Stock feed contaminated with human faeces is being blamed for an outbreak of beef measles in northern NSW three years ago.
Twenty-six cattle were condemned and dozens more downgraded during the parasitic infection which affected just one feedlot at Tamworth.
DNA tests showed cystic lesions found in the cattle during routine meat inspections at abattoirs in NSW and Queensland in 2010 were caused by a human parasite known as Taenia saginata, the beef tapeworm.
David Jenkins, from the School of Animal and Veterinary Sciences at Charles Sturt University, and his colleagues were enlisted to explore just how human poo end up in an imported livestock feed supplement.
"We're talking about a seriously large tapeworm; about four metres long. It lives in the intestine in people and when they go to the toilet, they pass the eggs out," he said.
"In situations where there's defecation onto the ground because people don't have toilets, the eggs get spread around on the pasture, cattle graze, and eat the eggs. Then eggs then hatch inside them and the larval stage pass into the muscles and form a little cystic stage which, if it's eaten as raw meat or meat that's only been lightly cooked, the human contracts the infection through eating this poorly cooked beef that is infected with these cysts."
Months of investigation narrowed down the source of the infection to Papua New Guinea and a batch of copra meal, a widely used protein supplement made from coconut.
"Other batches come in from the islands around Australia. My colleague, Dr Graeme Brown, has been to a number of these islands and found the human faeces contaminating the environment is very high."
The researchers found it curious that the Tamworth outbreak was isolated.
"What we suspect happened is that someone in the feedmill was desperate to go to the toilet. And then this piece of faeces landed in the desiccated coconut and became like a faecal lamington and then slid through the coconut as they filled the 20-kilo bags.
"Just by chance, it went to a cow property. Had it gone to a sheep or horse place, you'd have never known because these animals aren't susceptible to this parasite."
Dr Jenkins has called for all imported copra meal to be sterilised to destroy contaminating pathogens, such as the eggs of the beef tapeworm.
"We've recommended that copra meal should be either heat treated or deep frozen. Both processes will kill the cysts, but it's a terribly expensive thing to do. But people don't like tapeworms so I think it's worth considering."
District livestock officer Alastair Rayner, from the NSW Department of Primary Industries, says the incident highlights the importance of vendor declarations and keeping effective records.
"When something like this happens, being able to go back and isolate the feed, or the environment, or the location of where the stock has come from is essential in nailing the problem very quickly and preventing it from happening further."