Current Advice on Parasite Control:
Ectoparasites - Notoedric Mite
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.
- 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.
- 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.
- 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.
- 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.
- 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.