The developmental cycle of a species of Sarcocystis occurring in dogs and sheep, with observations on pathogenicity in the intermediate host

Abattoir surveillance of Sarcocystis spp., Cysticercosis ovis and Echinococcus granulosus in Tasmanian slaughter sheep, 2007-2013

OBJECTIVE

To estimate the prevalence of macroscopic Sarcocystis spp., Cysticercus ovis and Echinococcus granulosus recorded at routine postmortem inspection of Tasmanian slaughter sheep during 2007 to 2013.

METHODS

A retrospective analysis of routine postmortem meat inspection data maintained on 352,325 Tasmanian adult slaughter sheep inspected across nine abattoirs in Tasmania, Victoria and South Australia as part of the National Sheep Health Monitoring Project (NSHMP).

RESULTS

During the period 1 September 2007 to 30 June 2013, the estimated prevalence of macroscopic Sarcocystis spp. was 14.3%, C. ovis was 3.2% and E. granulosus was 0.01%. Mean Sarcocystis spp. line prevalence ranged from 0% to 33.5%. Significant between-abattoir differences in the level of sarcosporidiosis (P < 0.001) and C. ovis were found (P < 0.001). Overall, very low levels of hydatidosis were recorded throughout the surveillance period. Predicted within-line prevalence of macroscopic sarcocysts in animals coming from a known/recorded local government area (LGA) (P < 0.001) was lower than that of lines where the LGA was unknown or not recorded. A higher prevalence of sarcocystosis was recorded in lines of sheep aged ≥ 2 years compared with those < 2 years (P < 0.001).

CONCLUSION

Reasons for the significant between-abattoir differences in recorded levels of ovine sarcosporidiosis and cysticercosis remain unknown, but may represent sampling bias, with subsets of slaughter sheep going to abattoirs with different tiers or access to markets. Further investigation into apparent differences, including epidemiological studies of properties with high lesion prevalence, comparing meat inspector diagnostic sensitivity, assessing the effect of line speed and tiers and market access in different abattoirs, may be useful.

Sarcocystid organisms found in bile from a dog with acute hepatitis: a case report and review of intestinal and hepatobiliary Sarcocystidae infections in dogs and cats

Sarcocystidae is a family of coccidian protozoa from the phylum Apicomplexa that includes Toxoplasma, Neospora, Sarcocystis, Hammondia, and Besnoitia spp. All species undergo a 2-host sexual and asexual cycle. In the definitive host, replication is enteroepithelial, and infection is typically asymptomatic or less commonly causes mild diarrhea. Clinical disease is most frequently observed in the intermediate host, often as an aberrant infection, and is mostly associated with neurologic, muscular, or hepatic inflammation. Here, we review the literature regarding intestinal Sarcocystidae infections in dogs and cats, with emphasis on the life cycle stages and the available diagnostic assays and their limitations. We also report the diagnostic findings for an 11-year-old dog with acute neutrophilic hepatitis, biliary protozoa, and negative biliary culture. Although Toxoplasma and Neospora IgG titers were both high, PCR for these 2 organisms was negative for bile. The organisms were identified by 18S rDNA PCR as most consistent with Hammondia, either H heydorni or H triffittae. This is the first report of presumed Hammondia organisms being found in canine bile.

First molecular characterization of Sarcocystis tenella in Tatra chamois (Rupicapra rupicapra tatrica) in Poland

