Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/19/2010
Publication Date: 4/29/2010
Citation: Miska, K.B., Schwarz, R.S., Jenkins, M.C., Rathinam, T., Chapman, D. 2010. Molecular characterization and phylogenetic analysis of Eimeria from turkeys and gamebirds, and the implication on the evolutionary relationships OF Eimeria FROM galliforme birds. Journal of Parasitology. 96:982-986. Interpretive Summary: Understanding the evolution of Eimeria in poultry is extremely important because it provides a perspective on controlling and treating coccidiosis in chickens as well as in other poultry species. In this study we used sequences of two different genes to study the evolution of Eimeria in chickens, domestic turkeys, and two species of game birds (pheasants and chukars). Through this analysis we have determined that Eimeria that infect chickens can be divided into two distinct groups. One group represents the species that infect the ceca (lower intestine), and these are more closely related to Eimeria of turkeys and pheasants. The other group can be categorized as the species that infect the upper regions of the intestines (duodenum, mid-gut). It’s possible that coccidiosis in chickens is a result of two different infection events which occurred earlier in the evolutionary history of the chicken. One of these gave rise to species that infect the ceca and the other gave rise to the species that infect the upper regions of the gut. This is important information, because it underlines the fact that coccidiosis in chickens most likely represents different diseases, each of which has different symptoms and perhaps necessitates different treatments.
Technical Abstract: In order to evaluate the evolutionary relationships of Eimeria that infect galliforme birds, the 18s rDNA gene, and a portion of the cytochrome oxidase subunit 1 (cox-1) were amplified from Eimeria that infect turkeys, chukars, and pheasants. The phylogenetic analysis of these sequences suggests that Eimeria species that infect chickens are polyphyletic, and therefore do not all share a direct common ancestor. Both the 18s rDNA as well as the cox-1 sequences indicate that Eimeria tenella and Eimeria necatrix is more closely related to Eimeria that infects turkeys and pheasants than to other Eimeria species that are infectious to chickens. It is therefore likely that Eimeria that infects chickens represents two separate ancestral infection events. Once of these represent E. tenella and E. necatrix which infect the ceca, while the second infection event has given rise to the species which infect the upper regions of the intestine like Eimeria maxima and Eimeria acervulina.