Parasites are those small organisms that benefit from and live off of a host — for our purposes this means your dog or cat. Some parasites are external, living on the skin or hair and some are internal, inhabiting the host’s body tissues. The most common external parasites we deal with are the flea and tick. Lice are also included in this category.

Fleas
Fleas spend most of their adult life on the pet itself but develop off the pet in the surrounding environment. This can be inside the home or outside in the yard. Adult female fleas lay their eggs on the hair shafts of the pet. Once the sticky coating dries, the eggs fall off. Depending upon the environmental conditions, the eggs hatch within four to 10 days into the larval stage. The larvae feed on flea feces in the area, which have also fallen off the pet.

The larvae pass through two molts in a two-week period and then begin to spin cocoons. Adults emerge from the cocoons in three to four weeks. Female fleas usually hatch first and find another host as soon as possible to start the cycle all over again. Because they reproduce rather rapidly, it only takes a few fleas in the beginning to create hundreds or thousands in new generations.

Fleas live in most areas of the United States, with the exception of arid areas of the southwest and areas at high altitudes. They thrive in warmth and humidity and normally emerge in early to mid-summer and stay until fall. Cool temperatures with low humidity, especially subfreezing conditions, will kill fleas. In southern areas of the country fleas live year-round but in northern areas they die off after one or two hard frosts. In favorable conditions (cool temperatures, high humidity), fleas have the ability to hibernate when no food is available. They may wait in a house for several days or even weeks when pets and their owners are away. When hungry enough, fleas will bite people in the absence of pets. Even in northern areas, fleas can live year-round in a home environment.

Ticks
Ticks are also blood-sucking parasites. They can also transmit a number of diseases to humans and pets. Ticks have long mouth parts that bury tightly into the skin but they do not actually put their heads under the skin (a common misconception). The bite can be painful and often becomes reddened and inflamed. This is due in part to the chemicals they release into the skin.

Female ticks are larger than males and are usually the ones found feeding on a dog or cat. They must have blood meal to be fertile and lay eggs. Diseases are passed over a period of time and depending on the disease, the sooner ticks are removed the less the chance of a host contracting a disease.
Female ticks lay clutches of eggs (approximately 2,000–4,000 eggs) in crevices, grassy areas, small bushes or a suitable indoor area. Young larval ticks (who have six legs) feed on the host pet for a few days, then drop off and molt into nymphs. Nymphs (eight legs as in adults) again find a host and feed for about a week. They also drop off and molt once again into the final adult stage. The whole cycle takes two–three months (some species take longer). Unfed adults may survive for over a year.

Attached ticks should be removed from a pet with tweezers by grasping the tick close to the skin pulling back. Do not crush adult ticks as eggs can be released into the environment from the female. Treat pets and the environment (house and yard) with an approved parasiticide. Birds and mice commonly carry ticks and may infest your yard. When egg cases hatch, your pet may pick up several dozen ticks by walking through a nest in the yard. Though shampoos and dips will help kill many, some will need to be removed by hand.

Treatment
In the last few years, big advances in pesticides that control fleas and/or ticks have been made. Frontline, Top Spot and Advantage are the three brands considered to be most effective. They are all sold through veterinarians. Advantage does not kill ticks. Several oral administrations combining heartworm prevention and topical parasite control are also available. Talk to your veterinarian for more information about which of these products is best for your pet.

This article is provided as a general overview of the topic. Always consult your veterinarian for specific information related to diseases or medical care for pets.

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