€5m vaccine project to target liver fluke parasite

Liver fluke affects 75pc of dairy cattle and farmers spend an estimated €90m treating parasitic diseases

Summer trials: Professor John Dalton is optimistic that if the vaccine works on sheep, it will work on or even be better on cattle.
Summer trials: Professor John Dalton is optimistic that if the vaccine works on sheep, it will work on or even be better on cattle.
Professor John Dalton
Ciaran Moran

Ciaran Moran

A ground­breaking research trial this summer is set to test a vaccine that might prevent liver fluke.

Professor John Pius Dalton, a renowned scientist in infectious diseases, has joined NUI Galway as Professor of Molecular Parasitology to tackle major parasitic diseases of humans and their livestock.

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He is developing a €5m research project, which will devise an overall strategy for the development of a novel preventative vaccine of parasitic diseases for both humans and animals.

Irish farmers spend more than €90m per year to protect their sheep, cattle and pigs from such diseases.

The emergence of drug-resistance parasites, as well as the impacts of climate change on parasite transmission, is causing major concern as we are now seeing an increase of livestock parasites in Ireland and across Europe.

Professor Dalton's research will also develop novel diagnostic tests for parasites to help farmers control and manage infection on the farm to reduce their reliance on chemical treatments.

"The ultimate aim is to benefit farmers," says Professor Dalton, "they need better means of detecting diseases on farms so that they can strategically, rather than randomly, treat their livestock. It saves them money, effort and, in the long term, can help eradicate the disease."

Liver fluke

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Liver fluke will be the main emphasis in the project, he explains while also highlighting the scale of the issue in Ireland. "Liver fluke is a huge issue in Irish agriculture with research suggesting it affects 75pc of our dairy cattle," he says.

Currently, liver fluke is controlled by chemicals with the obvious issue of withdrawal periods and resistance.

He said there is now widespread resistance to the drugs launched in the 1980s to control the early stages of infection.

"The reason why these drugs were so popular is because they killed the very early stages of the parasite and thus protected the animal from liver damage.

"The drug was used so intensively it was a no-brainer that resistance would emerge," he says, highlighting that the first signs of resistance occurred as far back as the 1990s.

"Drug resistance has left farmers with no means of control of the early infection. They can't protect their animals. We see resistance in Ireland, right across Europe and as far as Australia."


Professor Dalton explains that the project is about understanding the parasite. "I have been studying this for 30 years. However, the significant change over the last five years is genomics. We now can study the parasite in a more molecular level."

He highlighted that previous work concentrated on the late stages of infection.

"It's straightforward to pick up the infection when it's at the late stage, but the damage is already done to the liver of the animal," he says.

The new technology, he says, allows scientists to study the infection at a very early stage when the animals pick up the infection from the grass and the parasite is microscopic.

"When the parasite comes into the digestive tract, the parasite is in a dormant stage because it has been sitting on the grass for months.

"The parasite penetrates the intestine of the animal and crosses into the liver and causes extensive damage," he says.

This stage, when the parasite penetrates the intestine and crosses into the liver, is where the professor has been studying for the last five years.

"This stage is where we want to develop our vaccine, stopping the parasite before it has a chance to damage the liver.

"It's a huge challenge because the parasite itself is microscopic, however with genomics we can now trace the development of the parasite.

"Liver fluke goes from being microscopic to about two centimetres long and over a centimetre wide in the space of two months. That is massive growth and demonstrates the resilience and adaptability of the parasite," he says.

The research team are examining which molecules the parasite is using to penetrate the intestine and which ones it uses to suppress the immune system of the animal, shortlisting these molecules as vaccine candidates.


The research team is planning to test the first vaccine on farm in collaboration with Teagasc Athenry this summer. "We are going to vaccinate young lambs by means of a simple injection and place them on an infected pasture. They will also get a follow-up vaccination while they are on the paddock."

He explains that there would also be a control group of lambs which will not be vaccinated. In the autumn, the team will assess the lambs to see if the vaccine immunised the lambs against fluke.

"We are going to concentrate on sheep first, but we intend to develop a vaccine for both sheep and cattle," he says.

"We are optimistic that if the vaccine works in sheep, it will work on or even be better on cattle," he says.

He stressed that the team's main goal is developing the vaccine for the benefit of farmers.

"We know what farmers want - they want an animal that is healthy and puts on more weight.

"There is no point in us developing a vaccine that only works in the lab and is not transferable to the field."

Prof Dalton highlights that at one point farmers were recommended to use drug treatments once a month.

"That was an enormous expenditure and an enormous use of chemicals in the food chain.

"With a vaccine, there will be no withdrawal period and no chemicals involved. Vaccines are greener," he says.


'We now have the tools to ­understand link between host and parasite'

Liver fluke also poses a threat to human health.

While infections with parasitic worms, such as pinworm, may have been common in Ireland over 70 years ago, due to better sanitation and control measures these are, thankfully, now infrequent.

However, globally, almost two billion people, one-quarter of the world's population, suffer from parasitic worm diseases.

These occur predominantly in poorer regions of the world, such as sub-Saharan Africa, Asia and South America, where households earn less than two dollars a day.

"In many parts of rural Asia, Africa and South America where people manage their livestock much differently to here, animals are left roam around and contaminate the vegetation that people eat. Humans can pick up the parasite on food just like animals," says Professor John Dalton from NUIG.

"Parasitic diseases cause high morbidity, particularly amongst children, and reduce the economic potential of these regions, and compound the health and well-being issues related to poverty.

"To develop new vaccines, we need to understand the basic biology of the interaction between the parasite and its host - from this we can devise vaccines to break this relationship and protect the host, and we now have the molecular, bioinformatics and genetic tools to do this, as well as the technology to manufacture vaccines.

"I'm looking forward to developing a world-class molecular parasitology research team at NUI Galway and to tapping into the excellent expertise in infectious diseases already established here and nearby at Teagasc, Athenry.

"This is a perfect research environment to translate our research into real and practical outcomes in veterinary and human medicine, not only for Ireland but also for much less well-off regions in the world," Prof Dalton adds.

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