Acute fulminant sarcocystosis in a captive-born rhesus macaque

Molecular detection of Sarcocystis sp. in a kept under human care black capuchin monkey (Sapajus nigritus., Goldfuss 1809) with necrotizing encephalitis

A senile male black capuchin monkey (Sapajus nigritus) kept under human care in a Zoo was found dead after 2 weeks presenting signals of weight loss and hyporexia. Histopathological revealed a necrotizing encephalitis. Although it was not observed microscopically, Sarcocystis sp infection was detected in brain tissue from molecular assays. These infections have been rarely described in neotropical primates, particularly associated with tissue lesions.

Pathologic characteristics of infectious diseases in macaque monkeys used in biomedical and toxicologic studies

Nonhuman primates (NHPs), which have many advantages in scientific research and are often the only relevant animals to use in assessing the safety profiles and biological or pharmacological effects of drug candidates, including biologics. In scientific or developmental experiments, the immune systems of animals can be spontaneously compromised possibly due to background infection, experimental procedure-associated stress, poor physical condition, or intended or unintended mechanisms of action of test articles. Under these circumstances, background, incidental, or opportunistic infections can seriously can significantly complicate the interpretation of research results and findings and consequently affect experimental conclusions. Pathologists and toxicologists must understand the clinical manifestations and pathologic features of infectious diseases and the effects of these diseases on animal physiology and experimental results in addition to the spectrum of infectious diseases in healthy NHP colonies. This review provides an overview of the clinical and pathologic characteristics of common viral, bacterial, fungal, and parasitic infectious diseases in NHPs, especially macaque monkeys, as well as methods for definitive diagnosis of these diseases. Opportunistic infections that can occur in the laboratory setting have also been addressed in this review with examples of cases of infection disease manifestation that was observed or influenced during safety assessment studies or under experimental conditions.

Chronic Polymyositis Associated with Disseminated Sarcocystosis in a Captive-born Rhesus Macaque

A 2–year-old, captive-born, clinically healthy male, rhesus macaque, was euthanatized as part of an experimental study. At necropsy, diffuse pale streaking of the trunk, lumbar, and limb muscles were noted macroscopically. On histology, numerous elongated cysts that contained crescent-shaped basophilic spores were found in the fibers of skeletal muscles. Scattered affected myofibers were degenerate and accompanied by eosinophilic-to-granulomatous inflammation. Sarcocysts had prominent villus-like projections with the morphology of a type 11 sarcocyst wall similar to Sarcocystis neurona but possessing many more villus microtubules than is reported for S. neurona. In addition, bradyzoites were very long, up to approximately 12 um in length. The protozoa were consistent with a Sarcocystis sp., based on histology and ultrastructure, however, a definitive identification of the species was not possible. Nonspecific immunohistochemical crossreaction with Sarcocystis cruzi antisera was observed. The 18S ribosomal deoxyribonucleic acid sequence showed 91% similarity to Sarcocystis hominis, 90% similarity to Sarcocystis buffalonis, and 89% similarity to Sarcocystis hirsuta. Interestingly, the ITSI sequence showed very little homology to any sequence in GenBank, suggesting that this is possibly a unique Sarcocystis sp. Sarcocystosis is often considered an incidental finding, particularly in wild-caught animals, with little clinical significance. However, as demonstrated in this report and others, disseminated sarcocystosis can occur in captive-born rhesus macaques with or without clinical signs. In some cases interference with research results can occur; including death in fulminant cases.

Sarcocystosis among wild captive and zoo animals in Malaysia

Sarcocystis sp. infection was investigated in 20 necropsied captive wild mammals and 20 birds in 2 petting zoos in Malaysia. The gross post-mortem lesions in mammals showed marbling of the liver with uniform congestion of the intestine, and for birds, there was atrophy of the sternal muscles with hemorrhage and edema of the lungs in 2 birds. Naked eye examination was used for detection of macroscopic sarcocysts, and muscle squash for microscopic type. Only microscopically visible cysts were detected in 8 animals and species identification was not possible. Histological examination of the sections of infected skeletal muscles showed more than 5 sarcocysts in each specimen. No leukocytic infiltration was seen in affected organs. The shape of the cysts was elongated or circular, and the mean size reached 254 x 24.5 µm and the thickness of the wall up to 2.5 µm. Two stages were recognized in the cysts, the peripheral metrocytes and large numbers of crescent shaped merozoites. Out of 40 animals examined, 3 mammals and 5 birds were positive (20%). The infection rate was 15% and 25% in mammals and birds, respectively. Regarding the organs, the infection rate was 50% in the skeletal muscles followed by tongue and heart (37.5%), diaphragm (25%), and esophagus (12.5%). Further ultrastructural studies are required to identify the species of Sarcocystis that infect captive wild animals and their possible role in zoonosis.

