J RaptorRes. 30(1):45 ¸ 1996 The Raptor ResearchFoundation, Inc.

A PREEN GLAND ABNORMALITY IN A FREE-LIVING WHITE-HEADEDVULTURE (Aegypius occipitalis)

The uropygial(preen) gland produces oil which enhancesthe integrityand waterproofingof a bird's plumage.In African Old World vultures, preening,coupled with sunning behavior, plays a part in feather maintenance(D.C. Houston, 1980, Ibis 122:366-369). Although examinationof the uropygialgland has long been recommendedas a routinepart of clinicalexamination of raptors(J.E. Cooper,1985, Veterinary aspectsof captivebirds of prey. Standfast Press,Gloucester, U.K.), little has beenpublished on preengland abnormalitiesin thesebirds, especiallyin the wild. Here pathologicalfindings in the preengland of a white-headedvulture (Aegypiusoccipitalis) from Tanzania, East Africa, are reported.The vulture, an adult, was found dead under a tree in Mikumi National Park. No signsof predationor other injury that might have causedits death were noted.The carcass,which appearedto be fresh, had been briefly placedin a freezer at the park. Gross postmortemexamination revealed that the bird was a female in goodcondition (mass 4.5 kg) with substantialsubcutaneous fat. Radiographsshowed no skeletalchanges suggestive of trauma, nutritional/metabolicdisorders, or infectiousdisease. The only externalabnormalities noted were damageto the tips of wing and tail feathersand a turgidpreen gland from whichdirty white toothpaste-likematerial rather than oil couldbe expressed. Histopathologicalexamination of the preengland revealedsome dilated acini and ductslined by simple,squamous epithelium;elsewhere, the glandshowed whorls of keratin, stratifiedsquamous and giant cellsin closeproximity to secretorymaterial. In a secondsection there was moderate hyperkeratinization of the epitheliumoverlying the gland. On the basisof thesefindings the abnormalitywas diagnosedas a preen gland impactionof uncertainetiology. Microbiologicalculture was not performedbut the histopathologicalfindings, in particularthe absenceof any heterophil infiltrate, would appear to rule out a bacterialinfection. The stratifiedepithelium suggests a metaplasticchange in the gland and the giant cellsmay have beena responseto keratin. The uropygialgland abnormalityin this vulturedid not appearto havecontributed to deathnor was it associated with any obviouschanges in the bird'splumage. The causeof the impactionwas unclearas hasbeen the casein preen glandimpactions reported in other speciesof bird includingbudgerigars (Melopsittacus undulatus; M.L. Petrak, 1982, Diseasesof cageand aviary birds,Lea and Febiger,Philadelphia, PA U.S.A.), helmetedguineafowl (Numida meleagris; Cooperunpubl. data), and merlins(Falco columbarius; J.E. Cooperand N.A. Forbes,1986, Vet. Rec. 118:232-235). The only other impactionof this kind diagnosedin an East African raptor by the author involveda live tawny eagle (Aquilarapax) which was found trapped,with heavily soiledplumage, on the edgeof a sodalake in Kenya (Cooper unpubl. data). The underlyingpathogenesis was not elucidated. I am grateful to the staff of Mikumi National Park and ABRU, especiallySabine Schmidt, Christopher Holmes and JoAnn Dokter, for providingthe specimen,and to colleaguesat the Faculty of Veterinary Medicine for taking radiographsand preparinghistological sections.--John E. Cooper, Faculty of Veterinary Medicine, Sokoine Uni- versity of Agriculture, P.O. Box 3021, Morogoro, Tanzania. Presentaddress: Durrell Instituteof Conservationand Ecology,The University, Canterbury, Kent CT2 7PD U.K.

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