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Biomedical subjects

A O Heydorn

Publications and source records attributed to A O Heydorn.

At least 19 recordsLinked to original sources
PubMed2005

Oocysts of Neospora caninum, Hammondia heydorni, Toxoplasma gondii and Hammondia hammondi in faeces collected from dogs in Germany.

Faecal samples of 24,089 dogs were examined coproscopically in two veterinary laboratories in Germany between March 2001 and October 2004. In 47 dogs, oocysts of 9-14 microm size were found. Their morphology was similar to those of Hammondia heydorni and Neospora caninum. Samples of 28 of these dogs were further examined by inoculation into gerbils: seven isolates induced a specific antibody response against antigens of N. caninum NC-1 tachyzoites. This response suggests that the isolates contained N. caninum. In addition to H. heydorni (12 times isolated), Toxoplasma gondii occysts (twice) and Hammondia hammondi oocysts (twice) were observed in dog faeces. The latter findings suggest that coprophagia with a subsequent intestinal passage by dogs plays a role in the dissemination of coccidian parasites for which cats are definitive hosts. Five of the seven N. caninum (NC-GER2, NC-GER3, NC-GER4, NC-GER5, NC-GER6) and the two T. gondii isolates (TG-dgGER1, TG-dgGER2) were successfully passaged into cell culture and are now available for detailed characterization. In contrast to oocysts of other parasites, N. caninum oocysts were predominantly found between January and April (Fisher exact; P=0.038). In the sera of dogs shedding N. caninum, no reactions against the immunodominant antigens with apparent molecular weights of 19, 29, 30, 33 and 37 kDa of N. caninum tachyzoites were observed 3-5 weeks after shedding. However, the animals recognized a 152-kDa N. caninum antigen. Compared with those identified as H. heydorni, T. gondii or H. hammondi, N. caninum oocyst isolates were significantly smaller in length with the 75th percentiles <or=10.7 microm when measured in concentrated sucrose solution and smaller length-width ratios with the 75th percentiles <or=1.06. It may thus be possible to develop criteria for a preliminary identification of N. caninum in dog faeces based on the oocyst morphology.

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PubMed2003

Electron microscopic study of in vitro cultures of Hammondia heydorni (Berlin 1996) tachyzoites after passages through dogs, mice, rats, guinea pigs and jirds.

This study describes the fine structure and reproduction of tachyzoites of Hammondia heydorni (isolate Berlin 1996) after in vitro cultivation of stages isolated from serial passages between dogs and various intermediate hosts such as mice, rats, guinea pigs, jirds, knock-out mice, goats and sheep. The tachyzoites are identical with respect to their ultrastructural features to the corresponding stages of the NC-1-strain of Neospora caninum. This fact conforms with other already published data and underlines our opinion that the recently redescribed N. caninum Dubey et al. 2002 is a synonym of the previously described H. heydorni (Tadros and Laarman 1976) Dubey 1977.

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PubMed2001

Hammondia heydorni-like oocysts shed by a naturally infected dog and Neospora caninum NC-1 cannot be distinguished.

This study describes transmission experiments using Hammondia heydorni-like oocysts isolated in 1996 from a naturally infected dog. The isolate was designated as H. heydorni-Berlin-1996. Examination of sera from infected intermediate hosts showed immunoblot reactions that resembled patterns observed after Neospora caninum NC-1 infection. Furthermore, N. caninum DNA could be demonstrated in tissue samples (e.g. heart, brain) of experimentally infected intermediate hosts and in oocyst preparations from H. heydorni-Berlin-1996. The isolated oocysts did not induce any detectable disease in any of the inoculated adult intermediate hosts (goats, sheep, gerbils, guinea pigs, multimammate rats, BALB/c mice, SCID mice), even upon immunosuppression. Furthermore, neither histological lesions nor parasite stages could be identified in the tissues of all fetuses recovered from two multimammate rats that had been infected prior to pregnancy. An experiment with one dog fed a second time on infected intermediate host tissue indicated that immunity may prevent repeated oocyst shedding in N. caninum-infected dogs. In addition, the study clearly demonstrates that N. caninum can be readily transmitted by dogs that have ingested exclusively skeletal muscles of infected intermediate hosts. Therefore, the study has consequences for the recommendations for farmers to prevent postnatal transmission of N. caninum to cattle. It indicates that feeding of any tissues of potential intermediate hosts (including sheep, goats, rodents) to final hosts may induce the shedding of oocysts in these hosts and thus pose a risk for post-natal infection of cattle. With respect to oocyst morphology and the infectivity of muscle tissues for final hosts, no differences were seen in comparison with observations made in the past on Isospora bigemina/I. heydorni/H. heydorni. Therefore, earlier studies made on I. bigemina/I. heydorni/H. heydorni have to be re-evaluated critically to determine whether they may have included N. caninum or other protozoan parasites that use dogs as final hosts and have an oocyst morphology resembling that of I. bigemina/I. heydorni/H. heydorni.

