Parasitic Mites of Dogs and Cats
Transcription
Parasitic Mites of Dogs and Cats
~......OMPENDIUM A REPRINT FROM ...........NTlNUING UCATION . .', .'. "~OR SPECIAL FOCUS ON THE PRACTICING VETERINARIAN PARASITOLOGY Continuing Education Article #5 .. :; Vol. 13; .No, ~. M~y 19,.91 783 Parasitic Mites of Dogs and Cats KEY FACTS • In dogs and cats, parasitic mites can cause Irritation and annoyance, may Induce localized Infection, and can be debilitating or fatal. • Mites lack natural enemies and can be resistant parasiticIdes; some species can lower host Immunity. • Some mite Infestations are easily eliminated from the animal and environment. Others are difficult or Impossible to eradicate. . • Prompt diagnosis of mite Infestation and Identification of the mite species as well as appropriate treatment are requisite to eliminate the parasite, to Institute any ancillary treatment, a.nd to advise the owners regarding contagion of the parasite or any possible predisposing genetic factors of the host. • In some cases, extralabel therapy with such agents as amltraz, ronnel, or Ivermectln Is the most effective treatment. Owners must give Informed consent before the extralabel treatment Is Initiated. to Upper Keys Veterinary Clinic Islamorada. Florida Robert H. Foley, DVM RRASITIC MITES ace membe" of the class Machnida, order Arachina (see the listing on Mite Taxonomy). Mites have a four-stage life cycle: egg, six-legged larva, eight-legged nymph, and eight-legged adult. Except for chiggers (Trombiculidae), of which only the larval stage is parasitic, mites of all four stages are parasitic. The three suborders of mites in the order Arachina consist of animals of diverse sizes, shapes, and distinguishing characteristics (Table I). The host anatomic areas preferred by various mite species differ (Table II) as do the geographic distribution (Table. III) and potential for contagion .' to .other animals and to h'umans 1.2 (Table IV). Because the j. "':":_c~inical significance and management of mite infestation .: ~;~.:~u,epend on the mite species, this article discusses each of 'the commonly encountered mites separately. the litter. Susceptible young dogs reportedly can contract Demodex canis mites by direct and close contact with a heavily parasitized carrier. 18 The presence of Demodex canis mites is considered to be a disease state when excessive numbers of mites of all four stages of the life cycle are present in a skin scraping from an animal with clinical signs. 19 Demodicosis is also termed follicular, red, pulJPY, squamous, pilosebaceous, or Acarus mange. Demodex mites reproduce and lay eggs in the hair follicle and associated sebaceous and apocrine sweat glands. The mites puncture cells and ingest the cell contents; this feeding activity produces keratinization that plugs and distends the follicle. Proliferation of the mites, with subsequent rupture of the hair follicle, allows the parasites to enter the bloodstream, lymphatics, lymph nodes, J.;. and various body organs. Inflammation and foreign body DEMODEX SPECIES ' '., response also occur. 20 Clinical Manifestations in Dogs Demodicosis occurs in three clinical forms: localized deA small population of Demodex canis mites is a normal modicosis, generalized Uuvenile or adult) demodicosis, finding on or in the skin of healthy dogs. The elongated and chronic pododermatitis. The localized form is the most mite (Table I) lives its entire 20- to 35-day life cycle in the common and usually involves the face, skull, ear canal, hair follicle, leaving only to cross to another hair follicle2 . 16 forelegs, or trunk. Affected dogs may have alopecia, vary(Figure 1). The mites are transmitted to puppies by contact ing degrees of scaling, hyperpigmentation, minimal pruriwith the dam during the first two to three days of life. 17 tus, erythema, and bacterial infection. The mites may Mites can also be transmitted from one pup to another in elude discovery. Multiple scrapings from squeezed hair Copyright © 1991, Veterinary Learning Systems Co., Inc. All Rights Reserved. Printed in USA 784 The Compendium • Small Animal Mite Taxonomy (Order Acarina)1 Class Arachnida: Head, thorax, and abdomen are fused. Mouthparts in capitulum; antennae and mandibles missing. Six-legged larvae, eight-legged nymph and adult stages. Order Arachina Suborder Prostigmata Family Demodicidae Demodex canis Demodex cati Unnamed Demodex species Family Cheyletiellidae Cheyletiella yasguri Cheyletiella blakei Family Trombiculidae Walchia americana Trombicula alfreduggesi Trombicula autumnalis Suborder Astigma: Respiratory pores absent; respiration occurs through integument Family Sarcoptidae Sarcoptes scabiei var. canis Notoedres cati Family Psoroptidae Otodectes cynotis Subfamily Listrophoroidea Lynxacarus radovskyi Suborder Mesostigmata: Respiratory pores on mid body Family Halarachnidae Pneumonyssoides caninum Family Dermanyssidae Dermanyssus gallinae Suborder Metastigmata: Ticks follicles on the margin of lesions may be needed. Skin scraping suffices to diagnose localized or generalized demodicosis; whereas in cases of pododermatitis, skin biopsy sometimes is necessary to establish a diagnosis. Localized demodicosis is most common in intact purebred dogs (76 %) younger than one year of age. 18 Ninety percent of cases of localized mange resolve spontaneously in four to eight weeks. Underlying transient stresses (e.g., adolescence, estrus, endoparasites, growth, nutrition, vaccination, surgery, and pregnancy) have been incriminated and may contribute to the disease. Sex, haircoat length, sebaceous gland size, and hypothyroidism do not appear to be factors in the development of localized demodicosis.'8.19.21 Ten percent of dogs with the localized form deteriorate to generalized juvenile demodicosis. The generalized form in- volves large areas of the body and causes alopecia (in more than 10 areas), erythema, and varying degrees of crusting, follicular plugging, and hemorrhage. A rancid seborrheic odor, folliculitis, furunculosis, cellulitis, deep pyoderma, pruritus, and peripheral lymphadenopathy often accompany generalized juvenile demodicosis. The condition can also occur without major associated reactions2.'7-'9.22 (Figure 2). In one study of 821 dogs with generalized juvenile mange, 87 % of the cases occurred in animals older than seven months of age; most of the subjects were intact purebreds (80%). Age and familial predisposition were the most important factors. 