dfb pharmaceutical

English Edition No. 1-2009
EWOS integrated sea lice
programme - Feed as a tool
in the management of sea lice
1
EWOS integrated sea lice
programme - Feed as a tool
in the management of sea lice
Electron microscope
photos of sea lice.
(© Simon Wadsworth)
Spotlight is an occasional, international publication from EWOS to discuss, in some depth,
topical issues relating to fish feed.
EWOS is a leading and trusted supplier of aquafeed for the international aquaculture
industry. We produce fish feed in all four of the world’s major salmon farming regions:
Norway; Chile; Canada; and Scotland.
Find out more about EWOS and download resources at: www.ewos.com
2
English Edition No. 1-2009
e
Page
1. Summary
a. EWOS IN FEED ANTI SEA LICE PORTFOLIO
2. Background
3. Significance of sea lice
a. Economic impacts
b. Health and welfare
c. Possible vectors of contagious diseases
d. Environmental impacts
4. Sea lice biology
a. Sea lice species, life cycle and stage development
b. Reservoir
c. Biological spreading patterns
5. Sea lice control programs
a. Sea lice monitoring
6. Sea lice treatment
a. Treatments, mode of action and restrictions on use
i. Cleaner fish
ii. Pharmaceuticals
iii. Disease
b. Integrated pest management
c. Ideal salmon life cycle sea lice treatment scheme
d. Pharmaceuticals, use, misuse and resistance patterns
I. Norway
II. Chile
iIi. Ireland
IV. UK
v. Canada
vI. Faeroes
7. Strategies to avoid sea lice resistance development
8. Effective husbandry and treatment practice
9. Anti stress properties of dietary nucleotides, EWOS boost
a. Sea lice infestation and treatment stress
10. Anti sea lice properties of dietary nucleotide, EWOS boost
11. New EWOS anti sea lice drug and bioactive compounds
a. EWOS releeze® and EWOS Dfb medicated pellet
b. EWOS additional bioactive compounds
12. EWOS Integrated Sea Lice Program
13. List of references
4
4
4
4
4
5
5
6
8
8
10
10
10
10
12
13
13
13
14
14
13
15
15
16
16
16
16
17
17
18
19
19
20
20
20
21
22
23
3
Summary
Infestations with the marine copepods
Lepeophtheirus salmonis and Caligus
sp are difficult to avoid within netpen based salmonid production.
Consequently a core aim of EWOS is
to secure the access of in-feed anti-sea
lice drugs and supportive compounds
to the industry. The current launching
of an EWOS diflubenzuron-based oral
chitin synthesis inhibitor of sea lice
in Chile and Norway is a significant
contribution. With its existing product
Slice® (or its generic emamectin
equivalent), EWOS has two different
anti-sea lice medicated pellets in
the market. These veterinary drugs
together with EWOS additional
bioactive compounds form the
EWOS in-feed anti-sea lice portfolio.
Furthermore, it is the responsibility
of EWOS to present ideal rotating
treatment schemes of sea lice to the
industry, including bath treatments.
This will maintain a prolonged shelf
life of all compounds and prevent
the development of resistance.
Establishing an EWOS integrated sea
lice programme is a challenge both
for EWOS Innovation and the EWOS
operating companies. However, as
control of sea lice is an absolute
necessity to the entire salmon industry,
EWOS’s goal is to be a competent
partner and participant to help
ameliorate this issue in the future.
EWOS IN-FEED ANTI-SEA LICE PORTFOLIO
Prescription drugs
• EWOS slice® and EWOS emamectin generic
- Emamectinbenzoate, a sea lice neurotransmission inhibitor with 10 weeks prolonged efficacy against all species and stages of lice
species of lice: duration of effect
identical to duration of treatment;
14 days
Feed additives
• EWOS boost
- Nucleotide mix, anti stress and sea lice properties
Emerging products
Feed additives with anti sea lice
properties;
- Within EWOS Innovation research is being conducted on both naturally derived and pharmaceutical molecules for their efficacy against sea lice; either in combination or as a single substance
• EWOS releeze® and EWOS Dfb
- Diflubenzuron, a sea lice chitin synthesis inhibitor effective against moulting stages of all
Background
The sea lice issue within the salmon
aquaculture industry worldwide is a
serious, complex and dynamic issue
with a series of industrial, biological,
political, social and environmental
questions surrounding it. Control
of sea lice is critical to the future
sustainability of the salmon farming
industry. The significance of the sea
lice issue and its sub-issues varies from
region to region. EWOS, as a global
supplier to the salmon industry, is
fully involved in all aspects of the
topic to improve knowledge and assist
customers in challenging the problem
of sea lice infestation.
Significance
of sea lice
The general significance of the sea lice
challenge and its implications for the
sustainability of the salmon farming
industry can be subdivided into four
4
main areas;
- as a direct challenge to the economic sustainability of the industry
- as a direct threat to farmed salmon health and welfare
- as a possible vector of contagious diseases
- as an environmental challenge related to migrating wild salmon smolts and to the impact on benthic fauna beneath operations when anti-sea lice drugs are used.
Economic Impacts:
Johnson et al. (2004) reviewed the
economic impact of parasitic copepods
in marine aquaculture and concluded
that the average annual cost of sea lice
infestations in salmonid aquaculture
exceeds US$ 100 mill.
In Chile, it has been estimated for 2007
that Caligus rogercresseyi infestation
of salmon represented a total loss
of US$ 222 mill, which included
performance impacts and treatment
costs, which translate to 0.33 US$/kg of
salmon produced (Bustos, 2007).
The 2007 figure for Chilean sea licerelated costs is more than double
corresponding global costs of 2004.
However, in contrast to 2004 global
figures and the 2007 Chilean figures,
performance and downgrade costs
are less of an issue today, especially
in Ireland, the UK, Canada and
Norway due to mandatory treatments
triggered by low sea lice counts. In
the Norwegian salmon aquaculture
industry two main types of expenses
are related to sea lice; direct treatment
costs and losses due to an increased
FCR, calculated as 0.5% increase on
average FCR of total biomass produced
within one fiscal year. In 2007 Slice®
oral and pyrethroid bath treatment
costs were 86.5 mill and 33.7 mill NOK,
respectively. The estimated increased
FCR on total production equals a
value of 47 mill NOK, which gives a
total sea lice connected expenditure
in Norway in 2007 of 167.2 mill NOK
(US$ 23.5 mill). However, in contrast
the Norwegian sea lice related costs
are only 10% compared to the Chilean
equivalent.
English Edition No. 1-2009
For Canada the economic impact is solely
related to the cost of Slice® treatments.
In 2007, the cost of treatment in British
Columbia, Canada, was estimated at 3 mill
CAN dollar (US$ 2,8 mill).
Health and Welfare:
Sea lice infestations that are not properly
treated cause tremendous skin lesions,
disturbance of the osmotic balance,
secondary infections in wounds and
ultimately death of the fish. This was
considered the usual disease event in
infested fish in the early days of the
industry before the introduction of
effective pharmaceuticals.
Chilean aquaculture operations in certain
geographical areas have recently been
periodically fallowed because of the
reduced effect of drugs used, and the
subsequent reappearance of severe clinical
problems due to sea lice
The significant stress to salmon caused
by sea lice infestation, as well as the
treatments used (at increasing frequency
due to the improving resistance of sea lice
to previously effective pharmaceuticals)
highlights the obvious welfare implications
the industry faces. The establishment of
a sea lice control programme will act as
an important element within the context
of a larger aquaculture industry welfare
programme.
