New Observations Allowing the Differentiation of Late Asexual Stages of Cystoisospora canis from Developing Microgamonts in the Intestines of Experimentally Infected Dogs

The coccidian parasite Cystoisospora canis (syn. Isospora canis) can cause clinical disease in dogs. Three generations of meronts are reported to occur in the small intestine of experimentally infected dogs before gametogony and oocyst formation. Oocyst excretion in the feces occurs at 9 to 11 days post-inoculation (PI). We examined the late asexual and sexual development of C. canis in 2 dogs necropsied 10 days after oral inoculation with 100,000 sporulated C. canis oocysts; both dogs had excreted oocysts 9 days PI. Asexual and sexual stages were seen in the lamina propria, throughout the small intestine in sections stained with hematoxylin and eosin from both dogs. In other studies of the C. canis life cycle, little attention has been given to distinguishing the last asexual generation of meronts and early microgamonts that can appear similar due to their stage of maturation and both having multiple nuclei. Here we report newly identified features of developing meronts and microgamonts and their distinction from each other by using sections processed using the periodic acid-Schiff (PAS) reaction. Using this method, we demonstrated that PAS-positive granules could be used to identify microgamonts and differentiate them from developing meront stages. These findings will aid pathologists and others in properly identifying coccidial parasites, in determining the cause of microscopic lesions in intestinal tissue, and in accurately identifying etiological agents.

Re-Evaluation of Asynchronous Asexual Development of Cystoisospora canis in Intestines of Dogs

The coccidian parasite Cystoisospora canis (syn. Isospora canis) can cause clinical disease in dogs. Three generation of schizonts have been reported in the small intestine of dogs before oocysts are excreted 9-11 days post inoculation (PI). Here, we re-evaluated asexual development of C. canis in 2 dogs necropsied 10 days after oral inoculation with 100,000 C. canis oocysts; both dogs had excreted oocysts 9 days PI. Asexual and sexual stages were seen in the lamina propria throughout the small intestine. Merozoites of different sizes were present, often in the same vacuole. They were arranged singly, in pairs, and many within a single parasitophorous vacuole. The maximum number of nuclei within developing merozoites in a group was 8, but it could not be discerned if they were individual nuclei or parts of merozoites. Findings of abundant asexual stages 1 day after dogs had started excreting oocysts indicated continued asexual multiplication beyond the prepatent period. The stages found resemble the 3 generations reported previously. The mode of division of the asexual generations remains unclear. The results of the present study indicate that there are many generations that are difficult to determine because of the multiplication of merozoites in the original host cell without leaving it to enter new host cells. From the literature, it is evident that cat and dog coccidia ( Cystoisospora spp.) divide by more than 1 type of division, including endodyogeny. In the past, the schizont/meront groups containing more than 1 generation have been called "cysts." However, cyst is not an accurate term because it is best used for an orally infective stage of coccidia; monozoic tissue cysts of C. canis can occur in paratenic hosts in extraintestinal organs. We recommend the term "types" as originally proposed for intestinal stages of Toxoplasma gondii and used for the original description of the life cycle of C. suis of swine when describing endogenous stages of the Sarcocystidae. Ultrastructural studies are needed to determine the precise form of multiplication of canine Cystoisospora species.

Sarcocystis strixi n. sp. from a Barred Owl ( Strix varia) Definitive Host and Interferon Gamma Gene Knockout Mice as Experimental Intermediate Host

Here we report a new species of Sarcocystis with a barred owl ( Strix varia) as the natural definitive host and interferon gamma gene knockout (KO) mice as an experimental intermediate host. A barred owl submitted to the Carolina Raptor Center, Huntersville, North Carolina, was euthanized because of paralysis. Fully sporulated 12.5 × 9.9 μm sporocysts were found in intestinal scrapings from the owl. Sporocysts from the barred owl were orally fed to 4 laboratory-reared outbred Swiss Webster (SW) ( Mus musculus) and 8 KO mice. All mice remained asymptomatic. Microscopic sarcocysts were found in all 5 KO mice euthanized on day 32, 59, 120, 154, and 206 post-inoculation (PI), not in KO mice euthanized on day 4, 8, and 14 PI. Sarcocysts were not found in any SW mice euthanized on day 72, 120, 206, and 210 PI. Sarcocysts were microscopic, up to 70 μm wide. By light microscopy, the sarcocyst wall < 2 μm thick had undulating, flat to conical, protrusions of varying dimensions. Numerous sarcocysts were seen in the histological sections of tongue and skeletal muscles from the abdomen, limbs, and eye but not in the heart. By transmission electron microscopy, the sarcocyst wall was "type 1j." The ground substance layer (gs) was homogenous, up to 2 μm thick, with very fine granules, and a few vesicles concentrated toward the villar projections. No microtubules were seen in the gs. Longitudinally cut bradyzoites at 206 days PI were 7.8 × 2.2 μm. Based on molecular characterization using 18S rRNA, 28S rRNA, and cox1 genes and morphology of sarcocysts, the parasite in the present study was biologically and structurally different from species so far described, and we therefore propose a new species name, Sarcocystis strixi n. sp.

Sarcocystis jamaicensis n. sp., from Red-Tailed Hawks (Buteo jamaicensis) Definitive Host and IFN-γ Gene Knockout Mice as Experimental Intermediate Host

