Ask the Vet

Liver Flukes Problem Expanding Across US

Liver flukes are becoming more common across the country but often are not found until an animal is slaughtered or dies from being infected. (DTN/Progressive Farmer file photo by Pamela Smith)

READER QUESTION:

A neighbor of ours fed out a steer, and at slaughter, the liver was badly infected with liver flukes, and it died. I have never heard of that in our area, and I don't know anything about them. Do I need to be worried? What do I need to do to protect my cattle?

DR. MCMILLAN'S ANSWER:

Liver flukes were once considered to be a parasite of the Gulf Coast and the Pacific Northwest, but with increased cattle movement across the country and with warmer weather, flukes are rapidly expanding their range.

Flukes have a unique life cycle. The adult flukes live in the liver and lay eggs that are passed out in the manure. They require water to complete their life cycle. In really dry conditions, the eggs can live for up to a year. But if enough moisture is present, the eggs hatch into larvae (miracidia) and swim off in search of the common mud snail. They enter the snail, and after a period of time produce another larval stage (cercariae) that swim to vegetation and attach as the encysted larval stage (metacercaria). Cattle are infected when they eat infected grass or drink infected water. Inside the intestines of the cow, juvenile flukes are released and begin a migration to the liver.

The adult fluke is about the size of a large thumbnail. They have a sharp, spiny exoskeleton and migrate through the liver and bile duct, causing severe damage. Common signs can include poor body condition, anemia, bottle jaw, diarrhea, reduced milk yields, reduced fertility, weak calves and even death. Condemned livers is a major loss for feedlots, but the largest loss may be on the farm in lost production.

Unfortunately, these are similar signs to other internal parasites, but most dewormers are not effective on flukes. So, diagnosis of fluke infection is very important.

Many times, fluke infection is found at necropsy or at slaughter. Your veterinarian can diagnose fluke infection by finding fluke eggs on a fecal sedimentation test. There are also blood tests to check for antibodies to flukes. Ultrasound can also be used to find liver damage, and the liver can also be biopsied.

Treatment of flukes can be challenging since there is no product approved in the U.S. that kills the juvenile stages that cause much of the damage. The timing of deworming is critical since the earliest we can start killing them is eight to 12 weeks after infection. Albendazole (Valbazen) drench and products containing clorsulon (Ivomec Plus and generics) are used to treat flukes. Please check with your veterinarian on when to deworm, how often and which product is best for your operation.

Because of this issue, management again becomes critical. Since there is no way to effectively kill snails, keep cattle off wet areas or improve drainage to avoid standing water to reduce the exposure to the snail habitat.

Unfortunately, if you do not have flukes in your area, they may be headed your way soon, so be on the lookout.

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Editor's Note: Please contact your veterinarian with questions about the health of your herd or other animals. Every operation is unique, and the information in this column does not pertain to all situations. This is not intended as medical advice but is purely for informational purposes. Email Dr. Ken McMillan at vet@dtn.com.