In this study, sarcocysts from three Polish Tatra chamois were isolated and identified using morphological and molecular methods for the first time. Six cysts were found in the latissimus dorsi muscle and another two in the diaphragm. No sarcocysts were detected in the myocardium, tongue, and esophagus. The isolated cysts were long with rounded ends, 0.35-0.61 mm in length, and 0.02-0.06 mm in width. All the sarcocysts were identified as Sarcocystis tenella on the basis of light microscopy and sequencing of cytochrome C oxidase subunit I (cox1) and small-subunit rRNA (ssu rRNA) genes. Comparative analysis showed a 99.23% identity of the cox1 gene sequences from Tatra chamois and sheep sarcocysts, and an even higher degree of sequence identity (99.88%) was documented in the case of the ssu rRNA gene. When compared at a haplotype level, all the sheep sequences of cox1 differed from those isolated from Tatra chamois. In contrast, one out of the two ssu rRNA haplotypes from the sheep isolates was identical with the haplotype from Tatra chamois. In conclusion, we showed that cox1 and ssu rRNA genes can be used as genetic markers for identification of the S. tenella, with cox1 gene providing better resolution during phylogenetic analyses. However, both genetic population analysis and phylogenetic inference with cox1 and ssu rRNA genes demonstrated that they do not constitute good markers for spatial differentiation of S. tenella.

Oocysts and high seroprevalence of Neospora caninum in dogs living in remote Aboriginal communities and wild dogs in Australia

Canines are definitive hosts of Neospora caninum (Apicomplexa). For horizontal transmission from canines to occur, viable oocysts of N. caninum must occur in the environment of susceptible intermediate hosts. Canids in Australia include wild dogs and Aboriginal community dogs. Wild dogs are those dogs that are not dependent on humans for survival and consist of the dingo, feral domestic dog and their hybrid genotypes. Aboriginal community dogs are dependent on humans, domesticated and owned by a family, but are free-roaming and have free access throughout the community. In this study the extent of N. caninum infection was determined in a total of 374 dogs (75 wild dogs and 299 Aboriginal community dogs) using a combination of microscopic, molecular and serological techniques. Oocysts of N. caninum were observed in the faeces of two juvenile Aboriginal community dogs (2/132; 1.5%). To estimate N. caninum prevalence, a new optimised cut-off of 18.5% inhibition for a commercial competitive ELISA was calculated using a two-graph receiver-operating characteristic (TG-ROC) analysis and IFAT as the gold standard resulting in equal sensitivity and specificity of 67.8%. Of the 263 dog sera tested the true prevalence of N. caninum antibodies was 27.0% (95% confidence limit: 10.3-44.1%). The association between the competitive ELISA results in dogs less than 12 month old and older dogs was significant (P=0.042). To our knowledge this is the first large scale parasitological survey of the Aboriginal community dogs and wild dogs from Australia. The high prevalence of N. caninum infection in Aboriginal community dogs illustrates that horizontal transmission of N. caninum is occurring in Australia. These results demonstrated that N. caninum in dogs is widespread, including the semi-arid to arid regions of north-western New South Wales and the Northern Territory. The populations of free-ranging dogs are likely to be important contributors to the sylvatic life cycle of N. caninum.

Development and validation of species-specific nested PCRs for diagnosis of acute sarcocystiosis in sheep

Sheep may be infected by four species of Sarcocystis. Two of these species, Sarcocystis tenella and Sarcocystis arieticanis, are pathogenic. They may cause abortion or acute disease during the early phase of infection, and chronic disease during the late phase of infection. Thus far, diagnosis of sarcocystiosis in sheep has been limited, because traditional diagnostic tests based on the detection of Sarcocystis-specific antibodies are only genus-specific and, thus, cannot differentiate between pathogenic and non-pathogenic species. In addition, most of these tests show a reasonable sensitivity only for the late phase of infection. Therefore, diagnosis of acute sarcocystiosis has been based mainly on post-mortem examination, i.e. after the animal had succumbed to the disease. Here we established species-specific nested PCR assays based on unique small subunit ribosomal RNA gene sequences of S. tenella and S. arieticanis. These PCR assays specifically detect DNA of the homologous species in blood samples of sheep. No cross-reactions were observed with the heterologous pathogenic species, the non-pathogenic species Sarcocystis gigantea, or the closely related coccidia Toxoplasma gondii and Neospora caninum. In sheep experimentally infected with S. tenella or S. arieticanis, positive PCR results were correlated with the early phases of multiplication (endopolygeny) of the parasites. By contrast, Sarcocystis-specific antibodies were detected by an enzyme-linked immunosorbent assay only during the terminal phase of endopolygeny or thereafter. Thus, the nested PCR assays developed here enable, for the first time, the diagnosis and differentiation of infections with S. tenella and S. arieticanis in living sheep during the acute phase of the disease and facilitate comprehensive studies on the epidemiology and importance of infections with pathogenic Sarcocystis species in sheep.