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PubMed2001

Cyclic transmission of Neospora caninum: serological findings in dogs shedding oocysts.

In a previous paper we demonstrated that Hammondia heydorni-like oocysts isolated in 1996 from a naturally infected dog could not be distinguished from the isolate Neospora caninum NC-1. The isolate, designated as H. heydorni-Berlin-1996, was cyclically transmitted using dogs as the final hosts. The present study provides information on the antibody responses of the dogs used for the cyclical transmission of this isolate. The majority of dogs that had shed oocysts showed no sero-conversion with respect to N. caninum tachyzoite surface or immunodominant antigens, either in the indirect fluorescent antibody test or in two Western-blot-based tests. In addition to the examination of responses to immunodominant antigens, we also analysed the antibody reactions of dogs to a high-molecular-weight antigen (152 kDa) in the tachyzoite antigen preparation. The antibodies against this antigen appeared after the dogs had been fed infected intermediate host tissues and shed oocysts. The reaction was observed in dogs between day 35 and day 447 after feeding of intermediate host tissues. Therefore, our study provides initial information on a 152 kDa tachyzoite antigen, which might be a suitable candidate to identify dogs with a history of shedding N. caninum oocysts.

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PubMed2001

Comparative molecular investigation of Nc5-PCR amplicons from Neospora caninum NC-1 and Hammondia heydorni-Berlin-1996.

The clinical relevance of Neospora caninum as a cyst-forming coccidian parasite is increasingly acknowledged within veterinary medicine, although the pathways of transmission are far from being solved. The parasite is well known for causing diaplacental infections in cows associated with abortion and/or severe damage of the fetus. In addition, it may cause neuromuscular disease in dogs, which thus apparently act as intermediate hosts as well as final hosts. In our previous studies, we have demonstrated that molecular diagnosis of N. caninum infections has a high performance when a highly sensitive polymerase chain reaction (PCR) targeted to the Nc5 region of the parasite is used. The present study indicates that the high sensitivity of the PCR is the consequence of a target dose effect which reflects a high redundancy of Nc5-type sequences within the genome of the parasite. The PCR was shown to amplify a set of DNA molecules exhibiting significant sequence differences. A complex composition of Nc5-type sequences was observed in the parasite isolate N. caninum NC-1 but also in another isolate, designated Hammondia heydorni-Berlin-1996. Investigation of the infection pattern of this parasite in its intermediate and final canine hosts showed it to be indistinguishable from N. caninum NC-1.

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PubMed2000

Neospora caninum: is it really different from Hammondia heydorni or is it a strain of Toxoplasma gondii? An opinion.

The published data concerning Toxoplasma gondii, Hammondia hammondi, H. heydorni and Neospora caninum on one side and between T. gondii on the other were neglected by most authors. As conclusion we are convinced that there are only two valid species: Isospora (Toxoplasma) gondii and Hammondia heydorni. The first includes as a strain H. hammondi and the latter N. caninum. In any case there is absolutely no reason (with respect to general Zoological nomenclature) to create new genera!

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PubMed1992

A comparison of sporozoite and cyst merozoite surface proteins of Sarcocystis.

