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HAIRCLASPING MITES: Species

Cheyletiella mites are sometimes referred to as “walking dandruff” mites. Cheyletiella yasguri affects dogs. Cheyletiella blakei has been reported in cats around the world.

Lynxacarus radovskyi occurs in cats and from the lynx. Similar mites described from other species have been found on bobcats and weasels.

Overview of Life Cycle

• Adult Cheyletiella mites are nonburrowing and live on the skin, where they feed on the keratin layer of the epidermis. Cheyletiella blakei also feeds on the hair coat of the cat.
• Cheyletiella mites are very mobile and are contagious by direct contact. These mites have been found on fleas, lice, and flies; it has been hypothesized that this is one means by which they move between hosts.
• Lynxacarus radovskyi mites are laterally compressed and found clinging to the hairs of the cat. The large eggs (200 μm in length) are glued to the hairs and produce a six-legged larva. The larva molts to an eight-legged nymph, which molts to the adult.

Stages

• Cheyletiella spp. have five developmental stages: egg, prelarva, larva, a first and second nymphal stage, and adult. Eggs are very large (about 240-μm long) and glued to the hairs. The prelarva is a quiescent nonfeeding stage that appears to be no more than a legless sack. Adult Cheyletiella mites are large, 500-μm long, and visible to the naked eye. The key morphologic feature is the large palpal claws.
• Lynxacarus radovskyi eggs are about 200-μm long and are attached by one end to the hairs of the cat. The six-legged larvae and eight-legged nymphs are also found on the hairs of the cat. Adult Lynxacarus mites are about 500-μm long, are laterally compressed, and have short legs anteriorly on the first two-thirds of the body. They are found clinging to the hairs with the anterior end held near the hair shaft.

Disease

• Cheyletiella infestations cause exfoliative dermatitis with flaky, bran-like squames. Cheyletiella principally affects the back and is a common etiologic agent of exfoliative dermatitis on the dorsum. The visual appearance of “walking dandruff” is caused by the agitation of epidermal debris by the activities of the mites. Cats sometimes develop miliary dermatitis with reddish yellow crusts.
• In Lynxacarus infestations, mites most commonly are found on the tail head and tip and in the perineal area. In heavy infestations, mites may be found over the cat’s entire body. The hair coat can appear dull, dry, and rust-colored. The mites and eggs present on the hairs give the cat a “peppered” appearance, and the coat may be granular to the touch. Cats may present with gastrointestinal disturbances, rectal irritation, or hairballs (due to excessive grooming). In addition, infested cats may have gingivitis, anorexia, restlessness, fever, and weight loss.

Prevalence

• Cheyletiella infestations, though relatively uncommon, seem to occur most often on puppies from large breeding facilities.
• Lynxacarus infestations in cats are rare in most parts of the United States but can be common in certain areas of the more tropical regions, such as Hawaii, Puerto Rico, and the Florida Keys. The mite is also found in Fiji and Australia.

Host Associations and Transmission Between Hosts

• Both Cheyletiella and Lynxacarus mites appear to be restricted to their respective hosts.

Prepatent Period and Environmental Factors

• In the case of cheyletiellosis, it takes three to five weeks for an infection to develop from a single mite to a recognized infestation.
• The prepatent period for lynxacariasis is not known but is considered to be three to five weeks.

Site of Infection and Pathogenesis

• Cheyletiella mites typically are found on the dorsum.
• Lynxacarus mites typically are associated with the numerous mites clinging to the hairs and the associated pruritus induced by their presence.

Diagnosis

• Mites typically can be found upon observation and identified by their distinct appearance. An examination of the skin with a hand lens often will clearly reveal the mites.
• Mites sometimes are found in the feces of cats that have groomed the mites from their body surface.
• Specific identification can usually be made by the host association. Specific morphologic diagnosis of the Cheyletiella spp. can be made by very close examination of the shape of a seta on the fourth pair of legs; the seta is heart-shaped in C. yasguri and conical in C. blakei.

Treatment

• Ivermectin (200 to 300 μg/kg) has been found to be highly efficacious.
• Shampoos containing pyrethrin are effective.
• Selamectin has efficacy.
• Fipronil is likely effective.

Control and Prevention

• Infestations in cats and dogs can be prevented by routine administration of selamectin or fipronil on a monthly basis.

