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Northern Fowl Mites

The Northern Fowl Mite (NFM) (Ornithonyssus sylviarum) is an external parasite of chickens. They are very small, ranging in size from 0.5-1 mm (0.02-0.04 in), therefore they are very difficult to see by the naked eye; they appears as little dark specs. NFM permanently live their entire lives on the chickens, spending most of their time on the feathers, traveling to the skin surface to feed on blood.

During heavy infestations, NFM can cause the birds a great deal of stress, pain and blood loss (they can potentially lose 6% of their blood daily). This results in many chickens developing anemia.

Clinical Signs

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 often appear 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 the light, inspect the chicken's feathers by parting them to see the skin, especially in the vent area.

How NFM are Transmitted to Chickens

NFM infests a wide range of domestic and wild birds, rodents, wildlife, and domestic animals. They can survive off of a host 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
Pale comb
Skin inflammation
Decreased egg production


  • History
  • Clinical signs
  • Physical exam
  • Skin scrapings


Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
Elector PSPCommercial product manufacturered by Elanco
Diatomaceous earthAdd to dustbathing areaMartin et al., 2012
Garlic spray10% garlic solution diluted with water, sprayed on the chicken's vent and abdomen, once every 7 days for 3 weeks
InsecticidesOnly using those approved for use in birds, and in accordance with label instructions.


  • Do not trim beaks
  • Keep rodents off of the premises
  • Exclude wild birds
  • Provide a dustbathing area with sand plus diatomaceous earth (DE), kaolin clay or sulphur
  • Topical application of 10% garlic juice in water
  • Biosecurity
  • Implement a mite monitoring program

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