Could JEV Leave the Pork Sector DOA?

Monday, May 13, 2024

'This is one swine disease that we certainly have on our radar.'

By Geoff Geddes

If you thought three letters couldn't do much damage, you've never dealt with the CRA. From PRRS to PED, the pork sector in Canada is full of scary acronyms, and one that recently caught the attention of the industry is JEV (Japanese Encephalitis Virus).

This zoonotic pathogen (caused by germs that spread between animals and people) can lead to serious disease in humans and trigger abortions and stillbirths in sows. Though it has yet to reach Canada, the potential for huge economic losses in the pig sector could make it worse than a federal audit.

"JEV is known as an arbovirus. An arbovirus by definition is an insect-borne virus that transmits to other vertebrates," says Dr. Christa Arsenault, manager of the Canadian Swine Health Intelligence Network (CSHIN). "It originated in Asia and affects about 70,000 people per year in the Western Pacific region, especially the very young and very old, with around a 20 to 30 per cent mortality rate."

Though the overall death rate in pigs is lower than for humans, the risk depends on when the animal is infected.

"The younger the pig is at that point, including in utero from an infected sow, the higher the mortality," says Dr. Arsenault. "It is a hard disease to detect, so we may need to look for patterns that could alert swine veterinarians.

"Because JEV is mosquito-driven, the majority of cases may be concentrated in a specific area, such as near a body of water."

This disease bites

The virus is initially passed from certain types of mosquitoes to birds that live near water. If an infected mosquito bites a pig, the latter will replicate and amplify the pathogen. Though JEV has been reported in humans since the 19th century, the ability of pigs to act as amplifying hosts was not known until the 1960s.

Still, that was 60 years ago – so why all the fuss today?

"About a year and a half ago, JEV landed in Australia and caused clinical disease in both humans and pigs," says Dr. Egan Brockhoff, veterinary counsellor for the Canadian Pork Council (CPC). "That caught everyone's attention, sparking risk assessments by the National Pork Producers Council in the U.S. and the Canadian Food Inspection Agency (CFIA), through CSHIN, in Canada."

The prevailing theory is that if JEV arrived on our shores, it would most likely be via mosquitoes on a plane from an infected area such as Australia.

"That mosquito would have to survive transport, bite and infect a human or animal, and establish a disease reservoir in North America," says Dr. Brockhoff. "We have the right birds in Canada to transmit it, though it may be more likely in the U.S. given its favourable climate versus our harsh winters."

As far as the potential impact on the Canadian pork sector, our best guide may be the Land Down Under.

"In Australia, we saw the virus move from farm to farm and cause disease," says Dr. Brockhoff. "That led to abortions and stillborn pigs, neurological disease, and some damage to fertility in both males and females. Should JEV reach Canada, the production loss could be significant, though we can't put a number on it at this point."

Since JEV is similar to West Nile virus, it could follow a similar path and establish as a seasonal virus in Canada.

Given the risks if we let JEV in, the better option is simple, but not easy: Keep it out.

An intent to prevent

"Prevention is a huge focus for us at CSHIN when it comes to pig disease," says Dr. Arsenault. "We have established a national surveillance network with experts from across Canada meeting quarterly to discuss emerging issues in swine health."

As part of the meetings, CSHIN takes input from The Community for Emerging and Zoonotic Diseases (CEZD). That group is "a virtual network that includes representatives from federal, provincial and municipal governments, academia and the private sector who have an expertise in public, animal and environmental health.

"CEZD focuses on emerging international swine diseases of concern that could threaten Canada and North America in the future," explains Dr. Arsenault.

"It gathers the latest data to help us build knowledge and prepare for the worst, and that's exactly what it did in the case of JEV."

Such early warning activities are critical, as the faster the industry detects a disease threat, the more we can limit the damage. With JEV, this would mean controlling mosquito populations that could carry and transmit the virus.

"Similar to West Nile virus, we would want to eliminate areas where mosquitoes breed near pig farms, such as low-standing water sources," says Dr. Arsenault.

"Obviously, producers should avoid having a pond adjacent to their facilities. We could also look at controlling mosquitoes through spraying, though that is the least desirable mechanism given its effect on the environment."

Not all mosquitoes carry JEV, with two types responsible for the bulk of the infection, so industry could also mitigate the fallout by focusing on the main culprits.

At the federal level, the Government of Canada is doing its part to prepare.

In the event that JEV is detected here, a series of measures, including an epidemiological investigation and control measures, would be implemented to mitigate its impact.

According to a CFIA spokesperson, "intensified surveillance efforts would target animals and disease vectors (mosquitoes) to promptly identify and monitor the spread of the virus within the country. Swift response and coordination among various authorities, including the Canadian Food Inspection Agency (CFIA) and the Public Health Agency of Canada (PHAC), provinces and territories, would allow for a cohesive response. PHAC would lead on measures related to public health."

While vaccines have been a game-changer for both human and animal disease, they might not be the answer with this pathogen.

"To date, swine vaccination against JEV has not been widely practised in countries at risk," says Dr. Arsenault. "The cost is high and there is a limited window to vaccinate effectively, both of which have limited the uptake."

As with many aspects of daily life, climate change could also exacerbate the problem of JEV.

"As the climate in North America becomes more favourable to vectors (carriers) of this disease, the risk continues to grow," says Dr. Brockhoff. "Though there is still much to learn, there is clearly a link between the movement of mosquito-borne diseases and climate change."

In the meantime, the Canadian pork sector will work to stay on top of developments with JEV and continue to assess the threat.

"This is one swine disease that we certainly have on our radar," says Dr. Brockhoff.

"In my role with the veterinary council of the CPC, I speak about JEV regularly when talking about potential risks in 2024, '25, '26, and beyond. Like the U.S. pork industry, we plan to be ever-watchful and see what happens from here.

"At this point, that's about all we can do." BP