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Variety of producers help in ectoparasite control

Article

Dr. Patricia Payne reviews why it is essential for veterinarians to stay up-to-date on diagnosing and treating octoparasites.

Veterinary professionals now have their choice of an array of extremely safe and effective ectoparasite control products for their clients. After an ectoparasite problem has been diagnosed, these convenient and reasonably priced products will ensure client satisfaction and pet comfort. Veterinarians who continue to add their expertise to the diagnosis and treatment of ectoparasite infestations should be satisfied both professionally and financially.

Photo 1: Flea life cycle: Adult, egg, larva and pupa.

The parasites

Fleas:

Ctenocephalides felis, the cat flea is the most common ectoparasite of pets. This flea species has adapted and survives very well in most home environments. If unable to feed on their preferred hosts, cat fleas will also bite and feed on humans.

Ctenocephalides felis are tiny, holometobolic insects that have four life stages (Photo 1). The adult female flea will jump on a host, bite and start feeding within 10 minutes. Egg production begins within the first 24-48 hours. The small, pearly white eggs roll off of the host onto the carpet or ground. The 50-plus eggs laid per day by each female flea accumulate where the pet rests or sleeps but eggs may also be dispersed by the traveling pet. In three to five days, first instar larvae hatch from the eggs and start to feed on dried flea feces and other organic debris. Flea larvae tend to move away from light and down into the carpet or dirt. Flea larvae feed ravenously and molt twice before pupating. During pupation, the soft, multi-legged caterpillar-like flea larva completely changes into a laterally compressed hard-bodied adult insect. The pre-emerged adult flea may lay in wait in its silken cocoon for many days until an unsuspecting host passes by.

Ticks: There are four genera of three-host ixodid or hard ticks that infest our pets and homes. These include ambylomma, dermacentor, ixodes and rhipicephalus.

Photo 2: Tick larvae, three pair of legs.

The tick life cycle differs from that of the flea. Ticks are arachnids and are more closely related to mites and spiders than to fleas and lice. Ticks do not pupate; they molt from one life stage to another with little change in body form. Thousands of eggs are deposited in a single batch after the engorged adult female tick falls from the host into the environment.

After a month or longer, eggs hatch and the tiny tick larvae develop and wait for the appropriate host to pass by. Tick larvae have three pairs of legs (Photo 2, p. 23), nymphs (Photo 3, p. 23) and adults have four pair. Larvae usually prefer small rodents but in the case of Rhipicephalus sanguineus dogs or puppies will do. The larvae feed and move with their host until they are fully engorged and tumble off into the environment. Larvae then molt to nymphs and may remain dormant for varying lengths of time depending on species and environmental conditions. Nymphs find their preferred hosts, feed and fall once again into the environment where they molt to adults. The quest for a host by an adult tick becomes more complex as an intricate mix of attachment, aggregation and sexual pheromes come into play. Adult ticks feed and mate on their final host.

Photo 3: Tick nymph, four pair of legs.

Different genera and species of ticks have adapted this basic sequence of events and hosts to ensure survival in many geographical locations. Ixodes scapularis, the deer tick that transmits Lyme disease has a two-year life cycle. The adult female deposits eggs in the spring, larvae feed on mice and the nymphs quest for hosts the next spring. Rhipicephalus sp. ticks are very difficult to control in homes and kennels because larvae, nymphs and adults will feed on dogs and the environmental conditions are suitable for all life stages. These individual survival strategies have proven to be very effective both for the tick and the pathogens that they carry. Tick populations cause periodic infestations of people and their pets across most of the United States. Infestations of pets are dependant on the genus and species of tick, climatic conditions and the availability and prevalence of hosts.

The diagnosis

Fleas:

Flea combs may not be high-tech or expensive diagnostic instruments, but they are invaluable in their demonstrative capacity (Photo 4, p. 26). Adult fleas and flea dirt will line the edges of the comb and when placed on a white paper towel dampened with alcohol, most clients will actually be able to see the adult fleas and the bloodstain from the moistened flea dirt.

Ticks: The diagnosis of adult tick infestations is usually visually apparent. Infestations by nymphs may escape notice until they are fully engorged because of their small size.

The problems: Advertising campaigns have been successful in increasing public awareness of possible disease transmission from fleas and ticks to their pets and themselves.

Fleas: Flea allergy dermatitis is the most common cause of skin disease in dogs and cats. The new, highly effective insecticides have greatly reduced the recurrence and severity of this disease. Fleas also serve as an intermediate host for Dipylidium caninum, a common tapeworm of dogs and cats. Children have been infected with adults of this tapeworm by ingesting infected fleas. Cat fleas do not transmit Bubonic plague but do transmit Murine typhus (Rickettsia typhi). The causative agent of human cat scratch fever, Bartonella henselae, is spread among cats by fleas.

Table 1: species of ticks

Ticks: Ticks are extremely competent vectors of many diseases. Ticks are slow feeders, allowing time for disease transmission between host and parasite. Ticks transmit disease both trasnsovarialy (from adult tick to egg to larva) and also transstadially (from larva to nymph, nymph to adult). Ticks also disperse these disease agents while they feed and are transported into new environments (Table 1). Current research projects are beginning to elucidate the exact time necessary for disease transmission but the sooner a tick is detected and removed, the less likely disease agents will be passed. Multiple tick-borne diseases are the rule in both dogs and humans. The most common tick-borne disease in man in the United States is Lyme disease; the most lethal is Rocky Mountain spotted fever. The deadly tick borne disease Cytauxzoon felis, is passed by Dermacentor variabilis from the bobcat (Lynx rufus) reservoir host to the demise of domestic and exotic cats.

