Trombiculiasis is caused by the larvae of chiggers (eg, Eutrombicula alfreddugesi, Trombicula batatas, Trombicula autumnalis, Walchia americana) which usually parasitize rodents, birds, snakes and lizards in wooded areas. The adults live free in the environment and do not feed on animals.
Cats and dogs roaming through infested environments may acquire the parasitic larval forms which penetrate the skin. This problem is more prevalent in the late summer and fall. The bites of chigger mites are quite irritating and itchy, and most bites are on the head and feet.
The diagnosis may be suspected when pets roam through infested forests in late summer or fall and can be confirmed by finding the mites. Occasionally the larvae may be seen as orange dots but skin scrapings are often more helpful.
Treatment is not difficult as the larvae are susceptible to many insecticides and rarely persist in the skin although irritation from the bites may persist for several days.