Possible vectors of contagious
disease
It is documented that sea lice might
harbour pathogenic bacteria and viruses,
like Aeromonas salmonicida (furunculosis),
Piscirickettsia salmonis (SRS), Infectious
Salmon Anaemia virus (ISAv) and Pancreas
Disease virus (PDv). Even intracellular
parasites, Microsporidia sp, which cause
disease in salmonid fish are transmitted
by sea lice, as shown in a recent paper
published by Nylund et al. (2009). The role
of sea lice as a vector for these agents
should not be underestimated, especially
in areas where the infectious pressure
of viruses is high and where skin and gill
lesions caused by sea lice are recorded
clinically. The question is if the lice act
merely as a passive mechanical vector of
viruses or also as a biological vector, ie
do viruses replicate within the lice? If so,
this would create a much more serious
scenario. Already Microsporidia sp have
been shown to propagate within the louse
(Nylund et al., 2009).
5
Enviromental Impacts
Sea lice have been the main political
issue for some time in Norway,
Scotland and Canada due to the
threat they are believed to create
to migrating wild salmon. There is
a strong assumption that a direct
relationship exists between sea lice
infestation of farmed stock and
infestation rate (and mortality due
to sea lice) on their wild counterparts
in such areas. This (unconfirmed)
negative relationship of farmed
salmon acting as a reservoir of lice that
infects wild stocks, espesially migrating
smolts resulted in the Norwegian
legislation for the control of sea lice;
6
mandatory delousing campaigns
within the industry. The protection
of wild salmon stocks is currently the
primary objective of sea lice legislation
in Norway.
In Canada a long lasting political
discussion is taking place on the
significance of sea lice infestation
levels encountered in cultured salmon
and the survival rates of migrating
wild pacific salmon stocks. Average sea
lice infestation rates are low within
Canadian West coast operations.
Consequently, there is no evidence
to suggest a connection between sea
lice numbers on farmed salmon and
a reduction of recurring wild salmon.
In spite of this, strong demands have
been raised towards the industry in
relation to the eradication of certain
wild pacific salmon smolts because of
sea lice. However, such claims should
be regarded within the scope of
domestic competing industries, such as
angling, general tourist activity, and
pacific salmon wild catch operations.
The main focus regarding possible
negative effects on anti-sea lice drugs
has historically been on chitin synthesis
inhibitors. Although bath anti-sea lice
English Edition No. 1-2009
treatments have an obvious direct,
but short-lived toxic effect on life in
the water column close to the treated
pen, focus has been on the effect of
chitin synthesis inhibitors due to the
possible impact on benthic fauna in
sediments beneath farms, especially
on animals with a chitin exoskeleton.
However, following a review by
the Norwegian Institute of Marine
Research (IMR) of the comprehensive
ecotoxicological documentation
package for the registration of the
various chitin synthesis inhibitors in
the market, it was concluded that the
use of these compounds is extensively
documented and those used are
considered environmentally safe.
Similarly, the environmental impact
of Slice® (emamectin) was deemed
safe following a lengthy study by the
Scottish Environmental Protection
Agency (SEPA).
In terms of food safety there have
been no issues related to the use of
sea lice drugs. For all compounds
used there is an established maximum
residue limit (mrl) according to
relevant EU legislation, based on
extensive metabolic and toxicological
data from the target animal, salmon.
Sea lice continue to hinder both
cultured and wild salmon in numerous
countries across the world. It is a very
real threat to the future aquaculture
production of the affected species.
With the development of effective
sea lice vaccines, and the breeding of
genetically resistant stock currently
distant goals, the industry must
adapt and fully utilise the currently
available options; good management,
treatment(s), and proposed control
programmes such as this.
7
Sea lice biology
A profound understanding of sea
lice biology, potential reservoirs,
life cycle, biological requirements,
epidemiology etc are required in
order to be able to establish effective
anti-sea lice strategic programmes. A
lot of scientific knowledge has been
compiled in recent years, but some
important data are still missing.
Sea lice species, life cycle
and stage development
Within salmon aquaculture, there
are basically two main variants of
sea lice, Lepeoptheirus salmonis
and Caligus sp. The first is a distinct
uniform species, whilst the latter is
a heterogeneous biological genus
covering a large group of species and
subspecies with individual distinct
features. The biology of these two
species or groups is different; the
Figure 1 Lepeophtheirus salmonis life cycle
8
8
main difference being the fact
that Lepeoptheirus salmonis is a
salmonid species specific parasite
and Caligus sp are not; they are a
parasite with no fish host species
preference. Although Caligus sp
are encountered in monitoring
programmes, Lepeoptheirus salmonis
represents the main sea lice challenge
in Norway, the UK and Canada. In
Chile, Caligus rogercresseyi is the sea
lice species of importance.
The life cycle of the two species
present within salmon aquaculture
are depicted in Figures 1 and 2. Since
preadult moulting stages are not
present in Caligus rogercresseyi, the
duration of the Caligus rogercresseyi
cycle itself is shorter compared to the
Lepeoptheirus salmonis equivalent
at equal water temperature. This
gives a narrower window for EWOS
diflubenzuron (chitin synthesis
inhibitor) treatment.
Further to the known sea lice species
in salmonid fish, marine fish have
their own specially adapted lice, like
Lepeophtheirus hippoglossi in halibut
(Hippoglossus hippoglossus) and
Caligus curtus in cod (Gadus morhua),
both with their own life cycle and
environmental and biological
requirements.
Since sea lice drugs have various
modes of action and are effective
towards different stages of sea lice,
knowledge on development patterns
among various lice are crucial. Stage
development and water temperature
in Lepeoptheirus salmonis is shown
in Figure 3. Water salinity is a further
factor influencing louse development
significantly.
English Edition No. 1-2009
Figure 3
Approximate development time for sea lice (L. salmonis) at various temperatures
Adult, female
17OC
Adult, male
10OC
Preadult 2, female
7OC
Preadult 2, male
Preadult
Chalimus 4
Chalimus 3
Chalimus 2
Chalimus 1
Copepodit
0
1 weeks
2 weeks 3 weeks
4 weeks 5 weeks 6 weeks
7 weeks 8 weeks 9 weeks 10 weeks
Approximate development phase from
Chalimus 3 until Adult, male stage at
10 C after 20 days
O
Figure 2 Caligus rogercresseyi life cycle
Male
Nauplius I
Nauplius II
Gravid female
Copepodid
Chalimus I
Adults (motile stage)
Chalimus II
Chalimus IV
Chalimus III
>
9
>
Reservoir
Lepeoptheirus salmonis, being a
species specific parasite, makes the
establishment and implementation
of parasite control programmes
feasible. This is because there is
basically an industrial control of the
parasite reservoir; farmed salmon.
Since farmed salmon in Norway, the
UK and Chile constitutes the major
part of the total salmon at sea,
such reservoir control is possible.
Unfortunately, farmed salmon
escapees represent an uncontrollable
reservoir of all types of sea lice.
The Canadian situation is different.
Here, large migrating salmon stocks
represent major parasite reservoirs or
at least an equal reservoir to that of
farmed stocks. The wild salmon louse
reservoir is uncontrollable and will
therefore have significant impacts
on established, or establishing
programmes within the Canadian
industry. The basic prerequisites
for establishing a sea lice control
programme in Canada is therefore
different compared to other regions
or countries.
The Chilean situation was previously
thought to share similarities with
the Canadian industry, where Caligus
rogercresseyi is a non-species specific
parasite with an uncontrollable
reservoir outside the salmon farming
operations, ie in wild marine fish.
However, investigations carried out
during the fallowing programme at
specific sites indicate that farmed
salmon seem to have emerged as
the major host and reservoir of
Caligus rogercresseyi. This is probably
due to the fact that abundant
numbers of salmon, present in high
densities per sea site, serve as a
convenient and permanent host to
the parasites, leaving the parasite
with no requirement to change host
for feeding or mating. This change
in host pattern among Caligus
rogercresseyi now means there is
a better basis (and reason) for the
establishment of an effective sea lice
control programme in Chile.
