Rat-bite fever overview
|
Rat-bite fever Microchapters |
|
Diagnosis |
|---|
|
Treatment |
|
Case Studies |
|
Rat-bite fever overview On the Web |
|
American Roentgen Ray Society Images of Rat-bite fever overview |
|
Risk calculators and risk factors for Rat-bite fever overview |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Rat-bite fever is an acute, febrile human illness caused by bacteria transmitted by rodents, rats in most cases. Two types of gram-negative facultatively anaerobic bacteria can cause the infection, which is passed from rodent to human via the rodent's urine or mucous secretions.Rat-bite fever (RBF) is an infectious disease caused by two different organisms, Streptobacillus moniliformis and Spirillum minus. In the United States, Rat-bite fever is primarily due to infection with S. moniliformis. Spirillum minus causes Rat-bite fever cases in countries such as Asia and Africa. S. moniliformis and S. minus are part of the normal respiratory flora of rats. Both organisms may be transmitted to humans through rat bites or scratches. Infection can also result from handling an infected rat, with no reported bite or scratch. Infection with S. moniliformis can also occur through ingestion of food or drink contaminated with rat excrement (Haverhill fever). Other rodents (e.g. mice, gerbils) may also be reservoirs. Person-to-person transmission has not been reported.
Spirillosis
Rat-bite fever transmitted by the gram-negative spirochaete Spirillum minus is more rare, and is found most often in Asia. In Japan the disease is called Sodoku. Symptoms do not manifest for two to four weeks after exposure to the organism, and the wound through which it entered exhibits slow healing and marked inflammation. The fever lasts longer and is recurring, for months in some cases. Joint pain and gastrointestinal symptoms are less severe or are absent. Penicillin is the most common treatment.
Streptobacillosis
The Streptobacillosis form of rat-bite fever is known by the alternate names Haverhill Fever and epidemic arthritic erythema. It is a severe disease caused by Streptobacillus moniliformis , transmitted either by rat bite or ingestion of contaminated products ( Haverhill fever). After a incubation period of around 10 days, Haverhill fever begins with high prostrating fevers, rigors, headache and polyarthralgia. Soon a exanthem appears, either maculopapular or petechial and arthritis of large joints can be seen. The organism can be cultivated in blood or articular fluid. The disease can be fatal if untreataed in 10% of cases due to malignant endocarditis, meningoencephalitis or septic shock. The treatment is with penicillin or tetracycline.
Pathophysiology
The initial scratch or wound caused by bite from a carrier rodent will result in mild inflammatory reactions and ulcerations. The wounds may heal initially, but reappears with the onset of symptoms. The incubation period is 4 to 28 days.
Risk Factors
Persons who are at risk for infection include those who work with animals in labs or pet stores and persons living in dwellings infested with wild rats. People who have pet rats may also be at risk for infection.
History and Symptoms
Initial symptoms are non-specific and include fever, chills, myalgias, arthralgias, headache, vomiting. Patients may develop a maculopapular rash on the extremities or septic arthritis 2-4 days after fever onset. The incubation period typically ranges from 2-10 days. If not appropriately treated, severe manifestations may include endocarditis, myocarditis, meningitis, pneumonia and sepsis. In rare cases, death occurs.
The findings of rash, fever, and arthritis in individuals with a history of rat exposure suggest the diagnosis of Rat-bite fever.
Physical Examination
The findings of rash, fever, and arthritis in individuals with a history of rat exposure suggest the diagnosis of Rat-bite fever.
Medical Therapy
Responds to penicillin antibiotics. In cases allergic to penicillin, erythromycin or tetracyclines can be used for respectively streptobacillary or spirillary infections.
Prevention
Preventable by staying away from rodents, washing hands and face thoroughly after contact and cleaning and applying antiseptics to any scratches.