Pig Ebola May Lead Scientists to ‘Elusive Reservoir’ of Virus

By Jason Gale

Dec. 11 (Bloomberg) -- The first known Ebola infections in pigs may help researchers answer a question that’s confounded them since the deadly virus was first discovered more than 30 years ago: where it comes from.

International scientists will converge on farms in the Philippines to help local authorities discover how pigs contracted Ebola-Reston, a monkey-killing strain not known to harm people. The findings may help identify which species carries the virus in the wild without getting sick, enabling the pathogen to persist undetected in the environment, said Juan Lubroth, head of infectious diseases in the animal health unit of the Food and Agriculture Organization in Rome.

Knowing the natural host of Ebola will help people better protect themselves against one of the most-feared infectious diseases. African strains usually kill 50 percent to 90 percent of those infected through lethal bleeding and organ failure, according to the World Health Organization.

“Since the 1970s, scientists, veterinarians, microbiologists and physicians have been looking at thousands of species to see if they can find this elusive reservoir, and we have been pretty much empty-handed,” Lubroth said in a telephone interview today. “This opens up avenues to delve into the ecology and do more searching.”

Ebola was first recognized in 1976 after an outbreak near the Ebola River in the Democratic Republic of Congo, formerly known as Zaire.

Thirteen years later, Ebola-Reston was discovered in the U.S. in association with an outbreak of viral hemorrhagic fever among monkeys imported from the Philippines to Reston, Virginia. The virus was found among Philippine monkeys in the U.S. again in 1990 and 1996, and in Italy in 1992. In October, for the first time, the strain was found in Philippine pigs.

Pig-Ebola Nexus

“What is the connection between the natural habitat of Ebola-Reston and swine production? That needs to be teased out in the Philippines,” Lubroth said.

Ebola-Reston turned up in six of 28 swine samples tested at a U.S. Department of Agriculture laboratory in New York, said Davinio P. Catbagan, the Philippines’ chief veterinary officer. The infected pigs were traced to two commercial and two backyard farms in three provinces north of Manila, he said. Further testing found no new cases, including among 42 people involved in caring for the animals.

“We’re still trying to find out how it came to the pigs,” Catbagan said in a telephone interview today.

Both Ebola, and a related virus known as Marburg hemorrhagic fever, are thought to infect humans via primates.

Snakes, Guinea Pigs

Disease trackers have tested everything from snakes to guinea pigs in the search for an animal reservoir and have been repeatedly led back to caves, mines and bats.

A 2005 study published in the journal Nature found evidence of symptomless infection by Ebola in three species of fruit bat in West Africa, indicating that these animals may be acting as a reservoir for the virus.

“It would merit looking at it in the natural habitat in the Western Pacific further,” Lubroth said. “We are only scratching the surface.”

The Philippines government said yesterday it would like technical assistance from the WHO, FAO and the World Organization for Animal Health in studying the disease and assessing what potential health risks it may pose.

“At the moment, it’s not a dangerous pathogen, but we cannot be sure it will remain like this,” said Soe Nyunt-U, the WHO’s representative to the Philippines. “We have to make sure we understand the ecology of the virus really well.”

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