Biological spreading
patterns
A second biological feature of
importance is the spreading
patterns of sea lice between farms
and geographical locations and
also between fish within farms.
Lepeoptheirus salmonis spread
between sites via the planktonic
and parasitic infective stages,
nauplii and copepodites (Figure
1), which use oceanic and tidal
currents in order to shift location.
For a sea lice programme to work
effectively, knowledge on local and
regional hydrographic patterns
is therefore essential. Preadult
and adult Lepeoptheirus salmonis
move from host to host within and
between cages for feeding and
mating purposes, which serves as a
possible vector for the distribution of
contagious agents within sites.
Infectivity or spreading patterns
among Caligus sp is different to those
of Lepeoptheirus salmonis. In Caligus
sp both adult and larval challimus
stages are infective. Movement using
the marine current pathway allows
relocation between wild fish hosts
and caged salmon. Caligus sp will
remain on a salmon host over time
providing there is a plentiful supply
of food and energy, and the salmon
provides a suitable environment
for the reproductive stages of the
louse. Given suitable conditions, even
Caligus sp. will adapt and develop a
fish host preference.
Sea lice control
programs
A model sea lice programme consists
of regular sea lice monitoring and
rotational treatment schemes.
Such schemes include the use
of more compounds (biological
and pharmaceutical) that are
biosecured by correct treatment
and management practices, ie
coordination and the synchronisation
of treatments. It is also important
to test the treatment efficacy,
monitor drug use and conduct
bioassay surveillance (Figure 4). The
deployment of rotational schemes
is crucial for the control of drug
resistant sea lice.
Sea lice monitoring
The fundamental prerequisite of
any control programme for sea lice
within aquaculture operations, or
any treatment against sea lice, is
the establishment of monitoring
programmes giving information on:
- type or species of sea lice
- stages of the various lice
- infestation patterns, focal infestations or prolonged and ongoing chronic events
- water temperature and salinity
- any other disease or technical events which could influence infestation rates
Water salinity is a further significant
factor influencing louse development
10
10
Figure 4 Sealice treatments - biosecurity
English Edition No. 1-2009
Good treatment and
husbandry practices 3
Rotational treatment
schemes, 2
Drug biassay
surveillance 4
Pre- and post treatment
monitoring 1 + 5
EWOS has, for many years, developed
and issued sea lice monitoring
schemes for the industry. Within the
Norwegian official sea lice control
programme, such monitoring is
mandatory every fourteenth day
during the summer months. The
remainder of the year is monitored
monthly. Results have to be reported
to the responsible authority, and sea
lice levels are assessed on location by
the authorities. Sea lice counts above
fixed levels will trigger a mandatory
delousing action.
Date:
Site:
Cage.:
Monitoring scheme for Sea lice (L. Salmonis)
Accomplished
by: (sign.)
SEA LICE
Fish
no.
Non-mortile
Chamilus I-IV
Mortile
Preadult
I-II
Adult *
male
Adult female
Coligus sp.
with (+) / without (-) eggstrings
1
2
3
3
4
5
6
In the UK, the Code of Good
Practice for Scottish Finfish
Aquaculture recommends weekly
lice monitoring throughout the
year. The implementation of Area
Management Agreements is also
encouraged to coordinate strategic
treatments to keep lice levels at a
minimum.
7
8
9
10
11
12
13
14
15
16
17
18
‘19
20
Total:
Average:
Comments (Sea temp., weather conditions, other diseases).
>
© Copyright EWOS AS
EWOS SEA LICE SCHEME NO. 3 - 2009 ©
11
Table 1. Sea lice infestation levels triggering site treatment in different salmon farming areas
>
Country
Lice species
Infestation levels
Norway
Lepeoptheirus salmonis
• >0.5 adult female lice or >3 motile lice per fish independent of time
of the year
• >0.1 lice per fish any stage during mandatory delousing campaigns
in Western Norway, December 2008/January 2009
Faeroes
Lepeoptheirus salmonis
No fixed levels established
UK
Lepeoptheirus salmonis
Feb to June inclusive: 0.5 adult female lice per fish (recommended in
Code of Good Practice)
July to Jan inclusive: 1.0 adult female lice per fish (recommended in
Code of Good Practice)
Ireland
Lepeoptheirus salmonis
Spring: >0.3 to 0.5 egg bearing female lice per fish or high numbers
of motile lice
Other seasons: >2.0 egg bearing female lice per fish
Canada
Lepeoptheirus salmonis
British Columbia: >3 motile lice per fish during the whole year
New Brunswick: >2 adult lice per fish, whole year
Nova Scotia: no provincial threshold established
Chile
Caligus rogercresseyi
If >6 but <10 motile adults and gravid females per fish in the area
and ≥6 on site, treatment is organised by private company with
The second prerequisite within a functioning control programme will be the availability of anti-sea lice treatments;
biological means, anti-sea lice drugs and supportive natural components. For various reasons the availability of such
commodities differs within different regions (Table 2).
Sea lice treatment
The treatment of sea lice should be adapted to the epidemiology and life cycle of the sea lice present on site.
The listed range of treatments below is available for use with specified regional restrictions.
1) Biological treatment
- wrasse, cleaner fish
2) Pharmaceutical treatment
- Oral treatment
- emamectinbenzoate/Slice®
- chitin synthesis inhibitors,
EWOS releeze® and EWOS Dfb
- Bath treatments
- pyrethroids, AlfamaxTM, EXCISTM, BetamaxTM
- organophosphates, Salmosan®
- H202
3) Additive in-feed compounds
- nucleotides
- others; immune stimulants, anti-
sea lice settlement compounds
Table 2. Availability of anti sea-lice treatments in different salmon farming areas.
1) Biological treatment
- wrasse
2). Pharmaceutical
treatment;
- oral;
Canada
Chile
Not established
No biological
treatment available
Slice®
Generic
emamectinbenzoat
- emamectinbenzoat
- chitin synthesis
inhibitors
EWOS Dfb available
since early 2009
Norway
Established method
UK
Limited use
Slice®
Slice®
EWOS releeze®
available 2009
Launching of an EWOS
chitin synthesis inhibitor
pending
Calicide
Alphamax
(deltamethrin) and
Betamax (cypermethrin)
Excis (cypermethrin)
Salmosan
(asamethiphoz)
Salmosan (azamathifoz)
EWOS boost
EWOS boost
- bath
- pyrethroids
Alphamax
- organophosphates
H202
- H2O2
3. Additive in feed
components
12
12
- nucleotides
- others
EWOS boost
EWOS boost
Nucleotides, prebiotics
and immunostimulant
English Edition No. 1-2009
Mode of action and
restrictions on use
Factors influencing and restricting
the use of available treatments can
generally be listed as follows.
Cleaner fish
Biological treatment with wrasse is
dependant on the natural occurrence
of such fish in the various regions,
as well as their behaviour and
biology. The use of certain cleaner
fish species has been a success within
Norwegian aquaculture. Given the
right environmental conditions
certain operations in Southern
Norway completely manage their
sea louse situation by means of
a wrasse population within the
cages. However, this strategy is
difficult in Northern Norway due
to unfavourable conditions for the
wrasse species. The absence of such
fish in Canada and Chile makes a
similar approach unfeasible.
Pharmaceuticals
Pharmaceutical treatment of sea
lice is dependant on the mode of
action of the drug applied. The
most important feature to be aware
of is towards what stages of sea
lice the various compounds are
effective and for how long. Slice®
(emamectinbenzoate) is effective
against all stages of sea lice for
at least 10 weeks post-treatment,
hence its wide use in the industry.
In-feed diflubenzuron-based chitin
synthesis inhibitors are effective
against moulting stages of sea lice,
but not against adult stages, and
its effectiveness is limited to the
treatment period,14 days.