Perspectives on the biodiversity of parasitic protozoa in Australia

Biodiversity is a term applied to described the number, variety and variability of organisms. Its colloquial application is usually as a measure of species diversity of species richness. Thus, the concepts of "species" and "species boundaries" are integral to any discussion on biodiversity, and with them, the basal question of what constitutes meaningful variation. Protozoan taxonomy is an evolving mix of morphological and molecular characters, and is based largely on decisions made intuitively and arbitrarily using multiple characters. Where to draw species boundaries has become more difficult in the face of a bewildering level of variation uncovered in recent years, due largely to an increase in the resolution of our taxonomic techniques (e.g., ultrastructural and genetic studies). A major challenge for contemporary protozoan taxonomists is to update the existing systematic framework to incorporate our current level of knowledge and to decide on the relative importance of parasite morphology, genetics and biology to the concept of the protozoan "species". This task is compounded by the relative paucity of information on our endemic protozoan parasites. In Australia, even in vertebrate hosts, little is known of the biodiversity of parasitic protozoa. Not surprisingly, what knowledge we do have is linked to clinical disease, e.g., detailed knowledge of some species of coccidia and of some enteric ciliates, flagellates and amoebae of mammals. We have some knowledge of a few species of haemosporidia of reptiles and birds but, even here, molecular studies and experimental work are required to identify species boundaries. In view of these limitations, the best estimate of the biodiversity of Australia's parasitic protozoa in at least the vertebrate fauna of Australia, is that less than one third of the total species have been discovered to date.

Protozoal causes of reproductive failure in domestic ruminants

Protozoan parasites are a significant cause of abortion and infertility in domestic ruminants. Toxoplasma gondii, a widespread cause of abortion in sheep and goats, and Sarcocystis spp., which cause a common, frequently asymptomatic infection of domestic ruminants, both have a two-host life cycle. Carnivorous definitive hosts spread the infection through their feces and domestic ruminants are intermediate hosts. A similar, recently recognized protozoa, Neospora sp., has emerged as an important cause of reproductive disease, especially as an abortifacient in dairy cattle. Neospora is presumed to also have a two-host life cycle, although the definitive host(s) has not been identified. The venereally transmitted Tritrichomonas foetus is an important cause of pregnancy loss in naturally bred cattle throughout the world. In the absence of effective methods for vaccination or treatment, control of these parasites is based on management procedures to reduce infection and transmission.

Ovine myeloencephalitis-leukomyelomalacia associated with a Sarcocystis-like protozoan

Bilateral pelvic limb paresis developed in 7 of 15 10-month-old Blueface Leicester ram lambs on a mixed enterprise farm in the North of England. Clinical signs were principally mild to severe paresis of the pelvic limbs. Two mildly affected lambs recovered. Multifocal spinal cord white matter edema and necrosis, glial nodules, and mild to moderate nonsuppurative encephalomyelitis were the principal findings in 3 severely paretic lambs examined histologically. Protozoan bodies (12.7-23.0 microns) that stained immunocytochemically for Sarcocystis epitopes were in spinal cord glial cells of 2 of 3 lambs. Protozoa did not react immunocytochemically with anti-Toxoplasma gondii or Neospora canium antisera. Serology indicated there was recent exposure to Sarcocystis spp. in some surviving lambs. These cases resembled those in previous reports of paresis due to an unidentified Sarcocystis-like protozoan in sheep (ovine protozoan myeloencephalitis) in the British Isles, the USA, France, Australia, and New Zealand.