18 Two mechanisms have been proposed to explain the inherited immunologic predisposition to generalized juvenile demodicosis. The first explanation is that a genetic immune abnormality allows massive mite proliferation. The heavy mite population induces a humoral substance (B-cell stimulation) that in turn suppresses cell-mediated (T-cell) immunity. Treatment is directed at elimination of the mites to restore T-cell function. 23 -25 The second proposed mechanism is that genetic predisposition to pyoderma complicates the generalized juvenile demodicosis and suppresses lymphocyte blastogenesis (B and T cells). The pyoderma suppresses serum lymphocyte immunoregulatory factors in proportion to the degree of infection. Therapy would therefore be directed at the skin infection. 22 Immunosuppressive agents, such as corticosteroids, should not be used in animals with generalized juvenile demodicosis. Because of the inherited predisposition to the condition, the American Academy of Veterinary Dermatology recommends that dogs with generalized demodicosis should be sterilized.26 Demodectic pododermatitis tends to be a chronic digital and interdigital disease often complicated by pyoderma. Certain breeds are at increased risk (see the listing on Canine Breeds Predisposed to Demodicosis). Biopsy may be necessary to reveal the mites. In many cases, the condition is never cured. 2.27 Adult-onset demodicosis may not be hereditary. Most cases are secondary to iatrogenic Cushing's syndrome, atopy, immune deficiencies, diabetes mellitus, heartworms, malignancies, use of immunosuppressive agents, or deep pyoderma. Patients with the adult-onset disorder must be thoroughly examined and checked for other parasites and disease processes. A complete blood count, blood profile, and endocrine screening should be performed to identify any inciting factors needing treatment. Scottish terriers and West Highland white terriers seem particularly prone to adult-onset demodicosis complicated with atopy and deep pyoderma (Figure 3). Adult-onset generalized demodicosis can necessitate euthanasia. 2.27-29 Treatment of Canine Demodicosis Therapy for canine demodicosis depends on its form and complications. Localized demodicosis has a good prognosis; 90% of cases remit spontaneously within four to eight The Compendium • Small Animal 785 weeks without treatment. If the patient's owner insists on some form of intervention, topical 1% rotenone or follicular flushing products with benzoyl peroxide may be applied. 18 F;R THE 10% of locali"'l cases 'hat del"io"'e to generalized demodicosis, the prognosis is less optimistic and individualized therapy is indicated. From 30% to 50% of generalized juvenile demodicosis cases resolve spontaneously. Acaricidal therapy may not be necessary immediately; the clinician should monitor the patient's progress closely. Skin scrapings performed at two- to four-week intervals indicate when increasing mite population and predominance of immature forms dictate more-aggressive treatment. Review of the animal's pedigree could reveal the likelihood of spontaneous remission.2.17-19 Treatment of generalized demodicosis (juvenile and adult-onset) should be directed at simultaneous elimination of mites and any underlying pyoderma. Currently, amitraz is the only agent approved for use as a Demodex miticide in the United States. The manufacturer advises that 10.6 ml be diluted in two gallons of water (250 ppm = 0.025 %) and applied every two weeks to the dog's dry haircoal. Gloves must be worn during application of amitraz. Before amitraz application, the haircoat should be shaved and cleansed with a follicular flushing shampoo or a therapeutic shampoo (e.g., with povidone-iodine or chlorhexidine). Areas of deep pyoderma and furuncles should be avoided during dipping to minimize toxicity associated with amitraz absorbance. 27 Extralabel use of amitraz dramatically improves cure rates; an animal is considered cured if skin scrapings are negative and the animal lacks clinical signs six months after the last treatment. One study24 found that when 0.03 % amitraz (6 ml of 19.9 % amitraz in two gallons of water) was applied weekly rather than every two weeks, the cure rate for generalized demodicosis can rise from 20% to 75 %. Halving the diluent (6 ml amitraz in 1 gallon of water) to double the dose to 0.06 % can raise the cure rate up to 80 % with minimal toxicity. Amitraz toxicity is manifested as increased sleepiness, depression, and anorexia during the first 24 hours after treatment. More-extreme signs of toxicity, such as ataxia, polyuria, polydipsia, hypothermia, seizures, pruritus, erythema, hyperglycemia, and glucose intolerance, may occur. 30.31 Death is highly unlikely.30 If a doubled dose of amitraz is administered weekly, hyperglycemic and insulin-suppressing effects require special caution for diabetic animals. 31 Humans with diabetes must wear gloves when applying amitraz. Weekly administration of 0.05% amitraz seems most efficacious; but pet owners must be advised that this regimen is extralabel. 30 In France, amitraz concentrations of 0.05% and 0.10% have reportedly been effective and produced no toxic side effects. 