Respiratory disease in Youngstock
The cattle lungworm, Dictyocaulus viviparus, is a cause of serious respiratory disease in youngstock and adult cattle. Taking a pro-active approach to prevention, and rapidly treating outbreaks, can lessen the negative impact on productivity and reduce costs.
When does lungworm occur?
Infection with lungworm typically occurs in cattle from July onwards and, depending on climatic conditions, disease can be seen as late as November. Disease can cause significant losses in the dairy herd, due to reduced milk yield, reduced fertility rates, dead or culled animals and the cost of veterinary treatment.
Affected cows will also be more susceptible to other respiratory diseases. Sioned Timothy, technical manager at Boehringer Ingelheim Animal Health UK, offers five tips for managing lungworm in dairy cattle this grazing season.
1. Protect naive cattle
Youngstock and immunologically naive cattle are at greatest risk of respiratory disease caused by lungworm. Cattle gain immunity to lungworm infections through vaccination pre-turnout or low levels of natural exposure on pasture.
Worm control strategies should allow some exposure to occur, as this will trigger an immune response, but prevent a high lungworm challenge which could cause clinical disease.
Maintaining this balance between exposure and immunity is crucial, and the precise strategy should be developed for each individual farm with your vet or animal health adviser.
2. Pasture management
Warm, wet weather provides optimal conditions for lungworm. Populations of infective larvae can establish quickly on pasture, creating high challenge conditions for cattle.
It has been shown that, just 30 days after an animal has been infected with a low dose of 200 lungworm larvae, 2.5 million infected larvae can be shed onto the pasture (1), due to the parasite’s fast, direct lifecycle.
Rotating paddocks, strip grazing, and use of silage aftermath later in the season can be effective measures to reduce pasture larvae load and worm challenge faced by cattle.
3. Signs of disease
Lungworm should always be considered as a potential cause of coughing in grazing cattle. However, early infection can be difficult to identify and may only be recognised once a full outbreak occurs.
Lungworm can sometimes be confused with IBR, especially in older cattle, but affected animals will typically have a deep, harsh cough, and may exhibit laboured breathing. Severely affected cattle may extend their head and neck in an ‘air hunger’ position.
Affected cattle may rapidly lose condition and, if lactating, show a sudden drop in milk production. They may also be observed resting more frequently and eating and drinking less than normal.
Some animals may remain asymptomatic, with studies showing that up to 10% of cattle may be sub-clinical carriers of lungworm (2). These animals contribute low numbers of larvae to the pasture, but act as a reservoir of infectivity.
4. Treat disease rapidly
Where lungworm is confirmed, the whole herd or group must be treated, ideally with an anthelmintic which offers prolonged activity against Dictyocaulus viviparus.
Preventing immediate reinfection helps the animal’s lungs to recover and prevents further damage during the treatment phase. Anthelmintics with a zero-milk withhold period, such as those containing eprinomectin, can allow lactating cows to be treated for lungworm, without the loss of milk sales.
Severely affected cattle will require veterinary assessment and supportive treatment to relieve pain and inflammation and treat secondary infections.
5. Lungworm strategy
It is not too late to plan your approach to lungworm control this year. If you have already turned cattle out and have not vaccinated, talk to your vet or animal health adviser about strategic lungworm treatments and grazing management techniques to protect your cattle against lungworm and other productivity-limiting parasites.