A flea is an insect with a wingless body that is flattened sideways. Ctenocephalides canis and Ctenocephalides felis are the fleas commonly found on dogs and only the adults are parasitic. They are usually found in areas frequented by the dog: it has been estimated that at any given time, only ten percent of the fleas present are in the dog's coat.
Fleas are quite prolific: the females lay many eggs (sometimes one or two thousand) within a few months. The eggs do not stick to the dog's coat, but fall to the ground and collect in rugs, wood floors, etc. Then they hatch and the larvae undergo metamorphosis, molt to become nymphs and when conditions are favorable, emerge as adults and become parasites on dogs, their definitive host. The adult flea pierces the dog's skin with its mouth parts and, after injecting some anticoagulant saliva, drinks the blood through its proboscis.
A dog and cat flea and its larva
The presence of fleas is revealed by their excrement: tiny black pellets found on the animal, particularly in the dorsal lumbar region. The pellets consist of blood eaten and digested by the fleas.
Fleas cause many diseases. First, they are a direct pathogen, although usually not a serious one, merely causing an itch. However, a dog can develop flea allergy dermatitis (FAD), causing significant pruritis that leads to hair loss and even sores from scratching, localized on the top of the body (especially in the lumbar region). This is less common in cold seasons when fleas are not as active.Their indirect pathogenic role consists of transmitting pathogenic agents: bacteria (including the bacterium responsible for bubonic plague in humans) and digestive-tract parasites (transmitted when adult fleas are ingested).
The Why and How of the War against Dog and Cat Fleas
To effectively combat a parasite, the pet owner must know how it develops so he can intervene in the various stages of development.
Larvae hide from the light. (In a house, this can be under rugs, cushions or skirting, between floorboards, in nooks and crannies, etc.) After one or two weeks of life, the larva changes to a cocoon, which is very resistant to flea treatments, and can survive this way for up to five months. The presence of animals or humans triggers the hatching of the adult from the cocoon. When a house has been inhabited for several months, a large number of cocoons can hatch all at once, leading to an infestation of fleas within a matter of hours. The adult then jumps onto (usually) a cat or dog and bites the animal so that it can eat the blood. The females are the most ravenous, able to eat fifteen times their own weight in blood (seventy females can eat one milliliter of blood per day!). If nature calls while a female flea is eating, the flea deposits "flea dirts"-small black pellets that can be found in the coat and become deep red when placed on wet paper.
In addition to siphoning off blood, fleas frequently cause allergies and can also transmit a flatworm to dogs and cats, a phenomenon often found in adult carnivores.
Most flea treatments applied to the animal (collars, sprays, powders) do limit the number of fleas, but are not sufficient to eliminate all of them because there are often a large number still lurking in the environment. Two treatments are usually recommended. The purpose of the first treatment, an insecticide, is to kill all the adult fleas on the dogs and cats living in the area to be treated. Antiparasitic sprays (pyrethroids) or "spot on" applications (direct application of very concentrated spray solution that then diffuses throughout the animal's body and kills the fleas as they eat) are used for this purpose. This treatment must be repeated every month. Another method attempts to sterilize the fleas as they eat. This treatment is administered by giving the dog a pill once a month. The second treatment attempts to kill the fleas (using an insecticide) or keep them from developing (by means of an insect growth regulator, or IGR) in the environment.
Insect growth regulators have the advantage of being completely harmless to domestic animals and humans. Before applying this treatment, the entire area must be dusted and thoroughly cleaned (remember that the vacuum cleaner, as well as the cupboard where it is kept, can become a haven for fleas). Surfaces are then treated with an insecticide and/or insect growth regulator. In good weather, it is sometimes necessary to treat the yard as well (only the shady places where the dogs and cats lie down, and the products used must be resistant to ultraviolet radiation). Many effective insecticides and insect growth regulators are available, each with its own advantages and limitations.
The results obtained are usually good, but depend on the way the treatments are applied and how often they are used.
Bruno POLACKDepartment of Parasitology, Mycology, and Parasitic and Fungal DiseasesEcole Nationale Vétérinaire, Alfort, France.
Ticks are very large acarids (from two to ten millimeters long) of the Ixodidae family. They display a significant sexual dimorphism: the female's abdomen can expand greatly, while the male's cannot. Their bodies are reddish-brown and flat, except after eating, when they are globular. They are intermittent parasites that live strictly on blood, except for the males of certain species, which do not eat at all.
The main species that is parasitic on dogs is Rhipicephalus sanguineus, the kennel tick, which is highly specific to its host. It attaches preferentially to dogs and only dogs, at all stages of life (larva, nymph, adult).Ticks attach to a dog's skin, preferring the most delicate areas. They use their mouth parts to pierce the skin and inject a special saliva, which solidifies into a very strong attachment point. The tick can then enjoy its meal of blood, after injecting more saliva with anticoagulant and vasodilating properties. Larvae, nymphs and unfertilized females take only small amount of blood, but fertilized females take large amounts (as much as several milliliters). While larvae, nymphs and adult females take only a single meal, the males eat very little but eat many times. Once the tick has finished its meal, another type of saliva is used to dissolve the attachment point so the tick can drop off. A free-living stage can follow the parasitic phase, depending on outside conditions.
A tick on a dog's skin
This free-living stage of the tick's life cycle is much longer than the parasitic stage. The kennel tick usually reproduces on its host, then the female gorges on blood and drops to the ground. After a few weeks, the female lays several thousand eggs and dies. Depending on environmental conditions, the eggs incubate for several weeks and then hatch. A larva emerges from each egg, climbs a blade of grass and waits for its future canine host to pass by. It attaches to the host and takes its first meal, lasting several days, then drops to the ground again. After a time on the ground, the larva molts and becomes a nymph. The same process occurs again: the nymph attaches to the host and eats, drops to the ground and molts to become an adult male or female. The complete cycle is quite long, considering that the tick must attach to three hosts: under less-than-ideal conditions, it can last up to four years. Furthermore, not all eggs reach adulthood, because they may be ingested at any stage of development by various animals, particularly during the free-living stage.
How to Destroy Ticks?
If the dog is not heavily infested, the ticks may be removed one at a time with tweezers, preferably after dropping a bit of ether on the tick or using a felt-tipped applicator impregnated with cypermethrin. A veterinarian has also designed a small hook that can be used to easily extract a tick without breaking off the mouth parts. In fact, removing the mouth parts is essential to prevent abscess formation at the point of attachment.
If the dog is heavily infested, it will have to be washed in lindane, pyrethroids, or amitraz, which all kill ticks. To avoid infestations in kennels or other animal populations, the floor and walls should be covered with cement, and an appropriate powdered insecticide should be used. A vaccine is also available, which is effective for six months and is designed to prevent parasite infections when a dog must frequent locations (e.g., forests) having a significant tick population.
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