32 Also in France, an amitraz-impregnated collar is marketed for Demodex and tick control,32 Treatment failures may be related to premature cessation of treatment or failure to correct underlying stress or infection. Months of weekly dipping may be needed to effect a cure; there is no prescribed number of dips. Extralabel use of ronnel can be tried to treat generalized juvenile demodicosis if amitraz fails. Ronnel is mixed as a 4% solution with propylene glycol (Scott's formula).24 The agent can be dispensed in a 4-ounce childproof amber medicine bottle containing 18 ml of 33.3 % ronnel solution plus 100 ml of propylene glycol. The preparation is stable for about one month. One third of the dog's body is painted daily so that each area is treated once every three days in sequence. Ronnel is effective in 90% of cases but is irritating to the skin and highly toxic to animals and humans. 19 Dogs to be treated with ronnel (or any organophosphate) should be free of heartworm infection before treatment is initiated. Demodex canis is resistant to ectoparasiticides less potent than ronnel. D EMODECTIC pododennalitis can he "eated with weekly immersion in double-strength amitraz (0.05%) or 4 % topical ronnel. Fresh daily amitraz can be applied (l ml of 19.9% amitraz per 30 ml of propylene glycol); however, oxidation makes this topical preparation unstable. Aqueous trichlorfon (3 %) solutions may be used as a topical therapy but are less effective than ronneP9; this use of trichlorfon is also extralabel. For all miticidal therapies, skin scrapings must be monitored at two- to four-week intervals. Counts or estimates of the numbers of live and dead mites should be made and therapy continued for three to four weeks after scrapings are negative. Recurrence is possible, and lifelong amitraz dips may be necessary. 28.33 Concurrent pyoderma must be treated simultaneously. Skin culture and sensitivity studies are indicated in complicated cases of demodicosis. Coagulase-positive staphylococci are the most common isolate, but Proteus or Pseudomonas organisms may be present. Pseudomonas seriously changes the prognosis because it can cause fatal septicemia. 18 An antibiotic, such as erythromycin, lincomycin, oxacillin sodium, cephalosporin, or chloramphenicol, may be used until the culture and sensitivity report returns. Antibiotics should be continued weeks beyond healing. 25 Clients should be advised of the zoonotic potential of the pet's infected skin. Vitamin E (up to 400 U orally twice a day) and fatty acid supplements may quell skin inflammation in dogs with generalized demodicosis and are useful for treating any underlying atopy. 33 Immune stimulants, such as levamisole or injectable bacterins, have not been successful against mites 786 The Compendium. Small Animal TABLE I Size and Identifying Characteristics of Parasitic Mites of Dogs and Cats2-6 Mite Size of Adult Female (lAm) Characteristics Demodex canis 40 x 225 Spindle-shaped eggs; elongated body, striations Demodex cati 30 x 200 Oval eggs; smaller and slimmer body than Demodex canis Unnamed Demodex species 30 x 110 Short, blunt abdomen; superficial skin parasite Cheyletiella yasguri 265 x 500 Cone-shaped sensory organ Cheyletiella blakei 265 x 500 Huge mouthhooks, heart-shaped sensory organ; surface mite Trombiculidae (chiggers) 210 x 400 Sarcoptes scabiei var. canis 250 x 400 Terminal anus; long, unsegmented pedicel Notoedres cati 200 x 240 Dorsal anus, body striations Otodectes cynotis 300 x 400 Long legs, short pedicel; males have pretarse on all four pairs of legs; surface mite Lynxacarus radovskyi 250 x 515 Hair-clasping sternal plates, elongated body; surface mite Pneumonyssoides caninum 150 x 400 Long legs, small palps; often confused with Dermanyssus mites Dermanyssus gallinae 150 x 400 Long legs, stocky palps; deeply embedded, red poultry mites; surface mites but may aid pyodenna therapy. 23.28 The extralabel use of ivennectin has produced disappointing results against Demodex mites, although it is highly effective against other mites. 34 ,35 Ivennectin paralyzes susceptible mites by potentiating the neuroinhibitor v-aminobutyric acid (GABA), thus blocking postsynaptic neuromuscular potentials, and is lethal to the parasite. Ivennectin does not cross mammalian blood-brain barriers to reach the GABA receptors. 35 Ivennectin can cause potentially fatal idiosyncratic reactions in collies, sheepdogs, and related crossbreeds and should not be used in these animals. 36 . 37 Dogs should be screened for heartwonn infection before receiving ivennectin therapy; the precise weight of all animals, dogs or cats, should be measured to detennine the correct dose. A 1% preparation of ivennectin provides 10 mg/ml (10,000 Ilg/ml). In one study, two 400-llg/kg injections of ivennectin given two weeks apart were effective against Demodex canis. 38 Another trial of the same dose at weekly intervals did not resolve the infestation but seemed to pro- . Orange-red, six-legged parasitic larva; hairy body; surface mite vide some reduction of clinical signs. 34 The efficacy of milbemycin oxime against Demodex canis is under study. Clinical Manifestations in Cats Feline demodicosis is caused by the follicular mite Demodex catil. 2 •9 (Figure 4) and a much less common unnamed Demodex species, which is found only in the stratum corneum of the cat's skin. 39 •4O The size and shapes of these mites differ from those of Demodex canis 3 (Table I). Both species are rare. Feline demodicosis manifests itself in two fonns. The localized fonn exhibits erythematous patches of alopecia along with scaling and crusting of the eyelids, face, chin, or neck (Figure 4). Ceruminous otitis may be seen. Multiple skin scrapings disclose the parasite. Spontaneous remission can occur. Generalized feline demodicosis is usually associated with an underlying disease (e.g., diabetes mellitus, hyperadrenocorticism, endocrine alopecia, feline leukemia virus infection, feline immunodeficiency virus, or an autoimmune disease).41-44 Generalized feline demodicosis may be more common in 788 The Compendium • Small Animal Figure 1A Figure 18 Figure 1-(A) Characteristic Demodex canis mite measuring 40 /-1m x 225 /-1m. (x60) (8) Demodex canis egg. (x60) CHEYLETIELLA SPECIES Clinical Manifestations Figure 2-A 10-month-old female akita with generalized juvenile demodicosis. Pyoderma was minimal relative to the extent of Demodex canis lesions. Burmese and Siamese cats than in other feline breeds. 