Pig virus seen as culprit hog deaths in Luzon farms

A Filipino scientist has warned that a virus, present in pigs worldwide, is associated with a disease that has a mortality rate of as much as 100 percent and may be the cause of unexplained deaths in pig farms in Luzon last year.

Dr. Romeo Sanchez, a veterinary science expert, said the deaths of pigs in Batangas, Bulacan, Tarlac and Laguna in 2003 were "suspect" since farmers told him that these pigs showed symptoms "similar to hog cholera" but the corresponding vaccine was not effective in preventing the deaths.

"There has to be an urgent effort to look into this disease," Sanchez said.

The porcine circovirus 2 (PCV2), according to Sanchez, is associated with post-weaning multisystemic wasting syndrome (PMWS), which affects five to 50 percent of infected pigs, of which as much as 80 to 100 percent die.

Pigs with PMWS become emaciated, develop jaundice and suffer from a decreased growth rate. Some develop respiratory problems, diarrhea and gastric ulcers.

"How the virus causes this disease is unclear. There are no vaccines available yet," he said at a paper presentation of finalists for a talent search for young scientists, sponsored by the National Academy of Science and Technology (NAST) and DuPont Far East Inc.

Sanchez explained that while the virus is present in most, if not all, pigs, not all of them develop PMWS. He attributes the suspicious deaths to two factors, genetics and the conditions in which pigs are raised.

"Pigs are bred according to which has the most number of teats or produces the most number of piglets. Also, while farms were spacious before, now you can have 100,000 pigs in one farm," he said.

The pigs affected by these two factors may have weakened immune systems, according to Sanchez. He noted that with the onset of the rainy season, more pigs will be stressed out because they will suffer from the cold aside from being confined in a small space.

Sanchez said thus far, there has only been one report of PCV2 infection in the Philippines, allegedly at pig farms in the towns of Tiaong and Tayabas in Quezon.

Citing the need to improve the diagnosis of PMWS, he said the veterinary experts from the University of the Philippines-Los Baños campus will study farms in Batangas by June.

Sanchez said there is yet no evidence of the virus infecting mice, sheep, cattle or humans but another scientist, NAST president Dr. Perla Santos Ocampo, aired her concern over this possibility.

"With viruses (from animals) jumping to humans, I don’t know," she said. Scientists have found the virus that causes Severe Acute Respiratory Syndrome jumped from animals to humans in China.

PMWS was first recognized in the United States in 1996, and was found in commercial pig farms in Canada in 1998, Sanchez said. The disease has also been recognized in South America and Europe.

However, he said that when scientists at Kent University in Belgium studied serum samples from as far back as 1969, they found that pigs then had the virus in their system.

The PCV2 has spread to practically all parts of the world because it belongs to Circoviridae, a family of small, highly resistant viruses that can survive up to eight weeks when put in an incubator set at 37 degrees Centigrade, Sanchez said. While the porcine circovirus appears to specifically infect pigs, other circoviruses cause disease in birds, plants and humans.

The PCV2 has since been linked with other diseases in weaned and fattening pigs, disorders in newborn piglets, and fetal deaths.

Sanchez said three companies are already working on a vaccine for the virus, and this may be available in one year. He added that farmers, in the meantime, have to fall back on "basic biosecurity" measures by reducing stress and removing sick pigs.

According to www.pighealth.com, PCV2 "has been shown to be shed in feces and nasal secretions of recently infected pigs and presumably this is how it spreads from pig to pig. It is not known how it spreads from herd to herd but, like other viruses, movement of pigs between herds is probably a major factor. Since it is a relatively hardy virus, it is also likely to spread on clothes and equipment."