Control

The goals of professionally designed flea and tick control programs are to eliminate the current infestation and prevent reinfestation. The plans should include all pets and people (toddlers, immunocompromised) in the household. Armed with a complete history, that includes products used previously and what pets and people live in the household, the veterinarian will be able to make excellent recommendations. The veterinary practice may not be the only source of ectoparasite control products. Because there are many products to choose from and because not all pets need monthly flea and tick control, individualized risk factors for each household or kennel should be evaluated. The program should always be safe, effective and affordable.

Photo 4: Cats actually enjoy being combed for fleas. Flea feces and adult fleas are trapped and removed.

Fleas: Adult fleas may be combed from the animal with a fine tooth flea comb; eggs, larvae and pupae can be removed from the environment by washing the pet's bedding and vacuuming carpets (Photo 4). Outside projects to prevent wildlife (raccoons and opossums) from re-infesting the yard include repairing fences, trimming brush and removing any food sources, including pet food bowls, garbage cans and bird feeders.

Flea prevention and chemical control on pets

Environmental chemical control:

Thankfully this is usually not necessary today. Depending on your client, it may be best accomplished by a pest control operator (PCO) (Table 2).

Table 2: The products

If pet owners with occasional flea problems are concerned about the topical products leaving residual amounts of insecticide where the pet sleeps (personally I think this is a positive attribute of these products) you might suggest oral administration of nitenpyram as needed for control of adult fleas plus lufenuron for its ability to control flea reproduction. This combination of products should solve the problem and be extremely satisfying to your clients because you listened and valued their concerns.

Flea control can be as simple as one nitenpyram tablet after the weekly trip to the dog park during the short Maine summer. However, flea control can become more complex for pet owners in the Carolinas where fleas are present year round. Proper control could involve a combination of monthly topical applications of fipronil and methroprene, monthly administration of lufenuron and nitenpyram tablets every other day.

Tick prevention and chemical control on pets

Avoidance is an often overlooked but extremely successful strategy. Suggestions such as keeping the cat indoors, walking the dog only on cleared pathways and out of the woods during peak infestation times may be reasonable and very practical to some clients.

Table 3: Label Safety recommendations

Physical removal: There are many tick removal devices available but thumb forceps are what the author prefers. Whatever your preference is, make sure you demonstrate the proper technique to your clients. The removal of larvae and nymphs can be very challenging and may require sedation of the pet.

The next problem is what to do with the tick once it has been removed. It is very important that you advise your clients not to smash or burn fully engorged ticks because if there are disease agents inside the tick they will become aerosolized. Your clients also need to realize that all attempts to drown fully engorged ticks by flushing may not be successful. Submersion in 70 percent alcohol in a screw top vial or sealed baggie for 12 hours will kill ticks without endangering the owner.

Physical environmental control: An attempt to control rodents and wildlife (deer included) by destroying habitat and trapping will deprive the larval and nymphal stages of most tick species their preferred hosts. Keeping grass and brush cut short, fences repaired and removing possible food sources for wildlife are just a few suggestions that should accomplish this goal.

Environmental chemical control: The best choice for severe tick infestations is a PCO especially if Rhipi-cephalus sp. has infested the house or kennel or if the deer population has exploded in the backyard or neighborhood. An alternative for less severe infestations would a product containing cyflurin, which is available in several formulations at yard and garden shops.

Compliance: The first dose of any of the topical products should be applied to the pet with the owner present or at the very least a demonstration using a stuffed animal. There are many pitfalls in the application process despite valiant efforts of the marketing and packaging people to make the instructions clear. These include actually opening the tube (push down or remove cap and turn over to puncture) to allow the liquid to be placed on the pet. Some of the doses are very low volume (1¼4 ml) and may not be fully dispensed from the container or may be removed immediately by the owner's hand. Proper application is part of the professional service that you may easily provide to your clients that other sources of products cannot. This is a great opportunity for your staff to become involved in your newly designed flea and tick control programs.

Product safety

Make sure you are familiar with label recommendations (Table 3). Products available through veterinarians come with backing by the company only if they are used according to label directions. They also come with professional service hotlines and client Web sites. You should always check with the manufacturer or exotic medical specialists before advocating use of these products on exotic species such as rabbits, ferrets, birds or reptiles, and get client consent for any off label usage.

Suggested Reading

Permethrin is a common ingredient in over-the-counter ectoparasite products. Make a sincere effort to inform all of your cat owners that this synthetic pyrethroid is extremely toxic to cats, even if it is applied to dogs at the proper dosage level, cats have died from coming into contact with treated dogs.

Today's veterinarian is fortunate to have such a wide variety of extremely safe and highly effective products to choose from. Professionally designed flea and tick control programs will increase the cost to clients because the professional time invested should always be billed, but will benefit all concerned, the pet, the client and the veterinary practice.

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