Overview of known non-human primate pathogens with potential to affect colonies used for toxicity testing

The increased demand for non-human primates (NHPs) in biomedical research has resulted in alternative sources of animals being used, which has allowed for importation of animals with varying background incidences of bacterial, viral, parasitic, and fungal pathogens. This can be of minimal consequence when animals from different sources are kept isolated. However, when NHPs from different sources with varying incidences of primary and opportunistic pathogens are mixed, there can be a rapid spread of these pathogens and an increase in the seroconversion of susceptible animals. If this process occurs during the conduct of a study, interpretation of that study can be confounded. Furthermore, NHPs imported from areas enzootic for pathogens such as Plasmodium or with high incidences of human diseases such as measles and tuberculosis can introduce diseases that can be a threat to colony health, have zoonotic risk, and can severely impact study outcome. Thus, knowledge of the common primary and opportunistic NHP infections, as well as reemerging pathogens, enables the toxicologist to use information on disease status for pre-study animal selection and intelligent study design. This is particularly important when immunomodulatory compounds are being investigated. Moreover, the toxicologic pathologist well versed in the common spontaneous infections, opportunistic pathogens, and background lesions in NHPs is able to assess possible drug-related effects in drug safety studies. This review identifies the common primary and opportunistic pathogens, as well as newly emerging infections of NHPs, that can directly or indirectly affect colony health and the interpretation of drug safety studies.

Sarcocystis and its complications in camels (Camelus dromedarius) of eastern provinces of Iran

The prevalence of Sarcocystis spp. was investigated by gross and histopathological examinations in 250 camels (Camelus dromedarius) slaughtered from 2002 to 2005 in the Mashhad Slaughterhouse, eastern Iran. Samples were taken from the diaphragm, heart, tongue, esophagus and masseter muscles for histopathological studies. No macroscopic sarcocysts were found in the samples at gross inspection. Sarcocysts were detected in 209 of 250 (83.6%) examined camels at histopathological level. The infection rate of the esophagus, heart, masseter muscles, diaphragm, and tongue was 58.8%, 48.0%, 46.8%, 41.6%, and 28.0%, respectively. There was no significant difference in the rate of infection between male (85.8%) and female (81.0%) camels. The tissue response to vital cysts was minimal; however, reaction to the degenerating cysts was severe and caused tissue damages resulting in hyperemia, hemorrhages, mononuclear cell infiltration, necrotic changes, and fibrosis. The wild and domestic carnivores especially dogs may be the final hosts of Sarcocystis spp. in this area.

Hemorrhagic disease in dogs infected with an unclassified intraendothelial piroplasm in southern Brazil

A hemorrhagic disease affecting dogs in Brazil, referred to popularly as "nambiuvú" (bloody ears) and believed to be transmitted by ticks, has been observed in animals infected with an organism described originally in 1910 as a piroplasm, and known locally as Rangelia vitalii. In this series of 10 cases, the disease was characterized by anaemia, jaundice, fever, spleno- and lymphadenomegaly, hemorrhage in the gastrointestinal tract, and persistent bleeding from the nose, oral cavity and tips, margins and outer surface of the pinnae. The ixodid ticks Rhipicephalus sanguineus and Amblyomma aureolatum infested affected dogs from suburban and rural areas, respectively. Laboratory findings included regenerative anaemia, spherocytosis, icteric plasma and bilirubinuria. Those intracellular organisms were found in bone marrow smears but not in blood smears. Microscopically, zoites were seen within the cytoplasm of blood capillary endothelial cells. Parasitized and non-parasitized endothelial cells were positive immunohistochemically for von Willebrand factor (vWF). Langhans-type multinucleate giant cells were observed in the lymph nodes and choroid plexus. There was prominent erythrophagocytosis by macrophages in the lymph node sinuses and infiltration of the medullary cords by numerous plasma cells. Ultrastructurally, this organism had an apical complex that included a polar ring and rhoptries but no conoid. This parasite was contained within a parasitophorous vacuole that had a trilaminar membrane with villar protrusions and was situated in the cytoplasm of capillary endothelial cells. This organism tested positive by immunohistochemistry for Babesia microti. This pathogen was also positive by in situ hybridization for B. microti. Tentative clinical diagnosis in these cases was based on the history, clinical picture, haemogram and favorable response to therapy, and confirmed through microscopic examination of smears from the bone marrow or histological sections of multiple tissues, especially lymph nodes where zoites were most frequently found. The disease was reproduced by intravenous inoculation of blood from a naturally infected dog into an experimental dog. The authors demonstrate in this study that this organism is a protozoa of the phylum Apicomplexa, order Piroplasmorida. This piroplasm seems to be different from Babesia since it has an intraendothelial stage. Molecular phylogenetic analysis is necessary to better characterize this parasite and clarify its taxonomic status.

Sarcocystis spp. in human infections

Sarcocystis species are intracellular protozoan parasites with an intermediate-definitive host life cycle based on a prey-predator relationship. Asexual stages develop in intermediate hosts after they ingest the oocyst stage from definitive-host feces and terminate with the formation of intramuscular cysts (sarcocysts). Sarcocysts in meat eaten by a definitive host initiate sexual stages in the intestine that terminate in oocysts excreted in the feces. Most Sarcocystis species infect specific hosts or closely related host species. For example, humans and some primates are definitive hosts for Sarcocystis hominis and S. suihominis after eating raw meat from cattle and pigs, respectively. The prevalence of intestinal sarcocystosis in humans is low and is only rarely associated with illness, except in volunteers who ingest large numbers of sarcocysts. Cases of infection of humans as intermediate hosts, with intramuscular cysts, number less than 100 and are of unknown origin. The asexual stages, including sarcocysts, can stimulate a strong inflammatory response. Livestock have suffered acute debilitating infections, resulting in abortion and death or chronic infections with failure to grow or thrive. This review provides a summary of Sarcocystis biology, including its morphology, life cycle, host specificity, prevalence, diagnosis, treatment, and prevention strategies, for human and food animal infections.