At best, fleas are annoying blood-feeding insects that can irritate both humans and pets. At worst, they can carry diseases; fleas infesting rodents can infect humans with typhus and even plague, and the type commonly called the cat flea can spread a tapeworm that can infest dogs, cats and other domesticated animals as well as humans. If the human or animal bitten by a flea is allergic to flea saliva, severe itching, rashes or hives could result. Cold weather can kill many fleas if the cold snap is long enough and temperatures drop sufficiently, but winter may not completely eliminate a flea problem.
It's a Flea's Life
Fleas go through four distinct stages during their lives., according to the University of Kentucky College of Agriculture, Food and Environment.
- Eggs: Adult female fleas can lay as many as 50 eggs per day. The eggs are normally deposited on the host, such as a dog or cat upon which the flea is feeding. However, the eggs do not remain affixed to the pet's fur. Instead, they tend to fall off wherever the pet sleeps, sits, rests or walks.
- Larvae: Eggs hatch and turn into very small larvae that usually remain in or near the area where they hatched. These tiny "worms" can survive by feeding on the feces deposited by adult fleas in the immediate vicinity of the eggs.
- Pupae: The larvae encase themselves in a cocoon of silk-like material. The length of time this stage will last depends a great deal on the temperature and the availability of a nearby host; the pupae can detect the presence of a host by sensing movements and changes in the carbon dioxide levels. During the time spent in the cocoons, the larvae transform into adult fleas.
- Adults: Only adult fleas bite, and they emerge from their cocoons ready to find a meal of blood. A female flea will not begin laying eggs until approximately two days after she has her first blood meal.
Acceptable Environmental Conditions for Fleas
Although there are many different types of fleas, the most prevalent flea in the United States is Ctenocephalides felis, or cat flea. Despite its name, this is the flea most commonly found on dogs and wild animals, as well as cats. Different species of fleas prefer slightly different conditions, but the differences are not significant and have little relevance for United States pet and property owners battling an infestation of cat fleas.
Ideal conditions for cat fleas, according to the Texas A&M University's Veterinary Medicine and Biomedical Sciences, are temperatures between 70 and 80 degrees Fahrenheit and relative humidity between 70 and 80 percent. If the soil temperature rises above approximately 95 degrees or the humidity drops below 50 percent, many of the larvae will die.
During the winter months, if adult fleas can find a warm, sheltered location, such as in the fur of a host animal or an indoor location, they may survive the cold weather. However, cold can destroy the eggs and larvae. Cold weather can also destroy fleas that are in the pupal stage, but because the pupae can remain dormant for five months or more, some of them may survive the winter. Sustained temperatures below 30 degrees Fahrenheit, combined with low levels of humidity will kill all adults, eggs, larvae and pupae.
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