Here, we report a new species of Sarcocystis with red-tailed hawk (RTH, Buteo jamaicensis) as the natural definitive host and IFN-γ gene knockout (KO) mice as an experimental intermediate host in which sarcocysts form in muscle. Two RTHs submitted to the Carolina Raptor Center, Huntersville, North Carolina, were euthanized because they could not be rehabilitated and released. Fully sporulated 12.5 × 9.9-μm sized sporocysts were found in intestinal scrapings of both hawks. Sporocysts were orally fed to laboratory-reared outbred Swiss Webster mice (SW, Mus musculus) and also to KO mice. The sporocysts were infective for KO mice but not for SW mice. All SW mice remained asymptomatic, and neither schizonts nor sarcocysts were found in any SW mice euthanized on days 54, 77, 103 (n = 2) or 137 post-inoculation (PI). The KO mice developed neurological signs and were necropsied between 52 to 68 days PI. Schizonts/merozoites were found in all KO mice euthanized on days 52, 55 (n = 3), 59, 61 (n = 2), 66, and 68 PI and they were confined to the brain. The predominant lesion was meningoencephalitis characterized by perivascular cuffs, granulomas, and necrosis of the neural tissue. The schizonts/merozoites were located in neural tissue and were apparently extravascular. Brain homogenates from infected KO mice were infective to KO mice by subcutaneous inoculation and when seeded on to CV-1 cells. Microscopic sarcocysts were found in skeletal muscles of 5 of 8 KO mice euthanized between 55-61 days PI. Only a few sarcocysts were detected. Sarcocysts were microscopic, up to 3.5 mm long. When viewed with light microscopy, the sarcocyst wall appeared thin (<1 μm thick) and smooth. By transmission electron microscopy, the sarcocyst wall classified as "type 1j" (new designation). Molecular characterization using 18S rRNA, 28S rRNA, ITS-1, and cox1 genes revealed a close relationship with Sarcocystis microti and Sarcocystis glareoli; both species infect birds as definitive hosts. The parasite in the present study was biologically and molecularly different from species so far described in RTHs and we therefore propose a new species name, Sarcocystis jamaicensis n. sp.

Sarcocystis pantherophisi n. sp., from Eastern Rat Snakes (Pantherophis alleghaniensis) as Definitive Hosts and Interferon Gamma Gene Knockout Mice as Experimental Intermediate Hosts

Here, we report a new species, Sarcocystis pantherophisi n. sp., with the Eastern rat snake (Pantherophis alleghaniensis) as natural definitive host and the interferon gamma gene knockout (KO) mouse as the experimental intermediate host. Sporocysts (n = 15) from intestinal contents of the snake were 10.8 × 8.9 μm. Sporocysts were orally infective to KO mice but not to laboratory-raised albino outbred house mice (Mus musculus). The interferon gamma KO mice developed schizont-associated neurological signs, and schizonts were cultivated in vitro from the brain. Mature sarcocysts were found in skeletal muscles of KO mice examined 41 days postinoculation (PI). Sarcocysts were slender, up to 70 μm wide and up to 3.5 mm long. By light microscopy, sarcocysts appeared thin-walled (<1 μm) without projections. By transmission electron microscopy, the sarcocyst wall was a variant of "type 1" (type 1i, new designation). The parasitophorous vacuolar membrane (pvm) had approximately 100-nm-wide × 100-nm-long bleb-like evaginations interspersed with 100-nm-wide × 650-nm-long elongated protrusions at irregular distances, and invaginations into the ground substance layer (gs) for a very short distance (6 nm). The gs was smooth, up to 500 nm thick, without tubules, and contained a few vesicles. Longitudinally cut bradyzoites at 54 days PI were banana-shaped, 7.8 × 2.2 μm (n = 5). Molecular characterization using 18S rRNA, 28S rRNA, ITS-1, and cox1 genes indicated a close relationship with other Sarcocystis parasites that have snake-rodent life cycles. The parasite in the present study was molecularly and biologically similar to a previously reported isolate (designated earlier as Sarcocystis sp. ex Pantherophis alleghaniensis) from P. alleghaniensis, and it was structurally different from other Sarcocystis species so far described.

Isolation, Culture and Cryopreservation of Sarcocystis species

More than 200 valid Sarcocystis species have been described in the parasitological literature. The developmental life cycle in the intermediate host and definitive host has only been described for a few species. Sarcocystis parasites are common pathogens infecting a wide range of animals, including humans, and this unit reviews the methods used for isolating infective stages of the parasite from both definitive and intermediate host(s), as well as methods used to initiate cultures from sporocysts and merozoites and for cryopreservation of various Sarcocystis spp. These methods are based on published reports and our experience with Sarcocystis species in cell culture over many years. The information presented is suitable for the efficient culture of many Sarcocystis species; however, some minor modifications may be needed based on the unique developmental patterns of some species. © 2017 by John Wiley & Sons, Inc.

Experimental transmission of Cystoisospora felis-like coccidium from bobcat (Lynx rufus) to the domestic cat (Felis catus)

Cystoisospora felis is an ubiquitous coccidian of cats. The domestic cat (Felis catus) is its definitive host and several mammalian and avian species are its optional intermediate/transport hosts. Nothing is known if it is transmissible to wild felids. In the present study C. felis-like oocysts were found in two naturally infected bobcats (Lynx rufus) from Pennsylvania. To study transmission of C. felis-like parasite from bobcats to domestic cats, sporulated oocysts of C. felis-like from one bobcat were orally inoculated into interferon gamma gene knockout (KO) mice, and 56 days later tissues of KO mice were fed to two coccidian-free cats; two littermate cats were uninoculated controls. The inoculated cats and controls were euthanized five and seven days later, and their small intestines were studied histologically. One inoculated cat excreted C. felis-like oocysts seven days post inoculation (p.i.) and was immediately euthanized. Mature schizonts, mature male and female gamonts, and unsporulated oocysts were found in the lamina propria of small intestine; these stages were morphologically similar to C. felis of domestic cats. No parasites were seen in histological sections of small intestines of the remaining three cats. The experiment was terminated at seven days p.i. (minimum prepatent period for C. felis) to minimize spread of this highly infectious parasite to other cats. Although oocysts of the parasite in bobcats were morphologically similar to C. felis of domestic cats, the endogenous stages differed in their location of development. The bobcat derived parasite was located in the lamina propria of ileum whereas all endogenous stages of C. felis of domestic cats are always located in enterocytes of intestinal epithelium. Characterization of DNA isolated from C. felis-like oocysts from the donor bobcat revealed that sequences of the ITS1 region was only 87% similar to the ITS1 region of C. felis from domestic cats. These results indicate that the parasite in bobcat is likely different than C. felis of cats.

