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The Tropical Fowl Mite (Ornithonyssus bursa) is a blood-feeding mite commonly found on a range of wild and domestic birds. It is rarely found on mammals, but where infested birds are nesting in close proximity to humans, these mites may enter homes and bite people. The bite is irritating to humans and may cause persistent itching and painful dermatitis. Tropical Fowl Mites are widespread in tropical and warm regions of the world. Although the Tropical Fowl Mite (which measures around 0.75 mm long and 0.5 mm wide; Oliveira et al. 2012) is similar to the Northern Fowl Mite (O. sylviarum), it can be distinguished by the dorsal plate. The posterior end of this plate tapers acutely in the Northern Fowl Mite but more evenly in the Tropical Fowl Mite. Furthermore, three pairs of setae (bristles) are present on the sternal plate in Tropical Fowl Mites but only two pairs in Northern Fowl Mites (see illustrations in online Featured Creatures species account)
The Tropical and Northern Fowl Mites have similar life cycles. There are five developmental stages: egg, larva, protonymph, deutonymph, and adult. In the laboratory, most eggs are deposited in the litter away from its hosts. In the field, eggs are laid on the host or in the nest. Eggs hatch within three days and the non-feeding larvae molt in around 17 hours. The protonymph molts in one or two days, but the length of the deutonymph stage is not known for the Tropical Fowl Mite (it is about a day in the Northern Fowl Mite).
The nymphs and adults of the Tropical Fowl Mite take blood meals (in contrast to the Northern Fowl Mite, in which only the protonymph and adult stages feed). On birds, most reproduction takes place in the host's nest. On chickens, the mites prefer the fluffy downy feathers and are numerous around the vent (the cloacal opening), accumulating on a few feathers. A human handling an infested chicken will become infested.
The Tropical Fowl Mite is a serious pest of both domestic fowl and many wild birds. It is almost never found on wild mammals, although there are numerous records of it biting humans (e.g., Oliveira et al. 2012). It has never been implicated as a disease vector. Attacks on humans cause discomfort similar to that caused by the Northern Fowl Mite, which is also a pest of domestic fowl and wild birds.