Diagnosis

Comments

Transcription

Diagnosis
Helminths
•
The helminths can live in the humans for years,
decades
General symptoms
•
metabolic product of the helminth
- protein  allergisation  eozinophilia, urticaria,
asthma
•
food requirement of the helminths  food withdrawal
from the host  losing weight, anaemia
•
mechanical effect
- damage to the skin
•
specific organ symptoms during the migration of the
larva
- intestinal obstruction
- lymphatic vessels, blood vessels obstruction
•
carcinogenesis (schistosoma)
Diagnosis
• serology
• macroscopic examination
• microscopic examination 
• concentration methods:
- larva: larva migration test
- positive thermo-hydrotaxis of the larvas
- egg:
- flotation: specific weight of the media > egg
• specific weight (supernatant)
- sedimentation: specific weight of the media < egg
• specific weight (in the sediment)
- biopsy: - cysticercus in the muscle
Prevention
• washing hands
• washing vegetables, fruits
• avoid eating not sufficiently roasted, cooked meat … etc.
Therapy
- drugs usually inhibit one of the catalytic enzyme
system of the helmiths
- they usually have wide spectrum
- eg: Mebendazole, Praziquntel, Thiabendazole
Nemathelminthes - round worms
- separate - sexed
complete digestive system
Nematodes - thread worm
- resistant, non cellular cuticle
- spindle or whip shape
Platyhelminthes – flatworms
- hermaphroditic or separated sexed
uncomplete or lack of digestive system
Trematodes - fluke
- leaf-shaped
- cellular epithelium
- pair of suckers
Cestodes - tape worm
strobila (segments)  inside: complete male and
female reproduction system
- no mouth  absorption
Flat worms
• tapeworms maintain anchorage to the host small-gut
mucosa by means of the scolex
• a holdfast structure bearing a circlet of four suckers and
usually a central evertible rostellum with one or more
circlets of minute hooks
• the rest of the body forms the strobila and consists of a
chain of flattened proglottids,
• gravid proglottids are lost from the end of the worm and
are replaced by others that have matured as they pass
down the strobila
• each proglottid possesses a complete set of
hermaphroditic sex organs and marginal genital
openings
• eggs accumulate in the uterus of gravid proglottids and
only enter the faecal stream when the proglottids are
disrupted
• T. saginata: 12 m, T. solium: 6 m
• T. saginata scolex: is square, 1-2 mm in
diameter with 4 suckers
• T. solium scolex: has a rostellum with
hooklets
• symptoms include abdominal discomfort or
pain, abdominal distension, nausea,
diarrhoea, malaise, anxiety, anorexia
Taenia saginata - cattle
Taenia solium – pig
Taeniasis:
• world-wide distribution
• T. saginata is prevalent in regions where cattle are raised:
Africa, Middle-East, Central and South America, Europa and
Asia
• T. solium is prevalent in Central and South America
(expecially in Mexico), Africa, South-Est Asia, Eastern
Europe, Micronesia
Taeniasis:
• occurs when raw or undercooked unfrozen beef (T.saginata)
or pork (T.solium) are eaten
• in the muscle "cystisercus"  human infected by eating the
meat  small intestine larva maturation  mature worm 
egg filled segments break off  pass out with faeces  pork
or cattle  embryo  blood stream  muscle  cysticercus
• after ingestion by the intermediate host, eggs
hatch
• and the released hexacanth embryos bore
their way into the mucosa
• the larval stages of the parasite are generally
cystic with an invaginated embryonic scolex
(protoscolex)
• the cycle is completed when the larval stage,
within the intermediate host or its tissues, is
eaten by the definitive host
• the protoscolex evaginates and attaches to
the gut mucosa
Taenia saginata – beef tapeworm
• gravid proglottids are passed at defaecation, often
in short chains; free eggs also occur in faeces
• the whitish proglottids, approximately 2 to 3 cm
long, are actively motile, elongating and contracting
• viable eggs persist on pasture for many months and
can survive most forms of sewage treatment
• cattle have access to human faeces on farms, at
camp sites and recreation areas, and on railway
lines
• in cattle, cysticerci occur in striated muscle
• they are whitish, ovoid, and measure 8 by 5 mm
• they contain an invaginated protoscolex with no
hooks
• they become infective within 12 weeks and
remain viable in the living host for 2 years
• they are viable in stored, chilled meat for several
weeks but are killed at -20°C within 1 week
• the prepatent period in humans is 3 months and
worms may live 30 years
• cattle develop protective immunity to new
infection
Treatment: niclosamid, praziquantel
Echinococcus granulosus - dog
E. multilocularis fox - final host
• distribution with a higher prevalence in
South-America (Argentina, Uruguay),
Europe (mediterranean bassin), Northern
Africa, Middle East, South-Central and
East Asia
• intermediate host: cattle, pig, sheep
• accidental intermediate host: human
Disease: hydatidosis
• is caused by the larval stage of E. granulosus
• after ingestion of eggs the onchospheres penetrate the
intestinal mucosa and reach host organs (mainly liver
and lung)
• they encyst within a week reaching 1 cm in diameter in
about 5 months
• the cysts (2 to 30 cm) are constituted by an external
acellular cuticule and an inner cellular "germinal" layer
that produces the brood capsules containing 6-12
protoscolices or single protoscolices
• the larvae (scolices) develop from the germinal layer
• the mature protoscolices have 4 suckers and a rostellum
