Multi-locus variable-number tandem repeat analysis (MLVA) reveals heterogeneity of Mycobacterium bovis strains and multiple genotype infections of cattle in Ethiopia.
Bovine tuberculosis (BTB) remains a major threat to animal and human health, and obstructs international and inter-regional livestock trade in Ethiopia. Many aspects of epidemiology of BTB and its causative agent, Mycobacterium bovis (M. bovis) are not well known. Aims of the study were to elucidate molecular characteristics of M. bovis strains using MLVA typing method. Further aim was to determine infection pressure associated with occurrence of multiple genotypes in individual infected cattle. Data and samples were collected in the period July 2006-January 2007 in cattle slaughtered at five representative abattoirs across the country. Molecular investigation of the isolates was carried out using multilocus variable-number tandem-repeat analysis (MLVA) of 28 variable numbers of tandem repeat (VNTR) loci, and the results were compared to spoligotyping. This study is believed to contribute to the knowledge of molecular genetics and epidemiology of M. bovis in Ethiopia and elsewhere with similar BTB epidemic situation and livestock production settings. Four-hundred and six tissue samples from 337 carcasses revealing gross pathologic lesions compatible with BTB were collected from five abattoirs. Fifty-eight isolates obtained from cultured samples were subjected to region of difference (RD) analysis and MLVA typing. RD confirmed all isolates as being M. bovis. MLVA revealed a high heterogeneity of M. bovis (19 genotypes) and the discriminatory power of MLVA was higher than for spoligotyping (Hunter-Gaston Diversity Index (HGDI) 0.92 vs. 0.82). Adoption of the nine VNTR loci with ⩾3 alleles provided good differentiation between the isolates. However, differentiation was optimized when MLVA was combined with spoligotyping (HGDI=0.99). MLVA confirmed infections with multiple genotypes in 38.5% (10/26) of individual animals. In conclusion, the usefulness of MLVA for genotyping M. bovis in high prevalence settings was demonstrated. BTB in Ethiopia is caused by heterogeneous populations of M. bovis and individual carcasses were often infected with different genotypes, indicating a high infection pressure perhaps related to the absence of protective immunity conferred by infection.
Center for Epidemiology and Biostatistics, Norwegian School of Veterinary Science, P.O. Box 8146, N-0033 Oslo, Norway; College of Medicine, University of Arizona, 1656, E Mabel St, P.O. Box 245221, Tucson 85719, AZ, USA. Electronic address: demelash.biffa@gmail.com.
Demelash
D
Biffa
Department of Animal Health, National Veterinary Institute, P.O. Box 750 dep, N-0106 Oslo, Norway.
Tone Bjordal
TB
Johansen
Section for Arctic Veterinary Medicine, Norwegian School of Veterinary Science, Stakkevollveien 9010, Tromsø, Norway.
Jacques
J
Godfroid
The Roslin Institute, University of Edinburgh Easter Bush Roslin, Midlothian EH25 9RG, United Kingdom.
Adrian
A
Muwonge
Center for Epidemiology and Biostatistics, Norwegian School of Veterinary Science, P.O. Box 8146, N-0033 Oslo, Norway.
Eystein
E
Skjerve
Department of Animal Health, National Veterinary Institute, P.O. Box 750 dep, N-0106 Oslo, Norway.
Berit
B
Djønne
D000818:Animals; D002417:Cattle; D005002:Ethiopia / Q000453:epidemiology; D018740:Genetic Heterogeneity; D005838:Genotype; D018598:Minisatellite Repeats / Q000235:genetics; D058885:Multilocus Sequence Typing / Q000379:methods*; D009163:Mycobacterium bovis / Q000145:classification* / Q000235:genetics*; D014380:Tuberculosis, Bovine / Q000453:epidemiology* / Q000382:microbiology
Cattle; Ethiopia; Heterogeneity; MLVA; Mycobacterium bovis