Role of the dog, fox, cat and human as carnivore vectors in the transmission of the Sarcosporidia that affect sheep meat production

Abstract

The roles of six carnivores as potential sources to sheep of the sarcosporidial parasites causing cysts in meat were compared in a series of experiments carried out between 1973 and 1980. The research was concomitant with other studies that confirmed the prey-predator-prey-predator cycle of transmission. Infected carnivores act as vectors, excreting in their faeces coccidial sporocysts infective to the meat animal. For 60 experimental infections, sheep meat containing sarcocysts or sarcocysts removed from sheep meat were fed to experimental carnivores. Faecal samples were examined for sporocysts over 60 days post infection. Neither macroscopic (visible) sarcocysts nor microscopic sarcocysts from sheep carcasses were transmissible by humans or by ferrets (domestic polecats). Microscopic sarcocysts were readily infective to dogs, both domestic and dingo, as well as to foxes, but not to cats. Large numbers of sporocysts that could contaminate the environment were excreted. Both fat and thin visible sarcocysts were transmitted exclusively to cats. Although cats responded with relatively low levels of sporocysts, these were considered adequate to provide sufficient pasture contamination for the life cycle to be perpetuated. It is concluded that, while domestic dogs may be the greatest source of infection for sheep with microscopic sarcocysts, foxes as vectors also pose a threat to sheep production. Similarly, due to their widespread presence, feral cats play a role as well as domestic or semi-domestic cats in the spread of sarcocysts causing visible carcass lesions.

Abattoir surveillance of Sarcocystis spp., Cysticercosis ovis and Echinococcus granulosus in Tasmanian slaughter sheep, 2007–2013

“…in which carnivores act as the final host. Felines are the definitive hosts of the distinctive fat and thin mature macroscopic cysts associated with S. gigantea and S. medusiformis , respectively . Canines (including domestic dogs, foxes, coyotes and dingoes) are the definitive host for the microscopic cysts associated with S. tenella and S. arieticanis.…”

Toxoplasmaand other protozoan infections of economic importance in New Zealand

“…Four species have been described from sheep. These include: S. gigantea and S. medusiformis (first described from New Zealand ) (Collins et al 1976(Collins et al , 1979, both with sarcocysts which grow large enough to be macroscopically visible, and both transmitted by cats Collins et al 1979;Cole 1982); and S. tenella and S. arieticanis (Pomroy & Charleston 1987), whose sarcocysts are microscopic and which are both transmitted by dogs (Heydorn & Gestrich 1976;Erber 1982;Heydorn 1985) and some other canids (Ford 1986;Dubey et al 1989).…”

Miosite eosinofílica em bovinos abatidos para consumo humano

“…inflamatória associada, e o achado incidental do protozoário em lâminas de músculo estriado é um lugar comum na rotina histopatológica (Valentine & McGavin 2012). No Rio Grande do Sul acredita-se que a alta prevalência de Sarcocystis em bovinos esteja intimamente ligada ao hábito de se fornecer para a alimentação de cães, vísceras e órgãos de bovinos abatidos em propriedades rurais, ou ao consumo, pelos cães, de carcaças de bovinos mortos no campo por causas diversas (Ford 1986). A patogênese da miosite eosinofílica não está bem esclarecida e as lesões dessa condição não foram reproduzidas experimentalmente em espécies infectadas com Sarcocystis spp.…”