East Africa | EPFL Graph Search

East Africa, Eastern Africa, or East of Africa, is the eastern subregion of the African continent. In the United Nations Statistics Division scheme of geographic regions, 10-11-(16*) territories make up Eastern Africa: Scientific consensus states the region of East Africa is where anatomically modern humans first evolved circa 200,000 years ago before migrating northwards out of Africa. Due to the historical Omani Empire and colonial territories of the British East Africa Protectorate and German East Africa, the term East Africa is often (especially in the English language) used to specifically refer to the area now comprising the three countries of Kenya, Tanzania, and Uganda. However, this has never been the convention in many other languages, where the term generally had a wider, strictly geographic context and therefore typically included Djibouti, Eritrea, Ethiopia, and Somalia. *Tanzania, Kenya, Uganda, Rwanda, Burundi, Democratic Republic of Congo and South Sudan are members

First quantitative survey delineates the distribution of chimpanzees in the Eastern Central African Republic

Stéphane Joost, Estelle Rochat

Vast, pristine ecosystems and their biodiversity are vanishing globally at frightening speed, but many large tracts of wilderness have not yet been systematically inventoried and important natural populations of threatened species remain poorly characterized. The forest-savanna ecotone of the Eastern Central African Republic (CAR) is one such poorly studied area. Using camera traps, transect walks and collected fecal samples, we provide the first quantitative survey of chimpanzees (Pan troglodytes) in this region previously classified as a highly important chimpanzee conservation unit. In contrast to species distribution models and expert predictions, we did not find any evidence of chimpanzees in the large and remote forest blocks west of the Chinko River despite considerable search effort. Our study thus highlights the limitations of relying solely on remote sensing data to predict the presence or absence of endangered species and illustrates the necessity of extensive field surveys to accurately assess occurrence and density in remote areas. However, we did discover a sizeable and reproducing population of chimpanzees east of the Chinko River. Based on a density of 0.81 chimpanzees/km2 in closed canopy forest that we inferred from nest count data, we estimate 910 weaned chimpanzees to inhabit the Chinko Nature Reserve (CNR) and further predict additional 2700 individuals in adjacent, unmanaged hunting zones and reserves. According to microsatellite data, these chimpanzees genetically cluster with P. t. schweinfurthii populations in East Africa. Conservation action and appropriate management plans are urgently needed to protect this important population and to prevent heavily-armed nomadic pastoralists from the Sahel, illegal miners, as well as elephant and meat poachers, from irretrievably destroying the natural vegetation and local biodiversity of the area.

Elsevier2017

Spatial Areas of Genotype Probability of Cattle Genomic Variants Involved in the Resistance to East Coast Fever: A Tool to Predict Future Disease-Vulnerable Geographical Regions

Stéphane Joost, Estelle Rochat, Elia Vajana

East Coast Fever (ECF) is a livestock disease caused by Theileria parva, a protozoan transmitted by the vector tick Rhipicephalus appendiculatus. This disease causes high mortality in cattle populations of Central and Eastern Africa, especially in exotic breeds. Here, we highlight genomic regions likely involved into tolerance/resistance mechanisms against ECF, and we introduce the estimation of their Spatial Area of Genotype Probability (SPAG) to delimit areas where the concerned genotypes are predicted to be present. During the NEXTGEN project, 803 Ugandan cattle were geo-referenced and genotyped (54K SNPs), while 532 tick occurrences were retrieved from a published database. To get a proxy of the parasite selective pressure, we used WorldClim bioclimatic variables to model vector ecological niche. Landscape genomics models were then used to detect cattle genotypes associated with vector probability of presence, and to estimate their SPAGs. Finally, climate change scenarios for 2070 were considered to compare the predicted shift in the vector niche with the estimated current SPAG. The analysis revealed two main areas of presence of possibly resistance-related genotypes, one South and one East of Lake Victoria. Climate change will probably shift tick niche southwards in the Eastern regions of Lake Victoria, inducing a critical area that currently does not show the candidate genotypes, but where disease will likely spread in the future. The combined use of SPAGs and niche maps could therefore facilitate the identification of regions of concern and to direct future targeted breeding schemes.

2016

Population Genomics of Mycobacterium leprae Reveals a New Genotype in Madagascar and the Comoros

Charlotte Avanzi, Andrej Benjak, Philippe Busso, Stewart Cole, Thyago Leal Calvo, Pushpendra Singh

Human settlement of Madagascar traces back to the beginning of the first millennium with the arrival of Austronesians from Southeast Asia, followed by migrations from Africa and the Middle East. Remains of these different cultural, genetic, and linguistic legacies are still present in Madagascar and other islands of the Indian Ocean. The close relationship between human migration and the introduction and spread of infectious diseases, a well-documented phenomenon, is particularly evident for the causative agent of leprosy, Mycobacterium leprae. In this study, we used whole-genome sequencing (WGS) and molecular dating to characterize the genetic background and retrace the origin of the M. leprae strains circulating in Madagascar (n = 30) and the Comoros (n = 3), two islands where leprosy is still considered a public health problem and monitored as part of a drug resistance surveillance program. Most M. leprae strains (97%) from Madagascar and Comoros belonged to a new genotype as part of branch 1, closely related to single nucleotide polymorphism (SNP) type 1D, named 1D-Malagasy. Other strains belonged to the genotype 1A (3%). We sequenced 39 strains from nine other countries, which, together with previously published genomes, amounted to 242 genomes that were used for molecular dating. Specific SNP markers for the new 1D-Malagasy genotype were used to screen samples from 11 countries and revealed this genotype to be restricted to Madagascar, with the sole exception being a strain from Malawi. The overall analysis thus ruled out a possible introduction of leprosy by the Austronesian settlers and suggests a later origin from East Africa, the Middle East, or South Asia.

2020

First quantitative survey delineates the distribution of chimpanzees in the Eastern Central African Republic

Stéphane Joost, Estelle Rochat

Elsevier2017