Public Health Considerations

• Lesions on human owners are associated with cheyletiellosis in dogs far less often than with cheyletiellosis in cats. It is unknown if this is attributable to the mite’s behavior or the different relationship between people and their dogs versus people and their cats.
• Lynxacarus radovskyi has not been associated with lesions on the owners of infested cats.

SARCOPTIC MANGE: Species

Sarcoptes scabiei infests a wide range of mammalian hosts, including dogs and other canids, human beings, horses, and cattle; cats are rarely infested with this mite. In all hosts, mites tunnel in the epidermis and produce an intensely pruritic dermatitis with hyperkeratosis and alopecia. Infestations between hosts occur, but the mites tend not to survive for long on hosts other than those to which they are adapted; thus, they are considered host-adapted strains of a single species rather than distinct species.

Overview of Life Cycle

• Mites live in burrows in the skin where the female glues her eggs to the tunnel walls. Eggs hatch to produce six-legged larvae that molt to become first- and second-stage nymphs before becoming adults.

Stages

• Eggs are large (about 230-μm long) and ellipsoid.
• Adults are approximately 0.5-mm long. The first two pairs of legs of the eight-legged adult females end in long and unbranched stalks (pedicels) that end in a wineglass-shaped caruncle; the third and fourth pairs of legs end in long setae. Male mites have setae only on the third pair of legs, with pedicels and caruncles on the other legs. Males also have marked thickening of the cuticle between the various plates on the ventral surface that appear dark, compared with the rest of the body. The dorsal surface of both the male and female mites is covered with large triangular spines (most conspicuous in the female).

Disease

• Infestations typically produce hyperkeratosis and alopecia.
• Lesions become highly pruritic and are often the cause of self mutilation. Lesions may become bloody from the scratching of the affected dog.
• Mites typically are found on the margins of the ears and on the knees of affected animals, although lesions are also common on the flanks and ventrum, especially in more severe cases.

Prevalence

• Infestations are relatively rare, or at least, severe cases are rare.
• There may be cases where severe skin disease can occur even though repeated skin scrapings recover no mites.
• Infestations appear to occur throughout the range of the dog and are present in both cool and tropical climates.

Host Associations and Transmission Between Hosts

• This mite appears to be restricted to the dog but can be spread between canids rather freely. Sarcoptes scabiei is a serious parasite of the fox, which could perhaps be considered a reservoir host in areas where foxes are common.

Prepatent Period and Environmental Factors

• The prepatent period and environmental factors are unknown.

Site of Infection and Pathogenesis

• Mites are found in burrows in the skin.
• Lesions typically are first noted on the margins of the ears, the knees, or the feet of infested animals.
• Infestations initially produce dry, crusted lesions that become pruritic and on excoriation often develop a serous exudate.
• Infection is often accompanied by alopecia, and some dogs develop hyperkeratosis.

Diagnosis

• Skin scrapings for sarcoptic mange mites should be deep enough to examine the full thickness of the epidermis and produce a sample that is tinged with blood.
• Often it is helpful to dip the scraping scalpel in mineral oil and tease apart the scrapings on the microscope slide with needles, especially when significant hyperakeratosis is present.
• Mites and their eggs will be clearly visible at the lowest power of the compound microscope.

Treatment

• Cases have been treated with ivermectin (200 μg/kg).
• Selamectin is efficacious.
• Fipronil has been shown to aid in the control of sarcoptic mange.

Control and Prevention

• Selamectin likely will prevent infestations with these parasites.

Public Health Considerations

• People can become infested with the mites present on their dogs. The lesions that are produced will be highly pruritic but will almost always clear without the need of specific treatment for the mite infestation.

NOTOEDRIC MANGE: Species

Notoedres cati occurs in cats and other members of the Felidae throughout the world, including ocelots, Florida panthers, tigers, bobcats, lynx, snow leopards, and cheetahs. Other species of Notoedres are generally found as parasites of lagomorphs, rodents, and bats. Cats are only very rarely infected with the related mite, S. scabiei.

