Fleas: Most Important Pet Pest

Although PCOs seem to have had fewer calls for flea control in recent years, these pests still cause problems for homeowners with dogs and cats. The Fifth International Symposium on Ectoparasites of Pets (ISEP) held in Fort Collins, Colo., last April explored the significance of fleas, ticks, lice, mites, mosquitoes and other ectoparasites and their associated veterinary conditions. This biennial conference brings together veterinary specialists (dermatologists, allergists, parasitologists, etc.), their entomological counterparts and industry representatives with varied backgrounds. The diversity of professions attending the symposium is indicative of the imaginative and creative avenues being pursued regarding pet ectoparasites. Although several diseases are transmitted to cats and dogs by ticks and other bloodsucking arthropods, fleas are still the major concern.

GENERAL THEMES. Three major themes emerged in presentations at the 1999 ISEP Conference. The first theme was that the economic significance and pest status of ectoparasite pests is growing. Second, researchers and pest management professionals need to better understand the biology, ecology (including parasite-host interactions) and behavior of ectoparasite pests. And finally, there is excitement concerning new control strategies being developed for companion animal ectoparasites.

As every PCO knows, the major dog and cat pests include fleas, ticks, mites, lice and bloodsucking flies. Because of their significance, fleas were the subject of most of the presentations. Changing demographics, with increases in both single-person households and urban dwellers, affect pet choices and concerns about ectoparasites. Consumers are demanding a different level of pest suppression on pampered indoor pets — a threshold level higher than on hunting dogs and barn cats.

Pet ectoparasites are important to veterinarians, medical-veterinary entomologists, urban entomologists and other specialists. Veterinarians approach ectoparasites from the pet health perspective. Entomologists focus on arthropods. They are interested not only in host-ectoparasite interactions, but also in the arthropod pest as a biological entity. Medical entomologists focus on pest effects on human health. Urban entomologists and pest professionals focus on these pests in the home as they affect human comfort. Insecticide manufacturers view pet ectoparasites as a control challenge, both on the animal and in off-host habitats.

DISEASE TRANSMISSION. Close contact between pet owners and their animals increases opportunities for humans to contract zoonoses — diseases shared by humans and animals. Emerging arthropod-borne diseases such as borrelioses, babesioses, ehrlichioses, dipylidiases, filariases, bartonelloses, etc., point out the significance of pets and their ectoparasites serving as bridges from wild reservoirs to humans. There is also the seldom-considered reverse situation of pets and their ectoparasites serving as reservoirs of disease organisms threatening endangered wildlife.

In addition to disease pathogens transmitted by ectoparasites, these arthropods are pests due merely to their presence. Ectoparasite infestations not only affect host health, they also affect the relationship between pets and their owners. Severe clinical manifestations of flea allergy dermatitis and mange are responsible for abandonment and death by euthanasia of thousands of animals annually. \

ON-HOST FLEA CONTROL. Flea control has shifted from being the purview of the pest control industry to being primarily a veterinary concern. Recently developed host-targeted insect growth regulators and new chemistries for adulticides have vastly increased efficacy of on-animal flea suppression. In fact, improved efficacy has increased the market for flea control — by some estimates tripling the veterinary market for flea suppression products.

Pet owners spend more than $2 billion annually nationwide for flea control. In some areas of the country, control of fleas and flea-related diseases accounts for more than half of the annual income of small animal veterinary clinics.

One veterinary product is Program (lufenuron). In addition to the "once a month" pill (or liquid in the case of cats), Program is also available as a 6-month feline injectable. Orally administered, lufenuron shows potential for flea control on wild hosts, some of which are potential plague reservoirs. Lufenuron does not kill adult fleas, but works by preventing flea eggs from hatching.

Two other flea control products, Advantage (imidacloprid) and Frontline (fipronil), are adulticides, providing kill of on-host fleas within 24 hours. These products are available in small tubes; a few drops are applied between the shoulder blades and distributed through skin oils to cover the entire body. Package directions indicate that Advantage should be applied monthly. Frontline claims up to three months activity against fleas, but has the additional feature of being effective against ticks. For tick suppression, Frontline should be used once per month.

