Rat Bite Fever FAQ

If your colony has tested negative for Streptobacillus Moniliformis (SBM) – Congratulations! Please consider joining the Facebook group Practical Rodent Testing and sharing your results so that we as a community can work towards healthier animals without this bacteria.

Other than general quarantine practices, you can help keep your colony safe by reducing the risk of exposure to wild rodents and performing routine testing. If your colony has tested positive for SBM, please remember that you are not alone. It is a heart breaking result to receive, but one that must be dealt with properly for the safety of yourself, other animals, and the community. SBM is the bacteria that causes Rat Bite Fever (RBF) in other species. Remember as well that with any positive result received from Charles River, you can order a free retest to confirm the positive!

SBM can be considered “normal flora” for rats, which have evolved to be reservoirs for this bacteria without any real direct impact on their health (a commensal). This wording of “normal” has led to a lot of misunderstanding. It is not “normal” in the sense that they all have it but instead insinuating they are a reservoir and are asymptomatic. Charles River routinely brings in rats from pet shops and private breeders who test negative for SBM. While quite a few breeders have recently tested positive, it is more likely due to the lack of awareness and testing in the past allowing infected stock to be spread – not that all rats are inherently infected.

While there have been several studies conducted to test the effectiveness of many different antibiotics on infected rats, none have proven successful – leaving no data to support the use of antibiotics to treat RBF in animals carrying the bacteria. It is considered “not practical” and dangerous to attempt treatment outside of a controlled laboratory environment. The only recognized way to eradicate RBF from a line  is Cesarean Rederivation, which should not be performed outside of a controlled veterinary or laboratory environment. Cross-fostering is currently being explored as a rederivation method for RBF

Unfortunately, with the bacteria’s persistence and risk to human life, depopulation is highly suggested by Charles River and the CDC. Depopulation can either be forced by euthanasia, or natural by letting your colony live out the rest of their lives in a quarantined environment with minimal contact and wearing a facemask and gloves when handling/cleaning to keep yourself and others safe.

RBF is not seen as a concern for reptiles or birds of prey and would be safe to feed off to those species. For the safety of others, any RBF positive feeders should be frozen and buyers should be informed to take proper precautions while handling.

The surface life of SBM is currently unconfirmed, but it has proven to be unstable outside of the host. Any possibly infected surfaces should be disinfected with bleach.

Informing others can be an incredibly daunting task, but can also be a life saving one! Any breeders you have received or shared stock with should be informed and suggested to test, as well as any pet homes. If you are able to accurately pinpoint the time of infection, that is a great place to start. Unfortunately we cannot control what others do with this information, but we can control what we do by spreading awareness and reducing the spread of the infection.

This is a common question from breeders with no simple answer. However, with constant exposure you are likely continuously maintaining immune protection – thus It’s possible that you have been infected and have immunity. There is also a possibility that you may have been infected long-ago, got sick (could be asymptomatic, mild, or severe) and you could have thought it was something else and never associated it with the rats.