2.39 Extensive lesions of erythema, alopecia, crusting, and hyperpigmentation can involve the head, neck, legs, and trunk. Eosinophilia and pyoderma may occur. Intense pruritus can occur with infestations of the unnamed Demodex species. 3 Treatment of Feline Demodicosis The prognosis for treatment of feline demodicosis is good. Treatments include 2.5% lime-sulfur dips, carbaryl shampoos, and malathion dips.2.42 Carbamate products, however, are not approved for use on kittens or nursing puppies. Organophosphates should only be used cautiously in cats. An extralabel regimen of weekly half-strength amitraz dips (0.0125 %) is effective against feline demodicosis. 45 Sedation and salivation are transient side effects, especially when the amitraz preparation is used fullstrength. 45 Diabetic cats with demodicosis should be treated with miticides other than amitraz. 31 Cheyletiella yasguri of dogs and Cheyletiella blakei of cats are large, surface-feeding mites that live in keratin (Table I). Their 35-day life cycle is spent entirely on the dog or cat. The mite has enormous hooked mouthparts and combed legs; it attaches its eggs to hair. The mites are very mobile and contagious by direct contact; the so-called walking dandruff can spread rapidly through a kennel or cattery. Puppies and kittens are most susceptible. Cheyletiella mites are not host specific, and a reference text is advisable for correct identification of the species. The hallmark of Cheyletiella is the moving white flakes along the dorsal midline and head of the dog and cat. Scraping, combing, or applying transparent adhesive tape to the suspect areas aids in disclosing the large, visible mites. Magnifying loupes and selective removal of questionable flakes or hairs represent the quickest method. Some fastidious cats may require skin scrapings or fecal flotations to reveal mites. 2.4.9.46.47 Dogs experience more pruritus associated with cheyletiellosis than do cats. The canine disease may resemble seborrhea oleosa or fleabite dermatitis. Affected dogs have scaly, oily skin. Cats may appear to have seborrhea sicca with scales and red scabs, or they may show no signs at all. Humans, especially cattery personnel, are highly susceptible to Cheyletiella infestation. Pruritus, erythematous papules, and pustules appear on the chest, arms, thighs, and abdomen. The human disease is transient (three weeks) without reexposure.4.11-13 Treatment Treatment of Cheyletiella mite infestation can be accomplished by using lime-sulfur dips, carbaryl shampoo or 5 % dust, 0.5 % malathion dips, or pyrethrins weekly for four or five treatments.2.9 Although amitraz has not been approved for use against Cheyletiella, this agent is effective The Compendium • Small Animal 789 TABLE II Host Anatomic Areas Preferred by Canine and Feline Mites2,7,8 Mite Preferred Location on Host Demodex species Localized: follicles of face, skull, ear canal, forelegs; Generalized: anywhere and everywhere Cheyletiella species Surface of dorsal midline Trombiculidae Surface of head, legs, and ventral areas Sarcoptes scabiei var. canis Epidermis of ear tips, elbows, and glabrous areas Notoedres cati Epidermis of ears, face, and feet Otodectes cynotis Surface of ear canals and periauricular areas Lynxacarus radovskyi Surface of perineum, tailhead, and tail tip Pneumonyssoides caninum Nasal sinus, nasal passages Dermanyssus gallinae Surface of legs and back Canine Breeds Predisposed to Demodicosis 2 ,5.18,19 Generalized Juvenile Demodicosis Afghan hound, beagle, Boston terrier, boxer, Chihuahua, Chinese shar peL chow chow, collie, dalmatian, dachshund, Doberman pinscher, English bulldog, German shepherd, Great Dane, Old English sheepdog, pointer, pit bullterrier, pug, Staffordshire bullterrier Chronic Demodectic Pododermatitis Great Dane, Newfoundland, Old English sheepdog, Saint Bernard Generalized Adult-Onset Demodicosis Cocker spaniel, Old English sheepdog, Scottish terrier, West Highland white terrier can be killed by carbaryl shampoos, powders, or dips; pyrethrin; or extralabel use of amitraz (0.025 %).2.5.9.32.51 SARCOPTES Clinical Manifestations on dogs (0.025%); one treatment is sufficient. 48 Subcutaneous ivermectin (300 J.lg/kg) repeated after a five-week interval is effective and useful for miticide-resistant cases and may be ideal for cattery and kennel infestations. 14 ,49 Regardless of the treatment used against Cheyletiella, all of the animals in the household or facility must be treated. TROMBICULIDAE Clinical Manifestations Trombiculiasis is infestation by parasitic, six-legged, larval chiggers. Dogs, cats, and humans can be parasitized by 20 of the more than 700 species of chiggers. Infestation is most prevalent during the late summer and fall and in animals frequenting fields or woodlands where the larval mites are contracted directly (Table III). The nymphs and adult chiggers are free-living and not parasitic. The bright orange-red mites are surface feeders; their salivary secretions induce intense pruritus that lasts longer than the mites are present on the body. Alopecia, pustules, and scaling of the head, ears, ventral trunk, legs, and paws can occur. The entire body can be afflicted; self-inflicted injury is often a problem. Diagnosis and Treatment Diagnosis can be made by scraping the mite from the lesion, but the mite may already have detached from the animal.2· 5.9,47.5o.51 Thus, chigger infestations might be more common than they are believed to be. Mites that are present Scabies caused by the mite Sarcoptes scabiei var. canis is often misdiagnosed as contact allergy, food allergy, atopy, or fleabite dermatitis. Many pruritus-producing skin diseases can resemble scabies. 