International experts probe deadly Ebola Reston virus outbreak in Philippine pigs

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Thursday, January 8, 2009

Transmission Electron Micrograph of the Ebola Virus. Hemorrhagic Fever, RNA Virus.

Global animal and health authorities' emergency mission to the Philippines is investigating whether the strain of deadly Ebola Reston virus, recently discovered in dead pigs, poses a threat to human health. Unlike more-deadly strains of Ebola virus, Philippine health officials say this particular strain, known as the Reston ebolavirus, has never caused human illness or death, and it's not immediately clear there is a public-health issue.

A 22-member team of experts from three United Nations agencies arrived in Manila on Tuesday for a joint risk assessment on the virus contamination of local swine, to help the government contain the outbreak. The mission will coordinate with the Philippine counterparts - the Departments of Agriculture and Health. According to chief veterinary officer, Davinio P. Catbagan, six of 28 swine samples tested positive for Ebola-Reston by the U.S. Department of Agriculture laboratory. The infected pigs came from two commercial and two backyard farms in three provinces north of Manila. Both Ebola and related Marburg hemorrhagic fever, are considered to infect humans via primates.

The Straits Times reported that as of December, about 6,000 pigs at Pandi, Bulacan and Talavera farms had tested positive for the Ebola-Reston virus. "Eating pork remained safe as long as it is handled and cooked properly (at a minimum of 70 degrees Celsius or 158 degrees Fahrenheit) and bought in outlets accredited by the government's National Meat Inspection Service," said a joint statement by the World Health Organisation (WHO), World Organisation for Animal Health (OIE) and Food and Agriculture Organisation (FAO). "Our teams are doing field and laboratory investigation to determine where the Ebola-Reston virus came from and how it was transmitted," Caroline-Anne Coulombe, WHO risk communications officer, explained.

Crab-eating macaque (Macaca fascicularis) in Lopburi, Thailand.

According to FAO team leader, Juan Lubroth, it was the first time that the Ebola-Reston virus strain had infected animals other than monkeys and the first recorded worldwide in swine. The U.N. mission is scheduled to perform 10 days scientific tests, on two hog farms in Manaoag, Pangasinan and Pandi, Bulacan, but it would take months to publish evaluation reports on the virus.

As early as May, a high incidence of swine sickness and death in three provinces caused Philippine authorities in August to send samples from the dead pigs to the NY Plum Island Animal Disease Center. The results found the presence of several diseases, including Ebola Reston virus and PRRS.

In late October laboratory tests confirmed that pigs in Nueva Ecija and Bulacan farms were infected with the Ebola-Reston virus and the highly virulent strain of Porcine Reproductive and Respiratory Syndrome Virus (PRRS). In early 2007 pigs on those farms died at a faster rate than usual amid the conducted lab tests. PRRSV, or Blue-Ear Pig Disease (zhū láněr bìng 豬藍耳病), is a viral and economically important pandemic disease which causes reproductive failure in breeding stock and respiratory tract illness in young pigs. Initially referred to as 'mystery swine disease' or 'mystery reproductive syndrome', it was first reported in 1987 in North America and Central Europe. The disease costs the United States swine industry around $600 million annually.

In December, the Philippine health authorities conducted testing of about 10,000 swine in two northern Luzon quarantined farms. Reuters reported that "the Ebola-Reston virus in some pigs in two commercial farms and two backyard farms in the Philippines were discovered by accident in United States laboratory tests in September, when samples were sent to test another disease."

Ebola virus is one of at least 18 known viruses capable of causing the viral hemorrhagic fever syndrome. It is the common term for a group of viruses belonging to genus Ebolavirus, family Filoviridae, and for the disease which they cause, Ebola hemorrhagic fever. The virus is named after the Ebola River where the first recognized outbreak of Ebola hemorrhagic fever occurred in 1976. The viruses are characterized by long filaments and have a similar shape to the Marburg virus, also in the family Filoviridae, and share similar disease symptoms. Since its discovery, Ebolavirus has been responsible for a number of deaths.

In the central Democratic Republic of Congo (DRC), the highly contagious Ebola virus was first detected in September, according to Medecins Sans Frontieres. "As of Tuesday January 7, a total of 42 patients have been reported with suspected Ebola haemorrhagic fever in the province of Western Kasai... 13 of these 42 patients suspected of having Ebola have died," it said.

Transmission Electron Micrograph of the Ebola Virus.

The Reston ebolavirus is suspected of being either another subtype of the Ebola or a new filovirus of Asian origin. It was first discovered in crab-eating macaques originating in the Philippines, from Hazleton Laboratories (now Covance) in 1989. This discovery attracted significant media attention and led to the publication of The Hot Zone. There was then, an outbreak of viral hemorrhagic fever among monkeys imported from the Philippines to Reston, Virginia. The Ebola-Reston strain was discovered among Philippine monkeys in the U.S. again in 1990 and 1996, and in Italy in 1992.

According to the World Health Organization, African strains kill 50 percent to 90 percent of those infected through lethal bleeding and organ failure. “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,” Juan Lubroth, head of infectious diseases in the animal health unit of the Food and Agriculture Organization in Rome, explained.

Despite its status as a Level-4 organism, the Reston ebolavirus is non-pathogenic to humans and is only mildly fatal to monkeys; the perception of its lethality was skewed due to the monkey's coinfection with Simian hemorrhagic fever virus (SHFV). During the incident in which it was discovered, six animal handlers eventually became seroconverted, one of whom had cut himself while performing a necropsy on the liver of an infected monkey. When the handler failed to become ill, it was concluded that the virus had a very low pathogenicity to humans.

In January 1997, The Philippines Department of Environment and Natural Resources had ordered the immediate slaughter of some 600 monkeys in Ferlite, a breeding farm in Laguna, to prevent an outbreak of the deadly Ebola Reston strain virus.

The US Centers for Disease Control and Prevention had donated 8,000 test kits to diagnose the ebola reston strain. "I am more concerned in the international community because we have proven in our December sales that this ebola did not affect consumer confidence," Albert R. T. Lim, president of the National Federation of Hog Farmers, Inc., warned. The Philippines Department of Agriculture (DA) has directed the Bureau of Animal Industry (BAI) and the National Meat Inspection Commission (NMIC) to conduct swine tests in South Cotabato using the US test kits for the Ebola Reston virus, before approval of the "Meat in a Box" shipment to Singapore. The initial export of the meat for December was deferred pending outcome of the ERV tests.

Meanwhile, in eight Barangays of Santa Maria, Davao del Sur, in Mindanao, at least 50 pigs died since December due to viral and bacterial infections. Dr. Nestor Barroga, provincial veterinarian, said that he could not however detect yet the type of the infecting virus. The village of Pong-pong had the largest number of casualties. Mercy Olalo, a hog raiser, said their pigs would suddenly become weak and eventually die. "The pigs developed red skins and they salivate excessively," she said.