Prevalence of IgG Antibodies to Toxoplasma gondii in Veterinary and Undergraduate Students at Virginia Tech, Blacksburg, Virginia

Toxoplasma gondii is a globally distributed parasitic protozoan that infects humans and other warm-blooded vertebrates. Felids are the only definitive host for T. gondii, and they excrete oocysts in their faeces. The national prevalence in humans is declining in the United States. This zoonotic organism is of particular interest due to its importance in pregnant women, in individuals with altered immune systems, and in reactivated ocular infections. Exposure to the parasite in humans is usually associated with consumption of raw or undercooked meat or by accidental ingestion of oocysts. It was hypothesized that veterinary students would have a greater chance at exposure to the parasite than an average population of undergraduate students due to increased contact with cats who are infected. A commercially available ELISA was used to examine serum samples from 336 students (252 veterinary students and 84 undergraduate students) at Virginia Polytechnic Institute and State University and the Virginia-Maryland Regional College of Veterinary Medicine for serum IgG antibodies to T. gondii antigen. The prevalence of T. gondii in these subjects was 5.6% in veterinary school students (n = 252) and 2.4% in undergraduates (n = 84). There was no significant difference (P > 0.05) in the prevalence of T. gondii antibodies in veterinary versus undergraduate students. The overall prevalence of 4.8% in all students in this study reflects the continuing decline of antibodies to T. gondii in humans in the United States.

Zoonotic protozoa in the marine environment: a threat to aquatic mammals and public health

This collection of abstracts provides an account of four presentations at the 19th International Conference of the World Association for the Advancement of Veterinary Parasitology (WAAVP)(held in New Orleans, LA, USA from 10–14 August 2003) in a symposium session on zoonotic protozoan parasites found in the marine environment and chaired by Ronald Fayer and David Lindsay.The focus was on three genera of parasites of veterinary and public health concern—Toxoplasma,Giardia, and Cryptosporidium with emphasis on their epidemiology in the marine environment.

Wild boars as sources for infectious diseases in livestock and humans

Wild boars (Sus scrofa) are indigenous in many countries in the world. These free-living swine are known reservoirs for a number of viruses, bacteria and parasites that are transmissible to domestic animals and humans. Changes of human habitation to suburban areas, increased use of lands for agricultural purposes, increased hunting activities and consumption of wild boar meat have increased the chances of exposure of wild boars to domestic animals and humans. Wild boars can act as reservoirs for many important infectious diseases in domestic animals, such as classical swine fever, brucellosis and trichinellosis, and in humans, diseases such as hepatitis E, tuberculosis, leptospirosis and trichinellosis. For examples, wild boars are reservoirs for hepatitis E virus, and cluster cases of hepatitis E have been reported in Japan of humans who consumed wild boar meat. In Canada, an outbreak of trichinellosis was linked to the consumption of wild boar meat. The incidence of tuberculosis owing to Mycobacterium bovis has increased in wild boars, thus posing a potential concern for infections in livestock and humans. It has also been documented that six hunters contracted Brucella suis infections from wild swine in Florida. This article discusses the prevalence and risk of infectious agents in wild boars and their potential transmission to livestock and humans.

Serological survey of Leishmania infantum and Trypanosoma cruzi in dogs from urban areas of Brazil and Colombia

Leishmania infantum and Trypanosoma cruzi are zoonotic parasites that are endemic throughout many parts of Latin America. Infected dogs play an important role in transmission of both parasites to humans. A serological survey of Leishmania and Trypanosoma infection was conducted on 365 dogs from São Paulo, Brazil and Bogatá, Colombia, South America. Serum samples were examined by the indirect immunofluorescent antibody test (IFAT). Anti-Leishmania IgG antibodies were detected in 5 of 107 from Brazil (4.7%) and in 4 of 258 dogs (1.6%) from Colombia. Titers ranged from 1:25 to 1:100. Anti-T. cruzi antibodies were not detected in any of the dogs from either Brazil or Colombia. The results show a low prevalence of anti-Leishmania antibodies and no antibodies against T. cruzi in these canine populations. Our study suggests that dogs play a limited role in the spread of L. infantum and T. cruzi in these urban areas of Brazil and Colombia.

Protozoal meningoencephalitis in sea otters (Enhydra lutris): a histopathological and immunohistochemical study of naturally occurring cases

Protozoal meningoencephalitis is considered to be an important cause of mortality in the California sea otter (Enhydra lutris). Thirty nine of 344 (11.3%) California (CA) and Washington state (WA) sea otters examined from 1985 to 2004 had histopathological evidence of significant protozoal meningoencephalitis. The aetiological agents and histopathological changes associated with these protozoal infections are described. The morphology of the actively multiplicative life stages of the organisms (tachyzoites for Toxoplasma gondii and merozoites for Sarcocystis neurona) and immunohistochemical labelling were used to identify infection with S. neurona (n=22, 56.4%), T. gondii (n=5, 12.8%) or dual infection with both organisms (n=12, 30.8%). Active S. neurona was present in all dual infections, while most had only the latent form of T. gondii. In S. neurona meningoencephalitis, multifocal to diffuse gliosis was widespread in grey matter and consistently present in the molecular layer of the cerebellum. In T. gondii meningoencephalitis, discrete foci of gliosis and malacia were more widely separated, sometimes incorporated pigment-laden macrophages and mineral, and were found predominantly in the cerebral cortex. Quiescent tissue cysts of T. gondii were considered to be incidental and not a cause of clinical disease and mortality. Protozoal meningoencephalitis was diagnosed more frequently in the expanding population of WA sea otters (10 of 31, 32.3%) than in the declining CA population (29 of 313, 9.3%). Among sea otters with protozoal meningoencephalitis, those that had displayed neurological signs prior to death had active S. neurona encephalitis, supporting the conclusion that S. neurona is the most significant protozoal pathogen in the central nervous system of sea otters.

Optimization of the use of C57BL/6 mice as a laboratory animal model for Neospora caninum vaccine studies

The development and testing of vaccines for Neospora caninum in mice require challenge studies to demonstrate a reduction in clinical signs or prevention of vertical transmission of the parasite after vaccination. Genetic susceptibility to N. caninum varies with the strain of mice. In this study, C57BL/6 mice were evaluated as a model for Neospora vaccine studies. A lethal challenge model was developed and the LD(50) was determined to be 1.5 x 10(7)N. caninum tachyzoites/mouse, delivered intraperitoneally. Brain lesions encountered in sections from sub-lethally challenged mice were scored on the basis of severity and total number of lesions to develop a histopathological scoring system for vaccine efficacy. A vertical transmission model for N. caninum vaccine studies was developed by studying mice that were infected either 2 weeks prior to mating or between days 12 and 14 of pregnancy. It was found that infection prior to mating reduced the average number of pups per litter. DNA extracted from fetal tissue was examined by a N. caninum specific polymerase chain reaction (PCR). The rate of vertical transmission was 0, 100 and 90.5% for the uninfected controls, mice infected during pregnancy and mice infected before mating, respectively. This study demonstrates that the C57BL/6 strain of mice is a good model for N. caninum vaccine studies because it is possible to establish a clear-cut lethal challenge model in C57BL/6 mice and they transmit the disease to their offspring efficiently.

