MORBIDITY: +

MORTALITY: +

ETIOLOGY: PARASITIC

Scabies is caused by Sarcoptes scabiei. Animals and people are infested by their own subspecies of S. scabiei, which prefer to live on a specific type of host animal. Human scabies is caused by S. scabiei var. hominis. Some of the other sarcoptic mites that can be found on other animals, and temporarily on people, are S. scabiei var. canis (dogs), S. scabiei var. bovis (cattle), S. scabiei var. equi (horses), S. scabiei var. caprae (goats), and S. scabiei var. suis (pigs).

A different mite, Notoedres cati, causes a disease similar to scabies in cats. This mite may also temporarily infest humans or other animals.

S. scabiei females make tiny burrows into the skin in which to lay their eggs. After about 3 weeks the eggs hatch, and the immature mites come to the opening of the burrow, mature, mate, and move on to make other burrows (Figure 36). The presence of the mites, mite eggs, and mite waste materials causes an allergic reaction in the host, which results in intense itching. Tiny red blisters or bumps develop on the skin, which is also inflamed.

FIGURE 36 Scabies.

It is while the adult mites are on the skin, rather than in the burrows, that they can be transferred to other animals or people. From a zoonotic standpoint, it is also at this time that the mites may be transferred to an atypical host, such as a person. The mites make their burrows, and the atypical host has an allergic reaction, but the mites die in a couple of days, and the itching goes away.

N. cati has a similar life cycle, but it is the immature mites that are transferred to other animals or people.