Nabijon Juraboev, a sheep farmer on the steppes of central Uzbekistan, was trying to protect his flock from the deadly "sheep pox" virus when he bought what he thought was a vaccine from a state agriculture supplier.
Within days of mixing the dry, brown substance with liquid and administering it to his sheep, his flock was dead.
Juraboev is not alone. He says all farmers in his district of Jizzakh Oblast have lost most of their sheep after giving them the substance.
According to unofficial estimates, more than 35,000 sheep may have died in Jizzakh Province alone and as many as 50,000 nationwide.
Meanwhile, in neighboring Kyrgyzstan, more than 1,700 sheep are dead in that country's Jalal-Abad Oblast after a smuggler from Uzbekistan apparently sold the vaccine on the black market.
Farmers in both countries want to know who is ultimately responsible.
State authorities in Uzbekistan are not commenting on the subject, and state-controlled media has avoided reporting on the story. Kyrgyz authorities have launched a criminal investigation and results of laboratory tests on the dubious vaccine are expected on September 28.
The British Veterinary Association says it can only speculate without testing the substance, but it says the problem is either the vaccine itself or the result of its being improperly administered.
The vaccine could be outdated or spoiled because it wasn't refrigerated properly.
Corruption is another possibility. Someone could have skimmed off some vaccine to sell on the black market, mixing the remainder with another substance to hide the theft.
Another possibility is that the vaccine was a bogus, counterfeit product manufactured in another country, such as China, for example.
Those who have handled the vaccine told RFE/RL that it carried a label from a state veterinary research institute in Pokrov, Russia -- part of the Russian Academy of Agricultural Science.
But the director of the Russian institute, Denis Kolbasov, insists that his researchers have confirmed the substance is not from Pokrov.
"We have not distributed the vaccine this year to [Uzbekistan or Kyrgyzstan]," he said. "The vaccine produced by us has been distributed across the Russian Federation and no complaints about its quality were ever made. The fact that the product in Uzbekistan is a fake became obvious as soon as we received samples.
"Neither the product's appearance nor its content correspond to our product. But I cannot say now if the content was the cause of the animals' deaths or any other reasons for what happened. I do not have any [test] results."
In Kyrgyzstan's Jalal-Abad Oblast, deputy police chief Tairbek Jorobekov says four criminal cases have been launched for violations of "veterinary regulations."
Talip Tashbolotov is among those detained for illegally selling the substance.
"Local people had been desperately asking for this smallpox vaccine," he told RFE/RL's Kyrgyz Service. "Finally, I decided to obtain 4,000 shots of the vaccine from a fellow [from Uzbekistan] whose name is Zianidin. About 3,300 of those shots were distributed [in Jalal-Abad Oblast] and used. In the places it was used, sheep died."
Authorities say another 1,600 sheep that received the vaccine in Jalal-Abad Oblast were being treated with antibiotics after becoming ill.
Jorobekov says a woman in Jalal-Abad has been charged with selling the vaccine at a shop in Kyrgyzstan without any medical education or veterinary training.
According to John Fitzgerald, the secretary of a U.K.-based alliance called "Responsible Use of Medicines in Agriculture,"
the reports are deeply troubling because suppliers of vaccines share responsibility with farmers to ensure that the medicine is properly administered.
"There are controls in the European Union on who is able to supply medicines," he said. "They are designed to make sure that there is the appropriate professional guidance available to a farmer when he is buying their medicines so that if the vet isn't going to administer the product then the farmer is aware of how the product should be used and when it should be used."
Jorobekov has also indicated that checkpoints have been set up to try to prevent tainted meat from being sold for human consumption in Kyrgyzstan.
"Special checkpoints have been established in the region to secure quarantine in order to prevent the dead sheep's meat, and still living but sick sheep, from being transported beyond the province's territory," he said. "The checkpoints are working around the clock."
But consumers in Kyrgyzstan are wary about tainted meat, which has loweed demand and caused the price of lamb to plummet at local markets.
Meanwhile, there are health risks in Uzbekistan from the possibility that tainted meat already may have made its way to markets.
That's because some Uzbek sheep farmers, fearing ruin if they lose their sheep, are slaughtering and selling their animals at the first sign of illness to minimize losses.
The huge loss of sheep could be more than Uzbekistan's fledgling private farmers can withstand.
With few market reforms in agriculture since the Soviet era, livestock are one of the only things Uzbekistan's farmers can privately own.
They must rent land from the state, and all supplies must be bought through a tightly controlled state-distribution system.
Ultimately, the loss of so many sheep could make Uzbekistan's sheep farmers the next casualty of the vaccine crisis.
Written and reported by Ron Synovitz, with additional reporting by RFE/RL Kyrgyz Service correspondent Torokul Doorov and Uzbek Service Director Alisher Siddikov