Merck Manual

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Introduction to Rats


Katherine E. Quesenberry

, DVM, MPH, DABVP (Avian);

Kenneth R. Boschert

, DVM, DACLAM, Washington University

Last full review/revision Apr 2020 | Content last modified Apr 2020

Pet rats (scientific name Rattus norvegicus) originated from the Norway rat, found on the streets of cities and in the fields of rural areas. The Norway rat became domesticated in Victorian times and people began to selectively breed them for their fur and color. Rats have a long history in association with humans, although not always very pleasant. Some cultures regard rats benevolently; they are the first sign in the Chinese zodiac and are considered gods in some Indian religions. In Europe they were considered creatures of darkness, death, and disease because of the belief that they transmitted the plague. Today we know that it was not rats, but rather the fleas they harbored, that carried the infection.

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