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Eamon O'Connell: Weather conditions have created the perfect storm for a lungworm outbreak

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Growing problem: A sharp increase in lungworm at pasture combined with decreased immunity has led to a massive rise in lungworm cases

Growing problem: A sharp increase in lungworm at pasture combined with decreased immunity has led to a massive rise in lungworm cases

Growing problem: A sharp increase in lungworm at pasture combined with decreased immunity has led to a massive rise in lungworm cases

"Cough etiquette" is one of the phrases that has defined 2020 for me so far. Not a day goes by that I don't hear about how coughing into my elbow will help minimise the risk of spread of Covid 19.

As the country returns to some semblance of normality, I was starting to enjoy not hearing about coughing at every hands turn. However, this week, coughing is back with a bang - not in people this time, but in our cows.

A number of farmers in recent days have complained of hearing cows coughing, either on the way in from pasture or when standing at the back of the parlour waiting to be milked. The cough is a dry, husky type cough. There is often an accompanying drop in milk yield. Fertility can also be affected. This is typical of a lungworm infestation.

Lungworm seems to be becoming more and more of a problem in recent years.

Lungworm love wet and warm weather, which is exactly what we have had over the past two weeks.

Unfortunately, the ideal conditions for grass growth are also ideal for lungworm. The dung pats at pasture are full of larvae which are spread onto the grass when rain falls. This has led to a massive increase in lungworm being ingested by cows.

The spell of dry weather that we had in late May and June ensured that very little lungworm was in the pasture at that time. Due to the fact that the cow's immune system was not exposed to lungworm, immunity decreased.

A sharp increase in lungworm at pasture combined with decreased immunity has created the perfect storm for lungworm this July.

Tight grazing patterns have served only to exacerbate the problem. Some herds of cows are returning to pasture every 17-18 days. This quickly leads to massive burdens of lungworm larvae. Topping, although necessary for better grass quality, has the disadvantage of spreading the dung-pats thereby distributing lungworm larvae all over the pasture.

A lungworm problem in cows starts back at the calf stage. The calf worming protocol, or lack thereof, can mean that calves gain little or no immunity in their first year. There is a tendency to dose calves whenever is convenient, rather than only when necessary.

Calves need to exposure to lungworm to develop immunity. A dosing strategy should be drawn up in conjunction with your vet to ensure immunity to lungworm can be developed in your replacement stock.

Weather conditions, pasture type, faecal samples and handling facilities will all be taken into account when formulating a plan.

The aim is for replacement stock to enter the grazing herd with a strong level of immunity. There is a vaccine available against lungworm, which is playing an increasing role in the development and maintenance of immunity every year in dairy herds.

It seems on first glance that there are a number of zero milk withdrawal products on the market for the treatment of lungworm in cows. There are various different pour-ons and also an injectable formulation.

At this time of year there seems to be some zero milk withdrawal wormer on offer in every farm store every week. The grim reality is that, despite all the product names, the active ingredient is the same - eprinomectin. There is no other option for dosing dairy cows during the grazing season. Eprinomectin is all we have. If resistance develops to eprinomectin, that's it.

We should be using zero milk withdrawal products very, very carefully to ensure we have them in the future. Don't buy and use a product because it's on special offer. Only use it when it's completely necessary and in consultation with your vet.

When lungworm is suspected, we need to confirm that it is present and also, rule out other causes of coughing.

Swabs can be taken to check for viruses such as IBR or PI3. A bulk milk sample can be analysed for antibodies to worms but shouldn't be used on its own to confirm. A lung washes (also known as a BAL) can be performed by your vet. A small volume of saline is flushed into the lungs and sucked back out. In severe cases, adult lungworm can be seen in the fluid. The fluid can be examined under a microscope to see lungworm larvae.

It is also worth noting that, after dosing coughing cow, the coughing may continue for a number of weeks due to irritation in the airways. Success of treatment should be judged by a combination of an increase in milk yield and a gradual decrease in the incidence of coughing. Reinfection can occur so continuous monitoring should be carried out.

Hopefully, as the summer goes on, we will hear less and less coughing, across all species.

Eamon O'Connell is a vet with the Summerhill Veterinary Clinic, Nenagh, Co Tipperary

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