Variation in Eimeria Oocyst Count and Species Composition in Weanling Beef Heifers

Rectal fecal samples were collected daily on 10 consecutive days in November 2004 from 11 weaned beef heifers to assess daily variation in fecal oocyst count and species composition. Subsequent samples were collected from the same animals on 15 April 2005 and 9 June 2005. Oocyst numbers were determined by the modified McMaster's test, and species were identified by examination of oocysts recovered with the Wisconsin sugar flotation technique. Soil samples were collected from the heifer pasture on 8 June 2005, and oocysts were quantified and identified to species. Mean fecal oocyst counts varied little at all sampling dates ranging from 134-377 oocysts/g. Ten Eimeria spp. were identified in fecal samples collected in November and April and 11 in June. Eimeria bovis was the most common species identified at all samplings. Mean species composition showed little variation during the 10-day sampling period in November, remained similar in April, and varied slightly in June. Twelve Eimeria spp. were identified in soil samples in proportions similar to those seen in fecal samples. The results indicate that clinically normal weanling beef heifers are likely to be infected with a diverse, but relatively stable, community of Eimeria spp.

Lack of Sarcocystis neurona antibody response in Virginia opossums (Didelphis virginiana) fed Sarcocystis neurona-infected muscle tissue

Serum was collected from laboratory-reared Virginia opossums (Didelphis virginiana) to determine whether experimentally infected opossums shedding Sarcocystis neurona sporocysts develop serum antibodies to S. neurona merozoite antigens. Three opossums were fed muscles from nine-banded armadillos (Dasypus novemcinctus), and 5 were fed muscles from striped skunks (Mephitis mephitis). Serum was also collected from 26 automobile-killed opossums to determine whether antibodies to S. neurona were present in these opossums. Serum was analyzed using the S. neurona direct agglutination test (SAT). The SAT was modified for use with a filter paper collection system. Antibodies to S. neurona were not detected in any of the serum samples from opossums, indicating that infection in the opossum is localized in the small intestine. Antibodies to S. neurona were detected in filter-paper-processed serum samples from 2 armadillos naturally infected with S. neurona.

Vaccination with gamma-irradiated Neospora caninum tachyzoites protects mice against acute challenge with N. caninum

Neospora caninum, an apicomplexan parasite, is a leading cause of bovine abortions worldwide. The efficacy of gamma-irradiated N. caninum strain NC-1 tachyzoites as a vaccine for neosporosis was assessed in C57BL6 mice. A dose of 528 Gy of gamma irradiation was sufficient to arrest replication but not host cell penetration by tachyzoites. Female C57BL6 mice were vaccinated with two intraperitoneal inoculations of 1 x 10(6) irradiated tachyzoites at 4-wk intervals. When stimulated with N. caninum tachyzoite lysates, splenocytes of vaccinated mice, cultured 5 and 10 wk after vaccination, secreted significant (P<0.05) levels of interferon gamma, interleukin (IL)-10, and small amounts of IL-4. Antibody isotype-specific ELISA of sera from vaccinated mice exhibited both IgG1 and IgG2a isotypes of antibodies. Vaccinated mice were challenged intraperitoneally with 2 x 10(7)N. caninum tachyzoites. All vaccinated mice remained healthy and showed no obvious signs of neosporosis up to the 25th day post-challenge when the study was terminated. All unvaccinated control mice died within 1 wk of infection. Gamma-irradiated N. caninum tachyzoites can serve as an effective, attenuated vaccine for N. caninum.

Utility of diagnostic tests used in diagnosis of infection in dogs experimentally inoculated with a North American isolate of Leishmania infantum infantum

Eight female beagles were infected with 1 x 10(7) (low dose, LD) or 2 x 10(8) (high dose, HD) promastigotes of a North American isolate of Leishmania infantum infantum (LIVT-1 strain) isolated from naturally infected Virginia Foxhounds. Two female beagles served as negative controls and 2 male beagles chronically infected (> 3 years) with Leishmania infantum chagasi were positive controls. Bone marrow (BM) and lymph node (LN) aspirates were collected every 6-8 weeks for cytologic evaluation, parasite culture, and polymerase chain reaction (PCR). Serum samples were collected monthly for determination of serologic responses by indirect fluorescent antibody test (IFAT) and diagnostic rK39 antigen. Cultures of BM and LN aspirates and cytology evaluation were consistently positive in positive control dogs during the course of study. Negative control dogs were negative on BM and LN cultures and on cytologic evaluation of aspirates. Amastigotes were present on cytological examination of BM aspirates in 2 experimentally infected dogs. Cultures of LN aspirates were positive on 22 samples, whereas BM cultures were positive on 12 samples for all dogs. IFA titers ranged from 0 to 1 :400 in experimentally infected dogs during the course of the study. Recombinant K39 immunoassay tests were consistently positive in positive control dogs and in the HD dogs by approximately 8 weeks after infection. BM PCR products were identified more consistently in the HD dogs compared with the LD dogs. Kappa statistics indicated PCR correlated better with cultures and cytology than did IFAT or the rK39 immunoassay results in the experimentally infected dogs.

