english VersionDeutsche Version Veterinärmedizinische Fakultät, Universität Leipzig, Institut für Parasitologie (Institutsdirektor: bis 30.Sept.2001 Prof. Dr. Regine Ribbeck; ab 01.Okt.2001 Prof. Dr. A. Daugschies)
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I. Adverse effects of feather mites
II. Adverse effects of feather shaft mites
III. Adverse effects of feather follicle mites


I. Adverse effects of feather mites
In the literature covering this subject, one can find controversial discussions about the adverse effects of feather mites. On one hand, it is reported about severe destruction of the feather coat and other impairments, which clearly result in the classification as parasites. On the other hand, they are described as harmless, non-pathogenic commensally living organisms on skin and feathers, which normally do not cause any problems to the host bird.

Reinhardt (1950) describes the effects of feather mites on poultry: "Mostly, feather mites are absolutely harmless. Only during moulting they cause irregularities in growth and loss of feathers, as well as itching". Borchert (1962) shares this opinion and adds concerning Falculifer rostratus in pigeons: the fact that the plumage is being damaged by the adult mites and by feather picking by the birds themselves. Mostly affected are the outer edges of flight feathers of wing and flight feathers of tail, leaving behind only bare feather shafts." Manuel and Siores (1967) report on feather damages in fowls on the Philippines caused by feather mites (Pterolichus obtusus). Especially the flight feathers of wing and –tail, as well as the covert feathers of wing and –tail had been affected. According to Vogel (1969): "…pigeons severely infested by mites are showing an unkempt feather coat, constant preening and their capability to flying is rather adversely affected. Mites appearing in masses are mainly infesting flight feathers of wing and flight feathers of tail, as for them to become chapped and tending to break. Therefore, the plumage loses its shining hint of grey and typical gloss. Feathers may be worn out by destroyed proximal and distal barbulae". Pillers (1927) as well reports on perforations in feathers of pigeons leading back to the mite Falculifer rostratus. Hiepe and others (1962), as well as Hiepe and Ribbeck (1982) clearly classify feather mites as parasites and describe destruction of feathers caused by mites in stocks of ducks. Destruction of feather coat affects the ability of swimming, especially keeping in the right position, with the possible result of drowning. Furthermore, an infestation with feather mites might lead to reproductive disorders in drakes. According to Dabert and Ehrnsberger (1996) the damages for host birds in most cases are insignificant, and according to Gylstoff and Grimm (1998), feathers are losing their normal direction, bend and finally break. "Mites of the family Ascouracaridae often infest the hollow interior part of the feather, such as the calamus and the lower part of the shaft. Damaging the feather this way and leaving behind long corridors in the sponge like substance of the feather shaft, the stability of covert feathers is severely decreased", as Dabert and Ehrnsberger (1995) are reporting. Baker (1996) investigated 198 exhibition Gadgerigars showing damages in plumage in Great Britain. In 18, 2% of these cases, feather mites had been detected as the reason for these destructions. So, feather mites take the third place in the list of reasons for feather damages in these budgerigars. Another aspect of adverse effects of feather mites can be seen in their potential role as human allergens. Colloff and others (1997) report on allergic reactions in humans breeding pigeons or budgerigars, which had been caused by feather mites.

According to own experiences with resident wild birds, companion birds (in cage and aviary), wild and domestic pigeons, birds in care after being injured, as well as single feathers, infested by feather mites, we cannot confirm the damages described in literature. Even massively infested birds (several thousand mites) did not present any evident feather destruction. Observed birds did neither show increased preening nor any itching like behaviour.



II. Adverse effects of feather shaft mites

Reinhardt (1959) states: "Apart from feather loss and aggravation of moulting, mites (of feather shafts) do not seem to leave any damage". Borchert (1962) concludes "the infestation does probably not substantially affect the birds´ state of health". Also Vogel (1996) grades the adverse effects concerning pigeons negligible. Kummerfeld (1982), as well, classes the relevance of feather shaft mites as small; yet, in cases of feather loss, an infestation with mites as a potential reason should be taken into consideration. However, Fritzsche and Gerriets (1959) describe the adverse effects caused by an infestation with feather shaft mites as follows: "…they gnaw the shafts to pieces and fill the hollow inside with a yellow-greyish powder like mass. This way feathers are losing their normal position, bend and fall out ahead of time." Quinten (1998) describes that feathers affected by mites are easily breaking and showing a predilection for malformation. According to Kummerfeld (1999), the mites are damaging the medullar caps of the calamus and, depending on the time and extend of infestation, lead to chapped feathers.

Up to this point of time, we could only prove the existence of feather shaft mites in wild birds. Yet, in these birds, no evidence of either gaps between feathers, chapped or loose feathers, or any other obvious irregularities had been found.



III. Adverse effects of feather follicle mites

According to Reinhardt (1950) "…feather follicle mites can be found in pigeons, passeriform birds, larks, psittacine birds and so on preferably underneath the wing and in the sternal region in yellow cysts of sizes varying from pea-size to bean-size, representing the dilated feather follicles." In heaped occurrence, the poultry may suffer from feather loss and cachexia. Also Borchert (1962) describes the adverse effects of feather follicle mites the same way Reinhardt does. Similar is the conclusion of Hiepe and Ribbeck (1982): "Feathers start falling out because of the inflammation of the feather follicles. In case of severe infestation, a decrease in body weight can be seen, which may result in death." Vogel (1969), Hiepe and Ribbeck (1982) and Kummerfeld (1982) state that female mites invade the skin directly until egg laying and place their eggs underneath the skin as well, which might lead to thickening and inflammation of the skin.