rat-bite fever

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Related to Rat-bite fevers: Q fever, Streptobacillary Fever

Rat-Bite Fever



Rat-bite fever refers to an infection which develops after having been bitten or scratched by an infected animal.


Rat-bite fever occurs most often among laboratory workers who handle lab rats in their jobs, and among people who live in poor conditions, with rodent infestation. Children are particularly likely to be bitten by rodents infesting their home, and are therefore most likely to contract rat-bite fever. Other animals that can carry the types of bacteria responsible for this illness include mice, squirrels, weasels, dogs, and cats. One of the causative bacteria can cause the same illness if it is ingested, for example in unpasteurized milk.

Causes and symptoms

There are two variations of rat-bite fever, caused by two different organisms. In the United States, the bacteria Streptobacillus moniliformis is the most common cause (causing streptobacillary rat-bite fever). In other countries, especially Africa, Spirillum minus causes a different form of the infection (called spirillary rat-bite fever).
Streptobacillary rat-bite fever occurs up to 22 days after the initial bite or scratch. The patient becomes ill with fever, chills, nausea and vomiting, headache, and pain in the back and joints. A rash made up of tiny pink bumps develops, covering the palms of the hands and the soles of the feet. Without treatment, the patient is at risk of developing serious infections of the lining of the heart (endocarditis), the sac containing the heart (pericarditis), the coverings of the brain and spinal cord (meningitis), or lungs (pneumonia). Any tissue or organ throughout the body may develop a pocket of infection and pus, called an abscess.
Spirillary rat-bite fever occurs some time after the initial injury has already healed, up to about 28 days after the bite or scratch. Although the wound had appeared completely healed, it suddenly grows red and swollen again. The patient develops a fever. Lymph nodes in the area become swollen and tender, and the patient suffers from fever, chills, and headache. The skin in the area of the original wound sloughs off. Although rash is less common than with streptobacillary rat-bite fever, there may be a lightly rosy, itchy rash all over the body. Joint and muscle pain rarely occur. If left untreated, the fever usually subsides, only to return again in repeated two-to four-day cycles. This can go on for up to a year, although, even without treatment, the illness usually resolves within four to eight weeks.


In streptobacillary rat-bite fever, found in the United States, diagnosis can be made by taking a sample of blood or fluid from a painful joint. In a laboratory, the sample can be cultured, to allow the growth of organisms. Examination under a microscope will then allow identification of the bacteria Streptobacillus moniliformis.
In spirillary rat-bite fever, diagnosis can be made by examining blood or a sample of tissue from the wound for evidence of Spirillum minus.


Shots of procaine penicillin G or penicillin V by mouth are effective against both streptobacillary and spirillary rat-bite fever. When a patient is allergic to the penicillins, erythromycin may be given by mouth for streptobacillary infection, or tetracycline by mouth for spirillary infection.


With treatment, prognosis is excellent for both types of rat-bite fever. Without treatment, the spirillary form usually resolves on its own, although it may take up to a year to do so.
The streptobacillary form, found in the United States, however, can progress to cause extremely serious, potentially fatal complications. In fact, before antibiotics were available to treat the infection, streptobacillary rat-bite fever frequently resulted in death.


Prevention involves avoiding contact with those animals capable of passing on the causative organisms. This can be an unfortunately difficult task for people whose economic situations do not allow them to move out of rat-infested buildings. Because streptobacillary rat-bite fever can occur after drinking contaminated milk or water, only pasteurized milk, and water from safe sources, should be ingested.

Key terms

Abscess — A pocket of infection; a collection of pus.
Endocarditis — An inflammation of the lining of the heart.
Meningitis — An inflammation of the tissues covering the brain and spinal cord.
Pasteurization — A process during which milk is heated up and maintained at a particular temperature long enough to kill bacteria.
Pericarditis — An inflammation of the sac containing the heart.



Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311. http://www.cdc.gov.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.

rat-bite fever

either of two distinct diseases transmitted to humans by the bite of an infected rat or less commonly of a squirrel, weasel, dog, cat, or pig. The more common of the two in the United States is Haverhill fever. The other form, sodoku, rarely occurs in North America but is observed frequently in Japan and other countries around East Asia. Although when both diseases were originally identified they followed the bite of a rat or similar animal, there are also other modes of transmission.

