It’s my life: Martin Nielsen, the accidental parasitologist

Martin Nielsen's interest in equine parasites was piqued at veterinary school in Denmark. He is now one of the best-known researchers in the field.
Martin Nielsen’s interest in equine parasites was piqued at veterinary school in Denmark. He is now one of the best-known researchers in the field.

It’s hard to believe that one of the world’s best-known equine parasitologists could easily have specialized in something else. Fate and circumstance played no small part in the career direction of Martin Krarup Nielsen. Neil Clarkson reports. 

If the field of equine parasitology had rock stars, Martin Nielsen would be its Jon Bon Jovi.

Rock stars need more than just musical talent. They need a strong stage presence, good hair, and, perhaps most importantly, a unique voice.

Nielsen is the man with that voice.

He has authored or co-authored about 90 scientific papers published in peer-reviewed journals. He has co-authored a handbook on parasites and written numerous articles for magazines. He is co-editor in chief of a well-respected journal, Veterinary Parasitology.

All of that came after training to be a vet and working in clinical practice for three years.

That speaks of the Danish-born scientist’s talent. But Nielsen also has the stage presence. He is warm, engaging and quick-witted. He likes to tell a story. He is 45 but looks implausibly young for someone who has been with the prestigious Maxwell H. Gluck Equine Research Center at the University of Kentucky for seven years, the first five as an assistant professor before being appointed an associate professor with tenure.

Before Kentucky beckoned, he was an assistant professor for four years at the University of Copenhagen.

Through all this, Nielsen somehow manages to make a head of greying hair look cool.

Equine parasitology needs its rock stars. The field is something of an anomaly. It is a specialist area of research, not exactly sexy science, but one in which many horse owners take an active interest. They hate the thought of little critters potentially harming their horses. They want control, but many worry about the potential overuse of chemicals.

Indeed, overuse has been one of the key drivers of worsening parasite resistance, and a consuming area of research in the field.

There have been towering figures in equine parasitology, such as Gene Lyons and Harold Drudge. Their discoveries have had an important influence on how owners have managed horse parasites for decades.

Nielsen is the modern face of parasitology.

Yes, he does the hard yards in the lab. But you will also find him on Twitter. And then there is his YouTube channel, Martin K. Nielsen Equine Parasitology, where you will find him talking about worms. He has successfully crowdfunded two studies, raising $US20,000 for one and $US70,000 for another. The first, a pilot study, led to a five-year federal grant for more research.

There are seminars, webinars, online and phone-in question sessions, round-table discussions, veterinary conferences, and talks to horse owners. Nielsen is a walking and talking one-man outreach program.

Martin has had a life-long involvement with horses, in particular the Icelandic breed.
Martin Nielsen has had a life-long involvement with horses, in particular the Icelandic breed.

He says his research is about the well-being horses and making a difference for those who take care of them. Much of his research is applied science.

So, when you learn that smartphone technology has been developed to conduct egg counts, it’s not especially surprising to learn that Nielsen is involved.

His fingerprints can be found on some of the most important research in the field in recent years.

He completely understands the desire of horse owners to find natural wormers. Indeed, he has carried out some well publicized research in the field.

Nielsen has talked on the topic before, seemingly able to engage with those opposed to the use of chemicals who are adamant they can get results with natural dewormers.

He is firm, but diplomatic on the point. We’re simply not there yet, although some progress is being made, citing the planned release of a fungus-based product which had been studied as far back as the 1990s.

But, for now, today’s anthelmintic drug classes, some of which have been available since the 1960s, remain the best we’ve got.

Nielsen’s veterinary background is unusual, and he admits as much.

He stepped into veterinary school in Copenhagen in the mid-1990s and quickly discovered he was different from many of the other students.

“Many of those at veterinary school were fulfilling a lifelong dream to become a veterinarian, or were following in the footsteps of their parents,” he recalls.

Not so Nielsen. For him, it seemed like a sensible career choice for someone who had spent a life involved in horses.

His mother had grown up with a passion for horses and her husband-to-be promised her a horse when they married. Several years later, the horse had yet to materialize.

The family moved house and neighbors on both sides had Icelandic horses. The pressure was on.

In 1979, Nielsen’s father, a landscape architect, went out and bought an Icelandic horse, who took up residence in their generous backyard. Martin was 6.

