1. ITV Report

What is rat bite fever? The infection explained

Library picture of a pet rat similar to one which bit Chris Hammond from Leicester Photo: PA

What is 'rat bite fever'?

Rat-bite fever is a rare infection caused by the Streptobacillus moniliformis bacterium which is carried in rat saliva. It is rarely diagnosed in England & Wales - with around one or two cases per year.


Human infection is usually through the following ways:

  • from a rat bite/scratch
  • handling infected rats
  • ingestion of milk or water contaminated with the organism (via rat urine)

Person-to-person transmission does not occur.


Rat-bite fever usually develops within 7 days of the bite

  • It begins abruptly with fever and chills
  • Followed by severe swelling and joint pain, headache and nausea
  • Many patients develop a rash, most often on the extremities
  • About half of all patients develop a non-suppurative arthritis
  • a minority of cases have a form of non-bacteraemic disease with septic arthritis


The infection can be successfully treated with antibiotics; penicillin is the treatment of choice.

What to do if you think you're infected

The advice if you are bitten by a rat and think you are showing symptoms is to go to your local GP or hospital. The infection is only dangerous if left untreated and after a course of antibiotics the illness has no long term effects.