52 This mite usually appears on dogs, occurs only rarely in cats,53.54 and spends its 17- to 21-day life cycle in epidermal pockets. The large female mite lays three to five eggs per day in freshly burrowed tunnels (Table I). The male mite, along with mites in the larval and nymph stages, lives in vacated burrows. The male dies after copulation. Sarcoptes mites have a long, unsegmented pedicel and a terminal anus. I .2 LTENSE pmdtu, iuducod by hypmeu,itivity to bucrowing female mites is a consistent clinical sign. The mite targets the pinnae, elbows, back, chest, abdomen, or hairless areas. The entire body can be affected. Alopecia, hemorrhagic crusts, and papules are worsened by self-inflicted injury. The skin becomes Iichenified, and secondary infection and lymphadenopathy occur. The animal can become debilitated; but well-nourished, well-groomed dogs also can have scabies. Frequent grooming of dogs and frequent insecticidal shampooing can cause and mask scabies in some pampered pets; the resultant condition has been called scabies incognito. Rubbing the infested animal's ear tip may elicit scratching movements of the hindlimb; this pinna-pedal reflex suggests scabies.2.33.52-54 792 The Compendium • Small Animal Figure 3A Figure 38 Figure 3-(A) Adult-onset demodicosis in a six-year-old intact male Scottish terrier with atopy. Extreme pyoderma and self-mutilation are evident. (8) The same dog after six weekly amitraz (0.05%) treatments. three weeks of oxacillin sodium therapy. and fatty acid supplementation. Figure 4A Figure 48 Figure 4-(A) Demodex cat; mite (30 /-1m x 200 /-1m) from a 14-year-old neutered tomcat with feline immunodeficiency virus infection. Compare its length and width with the length and width of the canine mite in Figure 1. (x60) (8) Appearance of the host's lesions. Multiple deep skin scrapings from scattered reddened crusty areas may reveal mites or eggs. To obtain an adequate skin scraping, the clinician must scrape hairless areas deeply enough for the area to ooze blood. In 35 % to 50% of cases, no mites are found and diagnosis is based on history, clinical examination, and response to treatment. A history of sudden-onset pruritus, exposure to a kennel or pet shop, or pruritus among humans in the household suggests scabies. 52 The mite is highly contagious by direct contact to other dogs; up to 50% of canine cases result in human disease. Humans evidence pruritic lesions on the arms, legs, and trunk. The canine parasite in humans is self-limiting and transient without reexposure. 2 .4.11 Treatment Treatment of infected dogs includes cleansing shampoos to remove debris as well as systemic antibiotics and antiinflammatory agents to treat infection and self-inflicted injury. Laundering the animal's bedding eliminates a source of reinfestation. Weekly malathion or phosmet dips have been suggested but may be ineffective because of resistant mites. Lime-sulfur dip (2.5%) is safe and effective; five dips are given at five-day intervals. Lime sulfur is also antifungal, antibacterial, and antipruritic. 2 . 33 .52 Amitraz is effective against Sarcoptes mites but has not been approved for that use. A single application of amitraz (0.025 %) is effective in 98 % of cases. Some dogs require a second or third application. 14.28.32.48.52 Extralabel use of oral or injected ivermectin (200 /-Ig/kg) is effective; a single treatment kills the mites. 11.14.28.35.52.55.56 Regardless of the method of treatment, all dogs in a household must be treated. The Compendium • Small Animal 793 TABLE III Geographic Distribution of Canine and Feline Mites in the United States2 ,5,7-10 TABLE IV Zoonotic Mites of Dogs and Cats2,4,7,11-15 Mite Mite Distribution Demodex species Throughout the United States Cheyletiella species Throughout the United States Trombiculidae Uncommon; fields and woodlands, especially in the central United States Human Anatomy Affected Cheyletiella species Arms, thighs, trunk Trombiculidae Legs, arms Sarcoptes scabiei var. caniso Arms, legs, trunk, neck Notoedres catiO Arms, trunk, neck Otodectes cynotisO Arms, trunk Sarcoptes scabiei var. canis Throughout the United States Lynxacarus radovskyio Arms, forearms Notoedres cati Uncommon; scattered enzootic areas Dermanyssus gallinaeo Arms, chest Otodectes cynotis Throughout the United States Lynxacarus radovskyi Rare; Hawaii, Puerto Rico, southern Florida Pneumonyssoides caninum Rare; throughout the United States Dermanyssus gallinae Rare; bird nests, henhouses, pigeon coops NOTOEDRES CATI Clinical Manifestations Notoedres cati is the mite of feline scabies. The mite is smaller than Sarcoptes mites and has a dorsal anus and evident body striations (Figure 5 and Table I). Its life cycle is similar to that of Sarcoptes mites. Notoedres cati is highly contagious by direct contact and is present in large numbers on the cat. All of the cats in a household or neighborhood may become infected. Although Notoedres mites are not a common parasite of cats, enzootic feline populations create cluster outbreaks with high morbidity. 2.9.10.57 CLINICAL ,ign, include inten,. pm,itu, attributable to a hypersensitivity response to the burrowing female mites as well as alopecia, crusting, and scaling of the face, ear tips, and distal extremities. Hyperpigmentation, lichenification, self-inflicted injury, and secondary skin infection can be severe (Figure 5). Young and chronically infected cats become debilitated 2,9.10,47 (Figure 6). Humans contacting infected cats can develop pruritic skin disease. Papules, crusts, and excoriations of the arms, legs, and trunk can occur. The human disease is self-limiting and transient without reexposure. 