What Is Rat-Bite Fever?

Rat bite fever is an acute infectious disease caused by bites from house rats or other rodents. It is a disease with different pathogens and different clinical manifestations. Pathogens are Microspira and Streptococcus candida, respectively. Clinically, rat bite fever is divided into two types according to pathogen classification. Microspirillum type This type is distributed all over the world, mostly in Asia. There are scattered cases reported in China, mostly south of the Yangtze River. Rodents are the source of infection, and cats, pigs, and other carnivores that have bitten sick rats are also infectious. People get sick after being bitten by these animals. The population is generally susceptible to this type, and infants and laboratory workers with poor sanitation in the place of residence are more likely to be infected. The disease is spread all over the world, but there are fewer cases. China has only seen reports of microspira. After antibiotic treatment, the prognosis is better. The untreated mortality rate is 10%. The two types differ in all aspects of infection, clinical manifestations, diagnosis, and treatment. Streptococcus candida-type infections are rodents such as wild or laboratory-raised rodents. Humans get sick by being bitten by sick rats or eating food contaminated with pathogenic bacteria. No rat bite fever has been reported in China so far.

Basic Information

English name: rat bite fever
Visiting department: Infectious Diseases
Common causes: Microspira, Streptococcus candida

Common symptoms: Fever, rash, etc.
Contagious: Have
way for spreading: Human being bitten by sick rats or eating food contaminated with pathogenic bacteria

Causes of rat bite fever

There are two types of pathogens: one is Microspirillum or Treponema pallidum, belonging to the family Spirulina, with a length of about 3 to 5 m, flagella, and rapid movement. The disease caused by it is spirillum fever; Bacillus, belonging to the family Vibrioaceae, has a length of 1 to 3 m and is round, oval, or fusiform. The disease caused by it is streptococcal fever. The former is transmitted by rodents; the latter can be transmitted by contaminated milk and food in addition to rodents.

Clinical manifestations of rat bite fever

Fever, rash, and systemic symptoms are common manifestations of the two.

Streptococcus candida

The incubation period is short, about 10 days. Fever and chills appear in the early stage, and general measles-like rash appears after 2 to 4 days, which can involve rash and ecchymosis. Joint pain, pleural effusion, endocarditis, pneumonia, and septic infarction can occur.

2. Microspirillum type

The incubation period is longer, 1 to 4 weeks. Suddenly high fever and chills occurred. Inflammation and ulcers in the bite can cause lymphangitis. The initial stage of skin lesions is erythema, which is more common in the abdomen, and is not abundant in number. It can be fused into a piece, showing a purple-red color, forming a hard plaque.

Rat bite fever check

Blood test

The white blood cell count increased (15-30) × 10 ⁹ / L, and the number of eosinophils could also increase.

2. Bacteriological examination

For cases caused by Microspirillum, in addition to the history of rat bites, the pathogen must be searched from the patient's blood, joint fluid, or local pus, or the spirochaetes should be detected under a dark field microscope, or the smear should be examined after staining. If the blood is inoculated into the peritoneum of mice, guinea pigs or rabbits, and the blood and peritoneal fluid are checked after 1 week, it is easy to find the microspira of the disease. Because animals can carry such pathogens, blood must be checked before vaccination to ensure that they are not infected before vaccination. For cases caused by Streptococcus, in addition to the above methods to find the pathogen, a rapid diagnosis can be made by gas-liquid chromatography, and the presence of lectins can be checked by serological methods.

Rat bite fever diagnosis

Diagnosis can be confirmed based on rodent bite history, fever, rash and systemic symptoms and related examinations.

Rat bite fever treatment

The bite area is immediately corroded with nitric acid to clean the wound to prevent tetanus. Penicillin, tetracycline, or second- and third-generation cephalosporins.