In their recent review on diversity of African tsetse fly-transmitted trypanosomes, Tait et al. [1xTrypanosome genetics: populations, phenotypes and diversity. Tait, A. et al. Vet. Parasitol. 2011; 181: 61–68Crossref | PubMed | Scopus (10)See all References[1] suggest that genetic diversity of Trypanosoma vivax, a major pathogen of African and South American cattle, is limited. This is primarily based on DNA microsatellite analysis of 31 T. vivax isolates from a single area in The Gambia [2xTrypanosoma vivax displays a clonal population structure. Duffy, C.W. et al. Int. J. Parasitol. 2009; 39: 1475–1483Crossref | PubMed | Scopus (24)See all References[2]. However, this assessment ignores evidence from several studies that have used isoenzymes [3xA comparison of the isoenzymes of Trypanosoma (Duttonella) vivax isolates from East Africa and West Africa. Fasogbon, A.I. et al. Int. J. Parasitol. 1990; 20: 389–394Crossref | PubMed | Scopus (25)See all References[3], DNA microsatellites [4xNew molecular marker for Trypanosoma (Duttonella) vivax identification. Morlais, I. et al. Acta Trop. 2001; 80: 207–213Crossref | PubMed | Scopus (25)See all References, 5xIdentification of Trypanosoma vivax subtypes isolated from cattle and goats using microsatellite markers. Biryomumaisho, S. et al. Vet. Arhiv. 2011; 81: 13–24See all References] and more recently sequence data [6xThe use of specific and generic primers to identify trypanosome infections of wild tsetse flies in Tanzania by PCR. Malele, I. et al. Infect. Genet. Evol. 2003; 3: 271–279Crossref | PubMed | Scopus (37)See all References, 7xPhylogenetic analysis of Trypanosoma vivax supports the separation of South American/West African from East African isolates and a new T. vivax like genotype infecting a nyala antelope from Mozambique. Rodrigues, A.C. et al. Parasitology. 2008; 135: 1317–1328Crossref | PubMed | Scopus (16)See all References, 8xNew Trypanosoma (Duttonella) vivax genotypes from tsetse flies in East Africa. Adams, E.R. et al. Parasitology. 2010; 137: 641–650Crossref | PubMed | Scopus (20)See all References, 9xThe taxonomic and phylogenetic relationships of Trypanosoma vivax from South America and Africa. Cortez, A.P. et al. Parasitology. 2006; 133: 159–169Crossref | PubMed | Scopus (45)See all References] that have revealed high levels of genetic diversity within this species, particularly in East Africa. A partial T. vivax 18S rDNA sequence, obtained from an infected tsetse fly in Tanzania had greatest similarity to that of a West African T. vivax isolate, yet diverged by 14% [6xThe use of specific and generic primers to identify trypanosome infections of wild tsetse flies in Tanzania by PCR. Malele, I. et al. Infect. Genet. Evol. 2003; 3: 271–279Crossref | PubMed | Scopus (37)See all References[6]; two novel genotypes were discovered in wild antelope from Mozambique, one of which caused severe disease in a goat [7xPhylogenetic analysis of Trypanosoma vivax supports the separation of South American/West African from East African isolates and a new T. vivax like genotype infecting a nyala antelope from Mozambique. Rodrigues, A.C. et al. Parasitology. 2008; 135: 1317–1328Crossref | PubMed | Scopus (16)See all References[7], and three diverse genotypes were discovered in tsetse flies from Tanzania [8xNew Trypanosoma (Duttonella) vivax genotypes from tsetse flies in East Africa. Adams, E.R. et al. Parasitology. 2010; 137: 641–650Crossref | PubMed | Scopus (20)See all References[8]. Indeed, analysis of glycosomal glyceraldehyde phosphate dehydrogenase (gGAPDH) gene sequences suggests that T. vivax diversity is similar to that of Trypanosoma congolense [8xNew Trypanosoma (Duttonella) vivax genotypes from tsetse flies in East Africa. Adams, E.R. et al. Parasitology. 2010; 137: 641–650Crossref | PubMed | Scopus (20)See all References[8], a species where the different strains (forest, savannah and kilifi) arguably represent different species.The limited genetic diversity found in The Gambia [2xTrypanosoma vivax displays a clonal population structure. Duffy, C.W. et al. Int. J. Parasitol. 