Diseases Spread By Rats

The Norway rat, the roof rat, and the house mouse are important rodents because they are found everywhere that humans are found. They are members of Murinae family and are also known as murine rodents. Murine rodents live in buildings, destroy food and property, compete with humans for existence, and endanger health. Rats carry a variety of infectious agents both internally and on their hair. Fleas from rats and mice occasionally spread diseases such as plague, typhus, tapeworms, among others.

Plague is caused by Yersinia pestis, a gram-negative bacillus. About 2000 cases of plague per year are reported to the WHO with a 10% mortality. The main reservoir is woodland rodents which transmit infection to domestic rats (Rattus rattus). The infection is transmitted by the rat fleas that bite humans when there is a sudden decline in rat population. Occasionally, spread of the organism may be through infected feces or through inhalation of dropl ets.4

Rats excrete vast amounts of Leptospira in their urine and thus contaminate rivers and soil. Domestic animals such as dogs and cats become a secondary source of infection for humans. Vulnerable humans may develop Weil's disease, a severe form of leptospirosis.

Rats carry Rickettsia burneti, the causative pathogen for Q fever, a common cause of pneumonia in Spain and Portugal.

Rats get infected with Lassa fever cause by arena virus. The disease is endemic in West Africa and is contracted through inhalation, ingestion, or inoculation of the virus.

Humans infected with rat lung worm (Angiostrongylus cantonensis) develop eosinophilic meningitis. The infection occurs through ingestion of raw aquatic animals such as prawns, snails and slugs, harboring infected larvae of the lungworm, or by eating vegetables contaminated with larvae. The infective larvae migrate to the central nervous system but do not develop into adult worms. The rat serves as reservoir host where the adult develops and passes infective eggs in rat feces.2

Pet rats (Ratus norvegicus) may be infected with cow pox virus that causes blistering of the skin and inflammation of the walls of the lymphatic vessels (lymphangitis).3

Rats are reservoir of the infectious agent Toxoplasma gondiithat causes toxoplasmosis both in animals and humans.

Ocular toxoplasmosisOcular toxoplasmosis Source: Middle East Afr J Ophthalmol. 2009 Oct-Dec; 16(4): 245–251.

Rat-bite fever is a disease caused by Streptobacillus moniliformis microbe and is characterized by fever, arthritis, and a rash. It can occur from close contact with rats or ingestion of contaminated food, water, or raw milk. The incidence of rat-bite fever is highest in urban areas with poor sanitation where there is a large population of rats. Swelling, abscesses, ulceration and secondary infections may develop at the site of the bite.5

Rats carry monkey pox virus which can infect pet prairie dogs that pass the infection to humans.

Rats are important carriers of Hantavirus.

Bamboo rats spread Penicillium marneffei a fungus causing mycosis, especially in AIDS patients. Infection occurs via inhalation of airborne conidia, with conversion to yeast stage in the lungs.7


  1. MCQs in Travel Medicine. Dom Colbert
  2. Infections of Leisure. edited by David Schlossberg
  3. Ferrets, Rabbits and Rodents: Clinical Medicine and Surgery. Katherine Quesenberry, James W. Carpenter
  4. Kumar and Clark's Clinical Medicine. Parveen Kumar, Michael L Clark
  5. Dermatology edited by Jean L. Bolognia, Joseph L. Jorizzo, Julie V. Schaffer
  6. Handbook of Environmental Health, Fourth Edition, Volume I. Herman Koren, Michael S. Bisesi
  7. Emerging Respiratory Infections in the 21st Century. Alimuddin Zumla, Wing-Wai Yew, David S.C. Hui

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