Even in the last decade we have seen an increase in certain diseases where we can link the incidence directly to warmer, wetter summers and milder winters. Perfect for extending the parasite and vector seasons for diseases spread by midges – like bluetongue; mud snails – like rumen fluke and direct infection – like haemonchus in sheep.

Most people would think Scotland is not directly affected by climate change, but it is already seeing direct results with the emergence of new diseases. With the best will in the world, unfortunately, these diseases are going to be a constant threat and likely to have a significant impact in years to come. Monitoring and surveillance going forward is key, with biosecurity, accurate diagnosis and responsible treatment the key to limit their economic impact.

Bluetongue

Once restricted to continental Europe, the industry is seeing cases of Bluetongue in the east of England, which has spread from the near continent by infected midges. Bluetongue is a notifiable disease affecting sheep, cattle and other ruminants like goats and camelids like llamas. Spread by the midge from April to November, the midge season is becoming longer with milder winters, which allows the infection of more animals and increases the risk of the disease spreading further from continental Europe.

Clinical signs vary between species and strain of bluetongue virus, however the latest strain to hit the UK is BTV-3. Sheep seem to be highly susceptible with high mortality rates up to 70% (average 2-30%). Infected animals carry the virus for up to two months in the blood stream, allowing further spread of the disease if conditions are right.

Clinical signs include ulcers in the mouth and nose, discharge from the eyes, nose and salivation, swelling of the lips, tongue, head and neck and the coronary band at the hoof. Other signs include fever, lameness, breathing problems, abortion and death.

Bluetongue is spread by midges that bite an infected animal and then the infected midge bites an uninfected susceptible animal. Once the midge has picked up the virus, it is infected for the rest of its life. Temperature, wind speed, direction and rain, together with proximity and density of neighbouring farms are significant factors affecting how quickly and how far infection may spread. Bluetongue is also spread through the movement of products like semen, embryos and infected animals.

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Disease control

Biosecurity: Importation of infected livestock from affected areas, both continental Europe and eastern England. Livestock keepers in high-risk areas can get free bluetongue testing for their animals. If bluetongue is confirmed to be circulating, APHA will place movement restrictions around infected premises.

Vaccination: Defra’s secretary of state has permitted the use of three unauthorized bluetongue serotype 3 (BTV-3) vaccines with the UK, subject to licensed. Available licenses will be targeted general licenses, initially in high risk areas, or specific licences which can be applied for through APHA.

BTV-3 vaccines do not prevent the disease, they reduce the clinical signs and infectiousness NOT prevent.

Trying to prevent exposure to midges has not limited the spread of the disease.

Be vigilant for the clinical signs of the disease but more importantly, be careful where you source your livestock. More information and latest updates on UK bluetongue advice are available on https://www.gov.uk/government/collections/bluetongue-information-and-guidance-for-livestock-keepers

Haemonchus

Haemonchus contortus is a stomach blood sucking worm affecting sheep. Historically affecting sheep in warmers climates on the continent and the south of England. The combination of climate change, poor biosecurity and drug resistance means we are starting to see more cases in Scotland, particularly this summer and autumn.

Different to other roundworms, haemonchus will affect sheep of any age and don’t present with a scour. The lifecycle is short and adult worms can lay thousands of eggs, so pasture can become contaminated very quickly. Acute infections, animals present with weakness or collapse, pale membranes of the eyes, rapid heart rate and breathing. These may present as sudden death. More chronic infections will show ill-thrift and weight-loss, pale and possible bottle-jaw, that you might also associate with liver fluke or Johnes.

Monitoring for this new disease in Scotland is important for early diagnosis and responsible treatments. Dung samples from animals with clinical signs can have huge worm egg counts, with definitive diagnosis at veterinary laboratories possible. Post-mortem examinations of dead animals is also important for diagnosis, with the presence of adult worms visible on the lining of the abomasum.

Biosecurity to prevent haemonchus coming onto the farm is important, with quarantine treatments for incoming stock – it is best to use narrow spectrum worms like closantel or nitroxinil, rather than reliance on longer acting avermectin products.

Rumen fluke

Another disease once restricted to the continent, cases of rumen fluke are common in Scotland. Now known to share the same intermediate host (the mud snail) as liver fluke, infections can be common on wet pastures with standing water.

Clinical signs include dullness, dehydration, rapid weight loss and severe watery scour. Also, low blood protein levels and bottle jaw. Left untreated, severely affected animals may die due to dehydration.

The most severe infections are seen when the rumen fluke larvae are migrating in the small intestines. Traditionally, rumen fluke was not considered to be a significant parasite in cattle, mainly because it was seen in very low numbers. Definitive diagnosis is important before treatment, as liver fluke infections may also be present. Eggs from adult rumen fluke can be found in the faeces but look similar to liver fluke.

Also, finding rumen fluke eggs in faeces may not be diagnostic as small numbers of rumen fluke do not cause disease. A diagnosis and treatment plan must be conducted with your veterinary surgeon. Importantly there is only one licensed product to treat rumen fluke, which is Oxyclozanide. This also kills adult liver fluke, but very importantly does not kill immature liver fluke, which may be highly significant. Most drugs that kill liver fluke do not kill rumen fluke.

Close monitoring is essential for all these diseases on farm, and for the best advice and treatment and control options, you should consult your own vet.