“Right now, poultry management of free-range layers needs to be steady,” said Frank Clerkin, pig and poultry vet from Cootehill, Co. Cavan.

“Birds are back out, feed prices have rocketed, so it’s all about utilising every ounce of feed and making sure there are no errors, because every egg counts.”

Frank Clerkin

This summer will be a challenging time for many farmers, including free-range egg producers. For many flock-keepers the warmer months bring the additional problem of poultry red mite (PRM).

“We’ve seen the temperature rise in the last couple of days and just as we see the fly numbers increasing, the mites within the poultry sheds will also bloom,” said Frank.

Poultry red mites live and rapidly breed within the hen house, emerging at night to crawl onto and suck blood from the birds. Red mites survive and reproduce at a wide range of temperatures, but at 17-25° and around 70% humidity their life cycle is shorter, reducing to between seven and 10 days.

This means that during the warm summer months, poultry-keepers see a sudden explosion in numbers because just one female mite is able to produce 2,000 more mites in a month.

“Hens sleep with one eye open because of their fright and flight mechanism for fear of predators, but they still need to rest. Just imagine sitting all night with creepy crawlies on your feet and neck,” said Frank.

“The birds are restless, lifting their feathers and pecking themselves until they bleed. Very high mite burdens can cause so much blood loss in the hens that they cause anaemia – they’re call red mite because they become engorged with the hen’s blood.

“All of this increases the birds’ stress hormones which in turn makes them more susceptible to disease, and of course, mites themselves are also known to carry viral and bacterial pathogens like E. coli, salmonella and listeria. It can be a real problem.”

Egg production

These health issues also affect egg production: More downgraded eggs in the packing station, higher rates of floor eggs and the laying pattern may be more spread out.

Farmers may see a reduction in the laying rate, compared either to previous flocks or to your wholesaler’s average. Depending on the size of the flock, if hens are hitting peak lay when PRM becomes a problem, the impact on production can be sizeable. Some studies have indicated that high infestation can cost up to €2.50/bird.


A systemic treatment from MSD Animal Health containing fluralaner, has been available for the control of poultry red mite infestations since 2017, with over seven million hens treated on the island of Ireland.

Treatment consists of two applications (via the drinking water), seven days apart, in order to target all stages of the life cycle. The egg withdrawal period is zero days.

It is the first veterinary product centrally registered in the EU to include animal welfare improvement in its licence.

Studies in commercial layer farms demonstrated that the elimination of poultry red mite from infested hens following treatment with this particular product significantly improved behavioural indicators of animal welfare, including the reduction of night-time activity, head shaking and preening at night and during the daytime.

A reduction of blood corticosterone concentration, a key indicator of stress, was also observed.

“Flocks that are mite-free are more settled, rest easier and are more comfortable,” said Frank.

“The knock-on from that is that following this treatment, they will use the nest box and happily perch close to the nest box at night. I’ve also noticed a significant improvement in behavioural vices, with less aggression and a reduction in over-preening and feather-plucking resulting in fewer birds with skin lesions.

“Right now, farmers need to keep their production steady. It’s understandable that producers want to keep costs at a minimum, but if your flock is being affected by red mite, it’s a false economy to do nothing.

“You need to be able to treat effectively to try to keep that process steady, maximise feed and make every egg count.”

More information

For information and advice on the threat of Poultry Red Mite and the best control strategy for your farm or smallholding, contact your veterinary practitioner or MSD Animal Health, Red Oak North, South County Business Park, Leopardstown, Dublin 18, Ireland.

MSD Animal Health can be contacted at: 01 297 0220 or emailed at: [email protected].