A 24 year old woman presented with fever and an abscess in her left antecubital fossa. She claimed that three weeks previously she had attended a blood donor session and an attempted cannulation at the site of the abscess had been unsuccessful. General examination was otherwise unremarkable and the only admitted history was of tonsillectomy, appendicectomy, and extraction of wisdom teeth. Incision and drainage of the abscess in the left antecubital fossa was undertaken on the night of admission and a ß haemolytic streptococcus and Escherichia coli were grown from the pus evacuated.
Her fever settled with intravenous antibiotics, but four days after admission a further abscess appeared on the dorsum of the right foot. Further inquiries led to a complete denial of any other relevant history.
In view of the two abscesses, a full screening for immunodeficiency was undertaken. Immunoglobulin and complement concentrations were measured and white cell function tests were performed all had normal results. The patient was negative for HIV antibodies. Other investigations performed for metastatic abscesses included abdominal ultrasonography and cerebral computed tomography, both of which had normal results.
As no further abscesses appeared during the next week's stay on the ward the patient was discharged, but she returned three days later with fever, rigors, and a swollen abscessing area in the right antecubital fossa. Again, examination was unremarkable apart from the abscess, but some tiny scars on the wrists were noted and under pressure she admitted to a suicide attempt.
Blood cultures were performed which eventually grew E coli and Streptococcus milleri, and the abscess in the right antecubital fossa was drained. She was again treated with intravenous antibiotics but six days after her admission another abscess appeared in the left antecubital fossa, which again required drainage.
Despite repeated questioning, no further helpful history was available. She vehemently denied, on confrontation, the possibility that she could either be using injecting drugs or injecting faeces into her veins. Subsequently her father, who lived 200 miles away, attended the ward and reported that the patient had been admitted to hospital with a halothane overdose in 1989 while working as a veterinary nurse. She also had a history of anorexia and bulimia with multiple suicide attempts.
Five days later she developed a further abscess on the right foot; it required drainage and again grew S milleri and E coli. Over the next two weeks she developed abscesses in her right perianal region and the right groin, both of which grew S milleri, and she then developed a suppurating wound on her abdominal wall in the right subcostal region.
On the evening that the abscess appeared on the patient's abdominal wall her friend, who visited her every day, was confronted and was found carrying a basket containing a large rat. It then became apparent that the patient had been sleeping with the rat, which was her pet, all the time she had been in hospital; her friend brought the rat in the evening and removed it in the morning. On re-examination we were unable to find any obvious rat bite marks on the patient's fingers or toes, but she habitually bit her nails and there were several lacerations on her fingers.
The multiple abscesses were thought to be due to rat bites and the patient was denied access to the rat, which had been her pet since being discovered in the wild some years before. Subsequently no further abscesses appeared, the rat no longer slept with the patient, and both remained well.
Rat bites are an uncommon cause of multiple skin abscesses, certainly in Western societies. Rat bite fever induced by Streptobacillus moniliformis is well described and is associated with chills, arthritis, and a diffuse rash