Experimental infection of ponies with Sarcocystis fayeri and differentiation from Sarcocystis neurona infections in horses

Sarcocystis neurona and Sarcocystis fayeri infections are common in horses in the Americas. Their antemortem diagnosis is important because the former causes a neurological disorder in horses, whereas the latter is considered nonpathogenic. There is a concern that equine antibodies to S. fayeri might react with S. neurona antigens in diagnostic tests. In this study, 4 ponies without demonstrable serum antibodies to S. neurona by Western immunoblot were used. Three ponies were fed 1 x 10(5) to 1 x 10(7) sporocysts of S. fayeri obtained from dogs that were fed naturally infected horse muscles. All ponies remained asymptomatic until the termination of the experiment, day 79 postinoculation (PI). All serum samples collected were negative for antibodies to S. neurona using the Western blot at the initial screening, just before inoculation with S. fayeri (day 2) and weekly until day 79 PI. Cerebrospinal fluid samples from each pony were negative for S. neurona antibodies. Using the S. neurona agglutination test, antibodies to S. neurona were not detected in 1:25 dilution of sera from any samples, except that from pony no. 4 on day 28; this pony had received 1 X 10(7) sporocysts. Using indirect immunofluorescence antibody tests (IFATs), 7 serum samples were found to be positive for S. neurona antibodies from 1:25 to 1:400 dilutions. Sarcocystis fayeri sarcocysts were found in striated muscles of all inoculated ponies, with heaviest infections in the tongue. All sarcocysts examined histologically appeared to contain only microcytes. Ultrastructurally, S. fayeri sarcocysts could be differentiated from S. neurona sarcocysts by the microtubules (mt) in villar protrusions on sarcocyst walls; in S. fayeri the mt extended from the villar tips to the pellicle of zoites, whereas in S. neurona the mt were restricted to the middle of the cyst wall. Results indicate that horses with S. fayeri infections may be misdiagnosed as being S. neurona infected using IFAT, and further research is needed on the serologic diagnosis of S. neurona infections.

Biologic, morphologic, and molecular characterisation of Neospora caninum isolates from littermate dogs

Isolation and biologic and molecular attributes of Neospora caninum from three littermate dogs are described. Tissue cysts were confined to the brain and striated muscles. N. caninum was isolated (isolates NC-6, NC-7, and NC-8) in rodents and cell culture that had been inoculated with brain tissue from the dogs. Schizont-like stages reactive with N. caninum antibodies were seen in cell cultures seeded with bradyzoites released from Percoll-isolated N. caninum tissue cysts from the brain of one dog. Tissue cysts were infective orally to mice and gerbils, but not to cats and dogs. The isolates were also identified as N. caninum by PCR and sequence analysis.

Neosporosis

Neospora caninum is a recently recognized protozoan parasite of animals, which, until 1988, was misdiagnosed as Toxoplasma gondii. Neospora caninum or Neospora-like parasites, here discussed by J.P. Dubey and David Lindsay, cause paralysis and death in dogs and neonatal mortality and abortion in cattle, sheep, goats and horses.

Molecular and Biological Characterization of Hammondia heydorni–Like Oocysts From a Dog Fed Hearts From Naturally Infected White-Tailed Deer (Odocoileus virginianus)

Neospora caninum and Hammondia heydorni are morphologically and phylogenetically related coccidians that are found in dogs. Although there is serological evidence of N. caninum infection in the white-tailed deer (Odocoileus virginianus), the parasite has not been yet isolated from the tissues of this host. In an attempt to isolate N. caninum from deer, hearts from 4 deer with antibodies to N. caninum were fed to 2 dogs. One of these dogs shed unsporulated oocysts 12-14 microm in diameter. Sporulated oocysts were not infective to Mongolian gerbils (Meriones ungulatus), and DNA isolated from these oocysts was not amplified using N. caninum-specific primers. However, positive amplification with the H. heydorni-specific first internal transcribed spacer (ITS-1) primers and common toxoplasmatiid ITS-1 primers confirmed the presence of H. heydorni DNA in the samples. The oocysts were considered to be H. heydorni on the basis of their morphology, biology, and molecular characteristics. This is the first record of a H. heydorni-like parasite in the white-tailed deer.

Effect of hydrogen peroxide and other protease inhibitors on Cryptosporidium parvum excystation and in vitro development

This study was undertaken to observe the effects of hydrogen peroxide on Cryptosporidium parvum oocysts with respect to protease activity in comparison to known protease inhibitors. In assessing the possible mechanisms of action of hydrogen peroxide, treatment effectiveness was analyzed using 3 assays and the potential roles of proteases and cations were considered. Treatment of C. parvum oocysts with hydrogen peroxide inhibited protease activity up to 50% compared with untreated controls. Treatment of oocysts with chemicals that affect sulfhydryls, including N-ethylmaleimide and dithiolthreitol, inhibited protease activity by >90%. Treatment of oocysts with these chemicals, along with the protease inhibitors, phenylmethylsulfonyl fluoride (PMSF), ethylenediamine-tetraacetic acid, and cystatin, inhibited protease activity as well as in vitro excystation and infection in a cell culture assay. Several mechanisms may result in the successful inhibition of infection and excystation by hydrogen peroxide treatment, including: oxidation of oocyst wall proteins or lipids, chelating of cations necessary for infection, or hydroxyl radical-induced DNA damage to sporozoites, or both.

Hammondia heydorni: evidence of genetic diversity among isolates from dogs

Canine isolates of Hammondia heydorni from Argentina, Brazil, and the United States were analysed for genetic diversity. A total of 14 isolates were tested for their ability to produce amplification using three PCR assays, one targeting the common toxoplasmatiid ITS-1 region and 2 amplifying novel, H. heydorni-specific loci, HhAP7 and HhAP10. While the ITS-1 fragments could be amplified from all isolates, only six isolates were capable of amplifying the fragments from the novel loci. The PCR products were further investigated for genetic diversity using restriction fragment length polymorphism (RFLP) and single strand conformation polymorphism (SSCP) techniques. Polymorphism in the digestion pattern was evident only at the HhAP10 locus, differentiating two of the Argentinean isolates from the remainder. Mobility shifts on SSCP gels revealed that the two Argentinean isolates were not only different from the other four isolates, but also differed from each other, both at the HhAP7 and HhAP10 loci. The ITS-1 fragments of all isolates were identical by RFLP. However, two distinct mobility patterns resulted when the products were electrophoresed on SSCP gels. Based on the sequence data from the ITS-1 and the two random loci, the isolates could be broadly classified into two distinct groups, within which minor polymorphisms were evident. In contrast, very little heterogeneity occurred in the sequences of corresponding ITS-1 regions of Neospora caninum and Toxoplasma gondii isolates. Thus, it is concluded that there is a considerable degree of microheterogeneity among isolates of H. heydorni. This diversity should be taken into consideration while attempting to elucidate the systematics, diagnostics, and biology of H. heydorni in relation to N. caninum.

