Backyard grown pigs have hepatitis E virus, says study

MANILA, Philippines - Pigs raised by Filipino backyard hog farmers in rural areas have high prevalence of hepatitis E virus (HEV), posing a potential risk of HEV infection among local residents, according to an article appearing in the latest issue of Livestock and Meat Business  (LaMB) Magazine.

The article, written by agricultural journalist Fermin Diaz, cited a recent study by a team of Japanese and Filipino doctors and scientists from Tohoku University Graduate School of Medicine and the National Institute of Infectious Disease in Japan and Philippine-based Research Institute for Tropical Medicine.

The team said genotype 3 of HEV was observed in their study, but pointed out that genetically diverse strains of HEV were also found to be circulating in pigs.

HEV genotype 3 is a strain not known to cause disease outbreaks, but it accounts for 35 percent to 80 percent of chronic and sporadic hepatitis infections in the Indian subcontinent, Southeast Asia and Australia, according to the World Health Organization.

Genotypes 3 and 4 are considered to be of zoonotic origin, or diseases transmittable from animals to human and are together recognized as an important cause of sporadic hepatitis cases in humans both in developing and industrialized countries, WHO says.

While HEV infection is a significant public health concern and pigs are known to be an important source of sporadic HEV infections in humans, there has been no epidemiological data available regarding HEV infection among hogs and people in the Philippines until their study, the team explained in their paper published in the BioMed Central (BMC) Veterinary Research in late January 2015.

The team, led by Dr. Hitoshi Oshitani of the Tohoku-RITM Collaborating Research Center on Emerging and Reemerging Infectious Diseases based at the RITM compound in Alabang, Muntinlupa City, said their findings were based on blood and rectal swab samples taken between July 2010 and June 2011 from 299 pigs from 155 households in four barangays of San Jose, Tarlac, namely Villa Aglipay, Moriones, Pao, and Lubigan.

The animals, with a median age of four months, consisted of grower pigs aged two to four months and breeder pig eight to 24 months old.

When the study was made, the hogs were healthy, raised in simple piggeries in backyards, fed with commercial feeds or kitchen residues, and living with other domestic animals such as chickens and ducks.

To assess the HEV infection status among the pigs, the team conducted Enzyme-linked immunosorbent assay (ELISA) which revealed that half or 50.3 percent of the blood samples taken from 93 households in the four barangays tested positive for anti-HEV IgG and another 23 percent for anti-HEV IgM.

On the other hand, a total of 22 rectal swabs, or 7.4 percent of the fecal samples of pigs from 16 households were positive for HEV ribonucleic acid (RNA) virus.

The average prevalence of any of the three markers (anti-HEV IgG, IgM, and RNA) in the pig population was observed at similar range between 47 percent and 62.5 percent among the four barangays, the team said in their paper.

“Overall, two thirds of the households had pigs positive for either anti-HEV IgG, IgM, or viral RNA. Among the 22 RNA positive samples, six samples were positive for both anti-HEV IgM and IgG, and 10 samples were only positive for anti-HEV IgG. The remaining six samples were negative for both anti-HEV IgM and IgG,” the team added.

In their study, the team, which includes Xiaofang Liu, Tiancheng Li, Japanese nationals Mariko Saito,Yusuke Sayama, Ellie Suzuki, Yuki Furuse, Mayuko Saito, Akira Suzuki and Filipinos Fedelino Malbas and Hazel Galang, said the prevalence of anti-HEV IgG and IgM in breeding pigs were higher than that in growing pigs. Majority or 91 percent of detected viruses belonged to subtype 3a, they added.

The team pointed out that HEV infection in commercial pig farms had already been previously reported outside in Japan, Germany and Italy, but said there were very few reports on HEV infections in local backyard pig farms where local people could be more frequently exposed to pigs or pig feces because of the open breeding system and poor sanitation of backyard pigs.

It said the study was conducted in San Jose, Tarlac, a third-class municipality, because the area is mainly  rural where the density of household-raised pigs is quite high. “Besides, the local people commonly consume the cooked pig livers, pork and sausages made by local manufacturers. Therefore, workers in slaughterhouses and pork handlers in the local area are at potential risk of getting HEV infection,” the team said.

“However, there are no available data on viral hepatitis incidence due to HEV in the Philippines. The human health impact of HEV should be properly defined to establish appropriate interventions, “ the team recommended.

The study, which appeared in  the latest issue of LaMB Magazine, is one of several highly-informative articles contained in the agribusiness publication.

The quarterly magazine is available by subscription (email: [email protected] or call 0918-5200470). It can also be accessed in digital format through its partnership with Magzter, the world’s largest and leading online magazine newsstand.  

The magazine can be previewed here: http://www.magzter.com/PH/Farm-Media-Development-Enterprises/LaMB-Philippines-Magazine/Animals-and-Pets/