Alerting vets, farmers and animal health advisers about the threat of lungworm in adult cattle and youngstock.
Farmers, animal health advisers and vets should be alert to the threat of lungworm (Dictyocaulus viviparous) in adult cattle and youngstock. It is a highly pathogenic and major productivity-limiting disease, causing severe losses in affected stock if untreated. Yet it can be difficult to diagnose at an early stage and often the disease is not spotted until there is a full-blown outbreak within the herd.
First season grazing cattle are the most susceptible to disease, not having had the chance to acquire any immunity prior to exposure. The impact on growth can be significant, with weight gains halved within 32 days after lungworm infection (1). Adult cows, however, are also at risk. They may have built up some immunity to lungworm as youngstock, either naturally or through vaccination, but this only lasts for six to 12 months. The most obvious impact of lungworm infection in adult cows is on milk yield, with reductions of between 15 and 20%, plus impaired fertility (2).
Early symptoms which can help identify an infection are:
Also known as ‘hoose’ or ‘husk’, outbreaks are typically seen in mid-late summer following periods of high rainfall and mild climatic conditions, but its occurrence is extremely unpredictable. Furthermore, an increasing number of cases of subclinical and clinical disease in adult cattle are being recognised, leading to productivity losses and severe disease. Planning a lungworm strategy throughout the grazing season is therefore the most effective means of preventing production loss and vital if the risk of disease is to be minimised. This preparation requires maintaining a careful balance between exposure and immunity, critical to the prevention of clinical husk.
At turnout, low levels of overwintered larvae are present on pasture grazed the previous year. These levels decline as the year progresses, decreasing significantly by early summer. Studies have shown, however, that as many as 10% of cows may be sub-clinical carriers of Dictyocaulus viviparus and thus contribute low numbers of larvae to this pasture contamination (3).
Once the infective larvae are consumed by grazing cattle, they penetrate the intestinal wall and migrate through lymphatics and blood vessels, reaching the lungs after approximately seven days. The larvae then mature as they travel through the airways and adult worms are present in the trachea approximately 25 days after infection.
Hatched larvae are then coughed up and swallowed before being passed out onto pasture in the faeces. A low dose infection with 200 larvae can lead to around 70 adult worms which can result in 2.5 million infective larvae on the pasture by 30 days after ingestion (4). This shows how heavy worm burdens, capable of causing severe clinical disease, can establish very quickly.
The survival and infectivity of larvae on the pasture is affected by a number of environmental factors. If, however, young or naïve cattle are exposed to high levels of larvae in the pasture without prior vaccination or sufficiently low level exposure to have developed immunity, clinical disease will be seen. In older animals which have an established level of immunity, low levels of larvae in the pasture will serve to boost this, but in the face of a heavy, uncontrolled challenge, outbreaks of severe potentially fatal disease can also be seen in adult cows.
A control strategy should be in place at turnout and throughout the summer. Vaccinating before the spring turnout is an effective method of preventing clinical disease in both youngstock and adult cows, although this immunity may wane as the grazing season progresses.
Strategic worming programmes are often implemented to control gastro-intestinal parasites in young cattle, and this approach will also provide protection against lungworm. In adult cattle targeted treatments are often used in response to the early signs of disease. This approach demands vigilance to ensure cattle are treated before outbreaks of severe disease and associated lung damage occur.
Many wormers used to treat cattle gutworm (Ostertagia ostertagii), such as EPRINEX® (eprinomectin) and IVOMEC® Classic (ivermectin), will also treat any lungworm present, so they can be used as part of a programme for lungworm control and for treating outbreaks by providing protection against reinfection for up to 28 days.
The effect of lungworm at its most extreme is death, but even in cases where this does not occur, lungworm can cause clinical disease of varying severity, significantly affecting the productivity of cattle. A planned strategy, vigilance and swift action will go a long way to reducing productivity losses throughout coming months.
Eprinex Pour-On for Beef and Dairy Cattle contains eprinomectin. Ivomec Classic Pour-on and Ivomec Classic Injection for Cattle and Sheep contain ivermectin. UK: POM-VPS. Further information available in the SPC or from Boehringer Ingelheim Animal Health UK Ltd, RG12 8YS, UK. UK Tel: 01344 746960 (sales) or 01344 746957 (technical), IE Tel: 01 291 3985 (all queries). Ivomec and Trodax are registered trademarks of the Boehringer Ingelheim Group. ©2019 Boehringer Ingelheim Animal Health UK Ltd. All rights reserved. Date of preparation: Apr 2019. AHD12102. Use Medicines Responsibly.
An educational service from Boehringer Ingelheim Animal Health UK Ltd (“BI”). Further information available from BI, RG12 8YS, UK. ©2019. All rights reserved. Date of preparation: January 2019. AHD 11982. Use Medicines Responsibly.
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1. Vercruysse, J. & Claerebout, E. (2001) Treatment vs non-treatment of helminth infections in cattle: defining the threshold. Veterinary Parasitology 98 ;195–214
2. Holzhauer, M., van Schaik, G., Saatkamp, HW., Ploeger, HW. (2011) Lungworm outbreaks in adult dairy cows: estimating economic losses and lessons to be learned. Veterinary Record 169, 494.
3. Eysker M, Classens EW, Lam TGM, Moons MJ, Pijpers A (1994). The prevalence of patent lungworm infection in herds of dairy cows in the Netherlands. Veterinary Parasitology 53 (3-4) 263-267
4. Vercruysse J, Janssens PG, Vercruysse J, Jansen J (1989) Dictyocaulosis. In: Worms and Worm Diseases pp 210-222 Samson Stafleu, Alphen aan den Rijn/Brussel
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