Epidemiologist: “Collaboration is critical in tackling zoonotic diseases”

Avian influenza is reported in the media almost daily. According to experts, the H5 variant of the influenza virus does not pose a significant danger to humans. But the risk of contracting a type of influenza that is dangerous to humans is not zero. This theme is in line with plans that the Ministries of Health, Welfare, Sports, Agriculture, Nature and Food Quality will present next summer in response to the “Zoönoses in the visor” report.


The next epidemic is likely to enter the Netherlands again via Schiphol

Jerdian van Shayk, epidemiologist at GD

Talks are held with the parties concerned. New measures are certainly being taken about raising livestock to reduce the risk of zoonoses, says Jerdian van Schaik, an epidemiologist at GD. “What will come is still uncertain to me.”

Is it all about risk management?

There is no such thing as zero risk of animal-to-human transmission. In the Netherlands we benefit from a good veterinary infrastructure and a high health situation. We are a small country and GD is the focal point where questions about the health of farm animals and horses come together. There is a lot of knowledge and experience here and we are on top. For example, we quickly discovered that the coronavirus was spreading among minks. The government immediately picked up our signal and took action.

Sharing information and informing each other when there are potential outbreaks of zoonoses is going smoothly. better than fifteen years after reports of miscarriage storms in goats caused by Q fever bacteria.

Is risk management in the Netherlands sound?

A great deal of knowledge is available from the veterinary side about diseases and the spread of infection, including in the field of zoonoses. Animal sectors always work on that. Several programs have been established to treat zoonotic diseases such as salmonella, campylobacter, leptospirosis and bovine tuberculosis.

After an outbreak of Q fever, dairy sheep and goat breeders must annually vaccinate their animals against Q fever bacteria. As a country with a lot of people and animals in a small area, we are obligated to put these things in order. We cannot rest on our laurels.

Was a certain success achieved?

The Netherlands became free of bovine tuberculosis in the last century. And the more recent example is that the Netherlands is the only country in the European Union and I think also in the rest of the world that has a leptospirosis-free case in dairy cows. This infection, caused by the bacterium Leptospira hardjo, can lead to milk fever in humans. Our free leptospirose was achieved by a combined approach and we monitor this free state by monitoring tank milk.

Do you worry about bird flu?

Of course, because new infections are still being added and the epidemic has not yet been stopped. A drama for the concerned farmers and their poultry. I hope the bird flu virus will die soon in Gelderse Vallei, which is rich in poultry. There is already a lot of discussion here about animal numbers and the density of livestock farms.

Countries around us are finding it much more difficult to contain the spread of the bird flu virus. In France, many cases of bird flu have been reported, although the size of the farm is smaller and poultry farms are more widely spaced.

What do you think this means?

As an epidemiologist, I look at facts and figures. You have a greater transition between farms if you have a hundred farms with a thousand animals compared to ten farms with ten thousand animals. The risk of zoonoses also decreases in the second case, because fewer people come into direct contact with productive animals. The impact on each company is greater if the infection enters a large company.

The more viruses spread, the higher the chance of mutations that could make them dangerous to humans. This is why it is so important for professional companies to have good biosecurity and to have animals vaccinated if there is a distinct vaccine for them.

Is the maximum size of animal numbers per company desirable?

If a culling is to be carried out due to a zoonotic virus infection, it is important that it be done within a reasonable time, so that further spread is prevented. From the point of view of disinfection capacity, a limit can be placed on the number of animals per site.

Is there a white spot of animal origin?

Swine flu can become a zoonotic problem. This is why we are working on some form of influenza surveillance in pig farms, so we better know what strains of influenza are and which are not kept in pigs. This is now not clear enough.

Will there be mandatory influenza vaccination for pig and poultry farmers?

This is a question for the government, which is the only body that can enforce the vaccination obligation. It is important to be clear what the purpose of the annual flu shot is. Preventing disease or limiting its transmission between animals, between humans or between animals and humans. This must be taken into account in the decision-making process.

Are livestock breeders of animal origin literate?

Livestock keepers care about the health of their animals on a daily basis and are more knowledgeable about the topic than the general public. They are the ones who pick up the first signs of an infectious disease in their animals when something goes wrong. If they get to a vet quickly and the vet can consult a GD if they suspect they have animal disease, the train can start to run fast. Working together with confidence increases the chance of budding infection.

Most zoonotic diseases originate in (sub)tropical regions and come this way with humans. The next epidemic will likely enter the Netherlands again via Schiphol. So we also have to be alert on the human side.

Who is Jerdian Van Shayk?

Jerdian van Schaik, 51, is GD’s chief epidemiologist. Between 2004 and July 2021, she was the Head of Epidemiology at GD. She has also been Professor of Farm Animal Health Monitoring and Monitoring at the University of Utrecht since 2015. This chair promotes collaboration between GD and the University of Utrecht in the field of disease control in farm animals and links practical knowledge and direct access to field data with the latest scientific knowledge. Van Schaik studied animal sciences at Wageningen University & Research and received his Ph.D. there in animal health economics. Van Shayk contributed as an expert to the development of the “Zoönoses in the Crosshairs” report published in June 2021. An expert panel on zoonoses was established in 2020 by the Ministers of Health, Welfare, Sports, Agriculture, Nature and Food Quality to advise on (measures against) the origin of animal diseases Origin, spread and severity.

