Virus detective work in Indonesia
The case of the mysterious livestock disease
Yogyakarta, Indonesia - Troubling news arrived at the Disease Investigation Centre in Central Java one day in August 2003. A poultry buyer had lost 7 000 chickens overnight. Cause: unknown.
"It was unusual because of the speed and the number of dead," says Centre pathologist Walujo Budi Priyono. He got a chance to investigate the phenomenon soon afterwards when a farmer brought in a sick chicken for diagnosis. When the bird died, he opened it up.
"I found abnormal brain tissue under the microscope," he recalls. "From my studies I was familiar with avian flu and I started to think it might be that. We isolated the virus and four months later confirmed the disease."
As the epidemic exploded across Java in early 2004, finding out how the virus spread required quick detective work. Without an understanding of transmission, control strategies couldn't be tailored to local circumstances.
A team of 15 veterinarians and technicians was marshalled to conduct a survey in villages and markets, searching for the path between one outbreak and the next. Nothing was ruled out from the list of suspected virus carriers: wild birds, ducks, pigs, insects, egg and chicken buyers, commercial feed, vehicles or equipment.
Because infected poultry excrete the virus in high concentrations, suspicion eventually fell on ways the droppings might be tracked from farm to farm, such as on clothing, shoes, egg trays, bird cages or even the tires of motorcycles and trucks.
Investigating the buyer
"The buyers could be the main source of spreading the disease. We saw that they went from one farm that had suspected avian flu to another farm and within three days it broke out there," says Centre Director Dr Isep Sulaiman. "Then, the buyer sold the infected live chickens at market, people took them home and didn't kill them immediately and it spread even further."
Similar discoveries were being made by animal health officials in all the affected Asian countries. While other suspected carriers, such as ducks and pigs, still need further study, understanding the role of buyers in the spread of the disease has led to much tighter controls on access to farms (see "Containing infection at source - signs of success" in related stories at right).
As for how the disease got to Indonesia in the first place, the Centre has a few suspects but no hard evidence: migratory birds, old hens smuggled into the country as cheap food, Pekin ducks imported by restaurants or imported breeding stock.
"The virus may even have always been here and through environmental changes such as in temperature or humidity mutated and became virulent," says Dr Nana Supriatna, a ministry of agriculture veterinarian on loan to and paid by FAO to handle liaison for the many international bird flu experts who come to give advice.
"We're just in chapter five of a twenty-chapter book on avian flu, there is so much we don't understand," he adds (See "Better disease prevention is the answer" in related stories at right).
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