Reducing reliance on ionophores: Eimeria population biology and impact on selection for antimicrobial resistance

More than 280 tonnes of antimicrobial drugs (ionophores, commonly not classified as antibiotics) are used in UK poultry production every year, primarily to control parasites such as Eimeria. The global use of ionophores is unclear, but is likely to exceed 16,000 tonnes per annum.

Public and legislative pressure is calling for reduced ionophore use, but the emergence of three new Eimeria species that can escape current vaccines and reduce economic performance risk prolonged use.

Ionophores can also control bacteria such as Clostridium perfringens and the disease necrotic enteritis, but have been associated with selection for transferable elements that facilitate ionophore resistance in Enterococcus faecalis and Enterococcus faecium, and co-occurrence with genes that confer resistance to erythromycin, tetracycline and ampicillin.

Enterococcus are bacteria that infect chickens but can also cause disease in humans - the spread of antimicrobial resistance genes (ARGs) could undermine animal as well as human health.

Here, we aim to understand Eimeria population biology, including emergence of new types and the consequences of cross-fertilisation (hybridisation), interactions with the host, intestinal populations of bacteria and ionophore or vaccine selection.

In parallel, we will use the same chickens and samples to define the consequences of ionophore use in commercial poultry populations on the occurrence of ARGs that could flow into food chains and the environment.

Combined, this project offers a holistic approach to understand Eimeria population biology and the consequences of ionophore use as essential steps towards reducing reliance on ionophores in chicken production.