4.11 Dogs rarely become parasitized by Notoedres mites. 2,47 Skin scrapings of lesions reveal numerous mites and eggs (Figure 7). The mites are active and rapidly spread over the cat's body. Diagnosis is usually easy. °Extralabel use of ivermectin in dogs and cats kills these mites; ivermectin is contraindicated for collies and sheepdogs, Treatment Treatment includes cleansing shampoos to remove scales and crusts. Antibiotics for secondary skin infection and corticosteroids to treat pruritus and self-inflicted injury may be needed. Four to six weekly dips with 2.5% lime sulfur are safe and effective and alleviate pruritus. 2.9.11 Amitraz dips (0.0125%) repeated at two-week intervals are reportedly effective, but this regimen is extralabel. II Stronger amitraz dips (0.025%) have reportedly been effective. 32 ,58 Malathion dip also is effective. 2 All cats in the household must be treated. Extralabel use of ivermectin is highly effective against Notoedres mites. I 1.33,59-61 I have treated an epizootic of Notoedres mange using subcutaneous ivermectin (300 llg/kg) on cats as young as four weeks. Over 200 cats have been treated; most need only one ivermectin injection. No adverse effects have been apparent. 10 OTODECTES CYNOTIS Clinical Manifestations Dogs and cats share the same ear mite species, Otodectes cynotis. The mite is a large and mobile surface feeder (Table I). Transmission is by direct contact between pets; the mite is not host specific. Otodectes cynotis mites have a 21-day life cycle on the host; the life cycle features a distinct stage involving deutonymphs. Deutonymphs are a sexually undifferentiated stage and will be joined end to end by an adult male mite (Figure 8). If the deutonymph molts to become a female, it will be fertilized. If a male develops or if a deutonymph fails to be joined by a male, no reproduction occurs. Ear mites have characteristic long legs that extend beyond the body as well as short pedicels on these legs l.2,47 (Figure 8 and Table I). Ear mites irritate the ear canal and hypersensitize the pet. The mite antigen induces antibody production soon after the pet is parasitized,2 The result is pruritus; head shaking; and a heavy, dark, discolored wax discharge. Ear 794 The Compendium • Small Animal Figure 5-Reactive skin from a cat with Notoedres cati infestation. Hyperplasia, excessive keratinization, deeply burrowing mites, and inflammatory infiltrates are evident. (x 25) Figure 7-Notoedres cati mite (length 200 J.(m). Body striations are evident, as is the absence of a terminal anus. (x 78) mites do not thrive in infected ears; patients with purulent .otitis are usually devoid of ear mites. The mites can leave the ear canal and irritate the neck, head, rump, and tail. 2.9 Head shaking can induce aural hematomas, and ear scratching can cause localized moist dermatitis and traumatic skin excoriations. Humans can develop papules on the arms and trunk; this condition is self-limiting without reexposure. 4 .62 Diagnosis of Otodectes cynotis is by direct visualization or microscopic examination of a swab smear. Treatment Miticidal therapy is preceded by gentle cleansing of the ear canals with a cerumenolytic agent, such as mineral oil or squalene. Such miticides as topical thiabendazole, rotenone in oil, or methylcarbaryI are all effective. Treatment intervals are staggered to increase kill of wandering mites; periauricular areas can also be treated to kill any mobile mites. Because the mites are so contagious, all animals in the household, kennel, or cattery should be treated. 2.47 Figure 6-A debilitated five-month-old male kitten. Notoedres cati infestation over its whole body responded well to ivermectin (300 J.(g/kg) and supportive care. Figure 8-Adult male Otodectes cynotis mite attached to a deutonymph. Fertilization will occur if the deutonymph develops into a female mite. The male measures 250 J.(m x 300 J.(m. Eight long legs and short pedicels are evident. (x60) E XTRALABEL use of ;venneclin (;njectinn of 200 In 400 J.(g/kg) can successfully eliminate Otodectes cynotis mites in dogs and cats. Ivermectin may be the ideal remedy for chronic infestations in a kennel or cattery. 4.55.63 Extralabel use of amitraz (0.05% on the body and 0.5% diluted with 50% propylene glycol in the ear canals) is reportedly effective against Otodectes cynotisY Amitraz at a concentration of 0.025 % is also effective. 48 LYNXACARUS RADOVSKYI Clinical Manifestations Lynxacarus radovskyi is the cat fur mite. It is a large hair-clasping surface feeder that can be easily seen through a head loupe (Table I). The mite has modified sternal plates that allow it to clasp a hair and travel along hair shafts over the eat's body I (Figure 9). The Compendium • Small Animal 795 Figure 9A Figure 9C Figure 9-(A) Female Lynxacarus radovskyi mite measuring 500 JAm long. Modified sternal plates enclose the eat's hair. The first pair of legs moves the mite along the hair. (x60) (8) Male mite 430 JAm long. (x60) (C) Fur mite eggs measuring approximately 200 JAm long attached to the eat's hair. (x60) Figure 98 Although Lynxacarus radovskyi is not common throughout the United States, it is enzootic in a few areas (Table III).6.7.63-66 The mite has an affinity for the tail tip, tailhead, and perineum. When this parasite is present in large numbers, the haircoat can feel granular and appear peppered. Small populations of fur mites cause no clinical signs; but heavily parasitized cats have pruritus, regional alopecia, and areas of shortened fur and develop a dry, rust-colored coat with such secondary signs as gingivitis or hair balls. 