Evaluation of the shedding of Sarcocystis falcatula sporocysts in experimentally infected Virginia opossums (Didelphis virginiana)

Five Virginia opossums (Didelphis virginiana) were fed muscles of brown-headed cowbirds (Molothrus ater) containing sarcocysts of Sarcocystis falcatula. Shedding of sporocysts was confirmed in all five opossums by fecal flotation. Counts were conducted daily for 2 weeks and then biweekly until the animals were euthanized and necropsied. The average prepatent period was 9.8 (7-16) days. The number of sporocysts shed varied greatly between the opossums with maximum mean shedding occurring at 71.6 (26-112) days post-infection (DPI). Average sporocyst production was 1480 sporocysts/gram of feces (SPG). Maximum output was 37,000 SPG. Average fecal yield in captivity was 17.5g of feces/day. Opossums shed 25,900 sporocysts/day (average) and a maximum of 647,500 sporocysts/day. All opossums shed sporocysts until time of euthanasia (46-200 DPI). Histologically, numerous sporocysts were present in the lamina propria at necropsy, primarily in the proximal half of the small intestine. Sporocysts were generally in clusters within the lamina propria of the luminal two-thirds of the villi. Sporocysts were found less frequently in the epithelium. No evidence of ongoing gametogony or other development was evident.     

Risk factors associated with the presence of Sarcocystis neurona sporocysts in opossums (Didelphis virginiana).

Sarcocystis neurona is the most important cause of equine protozoal myeloencephalitis (EPM) in horse in the Americas. The only known definitive host for this parasite in the United States is the opossum (Didelphis virginiana); however, despite the importance of the disease, the epidemiology of the parasite in the definitive host is poorly understood. To begin addressing these data gaps, potential risk factors were evaluated for their association with the presence of sporocysts of S. neurona in opossums live-trapped in March 1999 and November 1999 to May 2000. Sporocysts of S. neurona were found in 19 of the 72 animals examined. Potential risk factors evaluated were locality, trap date, age, gender, the presence of young in the pouch of females, and body condition score. Variables that were associated with the presence of S. neurona sporocysts were used in logistic regression analysis. Of the factors examined, season and body condition score were associated with increased odds of an animal harboring sporocysts.     

Prevalence of Sarcocystis neurona sporocysts in opossums (Didelphis virginiana) from rural Mississippi

Sarcocystis species sporocysts were found in intestinal scrapings from 24 of 72 opossums (Didelphis virginiana) from rural Mississippi. The number of sporocysts in each opossum varied from a few ( < 100000) to 187 million. Sporocysts from 24 opossums were bioassayed for Sarcocystis neurona infections by feeding to gamma-interferon knockout (KO) mice. S. neurona was detected in the brains of KO mice fed sporocysts from 19 opossums by immunohistochemical staining with anti-S. neurona specific polyclonal rabbit serum, and by in vitro culture from the brains of KO mice fed sporocysts. The isolates of S. neurona from opossums were designated SN16-OP to SN34-OP. Merozoites from 17 of 19 isolates tested at the 25/396 locus were identical to previously described S. neurona isolates from horses. The high prevalence of S. neurona sparocysts in D. virginiana suggests that this opossum constitutes an ample reservoir of infection in the southern United States.     

A retrospective study of 11 cases of lungworm (Didelphostrongylus hayesi) infection in opossums (Didelphis virginiana).

A juvenile, female North American opossum (Didelphis virginiana) died of verminous pneumonia caused by Didelphostrongylus haysei despite aggressive treatment with oral fenbendazole, corticosteroids, and antibiotics. This prompted a retrospective study of lungworm infection in opossums, during which 19 additional necropsy reports from opossums were reviewed. Including the subject of this report, a total of 11 (55%) of these cases included a diagnosis of lungworm infection. This diagnosis was considered to have contributed to death in eight out of the 11 cases (73%). Histologically, 10 of the 11 (91%) opossums had granulomatous bronchopneumonia with small to moderate numbers of adult nematodes in the airways and parenchyma. Four of the 11 (36%) opossums had free larvae within the parenchyma or terminal airways. Inflammation was usually associated with larvae, degenerating parasites, and nonintact adult nematodes. Superimposed bacterial pneumonia was evident in three animals, and sections of lung examined from all the opossums were characterized by moderate to severe smooth-muscle hyperplasia in airways, including terminal respiratory bronchioles and alveolar ducts. Nine animals had prominent medial smooth-muscle hyperplasia in small- and medium-sized arterioles. Lesions in other organs, particularly in liver, heart, and gastrointestinal tract, were frequently identified. Three animals had concomitant septicemia or bacterial bronchopneumonia (or both), which contributed to the cause of death. Seven animals had gastric nematodosis (Physaloptera sp.), although three of them had been treated with a 14-day course of fenbendazole.     

