Location: Animal Parasitic Diseases LaboratoryTitle: Eimeria oocyst concentrations and species composition in litter from commercial broiler farms during anticoccidial drug or live Eimeria oocyst vaccine control programs
Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2017
Publication Date: 3/9/2017
Citation: Jenkins, M.C., Parker, C.C., Ritter, D. 2017. Eimeria oocyst concentrations and species composition in litter from commercial broiler farms during anticoccidial drug or live Eimeria oocyst vaccine control programs. Avian Diseases. 61:214-220.
Interpretive Summary: Avian coccidiosis is an intestinal disease of poultry caused by protozoa in the genus Eimeria. Coccidiosis outbreaks are controlled by either medication of poultry feed with anti-coccidial drugs or vaccination of day-old chicks with low doses of live Eimeria oocysts. While Eimeria oocysts are ubiquitous in litter, there have been no studies tracking changes in Eimeria oocysts levels over time during anticoccidial drug or vaccine programs, nor any analyses done on how oocyst levels impact broiler performance during the 7-8 weeks of growout. In the present study, it was found that Eimeria oocyst levels in litter often do not follow an expected pattern with peak concentrations sometimes appearing later in growout. This data suggest that Eimeria drug resistance of incomplete vaccination at the hatchery may affect Eimeria oocyst levels in litter which makes controlling avian coccidiosis difficult. The data also reveals a correlation between chick mortality and levels of one Eimeria species, namely E. maxima. Of interest was a lack of correlation between E. maxima oocyst levels and performance parameters such as weight gain and feed utilization efficiency. This data suggest that chicks surviving an coccidia infection early in life can overcome the effects by the time of harvest at 7-8 weeks of age. It is unknown if this is true for younger broilers destined for the fast-food market. This information is useful for poultry veterinarians because it provides a clue into Eimeria drug resistance and non-uniform/inefficient vaccine application, and possible reason for increased mortality at 2-4 weeks of age.
Technical Abstract: The purpose of this study was to determine if Eimeria oocyst concentrations and species composition in commercial broiler house litter changed during different cycles of anticoccidial drug (ACD) or live Eimeria oocyst vaccine (VAC) control programs, and if there was a correlation between Eimeria oocyst levels and broiler performance. Litter samples were collected from a total of 15 different broiler farms encompassing a total of 45 individual houses during at least one complete growout cycle over a 21 month period. Of these 15 broiler farms, 3 were followed for the entire 21 month period spanning 3 ACD and 4 VAC cycles. Samples were collected at 2, 4, and 7-8 weeks of growout corresponding to starter, grower, and withdraw periods of the ACD cycle. On a number of occasions, litter samples were obtained just prior to chick placement. Eimeria oocysts were isolated from all samples, counted by microscopy and extracted for DNA to identify Eimeria species by ITS1 PCR. In general, Eimeria oocyst concentration in litter reached peak levels at 2-4 weeks of growout regardless of coccidiosis control measure being used. However, peak oocyst numbers were sometimes observed later in growout at 7-8 weeks possibly indicating some level of Eimeria drug resistance or incomplete vaccine coverage after hatch. Eimeria maxima, E. acervulina, E. praecox, and E. tenella were generally present in all samples, and no difference in the species composition was noted between houses on a particular farm. While Eimeria species composition was identical among houses, high Eimeria oocyst levels were randomly observed in one house compared to other houses in the same location. Of particular interest was the observed correlation between E. maxima oocyst numbers and chick mortality at different points of growout. However, no correlation was observed in E. maxima oocyst levels and the performance parameters adjusted feed conversion ratio and average daily weight gain. This study showed that understanding the dynamics of Eimeria oocyst levels and species composition in litter during ACD or VAC programs may provide insight into the effectiveness of coccidiosis control measures in commercial broiler production.