Epidemiology of Sarcocystis neurona infections in domestic cats (Felis domesticus) and its association with equine protozoal myeloencephalitis (EPM) case farms and feral cats from a mobile spay and neuter clinic

Equine protozoal myeloencephalitis (EPM) is a serious neurologic disease in the horse most commonly caused by Sarcocystis neurona. The domestic cat (Felis domesticus) is an intermediate host for S. neurona. In the present study, nine farms, known to have prior clinically diagnosed cases of EPM and a resident cat population were identified and sampled accordingly. In addition to the farm cats sampled, samples were also collected from a mobile spay and neuter clinic. Overall, serum samples were collected in 2001 from 310 cats, with samples including barn, feral and inside/outside cats. Of these 310 samples, 35 were from nine horse farms. Horse serum samples were also collected and traps were set for opossums at each of the farms. The S. neurona direct agglutination test (SAT) was used for both the horse and cat serum samples (1:25 dilution). Fourteen of 35 (40%) cats sampled from horse farms had circulating S. neurona agglutinating antibodies. Twenty-seven of the 275 (10%) cats from the spay/neuter clinic also had detectable S. neurona antibodies. Overall, 115 of 123 (93%) horses tested positive for anti-S. neurona antibodies, with each farm having greater than a 75% exposure rate among sampled horses. Twenty-one opossums were trapped on seven of the nine farms. Eleven opossums had Sarcocystis sp. sporocysts, six of them were identified as S. neurona sporocysts based on bioassays in gamma-interferon gene knockout mice with each opossum representing a different farm. Demonstration of S. neurona agglutinating antibodies in domestic and feral cats corroborates previous research demonstrating feral cats to be naturally infected, and also suggests that cats can be frequently infected with S. neurona and serve as one of several natural intermediate hosts for S. neurona.

Detection of Hammondia heydorni-like organisms and their differentiation from Neospora caninum using random-amplified polymorphic DNA-polymerase chain reaction

Neospora caninum and Hammondia heydorni are morphologically and phylogenetically related coccidians that are found in dogs. New diagnostic genetic loci, based on random-amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR), were developed to aid in the detection of H. heydorni-like parasites and to discriminate them from N. caninum and other related coccidians of dogs. On the basis of the data obtained from 5 random decamers, H. heydorni (Manhattan-1) and N. caninum (NC1) were characterized by distinct banding patterns (similarity index = 0.068). High-stringency PCR assays were developed from the sequences of 2 cloned bands (GenBank BZ592549 and BZ592593), uniquely amplified from H. heydorni. Interestingly, using these primers, PCR amplification was achieved only from 2 of the 5 isolates presumed to represent H. heydorni. The same result was obtained from these 5 isolates using a recently described PCR assay directed to the H. heydorni internal transcribed spacer-1. It is concluded that H. heydorni and N. caninum are genetically distinct and that such tools may be useful for more detailed characterization of the diversity of related parasites occurring in dogs.

Prevalence of antibodies to Neospora caninum, Sarcocystis neurona, and Toxoplasma gondii in wild horses from central Wyoming

Sarcocystis neurona, Neospora caninum, N. hughesi, and Toxoplasma gondii are 4 related coccidians considered to be associated with encephalomyelitis in horses. The source of infection for N. hughesi is unknown, whereas opossums, dogs, and cats are the definitive hosts for S. neurona, N. caninum, and T. gondii, respectively. Seroprevalence of these coccidians in 276 wild horses from central Wyoming outside the known range of the opossum (Didelphis virginiana) was determined. Antibodies to T. gondii were found only in 1 of 276 horses tested with the modified agglutination test using 1:25, 1:50, and 1:500 dilutions. Antibodies to N. caninum were found in 86 (31.1%) of the 276 horses tested with the Neospora agglutination test--the titers were 1:25 in 38 horses, 1:50 in 15, 1:100 in 9, 1:200 in 8, 1:400 in 4, 1:800 in 2, 1:1,600 in 2, 1:3,200 in 2, and 1:12,800 in 1. Antibodies to S. neurona were assessed with the serum immunoblot; of 276 horses tested, 18 had antibodies considered specific for S. neurona. Antibodies to S. neurona also were assessed with the S. neurona direct agglutination test (SAT). Thirty-nine of 265 horses tested had SAT antibodies--in titers of 1:50 in 26 horses and 1:100 in 13. The presence of S. neurona antibodies in horses in central Wyoming suggests that either there is cross-reactivity between S. neurona and some other infection or a definitive host other than opossum is the source of infection. In a retrospective study, S. neurona antibodies were not found by immunoblot in the sera of 243 horses from western Canada outside the range of D. virginiana.

Development and ultrastructure of Besnoitia oryctofelisi tachyzoites, tissue cysts, bradyzoites, schizonts and merozoites

Development and structure of different life cycle stages of Besnoitia oryctofelisi which has a rabbit-cat life cycle was studied by light and transmission electron microscopy. For light microscopy, Besnoitia oryctofelisi-infected tissues were stained with haematoxylin-eosin, periodic acid Schiff (PAS) reagent, and immunohistochemically with rabbit anti-B. oryctofelisi polyclonal antibodies and anti-BAG-1 antibodies. In vitro and in vivo-derived tachyzoites were 5-6 microm long and they were found to divide by endodyogeny. In tachyzoites, the nucleus was often central, and micronemes were few and located anterior to the nucleus. Earliest tissue cysts were seen in gerbils starting 12 days p.i. Early tissue cysts had an outer PAS-positive cyst wall, a middle PAS-negative host cell layer, and an inner PAS-negative parasitophorous vacuolar membrane. Organisms in early tissue cysts were PAS-negative, did not stain with anti-BAG-1 antibodies, and amylopectin granules and enigmatic bodies were absent. Tissue cysts beginning 17 days p.i. contained organisms that became PAS-positive and reacted with anti-BAG-1 antibodies, indicating they were bradyzoites. Immunoreactivity with polyclonal anti-B. oryctofelisi antibodies suggested that Besnoitia species bradyzoites are encapsulated by the host cell. Bradyzoites (10 microm) were about twice the length of tachyzoites and contained enigmatic bodies characteristic of Besnoitia bradyzoites. Unlike tachyzoites and tissue cysts, schizonts were located intravascularly in the lamina propria of the small intestine of cats. Merozoites were 5-6 microm long, had few rhoptries and amylopectin granules, had numerous micronemes and had a terminal nucleus.

