The most common infectious disease in gerbils is Tyzzer's disease, a bacterial disease, which stress can make animals more susceptible to. It produces symptoms such as ruffled fur, lethargy, hunched posture, poor appetite, diarrhoea, and often death. It quickly spreads between gerbils in close contact.or other uses, see Gerbil (disambiguation) . A gerbil is a small mammal of the order Rodentia. Once known simply as  desert rats , the gerbil subfamily includes about 110 species of African, Indian, and Asian rodents, including sand rats and jirds, all of which are adapted to arid habitats.