Didelphis: A genus of large OPOSSUMS in the family Didelphidae, found in the Americas. The species Didelphis virginiana is prominent in North America.Opossums: New World marsupials of the family Didelphidae. Opossums are omnivorous, largely nocturnal and arboreal MAMMALS, grow to about three feet in length, including the scaly prehensile tail, and have an abdominal pouch in which the young are carried at birth.Marsupialia: An infraclass of MAMMALS, also called Metatheria, where the young are born at an early stage of development and continue to develop in a pouch (marsupium). In contrast to Eutheria (placentals), marsupials have an incomplete PLACENTA.Disease Reservoirs: Animate or inanimate sources which normally harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. Reservoirs are distinguished from vectors (DISEASE VECTORS) and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks.Sarcocystis: A genus of protozoa found in reptiles, birds, and mammals, including humans. This heteroxenous parasite produces muscle cysts in intermediate hosts such as domestic herbivores (cattle, sheep, pigs) and rodents. Final hosts are predators such as dogs, cats, and man.Sarcocystosis: Infection of the striated muscle of mammals by parasites of the genus SARCOCYSTIS. Disease symptoms such as vomiting, diarrhea, muscle weakness, and paralysis are produced by sarcocystin, a toxin produced by the organism.Sarcocystidae: A family of parasitic organisms in the order EIMERIIDAE. They form tissue-cysts in their intermediate hosts, ultimately leading to pathogenesis in the final hosts that includes various mammals (including humans) and birds. The most important genera include NEOSPORA; SARCOCYSTIS; and TOXOPLASMA.Chagas Disease: Infection with the protozoan parasite TRYPANOSOMA CRUZI, a form of TRYPANOSOMIASIS endemic in Central and South America. It is named after the Brazilian physician Carlos Chagas, who discovered the parasite. Infection by the parasite (positive serologic result only) is distinguished from the clinical manifestations that develop years later, such as destruction of PARASYMPATHETIC GANGLIA; CHAGAS CARDIOMYOPATHY; and dysfunction of the ESOPHAGUS or COLON.Trypanosoma cruzi: The agent of South American trypanosomiasis or CHAGAS DISEASE. Its vertebrate hosts are man and various domestic and wild animals. Insects of several species are vectors.Anal Sacs: A pair of anal glands or sacs, located on either side of the ANUS, that produce and store a dark, foul-smelling fluid in carnivorous animals such as MEPHITIDAE and DOGS. The expelled fluid is used as a defensive repellent (in skunks) or a material to mark territory (in dogs).BrazilAnimals, Wild: Animals considered to be wild or feral or not adapted for domestic use. It does not include wild animals in zoos for which ANIMALS, ZOO is available.