|Introduction....Life Cycle...Insecticides...Organophosphates...Pyrethrins...Insect Growth Regulators...Dessicants...Biologicals....Central Nervous System Modulators Flea Control|
Introduction: Fleas are external, blood-sucking parasites of dogs (and other canids), cats (and other felids), pigs, rodents, rabbits, people, birds. Ctenocephalides species infest dogs and cats, naturally, but can also jump on and bite other animals and people. Adult fleas bite the host animal, sucking blood and sometimes, transmitting diseases and/or other parasites (e.g. plague, cat scratch fever, peliosis (both from Bartonella henselae), human and cat/dog tapeworms, other worms, blood parasites (Hemobartonella felis). Bites are painful, cause local itching, produce intense discomfort and at times secondary infection (due to excessive self trauma from scratching) , especially in animals particularly sensitive (allergic) to flea saliva. Additionally, infestation of very young, small animals can result in severe anemia (from blood sucking)...and even death. The cat flea, Ctenocephalides felis, is believed to transmit the blood pathogen, Hemobartonella to cats.
|Life Cycle: The flea metamorphosis consists of a cycle of eggs to larvae to pupae to adult stages....more pictures of these are shown below...|
|Insecticides for Controlling Fleas: Insecticides are used in area sprays, dips, shampoos, spot-ons, oral and topical preparations, and flea collars whose purpose(s) is to manage fleas in companion animals by preventing, controlling and/or obliterating these nasty parasites. Classes of insecticides include organophosphates, carbamates, pyrethrins, insect growth regulators (IGR's) and insect development inhibitors (IDI's), dessicants, biologicals, and selective central nervous system (CNS) modulators. In some instances, products are formulated to enhance initial "knockdown" effect by quickly killing the egg stage, or by acting synergistically to enhance or prolong the initial insecticidal activity of the primary product. These classes of product are discussed separately:|
|Organophosphates & Carbamates: These insecticides affect fleas (and other ectoparasites) via preventing the natural degradation of the neurotransmitter (acetylcholine) at neural junctions (synapses). The result is persistent neurotransmitter-mediated neural stimulation, resulting in hyperactivity, respiratory paralysis (due to muscle exhaustion), convulsions and death. Unfortunately, the same mechanism of activity can also result in toxicity and death to animals. Since these insecticides can be absorbed through the skin under certain circumstances, they are potentially dangerous...especially in certain breeds of dogs (e.g. Whippet and Greyhounds) and to cats. In addition to the neurological mechanism of toxicity, excessive exposure to organophosphates in cats can lead to fatal, necrotizing pancreatitis. Organophosphates, in this author's opinion, should not be used on cats.
|Pyrethrins: Pyrethrins are botanical insecticides derived from plant material, particularly the plant Chrysanthemum cinerariaefolium. They also act on the nervous system, but are generally less toxic to animals than the organophosphate-carbamate insecticides. Their effect is also shorter lived than the latter. Synthetic pyrethrins are called pyrethroids, and are more potent than their natural counterparts. Both kinds of products are used in various topical and area/premises treatments
|Insect Growth Regulators/Insect Development Inhibitors: These act to inhibit the development of flea cycle at the larval or egg stages, respectively.. They do not kill adult fleas...their purpose is to control the population of fleas in the environment! Pupae are resistant to insect growth regulators.
|Biologicals: in preparation...|
|Central Nervous System Modulators: The current primary products in this category are fipronil(Frontline® , Frontline Plus®,Top Spot®), imidacloprid (Advantage®), Selamectin (Revolution®) and Spinosad (Comfortis®, Trifexis®). Frontline® and Advantage® work on the flea's (adult and larvae stages) central nervous system, but in slightly different manners. Fipronil affects the movement of chloride ions across sensitive nerve cells...essentially paralyzing these nerves. Imidacloprid interferes with the functionality of specific neurotransmitter receptors. By thus interfering with the signals between nerve cells and the essential functions they perform, the effect of either product is death of the adult flea. Frontline Plus® also contains an insect growth regular (IGR)...to prevent development of eggs into adult fleas. The chemicals used in these products are selectively toxic to fleas...not to animals. Revolution®, affects selected chloride ion movement across nerve and muscle cells of invertebrates, resulting in paralysis. It is applied similarly to the other two products but is absorbed systemically and is parasiticidal to a variety of internal and external parasites in this way (round worms and hook worms (cats only), mites; it is also inhibitory to the development of heartworm larvae to adults) in addition to killing adult fleas. Unlike plain Frontline®,or Advantage®, the product also inhibits development of the flea egg into adult fleas.
Much of the flea life cycle is spent off of the animal, as illustrated below (click the "Home" button).
Once the adult flea lands on a host animal, egg production begins 24-48 hours later. About 40-50 eggs per day are layed and fall off the animal into the environment almost immediately. Since reproduction occurs on the animal, control of reproduction on the animal is the first step in controlling the flea population on the premesis.
In general, eliminating viable eggs on the animal, which can occur with products such as Lufenuron, Selamectin and selected topical IGRs will control the adult population of fleas in the environment, though elimination of all adult fleas in this manner may take one or more months. Advantage® and Frontline®, in theory, kill adult fleas before the 24-48 hour post-infestation egg-laying begins; hence these should also control the environment. However, flea survival and reproduction do, on occasion, occur beyond 48 hours post-application with these products. Thus the addition of an topical IGR ovacide may also be efficaceous in halting reproduction and elimination of fleas from the environment
Efforts to decrease the number ofdeveloping eggs already present in the environment should also be considered. Fleas eggs are deposited wherever the animal moves. The greatest concentration is usually where the animal spends most of it time. Hence, blankets/bedding, sofas/chairs, carpets etc. should be washed/vaccumed frequently. Application of stong area insecticides and/or area IGRs can be considered when basic cleaning and animal flea control measures prove inadequate because the flea/developing flea populations are overwhelming.
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