Population, genetic, and antigenic diversity of the apicomplexan Eimeria tenella and their relevance to vaccine development
Damer P. Blake,a,1 Emily L. Clark,a,2 Sarah E. Macdonald,a Venkatachalam Thenmozhi,b Krishnendu Kundu,c Rajat Garg,c Isa D. Jatau,d Simeon Ayoade,e Fumiya Kawahara,f Abdalgader Moftah,g Adam James Reid,h Ayotunde O. Adebambo,e Ramón Álvarez Zapata,i Arni S. R. Srinivasa Rao,j,k Kumarasamy Thangaraj,l Partha S. Banerjee,c G. Dhinakar-Raj,m M. Raman,b and Fiona M. Tomleya
Sixty billion chickens are produced worldwide each year, and all are at risk from Eimeria, parasites that cause coccidiosis. Control relies widely on chemoprophylaxis, but pressure to reduce drug use in farming urges development of cost-effective vaccines. Antigens such as apical membrane antigen 1 (AMA1) offer promise as anticoccidial vaccine candidates, but experience with related apicomplexans such as Plasmodium, in which pre-existing antigenic diversity and incompatible population structure have undermined vaccine development, tempers confidence.
Parasite genotyping identified enormous region-specific variation in haplotype diversity for Eimeria tenella but a contrastingly low level of polymorphism for EtAMA1. Although high levels of polyclonal Eimeria infection and hybridization indicate an ability to disseminate vaccine resistance rapidly, the low level of EtAMA1 diversity promotes vaccine development.