What are Fleas?
Fleas are tiny, wingless, parasitic insects that feed on a wide variety of warm-blooded animals, including humans. Fleas have laterally flattened bodies (in other words, they're taller than they are wide), and are about the size of a pin head, on average. They have specially-adapted, piercing-sucking mouthparts with which they puncture the skin of their hosts. Most flea species are named after their preferred host, such as dog fleas, cat fleas, human fleas, and so forth. But if their preferred host isn't available, fleas will simply infest another animal instead. Pretty much any warm-blooded animal will do in a pinch if a flea gets hungry enough. Adult fleas have well-developed legs and can jump quite high. They use this ability to jump onto a host animal's body after having fallen or having been shaken off the body of another host. In fact, fleas spend quite a bit of their time jumping onto and falling off of their hosts, which is one way they spread through homes. Fleas hitchhike on pets (and sometimes humans), and get transported throughout the house.
Flea Life Cycle
Fleas develop by complete metamorphosis. The entire developmental cycle from egg to adult can occur in as little as two weeks under ideal conditions, but usually takes a bit longer. Adult females usually deposit their eggs loosely in the hair or fur of a suitable host or in its lair. The eggs hatch into the first of three legless, eyeless larval stages. The larvae have chewing mouthparts and thrive on the feces of adult fleas, although they will eat virtually any kind of
organic matter. After completing the nymphal stage of their development, fleas pupate in silken cocoons until stimulated to emerge by an event in their environment that tells them that there is a suitable host nearby, such as vibration as the animal walks past. If no stimulus occurs, the flea can remain in a dormancy-like state inside the cocoon for many months. Adult fleas feed solely on blood, but they can survive for months between meals if no host is
available. Females must consume at least one blood meal, however, before they can lay eggs.
Fleas and Disease
Fleas are significant public health pests of humans, domestic animals, and livestock. Consider the following:
- Fleas are required vectors of Yersinia pestis, the bacterium that causes bubonic plague. During the fourteenth century A.D., plague killed perhaps as many as one-quarter of the world's known population. Fleas transmit the plague bacterium from rats to humans. Human cases of plague in the United States still occur, especially in the Southwest part of the country.
- Fleas are vectors of murine typhus, a rickettsial disease that is still common in less-developed nations where sanitation and pest control are lacking.
- Flea bites can cause a serious rash known as "fleabite dermatitis."
- Fleas carry an intermediate stage of stage of Dipylidium caninum (more commonly known as tapeworms) which can infest humans who accidentally ingest infected fleas. The importance of fleas as disease vectors and the difficulty of treating flea problems makes flea control one of the more important and challenging jobs in pest control.