Characterization of monoclonal antibodies against ovine Sarcocystis spp. antigens by immunoblotting and immuno-electron microscopy

Six monoclonal antibodies were raised in mice against purified cytozoite extracts of Sarcocystis gigantea and S. tenella from sheep. Each monoclonal antibody was evaluated for specificity by enzyme immunoassay, immunoblotting and immuno-electron microscopy using homologous and heterologous antigenic preparations. All six monoclonal antibodies exhibited good species-specificity when reacted against crude soluble cystozoite antigens in enzyme immunoassays. However, only two monoclonal antibodies (IgM and IgG2a) exhibited reactivity in Western blots against specific protein bands. Both reacted against S. gigantea antigens of 100,000, 43,000 and 39,000 molecular weight. Neither monoclonal antibody reacted against the heterologous species S. tenella. Ultrastructural studies performed with colloidal-gold conjugated antisera revealed that both monoclonal antibodies reacted against antigens located around micronemes and amylopectin granules in S. gigantea cystozoites. Another monoclonal antibody (IgGI) reacted only against microneme determinants in S. tenella cystozoites. In contrast, polyclonal sheep and rabbit immune sera cross-reacted against a wide range of cystozoite antigens.

DNA measurements and ploidy determination of different stages in the life cycle of Sarcocystis muris

The DNA contents of different stages within the life cycle of Sarcocystis muris were measured cytophotometrically using DNA-specific Feulgen staining. Stages of gamogony were obtained by the transfer of isolated cyst merozoites into cat kidney-cell cultures. For calculation of absolute DNA contents, the amounts of DNA in the parasites were compared with those in chicken erythrocytes, which are known. The measurements revealed that all investigated stages of S. muris contained haploid DNA except the early zygotes, which were diploid. The further development of the zygotes started with a nuclear division, resulting in two daughter nuclei that again revealed haploid DNA values. The results confirm the existence of zygotic meiosis; thus, a haplo-homophasic life cycle is proposed for the Sarcosporidia.

Antibody development and cellular immune responses in sheep immunized and challenged with Sarcocystis tenella sporocysts

Four specific-pathogen-free (SPF) sheep were experimentally infected with 10(3) or 10(4) Sarcocystis tenella (syn. S. ovicanis) sporocysts and another two sheep served as uninfected controls. All sheep were challenged 49 days later by infection with 2.5 X 10(5) sporocysts and their humoral and cellular responses to infection and challenge were assessed weekly by enzyme immunoassays and lymphocyte transformation assays. The control sheep died from acute sarcocystosis 29-30 days after challenge, whereas the immunized sheep survived and were protected against acute disease. Specific IgM and IgG antibodies were detected in the immunized sheep from 28 days after infection onwards. Lymphocytes collected before and after challenge did not exhibit any significant differences in their responses to stimulation with S. tenella cystozoite or sporozoite antigens. Furthermore, lymphocytes collected before challenge did not differ from the controls in their responses to stimulation with the mitogens lipopolysaccharide or phytohaemagglutinin. However, lymphocytes collected after challenge did exhibit increased blastogenic responses to stimulation with both mitogens from 21-28 days after challenge onwards. The infected sheep were necropsied 46 days after challenge, and histological and ultrastructural studies revealed numerous infiltrates of lymphocytes, histiocytes and plasma cells in the skeletal muscles, sometimes in association with degenerating parasitic cysts and macrophage myophagia. Parasites were not completely eliminated nor prevented from further establishment, therefore the protective immunity was not sterile but rather a state of premunition.

Lesions in sheep inoculated with Sarcocystis tenella sporocysts from canine feces

Sarcocystosis was studied in 37 sheep after oral inoculation with 10(4)-5 x 10(7) sporocysts of Sarcocystis tenella from canine feces. Two sheep inoculated with 2.5 x 10(7) and 5 x 10(7) sporocysts became moribund 16 and 19 days post-inoculation (DPI), respectively, due to occlusion of arteries of gut and mesentery by first generation meronts. Sheep inoculated with 10(7) sporocysts remained clinically normal until 21 DPI and those inoculated with 10(5)-10(6) became ill 24-28 DPI due to anemia coincident with maturation of second generation meronts. Inflammation, hepatitis and myocarditis were the main lesions of acute and subacute ovine sarcocystosis. Inflammation began to subside by the time (75 DPI) sarcocysts matured. Sarcocystis-induced encephalitis was distinguished from naturally occurring myelomalacia in sheep caused by an unidentified sporozoan.

