Humane Endpoints in Swiss Webster Mice Infected with Toxoplasma gondii RH Strain.

Simple Summary: Toxoplasmosis is a globally distributed zoonosis caused by Toxoplasma gondii. This protozoan is capable of infecting mammals and birds and can cause significant impacts on human and animal health. Much of what is known about the parasite's biology, the immune mechanisms involved in toxoplasmosis, and the development of diagnostic tests for this protozoan disease is due to the maintenance of the parasite in laboratory mice. However, the increasing debate on the use of biomodels in scientific research has brought about the need to implement the principles of the 3Rs in laboratory protocols, such as experimental infections with T. gondii in murine models. Therefore, this study aimed to establish the humane endpoints for experimental infection with the T. gondii RH strain in Swiss Webster mice. The results presented here seek to disseminate the method we have proposed for the humane finalization of these animals in experimental protocols using this highly virulent strain as a method of refinement that seeks to enhance animal welfare. The highly virulent Toxoplasma gondii RH strain is maintained through successive passages in mice, but there is still a lack of studies that refine these procedures from a 3Rs perspective, where humanitarian ideals aim to minimize the stress, pain, or suffering of the animals used in the research without the loss of results. The aim of this study was to establish humane endpoints in Swiss Webster mice inoculated with the T. gondii RH strain. A total of 52 mice were infected with 5 × 106 tachyzoites/mL and monitored for periods of up to 5 days. The parameters body weight; hair condition; higher than normal body temperature; hypothermia; respiratory function; pain; soft stools or diarrhea; bloody diarrhea; tense, nervous, or in distress during handling; and ascites were recorded daily in score tables. The results showed that prominent piloerection, respiratory function, pain parameters, and ascites are important clinical signs to be used as a cut-off point for implementing euthanasia. The application of this refinement method helped to avoid animal suffering and pain without compromising the number of parasites recovered. We therefore suggest adopting these parameters in research protocols that require the maintenance of the T. gondii RH strain in murine models to avoid and reduce animal suffering. [ABSTRACT FROM AUTHOR]