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Veterinary Forum May 2007 (Vol 24, No 5)

Clinical Report: "Fleas — The Tiny Pests Live On"

by Sophia Yin, DVM, MS (Animal Science)

    In 1995, a tiny predator with a ravenous appetite for blood and a phenomenal capability for reproducing - the flea - finally met its match when lufenuron was introduced onto the market. This systemic product was given monthly and prevented flea eggs from hatching, thus halting the mad cycle of reproduction. It was followed shortly with other topical and systemic residual compounds, such as fipronil, imidacloprid and selamectin.

    These insecticides, along with potent, long-lasting insect growth regulators, such as methoprene and pyriproxyfen, had the potential to turn household flea infestations into a problem of the past. The products worked either by killing the adult fleas before eggs were produced or killing developing larvae before they could mature.

    That was then, this Is now

    With the advent of these new wonder products, clients no longer needed to laboriously shampoo and dip their pets weekly and repeatedly treat the house and yard. With these powerful monthly treatments, veterinarians thought the flea to be a pest of the past. And with the subsequent sale of such products through nonveterinary consumer outlets, everyone believed pet owners would no longer need veterinarians to help them combat the tiny blood-sucking assailant. But now, more than a decade later, it is turning out that neither prediction is true.

    According to Carlo Vitali, DVM, DACVD, a dermatologist at San Francisco Veterinary Specialists, "Fleas are still the most common cause of skin allergy in private practice. Even in my specialty practice, I see eight to 10 cases a week. It's second only to atopic dermatitis. The most common reason for flea infestation or its associated allergy issue is not product failure,"Dr. Vitali adds, "but lack of client knowledge about flea biology, along with the problem of how and which parasiticides to use."

    Michael Dryden, DVM, PhD, professor of veterinary parasitology at Kansas State University, agrees: "When I lecture at conferences and ask practitioners how many had client handouts on flea biology before 1995, about 70% to 80% of practitioners raise their hand. When I ask how many provided handouts today, only one or two raise their hand. Therein lies the problem: We have forgotten our primary responsibility to provide client education."

    One consequence is that clients are largely misinformed about how their pets get fleas. "They still think pets get fleas directly from another dog or cat and that the fleas jump off the other dog and cat and lay eggs in cracks and crevices," says Dryden. So when they find fleas, they may blame other animals their pet has recently come into contact with or even their recent visit to the veterinarian.

    "Clients need to understand that the fleas they see on their pet are from eggs that were deposited in the environment 4 to 8 weeks ago," Dryden stresses. In addition, clients do not realize that fleas can remain in their cocoons until survival conditions are favorable. So a pet may leave the household for days to weeks, and when it returns, the fleas emerge from their cocoons and infest it.

    A second consequence of misinformation and lack of client education is when clients purchase flea products and their unrealistic expectations are not met. "They treat the animal and wonder why the fleas are not gone the next day because they don't understand that eggs, larvae, pupae and newly emerging fleas are in the environment," adds Dryden. Clients think the product has failed or the pet's pruritus is from other causes.

    Implementing workable flea control

    Modern monthly topical and systemic treatments kill the adult fleas on the pet or prevent newly laid eggs from hatching. However, the eggs that are already in the environment will continue to hatch, leading to larvae that develop into pupae and then later emerging as ravenous fleas. After the fleas find their host, they begin to suffer the toxic effects of the insecticides and the cycle winds down. This lag period between initial insecticide application and destruction of the entire flea population in the pet's household environment is called the developmental period. It may last up to 3 months.

    According to Dryden, "Veterinarians can help pet owners with flea-infested pets by implementing a safe and successful flea control program. In doing so, veterinarians must consider issues of flea biology, the environment, the host, insecticide efficacy and safety and pet owner concerns. Educating the pet owner, especially as to the concept of the developmental window, can help ensure client satisfaction."

    NEXT: Diagnostic Dilemma: "Feline Intestinal Hemangiosarcoma"


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