State vet finds likely cause of bird sickness

MAT-SU — A rash of chicken deaths in the Valley last fall was likely due to toxic levels of a chemical generally used to promote animal growth.

The sick and dead chickens started turning up in October 2010. Nancy Crowden of Willow said her birds became sick when she started feeding them Manna Pro feed bought at Walmart. When she switched the feed the birds got better. She talked to numerous other bird owners, all with very similar stories.

The feed was suspected from the start, but finding out exactly why the feed caused all this trouble was a laborious process.

“It was through a process of a lot of research, working with the toxicologists at Manna Pro and also in Idaho and the University of Washington to figure out what was going on,” said Alaska State Veterinarian Bob Gerlach.

The state started by checking for infectious diseases, then moved on to heavy metals and pesticides. They checked for salmonella, aflatoxin and anti-coagulant toxins. Every time they came up short.

“It wasn’t until the beginning of April that I thought that I would look at the ionophores in that feed to see if there was a problem with that,” he said.

Ionophores are a kind of chemical used both as growth promoters and, sometimes, as antibiotics.

“They help the transport of nutrients into the cells so the animals can more efficiently use the energy in the feed,” he said. “When it gets too much in there it allows the transport of certain salts into cells. Anytime you have an imbalance in the salt balance in an animal they’ll wind up getting sick.”

The results from the ionophore tests showed elevated levels of one particular chemical called monensin. Very elevated.

“Average concentration was approximately 10 times the value approved for use in poultry feed,” Gerlach wrote in his report.

Symptoms of a monensin overdose include lack of appetite, diarrhea, depression and muscle stiffness and weakness. The sick birds observed in flocks from Caswell to Anchorage had all of those signs.

So the monensin is the culprit, right?

Not so fast. As a scientist, Gerlach has a caveat. The monensin was found in the feed, but not in the birds, so it’s hard to say with certainty that monensin was definitely at fault.

But even if it was, there wouldn’t be any monensin in the birds.

“The monensin breaks down very quickly,” Gerlach said. His report notes that the chemical dissipates even in dead animals stored in freezers. “It’s very difficult to prove a case of toxicity with that because it is a very rapidly dissipating.”

Gerlach did seem happy, though, to have found what in all likelihood was the cause of the trouble. The state was “trying to help out the bird owners as well as trying to satisfy ourselves that we didn’t have some sort of problem.”

Contact Andrew Wellner at andrew.wellner@frontiersman.com or 352-2270.