Mainland sub-Saharan Africa Research Articles

Population size, HIV prevalence, and antiretroviral therapy coverage among key populations in sub-Saharan Africa: collation and synthesis of survey data, 2010–23

Key population HIV programmes in sub-Saharan Africa require epidemiological information to ensure equitable and universal access to effective services. We aimed to consolidate and harmonise survey data among female sex workers, men who have sex with men, people who inject drugs, and transgender people to estimate key population size, HIV prevalence, and antiretroviral therapy (ART) coverage for countries in mainland sub-Saharan Africa. Key population size estimates, HIV prevalence, and ART coverage data from 39 sub-Saharan Africa countries between 2010 and 2023 were collated from existing databases and verified against source documents. We used Bayesian mixed-effects spatial regression to model urban key population size estimates as a proportion of the gender-matched, year-matched, and area-matched population aged 15-49 years. We modelled subnational key population HIV prevalence and ART coverage with age-matched, gender-matched, year-matched, and province-matched total population estimates as predictors. We extracted 2065 key population size data points, 1183 HIV prevalence data points, and 259 ART coverage data points. Across national urban populations, a median of 1·65% (IQR 1·35-1·91) of adult cisgender women were female sex workers, 0·89% (0·77-0·95) were men who have sex with men, 0·32% (0·31-0·34) were men who injected drugs, and 0·10% (0·06-0·12) were women who were transgender. HIV prevalence among key populations was, on average, four to six times higher than matched total population prevalence, and ART coverage was correlated with, but lower than, the total population ART coverage with wide heterogeneity in relative ART coverage across studies. Across sub-Saharan Africa, key populations were estimated as comprising 1·2% (95% credible interval 0·9-1·6) of the total population aged 15-49 years but 6·1% (4·5-8·2) of people living with HIV. Key populations in sub-Saharan Africa experience higher HIV prevalence and lower ART coverage, underscoring the need for focused prevention and treatment services. In 2024, limited data availability and heterogeneity constrain precise estimates for programming and monitoring trends. Strengthening key population surveys and routine data within national HIV strategic information systems would support more precise estimates. UNAIDS, Bill & Melinda Gates Foundation, and US National Institutes of Health.

The age of the Tashinga Formation (Karoo Supergroup) in the Mid-Zambezi Basin, Zimbabwe and the first phytosaur from mainland sub-Saharan Africa

Correlations between continental sequences within the Karoo-aged basins of southern and eastern Africa are difficult due to the dearth of shared index fossils and a lack of radioisotopic dates for key formations. Here we describe four sites along the southeastern shoreline of Lake Kariba, Zimbabwe, within the Mid-Zambezi Basin, that yield material of phytosaurs (Archosauromorpha: Phytosauria) from within the informal Tashinga Formation (Upper Karoo Group). These phytosaur remains are the first to be recovered from sub-Saharan mainland Africa, representing a major geographic range extension for this group into high southern latitudes. Furthermore, an LA-ICPMS maximum depositional age of 209.2 ± 4.5 Ma (late Norian/early Rhaetian) derived from detrital zircons provides the first absolute age estimate for any of these sites. The phytosaurs are associated with lungfish and metoposaurid amphibians, forming part of a terrestrial-aquatic dominated biota, a previously undocumented biome from the Late Triassic of southern Africa.

Natural selection for the Duffy-null allele in the recently admixed people of Madagascar.

While gene flow between distantly related populations is increasingly recognized as a potentially important source of adaptive genetic variation for humans, fully characterized examples are rare. In addition, the role that natural selection for resistance to vivax malaria may have played in the extreme distribution of the protective Duffy-null allele, which is nearly completely fixed in mainland sub-Saharan Africa and absent elsewhere, is controversial. We address both these issues by investigating the evolution of the Duffy-null allele in the Malagasy, a recently admixed population with major ancestry components from both East Asia and mainland sub-Saharan Africa. We used genome-wide genetic data and extensive computer simulations to show that the high frequency of the Duffy-null allele in Madagascar can only be explained in the absence of positive natural selection under extreme demographic scenarios involving high genetic drift. However, the observed genomic single nucleotide polymorphism diversity in the Malagasy is incompatible with such extreme demographic scenarios, indicating that positive selection for the Duffy-null allele best explains the high frequency of the allele in Madagascar. We estimate the selection coefficient to be 0.066. Because vivax malaria is endemic to Madagascar, this result supports the hypothesis that malaria resistance drove fixation of the Duffy-null allele in mainland sub-Saharan Africa.

A national policy for malaria elimination in Swaziland: a first for sub-Saharan Africa

Swaziland is working to be the first country in mainland sub-Saharan Africa to eliminate malaria. The highest level of Swaziland's government recently approved a national elimination policy, which endorses Swaziland's robust national elimination strategic plan. This commentary outlines Swaziland's progress towards elimination as well as the challenges that remain, primarily around securing long-term financial resources and managing imported cases from neighbouring countries.