Wilma and Geert van Beek of Van Beek SPF Pigs in Lelystad.
Wilma and Geert van Beek of Van Beek SPF Pigs in Lelystad. © Kastermans . studio

The influenza virus is still elusive and will remain elusive

I’m familiar with the Zoonoses Looming report. I am a critic of recommendations for influenza surveillance in the swine sector and vaccination of pig farmers and their staff, says Gert van Beek, SPF pig breeder with Topigs Norsvin genetics.

Just this morning I was talking to our employees about corona and vaccination against this condition. Coincidentally, influenza was also discussed at the time, says Van Beek.

We’ve kept certain diseases out of pig houses for over twenty years. But the influenza virus is still a long way off. Even in this pig-free area and under strict biosecurity on my primary breeding farm, they sometimes grow on my animals. The virus is transmitted to the stable with the air or enters through humans. We often don’t notice pigs and find out about it by chance. That could happen if we also had to obtain blood samples for export breeding pigs that had been specifically tested for influenza.

Correct proportions

Pig farmers say pig farming takes zoonoses seriously. But it must remain in the correct proportions. The potential for the influenza virus to pass from pigs to humans and cause significant problems is marginal. If influenza is detected on pig farms in a cost-effective manner and government and society are reassured, it can add up to something for us as a sector.

“The vaccination is effective and I personally wouldn’t have a problem with it if the benefit is really obvious,” Van Beek says of getting the annual flu shot.

Janet van de Ven, Goat Farmer and LTO Portfolio Owner, Healthy Animals
Janet van de Ven, goat farmer and LTO purse owner, Healthy Animals © Eljee Bergwerff

Q fever in humans leads to the One Health approach

Outbreaks of Q fever in humans have been a harrowing experience, according to goat farmer and holder of the LTO Portfolio of Healthy Animals, Janet van de Ven. “This challenging lesson led to a better association between human health and veterinary health, the idea of ​​One Health.”

An outbreak of Q fever in goats that began in 2007 has infected humans. This was not immediately recognized, because good collaboration between human and veterinary healthcare was still lacking. Since this collaboration was already underway thereafter, and signals about potential zoonoses were well captured, it was noted in time that corona was a problem with minks.

Q fever, caused by the bacterium Coxiella burnetii, has not occurred in dairy goats and sheep for years. This can be achieved by a number of measures. Milk tank research is used to continuously monitor whether a company is free of bacteria. In addition, there is an obligation to report in the event of a miscarriage. Then the company is checked.

hygiene protocol

During pregnancy, it is forbidden to visit goat and sheep farms. Postpartum removal is carried out through a special hygiene protocol. Manure should be stored covered for thirty days before it is allowed to leave the company. There is also a mandatory vaccination protocol. All animals are vaccinated each year on farms with more than fifty goats or sheep and also in locations with fewer animals where visitors come, such as a petting zoo.

Van de Veen: “The Netherlands is the only country where we vaccinate every year. It would be good to check if there should be an upper limit on the number of vaccinations an animal should have. Goats are reacting increasingly violently to the fifth or sixth vaccination. The question is whether It adds nothing in terms of protection.

Jacco Wisserhof, Poultry Farmer and Chairman of the Board of Owners of Round Layer Chickens from LTO/NOP
Jacco Wisserhof, poultry farmer and Chairman of Circle Laying Hen Farmers of LTO / NOP © LTO / NOP

Vaccination is the only solution against bird flu

Poultry vaccination is the only solution to combat bird flu. This prevents poultry from getting infected and prevents its potential spread to humans. Although that risk appears small, says LTO/NOP Poultry Farmer and Chairman of the Board of Directors of LTO/NOP Round Hen Bearing Jacco Wisserhof.

Avian influenza is spreading for the second time this year in the Netherlands and many other European countries, but also in Asia and North America. The virus is widespread among wild birds, putting poultry farms at constant risk.

“Fortunately, we are in good control here, even if every single company affected is too much,” Wisserhof says. “In France, for example, it’s very different with more than 1,200 infected companies.”

According to poultry farmers, the question is whether the risks of contracting bird flu are great for humans. “It just depends on who you ask. In England one person died after caring for sick ducks in their home for three weeks.

Report immediately

Poultry farmers pay close attention to the symptoms of their animals and report immediately if there is a possibility of bird flu. Weserhoff: “We don’t give bird flu a chance to spread and infect people.”

Because the avian influenza virus is so common among wild birds and the ubiquitous presence of water attracts birds, it is inevitable that occasionally poultry will become infected. Wisserhof: “In the long term, vaccinating poultry is the only option to prevent sick animals and the spread of bird flu without culling.”

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