Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 1, 2000
Publication Date: N/A
Interpretive Summary: Parasites which infect the intestine cause significant economic losses to the poultry industry since the infection can cause a malabsorption of the nutrients and also poor feed utilization. The ARS scientists have been studying coccidiosis, a disease caused by the protozoan parasite called coccidia, to develop a new control strategy against this parasites. Coccidiosis costs the industry more than $600 million annually in prophylactic treatment. Drugs have been used to prevent coccidiosis. However, with the increasing concerns over the development of drug-resistant coccidia parasites in the field, a new control strategy is critically needed. In this paper, ARS scientists analyzed different disease parameters for avian coccidiosis in an attempt to develop a novel control strategy based upon DNA-marker assisted genetic selection. ARS scientists in collaboration with scientists at University of Delaware and Purdue Farms demonstrate that various factors associated with parasites an host genetics influence coccidiosis susceptibility and resistance. The knowledge which is presented in this paper will enhance the feasibility of developing a new control strategy for avian coccidiosis and will reduce the major stress factor that can lead to a lowered performance and a lowered production efficiency in livestock and poultry.
To determine an optimal dose for coccidial inoculation and to evaluate parameters for genetic resistance/susceptibility in chickens, broilers were inoculated with four different doses of Eimeria maxima oocysts. Body weight gain, fecal oocyst output, plasma carotenoid, and interferon levels were measured at two different time periods post-infection. The results showed significant dose and sex effects on the parameters and interaction between dose and sex in some parameters. The measurements from chickens inoculated with of oocysts displayed the highest correlations among oocyst output, body weight gain, carotenoid, and levels. An infection index, calculated from the correlated parameters, displayed high correlations with the parameters. The infection index may be a better parameter for evaluating individual genetic resistance against coccidial infection.