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 mite | Red poultry mite |
|---|
| Adult Appearance | | |
| Size | 0.5-1 mm (0.02-0.04 in) | 1-1.5 mm (0.04-0.06 in) |
| Color | Gray to black | Gray to black |
| Turns red | Yes | Yes |
| Wings | No | No |
| Body type | Oval | Oval |
| Speed | Slow moving | Slow moving |
| Visible to the naked eye | As tiny dark specs | Yes |
| Feeds on | Blood | Blood |
| Where they are found | Vent, breast, and legs. Less commonly on the head and neck. | Hide in crevices and cracks during the day, feed on chickens at night |
| Transmission | Wild birds, rodents, contaminated equipment (fomites) and personnel | Wild birds, rodents, wildlife, dogs, cats, humans, contaminated equipment |
| Where eggs are laid | White to off-white bundles of eggs found along the feather shaft of the vent. | Lays eggs in cracks and crevices |
| Average Life cycle | 5-7 days | 2 weeks |
| How you can tell | Early 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 |
| Temperature | Cool weather | Warm weather |
| Clinical signs | Dermatitis, poor condition (feathers appear 'dirty'), anemia, pale pink comb, soiled feathers near vent | Restlessness at night, dermatitis, anemia, may cause chickens to alter where they roost at night. |
| Zoonotic | Yes | Yes |
| Carry diseases | No | Yes |