Sporocyst size of isolates of Sarcocystis shed by the Virginia opossum (Didelphis virginiana)

The Virginia opossum (Didelphis virginiana) is a definitive host for multiple Sarcocystis species including Sarcocystis neurona, one of the causative agents of equine protozoal myeloencephalitis (EPM), a severe, neuromuscular disease of horses. Size and morphologic characteristics of isolates of Sarcocystis shed by the opossum were examined to determine if differences were useful in discriminating between the isolates and/or species. Collections of sporocysts from 17 opossums were molecularly characterized and measured using an ocular micrometer. The mean sporocyst size of isolates of S. neurona was 10.7 microm x 7.0 microm, Sarcocystis falcatula 11.0 microm x 7.1 microm, Sarcocystis speeri 12.2 microm x 8.8 microm, 1085-like isolate 10.9 microm x 6.8 microm, and 3344-like isolate 19.4 microm x 10.5 microm. The length and width of S. speeri were statistically different (p < 0.05) from the sporocysts of other types. The length of S. neurona and S. falcatula sporocysts were statistically different (p < 0.05) from each other and the width of S. falcatula and 1085 differed (p < 0.05). The fifth sporocyst type (3344) was observed, but due to pronounced morphological characteristics, statistical analysis was not performed. There was no consistent difference between the taxa based on internal structure of the sporocyst.     

Prevalence and tissue distribution of Besnoitia darlingi cysts in the Virginia opossum (Didelphis virginiana) in Michigan

Specimens of Virginia opossums (Didelphis virginiana) in Michigan were examined over 1 year to document the presence of Besnoitia darlingi cysts. Cyst morphology, prevalence, seasonal variation, and tissue sites of isolation were studied. Histology and ultrastructural features of the detected cysts and bradyzoites were consistent with B. darlingi. In the opossums, B. darlingi had intracellular tissue cysts. Tissue cysts had a mean diameter of 560 microm and were separated from the host tissue by a thick (5-20 microm) cyst wall. Overall prevalence of B. darlingi cysts in opossums was 10.9% (15/137). Variations in the prevalence were detected during spring (3/17; 17.6%), summer (10/34; 29.4%), and fall (2/60; 3.3%). No cysts were detected in the specimens examined during winter (0/26; 0%). Numerous B. darlingi cysts were detected in ears, conjunctiva, tongue, abdominal muscles, diaphragm, stomach, heart, liver, kidney, lung, and spleen. Cysts were detected mainly in adult female opossums that were debilitated. Ear was the most frequent organ from which the cysts were reported (10/15; 66.7%) when compared individually with other body tissues (P<0.05).     

Opossum Nematodiasis: Diagnosis and Treatment of Stomach,Intestine, and Lung Nematodes in the Virginia Opossum (Didelphis virginiana)

Internal parasitic infections are common in the Virginia opossum (Didelphis virginiana). More than 50 different species of nematodes have been identified from the genus Didelphis. Of them, 3 can cause significant illness to native opossums in Southern California, 2 gastrointestinal nematodes and 1 pulmonary nematode. This article provides an overview of the life cycles, methods for identification, pathologic findings, diagnostic tests, clinical signs, and options for treating these common nematode species.     

Concurrent presence of Sarcocystis neurona sporocysts, Besnoitia darlingi tissue cysts, and Sarcocystis inghami sarcocysts in naturally infected opossums (Didelphis virginiana).

