Submitted to: NE-60 Regional Meeting
Publication Type: Experiment Station
Publication Acceptance Date: April 1, 2001
Publication Date: N/A
Interpretive Summary: Avian coccidiosis is caused by several distinct species of Eimeria parasites which cause severe damage to the intestine. Ability to control coccidiosis will reduce the estimated economic losses of less than 600 million dollars. In order to develop novel control strategy against coccidiosis, better understanding of host immune system and the immunobiology of host parasite interaction is needed. In this report, ARS scientist investigated the genetic basis for the control of coccidiosis. The result showed that a host gene which is located on the chromosome 1 influences host response to parasites. Furthermore, few chicken cytokine genes have been identified and their role in host resistance to coccidiosis has been verified. These results will enhance our understanding of host- parasite relationship in avian coccidiosis and would enhance our feasibility of developing novel control strategy against coccidiosis.
According to our results, oocyst shedding was the best indicator of disease resistance to avian coccidiosis. First, the parameter is unique regarding to the disease, and it makes biological sense. It is generally, agreed that the birds susceptible to the disease are expected to shed more oocysts post inoculation than those are resistant. Second, oocyst shedding was independent on the sexes or the body weight. Third, oocyst shedding displayed the highest correlation with the body weight gain after the acute phase of the disease, e.g. from Day 6 to Day 9 PI than in any other periods. Cytokines such as IFN and IL-2 have been used to enhance cytotoxic T cell activity against human tumors in vitro and in vivo and both have been approved for clinical use to treat certain human cancers. In the case of avian coccidiosis, we have shown previously that TCR+ cells and natural killer cells mediating CMI to coccidiosis were activated following in vivo immunotherapy with recombinant chicken IL-2 protein. Chicken IL-2 stimulates chicken lymphocytes, aid in the establishment of NK and T cell cultures, and enhance in vivo resistance of infection. It is considered that chicken IL-2 plays a role in the chicken immune system virtually identical to that of mammalian IL-2 in mammalian immune systems. Development of ELISA for the measurement chicken IL-2 in serum and intestinal secretion will be of great advantage to investigations of IL-2 effects on the immune function of normal chickens and various diseased chickens.