Overview of Life Cycle

• Mites live in deep burrows within the dermis. The female lays eggs in the burrows, sometimes in a semicircle in a cave excavated in the skin.
• Females lay three to four eggs each day, and the eggs hatch four to five days after they are laid.
• The larva typically leaves the tunnels in which it hatches to crawl about on the surface of the skin before digging its own molting burrow. The larva enters the burrow and over the next week or so molts to the first nymphal stage.
• The first nymphal stage then leaves the burrow and enters a second, more superficial, burrow where it molts again to the second nymphal stage. This stage digs a third burrow in which the adult develops.
• The adult female tends to stay in the third nymphal burrow, whereas the adult male usually migrates to find a female with which to mate. Adults can appear as soon as 12 days after hatching, although it usually takes longer.
• The stages transmitted between hosts are usually the wandering larvae and nymphs.

Stages

• Eggs are oval and approximately 100 μm in length.
• Larvae have six legs.
• Nymphs have eight legs and are similar to adults (although smaller and lacking genital openings).
• Adults are almost round in dorsal view with a diameter of approximately 200 to 240 μm. Adults are eight-legged and have typical sarcoptiform pretarsi with a long, unsegmented pedicel. The male has a dorsal anus and ventral penis. The male has suckers (caruncles) on the ends of the first, second, and fourth pairs of legs; the female has suckers only on the first and second pairs of legs.

Disease

• Typical signs of infections include lichenification of the skin on the ear tips, face, and distal extremities. The skin can become acanthotic and hyperkeratotic with gray crusts and scale.
• Associated clinical signs include intense pruritus and alopecia that may be accompanied by self mutilation, weight loss, fever, or debilitation and sometimes death.
• Cats may develop leucocytosis with relative and absolute eosinophilia.

Prevalence

• This mite has been reported from most countries of the world and often seems to present as epizootics among groups of animals.
• In the United States, epizootics have been reported from the Florida Keys.

Host Associations and Transmission Between Hosts

• Notoedres cati infections are acquired by direct contact between cats.
• The species on rabbits may be the same as that on cats; in wild or hunting felids, the infestation may be acquired from captured rabbits.

Prepatent Period and Environmental Factors

• It likely takes several weeks to a month after the initial infection for notable lesions to appear on cats.

Site of Infection and Pathogenesis

• Mites are found in the skin of the cat and usually are detected first on the margins of the ears.
• All stages induce disease in the affected cat.

Diagnosis

• Mites typically are found in skin scrapings.
• Mites are smaller than S. scabiei. The male has a dorsal anus, and the female lacks the large triangular spines present on the surface of Sarcoptes.
• Because of the grooming behavior of the cat, mites often are detected in fecal examinations.

Treatment

• Ivermectin (200 to 300 μg/kg) is effective. Cats with severe lesions sometimes may also be administed penicillin for secondary bacterial infections and corticosteroids to alleviate the signs and reduce self-mutilation and hypersensitity reactions after treatment.
• Ivermectin toxicity has been reported in a few cats that have been treated with ivermectin at 400 μg/kg.
• Selamectin is an effective treatment and preventive.
• Fipronil is an effective treatment and preventive.
• Pyrethrin shampoos sometimes are used to clean the cat and soften the skin to aid in removal of the cutaneous crusts.

Control and Prevention

• Routine administration of monthly selamectin or fipronil may help prevent infestations in cats.

Public Health Considerations

• People living with infested cats sometimes will develop papular and pruritic rashes on the arms or legs. Typically, mite infestations do not persist on the infested humans.

EAR MITES OR OTODECTIC MANGE: Species

Otodectes cynotis has been reported from dogs, cats, foxes, and ferrets worldwide.

Overview of Life Cycle

• The complete egg-to-egg cycle takes 18 to 28 days. The egg hatches to produce a larva, a protonymph, and a deutonymph. Each stage takes a minimum of about three to five days of maturation to reach the next stage. The pairing of the male and a deutonymph takes place, and fertilization occurs as soon as the female molts to the adult stage.

Stages

• Eggs are large (about 200 μm in length).
• A six-legged larva hatches from the egg and goes through first and second nymphal stages before becoming an adult.
• Adult females are 350 to 450 μm in length, and adult males are 275 to 360 μm in length.
• The adult male has short pretarsi with wineglass-shaped caruncles on the distal end of each leg. The female has caruncles on only the first two pairs of legs, with long hairs on the posterior two pairs of legs. The posterior of the male has a pair of suckers used to grasp the female during copulation.

