What is Rat-Bite Fever?
Rat-bite fever, also known by several other names such as streptobacillosis, spirillary fever, bogger, and epidemic arthritic erythema, is a disease that can be directly transmitted from rodents to humans. Symptoms of rat-bite fever include recurring fever and pain in multiple joints, often moving from one joint to another. This disease can be contracted from rodents either via a bite or contact with rodent urine or other body fluids like saliva or eye secretions.
Rat-bite fever is caused by two types of bacteria – Spirillum minus and Streptobacillus moniliformis – both of which are normally found in the mouths of rodents. Although it’s a rare disease, cases have been reported in many parts of the world, including Japan, the United States, Europe, Australia, and Africa. Apart from rat bites, the disease can also spread by contact with urine or other body secretions of an infected rodent, consuming food or water contaminated with rodent feces or urine, and pets who’ve been exposed to infected rodents.
If a rodent bites you, it’s important to promptly and thoroughly clean the site of the bite to reduce the risk of infection. If left untreated, rat-bite fever can be deadly in up to 10% of cases. However, the disease can be effectively treated using antibiotics like Penicillin or Tetracyclines.
What Causes Rat-Bite Fever?
There are two types of bacteria that can cause rat-bite fever, leading to two different forms of illness.
The first is called ‘Spirillosis.’ It’s caused by a particular type of bacteria, known as Spirillum minus, which has a coiled shape. It’s pretty rare and usually found in Asia. Another name for this type of rat-bite fever is ‘Sodoku.’
The second form of rat-bite fever is ‘Streptobacillosis,’ which is a lot more common. This condition is also known as ‘epidemic arthritic erythema.’ It’s caused by a bacterium named Streptobacillus moniliformis. Streptobacillosis can be transmitted to humans through a rat bite or by consuming products, typically milk, that have been contaminated by the bacteria. When it’s transmitted via contaminated food, it’s also referred to as ‘Haverhill fever.’
Risk Factors and Frequency for Rat-Bite Fever
Every year, over two million animal bites happen in the United States, and rats cause about 1% of these. The most common person to get rat bite fever is a child under five years old who lives in poor conditions. People who work in pet stores or labs with rats are also at risk. There’s about a 10% chance of getting an infection from a rat bite.
Signs and Symptoms of Rat-Bite Fever
Rat bite fever can manifest in different ways, depending on the specific infecting organism that causes the disease:
- The type caused by Streptobacillus typically starts to show symptoms between three to twenty days after exposure, most cases take less than a week. These symptoms, which might take up to four weeks to appear, include recurring fever, migratory polyarthritis (pain in multiple joints that moves from one joint to another), and shaking chills. As the infection progresses, patients may also experience widespread muscle ache, swollen joints, back pain, and a skin rash. While both large and small joints can be affected, the knee and ankle joints are usually involved. One unusual thing to note is that the site of the rat bite often appears healed with little or no inflammation. If the site continues to show inflammation and tenderness, this might indicate a different disease.
- Spirillosis, another type of rat bite fever, has an incubation period of two to ten days. The bite site hardens and may ulcerate (break open to form ulcers) with associated lymphadenopathy (swelling of the lymph nodes). About half of the patients may develop a red-brown colored rash and rarely plaques.
- Haverhill fever is a variant of rat bite fever that presents with similar symptoms but typically occurs in individuals without a history of rat bite or contact with rats. These individuals often experience headaches, dizziness, and vomiting in addition to the other common symptoms of rat bite fever.
Testing for Rat-Bite Fever
To correctly diagnose certain illnesses, doctors need to be highly suspicious of symptoms presented by the patient. One such illness is caused by a bacteria named Streptobacillus moniliformis. This bacteria can be identified using a process called culturing, which involves growing the bacteria from a sample taken from the patient.
However, growing Streptobacillus moniliformis can be very challenging. The sample from the patient must be placed in a very specific environment, or ‘culture media,’ that does not contain a substance called Sodium Polyanethol Sulphonate. This substance is often used in culture media as an anticoagulant, which prevents blood clotting, but it also stops the growth of Streptobacillus moniliformis. Therefore, to grow this bacteria, doctors usually use anaerobic culture bottles, which do not contain Sodium Polyanethol Sulphonate.
Another disease, spirillosis, cannot be diagnosed via culturing. Instead, it can be identified by using dark field microscopy or Giemsa staining techniques. These methods involve applying a special stain to a sample from the patient, and then examining it under a microscope to identify the bacteria.
Treatment Options for Rat-Bite Fever
The best way to prevent a rat-bite fever is by avoiding contact with rodents. If contact is unavoidable, it’s essential to wash your hands and face after handling them. If you get scratched or bitten, clean the wound right away and apply an antiseptic. It’s not certain if taking medications after a rodent bite or scratch can prevent rat-bite fever.
People who frequently handle animals or work in labs, sanitation, or sewers should be particularly careful to avoid exposure. It’s also recommended not to touch wild rodents, whether they’re alive or dead.
If someone gets rat-bite fever, doctors usually use medications to treat it. Often, they’ll start with Penicillin G or Ceftriaxone given through a vein. After the patient starts feeling better, the treatment usually switches to an oral medication like Penicillin V, Ampicillin, or Amoxicillin. The treatment typically lasts two weeks. For people allergic to Penicillin, the antibiotic Doxycycline can be used instead.
What else can Rat-Bite Fever be?
These are some of the conditions that can present similar symptoms and therefore may need to be ruled out during a diagnosis:
- Meningococcemia
- Disseminated gonorrhea
- Lyme disease
- Brucellosis
- Ehrlichiosis
- Rickettsial infections
What to expect with Rat-Bite Fever
If the illness is not treated, the chances of death are around 10%.
Possible Complications When Diagnosed with Rat-Bite Fever
- Endocarditis: This is a condition where the inner lining of the heart becomes infected.
- Fulminant Sepsis: This is a severe and sudden infection that spreads throughout the body rapidly.
- Pneumonitis: This condition involves inflammation of the lungs.
- Meningitis: This is inflammation of the protective membranes covering the brain and spinal cord.
- Liver Abscess: This is a condition that develops when pus forms within the liver due to infection.
- Adrenal Gland Failure: This occurs when the adrenal glands, which sit on top of the kidneys, don’t produce enough hormones.
Preventing Rat-Bite Fever
It’s important for individuals who are regularly in contact with animals, particularly rats, to be aware of the risk of certain diseases. Taking the right safety measures can help to stop these diseases from spreading. If a rat bite occurs, it’s vital to seek medical help as soon as possible. This helps to reduce the risk of any complications and ensures you get the appropriate treatment promptly.
