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Liver Fluke Test: Developing A Rapid Test To Support Farmers In Response To Anthelmintic Resistance
“We are delighted that what started as a research tool is now being developed as a practical diagnostic test for farmers and vets, to support strategic control for this common, devastating disease.” Dr Tessa Walsh, University of Liverpool
Working with the University of Liverpool, GADx (formerly Mologic) developed an innovative liver fluke test that enables farmers to rapidly detect Fasciola hepatica infection in sheep and cattle.
What Is Liver Fluke?
Liver fluke disease in sheep and cattle is caused by the Fasciola hepatica, a common parasitic flatworm that can greatly impact livestock production worldwide. The parasite causes damage to the liver and bile ducts of infected animals, animals may show obvious clinical signs of weight loss, anaemia and death, but more commonly, infection is sub-clinical and leads to significant lost productivity.
The life cycle of the parasite relies on an intermediate snail host and mild wet conditions to thrive. In the UK, these conditions are most prevalent during the summer months and the infectious stages of the parasite are released onto pasture any time between August and December.
The precise timing of this release is difficult to judge as it is dependent on the local summer weather conditions and climate change is making it much less predictable.The life cycle of this parasite is described in below diagram by the FAS:
The Challenges Of Diagnosing Liver Fluke Infection
The disease has been reported in at least 70 countries worldwide and is prevalent across many of the major global livestock rearing areas. However, owing to shifts in weather patterns and global trade, there’s scope for this parasitic infection to become even more prevalent.
In sheep, the disease presents itself in three forms: Acute disease (or high infection level) where extensive liver damage leads to sudden death; in sub-acute where sheep and cattle are repeatedly infected but at a reduced level, lethargy, anemia and weight loss occurs and death may result; and finally chronic liver fluke disease is characterized by severe weight loss and anemia.
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In cattle particularly, the infection manifests as a sub-clinical disease, resulting in direct production losses, which are difficult to estimate. The lack of obvious clinical signs results in these losses commonly being attributed to other causes.
This is problematic for effective treatment and undermines appropriate control strategies available. Additionally, welfare of the animal is compromised by poor or incorrect diagnosis.
Diagnosis of liver fluke infection is complex. A vet may be needed to take samples and it can take up to a week for results to come back from the lab. From a farmer’s point of view, this is problematic, as livestock will have to be gathered for a second time for treatment, which takes time and adds to the cost, plus juvenile liver fluke can kill sheep within days if heavy infections build up. For these reasons, livestock are frequently treated based on calendar dates rather than diagnostic information.
Why Liver Fluke Diagnosis Is Crucial For The Agriculture Sector
Listed as one of the leading diseases in terms of economic impact on livestock production, liver fluke is estimated to affect 600 million farm animals per year, costing the agriculture sector over $3 billion dollars in the form of lost yield (lower growth rates and carcase quality) and additional medical costs.
Additional research points to an average lifetime losses of more than £60 ($73) per animal for farmer. The loss in agricultural yield can be attributed to livestock being infected with liver fluke taking longer to reach slaughter weight.
According to data from Boehringer, at a Scottish abattoir showed that animals with 1 to 10 liver fluke present in their liver took an average 31 days longer to reach slaughter weight. Animals with more than 10 liver fluke present took an additional 77 days longer to reach slaughter weight versus animals without any liver fluke infection.
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To complicate matters, diagnosis of liver fluke infection is difficult, and flukicides are frequently used, adding additional costs to farmers, in the absence of a diagnosis or disease symptoms. Unfortunately, this approach has led to drug-resistant flukes. Emerging resistance to these drugs is a problem for sustainable livestock production.
Therefore, effective diagnosis will not only enable farmers to sustainably achieve agriculture production targets, but also prevent the issue of anthelmintic resistance.
Effective Liver Fluke Diagnosis Is Vital For Global Food Supply
With the global population projected to reach 10 billion by 2050, there is an urgent need to ensure the agricultural sector is able to sustainably meet this surge in demand. The UN Food and Agriculture organization (chart below) estimates suggest demand for animal protein will outstrip human population growth.
Achieving a 76% increase in meat production worldwide by 2050 is vital for the global population, and a cost-effective and simple means of diagnosing liver fluke without laboratory equipment is part of the solution.
Developing An Innovative Pen-Side Liver Fluke Test
Recognising this development, the University of Liverpool sought out GADx’s expertise to develop a suitable rapid diagnostic test. This will enable farmers, in a cost-effective manner, to detect the presence of Liver Fluke infection on-site, and without the need for advanced laboratory equipment.
Recognising this development, the University of Liverpool sought out GADx’s expertise to develop a suitable rapid diagnostic test. This will enable farmers, in a cost-effective manner, to detect the presence of Liver Fluke infection on-site, and without the need for advanced laboratory equipment.
GADX with its strong knowledge of rapid diagnostic technology in the agricultural sector, was able to meet the University of Liverpool’s needs by undergoing the following steps:
1) Carrying out an in-depth market review: to assess the commercial landscape and business opportunity.
2) Developing an industry questionnaire with the University: to more specifically identify industry requirements, such as test specifications, sampling regime and type, on-farm test workflow, a qualitative or quantitative test read out, result interpretation to determine treatment pathway.
3) Merging industry data with production needs: test price point to help drive bill of materials selection (BOMs), cost of goods (COGs) for market uptake, manufacturing requirements depending on order volume.
4) Ascertain regulatory pathway and submission process for different markets.
One of GADx’s core strengths is its capacity to provide clients with a bespoke approach to their test development requirements.
Result: An Innovative Solution By GADx
“We are delighted that what started as a research tool is now being developed as a practical diagnostic test for farmers and vets […] The project has been supported by AHDB and BBSRC to bring it to a point where we can start to develop the test commercially.”
Dr Tessa Walsh, University of Liverpool
In the end GADx was able develop a liver fluke test that detects antibodies circulating in the blood of fluke-infected animals through a blood droplet taken from the ear. Below is a chart explaining how the test is utilised:
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The key strength of this test is its capacity to deliver highly accurate results within 10 minutes on-site, without the need for laboratory equipment. This innovate liver fluke test is a game-changer for the agricultural sector and achieves the following:
1) Early liver fluke infection diagnosis: enabling farmers to rapidly and accurately monitor infection, control its spread, and implement targeted treatment programmes.
2) Meeting sustainable production targets in a cost effective manner: enabling farmers to rear livestock to a suitable slaughter weight efficiently without expensive lab testing equipment and reduce need to use flukicide.
3) Prevent the rise of anthelmintic resistance: which is not only financial burden, but will also enable long-term sustainable agriculture.
4) Enable farmers worldwide to meet global food demand: with animal protein demand forecasted to increase by 76% by 2020, managing liver fluke infection effectively is part of the global solution to this trend.
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