Hosts of two canid genera, the red fox and the dog, as alternate vectors in the transmission of Sarcocystis tenella from sheep

Microscopic sarcocysts recovered from naturally infected sheep were infective to both the domestic dog (Canis familiaris) and the red fox (Vulpes vulpes). The parasite was passaged through experimental specific-parasite-free (SPF) sheep three times: infection was transmitted twice with sporocysts from foxes and subsequently with sporocysts from dogs. The sarcocysts from sheep muscle were infective to both dogs and foxes on each occasion. A cat was not infected. The prepatent period in individual canids ranged from 7 to 15 days. Sporocyst excretion was still detectable 60 days post infection. This study establishes that canids of two genera may act as vectors for a single isolate of the same Sarcocystis species from sheep.

Clinical, haematological and plasma biochemical changes in specified-pathogen-free (sporozoa) lambs experimentally infected with low numbers of Sarcocystis tenella sporocysts

Two groups of lambs raised free of sporozoan infection were inoculated with Sarcocystis tenella sporocysts and compared with controls. Lambs from Group 1 were inoculated with 5000 sporocysts and those in Group 2 were given 20,000. Transient increases in rectal temperatures occurred between 23 and 39 days post-inoculation (dpi), although the lambs appeared normal and retained their appetites. Packed cell volumes (PCV) of lambs given 20,000 sporocysts decreased dramatically from 28 to 38 dpi after which they slowly returned to near pre-inoculation levels by 99 dpi. The anaemia was normocytic/normochromic. White cell counts (WCC) rose in infected lambs from 49 dpi, reflecting principally an increase in lymphocyte numbers. Plasma albumin of Group 2 decreased at 28 dpi and remained depressed until the experiment was terminated at 99 dpi. Plasma globulin of infected groups increased from 31 (Group 2) and 35 dpi (Group 1). Plasma alkaline phosphatase (ALP) of Group 2 decreased from 28 dpi and remained depressed to 99 dpi. Lactate dehydrogenase (LDH) of Group 2 was elevated at 24 and 28 dpi and from 42 to 78 dpi, while aspartate aminotransferase (AST) of the same group was elevated from 45 to 66 dpi. Creatine kinase (CK) of Group 2 was elevated from 52 to 71 dpi.

Sarcocystosis

Sarcocystis infections of animals are commonplace and of worldwide distribution. Some species can be severely pathogenic to farm animals, causing anorexia, weight-loss, abortion and even death. But perhaps because sarcocysts are so common they have frequently been regarded as innocuous. Even in the USA and UK, many cases of abortion in farm animals go undiagnosed, and it is only now that sarcocystosis is being implicated as potentially of economic importance to the farm industry. In many cases however, the major effect is likely to be subclinical, seen in farm animals only as a reduction in liveweight gain. As this review shows, the history of research on Sarcocystis has been marked by confusion and neglect, although enormous progress has been made in the last decade. But until their economic importance is fully recognized, these widespread infections seem likely to continue unchallenged.

Demonstration of schizogonous stages of Sarcocystis gigantea in experimentally infected sheep

Sarcocystis-free lambs were orally dosed with 1 X 10(6) sporocysts of Sarcocystis gigantea. Schizonts were found in endothelial cells of capillaries and arterioles of the brain, lung and kidney of lambs 7 and 14 days post-inoculation (d.p.i.). Between 21 and 35 d.p.i. there was extensive multi-focal encephalitis; however no organisms were detected in association with these lesions.

