Return of the plague
Plague can remain dormant for long periods if the rodent bearing the pathogen remains confined to its natural habitat. With the mixing of rodent species, the pathogen is transmitted to domestic rats, which passes it on to human beings. In Himachal Pradesh, the pathogen would have remained dormant if a person who had gone to the forest had not carried it back.
Rats can be divided into three major classes: commensal (domestic), pericommensal (semi-domestic) and sylvan (living in forest). The three main rodents involved in the spread of plague are Tatera indica, Bandicota bengalensis and Rattus rattus. There is little or no information about the involvement of other rodents in the spread of diseases.
Tatera indica is a large-sized rodent. Its hind legs are longer than the forelimbs. The head is large, with a longish muzzle. The tail is longer than the body, and there is a tassel of black hair at the end. This species prefers open spaces, and lives near crop fields and gardens. It is a gregarious eater.
Rattus rattus is also big bodied. The species has adapted itself to living with human beings. However, it is also present in open spaces, and is instrumental in spreading various diseases to human beings.
Bandicota bengalensis is more spiny and bristly than the house rat. Originally a field rodent, it is commensal today.