A virus with a fatality rate significantly higher than COVID-19 is once again causing concern in India. Since December, two cases of Nipah virus have been confirmed in West Bengal. Although the immediate threat is a public health crisis, the U.S. swine industry is on alert. According to the Swine Health Information Center (SHIC), the entry of this virus into the U.S. could lead to devastating industry losses and a complex zoonotic challenge.
Pigs are an Amplifying Host
While fruit bats are the natural reservoir for Nipah virus, pigs play a critical role as intermediate or “amplifying” hosts. In the 1999 Malaysia outbreak, pigs were the primary drivers of human infection.
“I was in veterinary school when Nipah virus was first discovered in people and pigs in Malaysia,” says Dusty Oedekoven, chief veterinarian for the National Pork Board. “I recall that there were significant concerns about the potential impact to swine health, as well as public health and the economy, if the virus were to be identified in the U.S.”
Although the virus is most commonly associated with fruit bats and human-to-human transmission, pigs can get the Nipah virus from infected bats or consuming contaminated feed or water, according to the SHIC-funded Global Swine Disease Monitoring Report developed monthly by a team led by Maria Sol Perez at the University of Minnesota Center for Animal Health and Food Safety.
Infected pigs can shed the virus through their saliva, urine and feces. Because the virus can survive for several days in the environment, it spreads rapidly through a barn—and potentially to the people working within it.
A Silent Spreader
One of the most distinct challenges of Nipah virus is that infections in swine are often subclinical, making it a “silent” spreader. However, when symptoms do appear, they vary significantly by age:
• Suckling Piglets: High mortality rates often accompanied by neurological distress.
• Growing/Finishing Pigs: Characterized by a distinctive, loud “barking cough” and respiratory distress. While mortality is lower in this group, the neurological signs are a red flag.
• Adult Pigs: May suffer acute death, bloody nasal discharge, or abortions.
Protecting the U.S. Pork Industry
The risk of pig-to-human transmission is considered low compared to bat-to-human transmission, but the stakes are incredibly high, SHIC reports. The 1999 outbreak in Malaysia resulted in the culling of over one million pigs, nearly destroying the local industry.
To prevent a similar scenario in the U.S., strict biosecurity and surveillance are key.
“Biosecurity is the cornerstone of protecting herd health and preventing disease entry,” says Megan Niederwerder, executive director of SHIC. “When we think about risks of introducing new diseases, biosecurity is critical to consider for daily entry hazards such as personnel, supplies, equipment and feed as well as transport of pigs throughout production.”
In a recent summary of lessons learned through the SHIC-funded Standardized Outbreak Investigation Program, entry events ranked high risk most frequently included movements of cull sows, weaned pigs and mortalities from the farm, she points out.
“Along with biosecurity, implementing consistent diagnostic surveillance is essential to detecting disease early, identifying emerging pathogens, and preventing regional or system-wide spread,” Niederwerder says.
Diagnostic surveillance helps identify emerging pathogens by continuously monitoring, analyzing and interpreting health data to identify unusual disease patterns, such as unexpected increases in severity or incidence
“Emerging pathogens pose a threat to the health of our pigs and people,” Oedekoven says. “The industry-led National Swine Health Strategy includes a goal to keep foreign and emerging disease out, which includes ongoing global disease monitoring and disease detection and response planning.”
Those responsibilities include using Pork Checkoff funds to partner with SHIC to monitor global emerging disease and provide information to U.S. producers.
“I’m proud of SHIC’s work, along with the collaboration within the animal health community, to help monitor, prevent and prepare for emerging diseases,” Oedekoven says.
