On-animal products Conducive environmental conditions

Public Health Significance of Urban Pests 167 Sustained release devices, such as flea collars, may provide long-term on-animal flea sup- pression. However, the active ingredient determines efficacy, and flea populations have been shown to be resistant to several active ingredients, including organophosphates, car- bamates and pyrethroids Bossard, Hinkle Rust, 1998. Products already available for cat flea control may also be useful in rodent flea control, with modifications of how the products are applied Davis, 1999; Metzger Rust, 2002. Because shed residues do persist in nesting materials, long-term efficacy could be obtai- ned in sylvatic rodents, as well as in peridomestic species McTier et al., 2000; Mehlhorn, Hansen Mencke, 2001.

5.7.4.2. Foggers

Aerosol foggers disperse pesticides on all horizontal surfaces, making them poorly adap- ted for flea suppression. Foggers cause unnecessary environmental contamination and do not distribute the pesticide under furnishings where flea larvae and pupae may be concentrated. Instead of using foggers, pet owners preferentially use other application methods Davis, Brownson Garcia, 1992.

5.7.4.3. General surface treatments

Household environmental treatments with flea adulticides have fallen out of favour, due to deposition of toxic chemicals on broad expanses of the living area and due to concern about airborne and dislodgeable residues Koehler Moye, 1995, so there are few products available for killing adult fleas. Instead, flea suppression depends primarily on larvicides. IGRs constitute critical components of effective flea IPM program- mes, but disodium octaborate tetrahydrate and other borate products have also been shown to be effective in eliminating larval fleas Rust Dryden, 1997. Borate products are broadcast in sites where larvae develop, brushed into the carpet and then vacuumed to remove loose residue; this results in adequate material being left behind to effect larval mortality as flea larvae graze on organic debris at the base of the carpet fibres Klotz et al., 1994.

5.7.4.4. IGRs

The use of IGRs is the preferred method of sup- pressing fleas, because it eliminates larval fleas before they reach the bloodsucking adult stage Fig. 5.2. Targeting larval flea habitats is critical to effec- tive management, so care should be taken to direct applications to areas where flea hosts spend most of their time – for example, by distributing IGRs around dog beds Rust Dryden, 1997. IGRs, such as methoprene and pyriproxyfen, are ineffective Fleas 166 Avoiding secondary poisoning of predators is critical to prevent rodent populations from resurging. Following any intervention, it is important to continue monitoring, to eva- luate programme effectiveness and to modify tactics for greater efficacy. Indoor flea infestations require thorough inspections. Any location where a flea-infested animal spends time will accumulate flea eggs, so examinations should include discussions with the pet owner about the animal’s habits, to ascertain likely infestation foci. Flea lar- vae can survive in uncarpeted areas by moving to protected sites under furniture or base- boards, so effective treatments must also target these areas. Increasing public concern about exposure to insecticides has caused the emphasis in urban entomology to shift towards non-chemical or reduced chemical pest control methods Hinkle, Rust Reierson, 1997. Strategies that focus on the host have superseded the historic environmental focus Rust, 2005.

5.7.4.1. On-animal products

Therapies that target the flea hosts essentially involve flea baits, using the host animal as a lure for adult fleas. Because all fleas feed exclusively on blood and must find a host to survive, treating potential hosts with toxicants ensures that fleas either fail to feed or attempt to feed and are killed. Rust 2005 provided an excellent overview of commer- cially available products that are applied to the host to suppress adult fleas. Currently, registered on-host products include avermectins, fipronil, imidacloprid, pyrethroids, pyrethrins and IGRs including insect developmental inhibitors and juvenile hormone analogues. In addition to suppressing adult fleas, on-host products provide an ancillary benefit by suppressing off-host life stages. Shed hair, dander and other debris from trea- ted animals carry sufficient insecticide residues to suppress flea larvae McTier et al., 2000; Mehlhorn, Hansen Mencke, 2001. Products administered orally include nitenpyram and lufenuron Rust, 2005. On-animal flea control products are prepared in a variety of forms, as topically applied spot-ons, pills, injectables, sprays, dusts, shampoos, mousses, dips and collars. Some active ingredients can be formulated in several ways, while some are delivered in only one way. Spot-on products are made to be lipophilic, so they passively distribute in the skin oils fol- lowing application. These products have gained pet-owner acceptance, due to their depen- dable efficacy, sustained effectiveness, low risk and ease of use Schenker et al., 2003. Products administered internally such as pills, liquids and injectables vary in their mode of action, including both flea adulticides and larvicides. Because fleas must feed on host blood to acquire these compounds, they should not be relied on as the exclusive means of flea control for animals allergic to fleas. Topical applications of sprays, dusts, shampoos, mousses and dips likewise vary in their effectiveness, depending on the active ingredient and its persistence in the animal’s hair coat. Most of these kill fleas initially, but may not offer prolonged control. Fig. 5.2. Indoor application of an IGR fores- talls development of immatures into biting adult fleas Source: Photo by N.C. Hinkle. Public Health Significance of Urban Pests 169 5.10. Conclusions 5.10.1. Surveillance and environmental design