Effect of household bleach on the structure of the sporocyst wall of Toxoplasma gondii

Toxoplasma gondii oocysts are responsible for food- and water-borne infections in humans worldwide. They are resistant to common chemical disinfectants, including chlorinated products, presumably due to the structure and molecular nature of the oocyst wall but also the sporocyst wall. In this study, we used fluorescence microscopy and transmission electron microscopy to characterise the structure of both the oocyst and sporocyst walls, exposed to household bleach. Bleach removed the outer layer of the oocyst wall and the outer layer of the wall of sporocysts exposed due to rupture of the oocyst wall. The loss of the outer sporocyst wall layer was associated with a decrease in its autofluorescence, which can be linked to the degradation of dityrosine cross-link proteins, and loss of Maclura pomifera lectin-reactive glycoproteins. This study suggests that the inner layers of the oocyst and sporocyst walls are the main structures responsible for the resistance of the parasite to household bleach.

Endogenous stages of Choleoeimeria baltrocki (Daszak et Ball, 1991) n. comb. infecting the gall bladder of gold skink, Eumeces schneiderii Daudin, 1802 from Egypt

Examination of 98 gold skink, Eumeces schneiderii Daudin, 1802 from Alexandria and Marsa-matroh Governorates, Egypt revealed oocysts of Choleoeimeria baltrocki (Daszak et Ball, 1991) n. comb. in the gall bladder and faeces. The prevalence of the infection was 40.8%. Sporulated oocysts were found in the faeces and the gall bladder contents. Sporulated oocysts were tetrasporocystic, cylindrical, reaching a mean of 38.7 (36–42) × 19.9 (17–25) μm with bilayered smooth and colourless wall. The dizoic sporocysts were subspherical and measuring 10.8 (9.5–13) × 9.3 (8–10.5) μm with a large globular sporocyst residuum. Sporocyst wall was bilayered joined by meridional suture. Sporozoites were crescent-shaped, blunt at one end and slightly tapered at the other. Endogenous stages (meronts, gamonts, gametes and young oocysts) were confined to the gall bladder epithelium and the infected cells were hypertrophied. Based on the morphological features of the exogenous stages and endogenous development of the present parasite, its generic affiliation was revised and placed into the genus Choleoeimeria.

Ultrastructure of the life-cycle stages of Goussia janae (Apicomplexa, Eimeriidae), with X-ray microanalysis of accompanying precipitates

The ultrastructural features of the life-cycle stages of Goussia janae from the intestinal epithelium of the dace Leuciscus leuciscus and chub L. cephalus are described. All merogonial, gamogonial, and early sporogonial stages were localized in the microvillar region in an intracellular and extracytoplasmic position, covered by closely apposed enterocyte and parasitophorous vacuole membranes. Two types of location in the host cell were observed: (i) a more frequent "monopodial" type with a single zone of attachment to the host-cell cytoplasm, and (ii) a "spider-like" type with several isolated zones of attachment. Merozoites were formed by either ecto- or endo-merogony. Microgamonts produced elongated biflagellate microgametes at their periphery. The oocyst wall, produced exclusively by the parasite, was formed at the end of the intracellular phase of the life cycle. Exogenous sporulation resulted in the formation of elongated sporocysts with a thin sporocyst wall bearing a longitudinal suture accompanied by a narrow membranaceous veil. In the cytoplasm and cytoplasmic and parasitophorous vacuoles of the parasite, fine, dense precipitates were present. X-ray microanalysis of these precipitates from osmicated and non-osmicated samples revealed high levels of Ca and P, indicating the possible presence of hydroxyapatite.

Further observations on the sporogony of Eimeria sardinae in the testis of the herring Clupea harengus L.

Sporocyst formation commences with division of the sporoblast nucleus, after which two sporozoites develop, one at each end of the sporoblast. A thickening beneath the limiting unit membrane of the sporoblast is the first indication of the sporozoite pellicle forming. This subsequently develops into a cone-shaped structure, which becomes the anterior end of the sporozoite as it separates from the sporocyst residuum. The sporozoites elongate as they mature, and the sporocyst residuum, containing amylopectin and refractile granules, becomes smaller. A typical apical complex is present at the blunt anterior end of the sporozoite. A homogeneous area containing paracrystals is present in both the sporoblast and the sporozoite. There are no refractile granules in the sporozoite. The sporocyst wall is thin and contains no mechanism for releasing the sporozoite, such as a Stieda body or suture.

Coccidians in the liver and testis of the herring Clupea harengus L.

The coccidians Goussia clupearum from liver and Eimeria sardinae from testis of herring caught in waters near Nova Scotia were studied by light and electron microscopy. Unsporulated and sporulatcd oocysts were the most frequently encountered stages. Oocyst walls of both species were thin and closely apposed to the host cell. At least a part of the oocyst wall appeared to serve also as the boundary of the parasitophorous vacuole. In G. clupearum, membranes lining parasitophorous vacuoles of various stages seemed to be involved in host–parasite nutrient transfer. Wall-forming bodies were found in the sporont of E. sardinae, and presumptive wall-forming bodies were found in the sporont of G. clupearum. The sporocyst wall of G. clupearum appeared to consist of two valves. The wall had a thick transversely striated inner layer and a thin outer layer consisting of several closely apposed membranes. The lamellated membranes extended from the outer layer. The sporocyst wall of E. sardinae was thin and consisted of three loosely organized membranes. The sporocysts of neither species had a Stieda body. Goussia clupearum, which often elicited an intense host reaction, infected 85% of mature fish whereas E. sardinae infected 90–100%. Replacement of hepatic tissue by G. clupearum could stress fish and replacement of testicular tissue by E. sardinae could reduce sperm production, thus detrimentally affecting herring stocks.