Disease

• Clinical signs include shaking of the head, scratching at the ears, inflammation of the ear canals, and accumulation of copious cerumen and frequently serous to purulent exudates, depending on the nature of secondary infectious agents.
• In very heavy infestations, mites may leave the ear canal and cause infestations on the head and associated body parts of the dog or cat. In rare cases, these animals may present with miliary dermatitis.
• Cats may have what appear to be significant lesions with large quantities of dark cerumen and even blood in the ear canal, yet only one or two mites are present. Other cats may have very clean ear canals and as many as 50 mites present. Still other cats may have thousands of mites in an ear and yet exhibit few, if any, outward signs. The ears may be filled with a dry and waxy parchment-like material that occurs as sheets throughout the ear canal.

Prevalence

• Infestations are not uncommon in dogs and cats that do not receive routine veterinary care.

Host Associations and Transmission Between Hosts

• Infestations in dogs or cats can be transferred between hosts by close contact.
• When mites are present in one dog or cat in a household, it is essential that all dogs and cats in the household be treated at the same time.

Prepatent Period and Environmental Factors

• The prepatent period is unknown, but the complete life cycle takes approximately 18 to 28 days.

Site of Infection and Pathogenesis

• Mites live routinely in the ear canal. Cats can have more than 1,000 mites per ear; the numbers present in dogs are usually much lower.
• The ear canal epithelium becomes hyperkeratotitc and hyperplastic. with dramatic hyperplasia of the ceruminous and sebaceous glands. There is a marked increase in mast cells and macrophages, and the venules become dilated. Animals developed IgE levels to the infestation about two weeks after becoming infested.

Diagnosis

• Mites in the ear may be observed with an otoscope or on swabs of the ear canal.

Treatment

• Selamectin is efficacious for treating dogs and cats.
• Cats can be treated with approved products of ivermectin (Acarexx) or milbemycin (Milbemite) that are formulated for application to the ear canal.
• Cleaning of the ear canal is always recommended.
• When secondary infections with bacteria or fungi are suspected, these conditions should also be treated.

Control and Prevention

• Routine selamectin treatment should prevent ear mite infestations.

Public Health Considerations

• On very rare occasions, people have been infested with ear mites. One report cited ear mites on the torso and extremities of the new owner of a cocker spaniel. In another report, six mites were recovered from crusts on a woman’s eardrum.

CANINE NASAL MITES: Species

Pneumonyssoides caninum lives in the nasal and paranasal sinuses of the dog. Infestation has been reported from the tropics and from Scandinavia, indicating that the geographic range of this species is probably worldwide.

Overview of Life Cycle

• Adult mites live on the dog, are nonburrowing, and feed on the keratin layer of the epidermis. Mites are very mobile and extremely contagious by direct contact.
• These mites have been found on fleas, lice, and flies; it has been hypothesized that this is one means by which they move between hosts.

Stages

• Stages include egg, larva, nymph, and adult. All stages occur within the sinuses.
• Adults are large (1-mm long) and visible to the naked eye. They have long legs that extend beyond the edges of the body, and their overall appearance is similar to that of the avian mites, Dermanyssus and Ornithonyssus.

Disease

• Heavy infestations or infestations in certain dogs can result in violent sneezing or epistaxis.
• Infestations are often diagnosed by chance.

Prevalence

• Infestations appear to be more common in areas after an initial case is discovered; examination of dogs by people expecting to find infestations often increases the numbers of cases identified.

Host Associations and Transmission Between Hosts

• This mite appears to be restricted to the dog.

Prepatent Period and Environmental Factors

• The prepatent period and environmental factors are unknown.

Site of Infection and Pathogenesis

• Mites are found in the nasal and paranasal sinuses.

Diagnosis

• Rhinoscopic examination often can reveal the mites crawling in the nasal cavity.
• Mites are also sometimes found in mucus or watery secretions from the nose or in mucus sneezed onto the examination table.

Treatment

• Cases have been treated with ivermectin (200 μg/kg).
• Selamectin is likely to have efficacy.

Control and Prevention

• Selamectin will probably prevent infestations with these parasites.

Public Health Considerations

• No human health hazard appears to be associated with these mites.

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