The bath treatment compounds
EXCIS and Betamax (cypermethrins)
and Alphamax (deltamethrin) are, in
general, effective against all stages,
but practically less effective against
larval stages. Such pyrethroid bath
treatments can leave as much as
20% of the lice population (mostly
challimus stages) untreated. These
survivors have displayed a delayed
development of upto five or six times
longer than normally developing
lice. This represents a prolonged and
sublevel stress on the fish. In addition,
bath treatments can have a direct
negative impact on host immunology,
leaving fish vulnerable to (re)
infection. Salmosan can be used as a
bath treatment with instant results,
but this compound is only effective
against adult stages, and most antisea lice drugs are ineffective against
adult female louse eggs. By knowing
the application restrictions of the
various compounds, there are some
obvious application combinations
which will give full effect, ie
combining adulticide compounds
with compounds effective against
larval stages, for example bath
treatments and oral chitin synthesis
inhibitors.
1 kg
TRANSFER
-Slice
Bath treatment
An ideal salmon life cycle sea lice
treatment scheme should include a
Slice® treatment of young fish (<1
kg) during their first exposure to sea
water followed by alternating bath
treatments and oral chitin synthesis
inhibitor treatments in larger fish
Diflubenzuron
Diflubenzuron
Diflubenzuron
until harvest. Slice® treatments can
also be used on larger fish as an
intermediate preventative measure
– is this what is meant by ‘breaks’.
Bath treatments should be applied
when adult lice are present followed
by oral chitin synthesis inhibitor oral
Bath treatment/Slice
Diflubenzuron
HARVEST
treatments when infestation reoccurs.
Depending of the stages of louse
present consecutive same compound
treatments, either oral or bath, could
be applied before changing the drug
used.
>
13
>
14
Disease
In a recently published paper
(Berg and Horsberg, 2008) a highly
significant influence of disease
outbreaks on emamectinbenzoate
concentrations in plasma of Slice®
treated fish is demonstrated,
giving reduced effect of such Slice®
treatments in diseased fish. Whether
this is due to general reduced feeding
or reduced uptake of nutrients and/
or pharmaceuticals in the intestine
has to be elucidated. However,
disease status of the fish seems to
be a crucial background factor in
the effectiveness of control and
treatment programs. Additional
to this reported patophysiological
impact of disease on uptake and
plasma levels of anti sea-lice drugs,
disease as such will have a direct
immunosuppressive effect on the host
fish triggering sea lice infestation
rates, a vicious circle is created.
Integrated pest
management
Integrated pest management is an
effective way to control and treat
parasite infestations. The core
of this approach is to have more
than one active pharmaceutical
available together with supportive
bioactive compounds, to use
each compound correctly and to
apply them in a planned rotating
manner through the production
cycle. Other important elements
within an integrated programme
will be regional, coordinated and
synchronised delousing campaigns,
control programmes for other
contagious diseases as well as regular
fallowing practices of sites. Using
this approach can avoid early and
epidemic resistance development of
drugs applied and prolong the shelf
life of compounds. This will give
the industry access to long lasting
and predictable methods for the
control of sea lice; the use of a single
pharmaceutical over time is regarded
as detrimental in this instance.
The access to various anti-sea lice
treatments and pharmaceuticals
in the EWOS regions differs due to
biological and legislative reasons.
There are substantial differences
between markets regarding the
existence of sea lice and the salmon
species farmed as well as local
variations in resistance patterns of
available drugs, meteorological and
hydrographical conditions and the
farming technology itself. Despite
these existing differences, the
establishment of a common approach
is possible and encouraged. The
prerequisites and approach will be
discussed in detail.
English Edition No. 1-2009
Pharmaceuticals; use, misuse and resistance patterns
Norway
The recent Norwegian history in
the use of anti-sea lice compounds
reveals facts about the expected
shelf life of compounds and
their correct use. From 1980 until
1995 the two organophosphates,
Neguvon (metrifonate) and Nuvan
(dichlorphos), were consistently
used as single substances in bath
treatments. Total domestic Neguvon
resistance was discovered in 1987, and
a similar pattern occurred for Nuvan
in 1995. Salmosan (azamethiphos),
a third class organophosphate for
bath application, was introduced the
same year (1995), but was replaced
in the market by the cypermethrins,
Excis and Betamax in 1997 and
1999, respectively, and Alphamax
(deltamethrin) in 1998, not because
of resistance but because of better
technical properties and effects of the
new pyrethriod class bath treatments
introduced. The compound,
Salmosan, is yet to show signs of
domestic resistance, and its technical
properties remain strong.
In 1999 in-feed anti-sea lice
treatments were marketed for
the first time, EWOS Lepsidon®
(diflubenzuron) and Skretting
Ectoban® (teflubenzuron); both
chitin synthesis inhibitors. These
products had a relatively short
time in the market, but not due to
resistance development. Instead
they were replaced by the broad
spectrum in-feed compound, Slice®
(emamectinbenzoate). The Slice®
medicated pellets were, and continue
to be, manufactured and marketed
by both of the larger fish feed
producers; EWOS and Skretting.
Since 2000 two main pharmaceutical
groups have been used within the
Norwegian market, bath pyrethroid
and oral emamectin treatments. Slice®
is used for younger fish whilst bath
treatments for larger growers. With a
few exceptions, this treatment model
has kept these drugs available and
effective to date. From 1998 to 2000,
before the introduction of in-feed
compounds, resistance was recorded
in certain areas for all the pyrethroids
because of extensive single drug use.
However, after restricting the use of
these pyrethroids and reintroducing
them after specific time periods,
the drugs reverted to full efficacy,
suggesting the sea lice which evolved
resistant genes did not survive.
During 2008, a multiple pyrethroid/
emamectin resistant area has been
identified in mid-Norway, together
with single farm emamectin resistant
areas on the South West coast. These
findings are all confirmed by the
use of targeted resistance assays, an
important tool in this context. In the
actual sites and areas where drug
resistance has been demonstrated,
alternative compounds such as
Salmosan and pyrethroids are being
used clinically, together with a larger
resistance screening programme.
The current situation has shown the
necessity of having more than one
compound available for treatment.
It is advisable to have three or
more available at any one time,
and to use them in a planned, and
well-managed rotating system of
treatments.
>
15
>
Faeroes
The Faeroes has a similar range of
pharmaceuticals to Norway (Table 2).
However, to date no specific resistance
patterns have been revealed.
Canada
In Canada only Slice® is licensed for anti-sea lice
treatments, and has so far been fully effective.
However, due to environmental concerns no
additional drugs are licensed by national or
provincial authorities. This may be a problem
in the future due to the potential hazards of
single compound use. In order to avoid the risk
of resistance and for environmental reasons, a
combination of licensed pharmaceuticals should
be available. Used in the correct manner, multiple
compounds should pose no/little threat to the
environment, and prevent the development of
resistant strains of sea lice.
Ireland has experienced a similar
development compared to that of Chile.
Single in-feed use of one class of active
compounds, iver- and emamectins for many
years has resulted in a domestic situation
of almost total resistance, certainly reduced
efficacy. Currently there is a ban on the
use of Slice® in Ireland, leaving pyrethroids
(Alphamax) and organophosphates
(Salmosan) in bath treatments the only viable
option.
16
16
Chile
The most important historic feature in Chile
is the single drug application of generic
emamectinbenzoate medicated pellets
since early 2000. This resulted in a complete
resistance towards the compound within
the Chilean industry by 2007. The problem
became so severe that fallowing sites in specific
areas, in order to reduce sea lice pressure by
removing the salmon host, became a common
occurrence in certain areas. This is in addition
to reports of up to 30% weight loss due to sea
lice infestation at some sites; a substantial loss
to the industry. Since 2007 pyrethroids, and to
some extent H202 bath treatments, have been
used in extensive sea lice delousing operations.
