Sheep farmers in Scotland, North Wales and North West England should prepare for high levels of liver fluke disease this autumn, while cattle farmers across the UK must remain alert to lungworm disease (husk) and urgently assess any cows observed coughing, according to the NADIS September Parasite Forecast and Merial Animal Health.
“While 2015 saw high liver fluke challenge in sheep flocks, the threat in 2016 may prove even higher. Fluke eggs passed onto grazing last winter will have developed through the mud snail host into the infective cyst stage meaning pasture contamination could be very high in some areas this autumn,” warns Sioned Timothy, Veterinary Advisor for Merial Animal Health.
“It’s almost certain that preventative treatments will be necessary during early autumn in Scotland and highly likely in North West England and North Wales to prevent acute liver fluke disease in at-risk flocks. Triclabendazole is the only product that is effective against early immature fluke and is the mainstay for preventing acute and sub-acute liver fluke disease at this time of year. Alternative flukicides such as those containing nitroxynil (Trodax) or closantel are advised for later treatments, and especially where triclabendazole resistance is suspected.”
As with all veterinary medicines, accurate dosing according to weight is vital. Whilst under-dosing will reduce the efficacy of flukicides and potentially increase selection for resistance, particular care should be taken not to overdose or accidentally drench sheep twice as this will increase the risk of toxicity. Farmers should weigh a representative sample from the flock and dose according to this weight, adjusting for over or under-weight individuals.
If triclabendazole resistance is suspected, sheep farmers should consult their veterinary surgeon for advice. Tests can be performed which monitor the efficacy of the drug two to three weeks after dosing. If resistance is identified, an alternative plan can then be put in place.
Managing grazing by moving sheep onto pasture that is better-drained and less contaminated with fluke eggs can help reduce the risk of infection.
As well as planning fluke control, farmers should ensure all lambs are fully vaccinated against clostridial diseases since migrating immature flukes can predispose lambs to ‘black disease’.
“Lambs grazing pastures heavily contaminated with worm larvae may also be at risk of clinical parasitic gastroenteritis (PGE) with mild wet weather and high stocking densities exacerbating the challenge facing lambs this year,” advises Ms Timothy. “Regular monitoring using pooled faecal egg counts (FECs) or liveweight gains will help assess the need to dose for gastrointestinal worms.”
September is a key time for new breeding stock to be brought onto the farm. Quarantine of all bought-in stock is essential to prevent the spread of parasites to the home flock, including resistant strains of gastrointestinal worms and liver fluke. Veterinary advice should be sought to determine the most appropriate approach, and which products to use. Sheep should be confined for 24 to 48 hours after treatment and then turned out onto pasture recently grazed by sheep. New stock should be isolated from the home flock for at least 30 days and monitored closely for signs of disease.
A major parasite threat facing cattle this autumn is lungworm, with youngstock and unvaccinated cattle of all ages at high risk. However, even animals vaccinated against lungworm before turnout may still face challenge late in the season as immune protection wanes.
Lungworm eggs will not be present in the faeces until larvae develop into egg-laying adults, so faecal worm egg counts are not a reliable indicator of early infection. Diagnosis is usually based on clinical signs which include laboured breathing and coughing. Any cows exhibiting such signs should immediately be assessed to determine the likely cause of disease.
Once husk has been diagnosed, immediate treatment of all cattle in the group is required to clear the infection and protect productivity.
Youngstock may also face challenge from gastrointestinal worms, particularly those in their second grazing season which have not been subject to targeted worming programmes. Type 1 ostertagiosis can strike suddenly, affecting a large percentage of the group with profuse diarrhoea and rapid weight loss. Treatment with an appropriate anthelmintic is required to reduce productivity losses from reduced weight gain.
Many wormers used to treat gastrointestinal worms (such as Ostertagia ostertagi) will also treat lungworm. Advice on the most appropriate product to treat an outbreak of lungworm or to control gastrointestinal worms should be sought from a vet or SQP. Options include products containing ivermectin (Ivomec Classic) in beef cattle or those containing eprinomectin (EPRINEX) with zero milk withhold, in dairy cattle.
“Housing is a good time to appraise the effectiveness of parasite control measures this season and think about planning for next year, in conjunction with a veterinary surgeon or animal health adviser,” advises Ms Timothy. “In the meantime, preventing parasitic disease over winter and ensuring optimal production is an important element of protecting beef and dairy profitability.”