7 The mite is contagious to cats and humans by direct contact. One of my clients had a papular forearm rash that resolved when her heavily parasitized cat was cleansed. Diagnosis is swiftly made by plucking suspect hairs to reveal the mite or attached eggs (Figure 9). Treatment Treatment is easily accomplished using 2.5 % lime-sulfur dips or pyrethrin shampoos, powders, or sprays.25 Flea 796 The Compendium • Small Animal Figure 10A Figure 108 collars do not work. House cats should be separated from feral cats to prevent reinfestation. 7 Subcutaneous ivermectin (300 j.Lg/kg) has been effective in killing Lynxacarus radovskyi in an ongoing epizootic I am treating, PNEUMONYSSOIDES CANINUM Clinical Manifestations Pneumonyssoides caninum is the nasal or sinus mite of dogs. As with the previously mentioned cat fur mite, little is known about the complete life cycle of Pneumonyssoides caninum. Like fur mite infestation, Pneumonyssoides caninum infestation responds favorably to treatment. The sheltered habitat of the nasal sinus mite, however, protects it from injury and investigation, Larval and adult stages are usually seen, and the female may be ovoviviparous, The mode of contagion is unknown but is probably direct contact. The mite may cause no signs; however, rhinitis, serous nasal discharge, facial pruritus, sneezing, nocturnal restlessness, stertorous breathing sounds, and orbital infection have been reported, The mite has reportedly been found in lung, liver, and perirenal tissue8.68 (Figure 10). Diagnosis is made by finding the long-legged mite crawling on the dog's muzzle, in nasal discharge, or in the nasal passages (observed by rhinoscopy). The mite could be confused with Dermanyssus mites or larval ticks, Treatment Figure 10C Figure 10-(A) This two-year-old male English bulldog has nasal discharge and pruritic facial irritation resulting from Pneumonyssoides caninum infestation. (8) A typical Pneumonyssoides caninum mite embedded in dried nasal exudate from the dog. (C) A long-legged nasal mite found wandering on the dog's muzzle. (x60) The mite can be killed by ivermectin injections (200 j.Lg/ kg); two doses three weeks apart is an effective regimen. 8 Before this extralabel use of ivermectin was made, therapies for nasal sinus mite infestations included ether, rotenone, cresol, and organophosphates administered by nasal drops, inhaler bags, or insecticide strips,68.69 DERMANYSSUS GALLINAE Clinical Manifestations The red poultry mite, Dermanyssus gallinae, infests dogs, cats, and humans contacting infested bird nests, 798 The Compendium • Small Animal henhouses, or pigeon COOpS.2.70.15 The eight-legged nymph and adult stages are parasitic. The mite has long anterior legs. It tends to infest the back and legs of pets. Pruritus, papules, crusts, and erythema can be present. The mite is diagnosed by skin scrapings. Treatment Treatment is accomplished with lime sulfur, pyrethrins, or any safe acaricide. Ivermectin injections are effective in killing Dermanyssus gallinae on poultry71; ivermectin may be as effective when used in the rare canine and feline cases of infestation. Avoidance of the source of the parasites or treatment of the source prevents reinfestation. CONCLUSION Parasitic mite infestations of dogs and cats can be difficult or impossible to cure. Inherited factors, the contagious nature of the parasites, and their zoonotic potential complicate the management of these parasites. Because extralabel or nonapproved use of therapeutics may be necessary, owner awareness and cooperation are critical. Milbemycin, which has recently been approved for use in the United States, might someday be used to treat parasitism that is resistant to ivermectin or that has occurred in animals unable to tolerate ivermectin. About the Author Dr. Foley is affiliated with the Upper Keys Veterinary Clinic located in Islamorada. Florida. REFERENCES 1. Georgi JR, Georgi ME: Parasitology for Veterinarians, ed 5. Philadelphia, WB Saunders Co, 1990. 2. Muller GH, Kirk RW, Scott DW: Cutaneous parasitology, in Small Animal Dermatology, ed 3. Philadelphia, WB Saunders Co, 1989, pp 358-407. 3. Chesney CJ: An unusual species of Demodex mite in a cat. Vet Rec 123:671-673, 1988. 4. Scott DW, Hom RT: Zoonotic dermatoses of dogs and cats. Vet Clin Nonh Am {Small Anim PractJ 17:117-144, 1987. 5. Greene RT, Scheidt VJ, Moncol DJ: Trombiculiasis in a cat. JAVMA 188:1054-1055,1986. 6. Tenorio JM: A new species of Lynxacarus (Acarina:Astigmata:Listrophoridae) from Felis catus in the Hawaiian islands. J Med Entomol 11 :599-604, 1974. 7. Foley RH: An epizootic of a rare fur mite in an island's cat population. Feline Pract, accepted for publication. 8. Mundell AC, Ihrke PJ: Ivermectin in the treatment of Pneumonyssoides caninum: A case report. JAAHA 26:393-396, 1990. 9. Scott DW: Feline dermatology 1900-1978: A monograph. JAAHA 16:331-459, 1980. 10. Foley RH: A notoedric mange outbreak in an island cat population. Feline Pract, accepted for publication. 11. Merchant SR: Zoonotic disease with cutaneous manifestations-Part I. Compend Cantin Educ Pract Vet 12(3):371-378, 1990. 12. Fox JG, Reed C: Cheyletiella infestation of cats and their owners. Arch DermatoII14:1233-1234, 1978. 13. Keh B, Lave RS, Schachter SP: Cheyletiella blakei, an ectoparasite of cats, as cause of cryptic arthropod infestations affecting humans. West J Med 146: 192-194, 1987. 14. Schmeitzel LP: Cheyletiellosis and scabies. Vet Clin North Am {Small Anim PractJ 18:1069-1076,1988. 15. Regan AM, Metersky MC, Craven DE: Nosocomial dermatitis and pruritus caused by pigeon mite infestation. Arch Intern Med 147:2185-2187, 1987. 16. Greve JH, Gaafar SM: Natural transmission of Demodex canis in dogs. JAVMA 148: 1043-1045, 1966. 17. Scott DW: Canine demodicosis. Vet Clin North Am {Small Anim PractJ 9:79-92, 1979. 18. Folz SD: Demodicosis (Demodex canis). Compend Cantin Educ Pract Vet 5(2):116-121,1983. 19. Miller WH: Canine demodicosis. Compend Cantin Educ Pract Vet 2(4):334-342, 1980. 20. Sako S, Yamane 0: Studies on the canine demodicosis. II. The significance of presence of the parasite in lymphatic glands of affected dogs. Jpn J Parasitol 11 :93, 1962. 