Surface labeling of Sarcocystis muris and S. suicanis sporozoites with N-hydroxysuccinimide biotin led to the detection of major membrane proteins with relative molecular weights of 29 and 30 kDa, respectively. Immunoblots of Sarcocystis sporozoite proteins probed with sera from infected hosts or with polyclonal monospecific antibodies generated against membrane antigens of cyst merozoites (noncorresponding stages) showed cross-reactivity between the two developmental stages (cyst merozoites and sporozoites) as well as between the species S. muris and S. suicanis. Two-dimensional gel electrophoresis resulted in the identification of isoforms of the sporozoite membrane antigens, with isoelectric points ranging from pH 4.7 to pH 6.4 for S. muris and from pH 4.7 to pH 5.2 for S. suicanis. The molecular masses, the charge heterogeneity, and the immunological reactivity of the surface proteins of Sarcocystis sporozoites were similar to those of cyst merozoites of both species.

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PubMed1991

Purification of in vitro excysted Sarcocystis sporozoites by passage through a modified DE 52 anion-exchange column.

A method of purifying Sarcocystis sporozoites following in vitro excystation is described. After passage of sporozoites through a modified DE 52 anion-exchange cellulose column, the mean recovery was 88% for S. capracanis, 71% for S. hircicanis, 77% for S. ovicanis and 74% for S. arieticanis. Most of the sporozoites were motile, and the parasite suspension was free of excystation debris.

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PubMed1990

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.

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PubMed1988

Besnoitia besnoiti: studies on the definitive host and experimental infections in cattle.

Domestic cats, 11 other species of carnivorous mammals, 6 species of snakes, and white-backed vultures were tested for their possible role as definitive hosts of Benoitia besnoiti by feeding with cystic material from chronically infected bovines. None of the species tested is a definitive host; hence, the life cycle of this parasite remains obscure. In attempts to produce clinical cases of besnoitiosis by experimental infection, bovines were inoculated IV, SC, and IP with cystozoites or tachyzoites. Immunosuppression of the animals was essential for the development of severe cases and skin lesions; cystozoites proved to be more pathogenic than tachyzoites.

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PubMed1987

Experimental transmission of Sarcocystis muriviperae n. sp. to laboratory mice by sporocysts from the Palestinian viper (Vipera palaestinae): a light and electron microscope study.

Sporocysts collected from the feces of a Palestinian viper (Vipera palaestinae) were administered orally to species of various rodent genera such as Mus, Microtus, Mastomys, Meriones and Oryctolagus. Infections developed only in laboratory mice (Mus musculus). This investigation established the life cycle of Sarcocystis muriviperae in the laboratory. S. muriviperae is described as a new species, based on light and electron microscopic observations and repeated transmission studies. Naturally and experimentally infected Palestinian vipers both excreted structurally identical sporocysts measuring 9.6 micron (8.8-10.5 microns) by 12.2 microns (11.7-12.9 microns). Sporulation inside the snakes' intestine is completed between 14 and 19 days post-inoculation (p.i.). Rosette-like schizogonic stages were found in the liver cells of laboratory mice 9-10 days after infection with sporulated sporocysts. Sarcocysts measured up to 1,000 microns in length on day 36 p.i. and were mainly filled with metrocytes. The septated sarcocysts found 136 or 165 days p.i. reached a length of 5-8 mm and a width of 150-400 microns. The primary sarcocyst wall formed cauliflower-like branched protrusions about 3.5 microns in length.

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PubMed1987

Fine structure of Sarcocystis arieticanis Heydorn, 1985 in its intermediate and final hosts (sheep and dog).

The developmental stages of S. arieticanis (sheep-dog-cycle) were studied by means of electron microscopy. After oral infection of the sheep with sporocysts two generations of schizonts occur around days 14 and 27 p.i. Both are morphologically more or less similar and are situated immediately inside the cytoplasm of their host cells, which are endothelial cells. They produce somewhat more than 100 merozoites reaching a size of about 6-8 micron X 2.5 micron. The tissue cysts are characterized by hair-like protrusions of the primary cyst wall. These protrusions (reaching a length of 11 micron at the maximum) do not contain fibrils, are folded over and thus running along the surface. These cysts may then appear in light microscopical sections with a smooth cyst wall. The fine structure of the cyst wall was significantly different from the other sheep sarcosporidia. No differences were found in morphology of the cyst merozoites reaching a size of 15 X 2.5 micron. Inside the dog gamogony occurred in the cells of the lamina propria of the lower part of the small intestine. Gamogony was mostly completed after 20 h p.i. and sporogony after 12-14 days p.i. The fine structure of the stages in the final host was similar to that of other Sarcocystis species.

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