Coronaviruses are a family of zoonotic viruses; zoonotic meaning that they can pass from animals to people. SARS is one example, ebola, MERS and H1N1 are others. The sources have been animals as varied as pigs, monkeys, poultry, civet cats and camels. The strain of coronavirus (named COVID-19) currently in the news has been declared a “public health emergency of international concern.” The race to find a vaccine or prevent deaths is intense. To help us understand more about coronaviruses and zoonoses in pigs and people, Gentec spoke to Dr. Egan Brockhoff, Veterinary Counsellor for the Canadian Pork Council.
Gentec: How do we know that the source of a human disease might be animals? How do we know to do a “reverse diagnosis?”
Dr. Egan Brockhoff: Scientists do a whole-genome sequence of the bacteria or the virus, then they look for similarities with other known bacteria or viruses. That indicates where it’s most likely to have originated. It might sound simple but it involves significant scientific exploration. For COVID-19, the pangolin seems to be the animal source. The fact that these animals are eaten makes them a likely source of the jump, but that still needs to be confirmed.
Gentec: Porcine epidemic diarrhea (PED) virus, which is a pretty nasty pig disease, is also a coronavirus that could spread to humans. Why hasn’t it?
Dr. Egan Brockhoff: PED is a delta coronavirus. COVID-19 is a beta coronavirus. Even though they’re part of the same family, they’re only very distantly related. PED is an enteric virus that causes intestinal illness whereas the beta COVID-19 infecting humans is a respiratory virus. Because they’re so different, PED isn’t likely to jump over to humans.
Also, COVID-19 is a new virus. Once it has adapted to its host, it’s not likely to jump back to animals. To give you an example, MERS came from camels and can still be found in camels. But when viruses adapt to a new host, they don’t re-adapt to their original host as easily. Now that COVID-19 has become a zoonose and infected humans, we’re not very concerned that it will jump back. If it does, it would probably go to its most recent host.
Gentec: We’ve seen how fast and how wide zoonoses can spread. Which organizations are involved in containing an outbreak?
Dr. Egan Brockhoff: On a global level, the World Health Organization is responsible for human health, and the OIE (World Organisation for Animal Health) is responsible for animal health. At the federal level in Canada, Public Health Agency of Canada and Health Canada are the competent authorities for human health, and the Office of the Chief Veterinary Officer for Canada and the Canadian Food Inspection Agency are the competent authorities for animal health. Then each province has a chief medical and veterinary officer as well. In other words, many organizations must work together to find the best methods of control.
Gentec: So how do they talk to each other? What do they monitor? How do they decide on the best actions to take?
Dr. Egan Brockhoff: Both the WHO and the OIE are in constant back-and-forth communication with their member states. In terms of COVID-19, both were consulted, and the WHO has now landed a body of experts into China to work on this disease. In fact, renowned Canadian epidemiologist Dr. Bruce Aylward will be leading that team.
Canada and other developed nations have a very robust infrastructure for communicating with the WHO and OIE but in other countries, that may vary more. In this situation, China is working very hard with its public health authorities to understand and contain the disease, and the WHO is assisting and communicating back to the OIE. But let’s be clear, COVID-19 is not an animal health outbreak, it’s a public health outbreak. The OIE doesn’t have to be highly engaged beyond helping the authorities understand the coronavirus in its most recent species.
Gentec: What actions are being or have been taken to mitigate spread of PED in animals?
Dr. Egan Brockhoff: Again, let’s be clear. PED is not a zoonose, it’s a highly infectious enteric virus—for pigs. So bioexclusion, that is, the external biosecurity efforts to take to keep disease out of the farm are key. For PED, critical steps including washing all incoming transports to ensure they are virus-free, making sure you limit access to the controlled access zone around the farm, ensuring that people who must enter the farm wear boot covers, remove their footwear and clothing when they step over the line and go through a shower on the way back. And of course, wearing farm-specific clothing.
African swine fever kills nearly all infected pigs. The same measures of bioexclusion will keep it out of the farm. Because it’s not an aerosol virus (transmission through droplets or particles in the air), it moves by allowing infected animals or products to move on or off a farm. For example, feeding contaminated food items to healthy pigs will expose them to this disease. Because people can’t get it, good basic bioexclusion will keep the virus from affecting the population.
Gentec: The founding head of Ontario Public Health has spoken publicly that travel bans for zoonoses are ineffective, xenophobic and not evidence-based. Do you agree?
Dr. Egan Brockhoff: Every disease has unique features in terms of infectivity rates and routes by which it infects, so the story changes a bit but in general, that’s accurate. The WHO echoed those sentiments as well. Travel bans are not necessarily effective. Typically, with infectious diseases, people are infectious before they have clinical signs. The flu is a good example. All the early work done on COVID-19 echoes that. So, people can move all over the world before they know they’re infected. At best, travel bans can slow the spread but not contain it.
Gentec: Do you find that the public are informed and correctly informed about zoonoses, particularly those coming from pigs?
Dr. Egan Brockhoff: The public has every opportunity to access good information from the competent public health authorities. But there’s absolutely no question that social media has made it challenging for the public because there’s so much non-professional information out there as well.
Gentec: What’s your message to the public about zoonoses?
Dr. Egan Brockhoff: Washing your hands is one of the most effective things you can do to protect yourself from all infectious diseases, whether they come from other humans or from animals. Use good sanitation in the kitchen. And cook meat to a temperature that kills bacteria and viruses. You can use a food thermometer for that. Meat doesn’t have to be burnt to a crisp to be safe. And you don’t have to become a vegetarian either. Plenty of foodborne illnesses come through plants.
Gentec: Thank you, Dr. Brockhoff, for taking the time to do this interview.