RED MITE is a blood-sucking parasite that, if allowed to reproduce uncontrolled, can have a severe impact on the health and productivity of birds on a poultry farm.
They are primarily a problem in laying hen and broiler breeder systems, but the set-up of modern free-range egg farms can present particular challenges.
Even relatively small populations can cause issues, and it is thought that red mite may serve as a disease vector, potentially spreading unwelcome viruses and bacteria.
And as numbers increase, a range of behavioural and ultimately physical effects detrimental to health can emerge.
Birds irritated by high populations of red mite can have increased head-scratching and grooming, which can contribute to lower weight gain and egg production. At night, when mite typically feed, birds will appear restless – and unrested birds are more prone to health challenges and less likely to eat.
They can also become anaemic – all factors that may raise mortality levels.
It’s little surprise that these negative consequences can emerge; studies have suggested that a heavily infested hen can lose up to 5% of its blood overnight as mites feed.
The red mite
To understand how the red mite can become a problem for commercial poultry farms, it’s worth understanding how they evolved alongside chickens, according to Dave Hodson, of Rosehill Poultry.
“The parasite originally adapted to live in the nests of wild birds,” Mr Hodson says. They would activate when nests were occupied, feed and reproduce, before becoming dormant and hibernating when birds left nests empty.
This lifecycle is useful for surviving in an environment where hosts are only present seasonally; in fact, it is thought they can remain dormant for up to 18 months.
But in a modern poultry unit, where birds are constantly present in high numbers, it allows for explosive population growth.
Studies have shown that a female red mite can go from hatching to reaching maturity in as little as seven days and lay about 50 eggs over her lifetime – demonstrating how vital keeping on top of populations is.
Modern free-range farms are an excellent habitat for mite, adds Mr Hodson. Muck belts remove manure, keeping ammonia levels down; ventilation is generally better and sheds warmer – all helping to boost populations.
Understanding red mite population levels is a crucial element of control – and is essential if a pharmaceutical product is to be used, Mr Hodson says.
A straightforward way to assess a shed is to visually inspect cracks and crevices where the pest hides during the day. Removable parts of equipment like the clips of feed tracks can be an excellent place to look.
Eggs with blood spots are another sign that red mite populations may be on the up.
Formally testing is possible using the Avivet trapping system, which is often supplied in the UK by MSD.
Small cardboard tubes are placed around the shed, often under perches. After 48 hours, they are removed and weighed using extremely accurate scales – the change in weight will indicate mite populations.
Farmers should start with a thorough clean of sheds during turnaround.
There are, broadly speaking, three ways to treat red mite on a poultry farm while birds are in-situ – a spray-based red mite treatment, using the water-based pharmaceutical Exzolt to kill mite or another waterline-based treatment that can discourage feeding.
While good for spot treatments, an effective clearing of an entire shed using a spray-based product is a time-consuming task, that requires a lot of product, Mr Hodson says.
“From our work, we have found a 16,000-bird system needs 100-160l of product sprayed to penetrate dust and saturate the system effectively.
“This takes about 3-5 hours with two operators using Birchmeier knapsack sprayers fitted with flat fan nozzles,” he adds.
It must also be repeated seven-days later, as eggs unaffected by the first spray will have hatched.
Rosehill recommends Dergall, which can be sprayed onto birds and kills both red mite and their eggs. It also has antibacterial properties.
Time needed: 10 hours.
Spray treatment for red mite
- Initial Spray
This will take two operatives 3-5 hours and require betweent 100-160l of substance
- Second spray
Seven days’ later, the first step must be repeated to clear any eggs that have subsequently hatched
Pharmaceutical water-based treatment
Exzolt, from MSD, is an acaricide that enters hens’ bloodstreams via the gut. Any red mite that feed on treated hens will stop laying eggs and die within four hours of treatment.
Application is 0.1ml of Exzolt per kg of body weight, split between two doses seven-days apart. After treatment, it remains in hens’ bloodstreams for several mite cycles, so continues to keep populations suppressed.
“The product must be administered properly,” Mr Hodson says, and there are several tricks to get better results – one being to draw red mite out of control rooms by placing caged birds there throughout treatment.
It’s also essential to replace things like brushes, which can harbour mite and undermine treatment.
“We have used this product on almost six million birds, and it typically takes four-to-seven months in free-range and up to 12 months in colony systems before an infestation fully establishes itself again.
It has a higher initial cost than other treatments, at an estimated 18p/bird, but is undoubtedly time saving and highly effective, says Mr Hodson.
A treatment for commercial poultry producers will cost about 18p/bird
It is an acaracide administered through waterlines. Once in a hens’ blood it kills any red mite that feeds on it
Other water route treatments
There are non-pharmaceutical products available that make hens’ blood less attractive to red mite – or change the signals that they emit, making red mite believe the hens are not a food source.
Reduced feeding hampers the mites’ reproduction cycle and can, therefore, suppress populations. “These treatments are best implemented proactively ahead of red mite populations fully developing,” says Mr Hodson.
They are typically dosed for up to four weeks every day, followed by a ‘top-up’ for five-to-seven days every month after that.
- 83% – overall infestation rate in Europe
- 50p – cost in lost production per bird on mildly infested farm
- £2.23 – high infestation cost per bird
- £320m – total estimated annual economic cost of red mite in Europe