Experimental conversion of virulent RH Toxoplasma gondii tachyzoites in vitro

We aimed to induce conversion of RH-stain tachyzoites to bradyzoites by changing the pH of the culture medium. Alkalization of the medium to pH 8 induced morphological changes in the cultured tachyzoites. The majority of the organism increased in size and changed from a regular crescent shape to a rounded or ovoid shape. Cyst-like structures were formed. Using a computerized image analyser, significant differences in the size of the whole organisms and in their nuclei were observed compared to the control group. The converted organisms also showed significant differences from the control group by quantitative DNA analysis, and did not infect mice

Detection of Cryptosporidium parvum antigen by co-agglutination test and ELISA

Confirmation of the presence of Cryptosporidium in environmental samples is laborious, costly and often difficult. We report here a simple and economic slide agglutination test [co-agglutination test] for detecting cryptosporidial antigen in stool, serum and water. The results show that as a screening method co-agglutination is clearly superior to enzyme-linked immunosorbent assay [ELISA] and modified Ziehl-Neelsen staining, although ELISA is more accurate. The co-agglutination test is recommended for application as a new tool for detecting cryptosporidial antigen in large-scale epidemiological surveys

Coccidial infection in immunosuppressed mice: prophylaxis and treatment with dehydroepiandrosterone

Cryptosporidiosis and toxoplasmosis are diseases caused by opportunistic coccidial parasites that can lead to life-threatening infection in immunocompromised patients. We evaluated dehydroepiandrosterone as prophylaxis and therapy in immunosuppressed mice infected with Cryptosporidium parvum and avirulent Toxoplasma gondii. Mice were infected with either Cryptosporidium oocysts or Toxoplasma cysts. Assessment was by mortality rates, parasitic counts and electron microscopic studies. Mortality rates were significantly reduced in all treated groups. A significant reduction in the cryptosporidial oocyst count in stool and intestinal villi and in Toxoplasma cysts in the brains of infected mice was observed in all the groups. The effect of the drug was greater when given prior to infection