A treasured pet, a fever, and a rash

S.moniliformisHandA healthy 28 year old woman became abruptly ill with nausea and vomiting necessitating her abandoning her shift in a restaurant. She soon developed flu-like symptoms and a sore throat. The nausea and vomiting persisted for 3 days precipitating a visit to ER where she was diagnosed with gastroenteritis and given IV hydration.

She improved for a few hours but soon noticed a rash on much of her body, most pronounced on the distal parts of all her limbs. The nausea and vomiting settled but, what had been mild arthralgias / myalgias became much more severe especially in her wrists and hands. She returned to ER and was diagnosed with hand, foot and mouth disease.

During this visit blood cultures were drawn that proved to be diagnostic the following day. These photos were taken on the seventh day of illness after she returned to be assessed after report of positive blood cultures.




What type of pet does she have?

A rat

GAR was correct. She has a rat and is very close to it. She did not report a bite or scratch but did feed the rat from her hand and held it close to her face regularly.

Her disease is referred to as Rat Bite Fever and is caused by Streptobacillus moniliformis – a usual member of rat (and other rodent) oral flora.

People are classically infected by bites and scratches from rats or by eating or drinking food contaminated by rat saliva. There has been very few cases of Rat Bite Fever reported in Canada presumably because we have been successful in controlling human – rat contact for the large majority of our population.

Recently, however, there has been an increase in the popularity of rats as pets. In VIHA we have seen 6 cases in the last 3 years, most of which have been associated with pet rats without report of bites.

Laboratory diagnosis

This case (like all of the others) was diagnosed by identifying S. moniliformis in blood culture. This is the appearance of the organisms in the blood culture bottle. They tend to arrange themselves in parallel wavy “school of fish” patterns and are pointy or “fusiform” in shape. Streptobacillus_01

The Gram stain appearance of S. moniliformis after it is growing on solid media is very different than that seen in primary blood culture bottles. It is this very unusual “spaghetti and meatballs” appearance that is described as typical and is the source of the name “moniliformis” or “yeast like”. Streptobacillus_02

This isolate (like the other recent cases) was definitively identified with 16S ribosomal RNA amplification performed at BCCDC. It appears that Maldi-tof is another reliable means of identification.


Penicillin G is the “tried and true” therapy with most sources advocating at least 10 days of intravenous administration. However, the recent cases in VIHA have been managed successfully with less parenteral therapy. This woman was treated with 3 days of high dose intravenous Penicillin G and was discharged after very significant recovery on Penicillin V to complete a 3 week total course.

For more info see CDC – Rat Bite Fever.

Some thoughts on The perils of pet rats.

Category: Zoonoses

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