Defining the genetic diversity of free living and intra-molluscan stages of Fasciola hepatica

Programme of work
Fasciola hepatica, a liver fluke, is an important cause of morbidity and mortality in ruminants worldwide. Effects of sub-clinical infection on growth rates in meat producing animals and milk yield in dairy cattle is estimated to cost the industry around £300million/yr. Fluke has an indirect life cycle involving a mud snail, Galba truncatula, which is found throughout the UK. Currently control of fasciolosis is based on drug prophylaxis particularly the drug triclabendazole (TCBZ), which is effective against both immature and adult fluke, but resistance to TCBZ is emerging throughout the UK.

We have shown that there is high diversity within fluke populations infecting sheep and cattle. This raises questions about how genes, including drug resistance genes, move through the different life cycle stages, on pasture, in the snail and in the definitive host. Here we aim to address key questions in F. hepatica biology:

1. How does prevalence of infection in snail populations and parasite survival, impact on genetic diversity? We will determine seasonal and inter-annual variation in the presence and distribution of snails and metaceracariae on pasture and metacercarial survival in fodder crops using PCR.
2. Do infected G. truncatula produce cercariae of more than one genotype? We will apply our microsatellite markers to type parasite DNA from a) wild caught infected snails (from Q1) and b) snails experimentally infected with a mixture of miracidia of known genotypes.
3. How genetically diverse are metacercariae on pasture? Metacercariae (from Q1) will be whole genome amplified in triplicate and sequenced to 30x coverage on the HiSeq4000 platform and aligned to our reference genome to provide a genome wide panel of markers (SNPs).

This project will highlight the contribution different fluke life cycle stages make to parasite diversity and provide a deeper understanding of how drug resistance emerges and spreads. This will feed into advice to farmers on how best to manage their stock to reduce the amplification of resistance within fluke populations present on their farms. The project will provide immediate advice on risk to livestock from feeding stored fodder and on distribution of infective metacercariae on pasture, enabling the design of evidence based control programmes.

The project meets strategic remit of the BBSRC
BBSRC's Strategic Priorities include 'Agriculture and food security' and specifically: improving the UK's capacity to produce sufficient affordable nutritious safe food. This project falls clearly within that remit because the aim of the project is to increase meat and milk production sustainably by providing evidence based advice on parasite control in sheep and cattle. Better control, reduced reliance on anthelmintics and evidence based advice on control of fluke infection, will improve animal welfare, feed utilisation and nutrition of sheep and cattle, making meat and milk production more efficient, sustainable and cost-effective. This will contribute to national GDP by reducing the need to import meat and milk and extending the livestock products export market, even in the current price climate. The proposal addresses several topic priorities within this broad Priority area such as: animal health, welfare of managed animals, and sustainably enhancing agricultural production. The student will gain experience in working with farmers and industry directly, demonstrating the high impact of this research, also a target for BBSRC.

The project will add value to the student's training
This project is truly interdisciplinary and integrates parasite biology, drug resistance, molecular ecology and population genomics; all key areas of current research funding. The student will benefit from expertise within the Veterinary Parasitology research group and become equipped with an extended next generation sequencing technologies and a bioinformatics skillset directly relevant to any field o