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Tropical Fowl Mite

Other Names: Bird Mites

The tropical fowl mite, Ornithonyssus bursa is a common ectoparasite of chickens as well as wild nesting birds (such as pigeons, starlings, and sparrows). They are attracted to their nests, and both live and thrive in nesting material (hay, straw, shavings, etc.). This mite common in warmer regions of the world, and usually associated with moist or humid conditions. It is most active during the winter months.

Tropical fowl mites cause irritation (excessive itching), painful dermatitis, feather loss, and anemia in chickens. The mites are most commonly found in the vent area and accumulate in masses on just a few feathers. Tropical fowl mites can also spread from the birds to humans---resulting in avian mite dermatitis (also referred to as gamasoidosis), characterized by prolonged itching, welts, and painful dermatitis.

The tropical fowl mite is known for inhabiting abandoned nests of wild nesting birds. They may also become a pest to humans in areas of high bird populations or where wild birds are allowed to roost on roofs and around the eaves of homes.

The life cycle of the tropical fowl mite is similar to that of the Northern fowl mite. It lays its eggs on the birds or in the nests, which take 3 days to hatch. They will almost immediately begin feeding off the blood of the birds, and increase in their numbers rapidly. Without a blood meal from a bird host, they usually will die within 3 weeks.

Clinical Signs

Feather loss near vent area
Irritation, excessive itching
Pale comb/wattles


  • History
  • Clinical signs
  • Physical exam


FipronilFrontline Spray (0.25%-w/v-fipronil) applied directly to the bird's body.
Remove all abandoned wild bird nests nearby, which may be found around eaves, roof spaces, cavities in walls, foundations, porches, and on window ledges. Note Wear gloves when removing nests, since these mites can transfer to humans.
Remove and replace all nestbox materials (hay, straw, shavings, etc.), and thoroughly scrub clean with soap and hot water.
Treat the nestbox area with an approved insecticide, such as a surface spray or insecticide powder.



  • Remove abandoned wild bird nests which are located near where your flock lives.
  • Discharge wild birds from nesting in, on, or in the vicinity of coops.
  • Periodically remove and replace any materials present in nestboxes and all bedding materials (hay, straw, shavings, etc.)

Scientific References

Risk Factors

  • High populations of wild birds nesting in the area.
  • Abandoned wild bird nests
  • Not regularly (at least once a month) changing materials used for nestboxes.