KUALA LUMPUR, Jan 26 — A Monash University Malaysia virologist said modern pig farming only protects public health if it removes the key transmission pathways that fuelled Malaysia’s 1998-1999 Nipah virus outbreak.
Assoc Prof Dr Sharifah Syed Hassan said modern pig farming can protect public health “if all elements” of the system are followed, including measures to reduce exposure to vectors and prevent the entry of infected pigs.
“Modern farming system’s main purpose is to reduce odour, flies, wastewater and reduce its negative impact on animal health, public health, the environment and social wellbeing,” Dr Sharifah from Monash University Malaysia’s Jeffrey Cheah School of Medicine and Health Sciences told CodeBlue in an email interview.
Dr Sharifah, formerly director of research at the Department of Veterinary Services (DVS), said claims linking modern pig farming projects to Nipah outbreaks often misunderstand how the virus was introduced into pigs.
“It should be understood that during the outbreaks of Nipah virus (NiV) in pigs and humans, the introduction or transmission of NiV into pigs are from the bats,” she said, adding that bats “harbour hundreds of species of viruses”.
The molecular virologist said major factors supporting Nipah outbreaks included open pen systems and pig farms located in orchards, which increased the likelihood of pigs being exposed to bat secretions. She said pigs could become infected after eating half-eaten fruit contaminated with bat saliva or through exposure to bat excreta.
Nipah would then spread from pigs to pigs and pigs to humans, particularly within the same farm, through the respiratory route. Dr Sharifah added that wider spread across Malaysia occurred through the purchase and movement of Nipah-infected pigs between farms.
“The major contributing factor is the vicinity of pig farms surrounded by orchards and the virally-infected half-eaten fruits from the saliva of the bats,” she said. “In other words if there is no exposure from bat secretion whatsoever, the risk is very low or nil.”
Dr Sharifah said risk remains low “whether the farms are sporadic or centralised”, as long as the main contributing factors are not present.
The vector-borne disease researcher cautioned that modern pig farms are not automatically protected if biosecurity measures are not enforced, especially when animals are brought in from outside.
“Already infected sick pigs from other ‘dirty’ farms may enter the herd if biosecurity measures are not undertaken,” she said.
“If biosecurity measures are fully abided,” she said, practices such as disease testing before entry, quarantine, and all-in-all-out systems can help keep pig herds “clean from NiV or any other zoonotic viruses”.
Dr Sharifah said biosecurity and biosafety measures such as movement control, quarantine, active testing and surveillance, reporting, and early warning systems can help identify zoonotic spillovers in both centralised and dispersed farms, but stressed that outcomes depend on implementation and enforcement.
She said strong biosecurity is particularly critical for African swine fever (ASF), which has affected Malaysia’s pig industry in recent years.
Dr Sharifah said ASF remains a major threat to pig farms and that “the ‘find one, call all’ approach is the most practical way to help eradicate it, especially when coupled with testing and culling”.
ASF has “a devastatingly high mortality rate, often reaching up to 100 per cent, especially with highly virulent strains”, as the virologist warned that infected pigs that survive “end up being carriers”.
Beyond zoonotic diseases, Dr Sharifah said modern pig farming makes environmental and public nuisance risks easier to control, including wastewater, odour, and vectors.
However, she cautioned that areas with high pig concentrations may increase risks of vector-borne diseases like Japanese encephalitis (mosquito-borne) and the emergence of other arboviruses that may use pigs as amplifying hosts.
Selangor Menteri Besar Amirudin Shari announced earlier today a suspension of the Bukit Tagar centralised pig farming project in Hulu Selangor following heavy criticism, saying alternative sites would be identified.
Last Friday, Prime Minister Anwar Ibrahim urged the Selangor state government to cancel the Bukit Tagar project and consider relocating it, saying that location matters even if the best technology is used.
In CodeBlue’s earlier report, veteran virologist Prof Dr Lam Sai Kit, whose team discovered Nipah during Malaysia’s 1999 outbreak, said centralised farms could strengthen oversight and disease control compared to scattered farms.
“Bigger farms do not mean bigger outbreaks since centralised farms are easier to regulate and isolate,” Dr Lam told CodeBlue. “The 1999 outbreak in Malaysia spread through small and medium farms with poor oversight.”
Dr Lam also said centralisation can enable “strict control measures, dedicated isolation zones for new and sick animals, centralised labs for routine screening and real-time data sharing and better reporting and traceability of livestock”.