However, a single drug use pattern has once
again emerged with increasing resistance
to the treatment(s). The use of biological
resistance assays has now been introduced
within the Chilean industry
Ireland
UK
Slice®, pyrethroids and Salmosan are used
within the Scottish salmon industry. In
some areas, resistance against both Exis
and Slice® is reported. This is in addition
to a general lowered efficacy of Slice®
throughout the industry, which has
resulted in a reduced time interval between
treatments.
English Edition No. 1-2009
Strategies to avoid sea lice resistance development
The fundamental prerequisite to
avoid resistance development and
have effective drugs for long periods
is to have access to and to apply more
drug groups within an integrated sea
lice control programme. This should
be combined with biological tools
like cleaner fish if possible. Secondly,
treatments or single application
must be carried out correctly to
avoid suboptimal dosages, which
is the catalyst of drug resistance
development among lice. This is
specifically challenging regarding
bath treatments, where both existing
and emerging cage technology
as well as treatment practices are
unfavourable.
Classes of drugs, which by nature or
mode of action are only effective
against certain stages of lice, should
be strengthened by bioactive
compounds to make the applied
drug(s) more complete in their
action. This can be achieved in two
ways; by combining classes of drugs
in consecutive treatments; or, by
strengthening single drugs with
natural bioactive compounds which
have proven anti-sea lice effects. The
latter approach will be to include
natural bioactive molecules in the
recipes of anti-sea lice medicated
pellets and to feed fish awaiting bath
treatments with feeds containing
such extra bioactive compounds.
Industrial surveillance programmes
including the monitoring of
sea lice infestation before and
after treatments, as well as the
introduction of synchronised
resistance testing of lice towards
the various pharmaceuticals in use is
regarded as essential (figure 4).
17
Effective husbandry and treatment practices
Farmed salmon in regions with
clinical problems due to sea lice, ie
regions with substantial sea lice drug
resistance problems, require specific
husbandry practices and techniques
in order to maintain control. Regional
fallowing of all sites will be necessary
in severe cases, whilst geographical
extension of the region to fallow
and consecutive restocking policies
should be based on hydrographical
water current models or programmes
which give information on possible
spreading patterns of infective louse
copepodits and their epidemiological
area reservoirs, ie the position of
neighbouring salmon operations
which might harbour louse. Another
structural tool will be to switch to
the application of non-resistance
18
anti-sea lice drugs applied in a
concerted manner within voluntary
or mandatory delousing campaigns.
Such regional delousing programmes
should be implemented, irrelevant
to the resistance status of drugs, in
order to keep the sea lice infestation
pressure low.
In areas where certain drugs
remain effective, treatment
strategies should apply. The
importance of good medicine
management and the compliance to
recommended dosage regimes and
administration procedures cannot
be underestimated. Where oral
treatments are used, such as Slice®
or chitin synthesis inhibitors, the
population biomass estimate is of
paramount importance. Those using
bath treatments should consider the
following points for a correct and
successful treatment:
- control of water volume to treat, ie preferably the use of a cage closed tarpaulin or well boats
- oxygenation during treatment
- correct dosage (ml compound/m3) and treatment time
- trained personnel
In addition, it is considered essential
that regional, coordinated and
synchronised delousing campaigns
are established, which coincide
with control programmes for other
contagious diseases, and fallowing
practices implemented on site.
English Edition No. 1-2009
Products:
EWOS Oilmix; Proteinmix; OPAL; functional feeds; e-trace
Anti stress properties of dietary
nucleotides, EWOS boost
Sea lice infestation and treatment stress
micro
Stress is a medical term meaning
tissues, as seen during depletion
and exhaustion phases of stress
disruption of equilibrium or balance
events (Burrells 2001a,b, Leonardi,
of the normal physiology of the
organism (homeostasis) by various
2003). Infections and stress tax
and deplete the normal nucleotide
stressful stimuli; physical, perceptive
pool of the organism which can
or physiological.
not
be counterbalanced
by(EPI)
the ; Powerpack
Stress evolvesServices
from activation
EWOS(alarm)
growth index
(EGI);
EWOS pigment index
via resistance (depletion of reservoirs) organism’s normal de novo synthesis
or production via the salvage
to exhaustion (immune system
pathway of these nucleotides. In
collapse). To avoid stress is decisive
this situation the nucleotides are
within all aquaculture operations.
regarded conditionally essential,
meaning that they need to be
supplied orally in a purified form
A sea lice infestation represents a
for direct availability to the exposed
substantial stress to the infected
organism. The immunostimulatory,
animal. Furthermore, a sea lice
immunomodulatory and cell and
bath treatment is in its nature a
severe multi stress event including
tissue proliferative capacities of
dietary nucleotides are demonstrated
starvation, handling, crowding,
in a series of scientifically published
hypoxia and exposure to a toxic
trials (Peng Li, 2006).
pharmaceutical all within a short
period of time. Even a presumably
soft action like a Slice® pellet
For further information on EWOS
treatment has shown to trigger stress. boost, please refer to the more
detailed product brochure.
In a newly published scientific study
(Olsvik, 2008) it is reported that Slice®
aglonorse
opal120
treatment in prebiosal
salmon triggers the
expression of stress coding genes in
the fish due to sheer metabolisation
and degrading of emamectin in the
liver.
Dietary nucleotides as provided
boosterfeed
by EWOS boost
enhance the
function of the immune system, as
well as support the recovery and
regeneration of damaged cells and
boost
19
Anti sea lice properties of dietary
nucleotides, EWOS boost
Burrells et al. (2001c) demonstrated
the following effects by feeding
EWOS boost prior to, during, and
after primary sea lice infestation
events, sea lice bath treatments
(cypermethrin), and ultimately the
post-treatment reinfection, compared
to fish fed control feeds:
-
-
general primary infestation rate on affected fish were lowered by 25% (sea lice total counts, p<0,05)
effects of bath treatments were enhanced
- post treatment re-infestation rates were reduced by 30% (sea lice total counts, p<0,01)
These recorded anti-sea lice effects
are explained by a strengthening
of the innate immune defence
against attached lice. This optimised
treatment approach combining EWOS
boost feeding and bath treatment
enhances the total anti-sea lice effect
and reduces the risk of surviving
resistant lice.
EWOS Innovation in Colaco, Chile
(an experimental station) recorded
anti-sea lice effects by feeding EWOS
boost after bath treatments with
Alphamax. The results showed that
efficacy of anti-sea lice compounds
can be increased when combining
them with EWOS boost, obtaining an
additional average sea lice reduction
of 12% with a maximum effect in
adult stages (20% reduction) and
minimum effect in chalimus stages
(less than 7% reduction).
New class of EWOS medicated pellet against sea lice
EWOS releeze® and
EWOS Dfb
EWOS AS, Norway has recently
launched a new diflubezuron based
in-feed medicated pellet against
sea lice for prescription use only
EWOS releeze®. Diflubenzuron, the
active compound, is classified as a
chitin synthesis inhibitor. The drug
interferes with the exoskeleton
formation of the parasite and kills
it. This new medicine is therefore
effective against moulting stages
of lice (not adult stages),and is
effective throughout the duration
of the feeding period; 14 days. A
withdrawal period before slaughter
of 105 day degrees post treatment
is set by the Norwegian Medicinal
20
Authority, based on the mrl value
of diflubenzuron in salmon skin/
filet established within the EU. The
medicated pellet is an improved
version of a similar product previously
made by EWOS AS.
In Chile, a similar and parallel
licensing programme using a
diflubenzuron based EWOS
medicated pellet has been completed
with a pharmaceutical industrial
partner. EWOS Dfb, the Chilean
EWOS diflubenzuron medicated
pellets variant, has been available
since early 2009.
