Lungworm, otherwise known as “Husk” is very common in Northern Ireland. It is caused by the parasite Dictyocaulus viviparus and can lead to serious lung disease. It is estimated that the losses associated with lungworm in growing cattle can be up to £50-£100 per head. In adult lactating cattle the condition can lead to losses in milk production up to £3/cow/day.
According to the All-Island Animal Disease Surveillance reports 2023, AFBI reported that just over 12% of all pneumonia-related deaths in cattle were caused by Lungworm (D, viviparus). AFBI also reported, that of all faecal samples submitted for lungworm testing, 25% came back positive for lungworm. In Northern Ireland, the peak incidence of disease is seen from August to October (see Table 1 below).
Reference: 2023 All-Island Animal Disease Surveillance Report, chapter 28: Bovine Parasites, AFBI; Bob Hannah, Veterinary Research Officer, Stormont Veterinary Laboratory
Clinical Signs:
The clinical signs can be variable and may range from mild to severe. They are as follows:
- “Air hunger stance” – outstretched neck and open mouth
- Coughing
- Weight loss
- Increased respiratory rate and respiratory distress
- Reduced milk yields in adult stock
Risk:
- Wet, warm summers (common in Northern Ireland) encourage the development of lungworm on pasture
- Heavy stocking density on grazing fields also contributes to a higher risk of lungworm disease developing in grazing stock
- First grazing youngstock are most vulnerable, as they have not had previous exposure and therefore have low or no immunity.
Note that some adult stock can still be vulnerable to the disease due to overuse of wormers throughout their first grazing season.
Life cycle:
Photo Source – NADIS Forecasts
The nature of the lifecycle of lungworm, means that infected animals may not have positive dung tests for as long as 25-60 days post-infection. This is because the eggs are produced in the lungs rather than the intestinal tract of infected cattle and the larvae are excreted directly onto pasture in the faeces. This means, clinical signs are more useful in the diagnosis of the disease, rather than faecal tests.
Prognosis:
The prognosis for heavily infected cattle is usually poor and infection often leads to death. Caution must be taken when attempting to treat heavy infestations as some worming products can cause an allergic reaction to the dead worms within the lungs leading to sudden death. Group 2 (Levamisole), yellow wormers are the safest option to treat a suspected case of lungworm as they work by paralysing the nerves in the worm first, reducing the risk of allergic reactions in the lungs.
Control Strategy
Two strategies must be employed for grazing cattle to ensure that lungworm doesn’t cause issues throughout the grazing season:-
1. Suppress Infection
- Treat stock throughout the season, particularly in late summer and early autumn risk periods, with an effective wormer to ensure lungworm infection remains low
- Note that if wormers are overused, cattle have no immunity to lungworm and may still be susceptible to infection in their next grazing season
- The table below (Table 2) outlines the various active agents which may be used and their respective duration of protection against lungworm.
Table 2: Worming agents effective against lungworm
| Active Ingredient | Application Method | Duration of Protection |
| Doramectin | Injection | 35 days |
| Pour-On | 42 days | |
| Eprinomectin | Pour-On | 28 days |
| Ivermectin | Injection | 28 days |
| Pour-On | 28 days | |
| Moxidectin | Injection 10% | 120 days |
| Pour-On | 42 days | |
| Levamisole | Oral | No prolonged action |
| Benzimidazole | Oral | No prolonged action |
Quarantine and Treat all purchased stock
- If purchasing stock throughout the grazing season, there is a risk that you will “buy-in” lungworm infection. All incoming livestock should be quarantined and treated appropriately to mitigate the risk of incoming lungworm infection which could contaminate grazed pasture.
2. Induce Immunity
Vaccinate with Huskvac – an oral vaccination suitable for calves over 3 months of age. Vaccine schedule below:
Lungworm is a complex parasite with deadly consequences. Speak to our Registered Animal Medicine Advisors in your local Fane Valley Store for more help and guidance to ensure Lungworm is not a problem for your cattle this summer.
