From Intact to Highly Degraded Mitochondrial Genes in Trypanosoma vivax: New Insights into Introduction from Africa and Adaptation to Exclusive Mechanical Transmission in South America

Trypanosoma vivax displays distinct mitochondrial genomes: intact in Africa and degraded in South America. This finding, formerly reported from four isolates, suggested an association between mitochondrial mutations and adaptation to exclusive mechanical transmission outside Africa, circumventing mitochondrial activity essential for cyclical transmission by tsetse flies. Here, we characterized the mitochondrial ND7 and COIII genes in 25 South American isolates of T. vivax from livestock from Argentina, Brazil, Colombia, Ecuador, and Venezuela, as well as in 11 African isolates from Mozambique, Ethiopia, Uganda, Nigeria, and Burkina Faso from tsetse flies, antelopes, and cattle. Phylogenetic inference supported the lineages TVV (Trypanosoma vivax vivax) and TVL (Trypanosoma vivax-like), predominant in South America/West Africa and East Africa, respectively. Both ND7 and COIII genes were intact in all African TVV and TVL isolates and, for the first time, in 10 South American isolates from Brazil. Remaining South American isolates exhibited some degree of gene erosion, including ~142 bp deletion at the 3′ end of ND7 disclosed in Venezuela and Colombia, ~163 bp deletion at the 3′ end of ND7 in Brazil and Argentina, and ~750 bp deletion from the 5′ end of ND7 to the 3′ end of COIII in Venezuela. Comprehensive analyses of whole mitochondrial genomes from additional South American and African isolates are crucial for formulating reliable hypotheses regarding the origin, absence, and rapid mitochondrial degradation observed in South American T. vivax.