Post-Mortem Examination in the Diagnosis of Johne’s Disease in Goats

Abstract

Post-mortem examinations play an important role in Johne’s disease programmes in Norway. The results of such examinations of samples of viscera from 2997 goats carried out during the 5-year period 1972–1976 are given. The investigations show that the demonstration of macroscopical changes in mesenteric lymph nodes and small intestine has only limited value as a guideline in the post-mortem diagnosis of Johne’s disease in goats. Often macroscopical changes were not seen or they were non-specific. Caseous and/or calcified foci in mesenteric lymph nodes in infected animals were demonstrated quite often whilst observed intestinal changes were strikingly few. Corrugation of the mucosa was rare. However, in sections of macroscopically unchanged intestine marked epithelioid cell infiltrations and abundant acid-fast bacilli were not uncommon. In sporadic cases productive inflammation with tubercle formation was seen in lymph nodes in infected animals.

Bacteriological culture was by far the most reliable post-mortem diagnostic method. By this method 92% of the infected goats were detected. The corresponding figures for histological examination and microscopy were 54% and 47%, respectively.

Sammendrag

Post mortem undersøkelser spiller en betydelig rolle i bekjempelsesprogrammet mot paratuberkulose hos geit i Norge. I femårsperioden 1972–1976 ble organprøver fra 2997 geiter undersøkt. Disse undersøkelsene viste at makroskopiske forandringer i krøslymfeknuter og tynntarm-avsnitt bare har begrenset verdi som rettesnor ved post mortem diagnostikk av paratuberkulose hos geiter.

Mange infiserte dyr viste ingen makroskopiske forandringer i krøslymfeknuter eller tarmavsnitt. Hos andre var de registrerte forandringer overveiende uspesifikke. Av typiske forandringer hos infiserte dyr kan nevnes mer eller mindre svulne, ødematøse krøslymfeknuter. Of te fautes forostede og/eller forkalkede foci i disse. Tarmforandringer var få og oftest lite uttalte. Bare i enkelte tilfeller fautes fortykket slimhinne med foldedannelser. I histologiske snitt fra makroskopisk normale tarmavsnitt fautes imidlertid ofte betydelige epitheloide celleinfiltrasjoner og rikelig med syrefaste staver. Hos ganske få infiserte dyr påvistes produktiv betennelse med begynnende tuberkeldannelser i krøslymfeknuter.

Av de påviste infiserte dyr ble 92% funnet ved bakteriologisk dyrking. De tilsvarende tall for histologisk undersøkelse og direkte mikroskopi var henholdsvis 54% og 47%.