“My sisters and I started taking riding lessons. We got that one horse and it quickly turned into three horses.

“My parents bred a mare and got their first foal and started a little stud farm. My mum started giving riding lessons and then established a whole riding school.”

Not surprisingly, the family moved quite quickly to a small farm to cater for the horses.

“For the most part I grew up in the country.

“We never really went for any holidays growing up because we had the horses.

“But we went to horse shows.”

The family bought a horse trailer that could take five horses. They would all sit in the front and drive to weekend competitions.

“We would empty out the horses, clean up, and then we would put down mattresses and sleep in it. That would be our family trips.”

Martin Nielsen grew up with Icelandic horses and they remain his passion. Among other things, he is part of the Knights of Iceland Show Team, which promotes the breed in North America. Here the team is performing in the Kentucky Horse Park. Nielsen is second from right. His wife, Shaila Sigsgaard is second from left. Photo: Ida Sigsgaard
Martin Nielsen grew up with Icelandic horses and they remain his passion. Among other things, he is part of the Knights of Iceland Show Team, which promotes the breed in North America. Here, the team is performing in the Kentucky Horse Park. Nielsen is second from right. His wife, Shaila Sigsgaard is second from left. Photo: Ida Sigsgaard

His father came along and also rode and competed, before rising to become an international judge for Icelandic horses, as well as organizing events.

Horses were a big part of Nielsen’s life, but he struggled to find a career path.

“I found it really, really difficult to decide what I wanted to do with my life. After high school I felt a little fed up with going to school, so I went to Iceland for a year and trained horses.

“And that went fine.

“Some of my friends who were about the same age and were involved in Icelandic horses at the time actually chose that as a career, to become an Icelandic horse trainer.

“If you wanted to do that you had to go and spend time in Iceland, work with some of the good trainers.

“That was the path I was on.

“And I worked for a farrier and he taught me horse shoeing, so I started shoeing horses.”

He returned to Denmark after a year, where he continued to train and shoe horses.

Then, he started thinking about further education.

“I went and did some night school just to kind of get back into studying. Then I made a long list of career options and started crossing things out.

“I thought of something in biology; something involving animals. In the end, being a veterinarian didn’t seem like such a bad option.”

Nielsen found he had limited enthusiasm for memorizing the contents of entire textbooks, or learning the names of anatomical structures. “I didn’t find that very stimulating,” he admits.

“The parts that I enjoyed were where you got the chance to go into depth in certain topics. I really loved that, but a lot of my vet school friends really hated it. In fact, they hated that the most.”

Many also hated writing reports, which Nielsen enjoyed.

“Even before I graduated, I was approached by some professors who just wanted to make me aware of PhD opportunities. I don’t think I knew what a PhD was when I started vet school.

“Then I talked to Shaila, my wife, and she was like, ‘Yeah, you don’t want to be a nerd. You should at least try life as a vet out in the real world.’

“And I thought she had a point. After all, veterinary practice was sort of what I had in mind when I started.”

Nielsen decided to try working as a vet for a few years after graduating in 2001. He found a job in which most of the work was equine.

“It was a typical vet job. Lots of visits. No two days would be the same. The nice countryside of northern Denmark. Great people. It was nice.

“In the beginning, you struggle to keep up with everything as a new graduate, but then you start developing a routine which is very fulfilling, and start thinking, ‘right, I’ve got this’.”

The Knights of Iceland perform. Martin Nielsen is at right, his wife, Shaila Sigsgaard, rides beside him. Photo: Ida Sigsgaard
The Knights of Iceland perform. Martin Nielsen is at right; his wife, Shaila Sigsgaard, rides beside him. Photo: Ida Sigsgaard

By the end of the second year, Nielsen started looking for something more.

“I talked to my vet school friends who had all graduated with me. And we all ran into a crossroads, where we had to decide what we wanted to do next. If you stay in practice, a natural next step is to become a partner; actually own a share of the practice and influence it. Or you would want to perhaps develop an area of specialization.

“Many of my friends have done that, but for me it was more like, ‘I could probably keep doing this, but I miss going into depth in things.

“I realized the whole PhD thing would probably work out for me.”

He reached out to some professors at the Danish veterinary school and successfully applied for a stipend.

