African 2, a clonal complex of Mycobacterium bovis epidemiologically important in East Africa

Abstract

We have identified a clonal complex of Mycobacterium bovis isolated at high frequency from cattle in Uganda, Burundi, Tanzania, and Ethiopia. We have named this related group of M. bovis strains the African 2 (Af2) clonal complex of M. bovis. Af2 strains are defined by a specific chromosomal deletion (RDAf2) and can be identified by the absence of spacers 3 to 7 in their spoligotype patterns. Deletion analysis of M. bovis isolates from Algeria, Mali, Chad, Nigeria, Cameroon, South Africa, and Mozambique did not identify any strains of the Af2 clonal complex, suggesting that this clonal complex of M. bovis is localized in East Africa. The specific spoligotype pattern of the Af2 clonal complex was rarely identified among isolates from outside Africa, and the few isolates that were found and tested were intact at the RDAf2 locus. We conclude that the Af2 clonal complex is localized to cattle in East Africa. We found that strains of the Af2 clonal complex of M. bovis have, in general, four or more copies of the insertion sequence IS6110, in contrast to the majority of M. bovis strains isolated from cattle, which are thought to carry only one or a few copies.

FIG. 1.

Localization of the M. bovis Af1 and Af2 clonal complexes in Africa. (A) The four west-central African countries where Af1 strains were found to be dominant are shown in yellow, and the four east African countries where Af2 strains are highly prevalent are shown in green. Isolates of the Af1 clonal complex are very rare or not present in countries with the Af2 complex and vice versa. Countries where no Af1 or Af2 strains have been identified are labeled in gray, and countries where no isolates were studied are white. (B) Cattle distribution on the African continent (gray shaded area). (Reprinted from reference with permission from the publisher.).

FIG. 2.

IS6110 RFLP patterns, IS6110 copy numbers, RDAf2 deletion types, and spoligotypes of 12 M. bovis isolates from Africa and of the reference M. bovis BCG strain P3. The arrow marks a ∼1.9-kb restriction fragment commonly representing an IS6110 copy found in the DR region of M. bovis strains.