Mites: Rodent and Bird Mites in Homes
This is a bothersome group of mites that parasitize poultry, wild birds, and rodents. When their normal host is not present they may also bite humans, causing discomfort and sometimes skin irritations. Fortunately, they do not reproduce on human blood, rarely transmit diseases or otherwise cause a health hazard to people. Although these mites are very small (about 1/32 inch long), they can be seen with the naked eye.
Bird and rodent mites and other types of mites found in homes can be difficult to distinguish but their control often requires that they are identified correctly. Any questionable samples should be examined by a specialist familiar with mite taxonomy.
Bird Mites
Bird mites parasitize a wide variety of domestic and wild birds, including poultry, pigeons, starlings, sparrows and robins. These mites normally remain on birds or in bird nests throughout their life. Mite eggs are laid in nests or on feathers. Hatching occurs in two to three days and adults are seen about five days later if birds are present.
However, if a bird falls out of a nest and dies or a nest is abandoned, bird mites seek other hosts. These mites may enter homes, sometimes in large numbers to search for food when nests are on or in buildings. Although bird mites often bite people, circumstances have been described where they are found in large numbers but do not appear to annoy anyone.
The bird mites we encounter most often are northern fowl mites, Ornithonyssus sylviarum, and chicken mite, Dermanyssus gallinae. Both these mites feed commonly on chickens and other poultry but they are also common on many song birds. Northern fowl mites are known to survive up to six weeks without a bird blood meal while chicken mites are known to live as long as several months without one.
Rodent Mites
Rodent mites can be found in homes where rats or mice are abundant or where rodents have recently died. Several common rodent mites have been known to occasionally bite humans.
The tropical rat mite, Ornithonyssus bacoti, is neither truly tropical nor exclusively feeds on rats. This mite can live for up to 10 days off its host and is capable of traveling great distances to find new food sources. In habitats where rodents have been killed, the mites will leave their dead hosts, congregate around heat sources, such as hot pipes and stoves and seek alternative food sources, including humans. The bite of these mites often causes tiny, clear blisters which is accompanied by a rash. However, they are not known to vector any human diseases.
The house mouse mite, Liponyssides sanguineus has a worldwide distribution but is more common in the U.S. in the northeastern states. It is normally a nest dweller and only occurs on the host when feeding. It will attack humans if rodent hosts are not available. This mite is of medical importance because it vectors Rickettsia akari, the rickettsial pox in humans. Fortunately, this disease is relatively rare in the United States and there have not been any known cases in Minnesota.
Another rodent mite which occasionally bites people is the spiny rat mite, Laelaps echidnina. This is probably the most common mite occurring on Norway rats and roof rats in the U.S. It is not a known vector of pathogens.
Control
The easiest method to control bird or rodent mites that have entered your home is to physically remove them with a vacuum cleaner or wipe them up with a moist cloth. Mites are not automatically killed by a vacuum cleaner so freeze the bag to prevent the mites from crawling back out.
To prevent further problems with these mites, it is important to eliminate their hosts and any nests.
Bird Mites
Remove any dead birds that you find. If nests are empty (i.e. no eggs or young birds in them), remove and dispose of them. If eggs or young are found in nests of federally protected song birds (which includes nearly all birds in Minnesota), do not disturb them. If the nesting season is over and only adults remain, you may remove the nest, provided the birds are not harmed.
Only pigeons, starlings, and house sparrows are not federally protected; you may remove their nests regardless of the circumstances.
To reduce bird mites that may migrate indoors, spray an insecticide effective against mites. Sprays and aerosols containing the active ingredient pyrethrum (or pyrethrins) kill mites immediately on contact, though the treatment will remain effective for at most a few days. Bifenthrin is another pesticide that is effective against many mites and retains its killing properties for longer periods. Bifenthrin can be used, according to label directions, in living areas, attics and crawl spaces. Commercially bifenthrin is sold under the trade name, Bifen IT®. Treat outside around windows, doors, and other possible points of entry.
Caution: Read all product directions very carefully before buying insecticides and again before applying. If you cannot treat an outside area without harming an occupied nest, do not spray. Leave the nest alone until it is abandoned; then you can spray the house if mites are still a problem.
Rodent Mites
To eliminate mice and rats from the home, first locate the entrance/exit point used by the rodents to enter the building. Once located, the entrance/exit point must be completely blocked.
Second, remove all possible food sources by placing all pantry and cupboard foodstuffs into air-tight containers. Eliminate potential nesting sites by cleaning key areas such as closets, basements and storage areas.
Thirdly, trap rats and mice with kill traps, live traps and/or glueboards. Bait mouse traps with a mixture of peanut butter and rolled oats. Bait rat traps with meat products such as ham or beef. Arrange traps 10-15 ft apart placed perpendicular to walls, baseboards and rows of boxes. For more information on trapping rodents in the home, contact your county extension office.
University of Minnesota County Extension Service