Haverhill fever is caused by Streptobacillus moniliformis. If the disease follows a rat bite, a fluid-filled sore appears at the site of the bite within 10 days. High fever alternates with periods of normal temperature at intervals of 24 to 48 hours, and there is swelling of regional lymph nodes. The joints—usually the large joints—become reddened, swollen, and painful. There may be back pain, and a spotty, measles-like skin rash.

Sodoku, or spirillar rat-bite fever, is caused by Spirillum minus. The original bite heals promptly, but within 5 to 28 days the site becomes swollen and takes on a dusky, purplish hue. There is usually no joint inflammation and the rash is patchy rather than spotty. Otherwise the symptoms are similar to those characteristic of Haverhill fever.

Treatment for both forms of rat-bite fever is with penicillin, tetracycline, or other antibiotics.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

rat-·bite fe·ver

a single designation for two bacterial diseases associated with rat bites, one caused by Streptobacillus moniliformis (for example, Haverhill fever), the other by Spirillum minus (also called S. minor) (for example, sodoku); both diseases are characterized by relapsing fever, chills, headache, arthralgia, lymphadenopathy, and a maculopapular rash on the extremities.
Farlex Partner Medical Dictionary © Farlex 2012

rat-bite fever

Either of two infectious diseases contractible from the bite of a rat, specifically:
a. A disease caused by the bacterium Streptobacillus moniliformis and characterized by skin inflammation, back and joint pains, headache, and vomiting.
b. A disease caused by the bacterium Spirillum minus and characterized by ulceration at the site of the bite, a purplish rash, and recurrent fever.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.
A bacterial zoonosis caused by Spirillum minus (Spirillium minor) a gram-negative flagellated microaerophilic bacterium found in the saliva of rats and acquired through rat bites or scratches or less commonly as a nosocomial infection
Management Penicillin, tetracycline
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

rat-bite fever

Infectious disease Either of 2 similar systemic bacterial infections caused by different gram-negative facultative anaerobes
1. Streptobacillary RBF–caused by infection with Streptobacillus moniliformis, transmitted in crowded urban environs by ingesting milk contaminated by rat feces; S moniliformis is present in the nasopharynx of up to 50% of healthy lab and wild rodents Clinical 2-10 day incubation followed by an irregularly relapsing fever and asymmetric polyarthritis followed within 2-4 days by a maculopapular rash on extremities, palmoplantar surfaces; bite wound heals spontaneously; headache, N&V, myalgia, minimal regional lymphadenopathy, anemia, endocarditis, myocarditis, meningitis, pneumonia, and focal abscesses may occur; most cases resolve spontaneously within 2 wks, 13% of untreated cases are fatal Diagnosis Streptobacillary RBF can only be diagnosed by blood culture; S moniformis is a slow grower with strict growth requirements, making it difficult for most labs to culture; no serologic test is available; biological false positives for syphilis occur Management Penicillin, tetracycline, streptomycin.
2. Spirillary RBF caused by Spirillum minus which occurs worldwide, but is most common in Asia; it has a longer incubation period (1-3 weeks), rare arthralgia, and an inoculation wound which can reappear at the onset of Sx or persist with edema and ulceration Management Penicillin, tetracycline, streptomycin. See Sodoku.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

rat-bite fe·ver

(rat'bīt fē'vĕr)
A single designation for two bacterial diseases associated with rat bites, one caused by Streptobacillus moniliformis (i.e., Haverhill fever), the other by Spirillum minus (i.e., sodoku); both diseases are characterized by relapsing fever, chills, headache, arthralgia, lymphadenopathy, and a maculopapular rash on the limbs.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

rat-bite fever

Either of two diseases transmitted by the bite of a rat or by ingestion of contaminated milk. They are sodoku, occurring mainly in Japan, and caused by Spirillum minor , and Haverhill fever, caused by Streptobacillus moniliformis , occurring mainly in North America. Both feature painful inflammation at the site of the bite, fever, spleen and lymph node enlargement and lymph vessel inflammation (LYMPHANGITIS) and a dusky red, slightly raised, sparse rash. Haverhill fever also sometimes causes multiple joint ARTHRITIS. Both diseases respond well to penicillin and other antibiotics.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
References in periodicals archive ?
Rat-bite fever (Streptobacillus moniliformis): a potential emerging disease.