The presence of lung worm, gastrointestinal round worm and liver fluke are the leading cause of production losses for the cattle industry. The parasites cause a reduction in feed intake and utilisation of nutrients, animals infected may show signs of diarrhoea, respiratory disease, ill thrift and death.
Cattle are infected with lung worm by ingesting Dictyocaulus viviparus larvae from pasture. Larvae pass through the animals gut and travel to the lungs, where they mature into adults, this process takes around 3 weeks. Once mature females start laying eggs, these eggs hatch producing young larvae that travel up the windpipe, are swallowed and pass through the gastrointestinal tract and are passed out in the faeces, infecting the pasture and increasing the parasite burden on the pasture. This cycle takes around 4 weeks to complete; one week for the larvae to mature on pasture and three weeks for larvae to mature into adults in the animal.
Prevention and Treatment
Cattle will develop natural immunity to lung worm, usually taking 1-2 month to develop. Continued exposure is needed to maintain immunity. Dairy calves and autumn born suckler calves are very susceptible to infection, therefore vaccination is recommended prior to turn out to develop immunity. Clinical signs of lungworm infection include respiratory signs, panting and harsh persistent cough. Severe infections may result in difficulty breathing and death. Lungworm infection should be considered when calves are showing signs of respiratory disease whilst at pasture. Diagnosis is through faecal testing, however negative results are possible in acute infections. Lungworm can be treated with most wormers used for gut worms in cattle.
The most common gastrointestinal parasites in the UK are Ostertagia ostertagi (Stomach worm) and Cooperia oncophora (Intestinal worm). The lifecycles are similar to that of lungworm but Ostertagia has the ability to arrest its development during winter and hibernate within the stomach wall. Towards the end of winter it continues to develop into adults worms. This can happen in any cattle, however young cattle particularly are at risk if they have been exposed to large numbers of arrested larvae in the autumn. This can cause severe weight loss and diarrhoea or death, this disease process is known as type II Ostertagiosis.
Prevention and Treatment
Type I Ostertagiosis is usually seen during late summer to early autumn and is caused by the ingestion of large number of infective larvae that mature into adult worms. Adult cattle are not as susceptible to disease as calves or yearlings if they have developed immunity from past exposure. Signs of disease are loss of apetite and watery green diarrhoea which may affect a large proportion of animals within a group in a short amount of time. Growing cattle can lose up to 10% body weight and have extended periods to reach slaughter weights, death is uncommon. Type I Ostertagiosis is best controlled by pasture managements. Grazing young cattle on pasture that has been grazed by young untreated cattle in the last 12 months poses the highest risk of infection, whereas new pastures or pasture grazed by adult cattle pose a lower risk. Worming treatment should be aimed at youngstock in their first and second grazing seasons, they can be treated early in the grazing season to prevent contamination of the pasture later in the year.
Type II Ostertagiosis is usually seen in late winter to spring depending on when the arrested larvae emerge. As the arrested larvae emerge together acute onset profuse diarrhoea is usually seen. Type II Ostertagiosis has a poor treatment response to worming treatment. The best way to prevent disease is to treat with preventative routine worming treatment at housing during autumn/winter and minimising the exposure of youngstock to large numbers of arrested larvae late in the grazing season.
Liver fluke is caused by the parasite Fasciola hepatica,it has a slightly different life cycle compared to that of lung and gut worms. Liver fluke requires the mud snail to complete its life cycle therefore is more abundant in wet marshy areas. Adult fluke live in the bile ducts of the liver, from here they lay eggs that pass into the gastrointestinal tract to be passed out in faeces. The eggs develop into the next stage that infects the mud snail. After 6 weeks of development in the snail the young fluke emerge from the snail on to pasture to be eaten by cattle. Once ingested by grazing cattle the young fluke migrate to the liver, which can cause a considerable amount of tissue damage. The mature fluke emerge into the bile duct and start producing eggs. Adult fluke can live within the liver for 1-2 years if not treated with an effective flukicide.
Suckler cows most commonly present with chronic weight loss. Spring calving cows are usually most severely affected due to the high metabolic demands of late pregnancy and marginal winter rations. Cows may produce weak calves and have lower milk yields, causing higher perinatal losses.
Fattening cattle will most commonly show signs of poor weight gains, severe infestations can lead to severe weight loss, brisket oedema and bottle jaw. UK slaughterhouses are reporting increasing numbers of liver condemnations due to fluke damage in 12 to 18 month-old fattening cattle where reduced liveweight gains were not suspected by producers due to low-moderate infestation levels.
Diagnosis of liver fluke can be from faecal samples but the sensitivity of faecal egg counts for liver fluke in cattle is 50%, counts may also be negative if animals are recently infected. There is also a blood test to check for liver fluke, however this may indicate prior exposure as well as an active infection.
Prevention and Treatment
Using flukicide as a preventative control measure should be discussed with your vet and be part of your herd health plan. There are a number of flukicide treatments available to use depending on which stage of the lifecycle is to be targeted. Treatment should be considered depending on the areas grazed and risk of the given year. In high risk areas, strategic treatments with flukicide is the most appropriate control measure. Winter housed cattle can be treated at housing with a single dose of an appropriate flukicide in accordance with the herd health plan. All purchased cattle should be treated with a flukicide before entering the herd.
The recovery of chronically infected cattle is slow following treatment with a flukicide. Improved nutrition of affected cattle is essential to restore body condition and production. Treated cattle should be moved to clean pastures wherever possible.
With the ever increasing uncertainty of beef prices in the UK, producers should ensure that production losses are kept to a minimum to maximise profits. The presence of parasites within a herd can cause considerable production losses, so control measures should be in place to ensure that maximum efficiency is achieved.
Do contact your local Westpoint practice if you would like advice on parasite prevention and treatment.
Written by Luke Williams BVetMed MRCVS