Early developmental stages of Gregarina steini Berndt, 1902 from the intestine of Tenebrio molitor larvae were studied by transmission electron microscopy. The formation and structure of the eugregarine attachment site were compared with comparable features found on the feeder organelle of Cryptosporidium muris Tyzzer, 1907, from the stomach of experimentally infected rodents. The similarity of the attachment strategy between both organisms was revealed. The membrane fusion site in G. steini, formed by the trophozoite plasma membrane, host cell plasma membrane and a membrane-like structure limiting the cortical zone of the epimerite, resembles the Y-shaped membrane junction between the host cell plasma membrane, the trophozoite plasma membrane and membrane surrounding the anterior vacuole in C. muris. The anterior vacuole of C. muris appears to be the precursor of the feeder organelle and its structure is very similar to the epimeritic bud and the cortical zone of G. steini trophozoites. In both investigated organisms, the apical complex disappears early during cell invasion. The possibility of the epicellular location of Cryptosporidium on the surface of host cells is discussed.

Abstract.We investigated the genotypes of Cryptosporidium infecting red squirrels (Sciurus vulgaris L.) in two areas of the Western Alps in Italy. Examination of 141 faecal samples from 70 red squirrels revealed oocysts of Cryptosporidium in 17 animals (24.3%). Based on 18S rRNA gene sequencing, two genotypes of Cryptosporidium species were found: 15 squirrels were positive for the Cryptosporidium ferret genotype and 2 for the Cryptosporidium chipmunk genotype I. The occurrence and intensity of Cryptosporidium infection did not differ between the study areas or sex. More than 85% of the positive animals were adults; however no difference was found between Cryptosporidium infection in the juvenile and adult age groups. Oocysts of the Cryptosporidium ferret genotype measured 5.5 ± 0.3 × 5.2 ± 0.2 µm (shape index 1.06) and the Cryptosporidium chipmunk genotype I 5.8 ± 0.3 × 5.4 ± 0.3 µm (shape index 1.07). Neonatal and adult CD1 and BABL/c mice inoculated with 1 × 10 3 fresh oocysts of both genotypes did not produce detectable infection.

Usutu virus (USUV) is a flavivirus (Flaviviridae: Flavivirus) of an African origin transmitted among its natural hosts (diverse species of birds) by mosquitoes. The virus was introduced multiple times to Europe where it caused mortality of blackbirds (Turdus merula) and certain other susceptible species of birds. In this study, we report detection of USUV RNA in blackbirds, Culex pipiens and Cx. modestus mosquitoes in the Czech Republic, and isolation of 10 new Czech USUV strains from carcasses of blackbirds in cell culture. Multiple lineages (Europe 1, 2 and Africa 3) of USUV were found in blackbirds and mosquitoes in the southeastern part of the country. A single USUV lineage (Europe 3) was found in Prague and was likely associated with increased mortalities in the local blackbird population seen in this area in 2018. USUV genomic RNA (lineage Europe 2) was detected in a pool of Cx. pipiens mosquitoes from South Bohemia (southern part of the country), where no major mortality of birds has been reported so far, and no flavivirus RNA has been found in randomly sampled cadavers of blackbirds. The obtained data contributes to our knowledge about USUV genetic variability, distribution and spread in Central Europe.

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