Morphology of Sarcocystis gigantea in experimentally-infected sheep

The development of the parasite and lesions was studied in 32 sheep killed 10 days to 47 months after inoculation with Sarcocystis gigantea sporocysts from cats. At 21-42 days post-inoculation (d.p.i.), there was a mild encephalitis, but organisms were not seen in the brain. Immature sarcocysts were detected from 40-84 d.p.i. The cyst wall was not measurable by light microscopy at 40 d.p.i., but was 1.5-2 microns thick at 84 d.p.i. At 119 d.p.i. both immature cysts containing only metrocytes, and mature cysts containing both metrocytes and merozoites, were present. These mature cysts did not have a secondary cyst wall. A mature cyst, 350 microns in length, was found in a sheep killed at 8 1/2 months p.i. At 10 m.p.i. cysts were up to 0.5 mm long and a secondary cyst wall was present. At 47 m.p.i. cysts were 2-5 X 4.5-7.5 mm, and were found only in the muscles of tongue, oesophagus, pharynx and flank.

Development and growth of Sarcocystis gigantea in experimentally-infected sheep

Immature, microscopic Sarcocystis gigantea sarcocysts were detected in experimental sheep from 1.3 to 4 months after dosing with sporocysts from cats. Mature, microscopic sarcocysts were also present at 4 months post-inoculation (p.i.). S. gigantea sarcocysts were 0.35 mm long at 8.5 months p.i. and gradually increased in size to 7.5 mm by 45 months p.i. Transmission back to cats was demonstrated at 14 months p.i.

The effect of Sarcocystis tenella on wool growth in sheep

A dose of 1 X 10(4) Sarcocystis tenella sporocysts produced significant depression of wool growth in lambs dosed at 1 month of age. No significant effect on wool growth was produced when lambs were dosed at 5 months of age.

Haematological and biochemical changes in buffalo calves inoculated with Sarcocystis fusiformis from cats

Two groups of buffalo calves were infected with Sarcocystis fusiformis sporocysts. Animals of the first group received each 5 X 10(5) sporocysts, those of the second group 5 million sporocysts. All calves were clinically normal during 6 weeks after infection. Minor changes were observed in the blood cytology, serum alkaline phosphatase, glutamic oxalacetic transaminase, glutamic pyruvic transaminase, total proteins, urea and glucose of infected buffalo calves.

Immunity to sarcocystosis: modification of intestinal coccidiosis, and disappearance of sarcocysts in dairy goats

Fifty, 2-3 month old dairy goats were each vaccinated orally with 10000 sporocysts of Sarcocystis capracanis and 25 age-matched goats served as uninoculated controls. Groups of vaccinated and control goats were challenged with lethal doses of S. capracanis at 95, 113, 205, and 274 days post-vaccination. Vaccinated goats developed subclinical sarcocystosis. Twenty-three vaccinated goats and 1 control goat died of intestinal coccidiosis and bacterial pneumonia, 15-118 days after vaccination. Myositis and degenerating sarcocysts were seen in muscles of goats necropsied at 90-186 days postvaccination. Very few, or no sarcocysts were seen in goats necropsied at 272 and 332 days post-vaccination. Vaccinated goats survived a lethal challenge inoculation indicating persistent protective immunity.

Electron microscope study of merogony preceding cyst formation of Sarcocystis sp. in roe deer (Capreolus capreolus)

Precystic merogony of Sarcocystis sp. was studied in roe deer fawns 33, 45, and 49 days postinoculation (pi) with 2 X 10(4)-10(5) sporocysts recovered from dogs. Single merozoites, but no meronts, were found 33 days pi in liver, spleen, and lymph nodes. Transforming merozoites and meronts were found in myofibroblasts, satellite cells, and endothelial cells of muscle tissue on 45 and 49 days pi; they were surrounded by two membranes. Typical coccidian merozoites differentiated simultaneously around an enlarged, lobed nucleus.

The endogenous stages of Sarcocystis cameli (Mason, 1910)

The endogenous stages of Sarcocystis cameli (Mason, 1910) in the small intestine of dogs are described. These stages are mainly in the posterior third of the small intestine. They were observed only in the lamina propria of the distal third of the villi. There was no schizogonic process. Micro and macrogamonts were differentiated 18 h p.i. The first zygote was observed 24 h later. Unsporulated oocysts were found 30, 36, 42, 48 h and 4 days p.i. The oocysts started sporulation on the 5th day p.i. Completely sporulated oocysts were formed 8 days p.i.

