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Northern Fowl Mites

The Northern Fowl Mite (NFM) (Ornithonyssus sylviarum) is an ectoparasite of chickens. They are very small, ranging in size from 0.5-1 mm (0.02-0.04 in). NFM permanently live their entire lives on their host, spending most of their time on the feathers, traveling to the skin surface to feed on blood. During heavy infestations, NFM can cause the chickens a great deal of stress, pain and blood loss (they can potentially lose 6% of their blood daily).

Clinical signs of Northern Fowl Mites

Chickens infested with NFM may appear very irritated, and be seen trying to scratch themselves by rubbing up against objects and biting at their feathers. Feathers in the vent area may be soiled and blackened, due to the accumulation of dried blood and scabs, mite eggs, excrement, and cast skins. You may be able to see them moving in their feathers (as tiny dark specs). Using a bright flash light, inspect the chicken's feathers by parting them to see the skin, especially in the vent area.

How Northern Fowl Mites are Transmitted to Chickens

NFM are found on a wide range of domestic and wild birds, rodents, wildlife, and domestic animals. They can survive off their hosts for 2 to 3 weeks under optimal conditions.

Northern Fowl Mite Vs Red Poultry Mite

Northern fowl miteRed poultry mite
Adult Appearance  
Size0.5-1 mm (0.02-0.04 in)1-1.5 mm (0.04-0.06 in)
ColorGray to blackGray to black
Turns redYesYes
Body typeOvalOval
SpeedSlow movingSlow moving
Visible to the naked eyeAs tiny dark specsYes
Feeds onBloodBlood
Where they are foundVent, breast, and legs. Less commonly on the head and neck.Hide in crevices and cracks during the day, feed on chickens at night
TransmissionWild birds, rodents, contaminated equipment (fomites) and personnelWild birds, rodents, wildlife, dogs, cats, humans, contaminated equipment
Where eggs are laidWhite to off-white bundles of eggs found along the feather shaft of the vent.Lays eggs in cracks and crevices
Average Life cycle5-7 days2 weeks
How you can tellEarly infestations may be difficult to notice, but once numbers increase they can be clearly seen in the feathers and running along the skin surface. May also be seen on recently laid eggs.Look for them at night on the birds
TemperatureCool weatherWarm weather
Clinical signsDermatitis, poor condition (feathers appear 'dirty'), anemia, pale pink comb, soiled feathers near ventRestlessness at night, dermatitis, anemia, may cause chickens to alter where they roost at night.
Carry diseasesNoYes

Clinical Signs

Darkening of vent feathers
Insects visible
Poor quality and/or missing feathers near vent
Soiled vent feathers
Pale pink comb
Skin inflammation
Decreased egg production


  • History
  • Clinical signs
  • Physical exam
  • Skin scrapings


Elector PSPCommercial product manufacturered by Elanco
Fipronil7.5 mg/kg spray on skin once, avoiding the feathers during application. Repeat in 30 daysB Speer
Ivermectin0.2 mg/kg PO, SC, IM, topical once and repeated in 10-14 days.B Speer
Garlic spray10% garlic solution diluted with water, sprayed on the chicken's vent and abdomen, once every 7 days for 3 weeks.
Diatomaceous earthAdd to dustbathing area



  • Do not trim beaks
  • Keep rodents and wild birds off of the premises
  • Provide a dustbathing area with sand plus diatomaceous earth (DE)

Scientific References

Good Overviews

Age Range

Mites are more commonly found on 4 to 10 month old birds, after they reach sexual maturity.

Risk Factors

  • Cooler weather, less than 80°F (26.6°C)
  • Trimming beaks
  • Rodents on the premises
  • Contact with wild birds
  • Poor biosecurity procedures