Facts about fleas

StoryImage( ‘/Images/Story//Auto-img-113217266115297.jpg’, ‘Photo by Dr. RObert A. Hedeen’, ‘The Oriental rat flea may attack humans and transmit serious disease (Photomicrograph, times 25).’);

There is no doubt about it, the champion jumpers in the animal kingdom are the fleas. A flea that commonly infests humans can jump 8 inches vertically and about 13 inches horizontally, and this translates into about 150 times its own length along the ground and 100 times its own length into the air. Crickets, grasshoppers and kangaroos are obviously not in the same league with a flea.

Mathematically-inclined entomologists have determined that if a man could perform the same feats in proportion to his body size, he could broad jump 700 feet and high jump 450 feet. In the face of these figures; Olympic records seem trivial.

Fleas not only avoid capture by employing their jumping abilities, but their bodies are flattened from side to side and relatively smooth, which enables them to slip easily through one’s fingers. They are highly specialized insects without wings and a minute head. They are, however, admirably adapted for moving about freely among the hair and feathers of the animals upon which they live. All fleas are ectoparasitic blood-suckers.

Almost without exception, all terrestrial mammals are attacked by one species of flea or another, and many birds play host to these obnoxious insects (more than 2,000 different species have been described worldwide). In some cases, one species of flea infests one specific type of animal, but usually they are quite cosmopolitan and will set up housekeeping on any number of reluctant hosts. The human, dog, cat, and rat fleas are the most important to people. All four species readily attack man as well as other warm-blooded animals.

These common fleas are reddish-brown in color and are most active at night. The adults live on the body of the host where they routinely bite and imbibe blood. Mating occurs on the host, and the fertilized female then drops off to deposit her eggs in cracks and crevices or in the bedding of the animal. The larvae are legless and eyeless and appear to be quite helpless. Nevertheless, they always seem to find enough food among dust particles and bits of organic matter to grow to maturity.

Fleas are important not only because of their bites, but as vectors of disease organisms from one animal to another. The so-called Oriental rat flea is found worldwide and is the most important species as it is a transmitter of bubonic plague or Black Death and murine or endemic typhus fever. A rodent infected with one of the diseases will die.

As the body of the dead rodent cools, its fleas start looking for another home. If a human is in the vicinity, the flea will leap from the dead rodent to a person, adopting him as their new host and food source and passing on the infectious disease agents.

In the not-too-distant past, plague and endemic (murine) typhus (not to be confused with epidemic typhus fever that is transmitted to man by the body louse) were routinely encountered in various sections of the United States, but today these diseases are quite rare in this country due to modern, scientific flea and rodent control methods.

Pet owners, however, should be aware that the fleas infesting our canine and feline friends frequently harbor the infective stage of the dog and cat tapeworm. If a person happens to swallow an infected flea, the tapeworm will develop in the intestine. The dog and cat tapeworm is not transmitted by the bite of a flea.

Children (and some adults I have known) should never kiss their pets or in other ways bring their mouths in close contact with the animal. Better yet, get rid of the bloodsuckers that annoy a pet to no end with one of the effective anti-flea products on the market.

Fleas are all about us but frequently go unnoticed because of their small size and secretive habits. Many years ago, Jonathan Swift summed up the situation when he wrote:

“So, naturalists observe a flea, Hath smaller fleas that on him prey;

“And these have smaller fleas still to bite ‘em, and so proceed ad infinitum.”

Dr. Robert Hedeen is a former resident of Maryland’s eastern shore and resided in the Chicago area from 1960 to 1971. He is a retired professor emeritus of biological sciences in the University of Maryland system. He has published more than 30 scientific papers, has written numerous magazine articles, and is the author of two books on the natural history of the Chesapeake Bay.

From the Nov. 16-22, 2005, issue

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