Viable Eimeria oocysts in poultry house litter at time of chick placement

Authors: Jenkins, Mark; Parker, Carolyn; Obrien, Celia; RITTER, DONALD - Mountaire Farms, Inc

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2019
Publication Date: 4/5/2019
Citation: Jenkins, M.C., Parker, C.C., Obrien, C.N., Ritter, D. 2019. Viable Eimeria oocysts in poultry house litter at time of chick placement. Poultry Science. https://doi.org/10.3382/ps/pez147.
DOI: https://doi.org/10.3382/ps/pez147

Interpretive Summary: Avian coccidiosis is a parasitic disease caused by protozoa in the genus Eimeria. Each year, the disease causes over $ 350 million loss in the U.S. alone, with losses exceeding $ 1.5 billion worldwide. The losses stem from lower performance (weight gain) poorer feed utilization efficiency, and the cost of controls, be it anticoccidial drugs or Eimeria vaccines. Generally the top layer of litter is removed from a poultry house after chicks have been removed for processing and the house is left vacant for 2-3 weeks to expose viruses and microorganisms in litter to high heat and low oxygen levels. However, Eimeria are well-adapted to withstand high temperatures (< 40oC) and anoxic conditions. Newly-hatched chicks once placed in a poultry house are thus exposed to large numbers of Eimeria parasites, but it is unknown whether these parasites are viable and infectious for chickens. In this study, it was found that nearly 50% of poultry houses at the time of chick placement contain viable Eimeria parasites, and that these oocysts are infectious. This is important because it reiterates the need to protect newly-hatched chicks against avian coccidiosis from the time they are placed in a poultry house and/or to devise a strategy for destroying Eimeria oocysts in litter during the 2-3 week down-time.

Technical Abstract: The purpose of this study was to determine if Eimeria oocysts recovered from litter at time of chick placement in commercial broiler houses contained oocysts that were infectious for chickens. Over 100 litter samples were collected from 30 poultry farms representing a total of 60 different broiler houses with 9 houses sampled more than once over 1.5 years. The samples were collected just before placement of newly-hatched chicks and after an anticoccidial drug (ACD) or Eimeria vaccine (VAC) program, and processed for counting oocysts followed by Eimeria species determination using ITS1 PCR. Broiler chicks were inoculated with recovered Eimeria oocysts to determine if the litter oocysts were viable and capable of causing patent infection. At placement, E. maxima (Emax) oocysts were detected in 74/75 houses after ACD program and 47/47 houses after VAC program. Eimeria acervulina, E. praecox, and/or E. tenella (Eapt) were detected in 75/75 houses after ACD program and 46/47 houses after VAC program. Viability testing revealed that 32.1% of broiler houses contained viable Emax oocysts, while 47.2% contained viable Eapt oocysts. During VAC programs, the concentration of Emax oocysts at placement and the total number of Emax oocysts shed by chickens in the viability study showed a very strong correlation (r = 0.83). Likewise, during ACD programs, the concentration of Eapt oocysts at placement and the total number of Eapt oocysts shed by chickens in the viability study showed a strong correlation (r = 0.62). In general, Eimeria oocyst levels at placement and number of viable oocysts shed by chickens in the viability study were similar among houses on the same farm. However, the number of Eimeria oocysts shed in the viability studies was considerably less than expected based on the number of oocysts given. These data suggest that nearly 100% of all poultry houses contain Emax and Eapt oocysts at placement with 30-50% of the houses containing viable Eimeria oocysts thus possibly representing a source of the protozoa to newly-hatched chicks.