A livestock parasite that is hard to control and even harder to detect is causing headaches for cattle, sheep and cervid producers in parts of Alberta and Manitoba.
The liver fluke is an insidious parasite that infests the liver of host animals. Fluke infection is rarely a concern for livestock producers in most parts of the Prairies, but hot spots are emerging and veterinarians urge producers to watch for symptoms.
“I’ve been getting more and more reports from practitioners about liver fluke infections in Alberta and … I’ve heard reports of a similar situation in parts of southern Manitoba,” said Murray Kennedy, a livestock parasite expert with Alberta Agriculture.
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“Especially in the area around Drayton Valley, (Alta.), they seem to be fairly common and spreading.”
Liver flukes are difficult to control because the health problems they create are often misdiagnosed.
In general, heavily infested animals are thin and sickly looking. Weight gain is abnormally slow and milk production is poor.
The parasites can affect sheep, goats and cattle, as well as farmed elk and deer, but mortalities in cattle and elk are rare unless infestation is severe.
Deaths in sheep and goats are more common.
According to Kennedy, liver fluke infestations often go undetected until infected animals are sent to slaughter. When the liver is removed, the flukes appear as black or dark red lesions on the liver’s surface.
Infected livers are discarded but the rest of the carcass is unaffected, although conditioning at the time of slaughter is usually poor and muscle cuts are poorly marbled.
The more serious implications associated with fluke infection are the economic losses caused by poor weight gain and inefficient feed conversion.
It is hard to calculate the financial losses associated with fluke infection because a timely diagnosis is difficult and other factors may influence weight gain.
The life cycle of the liver fluke is relatively complex compared to most livestock parasites.
The eggs develop in water, hatch and release larvae that infect certain types of snails.
After attaching to the snails, the larvae develop and multiply rapidly, eventually producing new larvae that leave the host and attach themselves to aquatic plants.
Cattle ingest the larvae by drinking contaminated water.
Once the larvae are ingested, they migrate through the intestinal wall and into the liver. There, they complete their life cycle by excreting eggs that pass through the bile ducts and into the intestine. New eggs are excreted in the feces.
Control can be challenging once liver flukes become established.
Standing water and snail hosts are required for the fluke to complete its life cycle but if those conditions are met infections can be common.
Infected cattle spread the parasite by defecating in water or marshy areas. Moving infected cattle to a new range can also spread the parasite.
Brent Wagner, a parasite expert with the Western College of Veterinary Medicine in Saskatoon, said fluke infestations are rare in areas where standing water is limited and rangelands are generally dry.
“We really don’t see it much in Saskatchewan,” he said.
“As parasites go, it’s got a fairly complex life cycle so everything’s got to be just right for it to spread and reproduce.”
The easiest way to monitor regional infestation is to survey the condition of beef livers at local slaughter plants, Kennedy said.
If cases are common in an area and animal conditions are symptomatic of fluke infestation, producers can collect fecal samples of individual animals to determine if fluke eggs are present.
Control treatments using triclabendazole or albendazole can eliminate flukes in an infected animal but producers should consult a veterinarian for information on dosages, withdrawal times and other restrictions.
Livestock producers can also limit cattle access to marshy areas and discourage watering in ponds and sloughs.