21. Greve JH, Gaafar SM: Effect of hypothyroidism on canine demodicosis. Am J Vet Res 25:520-522, 1964. 22. Barta 0, Turnwald GH: Demodicosis, pyoderma, and other skin diseases of young dogs, and their associations with immunologic dysfunctions. Compend Cantin Educ Pract Vet 5(12):955-1003, 1983. 23. Scott DW, Farrow BRH, Schultz RD: Studies on the therapeutic and immunologic aspects of generalized demodectic mange in the dog. JAAHA 10:233-244, 1974. 24. Scott DW, Schultz RD, Baker E: Further studies on the therapeutic and immunologic aspects of generalized demodectic mange in the dog. JAAHA 12:203-213, 1976. 25. Krawiec DR, Gaafar SM: Studies on the immunology of canine demodicosis. JAAHA 16:669-676, 1980. 26. American Academy of Veterinary Dermatology Business Meeting, Atlanta, 1981 (editorial). JAVMA 182: 1048, 1983. 27. Muller GH: Amitraz treatment of demodicosis. JAAHA 19:435-441, 1983. 28. Reedy LW: Common parasitic problems in small animal dermatology. JAVMA 188:362-364, 1986. 29. Manning J: Cutaneous manifestations of internal mediated disease, in Proc Annu Cornell Conf 81: 172-173, 1989. 30. Kwochka KW, Kunkle GA, O'Neill Foil C: The efficacy of amitraz for generalized demodicosis in dogs: A study of two concentrations and frequencies of application. Compend Cantin Educ Pract Vet 7(1):8-18, 1985. 31. Hsu WH, Schaffer DD: Effects of topical application of amitraz on plasma glucose and insulin concentration in dogs. Am J Vet Res 49: 130-131, 1988. 32. Bussieras J, Chermette R: Amitraz and canine demodicosis. JAAHA 22:779-782, 1986. 33. Bevier DE: Parasitic dermatoses in the dog and cat. Parts I and II. Proc AAHA 57:24-89, 1990. 34. Scott DW, Walton AK: Experiences with the use of arnitraz and ivermectin for the treatment of generalized demodicosis in dogs. JAAHA 21:535-541,1985. 35. Bennet DG: Clinical pharmacology of ivermectin. JAVMA 189: 100104, 1986. 36. Paul AJ, Tranquilli WI, Seward RC, et al: Clinical observations in collies given ivermectin orally. Am J Vet Res 48:684-685, 1987. 37. Houston DM, Parent J, Matushek KJ: Ivermectin toxicosis in a dog. JAVMA 191:78-80, 1987. 38. Pugliese A, Peralta A, Pennisi M, et al: Ivermectin against parasites of the dog and cat. Obiettivie Documenti Veterinari 6:57-58, 1985. 39. Conroy JD, Healey MC, Bane AG: New Demodex sp. infesting a cat: A case report. JAAHA 18:405, 1982. 40. McDougal BJ, Novak CP: Feline demodicosis caused by unnamed Demodex mite. Compend Cantin Educ Pract Vet 11 :820-822, 1986. 41. White SD, Carpenter JL, Moore FM, et al: Generalized demodicosis associated with diabetes mellitus in two cats. JAVMA 191:448-450, 1987. 42. Medleau L, Brown CA, Brown SA, et al: Demodicosis in cats. JAAHA 24:85-91, 1988. 43. Chalmers S, Schick RO, Jeffers J: Demodicosis in two cats seropositive for feline immunodeficiency virus. JAVMA 194:256, 1989. 44. Stogdale L, Moore DJ: Feline demodicosis. JAAHA 18:427, 1982. 45. Cowan LA, Campbell K: Generalized demodicosis in a cat responsive to amitraz. JAVMA 192: 1442-1444, 1988. 46. McKeever PJ, Allen SK: Dermatitis associated with Cheyletiella infestation in cats. JAVMA 174(7):718-720, 1979. 47. Fadok VA: Miscellaneous parasites of the skin. Compend Contin Educ Pract Vet 2(10):782, 1980. 48. Folz SD, Kakuk TJ, Henke CL, et al: Clinical evaluation of amitraz for treatment of canine scabies. Mod Vet Pract 65:597-600, 1984. 49. Pardis M, Scott D, Villeneuve A: Efficacy of ivermectin against Cheyletiella blakei infestation in cats. JAAHA 26:126-128, 1990. 50. Hardison JL: A case of Eutrombicula alfreddugesi (chiggers) in a cat. VM SAC 72:47, 1977. 51. Lowenstine U, Carpenter JL, O'Connor BM: Trombiculosis in a cat. JAVMA 175:289, 1979. 52. Folz SD: Canine scabies. Compend Contin Educ Pract Vet 6(3): 176180, 1984. 53. Hawkins JA, McDonald RK, Woody BJ: Sarcoptes scabies infestation in a cat. JAVMA 190: 1572, 1987. 54. Kershaw A: Sarcoptes scabies infestation in a cat. Vet Rec 124:537538, 1989. 55. Yazwinski TA, Pole L, Tilley W, et al: Efficacy of ivermectin against Sarcoptes scabiei and Otodectes cynotis infestations of dogs. VM SAC 76: 1749-1751, 1981. 56. Scheidt VJ, Medleau L, Seward RL, et al: An evaluation of ivermectin in the treatment of sarcoptic mange in dogs. Am J Vet Res 45:1201-1202,1984. 57. Kangstrom LE: Ettfaell va Kattscabb. Svensk Veterinartidning 36(14):701-702, 1984. 58. Wilkinson GT: An overvie~ of feline skin disease. Proc Univ Sydney Postgrad Comm Vet Sci 57:277, 1981. 59. Bigler B, Waber S, pzister K: Erste erfolgversprechende Ergebnisse 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. in der Behandlung von Notoedres cati mit Ivermectin. Schweiz Arch Tierheilkd 126:365-367, 1984. Suarez CJM, Bertero SI: Tratamiento de la sarna notoedrica del gato con ivermectin: Informe preliminar. Vet Argent 3(24):338-344, 1986. Proglagen G: Practical trial with ivermectin against notoedric mange in cats. Clin Vet {Bologna} 109:417-420, 1986. Harwick RP: Lesions caused by canine ear mites. Arch Dermatol 114: 130, 1978. Schneck G: Use of ivermectin against ear mites in cats. Vet Rec 123:599, 1988. Fox I: Felistrophorus, a new genus of mites on cats in Puerto Rico (Acarina:Listrophoridae). Proc Entomol Soc [Washington} 79:242244, 1977. Bowman WL: The cat fur-mite (Lynxacarus radovskyl) in Australia. Aust Vet J 54:403-404, 1978. Munroe R, Munro HMC: Lynxacarus on cats in Fiji. Aust Vet J 55:90, 1979. Greve JH, Gerrish RR: Fur-mites (Lynxacarus) from cats in Florida. Feline Pract 11:28-30, 1981. Blagburn BL, Didier PJ, Todd KS: Pneumonyssoides caninum in a dog. VM SAC 77:768-770, 1982. Whitney GD: Treatment of P. caninum infestation. Mod Vet Pract 54:44, 1973. Ramsay GW, Mason PC: Chicken mite (D. gallinae) infesting a dog. NZ Vet J 23: 155, 1975. Zeman P: Systemic efficacy of ivermectin against Dermanyssus gallinae in fowls. Vet Parasitol {Czech} 23:141-146, 1987.