Mycobacterium avium subsp. avium distribution studied in a naturally infected hen flock and in the environment by culture, serotyping and IS 901 RFLP methods

Abstract

Mycobacterium avium subsp. avium ( MAA) of serotype 2 and genotype IS 901+ and IS 1245+ was cultured from 21 naturally infected hens ( Gallus domesticus) from one smallholder aviary. From a total of 330 samples taken from hens, 124 mycobacteria were detected. Out of which MAA was detected in 103 (35.7%) of 288 tissues, in 4 (19.0%) of 21 swabs of cloacae and in 9 (42.9%) of 21 faeces samples, 8 other conditionally pathogenic mycobacterial species were also isolated. Tuberculous (TB) lesions were found in the liver, spleen and intestinal organs of seven hens. The isolates of MAA ( n = 58) from 16 infected hens (7 with TB lesions and 9 without TB lesions) were found to be of 3 IS 901 RFLP types AE ( n = 48), AD ( n = 4) and E ( n = 6), where these MAA isolates are highly virulent to hens. Mixed infections with IS 901 RFLP types (AE and AD) and (AE and E) were also evident in seven hens. From a total of 35 examined environmental samples, 23 mycobacterial isolates were detected. Out of which four (17.4%) MAA isolates of IS 901 RFLP type AE and 19 (82.6%) other isolates of conditionally pathogenic mycobacteria were detected. The finding of identical IS 901 RFLP types from both tissues and faecal isolates confirms that infected domestic hens are the principal source of infection for other susceptible hosts and lead to the contamination of the surrounding environment. The presence of different IS 901 RFLP types in tissue isolates may indicate the repeated incidence of MAA infection and the occurrence of polyclonal infection.