Rat bite fever is a bit of a niche disease but one that I talk about a fair bit because it’s often missed, or at least diagnosed a lot later than it could (and perhaps should) be.  It’s not an issue with technology or testing – it’s an issue of human behaviour and failing to ask a simple question.

Rat bite fever is a bacterial infection caused mainly by Streptobacillus moniliformis. This bacterium lives in then mouth of most rats, and people mainly get exposed from rat bites (hence the name). Typically, infection causes a febrile illness that’s readily treatable, but it can sometimes cause serious complications, and it can be fatal.

A recent paper in BMC Infectious Diseases (Adams et al., 2021) describes an unusual presentation of rat bite fever, but a pretty typical story overall.

The report describes a 55-year-old man with infection of vertebrae (bones) in his back. He went to the hospital because of severe back pain, and didn’t have any classical signs of infection. Imaging showed abnormalities in his back, and a sample from the affected area was collected. Bacteria were seen, and antibiotics were started. Culture eventually yielded Streptobacillus moniliformis.

This is an unusual presentation of an unusual infection.  There’s no reason someone in this situation would have thought “hey, this might be a weird case of rat bite fever” when the patient arrived. He also responded well to treatment, so it’s not one of the cases where missing the diagnosis early had a major impact.

The main reason to mention this case report at all is this statement:

“On further history, it was revealed that patient had two pet rats and had sustained numerous bites in the last 1 year prior to symptom onset.”

That’s often when this information is obtained…”on further history.” Animal contact is often not queried until after a (often late) diagnosis of a zoonotic infection is made.

Would it have changed anything in this case?  Probably not.  However, “do you have pets” or, preferably “have you had contact with any animals” is a simple question to ask right at the start. It takes little time and no money, but it can lead to a quicker diagnosis in some situations.

More information about rat bite fever is available on the Worms & Germs Resources – Pets page.