|Classification and external resources|
Rat-bite fever is an acute, febrile human illness caused by bacteria transmitted by rodents, rats or mice in most cases, which is passed from rodent to human via the rodent's urine or mucous secretions. Alternative names for rat bite fever include streptobacillary fever, streptobacillosis, spirillary fever, sodoku, and epidemic arthritic erythema. It is a rare disease spread by infected rodents and can be caused by two specific types of bacteria. Most cases occur in Japan, but specific strains of the disease are present in the United States, Europe, Australia, and Africa. Some cases are diagnosed after patients were exposed to the urine or bodily secretions of an infected animal. These secretions can come from the mouth, nose, or eyes of the rodent. The majority of cases are due to the animal's bite. It can also be transmitted throughout food or water that is contaminated with rat feces or urine. Rats are not the only type of animal that can be infected with this disease. Others include weasels, gerbils, and squirrels. Household pets such as dogs or cats that are exposed to these animals can also carry the disease and infect humans. If a person is bitten by a rodent, it is important to quickly wash and cleanse the wound area thoroughly with antiseptic solution to reduce the risk of infection.
Rat-bite fever transmitted by the gram-negative coiled rod Spirillum minus (also known as Spirillum minor) 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. Rectal pain and gastrointestinal symptoms are less severe or are absent. Penicillin is the most common treatment.
The Streptobacillosis form of rat-bite fever is known by the alternative 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 an incubation period of 2–10 days, Haverhill fever begins with high prostrating fevers, rigors (shivering), headache and polyarthralgia (joint pain). Soon an exanthem (widespread rash) appears, either maculopapular (flat red with bumps) or petechial (red or purple spots) and arthritis of large joints can be seen. The organism can be cultivated in blood or articular fluid. The disease can be fatal if untreated in 20% of cases due to malignant endocarditis, meningoencephalitis or septic shock. Treatment is with penicillin, tetracycline or doxycycline.
Symptoms will be different for every person and will be different depending on the type of rat bite fever that a person is infected with. Both spirillary rat bite fever and streptobacillary rat bite fever have a few individual symptoms although most symptoms are crossovers. Streptobacillary is most commonly found in the United States and spirillary rat bite fever is generally diagnosed in patients in Africa as well as in other parts of the world. Rat bite symptoms are visually seen in most cases and include inflammation around the open sore. A rash can also spread around the area and appear red or purple. Other symptoms associated with streptobacillary rat bite fever include chills, fever, vomiting, headaches, and muscle aches. Joints can also become painfully swollen and pain can be experienced in the back. Along with rash and swollen joints, skin irritations like ulcers or inflammation can develop on the hands and feet. Wounds will heal slowly, so it is possible that symptoms will come and go over the course of a few months. It is important to contact a physician and report these symptoms immediately.
Symptoms associated with spirillary rat bite fever include issues with the lymph nodes. The lymph nodes which lie in the lymphatic system will often swell or inflame as a reaction to the disease or infection. The most common locations of lymph node swelling are in the neck, groin and underarm. Symptoms generally appear within two to ten days of exposure to the affected animal. It will begin with the fever and will progress to the rash that will appear on the hands and feet within two to four days. Rash will appear all over the body with this form of the infection and will rarely cause symptoms of joint pain.
Test and diagnosis
This condition is diagnosed by detecting the bacteria in skin, blood, joint fluid, or lymph nodes. Blood antibody tests may also be used. To get a proper diagnosis for rat bite fever, different tests are run depending on the type of symptoms that are being experienced.
To diagnosis streptobacillary rat bite fever, blood or joint fluid is extracted and the organisms living in it are cultured. Diagnosis for spirillary rat bite fever is by direct visualization or culture of spirillum from blood smears or tissue from lesions or lymph nodes. Treatment of antibiotics is the same for both types of infection.
Whilst obviously preventable by staying away from rodents, otherwise hands and face should be washed after contact and any scratches both cleaned and antiseptics applied. Prompt cleaning of wounds with antiseptic solution, and reducing the risk of rat bites. The effect of chemoprophylaxis following rodent bites or scratches on RBF is unknown. No vaccines are available for these diseases. Improve conditions to minimize rodent contact with humans is the best preventative measure for RBF. Animal handlers, laboratory workers, sanitation and sewer workers must take special precautions against exposure. Wild rodents, dead or alive, should not be touched and pets must not be allowed to ingest rodents. Those living in the inner cities where overcrowding and poor sanitation cause rodent problems are at risk for RBF. Half of all cases reported are children under 12 living in these conditions.
When proper treatment is provided for patients with rat bite fever, the prognosis is positive. Without treatment, the infection usually resolves on its own, although it may take up to a year to do so. A particular strain of rat bite fever that is located in the United States can progress and cause serious complications that can be potentially fatal. Before antibiotics were used for the treatment of rat bite fever, many cases resulted in death. If left untreated, streptobacillary can result in infection in the lining of the heart, covering over the spinal cord and brain, or in the lungs. Any tissue or organ throughout the body may develop a pocket of infection and pus, called an abscess.
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