Max's House

Parasites - External


External Parasites

Fleas are without question the most significant external parasites
afflicting cats. Fleas can cause life-endangering anemia, particularly
in severely infested kittens, and host one of the major tapeworms
that infect cats.  Fleas can also transmit plague, a potentially fatal
infection caused by the bacteria Yersinia pestis, most cornmonly
from infected rodents and rabbits to cats and humans. Rarely, fleas
transmit the disease from cat to cat or from cats to other species,
including humans and dogs. Although plague is not common in cats,
numbers of feline cases as well as cat-associated human cases, have
been on the rise since  1977 in the western United States. 
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But as far as the cat is concerned, probably the most bothersome problem  associated with fleas is flea-bite hypersensitivity, an allergic reaction to flea  saliva.  For the unfortunate cat that suffers from this disorder, Just a few  flea bites are often enough to cause a severe skin reaction. Common signs of flea-bite hypersensitivity are itchy skin, scabby bumps and hair loss-but these signs are not always exhibited, and other diseases can have the same symptoms. The only solution for such cats is
to prevent fleas from coming near them. This is usually a simple matter if your only pets are cats-keep them indoors-but can be a difficult task for many households with dogs.   Anti-inflarnmatory medications can be very helpful, but they are not a cure. They must be given as long as the cat is exposed to fleas, and they can sometimes produce harmful side effects when used long-term.

By parting the fur, you may be able to see these small brownish, wingless insects running about. If the infestation a s fairly light, fleas may be impossible to spot oil the coat, but flea dirt (droppings)-which looks like tiny black pepper flakes-confirms their presence. To find flea dirt, thoroughly comb the coat with a flea comb and look for black flecks entrapped in the teeth of the comb. If you can't tell if the black material is flea dirt or just debris, take a fleck or two and place it on a damp paper towel; if' a red halo forms around the fleck, it is flea dirt.

To control flea infestation, you must treat the environment as well as all the animals in the household. There are many safe, effective, and easily adininistered flea products available from veterinarian Convenient monthly treatments given orally or applied to a small area of' the sk' n are a boon to pet owners because they eliminate fleas not only from their pets for a month at a time but from the indoor environment as well. This is especially important in households where family members (often children) have an allergic reaction to flea bites.

Make certain that any over-the-counter products you use are labeled specifically for rise in cats, as some dog products may not be safe for cats, and follow the directions carefully. Never apply a flea product unless you can monitor the cat closely for at least several hours after administration and do not use more than one product at a time.

Ticks are small parasites that bury their heads in the skin of' their hosts and stick blood  until they look like fat, gray or brown beans. When the ticks can't hold any more blood, they fall off the host and lay thousands of eggs. Heavy tick infestations, rare in cats, can cause anemia as well as skin irritations and infections.  Cats may be parasitized by hard ticks of the family Ixodidae. These ectoparasites which feed only on the blood of their hosts are arthropods, closely related to scorpions, spiders and mites.  Ticks have a great  potential to act as vectors of protozoa, fungi, bacteria, viruses, rickettsiae, filarial nematodes and spirochetes.  Hard ticks have four life stages: egg, larva, nymph, and adult. Larvae and nymphs must feed to repletion prior to detaching and molting. As adult female ticks engorge, they may increase their weight by more than 100 fold and after detachment may lay thousands of eggs. Tick-photo.jpg (31919 bytes)

Pathogens may be acquired when ticks feed on infected reservoir hosts (often rodents and small feral mammals). In some cases transovarial transmission of pathogens occurs and infected eggs will hatch and produce infected larvae. The greatest potential for systemic disease occurs when infections acquired in early life stages are transmitted to new hosts when the next stage feeds. Transmission of pathogens and toxins often requires periods of attachment from hours to days and the essentially painless bite of ticks allows feeding times of adequate duration.

Ticks should be removed as soon as possible to limit time available for neurotoxin or pathogen transmission. Most efficient removal is accomplished with fine pointed tweezers. Ticks are grasped close to the skin and gently pulled free. Species with short, strong mouth parts (e.g., Dermacentor) usually pull free with host skin attached; species with long, fragile mouth parts (e.g., Ixodes) often leave fragments embedded in the feeding cavity. In either case, washing with soap and water is generally sufficient to prevent local inflammation of secondary infection

Tick avoidance requires avoiding environments that harbor ticks. Because ticks may survive on many intermediate hosts, and because suburban living has brought pets into environments frequented by these intermediate hosts, avoidance may be difficult for all but pets kept strictly indoors or for city dwellers.

Other external parasites that can cause skin disease in cats are several
species of Cheyletiella mites (large, oval, blimplike parasites visible
as small white specks that cause an itchy skin disease known as cheyletiellosis, or "walking dandruff ", plus a number of other species of mites and lice (small, flat, wingless biting parasites that cause itchiness, hair loss, and dandruff). Correct diagnosis and treatment ensure successful management of
problerns from external parasites.

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Ear mites
Otodectes cynotis are large, white, free-moving psoroptid mites that causes otoacariasis. These are highly transmissible mites that live on the surface of the epithelial lining of the ear canal, or less frequently on the skin surface. Otodectic mites lack specificity among carnivore host species and are responsible for approximately 10% of otitis in dogs and 50% in cats (Griffin, 1993). The incidence may actually be higher than this because otitis may be produced by low numbers of mites that could go undetected on examination. In addition, mites will often leave the ear canal if severe inflammation or a purulent bacterial or yeast infection develops.

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The life cycle is completed in 3 weeks and is initiated with the laying of an egg, which is cemented to a substrate. After 4 days, the egg hatches into a six-legged larva that develops into an eight-legged protonymph in 3 to 10 days. After 3 to 5 days, the protonymph molts into the deutonymph. After an additional 3 to 5 days, the deutonymph becomes attached, end to end, with an adult male. if a male adult is produced from the deutonymph, the attachment has no significance. However, if a female is produced, she must be fertilized at the moment of ecydysis or she will not be able to produce eggs.

 Mites feed on lymph and blood, thereby exposing the host to mite antigens. This may allow the host to become sensitized to mites with the production of immunoglubulin E (IgE) reaginic antibodies. This sensitization can be demonstrated in 87% of random source cats, which will have immediate wheal and flare response to mite antigens. Probably, almost all cats are exposed to small numbers of mites early in life, with the majority developing immune responses that create an aural environment that is not suitable for mite colonization and clinical disease. Other cats may have ineffective immune responses that allow mites to colonize and produce clinical disease.

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