Evaluation of Therapeutic Approaches for the Treatment of Spironucleus muris in Mice

Abstract

Spironucleus muris is an intestinal protozoal pathogen that can infect various species of rodents. The infection can have a wide range of clinical presentations, from no signs of disease to death. In addition, this pathogen can adversely affect research results, especially immunologic and gastrointestinal studies. For these reasons, institutions may exclude Spironucleus muris. However, despite rigorous efforts to keep this pathogen out, it can be common in rodent colonies. The current recommended approach to eradicating this pathogen is by testing and culling positive animals. A similar organism, Giardia muris, has been effectively eliminated by using chemotherapeutics. Therefore, the objective of this study was to determine whether S. muris is also susceptible to chemotherapeutics. Naturally infected mice were randomized to treatment groups after confirmation of positive infection via PCR. Mice received either metronidazole, fenbendazole, a combination of metronidazole-fenbendazole, or acidified water (control) treatments for a period of 4 wk. Each week fecal testing of S. muris was performed via PCR to evaluate the effectiveness of the treatments. At the end of the 4 wk period, mice were euthanized via CO2 inhalation and segments of the proximal gastrointestinal tract were submitted for histopathologic analysis. Treatment with metronidazole or fenbendazole alone or in combination, failed to clear S. muris infected mice. After 4 wk of treatment, none of the mice given fenbendazole via sucralose medicated gel were positive by either PCR or histopathology; however, this finding is most likely due to intermittent shedding rather than chemotherapeutic success. Therefore, the recommendation remains to test-and-cull or rederive mice as necessary to eliminate S. muris from laboratory animal facilities.