2009; 39: 1475–1483Crossref | PubMed | Scopus (24)See all References[2] reflects the results of a study which found isolates with identical gGAPDH gene sequences from across West Africa (The Gambia, Nigeria and Cameroon) and South America [8xNew Trypanosoma (Duttonella) vivax genotypes from tsetse flies in East Africa. Adams, E.R. et al. Parasitology. 2010; 137: 641–650Crossref | PubMed | Scopus (20)See all References[8]. By contrast, considerable polymorphism (11 distinct alleles) was identified in 31 T. vivax infections in field-collected tsetse flies from Cameroon, using primers targeting a region that contains a microsatellite sequence [4xNew molecular marker for Trypanosoma (Duttonella) vivax identification. Morlais, I. et al. Acta Trop. 2001; 80: 207–213Crossref | PubMed | Scopus (25)See all References[4]. The results from these studies are not directly comparable, as they used different genotyping techniques; DNA microsatellites evolve quickly, whereas the gGAPDH gene has a slow evolutionary rate and is generally used for resolving species-level relationships (e.g. [10xPatterns of co-evolution between trypanosomes and their hosts deduced from ribosomal RNA and protein-coding gene phylogenies. Hamilton, P.B. et al. Mol. Phylogenet. Evol. 2007; 43: 15–25Crossref | Scopus (93)See all References[10]). It is therefore difficult to assess the true genetic diversity of T. vivax in West Africa, particularly as T. vivax has not been extensively sampled from wild mammals, tsetse flies and other biting flies in the region, which could potentially harbor greater diversity. Additionally, the primer sets used for initial identification [11xSensitive detection of trypanosomes in tsetse-flies by DNA amplification. Masiga, D.K. et al. Int. J. Parasitol. 1992; 22: 909–918Crossref | PubMed | Scopus (203)See all References[11] in the study of Duffy et al. [2xTrypanosoma vivax displays a clonal population structure. Duffy, C.W. et al. Int. J. Parasitol. 2009; 39: 1475–1483Crossref | PubMed | Scopus (24)See all References[2] lack the ability to detect divergent T. vivax genotypes [4xNew molecular marker for Trypanosoma (Duttonella) vivax identification. Morlais, I. et al. Acta Trop. 2001; 80: 207–213Crossref | PubMed | Scopus (25)See all References[4], and this may also be the case for the primer sets used for microsatellite genotyping that were designed from genomic sequences from a West African strain [2xTrypanosoma vivax displays a clonal population structure. Duffy, C.W. et al. Int. J. Parasitol. 2009; 39: 1475–1483Crossref | PubMed | Scopus (24)See all References[2]. By contrast, the studies that have revealed the diverse genotypes in East Africa have used ‘generic’ primers, designed to amplify DNA from a wide range of trypanosome species, and therefore may be more likely to pick up novel genotypes [7xPhylogenetic analysis of Trypanosoma vivax supports the separation of South American/West African from East African isolates and a new T. vivax like genotype infecting a nyala antelope from Mozambique. Rodrigues, A.C. et al. Parasitology. 2008; 135: 1317–1328Crossref | PubMed | Scopus (16)See all References, 9xThe taxonomic and phylogenetic relationships of Trypanosoma vivax from South America and Africa. Cortez, A.P. et al. Parasitology. 2006; 133: 159–169Crossref | PubMed | Scopus (45)See all References, 12xA novel, high throughput technique for species identification reveals a new species of tsetse-transmitted trypanosome related to the Trypanosoma brucei subgenus, Trypanozoon. Hamilton, P.B. et al. Infect. Genet. Evol. 2008; 8: 26–33Crossref | PubMed | Scopus (33)See all References, 13xTrypanosomes are monophyletic: evidence from genes for glyceraldehyde phosphate dehydrogenase and small subunit ribosomal RNA. Hamilton, P.B. et al. Int. J. Parasitol. 2004; 34: 1393–1404Crossref | PubMed | Scopus (110)See all References].It is clear that our knowledge of the diversity of T. vivax is limited. Understanding the true diversity of this important parasite and its significance in terms of diagnosis, disease, differential drug response and the evolution of resistance to chemotherapeutic treatments will require broader surveys and improved genotyping techniques.