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Humane Endpoints in Swiss Webster Mice Infected with Toxoplasma gondii RH Strain
Igor Falco Arruda1, Maria Regina Reis Amendoeira1, Thamires Francisco Bonifácio1
1Toxoplasmosis and Other Protozoan Diseases, Oswaldo Cruz Institute, Fiocruz, Manguinhos, Rio de Janeiro 21040-900, Brazil.
Abstract:
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.
Insights
This study identifies key clinical signs in mice infected with Toxoplasma gondii RH strain to establish humane endpoints. Implementing these refined methods reduces animal suffering without impacting parasite recovery.
Area of Science:
- Parasitology
- Animal Research Ethics
Background:
- The Toxoplasma gondii RH strain is highly virulent and commonly passaged in mice.
- Current protocols lack refinement from a 3Rs perspective (Replacement, Reduction, Refinement) to minimize animal distress.
Purpose of the Study:
- To establish humane endpoints for Swiss Webster mice infected with the T. gondii RH strain.
- To refine animal research procedures for maintaining the T. gondii RH strain.
Main Methods:
- 52 mice were infected with 5 × 106 tachyzoites/mL of the T. gondii RH strain.
- Daily monitoring of clinical parameters including body weight, hair condition, temperature, respiration, pain, stool consistency, and ascites.
- Parameters were recorded daily for up to 5 days post-infection.
Main Results:
- Prominent piloerection, respiratory distress, pain indicators, and ascites were identified as critical clinical signs.
- These signs can serve as effective cut-off points for implementing euthanasia.
- The refined method successfully minimized animal suffering and pain.
Conclusions:
- The identified clinical signs provide a basis for humane endpoints in T. gondii RH strain research.
- Adoption of these parameters can significantly reduce animal suffering in murine models.
- Refinement of protocols ensures animal welfare without compromising research outcomes.
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