Premature parturition in ewes inoculated with Sarcocystis ovicanis

A dose of 6 X 10(4) Sarcocystis ovicanis sporocysts produced premature parturition in ewes and eventually proved fatal. The main pathological findings were myositis, myocarditis and encephalitis. Dose rates over the range of 2.5 X 10(3) to 6 X 10(4) depressed the haematocrit levels of pregnant ewes during the period 5-9 weeks after inoculation. Previous infection with S. gigantia did not protect from subsequent challenge with S. ovicanis.

Sarcocystinae: nomina dubia and available names

Examination of the original descriptions of the species of Sarcocystis in cattle, sheep, and swine, and of isosporid oocysts shed sporulated by dogs, cats, man, and other carnivores, has shown that it is not possible in most instances to identify unambiguously recently recognized taxa. The original descriptions are insufficient, and because no type specimens exist, could apply to two or more of the presently recognized taxa. We consider the following nomina dubia: Sarcocystis hirsuta S. miescheriana S. tenella S. cruzi S. bertrami Isospora bigemina (S. bigemina) I. hominis (S. hominis) I. buteonis (Frenkelia buteonis) Because the former type species, Sarcocystis miescheriana, is an indeterminate nomen dubium, we are proposing S. muris as the new type species. Historically, it was the first species described clearly and unambiguously even in the light of present knowledge, and the stages of its life cycle are probably completely known; it was the second species to be named. Old and recent descriptions are reviewed, and definitions are proposed for the following taxa: S. bovifelis S. bovicanis S. bovihominis S. ovifelis S. ovicanis S. muris (type species) S. suihominis S. suicanis S. equicanis Frenkelia microti F. glareoli for which neotypes will be prepared and deposited with designated institutions and curators. A new subfamily, Cystoisosporinae, is created.

Electron microscopical study on gamogony of Sarcocystis suihominis in human tissue cultures

Sexual stages and oocysts of Sarcocystis suihominis were developed in human tissue cultures and studied with the electron microscope. This development was extremely rapid, being completed about 18--22 h post infection and there were no preceding schizogonic processes, thus confirming the earlier observations that schizogony is obligatorily restricted to the intermediate host in the sarcosporidian life cycle. Micro- and macrogamonts could be distinguished about 12 h post infection and were situated in a parasitophorous vacuole bounded by two membranes. These gamonts reached diameters of up to 10 micrometer. The large nucleus of every microgamont gave rise simultaneously to about 20--30 microgametes. Only dense projections of the nucleus were used as nuclei of microgametes. The microgametes were slender, about 4--5 micrometer long, and several were found to have three flagella, one of which was attached to the body for some distance. Besides these flagella additional microtubules were found and in several cases the attached flagellum was not complete and contained various numbers of single or paired microtubules. The macrogametes were bounded by two membranes and contained two types of inclusions similar to the wall-forming bodies known from the genus Eimeria. The oocysts were bounded by a wall consisting of a dense outer layer and four membranes, under which two other membranes covered the cytoplasm. Beginning from the 22nd h post infection a development similar to sporulation was noted inside these oocysts. This sporulation, i.e., the formation of two sporocysts inside an oocyst, was, however, not completed, probably due to the rapid degeneration of the parasitized host cell. The oocyst itself even appeared intact five days later.

A sarcocystis-like protozoon in a sheep with lymphadenopathy and myocarditis

A generalized enlargement of the lymph nodes was found in an emaciated adult ewe. Additional autopsy findings included tiny grey-white necrotic foci in the heart muscle, aspiration pneumonia and diffuse pleuritis. Light microscopy showed a generalized lymphadenopathy with perilymphadenitis, depletion of lymphocytes and histiocytosis of the lymph node. In histiocytes and vascular endothelial cells of lymph nodes, septal capillary endothelium of lungs and capillary endothelium of myocardium, early stages of a protozoan parasite were found. In the myocardium, there were many foci of necrosis, some of which contained young cysts in the periphery. These cysts were morphogically similar tho those of Sarcocystis. Electron microscopy of the early protozoan stages yielded evidence of schizogony and formation of merozoites.