Opossums (Didelphis virginiana) are exposed to a wide range of coccidia through feeding on a variety of foods, including, but not limited to, carrion, insects, and nestling birds. Abundant D. virginiana populations in urban and suburban areas can be important reservoirs of parasitic infection because of their profuse and prolonged excretion of the sporocysts of several species of Sarcocystis, their omnivorous diet, and their relatively long life span. This report describes 2 adult female opossums found to be simultaneously infected with the tissue cysts of Besnoitia darlingi, sarcocysts of Sarcocystis inghami, as well as with the intestinal sporocysts of S. neurona. Cysts typical of B. darlingi based on gross, histological, and ultrastructural characteristics were disseminated throughout the visceral organs, musculature, ears, and skin. The S. neurona and B. darlingi infections were confirmed by comparative sequence analysis of polymerase chain reaction-amplified diagnostic genetic loci. Sarcocysts of S. inghami are also described. Such examples of multiple parasitic infections show that concurrent infections occur naturally. The propensity for species to coexist should be considered in the differential diagnosis of tissue cyst-forming coccidian protozoa and may have important epidemiological and evolutionary implications.     

Prevalence of antibodies against Toxoplasma gondii among Brazilian white-eared opossums (Didelphis albiventris)

Considering that Toxoplasma gondii is a parasite of global importance which affects several animal species including humans, the current study aimed to investigate the prevalence of antibodies against T. gondii among 72 white-eared opossums (Didelphis albiventris) from Botucatu Municipality (22°53'S 48°26'W), S?o Paulo State, Brazil. The investigation was carried out from January 2008 to December 2009, when the animals had their blood samples collected and subjected to the modified agglutination test (MAT); 12 specimens had brain samples bioassayed in mice. Seroprevalence was 5.5% (n=4) and bioassays were negative. Older animals had higher prevalence of antibodies against T. gondii. Opossums in closer contact with the urban environment are likely more exposed to T. gondii than animals from the sylvatic environment.     

Prevalence of and risk factors associated with the presence of Sarcocystis neurona sporocysts in opossum (Didelphis virginiana) from Michigan: a retrospective study

From April 1996 to December 2002 the prevalence of Sarcocystis neurona sporocysts in North American opossum (Didelphis virginiana) in Southern Michigan was estimated. Sporocysts of S. neurona were found in intestinal scrapings from 31 (15%) of 206 examined opossum. The frequency of infection was higher in adult animals (26/206; 12.6%) and females (19/206; 9.2%) than in juveniles (5/206; 2.4%) and males (12/206; 5.8%). Also, prevalence of S. neurona sporocysts in opossums in relation to factors such as age, sex, season, body condition, presence of concomitant infection, and presence of young in the pouch of females was studied in detail over the course of the year, 2002. Univariate analyses identified the following factors as being associated with the presence of S. neurona sporocysts in opossums: (i) for age, adult (odd ratio [OR] = 2.074, P = 0.0005); (ii) for sex, female (OR = 7.016, P = 0.0119); (iii) for season, summer (OR = 7.917, P = 0.0032) and spring (OR = 4.071, P = 0.1063); (iv) for body condition, poor (OR = 3.50, P = 0.1200) and good (OR = 1.167, P = 0.8637); (v) for the presence of concomitant infection (OR = 23.056, P = 0001), and (vi) for the presence of young in the pouch of females (OR = 40.083, P = 0.0001). Multivariate logistic-regression analyses selected the following factors as being significantly associated with presence of S. neurona sporocysts in opossums: (i) for the presence of concomitant infection (OR = 8.722, P = 0.0160) and (ii) for the presence of young in the pouch of females (OR = 31.915, P = 0.0065). The prevalence of S. neurona sporocysts in D. virginiana suggests that this opossum may constitute an ample reservoir of infection to other animals in the northern United States.     

