Rumen fluke in cattle and sheep: measuring impacts and improving diagnosis

Helminth (worm) parasites cause around 55% of all farm animal diseases. These parasites impact hugely on livestock productivity by affecting growth rates, fertility, meat quality, wool or milk production, and sometimes cause death. One of the most important parasites to impact animal production in the UK/Ireland (and throughout the EU) is the liver fluke, Fasciola hepatica. It infects more than 300 million cattle and 250 million sheep worldwide resulting in losses of over $3 billion to global agriculture through lost productivity. In the UK it costs the cattle farming industry alone around £23 million each year as a result of poor animal condition and a significant reduction of milk and meat yields. Worryingly, resistance to the frontline chemical treatment for liver fluke (a drug called triclabendazole) has become widespread leaving farmers with little to combat the disease. Until recently, infections by similar parasites called paramphistomes, or rumen fluke, were regarded as being of minor importance. However, over the last few years increasing reports of production losses from farmers in Great Britain and Ireland have been ascribed to infection by rumen fluke. It is now believed that rumen fluke has become a bigger problem than liver fluke in many areas. In order to meet the growing threat to food security posed by rumen fluke infection it is imperative that we act now. In this project we will answer some basic questions about its biology, its impact on animal health and productivity and will develop new tests that will allow more rapid and specific diagnosis than currently possible.

Specifically, we will address three main questions:

1) What is the extent of the rumen fluke problem in the UK?
2) What is the impact of rumen fluke on animal performance, health & welfare?
3) Can we develop a rapid and specific diagnostic test for rumen fluke?

Our approach is timely and will determine the extent of the problem in the UK and for the first time determine a measurable impact of infection on animal production in both cattle and sheep. Furthermore we will have produced rapid and specific diagnostic tests that will allow appropriate control measures to be put in place. These important findings will allow more effective management practices to be put in place early and give us a realistic chance of avoiding the problems of drug resistance currently seen with liver fluke.

The overall objective of the project is to address the emerging threat to animal health, welfare and livestock sustainability posed by rumen fluke in sheep and cattle. Specifically, we will address three main questions:

1) What is the extent of the rumen fluke problem in the UK?
The true extent of the rumen fluke problem in the UK has not yet been investigated. Using data collated from our industry partners we will determine its incidence and geographical range in the UK and use a multiplex PCR on intermediate hosts (snails) to investigate the likelihood of co-infection with liver fluke. We will conduct a UK-wide survey of farmers to gauge their awareness of the problem and set up knowledge transfer events to help them manage the infection more effectively.

2) What is the impact of rumen fluke on animal performance, health & welfare?
Despite considerable anecdotal evidence that diarrhea and production loss are caused by chronic rumen fluke infection it is still unclear to what extent infection impair animal welfare and translate into measurable production losses. We will conduct field studies on four experimental husbandry farms to measure the impact of rumen fluke infection on diarrhoea score, bodyweight and welfare assessment of grazing dairy heifers. Metabolic studies using state-of-the-art calorimetric chambers will also be conducted to determine the impact of rumen fluke on feed intake and digestibility in sheep.

3) Can we develop a rapid and specific diagnostic test for rumen fluke?
Current diagnosis of rumen fluke relies on labour-intensive methods such as examination of animals at post-mortem or faecal egg counts. Using proteomics we will characterize the secretome of rumen fluke and use selected antigens to develop ELISAs for detection of rumen fluke in faecal samples and bulk milk.

This project, aimed at investigating the impacts of rumen fluke in sheep and cattle in the UK and improving its diagnosis will have important societal and economic impacts.

[1] The livestock industry, such as cattle and sheep managers, and veterinarians, will benefit from having access to early warning signs of rumen fluke infection through animal-based (welfare) indicators and the development of tools for rapid and correct diagnosis. At present diagnosis is based on faecal egg counts in living animals making it difficult to distinguish clearly between rumen fluke and liver fluke, and relying on abattoir data for diagnosis is not practical for dairy cattle and breeding ewes nor for rapid response. Increasing scientific knowledge of early signs of the disease and developing tools for its rapid and correct diagnosis will enable effective therapeutic intervention before the onset of pathology. This in turn will enable producers to rear livestock to higher standards of health and welfare and ensure cost-effective control.

Furthermore, to what extent acute and chronic rumen fluke infection translate into measurable production losses or predispose animals to other diseases is unknown. Knowledge gained from this project will help to quantify the true impact on productivity and inform management decisions needed to avoid livestock and economic losses due to rumen fluke infection. It will promote livestock performance by avoiding the failure to thrive associated with chronic rumen fluke infection. Lower levels of infection will reduce pasture contamination and thus reduce the incidence of infection in subsequent years. In addition, selective use of anthelmintics with proven efficacy will improve livestock productivity, prevent the selection of anthelmintic resistant rumen fluke populations and thus maintain our ability to limit the spread and incidence of infection.

The development of tests for the early diagnosis of infections will improve targeting and economic use of therapeutics, thus limiting the unnecessary contamination of pasture with anthelmintic residues which may harm invertebrate eco-systems. By limiting the exposure of livestock to fluke infection this project aims to maximize weight gain and feed use efficiency in stock animals and minimize anthelmintic usage. This will reduce the presence of anthelmintic residues in the export product. Overall this project will enable the livestock industry to rear livestock to higher standards of health and welfare and to achieve economic competitiveness.

[2] Agricultural industry stakeholders such as meat plants, food processors and retailers will benefit in at least two ways. Firstly, this research will help to ensure that improving animal welfare should remain a priority for them, thus guaranteeing higher standards of health and welfare of the animals. A second important benefit is the reduced presence of anthelmintic residues in the export product. Both these benefits have important economic consequences for the food industry, as they can use this when marketing their products.

[3] Policy makers (Governments, EU, NGOs, etc) will benefit from having access to a scientific knowledge base quantifying i) to what extent rumen fluke infections, chronic or pathogenic, affect animal welfare and animal performance and ii) the potential for co-infection with liver fluke. This will enable them to make sound, evidence-based decisions and inform on strategies for improving the conditions and management of farmed animals. Furthermore, this project is in line with the aims of the "One Health" approach taken by policy makers as it will facilitate a more targeted use of therapeutics and the uptake of management practices minimizing anthelmintic usage.

[4] Consumers will benefit from knowing that something is being actively done to improve the health and welfare of farmed animals, and that products from farm to fork are welfare-friendly and free of unnecessary drug residues.