Alfred Otto Heydorn

The sarcosporidia (Protozoa, Sporozoa): life cycle and fine structure.

Publisher Summary Sarcosporidia have adapted their life cycle to the “predator–prey” relationship existing between their hosts. Some carnivores may be final hosts of several sarcocystis species and omnivores may be involved as intermediate as well as final hosts in the life cycles of different sarcosporidian species. Sporocysts or sporulated oocysts shed in the faeces of the final host must always be ingested by the intermediate host. The oocysts and sporocysts of the sarcosporidian life cycles are morphologically identical with those of the genus isospora, and thus, sarcocystis has been classified as isospora species. However, there are four differences: (1) the Sarcosporidia have an obligatory two-host cycle, (2) schizogony has two phases: an extraintestinal multiplication followed by cyst formation mostly within the muscles of the intermediate host, (3) in Sarcosporidia, no schizogonic multiplication occurs in the gut wall of the final host or in cell culture, and (4) in Sarcosporidia, oocysts are excreted fully sporulated; single sporocysts are often observed in the faeces of the final host because of the rupture of the extremely fine oocyst wall.

In contrast to dogs, red foxes (Vulpes vulpes) did not shed Neospora caninum upon feeding of intermediate host tissues

The alteration of one word during editing the above mentioned article led to a wrong statement at the end of the discussion (last paragraph, first sentence). The mistake remained un-observed during proof-reading. The sentence ‘‘By bioassay, we can conclude that there were more than 3,700 and 200 oocysts of our N. caninum-isolate among the Hammondia sp.-like oocysts collected during the first and the second foxfeeding experiments, respectively.’’ has to be corrected into ‘‘By bioassay, we can exclude that there were more than 3,700 and 200 oocysts of our N. caninum-isolate among the Hammondia sp.-like oocysts collected during the first and the second fox-feeding experiments, respectively.’’ Parasitol Res (2002) 88: 592 DOI 10.1007/s00436-002-0648-x

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 whitebacked vultures were tested for their possible role as definitive hosts ofBenoitia 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.

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

Abstract. 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.

Sarcocystinae:Nomina Dubia and available names

SummaryExamination of the original descriptions of the species ofSarcocystis 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 followingnomina dubia: Because the former type species,Sarcocystis miescheriana, is an indeterminatenomen dubium, we are proposingS. 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 reviwed, and definitions are proposed for the following taxa: for which neotypes1 will be prepared and deposited with designated institutions and curators. A new subfamily, Cystoisosporinae, is created.

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

Abstract 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!

Electron microscopical study on gamogony ofSarcocystis suihominis in human tissue cultures

SummarySexual stages and oocysts ofSarcocystis 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 μm. 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 μm 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 genusEimeria. 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.ZusammenfassungMenschliche Zellkulturen (Hautfibroblasten, Darmzellen) wurden mit Merozoiten aus Cysten vonSarcocystis suihominis vom Schwein inkubiert und im Abstand von zwei Stunden bis zum 5. Tage p.i. untersucht. Es zeigte sich, daß sich in diesen Zellen die Gamogonie vollzog und anschließend auch Oocysten gebildet wurden. Diese Entwicklung verlief sehr schnell und benötigte etwa 18–22 h. Etwa 12 h nach der Inkubation waren Mikro-und Makrogamonten deutlich zu unterscheiden, die stets in einer parasitophoren Vakuole lagen. Im Zeitraum von 14–18 h nach der Inkubation fand die Bildung der Mikrogameten statt. Dabei teilte sich der große Kern des Mikrogamonten gleichzeitig in etwa 20–30 sehr elektronendichte Bereiche auf, die unmittelbar als Kern in einen Mikrogameten übernommen wurden. Die an der Oberfläche des Mikrogamonten entstehenden Mikrogameten waren länglich, erreichten 4–5 μm Länge und einige wiesen eindeutig drei Geißeln auf, von denen eine allerdings teilweise als Schleppgeißel ausgebildet war und oft nicht komplett erschien. Neben diesen Geißeln konnten auch noch einzelne zusätzliche Mikrotubuli in Erscheinung treten. Die Makrogameten maßen etwa 10 μm im Durchmesser, waren von zwei Membranen begrenzt und enthielten Einschlüsse, die den Hüllbildungskörpern 1 und 2 der Eimerien sehr ähnelten. Etwa ab 18 h p.i. waren Oocysten in den parasitophoren Vakuolen der Wirtszellen anzutreffen. Die Oocystenwand bestand aus einer elektronendichten Schicht und vier unterlagerten Membranen, während das Cytoplasma der Zygote unmittelbar von zwei weiteren Membranen begrenzt wurde. Die Sporulation, d.h. die Bildung der Sporocysten, setzte schon nach etwa 22 h p.i. ein.Die Ergebnisse der vorliegenden Arbeit beweisen, daß die Gamogonie auch in Zellkulturen vom spezifischen Endwirt abläuft. Auf diese Weise kann völlig sauber mit einer einzigen Art gearbeitet werden, ohne Kontaminationen des Endwirtdarms in Rechnung stellen zu müssen. Die Ergebnisse zeigten weiterhin, daß in den Zellen des Endwirts tatsächlich direkt die Gamogonie von den Parasiten vollzogen wird und nicht erst ungeschlechtliche Vermehrungen. Die Sarkosporidien haben somit eindeutig den von uns aufgezeigtenobligatorischen Generationswechsel.

