Sarcocystis Hirsuta Research Articles

Ultrastructural differentiation between sarcocysts of Sarcocystis hirsuta and Sarcocystis hominis

The ultrastructure of macroscopic (2-7 mm) Sarcocystis hirsuta sarcocysts from naturally infected cattle from New Zealand was compared with the ultrastructure of 222-day-old S. hominis in experimentally infected cattle in the United States. The villar protrusions of S. hirsuta were approximately 8 microns long, constricted at the base, expanded laterally in the mid-region and tapered distally. Some of the villar tips were folded to form two to four conical projections. The distal portion of the villar protrusions was bent at an angle of 45-90 degrees to the sarcocyst surface. The villar core contained numerous microfilaments and rows of electron-dense granules. The villar protrusions of S. hominis were cylindrical, oriented nearly perpendicularly to the sarcocyst surface, not constricted at their base and contained relatively few electron-dense granules. Although the sarcocysts of S. hirsuta were indistinguishable from those of S. hominis by light microscopy, they were distinguishable ultrastructurally.

The structure and identity of macroscopically visible Sarcocystis cysts in cattle.

Macroscopically visible Sarcocystis spp. cysts isolated from the skeletal muscle of slaughtered cattle were examined by light- and electronmicroscopy. Transmission experiments involving cats, dogs and a human volunteer were also carried out. The cysts could only be transmitted to cats which establishes them with a high degree of certainty as Sarcocystis hirsuta. The cyst wall (including protrusions) ranged from 3.3 to 7.0 micron in thickness and the individual cyst wall protrusions from 1.2 to 2.6 micron in width. Transmission and scanning electronmicroscopy revealed previously undescribed features of the cyst wall. It appears that, with increasing age, the cyst wall protrusions become larger and develop a highly irregular surface. Their attachments to the cyst wall are slender and widely spaced indicating that growth of the cyst continues without the formation of new protrusions. Within the protrusions the fibrils become disorganised and numerous osmiophilic granules appear. It is evident that major changes in the structure of sarcocysts can occur with age.

Protozoan Nomina dubia: To Arbitrarily Restrict or Replace. The Case of Sarcocystis spp.

The original descriptions of some parasitic protozoa lack sufficient information to recognize where they may belong among current taxa. Descriptions were often made from fresh, unpreserved specimens and no type specimen remains. Some of the original names of Sarcocystis (Apicomplexa) were given to seemingly similar structures in a host. It is now impossible to apply them reasonably, and with any degree of scientific certainty, to any one of the 2-3 taxa of Sarcocystis known from each of several hosts and known to be host-specific. As a consequence, the original names became nomina dubia, names not certainly applicable to any known taxon. What do we do with these nomina dubia? The International Code of Zoological Nomenclature (1964) does not discuss them expressly, but implies that such names remain available (Art. 17, no. 29). Heydom et al. (1975) decided to give all the new taxa of Sarcocystis new names, in part, because there was no scientific basis for assigning any of the old names, and in part, because if a decision could only be arbitrary, the outcome should be clear, rather than ambiguous. Others suggest the arbitrary use of one of the old names for one of the new taxa, giving the other taxa new names (Melville, 1980). The issue is between arbitrariness in the interest of preserving an old specific name, and the feeling that arbitrariness is scientifically objectionable. Although either method promises precision, events lead one to question whether both means are similarly capable of achieving it. The following provides a specific illustration. When it was thought that there was only one species of Sarcocystis in cattle, Sarcocystis hirsuta Moule, 1888 had priority, and the following were synonyms: Miescheria cruzi Hasselmann, 1926, S. fusiformis Railliet, 1897 of Babudieri

Protective immunity against clinical sarcocystosis in cattle

Five experiments involving 50 calves ( Bos taurus) were conducted to determine if oral infection with sporocysts of the pathogen Sarcocystis cruzi or the non-pathogen Sarcocystis hirsuta would stimulate development of a protective immunity against illness or death from challenge infection with large numbers of S. cruzi sporocysts. Four experiments involved Holstein calves housed in individual pens in isolation buildings; one experiment involved Hereford calves on an open range. Calves infected with 50 000 to 100 000 S. cruzi sporocysts were protected from illness and death that would have resulted from challenge infections with 250 000 or 500 000 S. cruzi sporocysts given 70–252 days later. Calves treated with the anticoccidial drug amprolium from 21 to 35 days after being given an immunizing infection with S. cruzi to reduce clinical signs of the immunizing infection were also protected. Non-immunized calves and those given S. hirsuta sporocysts were not protected.

Clinical Sarcocystosis in Calves Fed Sarcocystis Hirsuta Sporocysts from Cats

Lesions of sarcocystosis were studied in 14 calves necropsied between seven and 110 days after inoculation with 5000 to 25 million sporocysts of Sarcocystis hirsuta from cats. Calves developed fever, anemia, and diarrhea between 11 and 30 days after inoculation. The development of first generation meronts in arteries of small intestine, mesentery, and mesenteric lymph nodes seven to 25 days after inoculation was associated with vascular occlusion and necrosis of associated tissues. The development of second generation meronts in capillaries of striated muscles 15 to 23 days after inoculation was associated with necrosis, edema, and nonsuppurative myositis in heart and other muscles. Sixty-two days after inoculation lesions were reduced to focal areas of granulomatous inflammation around degenerating sarcocysts in striated muscles, but not in the heart.

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.