39 1 , 17 25 (2012) Korean J. Poult. Sci. Vol.39, No.1, 17 25 (2012) http://dx.doi.org/10.5536/KJPS.2012.39.1.017 17 Effects of Various Field Coccidiosis Control Programs on Host Innate and Adaptive Immunity in Commercial Broiler Chickens Kyung-Woo Lee, Hyun S. Lillehoj , Seung I. Jang and Sung-Hyen Lee Animal Parasitic Diseases Laboratory, Animal and Natural Resources Institute, Agricultural Research Service, USDA, Beltsville, MD 20705 ABSTRACT Coccidiosis control programs such as vaccines or in-feed anticoccidials are commonly practiced in the poultry industry to improve growth performance and health of commercial broiler chickens. In this study, we assessed the effects of various coccidiosis control programs (e.g., in ovo vaccination, synthetic chemicals, and antibiotic ionophores) on immune status of broiler chickens vaccinated against infectious bronchitis virus and Newcastle disease virus (ND) and raised on an Eimeria- contaminated used litter. In general, the levels of α-1-acid glycoprotein, an acute phase protein, were altered by the treatments when measured at 34 days of age. Splenocyte subpopulations and serum antibody titers against ND were altered by various coccidiosis control programs. In-ovo-vaccinated chickens exhibited highest mitogenic response when their spleen cells were stimulated with concanavalin A (Con A) at 7 days of age. It is clear from this study that the type of coccidiosis control pro- gram influenced various aspects of innate and adaptive immune parameters of broiler chickens. Further studies will be necessary to delineate the underlying relationship between the type of coccidiosis control program and host immune system and to understand the role of other external environmental factors such as gut microbiota on host-pathogen interaction in various disease control programs. (Key words : infectious bronchitis virus, Newcastle disease virus, coccidiosis control program, immune status, broiler chickens) To whom correspondence should be addressed : Hyun.Lillehoj@ARS.USDA.GOV Avian coccidiosis is major parasitic disease of high econo- mic concern in the poultry industry worldwide and is caused by at least seven distinct species of Eimeria apicomplexan protozoa that infect the various areas of intestinal mucosa. The economic loss for avian coccidiosis is estimated to be more than $3 billion worldwide (Williams, 1999) and this cost includes in-feed medication, mortality, impaired growth rate, inefficient feed utilization and reduction in egg produc- tion. According to the previous reports, the Eimeria spp. prevalence has been estimated in more than 50% of the flock level around the world (Williams et al., 1996; Al-Natour et al., 2002; Haug et al., 2008; Nematollahi et al., 2009; Sun et al., 2009; Lee et al., 2010a). In general, the majority of Ei- meria-infected chickens are afflicted by multiple species of Eimeria with the most prevalent species including E. tenella, E. praecox, E. acervulina, and E. maxima. It has been a common practice to implement vaccination against coccidiosis or to add anti-coccidial feed additives either in the form of synthetic chemicals or antibiotic iono- phores to control coccidiosis by the poultry industry (Williams, 2005; Lee et al., 2009). Although coccidiosis control pro- grams have been widely used in poultry production world- wide, their impact on the developing host immune system and on host-pathogen interaction has not been studied so far. Because there are scientific data that show the influence of gut microbiota, drugs, and dietary feed-additives (e.g., probio- tics and phytonutrients) on developing host immune system (Lee et al., 2010b; Yin et al., 2010; Crhanova et al., 2011; Lee and Lillehoj, 2011; Lee et al., 2011a), it is important to gain better understanding of how these factors affect host ability to elicit immune response to field pathogens. Recent studies document significant immunoregulatory in- fluence of the gut commensal bacteria on host immune status. For example, Bifidobacteria infantis or Faecalibacterium praus- nitzii induced Foxp3 + T regulatory cells and increased the ex- pression of the anti-inflammatory cytokine, interleukin (IL)- 10, whereas segmented filamentous bacteria (Candidatus ar- thromitus) induced T-helper (Th)17 cell development (Lee