Completion of the cycle for transmission of sarcosporidiosis between cats and sheep reared specific pathogen free

The confirmation of a cat-sheep transmission for visible sarcocysts was achieved in specific pathogen free (SPF) animals by completing sheep-cat-sheep-cat passages during 1977-79. The study used 22 laboratory cats and 15 specially bred sheep. Experimental sheep were dosed with sporocysts recovered from cats fed visible sarcocysts. "Giant" or "fat" form of macroscopic sarcocysts commonly found on the oesophagus were first demonstrated in the SPF sheep at 17 months after dosing. The sarcocysts from these sheep were infective to cats. Thus, the cycle of transmission for cat-borne ovine sacosporidiosis was completed. Grazing sheep in some situations develop visible cysts earlier, around one year of age, hence it is considered that the infections of experimental sheep in SPF conditions may not reflect all the circumstances leading to natural infection.