Recent advances in flea control products and strategies result from ongoing commitment to research. New paradigms are emerging with respect to insect control; new chemistries, vaccines, natural products, traps and IPM strategies are shaping consumer perception and demand.

Development of effective topical and systemic flea control products has altered traditional practices. Fundamental goals of flea control, elimination of fleas on the pet and prevention of subsequent flea reinfestation have not changed, but methods of their achievement have.

People have very little tolerance for ectoparasites. Control and treatment strategies include both environmental and on-animal approaches. New compounds are being formulated to reduce human exposure and environmental contamination, with safer modes of action such as insect growth regulators, benzoylphenyl ureas, chloronicotinyls, phenylpyrazoles, avermectins and related compounds. Novel insecticides and modes of action, combined with new delivery systems, will make ectoparasite suppression more directly targeted than broad-spectrum pesticides. Together with new modes of action, new application technologies are being developed.

In the future we will see more specific and strategic tactics such as identifying vulnerable life stages and targeting multiple attack points. Niche treatments will be developed using environmentally friendly products. Companies are formulating products for maximal impact on pests with minimal environmental assault. Future research may yield vaccines for protection against fleas. Additional systemic, long-acting formulations may result from ongoing research, coupled with innovative delivery systems.

THE PCO’s ROLE IN FLEA CONTROL. It was apparent from these ISEP presentations that flea control has shifted away from the purview of PCOs and is now being oriented more toward veterinarians. The trend is moving away from environmental flea control to on-animal suppression. However, research illustrating the significance of wildlife and feral animals in supporting flea populations demonstrates that even with effective flea suppression on domestic animals, continual reinfestation can occur from these reservoirs. Considering this potential, the pest control operator’s value in flea suppression cannot be overlooked.

If the environment continues to produce fleas, pets will serve as attractants, harvesting environmental fleas. Both wild and feral animals serve as cat flea hosts. Wildlife reservoirs also provide reinfestation sources for our homes and our pets. If these animals continue to live in areas around residences with fleas, pets will continue to have fleas.

The PCO’s contribution to flea suppression therefore focuses on outdoor flea reservoirs, and the most significant activities involve exclusion and source reduction. Because the recurrent flea sources are wild and feral mammals, access prevention will reduce reinfestation potential.

Frequently, wild animals — such as raccoons, opossums, feral dogs and cats — will take temporary refuge in outbuildings, crawlspaces, attics and other secluded areas around homes. They bring with them their fleas, leaving an infestation behind when they depart. Newly emerged, hungry fleas can travel long distances seeking a host, crawling up through cracks in the floors to infest living quarters. So, elimination of potential nesting sites by building out alternative hosts is a priority. Access to attics and crawlspaces should be closed or screened to prevent animals from producing their litters there.

Once infestation occurs, results from attempted insecticide control are seldom satisfactory. Pupating fleas are protected from insecticide exposure and emerging fleas rapidly move away from the treated area, rarely encountering adequate residual to kill them. While spraying under a house may reduce the numbers of fleas that find their way up through the floorboards, it is much less effective than preventing flea production under the structure.

PCOs continue to play a role in flea IPM, but the role has shifted away from applying pesticides toward proactive prevention. PCOs have the knowledge to identify potential flea problems and to make recommendations for rectifying conducive conditions.

The author is a veterinary entomologist with the University of California, Riverside, Calif.

WANT MORE INFORMATION?

Copies of proceedings of the 4th International Symposium on Ectoparasites of Pets and proceedings of the 5th International Symposium on Ectoparasites of Pets are available for $25 each (covers postage and handling). Please send a check made out to "University of California Regents" to Dr. N.C. Hinkle, Department of Entomology, University of California, Riverside, CA 92521. Please indicate which volume you wish to purchase.