Neospora caninum is an invalid species name: an evaluation of facts and statements.

Abstract. An evaluation of both the formal requirements of the International Rules of Zoological Nomenclature and the scientific reasons for the description of new genera and species shows that the name Neospora caninum is a nomen nudum. The only characteristic criteria for discriminating between the previously described species Hammondia heydorni and the proposed new species N. caninum (i.e. the lack of a parasitophorous vacuole) has been shown to be wrong in many publications. Furthermore, absolutely no criteria were presented as to why a new genus (i.e. Neospora) should be established besides the already existing genera Hammondia, Toxoplasma and Isospora. In addition, recent transmission experiments show that an oocyst isolate (from the faeces of dogs) is morphologically indistinguishable from H. heydorni [synonymous with Isospora bigemina – small form, Isospora heydorni (Tadros and Laarman 1976) and H. heydorni (Tadros and Laarman 1976) Dubey 1977] and is almost identical with respect to molecular biological features with the NC-1 strain of N. caninum.

A novel Sarcocystis-associated encephalitis and myositis in racing pigeons

Sarcosporidian cysts in the skeletal muscle of domestic pigeons (Columba livia f. domestica) have previously been attributed to infection with Sarcocystis falcatula, which is shed in the faeces of the opossum (Didelphis virginiana). Here, we describe fatal spontaneous encephalitis and myositis associated with Sarcocystis infections in three flocks of racing pigeons with 47 of 244 animals affected. The clinical course was characterized by depression, mild diarrhoea, torticollis, opisthotonus, paralysis and trembling. Histopathological examination of 13 pigeons revealed generalized severe granulomatous and necrotizing meningoencephalitis and myositis with sarcosporidian cysts. Light and transmission electron microscopy identified cysts in heart and skeletal muscle of 1 to 2 mm in length and 20 to 50 µm in width. These were subdivided into small chambers by fine septae and filled with lancet-shaped cystozoites (7.5×1.5 µm) and dividing metrocytes, which is characteristic for Sarcocystis. The cysts had smooth walls and were devoid of protrusions typical of S. falcatula. Polymerase chain reaction amplification and sequencing of the internal transcribed spacer region (ITS-1) and the complete 28S rRNA identified a novel Sarcocystis species with only 51% ITS-1 nucleotide sequence similarity with S. falcatula. A phylogenetic comparison of the 28S rRNA revealed close sequence homologies with Frenkelia microti, Frenkelia glareoli and Sarcocystis neurona. The clinical, histopathological, electron microscopic and genetic data are unlike any previously described protozoan infections in pigeons, suggesting a novel, severe disease due to an as yet undescribed Sarcocystis species.

Sarcocystis Species Lethal for Domestic Pigeons

A large number of Sarcocystis spp. infect birds as intermediate hosts, but pigeons are rarely affected. We identified a novel Sarcocystis sp. that causes lethal neurologic disease in domestic pigeons in Germany. Experimental infections indicated transmission by northern goshawks, and sequence analyses indicated transnational distribution. Worldwide spread is possible.