Flea Bites

A flea bite is the resulting injury from a flea sting, which could produce a local inflammatory reaction, or after an incubation period, a flea-borne disease, such as plague, endemic typhus fever, dipylidiasis, and hymenolepiasis, among others, but most species of flea do not transmit pathogens.

Fleas belong (taxonomically) to the order Siphonapetra, with two important families for human and animal health: Pulicidae and Tungidae. The above-men-tioned diseases are transmitted by members of family Pulicidae (Pulex, Ctenocephalides, and Xenopsylla).

In history, Xenopsylla cheopis represented the most important vector of an ancient disease previously known as the Black Death (plague), one of the worst natural disasters in history. Plague or Black Death is an infection of rodents caused by Yersinia pestis and accidentally transmitted to humans by the bite of infected fleas. Plague has three forms: bubonic plague (infection of the lymph glands), septicemia plague (infection of the blood), and pneumonic plague (infection of the lungs). Pneumonic plague can spread from person to person. Fortunately, this disease is treatable with antibiotics if detected early. Prevention consists of controlling rodent fleas, educating the public and the medical community in places where plague occurs, and using preventive medicines and vaccines as appropriate.

Endemic typhus fever or typhus (also called flea-borne typhus and murine typhus) is a disease caused by small bacteria called Rickettsia. Dipylidiasis is a common tapeworm infection of dogs and cats caused by Dipylidium caninum. Arthropods serve as intermediate hosts for this parasite, including then the fleas which include the dog flea (Ctenocephalides canis), the cat flea (C. felis), and the dog louse (Trichodectes canis). The risk to human beings to acquire this disease is low, because this occurs by ingestion of arthropod intermediate hosts which harbor the cysticercoid larvae. The hymenolepiasis, caused by the dwarf tapeworm or Hymenolepis nana, is the most common tapeworm infection diagnosed in the world. Although it is not the most common form of transmission, fleas could vectorize this disease in animals and may be in humans. People get infected by accidentally ingesting tapeworm eggs, by ingesting fecally contaminated foods and water, by touching the mouth with contaminated fingers, or by ingesting contaminated soil.

Another important infection directly caused by fleas is the tungiasis which is a common health problem in economically depressed communities in South American and sub-Saharan African countries, [Page 668]but it should be considered in the increasing number of international travelers to tropical destinations. The causative ectoparasite, Tunga penetrans (a flea of approximately 1 millimeter of size), penetrates into the skin of its host, undergoes a peculiar hypertrophy, expels several hundred eggs for a period of less than three weeks, and eventually dies. Besides the human, this flea could infect cattle, sheep, and horses.