Ethanol and isopropanol trigger rapid egress of intracellular Eimeria tenella sporozoites.

Egress from host cells is a vital step of the intracellular life cycle of apicomplexan parasites such as Toxoplasma gondii. This phenomenon has attracted attentions from many research groups. Previous studies have shown that ethanol could stimulate the release of microneme proteins by elevating intracellular Ca(2+) concentration of T. gondii, resulting in the parasite egress from host cells. However, little information about egress is known on Eimeria species, the causative agent of coccidiosis in poultry and livestock. In this report, we studied the effect of ethanol and isopropanol on the egress of eimerian parasites. Eimeria tenella sporozoites cultured in primary chicken kidney cells were treated with ethanol and isopropanol, then the egressed parasites were analyzed. Ethanol and isopropanol could induce the rapid egress of E. tenella sporozoites from host cells. No substantial damage was found in parasite-egressed host cells. Compared to the freshly isolated sporozoites, the re-invading ability and reproductivity of the egressed parasites significantly decreased by 43.4 and 44.1 % individually. We also found that fewer sporozoites egressed from host cells when the parasites developed for a longer time before the alcohol treatment. These results demonstrate an in vitro egress mode different from that of T. gondii, facilitating the deciphering of the mechanisms of egress of eimerian parasites.