Location: Animal Parasitic Diseases
Title: Different susceptibilities of Eimeria acervulina, Eimeria maxima, and Eimeria tenella oocysts to dessication Authors
Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 25, 2013
Publication Date: N/A
Interpretive Summary: Avian coccidiosis is an intestinal disease of poultry caused by protozoan parasites in the genus Eimeria. Infection begins after chickens ingest Eimeria oocysts that have been shed by other chickens. With adequate oxygen supply and moisture, Eimeria oocysts can remain infectious for long periods of time in a poultry house. The purpose of the present study was to determine if the 3 major species of Eimeria, namely E. acervulina, E. maxima, and E. tenella, differed from one another in susceptibility to drying. This study was initiated because of our observing high levels of E. maxima in litter even though its reproductive potential is considerably lower than the other 2 Eimeria species. Indeed, E. maxima was able to withstand dessication for longer periods of time than both E. acervulina and E. tenella. Chickens ingesting E. maxima oocysts became infected even when E. maxima oocysts were stored for up to 3 days at poultry house conditions. E. acervulina and E. tenella oocysts stored for greater than 1 day were incapable of causing a clinical infection in chickens. This study provides at least one explanation on why E. maxima exists in high numbers in poultry litter even though its reproductive potential is low.
Technical Abstract: Outbreaks of avian coccidiosis may occur when susceptible chickens are raised on litter containing high concentrations of viable Eimeria oocysts. The purpose of this study was to compare the relative sensitivities of E. acervulina, E. maxima, and E. tenella oocysts to dessication. Sporulated E. acervulina, E. maxima, or E. tenella oocysts were incorporated into gelatin beads, and incubated at 32oC for 0, 1, 2, or 3 days. In vitro oocyst excystation rates were measured for each combination of Eimeria species and incubation time. Day-old broiler chicks were allowed to ingest the oocysts-containing beads, and total oocysts production was measured from days 5-8 post-inoculation. Although no effect on excystation was observed, E. maxima oocysts displayed greater resistance to drying compared to E. acervulina and E. tenella oocysts. E. acervulina oocysts production decreased by 2 orders of magnitude after 1 day, and was below detectable levels by 3 days incubation. E. tenella oocysts were slightly more resistant to drying in that a significant decrease in oocysts production was delayed until 2 days incubation, but was undetectable by 3 days incubation in gel beads. Eimeria maxima oocysts production remained high at all incubation times, displaying a slight decrease by 3 days incubation. These findings may explain in part the observed prevalence of E. maxima in litter from commercial poultry operations.