PARASITIC DISEASE - link.springer.com DISEASE Sarcocystosis of the Skeletal and Cardiac Muscle, Mouse l.P.Dubey Synonym. Sarcosporidiosis. Gross Appearance Some Sarcocystis species
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
PARASITIC DISEASE
Sarcocystosis of the Skeletal and Cardiac Muscle, Mouse
l.P.Dubey
Synonym. Sarcosporidiosis.
Gross Appearance
Some Sarcocystis species form grossly visible sarcocysts (Greek: sarco = flesh, kystis = bladder) in skeletal muscle of mice (Fig. 186). Grossly visible sarcocysts are dull-white, thread-like structures, replacing as much as 25% of the muscle mass. Heavily infected limb muscles bulge, and mice may have difficulty walking.
Microscopic Appearance
Sarcocysts are located within myocytes and usually cause no host reaction (Fig. 187). However, some intact sarcocysts are surrounded by mononuclear cells. The rupture of sarcocysts may result in severe granulocytic to mononuclear cell infiltrations (Ruiz and Frenkel 1976), followed by fibrosis (Figs. 188, 189). Sarcocysts may disappear completely within 3-6 months after infection.
Ultrastructure
Sarcocysts are located within myocytes at all stages of development. They are separated from the host cell cytoplasm by a parasitophorous vacuole. The parasitophorous vacuolar membrane bears numerous small bleb-like protrusions into the cytoplasm of the host cell (Fig. 190). Immediately adjacent to this membrane is the ground substance, which is continued as septa inside the sarcocyst. Two types of zoites are found in the sarcocyst. The globular zoites at the periphery are metrocytes (mother cells), and they are the only zoites present in immature sarcocysts. As the sarcocyst matures metrocytes divide into
Fig.186. Thread-like sarcocysts in skeletal muscles, mouse. (Courtesy of E. C. Powell) Unstained
two, forming banana-shaped zoites called bradyzoites or cystozoites (Figs. 187, 190). Bradyzoites are about 15 x 3 11m and contain periodic acid Schiff-positive granules. The parasitized myocyte surrounds sarcocysts that are up to 150 11m in diameter and several millimeters long. The host cell cytoplasm undergoes partial degeneration and is compressed by the sarcocyst. The myofibrils disintegrate and may become arranged in groups. Lines are dis-
Fig.1S7 Cross section of a sarcocyst in a myocyte, mouse. Note thin sarcocyst wall (SCW), numerous banana-shaped bradyzoites (B), and metrocytes (M). Giemsa, x 750
Table 9. Summary of Sarcocystis species in house mouse (Mus musculus). (Modified from Dubey et al. 1989)
Sarcocystis Intermediate host species
Maximum Schizonts in length of sarcocysts
S. muris Railliet 1886; Several centimeters Hepatocytes Labbe 1899
S. dispersa Cerna et al. 1978 Microscopic Hepatocytes
S. crotali Entzeroth et al. 1985 4mm ?
S. scotti Levine and Tadros 1980? ?
S. sebeki Tadros and Larrman 1976 Several centimeters ?
S. dirumpens Hafner and Matuschka 1984 25 mm ?
S. muriviperae Matuschka et al. 1987 8 mm Hepatocytes
Barn owl (Tyto alba), masked owl (Tyto novae hollandiae)
Mojave rattlesnake (Crotalus scutylatus)
Tawny owl (Strix aluco)
Tawny owl (Strix aluco)
Snakes of the genus Bitis Palestinian viper (Vipera palaestinae)
rupted and mitochondria accumulate in the cytoplasm around the parasitophorous vacuolar membrane (Sheffield et al. 1977; Viles and Powell 1976, 1981).
guished from Sarcocystis spp. by its structure. The tissue cysts of T. gondii are always microscopic ( < 100 !lm), the cyst wall is smooth, and there are no septa. The predominant lesion in toxoplasmosis is necrosis and the lesion is more severe in the brain.
