Fleas: They are happiest at home - DVM
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Fleas: They are happiest at home

DVM InFocus

Lastly, in situations where the environment has numerous hatching pupae topical spot-on products may be overwhelmed. In treatment failures, I recommend increasing the monthly topical products to every two to three weeks. Sometimes we may add additional treatments including Capstar. This product has a very wide safety margin and can be used in puppies and kittens as young as 4 weeks old. Capstar is quite effective, but may only last one to two days after administration.

The environmental infestation with pre-adults is often the most overlooked portion of flea control. As mentioned previously, about 70 percent to 80 percent or more of the life cycle is hidden in the environment. The eggs, larvae and pupae are in the soil, grass, gardens and the home. In California and the arid West, immature stages perish in non-irrigated areas by mid-summer. However, they survive quite nicely in indoor environments such as carpeting, area rugs, pet bedding, cracks between hardwood floors, upholstered furniture (under cushions), and in carpeted hallways in common areas in apartments.

Since the pupal stages are virtually indestructible, they may continue to emerge over time (delayed emergence) and jump on pets even though proper adulticides are being used and the environment has been treated with insect growth regulators (IGRs such as methoprene or pyriproxifen). These IGRs are very helpful and will target and kill most of the larval and some of the egg stages, but not the coccoon stage. Stopping egg hatchability and interfering with larval molting blocks a big portion of the pre-adult life cycles.

In moderate to severe flea infestations or with "treatment failures," I recommend spraying the indoor environments with products that contain these IGRs. Knockout or Siphotrol brands are adequate. I prefer Knockout spray, because it tends to dry on contact and is less messy. These sprays are designed for indoor use only. They contain permethrins that may have ovicidal activity but mainly kill newly emerging fleas from cocoon stages for a quick "knock down" of adults. Sodium polyborate (Fleabusters) is effective in the home, and "dehydrates" larvae by desiccation. It is speculated that the larvae choke on the fine dust.

The outdoor environment can be treated with larvicidal sprays. I do not recommend malathion or diazinon because these chemicals are environmentally unsafe to other beneficial insects and wildlife. What we do recommend is a biological product that contains nematodes (Steinernema). These nematodes are natural and preferentially feed on parasitic larvae (fleas, cutworms, Japanese Beetles, etc.) and work quite well. They need some moisture periodically and may need to be replenished every few months.

In summary, with the arrival of the newer generation insecticides, the ability to apply the "monthly" spot-ons every two to three weeks, and the knowledge of the flea life cycle, clinicians should be able to better manage those difficult cases of flea-allergy dermatitis.

Dr. Vitale received his veterinary degree from Mississippi State University, College of Veterinary Medicine. He completed a residency in veterinary dermatology at the University of California, Davis and is a diplomate of the American College of Veterinary Dermatology. He is a clinical instructor/lecturer at UC-Davis and a staff dermatologist at East Bay Veterinary Specialists (formerly Encina Veterinary Hospital), Bay Area Veterinary Specialists and San Francisco Veterinary Specialists.


Source: DVM InFocus,
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