The agonizing itch

Apr 14, 2008 15:33 GMT  ·  By

No, toads do not cause warts (they are produced by viruses), nor scab, which is caused by a mite. But pet animals, like dogs and cats can transmit this parasite.

Scabies is caused by the scab mite (Sarcoptes scabiei variety hominis), 0.3 to 0.9 mm long, which lives on the surface of the skin or beneath, feeding on dead, desquamated cells. The female digs galleries into the skin, where she lays her eggs, using her mouthparts and special cutting surfaces on the front legs, in just 25-60 minutes. The female lays 2-3 eggs daily for 2 months. The larvae hatch 3 to 10 days later and they dig their way to the surface of the skin where they moult into nymphae which inhabit the hair follicles, and then mature. The adult scabs live 3-4 weeks on the skin of the host. The female matures in 17 days, after two moults, and the male in 9-11 days, after just one moult (the female doubles the male in size).

The symptoms of scabies appear when the females penetrate the skin. Often, red thin lines emerge between the fingers (the preferred areas are the wrist and hand, but all body parts can be attacked). After a while, red, irritating eruptions emerge on the body. Except the head, the eruptions may cover the whole body, being more frequent on elbows, soles and ankles.

The eruptions cause intense itch, and the patient scratches often, especially when the skin gets heated, resulting in severe bacterial infections. The itch is caused by a strong allergic reaction caused by the moving of the female mites in the skin and the presence of the eggs. Scabies can be easily treated with ointments, but because it is a transmissible disease, all the persons who came in contact with the patient must be treated.

In fact, most patients do not have more than 12 mites at a time, but this is enough to turn their lives in a nightmare.

The first to prove scabies was caused by a small animal was the Italian biologist Diacinto Cestoni in the 18th century.

Other strains of this species infest domestic animals, from dogs to pigs and goats.