Rat-bite Fever
Rat-bite Fever
Disease History, Characteristics, and Transmission
Introduction
Rat-bite fever (RBF) is an acute infectious disease in humans caused by the scratch or bite of rodents, mostly rats, infected with one of two bacteria, Streptobacillus moniliformis or Spirillum minus. It is not transmitted from person to person. Scratches and bites are not necessarily the only way to contract the infection. Both bacteria are also able to be passed from rodents to humans through urine or mucous secretions from the eyes or nose of infected rats.
Rat-bite fever occurs most often among biomedical laboratory technicians, pet store employees who handle rodents, and people who have rodents as pets. It also occurs among people who live in rat-infested conditions. Children are more likely to be infected, both from their time spent inside and outdoors. Other animals that can carry the infectious bacteria are cats, dogs, gerbils, mice, squirrels, and weasels. The disease is also known as Haverhill fever and epidemic arthritic erythema (redness).
WORDS TO KNOW
ABSCESS: An abscess is a pus-filled sore, usually caused by a bacterial infection. It results from the body's defensive reaction to foreign material. Abscesses are often found in the soft tissue under the skin, such as the armpit or the groin. However, they may develop in any organ, and they are commonly found in the breast and gums. Abscesses are far more serious and call for more specific treatment if they are located in deep organs such as the lung, liver, or brain.
ERYTHEMA: Erythema is skin redness due to excess blood in capillaries (small blood vessels) in the skin.
SEPTIC: The term “septic” refers to the state of being infected with bacteria, particularly in the bloodstream
Disease History, Characteristics, and Transmission
Symptoms from the bacteria Streptobacillus moniliformis begin two to 22 days (usually within 10 days) after an initial bite or scratch. The infection can also be acquired by drinking contaminated milk or water (this form of the disease is sometimes referred to as Haverhill fever).
Symptoms are similar to severe influenza (flu), with a moderate fever (101–104°F [38.3–40.0°C]), chills, nausea, vomiting, headache, joint and back pain, gastrointestinal problems, and a reddish-pink rash (usually erupting about three days after initial contact with the bacteria) made of tiny bumps located generally on the palms of the hands and the soles of the feet.
Infections from the bacterium Spirillum minus are more common than infections with the other bacterium that causes rat-bite fever. With this bacterium, the infection is called spirillary rat-bite fever, or is sometimes known as sodoku. Symptoms do not begin until four to 28 days (usually less than 10 days) after exposure, and after the wound made by the bite or scratch has already healed. After the wound appears to initially heal, it suddenly becomes swollen and chronically inflamed.
Symptoms include fever, chills, and headache. The fever lasts longer than with Streptobacillus moniliformis, and may also reoccur over a period of months. Gastrointestinal symptoms are less severe than with the Haverhilltype fever. The rash is a light rosy color, causes itching, and covers most or all of the body. Joint and muscle pain does not usually occur or, if it does, it is much less severe than with the Haverhill-type fever.
Scope and Distribution
The infection caused by the bacterium Streptobacillus moniliformis has been found in the past to occur in the United States. With this bacterium, the infection is commonly called streptobacillary rat-bite fever. According to the Division of Bacterial and Mycotic Diseases, of the U.S. Centers for Disease Control and Prevention (CDC), it is rarely reported in the United States today and, consequently, accurate statistics on the incidence of the disease are not known.
The infection caused by the bacterium Spirillum minus is usually found in Asia and Africa, and its prevalence is much more common.
Treatment and Prevention
The bacterium Streptobacillus moniliformis is identified by a culture of blood or fluid that is taken from one of the affected joints of the infected human. The culture is then analyzed in a laboratory.
Antibiotics including procaine penicillin G or penicillin V by mouth (orally) are the most common treatments for streptobacillary rat-bite fever. If the patient is allergic to penicillin, erythromycin can be provided orally. Treatment is usually successful, although the infection can be sometimes eliminated by the human body itself, given sufficient time. However, if left untreated and when the body is unable to eliminate the disease, it can develop into serious complications such as septic (infectious) arthritis, abscesses (infections) to any tissue or organ of the body, endocarditis (inflammation of the heart's lining); meningitis (inflammation of the lining surrounding the brain and spine); and pneumonia (inflammation of the lungs). Without treatment, death can result from complications about 13% of the time.
The disease caused by the bacterium Spirillum minus is identified by examining blood or tissue removed from the wound of the infected human. Spirillary rat-bite fever is usually treated with procaine penicillin G or penicillin V by mouth. If the patient is allergic to penicillin, tetracycline can be given orally. If it is not treated, the fever usually subsides, but returns again in cycles of two to four days, which can continue for up for one year. In most circumstances, the illness, even without treatment, will resolve itself within four to eight weeks.
With both forms of rat-bite fever, the CDC Division of Bacterial and Mycotic Diseases recommends that humans avoid contact with animals capable of passing on the bacterial organisms. If contact cannot be avoided with rodents, recommendations include wearing gloves, regularly washing hands, and avoiding hand-to-mouth contact while handling rodents and cleaning their cages. With streptobacillary rat-bite fever, drinking only pasteurized milk and water from safe sources can help prevent the disease.
Impacts and Issues
Rat-bite fever and other types of rodent infestations contribute greatly to the decline of already poor communities. Rodents cause extensive losses of food and destruction of property when they are present in large numbers. They can cause damage and loss of revenue to grocery stores, warehouses, cargo carriers, and homes. Rodents can also cause loss of property due to fires from the gnawing of electrical wiring.
Sometimes rodents are controlled improperly with poisons, which exaggerates the problems already present. Health and safety problems can occur, especially among children, domesticated animals and pets, and the environment with improper poison use.
Along with rat-bite fever, large populations of rats within communities can increase the chance of contracting diseases such as hantavirus, leptospirosis (also called Weil's disease, canicola fever, and 7-day fever), plague, salmonella, and typhoid. These diseases can be potentially deadly, especially among the young and elderly.
See AlsoBacterial Disease; Vector-borne Disease; Zoonoses.
BIBLIOGRAPHY
Books
Committee on Infectious Diseases of Mice and Rats, Institute of Laboratory Animal Resources, Commission on Life Sciences, National Research Council. Infectious Diseases of Mice and Rats. Washington, DC: National Academy of Sciences, 1991.
Richardson, V.C.G. Diseases of Small Domestic Rodents. Oxford, UK, and Malden, MA: Blackwell Publishing, 2003.
Periodicals
Elliott, S.P. “Rat Bite Fever and Streptobacillus moniliformis.” Clinical Microbiology Reviews. January 1, 2007: 20 (1): 13–22.
Web Sites
Centers for Disease Control and Prevention. “Rat-bite Fever.” October 26, 2006 <http://www.cdc.gov/ncidod/dbmd/diseaseinfo/ratbitefever_g.htm#whatisrbf> (accessed March 18, 2007).