[Contributions to the life-cycle of Frenkelia. III. The sexual development of F. clethrionomyobuteonis in the buzzard (author's transl)]

8 buzzards (Buteo buteo) were infected orally with cysts of Frenkelia clethrionomyobuteonis of the bank vole (Clethrionomys glareolus). Their intestines were searched for developmental stages of Frenkelia 21 and 24 h and 2, 3, 4, and 5 days post infection. After 21 and 24 h male and female gamonts could be detected within epithelial cells of the villi of the first half of the small intestine. The microgamonts contained 10-14 microgametes. The macrogamonts which measured on an average 11,1 X 9,8 mum in Giemsa stained smears developed into very thin-walled oocysts measuring in fresh preparations on an average 15,8 X 11,7 mum on day 3 after infection. The oocysts were located between the lamina propria and the epithelial lining of the distal third of the villi. They began to sporulate on day 5 and the first sporocysts were excreted 7 and 8 days post infection. Schizonts and schizont-like stages could not be observed in the developmental cycle in Buteo buteo.

Sarcocystosis: a clinical outbreak in dairy calves

Death and illness in a pen of eight yearling dairy heifers was caused by the protozoan parasite Sarcocystis. All animals had weight loss, weakness, marginal anemia, and elevated serum enzymes. Affected animals had high hemagglutinating antibody titers to Sarcocystis antigen. Affected tissues of the two animals that died demonstrated schizonits and young cysts during pathologic examination. The resident farm dog was shedding Sarcocystis sporocysts and was incriminated as the source of infection.

Suspected Sarcocystis infections of the bovine placenta and foetus

Protozoan parasites resembling Sarcocystis schizonts were found in the brains of 2 bovine foetuses and the placentas of another 4. As typical of Sarcocystis, the organisms were located mainly within vascular endothelial cells, and frequently the zoites within the schizonts were arranged in a rosette or palisade fashion. Pathological changes noted were placentitis, myocarditis, pulmonary vasculitis and encephalitis. Attempts to demonstrate Toxoplasma by animal inoculation and serology were unsuccessful.

[Light and electron microscope studies on cysts of Sarcocystis ovicanis Heydorn et al. (1975) within muscle fibres of sheep (author's transl)]

Four conventionally reared lambs, isolated at the age of 5 and 8 weeks, were orally infected with oocysts and sporocysts from dogs, which had been fed raw muscles from sheep containing small cysts of S. tenella. Three lambs, each infected with 100,000 sporocysts, were killed at days 41, 63 and 81 p.i. The other lamb was used for a non-infected control. The development of Sarcocystis-cysts in muscle cells of the infected lambs was studied by light and electron microscopy. The cyst was always situated within a muscle fiber which was never surrounded by fibrillar layers (=no secondary cyst wall). The cyst was limited by a unit membrane, which was thickened at numerous places of the interior by osmiophilic material. This complex is called primary cyst wall (= Primärhülle), reaching a thickness of up to 25 nm. In old cysts this primary wall was regulary folded, forming palisade-like protrusions of about 3.5 mu in length. In light microscopy the combined protrusions had the appearance of a radially striated "thick wall", because of their close proximity to each other. During formation of the palisade-like protrusions the thin areas of the primary wall were restricted to the base of the protrusions and to the small space between the protrusions. Here, the single unit membrane formed vesicle-like invaginations of about 40 nm in diameter into the interior of the cyst. Vesicles seen in the cysts were thought to derive from these invaginations. Within the palisade-like protrusions never fibrillar or tubular elements appeared. In comparing the fine structure of the cyst wall of the small cysts, studied here, with the macroscopically visible cysts we found significant differences. These differences in the morphology confirm the results of transmission experiments, by which it was shown that S. tenella as described in literature is part of at least two coccidian life cycles. So the term S. tenella was replaced by two new species: S. ovicanis (final host: dog) and S. ovifelis (final host: cat) Heydorn et al. (1975).