He returned to university in 2004, graduating with his PhD in 2007. He got a job as assistant professor at the Danish vet school that year, then moved to Kentucky in 2011.

So, how did come to Nielsen come to specialize in equine parasitology?

“My wife has said this many times,” he begins. “It could have been anything. Any topic. And I think she is right.

“It became parasites because, during my years in vet school in the 1990s, the Danish parasitology group was huge. It had a lot of funding; there was a lot of activity going on.

“At one point during those years they had 30 PhD students engaged at the same time, all working on parasitology projects.

“And, as a vet student, there were so many opportunities to get a job – a paying job – helping out with some of these projects and learning something that would be beneficial. It was a win-win.

“I was part of that, as many others were.

“It was so exiting to hear about the different projects and what they were about. I found it very appealing and interesting.”

But the key figure in the story was Peter Nansen, then professor of parasitology at the Copenhagen vet school. He was a towering and charismatic figure with an uncanny knack for remembering the names of students – no minor feat given that there were 125 in each of his classes.

“It makes a difference when a professor knows you. Sometimes he would see some of us in the hallway, and come over, and have suggestions on projects and activities we could get involved with.

“A couple of times, he called me on my landline in my little studio apartment because he had a project he thought I might be interested in. That was very encouraging, so I give him a lot of credit for steering me in the direction of parasitology.

Sadly, Nansen died before Nielsen graduated.

“He was obviously excellent at getting funding. In the 1990s, if you had ambition and wanted to do something in parasitology, you had to go to Copenhagen.

“Many of the big names had spent time with Nansen, who had a tremendous impact on the field. He was a star.”

Parasitology researchers Dr Martin Nielsen with Dr Gene Lyons.
Martin Nielsen with the legendary Dr Gene Lyons, who died late last year.

So, how far have we come in parasite control since Nielsen walked the corridors of his veterinary school 20 years ago?

Some of themes from the 1990s remain themes today, he says.

“One of the big projects back then was the fungal spores that you feed to the animals, and passes through the intestines and kills the worms out in the field.

“Now, 25 years later, there is a product coming out being launched by an Australian company, but it has taken this long for a commercial product to see the light of day.

“But what has changed since then is that we have way more antiparasitic resistance now than we did back then. It was already recognized back then, but it has become so much worse.

“You could say that we have failed at preventing that, because the parasitologists at the time already saw this. They saw the resistance issues. They warned against it.

“They made recommendations and proposed going more surveillance-based, and it didn’t really happen.”

However, there is much more recognition of the problem today, he says, in part aided by the well-publicized knowledge of antibiotic resistance.

The big plus has been huge advancements on the diagnostic side, he says. Molecular-based testing and DNA sequencing was in its infancy when Nielsen was at vet school. It is now better and far more affordable, which has opened new avenues for research.

“There are a lot of basic mechanisms that we need to understand about the biology of parasites, and the mechanisms of drug resistance,” he explains.

“It’s a long journey to get there. A lot of genes, we don’t know what they are or what they do.

“What we have also realized since the 1990s is that resistance is so much more complicated than anyone had ever dreamt of. It is very, very complex.”

Molecular-based technologies now provide a precious opportunity to explore that avenue.

Martin Nielsen is the modern face of parasitology. Photo: File
Martin Nielsen is the modern face of parasitology. Photo: File

Nielsen admits that the drive to move horse owners from strictly calendar-based deworming to a surveillance-based program has had limited success.

“It’s very interesting. In the last half year we have published a couple of questionnaire surveys that have some interesting data on this.”

Nielsen was fortunate to have some input into the government-backed National Animal Health Monitoring System (NAMS) survey in 2015. Each year it focuses on a different farm species in the US, with horses featuring every 6 to 7 years.

Nielsen noted that questions on horses in the 1998 survey had delved into deworming strategies, and he proposed the issue be revisited in 2015.

The findings were revealing.

Between the late 1990s and 2015, the number of dewormer treatments per horse each year had fallen.

“On average, the treatment intensity had gone down, but the use of fecal egg counts as a surveillance tool had not changed a bit.

“At first, it was kind of disappointing for someone like me that all the recommendations, all the work I try to do – the webinars, the seminars, answering questions on the phone – all that doesn’t seem to have helped.

“Then I started thinking about it a little bit more and I thought, ‘why would people decrease their use of dewormers if it hadn’t been for the recommendations we have been making?’

