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.

Didelphis aurita (Marsupialia: Didelphidae): a new host for Sarcocystis lindsayi (Apicomplexa: Sarcocystidae).

Nine opossums, Didelphis aurita , were captured in the city of Seropédica, State of Rio de Janeiro, Brazil and examined for species of Sarcocystis. Sporocysts were observed in the mucosal scrapings of the small intestine from 3 opossums. Five budgerigars, Melopsittacus undulatus , were infected with sporocysts from each of these infected opossums and 5 budgerigars were used as controls. Of the 15 sporocyst-treated budgerigars, 5 birds that received sporocysts from 1 of the infected opossums developed tissue parasites. Meronts in the vascular endothelium of the lung venous capillaries and cysts in the skeletal and cardiac muscle cells were observed in histological sections stained with hematoxylin and eosin. The microscopic cysts, which were predominantly in the tongue and leg muscles, ranged from 65.3 to 118.1 µm in length and 14.0 to 29.4 µm in width and from 0.9 to 1.9 µm in thickness of the cystic wall. Sections examined by transmission electron microscopy revealed that the cyst wall contained numerous slender and jagged-shaped protrusions, each with a finger-like formation at the end. The morphology, especially of the cyst wall, and the morphometry of the tissue cysts indicate that the parasite is Sarcocystis lindsayi and, therefore, the opossum, D. aurita , is now considered a definitive host for this species in Brazil.

Fine structure of the bird parasites Trichomonas gallinae and Tetratrichomonas gallinarum from cultures.

The trophozoites of Trichomonas gallinae and Tetratrichomonas gallinarum were studied by means of light and electron microscopy after cloning and cultivating them axenically. T. gallinae trophozoites varied in shape reaching from ovoidal to pyriform and had a size of about 7-11 microm. They were provided with four free flagella and a fifth recurrent one, which did not become free at the posterior pole. The nucleus was ovoid, had a size of about 2.5-3 microm, and was situated closely below the basal bodies of the flagella. The axostyle consisted of a row of microtubules running from the region of the apical basal bodies to the posterior end of the cell. In addition to flagellated stages, which contained food vacuoles, hydrogenosomes, a costa-like structure, and glycogen granules besides lacunes of endoplasmic reticulum, spherical, nonflagellated, and cyst-like stages occurred. The trophozoites of T. gallinarum appeared mostly pear-shaped and ranged in size from 6 to 15 microm. They had also four free anterior flagella and a fifth recurrent one, which became free at the posterior pole in contrast to that of T. gallinae. Another clearly visible difference to T. gallinae was the occurrence of a sphere of lacunes of the endoplasmic reticulum surrounding in a regular distance the nucleus with its typical perinuclear membranes. Furthermore, the food vacuoles appeared very large. However, both species clearly differed from the trophozoites of Histomonas meleagridis.

Sarcocystis lindsayi-like (Apicomplexa: Sarcocystinae) of the opossum (Didelphis aurita) from Southeastern Brazil.

Sporocysts of Sarcocystis were obtained from intestinal scrapings of three out of five opossums (Didelphis aurita) trapped in the southeastern region, of the State of Rio de Janeiro, Brazil. Fifteen caged budgerigars (Melopsittacus undulatus) received, orally, twenty-six sporocysts in 500 mL PBS, but only five belonging to one of the groups developed clinical signs, that consisted of anorexia, lethargy, ruffled feathers and dyspnoea, and parasitism in tissues. Two of the five budgerigars died on the 25th and 29th days after infection (DAI). The other three budgerigars were posted on the 30th DAI. In all the five infected birds were observed meronts in the capillaries of the lungs and cysts in muscles, mainly in the tongue and legs.