Lungworm
Lungworm (or Husk) is caused by the parasitic worm Dictyocaulus viviparous which can infect cattle of all ages and breeds which have not been able to build immunity through natural exposure or vaccination.
Lungworm is now well established on grazing land across the UK which means that planning lungworm control strategies against this widespread disease is important for all farmers.
Outbreaks of lungworm can be unpredictable and so vaccination before turnout protects a herd from walking into a potential minefield.
Lungworm seasonality
Average monthly distribution of lungworm outbreaks:
Lungworm lifecycle
D. viviparous has a direct lifecycle which is described below:
How is disease spread?
The spread of disease is aided by the fungi Pilobolus. This fungus thrives in warm and wet conditions, growing on the surface of dung and the lungworm larvae attach to these spores. The spores explode and spread the larvae up to 3 metres on the pasture from the faeces.
Photograph kindly supplied by Catherine McLeonard
Clinical signs of lungworm
The clinical signs of lungworm are most frequently seen in first year grazing cattle (but cattle of any age can be affected) and can include:1,2
Impact of Lungworm
Lungworm infection causes reduced growth rates and decreased lifetime productivity in beef and dairy cattle.
Lungworm Prevention
Cattle can produce an immune response to lungworm larvae and adult worms. This immunity can wane after a few months unless cattle are exposed to low-level contamination on the pasture.
Vaccination is the most predictable method of building herd immunity to protect against lungworm.
Cattle can be vaccinated for lungworm by giving an oral vaccine containing irradiated lungworm larvae (L3) which stimulate immunity. Cattle need to be turned out onto low level infected pasture no sooner than 2 weeks after completing the vaccination course which allows them to boost their immunity naturally.
Vaccination provides a solid base of immunity at the start of the season, which is maintained in a controlled way through grazing low-level contaminated pasture.4
Worming and Vaccination Integration
If you are continuously worming for gut worms this will also remove lungworm and not allow for natural immunity to build up, therefore cattle are at risk of lungworm infection when the activity of the wormer ends.
Wormer Resistance
There is a risk of promoting resistance with the ongoing use of long-acting anthelmintics and relying on wormers alone does not allow the animal to develop its own natural immunity.5,6,7
Therefore, it is important to discuss with your vet or animal health advisor the appropriate use of anthelmintics; taking into account gut worm control, incorporating vaccination and also grazing management to create a robust approach to parasite control. For further information please refer to Control Of Worms Sustainably (COWS) via www.cattleparasites.org.uk
References
1. Cattleparasites.org.uk. (2014) Control of lungworm in cattle. http://www.cattleparasites.org.uk/app/uploads/2018/04/Control-of-lungworm-in-cattle.pdf [Accessed Jun 2018].
2. Elsheikha H. (2017) Endoparasites in cattle: studies and diagnostics. Vet Times Online.
3 Holzhauer M. et al. (2011) Lungworm outbreaks in adult dairy cows: estimating economic losses and lessons to be learned. Veterinary Record. 169:494.
4. McLeonard C. & van Dijk J. (2017) Controlling lungworm disease (husk) in dairy cattle. In Practice, 39(9). 408-419.
5. Forbes A. (2018) Lungworm in cattle: epidemiology, pathology and immunobiology & Lungworm in cattle: treatment and control. Livestock, 23(2) & 23 (3).
6. McNulty S. et al. (2016) Dictyocaulus viviparus genome, variome and transcriptome elucidate lungworm biology and support future intervention. Sci. Rep. 6.
7. Molento M. et al. (2006) Suppressive treatment of abamectin against Dictyocaulus viviparus and the occurrence of resistance in fi rst-grazing-season calves. Veterinary Parasitology 141. 373–376.
