Keep a close watch on liver fluke this autumn

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Kwakkeel kan ’n aanduiding van onder andere kroniese lewerslakbesmetting wees. (Foto: Johan van Rensburg)

Estimated reading time: 4 minutes

Dr Paul Reynolds, a veterinarian at Warden Veterinary Clinic, describes liver fluke as a parasitic worm that causes serious economic losses. Livestock producers, he says, must contend with two types of liver fluke – common liver fluke and giant liver fluke worm.

Better parasite control starts with lambs and calves.

Wetlands, springs, cultivated pastures, rain and heat all create an ideal breeding ground for this parasite. These parasites occur throughout South Africa, with their numbers rising in especially late summer and autumn. Liver flukes depend on freshwater snails as intermediate hosts to complete their life cycle. The presence of freshwater snails therefore usually spells disaster for livestock herds and flocks.

Adult and immature liver flukes are harmful to both humans and animals. Adult flukes can lead to chronic production losses or acute mortalities in livestock, whereas migrating, immature fluke larvae cause infestations in livestock when ingested with plants and water.

Signs of infestation

“The signs of infestation vary, depending on how heavy the load is and how long animals have been exposed to the flukes,” says Dr Reynolds. “Cattle can build up some resistance to liver fluke, but it depends on the load of freshwater snails or liver flukes in the infested area.”

In the case of chronic, light infestation animals can develop bottlejaw and a coarse coat. Sudden death accompanied by abdominal bleeding can occur, and infested cows will typically produce less milk. In acute cases, where the liver fluke load is high, sudden death can occur. This is due to the parasite migrating through the organs and blood vessels, causing bleeding, or due to shock brought on by the parasite’s presence in the animal’s body.

In sub-acute cases, where animals are exposed to a high load for a few weeks, liver damage can occur due to the immature liver flukes migrating through the body. This may lead to protein deficiencies, reduced blood clotting factors and a hormonal imbalance, as well as poor conception and animals that fail to enter oestrus.

In chronic cases, where animals are exposed to a light load for several weeks, treatment is too late. The condition causes liver damage and protein deficiencies, leading to condition loss and substandard performance in animals. Their coat may also appear coarse, and once this stage is reached, treatment is no longer effective.

Dr Reynolds notes that the liver is one of the most vital organs as it regulates hormone functions, blood and proteins. “A damaged liver can impair growth hormones and oestrus cycles while at times also causing permanent damage.

“An ox that typically does not gain weight, even with the right supplementation and treatment in the kraal, is a good example. Unfortunately, a post-mortem is generally not performed on such an animal because it might only have been deemed ‘sick’.”

A handy prevention strategy

It is possible to control infestation naturally by applying crop rotation and good management, especially in wet areas. However, if possible, rather avoid these areas. Another handy precautionary measure is to welcome wild geese into the area, as they eat snails.

https://www.agriorbit.com/a-worm-strategy-that-counters-resistance/

“Dosing helps to a large extent to limit adult and immature liver fluke damage,” says Dr Reynolds. “To determine whether you have a liver fluke problem in your herd or flock, you can take manure samples to your local veterinarian and jointly decide on an appropriate dosing or spraying programme.

“Remember, if no liver fluke eggs were detected in the manure sample, there may still be a problem. It could simply be a case where no adult liver flukes have yet laid eggs at that point. A manure sample test cannot detect immature liver flukes, which can cause problems at a later stage; however, it is possible to determine all stages of infestation by performing a blood test to detect antibodies in the animal.”

Strategic treatment

Preventive treatment includes various dosing and spraying agents, with most products killing only the adults, while the immature fluke is left to migrate through the animal’s body where it damages the liver and other organs.

Treatment for severe infestation is aimed at supporting the liver and includes a protein supplement. It is recommended that immature liver flukes be treated strategically and that producers use products that address both the adult and immature stages of liver fluke.

Lastly, Dr Reynolds notes that it would be doubly beneficial for livestock producers to consult with their veterinarian. Your herd or flock veterinarian will be able to offer constructive input to stop liver fluke in its tracks.

For more information, contact Dr Paul Reynolds on
082 587 7607, 071 438 9277 or wardendier@gmail.com.

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