“So they must have heard the message, that it is not necessary to deworm as much as they have done.

“That led me to think, ‘so why this reluctance about using these egg counts?’. If you think about it, it’s probably as simple as this: If you cut down on treatments you save money, and you realize your horses are just healthy, you have saved money, and saved some effort.

“But adding the egg counts, that goes in the entirely opposite direction. It’s extra effort, it’s cumbersome, and it costs more money.”

And the results can sometimes be confusing.

“I think it comes down to, first of all, cost. It’s easy enough to cut some treatments and realize that your animals are going to be fine … but those egg counts, those are going to be an extra cost.”

Nielsen says the most important thing with a fecal egg count is to actually check whether the treatment worked. If all is well, an egg count performed two weeks after treatment should show no parasite eggs. If it does, owners need to start investigating why. Drug resistance? An out-of-date wormer? An inadequate dose?

“A pragmatic approach is to just run the post-treatment counts. That, at least, will tell you something as there shouldn’t be any eggs present. If eggs are found, you know you need to revisit your procedures.”

Nielsen stresses that while the push has been toward surveillance-based worming strategies, there is still some seasonality – for example, drenching against tapeworms in autumn.

“For younger horses, it is more driven by the age of the animals. It is very predictable what parasites a foal will have at various ages, regardless of the treatments they have received.”

Strategic worming can reduce infection pressure among these young animals, he says.

Nielsen’s enthusiasm for his subject is as infectious as the parasites he studies.

There is so much we don’t know, he says.

Nielsen, currently in New Zealand for six months working on a research project, provides a couple of local examples: Rotational grazing with sheep has been shown to reduce presence of strongyle parasites in horses, but there is no data on ascarid parasites, which are so important in foals.

And irrigation is widely used in some areas of New Zealand. How does that affect transmission when there are no dry spells to reduce parasite infection pressure?

Horse owners can follow his work on Twitter.  “I try to keep a somewhat active Twitter profile because I think if you want to talk about science you need to meet the people where the people are. And people are on social media these days.”

In Kentucky, Nielsen has oversight of the university’s now famous parasitology herd, set up by Gene Lyons and Harold Drudge.

“One of them has been kept without deworming since 1979. They have all the parasites you can dream of.”

The horses are remarkably healthy. “In the seven years I have been working in Kentucky I think we have had 1 or 2 colics in a herd of 20 horses. I don’t think that’s higher than for any regularly dewormed herd.

“The bloodworm prevalence is 100%. The foals  get a lot of ascarids. Some of the foals born late in the year struggle a little bit with body condition that first winter. You have to really watch them. Whereas the early foals do fine. I think the parasites might be playing a role there. But other than that, these horses all look great with shiny haircoats and good body condition.”

The other herd comprises miniature horses. Established in 1974, they are religiously treated six times a year with commercial products at labelled doses. Over the years the treatments have altered as new drug classes emerged.

They have double resistance among the small strongyles they carry – that is, they are resistant to two of three available drug classes.

The miniature horses are currently involved in a trial of combination dewormers. Products containing two or more active ingredients targeting the same parasites are commercially available in Australia, New Zealand and South America, but many veterinarians in other parts of the world are using combinations on an extra-label basis because of all the resistance.

“But there is very little research behind this. Does combination deworming actually work? Is it good? Does it make things worse?”

Initial testing of one combination of oxibendazole and pyrantel pamoate showed promise, but then the results tanked, and effectiveness quickly went to a very low level.

“It doesn’t mean that all combinations are bad, or that this combination would not work well in another scenario.

“We are doing a second study now with another combination, this time we are using oxibendazole  with a macrocyclic lactone, so there should be a much higher efficacy. We will see how that works out.”

For now, Nielsen’s research continues one methodical step at a time, while guiding his students.

“I tend to try to address the questions that are right in front me at the time. But when you address one question, there is always a second and a third question. This is why science is so fascinating. The search for information never ends, and the challenges are right in front of us all the time.”

And the exuberant Nielsen is always looking for effective ways to get his message out to horse owners and head off misinformation.

“Vets, parasitologists, haven’t really accomplished that. I don’t think I have the recipe yet either, but I like to try different venues … and maybe get the help of other people to get my message out. Communicating effectively about science is at least as important as carrying out the research.”


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