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Int J Parasitol. 2016 Aug;46(9):537-44. doi: 10.1016/j.ijpara.2016.05.006. Epub 2016 Jun 29.

Cryptic Eimeria genotypes are common across the southern but not northern hemisphere.

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Department of Pathology and Pathogen Biology, Royal Veterinary College, North Mymms, Hertfordshire, UK.
Department of Veterinary Parasitology, Madras Veterinary College, Tamil Nadu Veterinary and Animal Sciences University, Chennai, India.
Division of Parasitology, Indian Veterinary Research Institute, Izatnagar, Uttar Pradesh, India.
Department of Animal Breeding and Genetics, Federal University of Agriculture, Abeokuta, Ogun State, Nigeria.
Department of Parasitology and Entomology, Faculty of Veterinary Medicine, Ahmadu Bello University, Zaria, Nigeria.
School of Agriculture, Food and Rural Development, Newcastle University, Newcastle upon Tyne, UK.
Universidad Central de Venezuela, Facultad de Agronomía Instituto de Producción Animal, Av. Universidad via El Limón, Maracay, Venezuela.
Accra Veterinary Laboratory, Accra, Ghana.
Department of Poultry Science, University of Arkansas, Fayetteville, AR, USA.
Southern African Centre for Infectious Disease Surveillance, Morogoro, Tanzania.
Department of Biotechnical and Diagnostic sciences College of Veterinary Medicine, Animal resources and Biosecurity, Makerere University, Kampala, Uganda.
Department of Paraclinical Studies, University of Zambia, Faculty of Veterinary Medicine, Lusaka, Zambia.
Production and Population Health, Royal Veterinary College, North Mymms, Hertfordshire, UK.
National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing, China.
CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India.
Augusta University, Augusta, GA, USA.
Department of Animal Biotechnology, Madras Veterinary College, Tamil Nadu Veterinary and Animal Sciences University, Chennai, India.
Department of Pathology and Pathogen Biology, Royal Veterinary College, North Mymms, Hertfordshire, UK. Electronic address:


The phylum Apicomplexa includes parasites of medical, zoonotic and veterinary significance. Understanding the global distribution and genetic diversity of these protozoa is of fundamental importance for efficient, robust and long-lasting methods of control. Eimeria spp. cause intestinal coccidiosis in all major livestock animals and are the most important parasites of domestic chickens in terms of both economic impact and animal welfare. Despite having significant negative impacts on the efficiency of food production, many fundamental questions relating to the global distribution and genetic variation of Eimeria spp. remain largely unanswered. Here, we provide the broadest map yet of Eimeria occurrence for domestic chickens, confirming that all the known species (Eimeria acervulina, Eimeria brunetti, Eimeria maxima, Eimeria mitis, Eimeria necatrix, Eimeria praecox, Eimeria tenella) are present in all six continents where chickens are found (including 21 countries). Analysis of 248 internal transcribed spacer sequences derived from 17 countries provided evidence of possible allopatric diversity for species such as E. tenella (FST values ⩽0.34) but not E. acervulina and E. mitis, and highlighted a trend towards widespread genetic variance. We found that three genetic variants described previously only in Australia and southern Africa (operational taxonomic units x, y and z) have a wide distribution across the southern, but not the northern hemisphere. While the drivers for such a polarised distribution of these operational taxonomic unit genotypes remains unclear, the occurrence of genetically variant Eimeria may pose a risk to food security and animal welfare in Europe and North America should these parasites spread to the northern hemisphere.


Chicken; Eimeria; Genetic diversity; Operational taxonomic units; Vaccine

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