There are plans to introduce
EWOS diflubezuron based in-feed
medicated pellet within other
EWOS markets; Canada, the UK,
and Ireland. For the Scottish and
Irish markets, authorisation could
be granted based on the Norwegian
Marketing Authorisation via the
national pathway. However local
documentation adjustments and
amendments specifically related to
environmental issues for each country
must be addressed. A possible
Canadian registration of a similar
product will be an independent
process, but all necessary medicinal
and environmental documentation
is available via similar registrations
within other EWOS countries.
English Edition No. 1-2009
EWOS additional bioactive
compounds
EWOS boost is the model compound
within this category with its
combined anti-sea lice, anti-stress
and immunomodulating properties.
Any medicated pellet recipe and any
feed administered in conjunction
with bath treatments should contain
this additional natural component;
nucleotides. EWOS boost strengthens
the effects of anti-sea lice drugs,
minimises possible resistance
development against the drugs,
reduces stress-related damage and
generally improves the immune
system of fish.
EWOS Innovation is currently testing
several classes of naturally derived
compounds for their effectiveness in
this field, ie anti-sea lice effects as
single substances or in combination
with other drugs or bioactive
molecules. The compounds tested
include glucans, immune stimulants,
fatty acids and biological extracts,
their mode of action or classification
ranging from supporting compounds
to possible medicinal substances.
Some of these new compounds are
tested in Chile, both in vitro and in
vivo through feed trials.
21
EWOS integrated sea lice program
In this document EWOS present to
the industry relevant background
data and a complete tool box
necessary for the control of sea lice,
including available drugs, additive
feed compounds, and infrastructure
and service elements: The EWOS
Integrated Sea Lice Programme.
The rationale of the programme is
to provide the correct information
for the application of biological,
medicinal and nutritional means in
order to ease the sea lice problem
throughout the industry, worldwide,
whether through the use of wrasse,
bath and/or in-feed treatments,
making more in-feed drugs available,
creating a series of supporting
bioactive compounds, or supplying
the knowledge for controlling sea lice
using a compound rotational system.
The programme can be adjusted to
the various markets in relation to the
availability of medicinal compounds,
current resistance patterns of drugs
in use, environmental concerns, the
possibility of using cleaner fish, and
type of sea lice involved. Supporting
tools will be the development of
monitoring programmes for sea
lice and sea lice drug resistance,
as well as our contribution to
the implementation of delousing
campaigns within defined epidemic
areas.
Knowledge makes the
difference - in sea lice
management
22
English Edition No. 1-2009
List of references
Bailey, R.J.E., Birkett, M.A., Ingvarsdóttir, A., Mordue (Luntz),
A.J., Mordue, W., Pickett, J.A., Wadhams, L.J., (2004). The role of
semiochemicals in host location and non-host avoidance by salmon
louse (Lepeophtheirus salmonis) copepodids. Can. J. Fish. Aquat. Sci.
63, 448-456.
Berg A-G.T., Horsberg T.E. (2008). Plasma concentrations of emamectin
benzoate after SliceTM treatments of Atlantic salmon (Salmo salar L.):
Differences between fish, cages, sites and seasons. Aquaculture In press,
corrected proof.
Boxaspen K. (1997). Geographical and temporal variation in abundance
of salmon lice Lepeophtheirus salmonis on salmon Salmo salar. ICES
Journal of Marine Science. 54. 1144-1147.
Boxaspen K. (2006). A review of the biology and genetics of sea lice.
ICES Journal of Marine Science: Journal du Conseil 63 (7): 1304-1316.
Boxshall G. A. (1974). The population dynamics of Lepeophtheirus
pectoralis Muller: seasonal variation in abundance and age structure.
Parasitology. 69. 361-371.
Bravo S. (2003). Sea lice in Chilean salmon farms. European Association
of Fish Pathologists. 4. 197-200
Bravo S., Sevatdal S., Horsberg T.E. (2008). Sensitivity assessment of
Caligus rogercresseyi to emamectin benzoat in Chile. Aquaculture
Volume 282:7 -12.
Bron J. E., Sommerville C., Wootten R., Rae G. H. (1993). Fallowing of
marine Atlantic salmon Salmo salar L. farms as a method for the control
of sea lice Lepeophtheirus salmonis (Krøyer 1837). Journal of Fish
Diseases. 16. 487-493.
Bron, J.E., Sommerville, C. & Rae, G.H. (1993) Aspect of the behaviour of
copepodid larvae of the salmon louse Lepeoptheirus salmonis (Kroyer,
1837). En: Pathogens of Wild and farmed Fish: Sea lice.
Burrells, C. Williams, P., Southgate P., Wadsworth S. (2001a). Dietary
nucleotides: a novel supplement in fish feeds. 1. Effects on resistance to
disease in salmonids. Aquaculture 199, 159 – 169.
Burrells, C. Williams, P., Southgate P., Wadsworth S. (2001b). Dietary
nucleotides: a novel supplement in fish feeds. 2. Effects on vaccination,
salt water transfer, growth rates and physiology of Atlantic salmon
(Salmo salar L). Aquaculture. 199. 171-184.
Burrells, C. Williams, P., Southgate P., Wadsworth S. (2001c). the effects
of a nucleotide-enriched diet on experimental infestation with sea lice
(Lepeophtheirus salmonis) and on re-infestation rates following antilouse bath treatment with cypremetrin. SCI Conference, Aberdeen.
Bustos, P. (2007). Nuevos hallazgos sanitarios e incremento de la
infestacion por Caligus: una aproximacion epidemiologica a los actuales
problemas de mortalidad y crecimiento en mar. Novartis Seminar,
Puerto Varas, Chile. June 27, 2007.
Carvajal, J., L. González, M. George-Nacsimento. (1998). Native sea lice
(Copepoda :Caligidae) infestation of salmonids reared epten systems in
southern Chile. Aquaculture 166 :241-246.
Carvajal, J., L. González, M. George-Nacsimento. 1998. Native sea lice
(Copepoda :Caligidae) infestation of salmonids reared epten systems in
southern Chile. Aquaculture 166 :241-246.
Dawson, L. H. J., Pike, A. W., Houlihan, D. F. & McVicar, A. H. (1997).
Comparison of the susceptibility of sea trout (Salmo trutta L.) and
Atlantic salmon (Salmo salar L.) to sea lice (Lepeophtheirus salmonis
(Kroyer, 1837) infections. Ices Journal of Marine Science 54, 1129-1139.
Devine, G.J., Ingvarsdottir, A., Mordue, W., Pike, A.W., Pickett, J., Duce,
I., Mordue, A.J., (2000). Salmon lice, Lepeophtheirus salmonis, exhibit
specific chemotactic responses to semiochemicals originating from the
salmonid, Salmo salar. J. Chem. Ecol. 26, 1833-1847.
Fast M, Ross NW, Mustafa A, Sims DE , Johnson SC, Conboy GA,
Speare DJ, Johnson G, Burka JF. 2002. Susceptibility of rainbow
trout Oncorhynchus mykiss, Atlantic salmon Salmo salar and coho
salmon Oncorhynchus kisutch to experimental infection with sea lice
Lepeoptheirus. Dis Aquat Organ. 2002 Nov. 7; 52 (1):57-68.
Glover, K., F. Nilsen, O. Skaala, J. Taggart & A. Tealet (2001). Differences
in susceptibility to sea lice infection between a sea run and a freshwater
resident population of brown trout. Journal of Fish Biology (59):
1512-1519.
Gonzalez , G. ; Valladolid, M. 1998. Ecología de los salmónidos En:
Aspectos Biológicos, Anatomía microscópica y enfermedades Infecciosas
de los salmónidos. Madrid, España , Graficas Summa S.A, pp:299-321
González, L. & J. Carvajal (2003). Life cycle of Caligus rogercresseyi,
(Copepoda: Caligidae) parasite of chilean reared salmonids.
