Haverhill fever is a term used to describe an infection by streptobacillus moniliformis, the causative agent of rat bite fever. Apart from a different mode of infection (ingestion of food, water or milk contaminated by rodent feces), the clinical presentation is almost identical - fever, headaches, joint pain and myalgia are most prominent signs. Advanced microbiological methods are necessary to make the diagnosis.
Haverhill fever, named after an outbreak of the disease in Haverhill, Massachusetts in 1926, through contamination of milk, is a bacterial infection caused by streptobacillus moniliformis. This microorganism is more frequently known as the causative agent of rat bite fever, occurring after the bite of a rodent (most commonly a rat)    . Due to the similar etiology, Haverhill fever and rat bite fever have the same clinical presentation, although different modes of infection are described  . Haverhill fever, considered to be a very rare infection, appears after ingestion of food products (turkey, water, and milk are mentioned) contaminated by rodent feces, with an incubation period of 2-10 days   . Fever, headaches, fatigue, myalgia, migratory polyarthralgia (involving the hands, wrists, elbows and knees in most cases), vomiting, weight loss, diarrhea, and chills are clinical hallmarks of this infection   . It should be noted that Haverhill fever may be distinguished from rat bite fever by more severe episodes of vomiting and an increased rate of pharyngitis . Numerous complications of infection caused by S. moniliformis have been described in the literature, including meningitis, pneumonia, endocarditis, and development of abscesses in various organs . These complications are perhaps one of the reasons why a mortality rate of 10-13% is observed in the absence of proper antibiotic therapy  . For this reason, early recognition is imperative to prevent complications.
Having in mind the very rare occurrence of Haverhill fever in medical practice, the diagnosis may be difficult to make, but a detailed patient history and a thorough physical examination can provide vital information for a presumptive diagnosis  . Firstly, recent consumption of "suspicious" food or beverages must be noted during history taking, whereas signs of vomiting and constitutional symptoms accompanied by a migratory polyarthritis could be sufficient to order further laboratory testing to exclude S. moniliformis as the underlying cause of symptoms. A complete blood count (CBC), inflammatory parameters - C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) and fibrinogen, as well as serum electrolytes and protein levels are recommended in workup, while microbiological studies, mainly cultivation of blood or joint fluid, is mandatory for the diagnosis of Haverhill fever   . Blood cultures can detect S. moniliformis after 3-7 days of growth, but because this bacterial pathogen requires specific media for cultivation, laboratories must be noted in advance, in order to prepare necessary components for testing . The recent introduction of novel molecular techniques, such as polymerase chain reaction (PCR), has greatly improved the diagnosis of many microbial organisms, including bacteria, and this procedure should be performed whenever possible   . Due to its cost, however, it is still not widely available in the developing world, and the diagnosis still relies on high clinical suspicion and results obtained from cultivation .