ST. CLOUD, Minn. — In the summer, beef producers have a laundry list of parasites to watch out for. Some parasites have obvious symptoms and can be easily treated. Others are more difficult to manage. Liver flukes are caused by the parasite Fasciola hepatica. Fluke eggs are passed in the feces of the animal, and they hatch into motile miracidia. The miracidia must find a host within three hours of hatching. The typical host is a snail. The infected snails will eventually shed cercaria, which are motile and will attach themselves to surfaces, such as grass blades, where they become the infective metacercariae. These are then reingested by the final host, completing the life cycle. Once inside cattle, metacercariae migrate through the gut wall, cross the peritoneum and penetrate the liver capsule and bile ducts.
Symptoms associated with liver flukes include reduced weight gain, reduced milk yields, reduced fertility, anemia, and diarrhea. However, a liver fluke infestation is typically subclinical, so you may not even know you have liver flukes unless you have a post-mortem completed or you receive feedback from the packing plant about condemned livers. Therefore, producers should look at post-mortem examination or carcass information from the packing plant as an essential diagnostic tool.
Condemnation of the liver at the packing plant can be caused by just one liver fluke. One would expect that most economic losses would be due to liver condemnation at slaughter. However, there are greater hidden financial losses experienced by beef producers once their cattle become infected with liver flukes. Reduced average daily gain, lower feed conversion, reduced milk production, and lower weaning weights are the most common productivity losses. In addition, several feedlot studies in feeder cattle infected with even low levels of liver flukes indicate that rate of gain can be significantly reduced. The financial bottom line is that liver flukes can be responsible for hidden economic losses in the beef cattle industry.
Taking prevention measures now can help avoid losses down the road. Look at reducing exposure to wet, marshy areas–where the larvae thrive best and where you are most likely to have snails. Next, look at deworming programs with your veterinarian. Two oral dewormers are available that are effective against liver flukes: clorsulon and albendazol. There is also an injectable dewormer, which is a combination of ivermectin and clorsulon. All the drugs have advantages and disadvantages in terms of cost, ease of administration, withdrawal times, and effectiveness. Consult your veterinarian to be certain which product will work best for your operation.
— Emily Wilmes, University of Minnesota Extension
For more news from Minnesota, click here.