Urinary Bladder incarceration and Infarction by an Intra-Abdominal Fat Pad in a Virginia Opossum (Didelphis Virginiana)

A 2.5-year-old, female opossum had acute stranguria. Based on radiography and ultrasonographic examination a cystic structure was identified in the caudal abdomen associated with bilateral hydroureter and hydronephrosis. This structure contained a neutrophilic fluid, determined to be urine. There was a neutrophilic leukocytosis. Serum chemistry values were within normal limits. The opossum was euthanized. An intra-abdominal fat pad incarceration of the urinary bladder above the trigone was present, resulting in complete obstruction of the urinary bladder and partial obstruction of the ureters. Vessels to the bladder were involved in the incarceration which resulted in vascular compromise and infarction of the bladder. Mild to moderate hydroureter and hydronephrosis were present.     

Light and electron microscopic features of eperythrozoon-like parasites in a North American opossum (Didelphis virginiana).

Epierythrocytic parasites associated with a severe anemic episode have not been previously reported in the opossum. A Wright-Giemsa-stained peripheral blood smear from an anemic North American opossum (Didelphis virginiana) revealed numerous organisms attached to red blood cells either singularly or in chains. Ring forms of the organism were common and could be found free in the plasma. Electron microscopy revealed that these organisms were attached to the intact plasma membrane in depressions on the surface of red blood cells. Delicate fibrils between the organism and adjacent membrane were observed. The organisms were round to oval with a diameter of 300-750 nm and were enclosed by a single limiting membrane. The light and electron microscopic features of these epierythrocytic organisms are similar to those reported for Eperythrozoon and Haemobartonella species.     

Hexamita meleagridis (Spironucleus meleagridis) infection in chukar partridges associated with high mortality and intracellular trophozoites

An outbreak of infectious catarrhal enteritis, associated with the flagellated protozoan Spironucleus meleagridis (syn. Hexamita meleagridis), is reported from a commercial flock of chukar partridges in California. The disease affected birds between the ages of 4 and 6 wk and resulted in diarrhea, listlessness, depression, and high mortality. Concurrent infection with other intestinal pathogens, including Cryptosporidia, group E Salmonella, long-segmented filamentous microorganisms (LSFMOs), and Rotavirus-like virus particles, was found in some but not all affected birds. Dermatitis of the face, shanks, and feet, suggestive of B-complex vitamin deficiency, was present in most affected birds as well. Flagellated protozoan parasites could be found in the lumen of the duodenum and jejunum and in the intestinal crypts. In some cases the flagellates were wedged between epithelial cells or were located intracellularly within cells of the mucosal epithelium and the intestinal lamina propria.     

Abomasal impaction associated with anorexia and mortality in lambs

Anorexia in forty-six (6.1%) out of 753 neonatal lambs was investigated. Thirty-five of these lambs (76.1%) died while eleven (23.9%) recovered after treatment. Coagulated rubber-like milk clots were found in fifteen (42.9%), phytobezoars in nine (25.7%) and trichophytobezoars and coarse straws in eleven (31.4%) of the dead lambs.     

Identifying agent(s) associated with poult enteritis mortality syndrome: importance of the thymus

Poult enteritis mortality syndrome (PEMS), a highly infectious disease of young turkeys, causes serious financial losses to the turkey industry. Clinically, PEMS is defined by mortality profiles, diarrhea, growth depression, and immunosuppression. Although many viruses, bacteria, and parasites are found in PEMS-infected birds, the inciting agent remains unknown. Experimentally, PEMS can be reproduced by exposing na?ve poults to the intestinal contents from infected birds. Previous reports suggest that extraintestinal tissues fail to reproduce the disease. Histopathologic examination of tissues from PEMS-infected poults suggested that the thymus exhibited the earliest signs of pathology. On the basis of these observations, we hypothesized that the thymus harbors an agent(s) involved in PEMS. In these studies, na?ve turkey poults were orally inoculated with a bacteria-free filtrate composed of either the intestines and feces or the thymus from PEMS-infected birds and were monitored for clinical signs of PEMS. Poults exposed to a filtrate composed solely of the thymus from PEMS-infected birds exhibited diarrhea, growth depression, mortality, pathology, and, most importantly, immunosuppression similar to poults exposed to the intestinal filtrate. The results of this study suggest that the thymus of infected birds harbors the agent(s) that can reproduce a PEMS-like disease in turkey poults.