Differential Diagnosis
Myositis can also be caused by toxoplasmosis. However, Toxoplasma gondii is easily distin-
Sarcocystosis of the Skeletal and Cardiac Muscle, Mouse 167
Fig.188 (above). Longitudinal section of skeletal muscle, mouse. Numerous intact sarcocysts on top and degenerating sarcocysts below. H & E, x 75
Etiology and Frequency
The house mouse (Mus musculus) is host for seven speces of Sarcocystis (Table 9). Sarcocystis spp. have an obligatory prey-predator two-host life cycle (Fig. 191). Asexual stages develop only in the intermediate host, which in
Fig.189 (below) . Cross section of skeletal muscle, mouse. Degenerating (arrow) and intact sarcocysts surrounded by granulocytes and mononuclear cells. H & E, x 150
nature is often a prey animal (mouse). Sexual stages develop only in the definitive host, which is carnivorous. Sarcocystis muris, which completes its life cycle in the domestic cat (or ferret) and the house mouse (Ruiz and Frenkel 1976; Rommel 1979; Rommel et al. 9181), will be used as an example. The cat becomes infected by eat-
ing infected mice containing mature sarcocysts. Bradyzoites liberated from the sarcocyst penetrate cells of the mucosa of the small intestine of the cat and transform these into either female (macro-) or male (micro-) gamonts. The microgamonts divide into several biflagellated microgametes. These microgametes are motile and penetrate the female gamont. A wall is formed around the resulting zygote to form the oocyst. Oocysts sporulate in the lamina propria of the small intes-
TEM, x 6273. Inset shows a high magnification of PVM. Note bleb-like protrusions (arrow). TEM, x 29573
tine. Sporulated oocysts contain two sporocysts, each with four sporozoites. Sporulated oocysts, or sporocysts, measuring about 10 x 8 ~m, are excreted in the feces. Mice become infected by ingesting food contaminated with sporocysts. The sporozoites excyst in the intestinal lumen and reach the liver via the circulation. The sporozoite penetrates a hepatocyte and the nucleus of the parasite then divides into several nuclei. Finally each nucleus is surrounded by cytoplasm which becomes confined
Sarcocystosis of the Skeletal and Cardiac Muscle, Mouse 169
SPOROCYST
INTERMEDIA TE HOST Mouse
Fig.191. Life cycle of Sarcocystis muris
by membranes to form merozoites. Merozoites are often arranged in a rosette within a schizont. Schizonts are seen in the liver 11-17 days after infection of the mouse. Unlike sarcocysts, schizonts locate directly in the host cell cytoplasm without a parasitophorous vacuole. Merozoites liberated from schizonts enter the circulation and penetrate myocytes to form sarcocysts. Earliest sarcocysts are seen around the 28th day after inoculation. Sarcocysts become infections for the definitive host (cat) between 65 and 76 days following inoculation (Ruiz and Frenkel 1976). Sarcocysts begin to be seen with the naked eye at 80 days and are easily visible at 100 days after inoculation. They start degenerating during the 4th month postinfection and may completely disappear by 6 months postinfection in some mice. However, some mice remain infected for more than 12 months, nearly for the life of the mouse. Sarcocysts are found only in skeletal muscles and not in the myocardium of mice. Sarcocystis muris infections are rare in mice raised under modern controlled conditions and their presence indicates contamination of bedding or food by feline feces.
Comparison with Other Species
More than 100 species of Sarcocystis have been described and they are generally host specific for their intermediate hosts (Dubey et al. 1989; Le-
vine 1986). Certain species of Sarcocystis can cause serious disease in cattle, sheep, goats, pig, and mule deer. Although all species of Sarcocystis have an obligatory two-host life cycle, Sarcocystis species in livestock form schizonts in endothelial cells of blood vessels whereas in murine species schizonts are formed in hepatocytes.
References
Dubey JP, Speer CA, Fayer R (1989) Sarcocystosis of animals and man. CRC, Boca Raton
Levine ND (1986) The taxonomy of Sarcocystis (protozoa, apicomplexa) species. J Parasitol72: 372-382
Rommel M (1979) Das Frettchen (Putorius putorius Juro), ein zusatzlicher Endwirt flir Sarcocystis muris. Z Parasitenkd 58: 187-188
Rommel M, Schwerdtfeger A, Blewaska S (1981) The Sarcocystis muris infection as a model for research on the chemotherapy of acute sarcocystosis of domestic animals. Zentralbl Bakteriol Mikrobiol Hyg [A] 250: 268-276
Ruiz A, Frenkel JK (1976) Recognition of cyclic transmission of Sacocystis muris by cats. J Infect Dis 133: 409-418
Sheffield HG, Frenkel JK, Ruiz A (1977) Ultrastructure of the cyst of Sarcocystis muris. J Parasitol63: 629-641
Viles JM, Powell EC (1976) The ultrastructure of the cyst wall of a murine Sarcocystis. Z Parasitenkd 49: 127-132