Pathogen Screening in Adult Frozen Feeder Mice Commonly Reveals Zoonotic Rodent-Adapted Cryptosporidium Spp.

Background Feeder rodents include mice, rats, and occasionally other rodents that are used to feed animals under human care including reptiles, amphibians, birds of prey, and other zoological species. Feeder rodents have previously been associated with numerous outbreaks and isolated infections of zoonotic diseases. Methods Frozen adult feeder mice (Mus musculus) from several popular commercial sources were screened for the presence of Cryptosporidium spp., Hantaan virus, Leptospira spp., lymphocytic choriomeningitis virus, Salmonella spp., and Streptobacillus moniliformis via polymerase chain reaction (PCR). PCR was performed on pooled fecal samples for Cryptosporidium spp. and on pooled oral swabs and fecal samples for the remaining pathogens. Samples were pooled from multiple mice, but sources were tested independently. Results None of the pooled samples tested positive for Hantaan virus, Leptospira spp., lymphocytic choriomeningitis virus, Salmonella spp. or Streptobacillus moniliformis; however, Cryptosporidium spp. were detected in pooled fecal samples from a majority of rodent sources (8/10, 80.0%). The majority of the positive isolates (6/8; 75%) were identified as Cryptosporidium tyzzeri, a rodent-adapted Cryptosporidium spp. with zoonotic potential. Conclusions and clinical relevance Results of this pilot study suggest that rodent-associated Cryptosporidium spp. including C. tyzzeri are common in frozen adult feeder mice; however, the viability and infectivity of these organisms following freezing is unknown. Due to the infectious and zoonotic potential of these pathogens, pet owners and animal caretakers should take precautions to prevent disease transmission when handling frozen feeder rodents.