Norway Rat (Brown Rat)
The brown rat, common rat, street rat, sewer rat, Hanover rat, Norway rat, brown Norway rat, Norwegian rat, or wharf rat (Rattus norvegicus) is one of the best known and most common rats.
One of the largest muroids, it is a brown or grey rodent with a body up to 10 in long, and a similar tail length; the male weighs on average 12 oz and the female 9 oz. Thought to have originated in northern China, this rodent has now spread to all continents except Antarctica, and is the dominant rat in Europe and much of North America—making it by at least this particular definition the most “successful” mammal on the planet after humans. Indeed, with rare exceptions, the brown rat lives wherever humans live, particularly in urban areas.
Similar to other rodents, brown rats may carry a number of pathogens, which can result in disease, including Weil’s disease, rat bite fever, cryptosporidiosis, viral hemorrhagic fever, Q fever and hantavirus pulmonary syndrome. In the United Kingdom, brown rats are an important reservoir for Coxiella burnetii, the bacterium that causes Q fever, with seroprevalence for the bacteria found to be as high as 53% in some wild populations.
This species can also serve as a reservoir for Toxoplasma gondii, the parasite that causes toxoplasmosis, though the disease usually spreads from rats to humans when domestic cats feed on infected brown rats.
The parasite has a long history with the brown rat, and there are indications that the parasite has evolved to alter an infected rat’s perception to cat predation, making it more susceptible to predation and increasing the likelihood of transmission.
Surveys and specimens of brown rat populations throughout the world have shown this species is often associated with outbreaks of trichinosis, but the extent to which the brown rat is responsible in transmitting Trichinella larvae to humans and other synanthropic animals is at least somewhat debatable. Trichinella pseudospiralis, a parasite previously not considered to be a potential pathogen in humans or domestic animals, has been found to be pathogenic in humans and carried by brown rats