Monitoring coccidia in commercial broiler chicken flocks in Ontario: comparing oocyst cycling patterns in flocks using anticoccidial medications or live vaccination

Abstract

Coccidiosis, the parasitic disease caused by Eimeria spp., is controlled during broiler chicken production through the inclusion of in-feed anticoccidial medications. Live-coccidiosis vaccination has become an increasingly common alternative to these medications. Monitoring infections with Eimeria spp. in flocks can be accomplished through determining the concentration of oocysts excreted in the fecal material (i.e., oocysts per gram; OPG ). The purpose of our study was to sample commercial Ontario broiler chicken flocks at various times of the year to determine weekly OPG counts for flocks that use either an in-feed anticoccidial medication or a live-coccidiosis vaccine. Weekly sampling of 95 flocks from placement to market permitted documentation of oocyst cycling patterns typical of conventional and antibiotic-free flocks, and variation of these patterns in summer and winter. Medicated flocks had higher and later peak oocyst shedding compared with vaccinated flocks. Flocks reared in the summer peaked in oocyst shedding earlier than flocks reared in the winter. Despite what appears to be poorer coccidiosis control in the medicated flocks, the performance data were similar for these flocks compared with vaccinated flocks. This is the first study describing typical patterns of parasite shedding in Ontarian commercial broiler chicken flocks; these data will provide a baseline of expected Eimeria spp. infections in Canadian broiler chicken flocks to ensure optimal coccidiosis prevention.

Anticoccidial Vaccination Is Associated with Improved Intestinal Health in Organic Chickens

“…Together, and in combination with no diagnosed cases of coccidiosis among dead and culled chicken from vaccinated flocks, these results suggest that vaccination induced partially protective immune responses against Eimeria -induced lesions from around four WOA. These findings support previous reports from field studies in non-organic broilers [ 20 , 21 ].…”

Nutritional interventions to support broiler chickens during Eimeria infection

“…In all experimental groups, oocyst excretion peaked on d22 and declined after d28, which is consistent with the Eimeria infection dynamics in broiler flocks as a result of increasing immunity ( Jenkins et al, 2017 ; Snyder et al, 2021 ). On d14, d22, and d28, the total oocyst output was significantly lower in the PC compared to all treatments, except for the NC, suggesting that the dietary treatments as tested here had limited effects on reducing peak oocyst excretion.…”

“…Although clinical coccidiosis, sometimes followed by necrotic enteritis, does occur in commercial farms, on many farms, coccidiosis can remain subclinical. Moreover, flock infections start with relatively low doses at an early age, before chickens are exposed to high oocyst levels later in the production period ( Klinkenberg and Heesterbeek, 2007 ; Chapman et al, 2016 ; Snyder et al, 2021 ), making our infection model compliant to field conditions.…”

Automated enumeration of Eimeria oocysts in feces for rapid coccidiosis monitoring

“…Monitoring the efficacy of interventions has economic implications for the poultry producers and health implications for the birds ( Jenkins et al, 2017 ; Snyder et al, 2021 ). The World Association for the Advancement of Veterinary Parasitology ( WAAVP ) recommends measuring coccidia oocysts in feces or litter to understand field efficacy of interventional methods, using either the hemocytometer or McMaster method ( Holdsworth et al, 2004 ), but oocyst counts have not been used historically as a diagnostic tool.…”