Implementation of different histochemical methods in diagnostics of brain Aspergillosis in turkey chicks

Abstract

Aspergillosis is a frequent fungal disease in different species of birds and mammals caused by fungi of the genus Aspergillus. It is characterized by inflammatory changes primarily in the respiratory system, even though it sometimes takes on a generalized form when several organ systems are affected. Mucotic-granulomatous meningoencephalitis with a predominant localization in the cerebellum has been described in turkeys, ducks and geese. Within this paper, examinations have been performed on a flock of broiler turkeys aged 12 days who had sustained evident neurological disorders in the form of ataxy, torticollis, paresis, and paralysis of the hind extremities and wings. In three of the ten autopsied chicks the macroscopic findings indicated granulomatous encephalitis of the cerebellum. A white-coloured granuloma, around 3mm in diameter, was situated cranioventrally and was clearly visible on the sagital section of the cerebellum. Mucological examinations of the cerebellum lesion resulted in the isolation of the fungi Aspergillus fumigatus. Haematoxylin-eosin (HE), Grocott and PAS methods were used for the evaluation of histopathological changes and proving Aspergillus fumigatusa hyphae. The microscopic examination of brain tissue sections stained with the HE method revealed the existence of a granuloma with a centrally placed necrotic area. The necrotic area was infiltrated with heterophilic granulocytes and surrounded by macrophage, giant cells and lymphocytes. A connective tissue capsule was located on the periphery of the granuloma. The fungi hyphae, as integral parts of the granuloma, were difficult to observe, and in some samples stained using the HE method they could not be seen at all. On the other hand, sections stanied using the Grocott and PAS methods showed prominent septed and branched hyphae in different parts of the granuloma. With the objective of making an etiological diagnosis of mucotic diseases, it is necessary to apply several histochemical methods, in addition to isolation.

Keywords

• turkey chicks
• histochemical methods
• meningoencephalitis
• Aspergillus fumigatus