Classification

Gram-negative coccobacillus

Family

Pasteurellaceae. Part of a larger group of bacteria, the Pasteurella-Haemophilus-Actinobacillus complex has been reclassified as Rodentibacter species. Type species Pasteurella pneumotropica Heyl has been reclassified as Rodentibacter Heylii. and type species Pasteurella pneumotropica Jawetz has been reclassified as Rodentibacter pneumotropicus

Affected species

Rats and mice are the primary carriers, although guinea pigs, hamsters, and gerbils may also be infected.

Frequency

Common in laboratory populations. Prevalence in the wild is unknown, although likely to be common.

Transmission

Rodentibacter is transmitted by direct contact with infected animals or their secretions. Humans are not common carriers, nor does the organism multiply or live for long periods in the environment.

Clinical Signs and Lesions

Infection of immunocompetent and most immunodeficient animals with Rodentibacter is asymptomatic. Rarely, clinical signs are seen if infected animals are stressed, or, as with any other opportunistic agent, there is a convenient port of entry. Nude mice with Rodentibacter may develop retrobulbar abscesses of the lacrimal gland, sometimes associated with a penetrating foreign body. Rodentibacter has been found associated with conjunctivitis, rhinitis, otitis, and cervical lymphadenitis in mice and rats. In immunosuppressed animals infected with Pneumocystis or other pathogens, Rodentibacter co-infection may lead to suppurative bronchopneumonia. Co-infection with Rodentibacter has been shown to exacerbate respiratory disease in mice with Mycoplasma or Sendai virus infections.

Diagnosis

Rodentibacter is best detected by culture or by specific PCR. Cultures should be taken from the usual colonization sites: the nasopharynx, the vagina, and the intestines. Rodentibacter may also be isolated from the conjunctiva in some cases. Screening mice via serology is not recommended, as animals with subclinical infections are often negative via serology, and animals infected with other Pasteurellaceae may show cross-reactivity.

Interference with Research

Animals carrying Rodentibacter may be suitable for research, unless clinically ill. This is an organism best excluded from colonies of immunodeficient animals, however.

Prevention and Treatment

Prevention of Rodentibacter infection consists of exclusion of Rodentibacter carriers from the animal facility. Quarantine or rederivation of incoming animals may be particularly valuable in this respect. Exclusion of wild or feral animals from animal facilities is also important. Rodentibacter is a fragile organism, which does not survive long outside a host. It may be difficult to transmit to healthy animals using dirty bedding, which may make sentinel monitoring programs unreliable.

Treatment is possible, but it is unlikely that antibiotic treatment will resolve a carrier state. Rodentibacter may be transmitted to fetuses in utero, through contact with infected uterine tissue. Embryo transfer, rather than hysterectomy rederivation, may be the best choice for a  Rodentibacter-infected colony. Hysterectomy rederivation may be accomplished by treating animals with antibiotics before surgery, careful attention to aseptic technique, and taking precautions such as dipping the removed uterus in a disinfectant before removing the pups.

Due to its fragility in the environment, stringent environmental decontamination is not necessary. Regular cleaning and the use of a high-level disinfectant should suffice to rid the environment of Rodentibacter.

  • References

    Baker DG. Natural Pathogens of Laboratory Animals: Their effects on research. Washington, D.C.: ASM Press; 2003

    Fox JG, Anderson LC, Otto G, Whary M,  Pritchett-Corning K, editors. Laboratory Animal Medicine. 3rd ed. San Diego: Academic Press; 2015

    Fox J, Barthold S, Davisson M, Newcomer C, Quimby F, and Smith A editors. The Mouse in Biomedical Research: Diseases. 2nd ed. New York: Academic Press; 2007

    Percy DH, Barthold SW, Griffey SM, Pathology of Laboratory Rodents and Rabbits. 4th  ed. Ames: Iowa State University Press; 2016

    Benga L, Sager M, Christensen H, From the Pasteurella pneumotropica complex to Rodentibacter, Review Article: Veterinary Microbiology, Elsevier; 2018

    Scharmann, W., and A. Heller. 2001. Survival and transmissibility of Pasteurella pneumotropica. Lab Anim 35:163-166.

    Serre, S., F. Veillet, P. Hardy, and A. Kodjo. 2004. Survival of rodent isolated Pasteurella pneumotropica, Staphylococcus aureus and Pseudomonas aeruginosa in different types of water. Revue Méd. Vét. 155:435-439.