Lesions caused by Sarcocystis spp., parasites of opossums (Didelphis aurita), in acute and chronic infections in birds (Melopsittacus undulatus).

Protozoa of the genus Sarcocystis are obligatory heterogenous parasites with both definitive and intermediate hosts. Opossums (Didelphis aurita) can shed multiple species of Sarcocystis with birds as the intermediate host. The pathologies of Sarcocystis species in birds have not been thoroughly elucidated. Therefore, the aim of the present study to determine the main lesions that can occur in acute and chronic infections in intermediate hosts, when they ingest infective sporocysts that are shed in the opossum's feces, using budgerigars as a model. To this end, 12 budgerigars, Melopsittacus undulatus, were divided into two groups that received an inoculum with 60 and 120 sporocysts. Birds that died or were euthanized were necropsied, and the lung, tongue, liver, brain, heart, and skeletal striated muscles were collected and fixed in 10% formalin for histopathological analysis. The infectivity varied according to the sample and infective dose. Acute histopathological lesions were characterized by evidence of slightly degenerated hepatocyte cords that permeated the region of the blood vessel and hepatic sinusoids. Pulmonary tissue lesions were also observed in the parabronchial region with the presence of inflammatory infiltrates associated with areas of edema and atelectasis. In chronic infections, few mature cysts were observed in the chest, and many mature cysts in the thigh and tongue muscles. Thus, it was possible to conclude that lesions are highly characteristic in acute infection and, in chronic infections, cysts were present but without major lesions. In this case, the preferred organs of parasitism were the thigh and the tongue.

Identification of opossums Didelphis aurita (Wied-Neuweid, 1826) as a definitive host of Sarcocystis falcatula-like sporocysts.

This study was conducted to identify the Sarcocystis species that infect the opossum Didelphis aurita in order to determine which sporocysts they are excreating in to the environment and help determine the role of D. aurita in the epidemiology of Sarcocystis. Sporocysts were obtained from intestinal tracts of 8 of 13 D. aurita trapped in Rio de Janeiro state, Brazil, and were orally inoculated into Melopsittacus undulatus and Balb/c nude Mus musculus. Portions of organs and muscles were processed for histology, immunohistochemistry, transmission electron microscopy (TEM), and PCR using primers JNB 33/54, and ITS. Amplification products were subjected to RFLP using DraI and HinfI. Some birds were euthanized 6, 7, 13, 16, and 24 days after inoculation (DAI). All other birds and all mice were euthanized 60 DAI. Schizonts were observed in the lungs using histology and immunostaining in birds examined prior to 60 DAI. Sarcocysts with a ~ 1.5-µm-thick wall were found in the breast, thigh, and tongue of some birds. Sarcocystis asexual stages were isolated in cell cultures inoculated with sporozoites. Parasite DNA isolated from bird tissues and cell cultures demonstrated that S. falcatula-like parasites were present in all samples derived from positive opossums. Asexual stages molecularly characterized as S. lindsayi-like were isolated in cell culture from one opossum with an apparent multiple infection. This study demonstrated that D. aurita is a definitive host for S. falcatula-like parasites and indicates that S. lindsayi-like parasites can be found in coinfections of this opossum species.