The chicken mite, Dermanyssus gallinae, has a world-wide distribution and is a nocturnally blood-feeding ectoparasite on domestic and wild birds. During the summer when synanthropic birds, for example, house sparrows, starlings or doves, have their nests inside or on the outside of human habitations, the mites will feed on the nestlings and their avian parents. When the birds leave the house the mites will try to find substitute hosts, which often happen to be people inhabiting the house. The bites can be painful and irritating. The length of the mite is about 0.7mm (unfed) to 1mm (fed). The recently fed mite is bright red in colour. Poultry houses can be infested by thousands of D. gallinae which may lead to serious blood-loss, reduced egg laying, and even death of the birds (Varma 1993). Infestations in schools and other buildings (often at the end of the summer) usually originates from birds' nests under eaves or in attics. The problem can usually be solved by removal of the nests, and by vacuum cleaning and insecticidal treatment of the attic and infested rooms.
Liponyssoides sanguineus (the house-mouse mite)
The house-mouse mite, Liponyssoides sanguineus, is a nest-dweller and comes to its hosts (mice, rats, and other rodents) only to feed. Liponyssoides sanguineus is a vector of rickettsial pox (caused by Rickettsia akari) in man. The infection has occurred as outbreaks in the US, Ukraine, and in Africa.
Ornithonyssus sylviarum (the northern fowl mite)
The general appearance and biology of the northern fowl mite, Liponyssoides sanguineus, is similar to those of D. gallinae. The northern fowl mite parasitizes domestic and wild birds but will also attack mammals, including humans. It is common in the northern temperate regions of North America and Europe but occurs also in southern Africa and southern Australia.
There are several species of Cheyletiella mites which feed on the keratin layer of the epidermis of cats, dogs, and rabbits. People handling infested animals can become infested and develop an itching dermatitis.
More than 1200 species of trombiculid mites (family Trombiculidae) have been described. About 20 of these are known to attack man, thereby causing chigger dermatitis (trombidiosis) or transmitting disease (scrub typhus or tsutsugamushi fever).
In several parts of Europe, including the British Isles and Scandinavia, microscopic chigger mites (Neotrombicula autumnalis) also denoted as harvest mites, are present in relatively distinct, focal localities. In the New World, species of the genus Eutrombicula have a biology and medical importance similar to those of Neotrombicula. The larval mites (about 0.25mm long) of N. autumnalis feed mainly on small mammals and birds. Only the larval stage is parasitic on vertebrates. The larvae are not blood-feeders but rather feed on the enzymatically liquefied skin tissues of the host. People visiting Neotrombicula-infested localities in the late summer may be attacked by hordes of the creamy white to bright red larvae. The individual larvae are difficult to see, but larvae attacking in clusters can easily be detected. People who have previously been bitten by chigger mites will develop an allergic condition, chigger mite dermatitis, scrub itch or trombidiosis, presumably caused by allergens in the saliva of the mites. In the typical case of trombidiosis there is no reaction until after the second time of exposure. About 2-3 weeks are needed between the first and second exposure in order for a typical allergic reaction to develop. Usually, the dermatitis is not serious but is often intensely itchy and starts a few hours after exposure. Small, red pustules (3-4mm) can be seen, mainly on areas where the skin is moist, where the clothes are tight to the skin, or under the watch-bracelet (Varma 1993; Kettle 1995). Personal protection from larval chigger mites is of course most optimally done by avoiding to visit infested habitats. If this is not possible, boots and trousers (well tucked into the boots) can be used, particularly if treated with an effective mite-repellent or acaricide, for example, diethyl-toluamide (DEET), benzyl-benzoate, or permethrin.
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