Biological and molecular characterization of Besnoitia akodoni n.sp. (Protozoa: Apicomplexa) from the rodent Akodon montensis in Brazil

The diversity among coccidian parasites of the genus Besnoitia is incompletely known. Of the eight currently described members of the genus, only B. jellisoni is known to parasitize a rodent host. Here, we propose a new name, Besnoitia akodoni, for the species initially isolated form the rodent Akodon montensis in Brazil. The tissue cysts of B. akodoni were up to 442 microm in diameter and bradyzoites were 8.4 x 1.4 microm in size. The bradyzoites contained enigmatic bodies, micronemes and rhoptries. Tachyzoites were 5.8 x 1.5 microm in size and they could be grown in vitro in bovine monocytes and African Green monkey cells where they divided by endodyogeny. Besnoitia akodoni was infective to laboratory-raised mice (Mus musculus) and gerbils (Meriones unguiculatus) but not to cats (Felis catus). Comparison of the conserved sequences of the small subunit rDNA clearly established the close relationship of B. akodoni with other members of the genus. However, sequences of the more variable first internal transcribed spacer portion of the ribosomal DNA repeat support its differentiation from the other species of the genus.

Besnoitia oryctofelisi n. sp. (Protozoa: Apicomplexa) from domestic rabbits

A species of Besnoitia from naturally infected rabbits from Argentina was propagated experimentally in mice, gerbils, rabbits, cats, and cell cultures. Cats fed tissue cysts from rabbits shed oocysts with a prepatent period of nine to 13 days. Sporulated oocysts were infective to gerbils, rabbits, outbred Swiss Webster and interferon gamma gene knockout mice. Bradyzoites were infective orally to gerbils and cats. Tachyzoites were successfully cultivated and maintained in vitro in bovine monocytes and African green monkey kidney cells. Schizonts were seen in the lamina propria of the small intestine of cats fed tissue cysts; the largest ones measured 52 x 45 microm. Schizonts were also present in mesenteric lymph nodes, livers, and other extra-intestinal organs of cats fed tissue cysts. Oocysts were 10-14 x 10-13 microm in size. This rabbit-derived species of Besnoitia resembled B. darlingi of the North American opossum, Didelphis virginiana with an opossum-cat cycle, but it was not transmissible to D. virginiana, and B. darlingi of opossums was not transmissible to rabbits. Based on biological, serological, antigenic, and molecular differences between the rabbit and the opossum Besnoitia, a new name, B. oryctofelisi is proposed for the parasite from domestic rabbits from Argentina.

Sarcocysts of an unidentified species of Sarcocystis in the sea otter (Enhydra lutris)

The number of Sarcocystis species that infect sea otters (Enhydra lutris) is unknown. Sea otter tissues were recently shown to harbor sarcocysts of S. neurona and of unidentified species of Sarcocystis. Whereas sarcocysts of S. neurona have walls 1-3 microm thick with type 9 villar protrusions, ultrastructure of a distinct thin-walled sarcocyst (0.5-0.7 microm thick) lacking villar protrusions, but instead exhibiting minute type 1 undulations on the sarcocyst wall, is described in this report. Parasites characterized from a sea otter infection were inferred to be related to, but distinct from, other species belonging to Sarcocystis, based on sequencing and phylogenetic analysis of a portion of the beta subunit of the plastid-encoded RNA polymerase gene.

Reactivity against Sarcocystis neurona and Neospora by serum antibodies in healthy French horses from two farms with previous equine protozoal myeloencephalitis-like cases

Sarcocystis neurona is considered a leading cause of equine protozoal myeloencephalitis (EPM), a common infectious neurological disease in horses in the Americas. EPM-like cases associated with S. neurona peptide reactive antibodies in Western blots were recently described in Normandy, France. In this report, antibodies reacting with S. neurona merozoites were detected using an agglutination assay at titers ranging from 50 to 500 in sera from 18/50 healthy horses from two farms with a previous EPM-like case. Higher values were found in older animals. Four out of six horses which traveled or stayed in the US exhibited titers over 50, a higher figure than in the group which did not travel out of France or stayed in an other European country. No correlation was found between anti-S. neurona and anti-Neospora sp. antibody titers. Data prompt further study of significance of anti-S. neurona antibodies in clinically healthy or diseased European horses, and identification of putative immunizing parasite(s) and their host(s).

Prevalence of antibodies to Neospora caninum and Sarcocystis neurona in sera of domestic cats from Brazil

Parasite Biology, Epidemiology and Systematics Laboratory, Animal and Natural Resources Institute, Agricultural Research Service, United States Department of Agriculture, Building 1001, Beltsville, Maryland 20705-2350 Antibodies to Neospora caninum and Sarcocystis neurona were determined in serum samples of 502 domestic cats from Brazil using direct agglutination tests with the respective antigens. Antibodies to S. neurona were not found in 1:50 dilution of any serum in the S. neurona agglutination test. suggesting that domestic cats from São Paulo city were not exposed to S. neurona sporocysts from opossums. Antibodies to N. caninum were found in 60 (11.9%) of 502 cats with titers of 1:40 in 36 cats, 1:80 in 18 cats, 1:160 in 5 cats, and 1:800 in 1 cat using the Neospora agglutination test (NAT). Antibodies to N. caninum were confirmed by Western blotting in the sera of 10 cats with NAT titers of 1:80 to 1:800; this finding suggests that at least 10 cats had N. caninum-specific antibodies confirmed by 2 tests. This is the first documentation of natural exposure of cats to N. caninum.

Life cycle of Sarcocystis neurona in its natural intermediate host, the raccoon, Procyon lotor

Sarcocystis neurona causes encephalomyelitis in many species of mammals and is the most important cause of neurologic disease in the horse. Its complete life cycle is unknown, particularly its development and localization in the intermediate host. Recently, the raccoon (Procyon lotor) was recognized as a natural intermediate host of S. neurona. In the present study, migration and development of S. neurona was studied in 10 raccoons that were fed S. neurona sporocysts from experimentally infected opossums; 4 raccoons served as controls. Raccoons were examined at necropsy 1, 3, 5, 7, 10, 14, 15, 22, 37, and 77 days after feeding on sporocysts (DAFS). Tissue sections of most of the organs were studied histologically and reacted with anti-S. neurona-specific polyclonal rabbit serum in an immunohistochemical test. Parasitemia was demonstrated in peripheral blood of raccoons 3 and 5 DAFS. Individual zoites were seen in histologic sections of intestines of raccoons euthanized 1, 3, and 5 DAFS. Schizonts and merozoites were seen in many tissues 7 to 22 DAFS, particularly in the brain. Sarcocysts were seen in raccoons killed 22 DAFS. Sarcocysts at 22 DAFS were immature and seen only in skeletal muscle. Mature sarcocysts were seen in all skeletal samples, particularly in the tongue of the raccoon 77 DAFS; these sarcocysts were infective to laboratory-raised opossums. This is the first report of the complete development of S. neurona schizonts and sarcocysts in a natural intermediate host.