Aquaculture 220: 101-117.
González, L., Carvajal, J., George-Nascimento, M., (2000). Differential
infectivity of Caligus flexispina (Copepoda, Caligidae) in three farmed
salmonids in Chile. Aquac 183, 13-23.
González, L., Carvajal, J., Medina, A., (1997). Comparative susceptibility
of rainbow trout and coho salmon to ectoparasites of economic
importance. Arch. Med. Vet. 29, 127-132.
Grant A .N., Treasurer J. W. (1993). The effects of fallowing on caligid
infestations on farmed Atlantic salmon Salmo salar L. in Scotland. In:
Pathogens of Wild and Farmed Salmonids: Sea Lice (ed: G.A. Boxshall
and D. Defaye). Ellis Horwood. pp. 255-260.
Grøntvedt O. (1997). Oral delousing, the effect of teflubenzuron on the
shell of the salmon louse. Norsk Fiskeoppdrett NR. 7. 34-37.
Hart J. L., Thacker J. R. M., Braidwood J. C., Fraser N. R., Mathews J. E.
(1997). Novel cypermethrin formulation for the control of sea lice on
salmon (Salmo salar). Veterinary Record 140. 179-181.
Gustafson, L., S. Ellis, T. Robinson, F. Marenghi & Endris, R. (2006).
Efficacy of emamectin benzoate against sea lice infestations of Atlantic
salmon, Salmo salar L.: evaluation in the absence of an untreated
contemporary control. Journal of Fish Diseases. 29 (10): 621-627
Heuch P. A. (1995). Experimental evidence for aggregation of salmon
louse Lepeophtheirus salmonis in step salinity gradient. Journal of the
Marine Biological Association. UK. 75. 927-939.
Hevroy. E. M., K. Boxaspen, F. Oppedal, G. L. Taranger & J. C. Holm.
(2002). The effect of artificial light treatment and depht on the
infestation of the louse Lepeoptheirus salmonis on Atlantic salmon
(Salmo salar) culture.Aquaculture 62001:1-14.
Hodenland K., Nylund A., Nilsen F., Midttun B. (1993). The effect of
nuvan, azamethiphos and hydrogen peroxide on salmon lice. Bulletin of
the European Association of Fish Pathologists. 13. 203-206.
Hogans W. E. (1995). Infection dynamics of sea lice Lepeophtheirus
salmonis (Copepoda: Caligidae) parasitic on Atlantic salmon Salmo
salar cultured in marine waters of the Lower Bay of Fundy. Canadian
Technical Report of Fish and Aquatic Sciences. 2067. 1-10.
Hogans W. E., Trudeau D. J. (1989). Preliminary studies on the biology of
sea lice Caligus elongatus, Caligus curtus, and Lepeophtheirus salmonis
(Copepoda: Caligidae) parasitic on cage cultured salmonids in the Lower
Bay of Fundy. Canadian Technical Report of Fish and Aquatic Sciences.
1715. 14-19.
Horsberg T., Høy T. (1991). Tissue distribution of 14diflubenzuron in
Atlantic salmon Salmo salar. Acta Vetinaia Scandinavia. 32. 527-533
Høy T. (1991). Chemotherapy of sea lice infestations in salmonids:
pharmacological, toxicological, and therapeutic properties of
established and potential agents. Thesis submitted for the degree of
Doctor scientiarum. Norwegian College of Veterinary Medicine, Oslo.
Ingvarsdottir, A., Birkett, M.A., Duce, I., Genna, R.L., Mordue, W.,
Pickett, J.A., Wadhams, L.J., Mordue, A.J., (2002). Semiochemical
strategies for sea louse control: host location cues. Pest Manage. Sci.
58, 537-545.
Johnson, S.C. & L.J. Albright. 1991. Development, growth, and survival
of Lepeoptheirus salmonis (Copepoda:Caligidae) under laboratory
conditions. J. Mar. Biol. Assoc. U. K. 71:425:436
Johnson S., Albright L. (1992). Comparative susceptibility and
histopathology of the response of naive Atlantic, chinook and coho
Salmon to experimental infection with Lepeophtheirus salmonis
(Copepoda: Caligidae). Diseases of Aquatic Organisms 14, 179-193.
Johnson S., Blaylock R., Elphick J. & K. Hyatt. (1996). Disease induced
by the sea louse Lepeophtheirus salmonis (Copepoda:caligidae) in
wild sockeye salmon Oncorhynchus nerkastocks of Alberni Inlet,
British Columbia. Canadian Journal of Fisheries and Aquatic Sciences
53:2888-2897.
Johnson S., Margolis L (1993). Efficacy of invermectin for the control of
the salmon louse Lepeophtheirus salmonis on Atlantic salmon. Disease
of Aquatic Organisms. 17. 101-105.
Johnson S., Blaylock R., Elphick J. & K. Hyatt. (1996). Disease induced
by the sea louse Lepeophtheirus salmonis (Copepoda:caligidae) in
wild sockeye salmon Oncorhynchus nerkastocks of Alberni Inlet,
British Columbia. Canadian Journal of Fisheries and Aquatic Sciences
53:2888-2897.
Johnson S.C., Treasurer J.W., Bravo S., Nagasawa K., Kabata Z. (2004).
A review of the impact of parasitic copepods on marine aquaculture.
Zoological Studies 43:229-243
Lees F., Gettinby G., Revie C.W. (2008). Changes in epidemiological
patterns of sea lice infestation on farmed Atlantic salmon, Salmo salar
L., in Scotland between 1996 and 2006. Journal of Fish Diseases, 31 (4):
259-268
Leonardi M., Sandino A.M., Klempau A. (2003). Sffect of nucleotideenriched diet on the immune system, plasma cortisol levels and
resistance to infectious pancreatic necrosis (IPN) in juvenile rainbow
trout (Oncorhyncus mykiss).
Li P., Gatlin D.M. (2006). Nucleotide nutrition in fish: Current knowledge
and current applications. Aquaculture 251: 141 – 152.
Mackinnon, B. (1998). Host factors important in sea lice infectation. ICES
Journal of Marine Science 55:188-192.
Mustafa, A. & MacKinnon, B. M. (1999). Atlantic Salmon, Salmo salar L.,
and Arctic char, Salvelinus alpinus (L.): comparative correlation between
iodine-iodide supplementation, thyroid hormone levels, plasma cortisol
levels, and infection intensity with the sea louse Caligus elongatus.
Canadian Journal of Zoology 77, 1092-1101.
Nylund S., Nylund A., Watanabe K., Arnesen C.E., Karlsbakk E., (2009).
Nytt pathogen – gammel sykdom. Norsk Fiskeoppdrett 34: nr.2, 44 – 49.
Olsvik P.A., Lie K.K., Mykkeltvedt E., Samuelsen O.B., Petersen K.,
Stavrum A-K., Lunestad B.T. (2008). Pharmacinetics and transcripcional
effects of the anti sea lice drug ememectin benzoote in Atlantic salmon
(Salmo salar L.). BMC Pharmacology 8:16
Osorio, V. (2007). Tesis para optar al título de Biólogo Marino “Conducta
de apareamiento y reproducción de Caligus rogercresseyi sobre
Eleginops maclovinus”. Universidad de Los Lagos. 57 páginas.
Pike A. W., Mordue A. J., Ritchie G. (1993). The development of Caligus
elongatus Nordmann from hatching to copepodid in relation to
temperature. In: Pathogens of Wild and Farmed Salmonids: Sea Lice (ed:
G. A. Boxshall and D. Defaye). Ellis Horwood. pp. 50-60.
Pike, A. W. & Wadsworth S. L. (2000). Sealice on salmonids : Their
biology and control. En : Advances in Parasitology. Academic Press.
