• Cause: the causative agent is Ornithonyssus sylviarum, an obligate blood-sucking mite.
• Signs: clinical signs depend on the level of infestation. It can cause irritation to the hen, anemia causing a pale comb, weight loss, listlessness and poor egg production.
• Diagnosis: mite identification. It is approximately 0.5 mm in length and is brown/black once it has had a blood meal.
• Treatment: prevention is with diatomaceous earth, good flock hygiene and chemical treatment as needed.
• Prognosis: good with early intervention.
• Northern fowl mites can spend their whole life on the birds.

ℹ️Print off the Factsheet on Northern fowl mite infestation to give to your clients.

• The mites lay their eggs at the base of the feathers in the cloacal area where the skin is softer. The feeding of the mites causes irritation to the hens.
• The feeding of the mites can cause anemia as numbers of mites can multiply rapidly.
• Owners may detect mites on them when they handle the hens.
• The irritation and rubbing may cause feather loss.
• Eggs can have mites or red streaks on them.
• Infestations can cause egg production to drop due to chronic debility of the hens.
• Fluctuating mortality.

• A pale, listless hen presented with numerous egg cases around the bases of the feathers especially in the cloacal area.
• There may be feather loss and red irritated skin.

• Worldwide.

• Peak infestation at 25-35 weeks (maximum laying for poultry industry).
• Levels will decline as immune response stimulated but will remain on hen for lifetime.

• All poultry.

• Western equine encephalomyelitis, St. Louis encephalitis, and Newcastle disease viruses Newcastle disease, as well as fowl pox virus Fowl pox, have been isolated from these mites. However, the mites are not significant vectors of these viruses.

• Significant losses of production and increased mortality and morbidity for poultry industry.

• The mites can be introduced into the flock by new hens, wild birds, rodents and equipment.
• The mites have a five-stage life cycle from egg to larva, protonymph, deutonymph and adult. This cycle can be completed in 5-12 days allowing rapid buildup of infestations.
• Unmated females can still lay eggs and can mate with male offspring to produce females
• Northern fowl mites usually spend their entire life on the bird. They can live for short periods (days) in the environment.
• Mite levels can reach up to 100,000 per bird.
• In the blood sucking stages up to 6% blood loss per day can occur leading to significant anemia.

General

• Young birds before some immunity built up (but this only reduces numbers of mites rather than becoming immune).

Specific

• Close contact with infected birds.

• Anemia caused by blood feeding of the mites Anemia/pale comb.
• They are immensely irritating to the birds throughout the day and night and can lead to agitation and feather pulling Feather/vent pecking/cannibalism.
• Morbidity and production loss common.
• Mortality is linked with blood loss and the introduction of secondary bacterial infections through the skin lesions.

• Mites live their entire lifecycle on the birds.
• The lifecycle can be as short as 5-12 days leading to rapid build-up of numbers.

• Mites will spread through flocks from contact with infested birds.
• Mites can spread to new flocks via wild birds, rodents, personnel, equipment and introduction of new birds.
• Temperatures above 37-39°C/100-102°F in the feathers are lethal to mites.

Refereed papers

• Recent references from PubMed and VetMedResource.
• Cirak V Y, Aksit D, Cihan H & Gokbulut C (2018) Plasma dispositions and concentrations of ivermectin in eggs following treatment of laying hens. N Z Vet J 66 (3), 121-124 PubMed.
• Hinkle N C, Jirjis F, Szewczyk E et al (2018) Efficacy and safety assessment of a water-soluble formulation of fluralaner for treatment of natural Ornithonyssus sylviarum infestations in laying hens. Parasites Vectors 11 (1), 99 PubMed.
• Vezzoli G, King A J & Mench J A (2016) The effect of northern fowl mite (Ornithonyssus sylviarum) infestation on hen physiology, physical condition, and egg quality. Poult Sci 95 (5), 1042-1049 PubMed.

Other sources of information

• Murillo A C (2022) Mites of Poultry. In: MSD Veterinary Manual. Website: www.msdvetmanual.com.
• G Poland & A Raftery (2014) Eds BSAVA Manual of Backyard Poultry Medicine and Surgery. BSAVA, UK.
• Murillo A C & Mullens B (2013) Northern Fowl Mite (Ornithonyssus sylviarum [Canestrini and Fanzago]). In: Veterinary Entomology. Website: www.veterinaryentomology.org.