Bill C-275 overestimates risk of human-to-animal disease transmission

The discussion in Parliament on Bill C-275—an Act to amend the Health of Animals Act (biosecurity on farms)—would benefit from some additional public health perspective on the potential risks of zoonotic transmission between humans and farm animals. After being introduced in the House in May of last year, C-275 passed third reading on Nov. 29, and is now in the Senate. The debate around this bill as it worked its way through the House of Commons was marked by discussion of the potential risks and harms associated with diseases spreading between humans and animals. My intent is neither to endorse nor oppose this bill. Rather—drawing from my background in public health, infectious diseases, and virology—I aim to shed light on the degree of risk that exists when it comes to zoonotic transmission. Dat Nguyen, a cancer researcher at the University Health Network in Toronto, Ont., holds a master of science degree in virology and immunology from the Johns Hopkins School of Public Health. Photograph courtesy of Dat Nguyen C-275—a private members' bill introduced by Conservative MP John Barlow—seeks to penalize unauthorized access to husbandry facilities with fines or imprisonment. Its primary aim is to deter activists from occupying these spaces. However, it's crucial to clarify—as several MPs have highlighted—that this bill doesn’t criminalize animal rights protests or impede whistleblowers. On Nov. 22, Conservative MP Branden Leslie mentioned the African Swine Fever (ASF) virus and the catastrophic outbreak of that disease in China that began in Liaoning in 2018. This outbreak led to a 40 per cent decline in swine stocks and an estimated $10-billion loss by 2019. While these numbers are alarming, understanding the transmission dynamics of ASF is crucial. For a virus to infect humans, it must bind to specific receptors on human cell surfaces—usually ones that are highly species-specific. Thus, the likelihood of a swine virus infecting humans—or vice versa—is minimal. Even in these cases of zoonotic jumps, the virus rarely reverts to infect the original species. ASF, for instance, is primarily vector-borne: carried by ticks that have fed on the blood of infected swine, and then transmitted to a new pig when feeding on it. The risk of transmission to farm animals via trespassers' clothing or bodies is low, because the viruses do not survive for long in the gut of the tick. Instead, the likelier scenario involves infected pigs introduced from other farms carrying the virus via ticks, and transmitting the disease to the new facility. The risk of avian flu was also brought up on Nov. 22 by Bloc Québécois MP Caroline Desbiens. Unlike ASF, there have been previous avian influenza outbreaks reported in Canada in 2014, 2015, and 2016. These outbreaks caused significant financial losses for affected farms and created considerable distress among local farmers. Yet, it's crucial to emphasize that the likelihood of avian flu transmission from humans to poultry is low. As explained above, it is hard for a virus to infect both humans and other common farm animals. Both avian and human flu are caused by different species of the influenza virus. These viruses exhibit distinct preferences for cellular receptors: avian flu viruses favour the Alpha-2,3 Sialic Acid receptor found on bird cells. Human cells express lower levels of this receptor and prefer the Alpha-2,6 isoform, which human influenza viruses target. Consequently, the risk of trespassers transmitting the influenza virus to farm animals is markedly low. Instead, historical evidence and ongoing observations, such as the recent outbreak in British Columbia, suggest that migratory birds often serve as the primary carriers, transmitting the virus to farm poultry. This article's purpose is not to downplay animal rights advocacy or the need for farm security. It is important for our society to be humane to the animals in our care and respect the right of private property—particularly for our hard working farmers, upon whom our nation relies. Instead, this article seeks to inform the public about infection risks and prevent undue panic—especially as our country continues to recover from the COVID-19 pandemic. I neither support nor oppose the rhetoric used during the parliamentary session, but I believe that relying solely on this bill to prevent outbreaks may be misguided. There are other crucial actions our honourable Members of Parliament should consider for the purpose of enhancing biosecurity in our husbandry industry, such as stricter import regulation, broader surveillance efforts, and more funding to research. Dat Nguyen is engaged in SARS-CoV-2 and cancer research at the University Health Network in Toronto, Ont. He holds a master of science degree in virology and immunology from the Johns Hopkins School of Public Health, as well as two bachelor degrees in public health and infectious disease biology from the University of California, Berkeley. The Hill Times