with hooklets and can be observed in the hydatid fluid
• spontaneous or surgical rupture of the cyst can originate
a secondary hydatidosis - - the liver is the most common
site of development of cysts (50-75%)
• pulmonary infection is observed in about 20-30% of
patients
• any other organ can be affected: nervous system, heart,
bones, spleen eyes, muscles are the most common sites
Diagnosis:
• the presence of isolated hooklets is diagnostic for
hydatidosis
• lesions can be detected by CT scan or echography
• ELISA, Western Blot
Treatment:
• is based on surgical and/or medical therapy
(albendazole)
Echinococcus multilocularis (E. multilocularis) The “small
fox tapeworm”
• prevalent in North America (Alaska and northern
Canada),
in Europe (France, Switzerland, Austria and Germany),
in Asia (from the White Sea to the Behring strait in the
north and from Turkey, through Afghanistan, Iran, India,
China, Mongolia to north Japan in the south)
• causes alveolar echinococcosis (AE) in intermediate
hosts
• red and arctic foxes, dogs and cats are the definitive
hosts - carnivores
• in the definitive hosts the adult tapeworm, consisting of 2
to 6 proglottids, lives attached to the luminal surface of
the small intestine
• it is assumed that the intermediate host acquires the
infections through the ingestion of contaminated fruits
and vegetables
• when the intermediate hosts (predominantly
rodents or other small mammals, or,
accidentally, humans) ingest eggs, the
onchosphere hatches from the egg in the
duodenum
• the activated oncosphere penetrates the small
intestine, enters blood vessels and reaches
primarily the liver via the portal vein
• in the liver the oncosphere proliferates into the
metacestode surrounded by an inner
germinative membrane and an outer laminated
layer
• the lifecycle is completed when an intermediate
host carrier of viable protoscolices within the
cysts, is devoured by a definite host
Disease
• the liver is the organ primarily affected
• metastases are mainly observed in cases of advanced
disease and may affect almost any organ
• the disease either spreads via direct contact or via blood
vessels
• secondary AE mostly affects the brain, the lungs, soft
tissue, the spine and other bony structures
• the disease is primarily characterized by an expansive
and infiltrative growth in the liver
• clinical features may be absent for many years and
mostly become apparent in advanced disease
• they may include hepatomegaly, jaundice, abdominal
pain, weight loss, fever and manifestations of
secondarily affected organs.
Diagnosis:
• computed tomography (CT) and magneticresonance-imaging (MRI) are used
• for serology ELISA
Treatment:
• The only curative treatment for AE is total
surgical resection combined with
chemotherapy
• benzimidazoles
Fasciola hepatica
• is found in rural areas of temperate and tropical regions, related to
cattle herding
• high prevalence is described in Europe and Latin America
• the adults live in biliary ducts for up to 10 years
• larva  excystation in the duodenum  larva through the gut wall
 liver  maturate worm  egg in the bile duct  pass out with
faeces  fresh water (miracidium)  snail  plants  human
• after excistation in the small intestine, metacercariae penetrate the
intestinal wall , cross the liver parenchima to the bile ducts
• eggs can be found in faeces 3-4 months after penetration
Diagnosis:
• the diagnosis is confirmed by the presence of eggs in faeces
serology is useful when the clinical picture is compatible and eggs
are not found
Nematodes
Entrobius vermicularis - pinworm
• "ab ano ad os"
• world-wide distribution with the highest prevalence in
temperate and cold climates and in crowded conditions
Life-cycle:
• larva leaves the egg in the duodenum  migration into
the colon  fertilization  gravid female goes down to
the anus and the embryonated ovum is deposited on
perianal skin (a few thousand/day)  itching 
scratching  autoinfection
Diagnosis:
• eggs are rarely found in faeces, they are more easily
found in the perianal region
• Scotch-tape smear can be used to pick up the eggs and
must be made in the morning before defecation and
bathing
Ascaris lumbricoides
• has a world-wide distribution and is most prevalent in
tropical areas
• 25% of the world population harbours the parasite
Life-cycle:
• geohelminth
• infect. with soil contam. egg  larva leaves the egg in
the duodenum  through the small intestine wall 
blood stream  lung  alveolus  bronchus  trachea
 pharynx  oesophagus small intestine sexually
mature worm gravid female release the egg  with
faeces in soil
• immature or adult A. lumbricoides are sometimes passed
in stools
• adult males are 15-20 cm, femals are 20-35 cm
Diagnosis:
• detection of eggs in faeces
Treatment:
• mebendazol, levamizol
Trichinella spiralis - pork meat
• eating cyst (encysted larva)  release of the larva  maturation 
copulation  gravid female under the mucous membrane of the the
small intestine  larva born  lymphatics, blood vessels 
encystation in muscle  infective for years
• the cyst is formed outside by a fibrous capsule and inside by an
eosinophil infiltration around the tightly coiled larvae
Disease: trichinellosis
• massive infection may cause acute enteritis
• myalgia, fever, periorbital oedema
• the migration and the later muscle encystation of larvae may be
asymptomatic or cause serious generalized disease with possible
miocardial and brain pathology
Diagnosis:
• is based on serology and
• on finding of larvae in the striated muscle biopsy
Treatment:
• tiabendazol