The dark speck that suddenly appears when you walk across the carpet, then disappears, is likely a flea. It’s a bloodsucker, reddish-brown, about one-eighth of an inch long. Using a magnifying glass, you’d see the flea’s body is flattened from side-to-side and it has long claws on its legs – both are adaptations for traveling between hair shafts. The flea also has spines on its mouth, legs and back to help prevent it from being groomed off.

Nevertheless, a dog will probably pick off many of the cat fleas it hosts. Cat fleas (Ctenocephalides felis) are more common on cats, dogs and humans than dog fleas (Ctenocephalides canis) and human fleas (Pulex irritans). Each has its preferred hosts. The human flea prefers the blood of humans and pigs. Cat and dog fleas prefer cats and dogs, though children can become infested when pets sleep or rest on the same bed. Cat and dog fleas also will infest certain types of wild carnivores, including opossums and raccoons, but not squirrels, rats or mice. While these two species do not carry human diseases, they can carry tapeworms (Dipylidium caninum) that infect dogs.

Other flea species occasionally encountered by humans include the oriental rat flea (Xenopsylla cheopis) and the northern rat flea (Nosopsyllus fasciatus). These fleas live on Norway rats and roof rats, and are capable of transmitting plague and murine typhus to humans.

FLEAS AND DISEASE

Fleas often probe the skin before taking a blood meal. After 30 minutes, lines or clusters of itchy red marks appear. On sensitive persons, bites develop into raised bumps within 24 hours after being bitten.

Fleas have been associated with humans and other animals for thousands of years. A bacterium (Yersinia pestis) spread by fleas killed 25 million people, more than a quarter of the European population, in 14 th century Europe. This was the “black plague.” Epidemics also occurred in Egypt, Africa, China, India and even the U.S., before the discovery of antibiotics. All told, perhaps 200 million people have died of plague – more than have died in all the wars in history.

Today, plague occurs worldwide. Each year, a few cases of bubonic plague are recorded in the United States, mostly in the Southwest. The disease is typically carried by wild rodents, and transmitted to the fleas that bite them. The digestive system of an infected flea can become blocked by rapid reproduction of the bacteria, causing the flea to bite repeatedly in an attempt to avoid starvation. Humans typically contract the disease from the bites of infected fleas, or through skin abrasions that contact the blood of infected animals or the feces of infected fleas.

Bubonic plague occurs most often where persons live or participate in outdoor activities in close proximity to wild rodents, such as rock squirrels, ground squirrels, prairie dogs, chipmunks and rats. Pets also bring plague-infected fleas into the home. Cats are highly susceptible to the disease. Outbreaks can arise in urban and rural areas, especially where conditions are primitive or unsanitary.

Symptoms of bubonic plague develop within one week of exposure to the bacterium, and may include headache, fever, weakness, fatigue and painful, swollen lymph nodes known as “buboes.” The disease responds well to antibiotics, but untreated persons may die within a week of showing symptoms.

Another disease transmitted by fleas is murine typhus. In the United States, only a few cases are reported annually. These typically occur in Texas, or result from travel abroad, especially to tropical countries. Transmission of a bacterium (Rickettsia typhi) that causes murine typhus takes place in rat-infested areas, in the same manner as mentioned above for bubonic plague, and by inhalation of airborne flea feces. Headache, body aches, fever and, occasionally, a rash and other symptoms develop within two weeks after infection. Like plague, murine typhus responds well to treatment with antibiotics.

Content Resource : http://www.idph.state.il.us/envhealth/pcfleas.htm