Genetically discrete populations of Trypanosoma congolense from livestock on the Kenyan coast

Twenty-seven stocks of Nannomonas trypanosomes isolated from livestock in 1982 on a ranch at Kilifi on the Kenyan coast were characterized by isoenzyme electrophoresis and by the abilities of the parasite's DNA to hybridize to two repetitive sequence DNA probes. Allthe Kilifi stocks which were examined had isoenzyme patterns which were markedly different from the 75 patterns previously described from 78 stocks of Trypanosoma congolense. On average only 15% of the enzyme bands present in the Kilifi stocks were present in those stocks of T. congolense which had previously been surveyed for isoenzymes. The DNA from all the Kilifi stocks which had been examined for isoenzymes hybridized with only the repetitive sequence probe isolated from a clone of a Kilifi stock. In contrast, the DNA from all 27 Kilifi stocks failed to hybridize with a repetitive sequence probe isolated from a clone from a different stock of T. congolense. Thus, the trypanosomes in all the Kilifi stocks examined were both phenotypically and genotypically discrete. These genetically discrete trypanosomes have also been detected in 2 stocks isolated from livestock from another location on the Kenyan coast. The results show that there is a wide range of genetic heterogeneity within the trypanosomes currently classified as T. congolense. We suggest that the limits of this genetic heterogeneity could represent incipient speciatio

The structure of a conserved telomeric region associated with variant antigen loci in the blood parasite Trypanosoma congolense

African trypanosomiasis is a vector-borne disease of humans and livestock caused by African trypanosomes (Trypanosoma spp.). Survival in the vertebrate bloodstream depends on antigenic variation of Variant Surface Glycoproteins (VSGs) coating the parasite surface. In T. brucei, a model for antigenic variation, monoallelic VSG expression originates from dedicated VSG expression sites (VES). Trypanosoma brucei VES have a conserved structure consisting of a telomeric VSG locus downstream of unique, repeat sequences, and an independent promoter. Additional protein-coding sequences, known as “Expression Site Associated Genes (ESAGs)”, are also often present and are implicated in diverse, bloodstream-stage functions. Trypanosoma congolense is a related veterinary pathogen, also displaying VSG-mediated antigenic variation. A T. congolense VES has not been described, making it unclear if regulation of VSG expression is conserved between species. Here, we describe a conserved telomeric region associated with VSG loci from long-read DNA sequencing of two T. congolense strains, which consists of a distal repeat, conserved noncoding elements and other genes besides the VSG; although these are not orthologous to T. brucei ESAGs. Most conserved telomeric regions are associated with accessory minichromosomes, but the same structure may also be associated with megabase chromosomes. We propose that this region represents the T. congolense VES, and through comparison with T. brucei, we discuss the parallel evolution of antigenic switching mechanisms, and unique adaptation of the T. brucei VES for developmental regulation of bloodstream-stage genes. Hence, we provide a basis for understanding antigenic switching in T. congolense and the origins of the African trypanosome VES

Effect of climate smart agriculture technologies on crop yields: Evidence from potato production in Kenya

Climate change is one of the current global issues of concern given that it is affecting agricultural production. Sub-Saharan Africa (SSA), which frequently experiences severe weather and natural disasters, is particularly vulnerable to climate change. Even though numerous measures are being promoted to mitigate climate change in SSA, little evidence exists regarding the adoption of climate-smart agriculture (CSA) technologies in potato farming and its effect on yield. CSA is widely acknowledged as a crucial technique for farmers to adapt to climate change and raise agricultural productivity. This study investigated the effects of CSA technology adoption among potato farmers in Kenya. A descriptive survey was adopted. A multistage sampling technique was used to randomly select 350 potato farming households in Nyandarua County. Data was collected using a questionnaire and interview techniques. Propensity Score Matching (PSM) was used to evaluate the effects of CSA technologies on potato yields. The results indicated that on average potato farmers adopted 8 out of the 18 CSA technologies. The PSM results indicated that the adoption of CSA technologies improved potato yields. Adoption of seed management technologies enhanced potato yield by 61 % followed by soil nutrient management, crop improvement practices, seed management, and crop protection techniques by 50 %, 41 %, 40 %, and 39 %, respectively. This implies that smallholder farmers' adoption of climate-smart technologies is critical for increasing and maintaining potato yield. However, adopting water management technologies like water harvesting and irrigation negatively affected potato yield. The study discusses the implications of these findings