Pneumocystis Murina Infection in Immunodeficient Mice in a Closed Barrier Unit: a Case Report
Pneumocystis is an important pathogen in immunocompromised individuals. In colonies of immunodeficient mice, P. murina can cause wasting disease and make the breeding and maintenance of immunodeficient animals difficult, unless they are continuously treated with sulfadiazin/trimethoprim. At University of Aarhus immunodeficient and immunocompetent mice were co-housed in a barrier unit. The facility was closed for entrance of animals (except for embryos for embryo transfer) and the entrance for personnel was highly restricted. The breeding performance of immunodeficient animals was comparable to that of the immunocompetent mice for a period of more than 3 years, until wasting disease and decreased litter size specifically in the breeding colony of immunodeficient mice occurred. Clinical symptoms of affected mice included laboured breathing, hunched up position, unwillingness to move, and ruffled coat. Pneumocystis infection was confirmed by histological examination and PCR. The partial sequence of the mitochondrial large subunit rRNA gene obtained (GenBank accession no AF548626) displayed 99 % identity to that of Pneumocystis murina (formerly Pneumocystis carinii f.sp.muris) found in laboratory mice. The immunodeficient animals were removed from the barrier and treated with sulfadiazin/trimethoprim in a separate unit. After the removal of immunodeficient animals, Pneumocystis could not be detected by PCR in the remaining animals. Our data add to the growing evidence that immunocompetent animals harboring Pneumocystis as a subclinical infection may be reservoirs for this organism. Still it remains to be determined how the infection was introduced and whether a latent infection can persist or the outbreak was caused by leakage in the barrier.