Immunohistochemistry based assay to determine the effects of treatments on Cryptosporidium parvum viability

Cell culture infectivity assays can provide an accurate means of detecting viable Cryptosporidium parvum oocysts from environmental samples or to test the effects of various treatments on oocyst infectivity. Cell culture assays can also be used to test candidate chemotherapeutic agents. The use of a human cell line provides a situation close to human infection. The present assay uses an anti-Cryptospordium primary antibody, combined with a biotinylated secondary antibody, and an immunoperoxidase detection system. Cryptosporidium parvum oocysts excysted in vitro when placed on monolayers of HCT-8 cells and developmental stages including schizonts and merozoites were visualized using light microscopy of the immunoperoxidase stained slides and by transmission electron microscopy of infected HCT-8 cell cultures. Because the immunoperoxidase system used gives a permanent preparation, the cell cultures can be retained and examined later. Dose titration of oocysts indicated that as few as 50 inoculated oocysts could be detected. The activity of paromomycin was evaluated in this system and 500 microg/ml produced a 97.8% reduction in infection.

Removal of Toxoplasma gondii oocysts from sea water by eastern oysters (Crassostrea virginica)

Toxoplasma gondii infections have been reported in a number of marine mammals. Presently it is not known how these animals acquire T. gondii from their aquatic environment. The eastern oyster, Crassostrea virginica, has been shown to remove Cryptosporidiwn oocysts from seawater and a similar phenomenon may be occurring with T. gondii oocysts and marine invertebrates. The present study was done to determine if eastern oysters could remove and retain T. gondii oocysts from seawater. Oocysts of the VEG strain of T. gondii (1 x 10(6) oocysts) were placed in seawater (32 ppt NaCl) containing live eastern oysters. The infected seawater was removed one day postinoculation (PI) and replaced with fresh seawater. Selected oysters were removed at 1, 3 and 6 days PI. Hemolymph, gill washes, and oyster tissue were collected separately at each observation time. The oyster tissue was homogenized and all 3 samples fed separately to mice. Toxoplasma gondii positive mice were observed at each time period. The results indicate that T. gondii oocysts can be removed from seawater by eastern oysters and retain their infectivity. Contaminated raw oysters may serve as a source of T. gondii infection for marine mammals and humans.

Serologic responses of cats against experimental Sarcocystis neurona infections

Sarcocystis neurona is the most important cause of a neurologic disease of horses, equine protozoal myeloencephalitis (EPM). Cats and other carnivores can act as its intermediate hosts and horses are aberrant hosts. Little is known of the sero-epidemiology of S. neurona infections in cats. In the present study, antibodies to S. neurona were evaluated by the S. neurona agglutination test (SAT). Cats fed sporocysts from the feces of naturally infected opossums or inoculated intramuscularly with S. neurona merozoites developed high levels (> or =1:4000) of SAT antibodies. Antibodies to S. neurona were not found in a cat inoculated with merozoites of the closely related parasite, Sarcocystis falcatula. These results should be useful in studying sero-epidemiology of S. neurona infections in cats.

Establishment of Besnoitia darlingi from opossums (Didelphis virginiana) in experimental intermediate and definitive hosts, propagation in cell culture, and description of ultrastructural and genetic characteristics

Besnoitia darlingi from naturally infected opossums (Didelphis virginiana) from Mississippi, USA, was propagated experimentally in mice, cats, and cell culture and was characterised according to ultrastructural, genetic, and life-history characteristics. Cats fed tissue cysts from opossums shed oocysts with a prepatent period of nine or 11 days. Oocysts, bradyzoites, or tachyzoites were infective to outbred and interferon-gamma gene knockout mice. Tachyzoites were successfully cultivated and maintained in vitro in bovine monocytes and African green monkey cells and revived after an 18-month storage in liquid nitrogen. Schizonts were seen in the small intestinal lamina propria of cats fed experimentally-infected mouse tissues. These schizonts measured up to 45 x 25 microm and contained many merozoites. A few schizonts were present in mesenteric lymph nodes and livers of cats fed tissue cysts. Ultrastructurally, tachyzoites and bradyzoites of B. darlingi were similar to other species of Besnoitia. A close relationship to B. besnoiti and an even closer relationship to B. jellisoni was indicated for B. darlingi on the basis of the small subunit and ITS-1 portions of nuclear ribosomal DNA.

Redescription of Neospora caninum and its differentiation from related coccidia

Neospora caninum is a protozoan parasite of animals, which before 1984 was misidentified as Toxoplasma gondii. Infection by this parasite is a major cause of abortion in cattle and causes paralysis in dogs. Since the original description of N. caninum in 1988, considerable progress has been made in the understanding of its life cycle, biology, genetics and diagnosis. In this article, the authors redescribe the parasite, distinguish it from related coccidia, and provide accession numbers to its type specimens deposited in museums.

Survival of nonsporulated Toxoplasma gondii oocysts under refrigerator conditions

Toxoplasma gondii oocysts are excreted nonsporulated in the feces of the cats into the environment. These oocysts must undergo sporulation to become infectious. Little is known about the factors that influence sporulation of T. gondii oocysts. The present study examined the survival of nonsporulated oocysts under refrigerated conditions over 11-week observation period. Microscopic examination of oocysts indicated that no visible development occurred under refrigerator conditions. The nonsporulated oocysts retained their ability to sporulate when placed at room temperature. The numbers of visually viable appearing oocysts decreased over time. Some oocysts in all samples were infectious for mice despite being refrigerated for up to an 11 weeks before undergoing sporulation. Results indicate that nonsporulated oocysts can survive in the environment for at least 3 months and retain their ability to become infectious when placed under appropriate conditions.