London. UK. Vol 44. pp 233-337.
Pino-Marambio, J.E., Mordue (Luntz), A.J., Birkett, M.A., Carvajal, J.,
Asencio, G., Mellado, A., Quiroz, A.E., (2007). Behavioural Studies
of Host, Non-Host and Mate Location by the Sea Louse, Caligus
rogercresseyi Boxshall & Bravo, 2000 (Copepoda: Caligidae). Aquac
271, 70-76.
populations on farmed Atlantic salmon, Salmo salar L., in Scotland
and its use in the assessment of treatment strategies. Journal of Fish
Diseases (28): 603-613.
Ritche G., Mordue A. J., Pike A. W., Rae G. H. (1993). The reproductive
output of Lepeophtheirus salmonis adult females in relation to seasonal
variability of temperature and photoperiod. In: Pathogens of wild and
farmed fish: sea lice (ed: G. A. Boxshall and D. Defaye). Ellis Horwood.
pp. 153-165.
Roth M., Richards R. H. (1992). Trials on the efficacy of azamethiphos
and its safety to salmon for the control of sea lice. In : Chemotherapy in
Aquaculture : From Theory to Reality (ed: C. Michel & D. J. Alderman).
Office International des Epizooties. Paris. pp. 212-218.
Roth M., Richards R. H., Sommerville C. (1993). Current practices in the
chemotherapeutic control of sea lice infestations in aquaculture: a
review. Journal of Fish Biology. 16. 1-26.
Roth, M., Richards, R.H & Sommerville, C. (1993). Currents practices in
the chemotherapeutic control of Sea lice infestations in Aquaculture- a
Review. Journal of fish Diseases 16:1-26.
Sevatdal, S., A. Magnusson, K. Ingebrigtsen, R. Haldorsen, T.E. Horsberg.
(2005). Distribution of emamectin benzoote in Atlantic salmon (Salmo
salar L.). (2005). J. vet. Pharmacol. Therap. 28: 101-107
Stone J., Sutherland L., Sommerville C., Richards R., Varma K. (2000).
Field trials to evaluate the efficacy of emamectin benzoate as an oral
treatment of Lepeophtheirus salmonis infections in Atlantic salmon
Salmo salar. Journal of Fish Diseases. 22. 261-270.
Thomassen J. M. (1993). Hydrogen peroxide as a delousing agent for
Atlantic salmon. In: Pathogens of wild and farmed fish : sea lice (ed: G.
A. Boxshall and D. Defaye). Ellis Horwood. pp. 290-295.
Treasurer J. W., Wadsworth S. & A. Grant (2000). Resistance of sea
lice Lepeophtheirus salmonis (Krøyer, 1837) to hydrogen peroxide on
farmed Atlantic salmon (Salmo salar L.). Aquaculture Research (31):
855-860.
Treasurer J. W., Wadsworth S., Grant A. (2000). Resistance of sea lice
Lepeophtheirus salmonis (Krøyer, 1837) to hydrogen peroxide on
farmed Atlantic salmon (Salmo salar L.). Aquaculture Research. 31.
855-860.
Treasurer J., Wadsworth S. (2004). Interspecific comparison of
experimental and natural routes of Lepeophtheirus salmonis and
Caligus elongatus challenge and consequences for distribution of
chalimus on salmonids and therapeutant screening. Aquaculture
Research. 35. 773-783.
Treasurer, J. W., S. Wadsworth, and A. Grant. 2000. Resistance of sea
lice, Lepeoptheirus salmonis (Kroyer), to hidrogen peroxide to farmed
Atlantic salmon, Salmo salar L. Aquacult. Res. 31:855-860.
Tucker C. (1998). Biological and environmental parameters influencing
the settlement and post settlement survival of Lepeophtheirus salmonis.
PhD thesis. University of Stirling. 1998.
Tully O. (1989). The succession of generations and growth of the caligid
copepods Caligus elongatus and Lepeophtheirus salmonis parasitising
farmed Atlantic salmon Salmo salar L. Journal of the Marine Biological
Association. UK. 69. 279-287.
Tully O. (1992). Predicting infestation parameters and impacts of
caligid copepods in wild and cultured fish populations. Invertebrate
Reproduction and Development. 22. 91-102.
Tully O., Whelan K. F. (1993) The production of nauplii of
Lepeophtheirus salmonis (Copepoda: Caligidae) from farmed and wild
salmon and its relation to the infestation of wild sea trout (Salmo trutta
L.) off the west coast of Ireland in 1991. Fisheries research. 17. 187-200.
Wadsworth S. L. (1998). Control of sea lice Lepeophtheirus salmonis
(Krøyer, 1837) on Atlantic salmon (Salmo salar L.) production sites. PhD
thesis. University of Aberdeen.
Wadsworth, S., Treasurer, J.W. and Grant, A.N. (1999) Efficacy of cocoordinated, winter treatments of farmed Atlantic salmon infested with
sea lice. Proceedings: 4th International Conference on Sea Lice, Dublin.
June, 1999.
Wallace C. (1998). Possible causes of salmon lice Lepeophtheirus
salmonis (Krøyer, 1837) infections on farmed Atlantic salmon
Salmo salar L., in a western Norwegian fjord-situated fish farm;
implementation for the design of regional management strategies.
Scientiarum thesis. University of Bergen.
Westcott J.D., Stryhn H., Burka J.F., Hammell K.L. (2008) Optimization
and field use of a bioassay to monitor sea lice Lepeophtheirus salmonis
sensitivity to emamectin benzoate. Disases of Aquatic Organisms, 79
(12): 119 - 131
White H. C. (1940). Sea Lice (Lepeophtheirus) and death of salmon.
Journal of the Fisheries Research Board of Canada. 5. 172-175.
White H. C. (1942). Life History of Lepeophtheirus salmonis. Journal of
the Fisheries Research Board of Canada. 6. 24-29.
Wooten, R., J.W. Smith, & E.A. Needham. (1982). Aspect of the biology
of the parasitic copepods Lepeoptheirus salmonis and Caligus elongatus
on farmed salmonids, and treatment. Proc. Roy. Soc. Edin. 81B: 185-197.
Wootten R. (1985). Experience of sea lice infestations in Scottish salmon
farms. ICES, Mariculture Committee. CM1985/F:7/Ref:M4.
Wootten R., Smith J. W., Needham E. A. (1982). Aspects of the biology
of the parasitic copepods Lepeophtheirus salmonis and Caligus
elongatus on farmed salmonids and their treatments. Proceedings of
the Royal Society of Edinburgh.
Quiroz A. (2006). Ecological control of Caligus rogercresseyi.
Symposium. Puerto Montt. November 2006.
Rae G. H. (1979). On the trail of the sea louse. Fish Farmer. 2. 22-23.
Revie C., Gettinby G., Treasurer J., Rae G. (2002). The epidemiology of
sea lice Caligus elongatus in marine aquaculture of Atlantic salmon
Salmo salar in Scotland. Journal of Fish Diseases. 25. 391-399.
Revie, C., C. Robbins, G. Gettinby, L. Kelly & J. Treasurer (2005). A
mathematical model of the growth of sea lice, Lepeophtheirus salmonis,
23
EWOS releeze®
and EWOS Dfb
Simon Wadsworth, PhD, EWOS Innovation
Jose Vecino; PhD, EWOS innovation
Javier Gonzales, DVM, PhD, EWOS Innovation
Jose Trioncoso, Marine biologist, EWOS Innovation
Ian Carr, MBA, EWOS Group
www.ewos.com
artgarden
Egil Myhr, DVM, PhD, EWOS Group
design
- Vet. 0,6g/kg, medicated pellet