Unintended pregnancy in sub-Saharan Africa: magnitude of the problem and potential role of contraceptive implants to alleviate it

BackgroundUnintended pregnancies continue to burden many countries in sub-Saharan Africa. Our aim was to estimate the number of unintended pregnancies in the region and model the impact of expanding use of contraceptive implants at the expense of short-term hormonal birth control methods. Study DesignFor the 42 countries in mainland sub-Saharan Africa, we estimated current levels of unintended pregnancy, prevalence of hormonal contraceptive use and number of unintended pregnancies stemming from early discontinuation and typical method failure rates. Using a decision-analytic model, we estimated the potential impact of more widespread use of the contraceptive implant. ResultsEvery year in sub-Saharan Africa, approximately 14 million unintended pregnancies occur and a sizeable proportion is due to poor use of short-term hormonal methods. If 20% of the 17.6 million women using oral contraceptives or injectables wanted long-term protection and switched to the contraceptive implant, over 1.8 million unintended pregnancies could be averted over a 5-year period. ConclusionPoor patterns of short-term hormonal contraceptive use (high discontinuation rates and incorrect use) contribute significantly to the problem of unintended pregnancy in sub-Saharan Africa. More availability and widespread use of highly effective methods, such as the contraceptive implant, will improve reproductive health in the region.

Gaps in the protected area network for threatened Afrotropical birds

Protected areas established for wildlife conservation (IUCN category I–VI protected areas) or for forest and watershed conservation (forest reserves) across mainland sub-Saharan Africa have high biodiversity values. However, they fail to cover over half of the 106 threatened bird species, and thus leave these vulnerable to extinction. An analysis of Red List bird species that are not represented in existing reserves indicates gaps in the current network of protected areas, namely: Mt. Cameroon-Bamenda highlands (Cameroon), the Angolan scarp (Angola), the Drakensberg Highlands (South Africa), the Highveld (South Africa), the Eastern Arc Mountains (Tanzania), the eastern African coastal forest mosaic (Kenya and Tanzania), the Albertine Rift (Uganda, Rwanda, Burundi, eastern Democratic Republic of Congo and western Tanzania), and the Ethiopian Highlands. The addition of Forest Reserves to the existing protected areas closes some of the reservation gaps for threatened birds in Africa. We suggest that these Forest Reserves should be included within official lists of protected areas, and that National forestry authorities be encouraged to manage these areas. Publication of scientific articles showing the conservation value of Forest Reserves is needed to raise local and international support and funding.

How much of the vertebrate diversity of sub-Saharan Africa is catered for by recent conservation proposals?

A database documenting the distribution of birds, mammals, amphibians and snakes across 1° latitude and longitude squares of mainland sub-Saharan Africa provides an opportunity to quantify how many of these vertebrates are potentially catered for by recent large-scale conservation proposals. Sets of priority areas proposed by BirdLife International, the World Wildlife Fund (USA), the World Conservation Union and the World Wide Fund for Nature, Conservation International, and the World Resources Institute contain between 45 and 93% of 3752 species of birds, mammals, snakes and amphibians breeding in this area. Gaps in the coverage of vertebrates were found in all large-scale proposals, and these are mapped. Most of the conservation proposals perform better than random selection of similar sized areas of Africa, with the proposals focused on species performing more efficiently than schemes based on large areas of intact habitat or process-related criteria. Four of the schemes approach the performance of a complementarity-based algorithm that aims to maximise the number of species captured within a given area of land, and which has been widely advocated as a tool for conservation planning. The reasons for this are discussed and the relevance of the results for conservation planning at coarse and fine scales are explained.

Amblyomma geochelone, a new species of tick (Acari: Ixodidae) from the Madagascan ploughshare tortoise.

The male and female of Amblyomma geochelone n. sp. are described and illustrated by both scanning electron micrographs and line drawings. Specimens of this new tick species were recovered from the endangered ploughshare tortoise, Geochelone yniphora (Vaillant), in northwestern Madagascar. This relatively large tick is morphologically most similar to Amblyomma nuttalli Dönitz, which occurs in mainland sub-Saharan Africa where it mainly parasitizes other species of tortoises. However, several characters distinguish the new species from A. nuttalli including the scutal ornamentation in both sexes and the characteristic patterns of shallow grooves on the alloscutum of the female of A. geochelone. Because the adult stages of A. geochelone are almost certainly host specific ectoparasites of the ploughsh are tortoise, this new tick species is also probably endangered.

Two new Falcaustra Lane, 1915 species (Nematoda: Kathlaniidae) from African pipids (Anura)

Two new species of Falcaustra Lane, 1915 are the first to be reported in amphibians from mainland sub-Saharan Africa. Falcaustra puylaerti n. sp. occurs in hosts of the Xenopus (Silurana) tropicalis group in Sierra Leone, Togo and Nigeria. Falcaustra hinkeli n. sp. infects Xenopus (Xenopus) fraseri group hosts at localities in the Cameroon and the Democratic Republic of the Congo. Falcaustra hinkeli and F. puylaerti are probably sister species with respect to described congeners and can be differentiated from each other by the form of the cheilostomal structures, the morphometrics of the anterior body, and by a large difference in male spicule length. Both lack a precloacal pseudosucker and are separated from other Falcaustra spp. which share this characteristic by the pattern of male caudal papillae and by a cheilostomal ring with associated sclerotized elements and posteriorly directed projections. Evolutionary aspects of the host-parasite relationship are discussed. Although alternative hypotheses are possible, the distinctive cheilostomal morphology, the sister species relationship and the host specificity pattern of F. hinkeli and F. puylaerti are consistent with their having undergone an extended evolutionary association with the host genus.