Rat bite fever

An acute, febrile human illness caused by bacteria transmitted by rodents.

It is a zoonotic disease.

It can be directly transmitted by rats, gerbils, and mice to humans by either a bite or scratch or it can be passed from rodent to rodent.

The causative bacterial agent has also been observed in squirrels, ferrets, dogs, and pigs, but the most common reservoir of the disease is rats.

Nearly all domestic and wild rats are colonized by the causative bacterial agent, Streptobacillus moniliformis.

Due to increasing population density, this illness is being seen more frequently

It is estimated that 1 in 10 bites from a rat will result in rat bite fever infection.

In most cases, it is passed from rodent to human by the rodent’s urine or mucous secretions.

Most cases of the disease reported from densely populated regions, such as big cities.

The bacteria can be acquired through ingestion of contaminated water or food by rodent feces, (Haverhill Fever).

It is a rare disease spread by infected rodents and can be caused by two specific types of bacteria.

Gram-negative coiled rod Spirillum minus and Streptobacillus moniliformis are the types of bacteria that cause the disease.

Rat-bite fever transmitted by the Gram-negative coiled rod Spirillum minus is more rare, and is found most often in Asia.

Both spirillary and streptobacillary rat-bite fever have a few individual symptoms, although most of their symptoms overlap.

Rat-bite symptoms in most cases include inflammation around the open sore, and 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, myalgias, joint pain and swelling and back pain.

Skin ulcers or inflammation can develop on the hands and feet.

Skin healing is slow, over the course of a few months.

Spirillary rat-bite fever symptoms include lymph node enlargement.

The most common locations of lymph node swelling are in the neck, groin, and underarm.

Symptom onset generally appear within 2 to 10 days of exposure to the infected animal.

Symptoms begin with fever and progresses to the rash on the hands and feet within 2 to 4 days.

Rash appears all over the body with Spirillary rat bite fever.

Spirillary rat bite fever is rarely associated with joint pain.

Most cases occur in Japan.

Certain strains of the disease are present in the United States, Europe, Australia, and Africa.

Exposure to the urine or bodily secretions of an infected animal can transmit the disease.

Secretions can come from the mouth, nose, or eyes of the rodent, but the majority of cases are due to the animal’s bite.

Transmission can be transmitted through food or water contaminated with rat feces or urine.

Other animals can be infected with this disease: weasels, gerbils, and squirrels, dogs or cats exposed to these animals can also carry the disease and infect humans.

Rodent bites should be quickly washed and cleansed with an antiseptic solution to reduce the risk of infection.

Streptobacillosis is most commonly found in the United States.

Spirillary rat-bite fever is generally diagnosed in patients in Africa.

In Japan, the disease is called sodoku.

Spirillary rat-bite fever symptoms manifest two to four weeks after exposure to the organism, and the wound through which it entered exhibits slow healing and marked inflammation.

Its 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 also known as Haverhill fever and epidemic arthritic erythema.

The streptobacillosis form of rat-bite fever is a severe disease caused by Streptobacillus moniliformis, transmitted either by rat bite or ingestion of contaminated products.

The streptobacillosis form of rat-bite fever has an incubation period of 2-10 days beginning with high fever, rigors, headache, and polyarthralgia.

Subsequently, a widespread rash appears, either maculopapular or petechial and arthritis of large joints can occur.

The organism can be isolated in blood or articular fluid, skin, or lymph nodes.

RBF can be fatal if untreated in 20% of cases due to endocarditis, meningoencephalitis, or septic shock.

Treatment is with penicillin, tetracycline, or doxycycline.

Blood antibody tests may also be used for diagnosis.

Diagnosis for spirillary rat bite fever is by direct visualization or culture of spirilla from blood smears or tissue from lesions or lymph nodes.

RBF is preventable by avoiding rodents, otherwise hands and face should be washed after contact and any scratches both cleaned and local antiseptics applied.

The effect of chemoprophylaxis following rodent bites or scratches is unknown.

No vaccines are available for these diseases.

Preventative measure is to minimize rodent contact with humans.

Treatment with penicillin is the same for both types of infections.

When allergies are present, erythromycin or tetracyclines are used.

Without treatment, the infection usually resolves on its own.

Infection resolution without treatment may take a year or so.

When proper treatment is provided for patients with rat-bite fever, have a favorable prognosis.


Before antibiotics many cases resulted in death. 

If left untreated, streptobacillary rat-bite fever can result in endocarditis, meningoencephalitis, or pneumonia.

Any tissue or organ throughout the body may develop an abscess, in the absence of antibiotic treatment.

If left untreated the mortality rate of RBF is 13%.

Even when treated, it can lead to migratory and chronic arthritis which can persist for weeks to years after initial infection and treatment.

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