Prevalence of Avian Tuberculosis in Domestic Chickens in Selected Sites of Ethiopia

Abstract

This study was conducted on 282 domestic chickens of Bahir Dar, Yilimana densa woreda, and Bishoftu by using avian tuberculosis diagnosis procedures such as single intradermal avian tuberculin test, post mortem examination, and Ziehl-Neelsen (Z-N) staining from tissue samples of naturally infected Domestic chickens (Gallus domesticus). The overall of this disease current prevalence was determined based on tuberculin skin test results supported by Z-N stain and post mortem lesions and it was 4.26% (12/282) (95% CI: 1.9-6.6), with higher prevalence in semi-intensively reared exotic chickens (5.85%) than backyard reared indigenous local chicken. This indicates the occurrence of this disease has a statistical significance association both with the breed and production system, both having a p-value of 0.03. Twelve strong positive reactor chickens have shown a swelling of greater than 5 mm in diameter 48 h. of post injection with different variety results, some with edematous swelling, and others with firm erythematic nodular swelling. Typical tuberculous lesions were seen mostly on the liver and spleen. From 12 tuberculi reactor slaughtered chickens, a total of seven (58.3%) chickens had gross lesions on different visceral organs, of which three (42.9%) examined chickens have manifested gross lesions on more than one organ. On acid fast staining five (41.67%) with grossly discernible lesions revealed acid-fast rods. For culturing, Lowenstein-Jensen (L-J) media was used as it yields more positive cultures, greater numbers of colonies on positive tubes, and shorter incubation times. None of the samples shown colonial growth till 8 weeks of incubation period and this may be due to the slow growth nature of mycobacterial species (especially when the infection was due to Mycobacterium avium subspecies paratuberculosis which needs a considerable long time for growth) and/or the current incubation temperature (37°C) may not be optimal as it does not fit the natural hosts internal body temperature and still the culture result is under process to see any growing colony. Therefore, this finding signaling an urgent need for intervention program to control the disease in domestic chickens and prevent zoonotic transmission.