scholarly journals The African mosquito-borne diseasosome: Geographical patterns and range expansion

2021 ◽  
Author(s):  
Tovi Lehmann ◽  
Cedric Kouam ◽  
Joshua Woo ◽  
Mawlouth Diallo ◽  
Richard Wilkerson ◽  
...  
Keyword(s):  
Species Richness ◽  
Range Expansion ◽  
System Analysis ◽  
Mosquito Species ◽  
Central Africa ◽  
Domestic Animals ◽  
Sub Saharan Africa ◽  
Eastern Africa ◽  
Striking Similarity ◽  
Disease Emergence

Mosquito-borne diseases (MBDs) such as malaria, dengue, and Rift Valley fever threaten public health and food security globally. Despite their cohesive nature, they are typically treated as distinct entities. Applying biological system analysis to the African MBDs from a One Health perspective, we provide the first biogeographic description of the African mosquito fauna corresponding with the pathogens they transmit. After compiling records accumulated over a century, we find that there are 677 mosquito species in Africa, representing 16 genera, and 151 mosquito-borne pathogens (MBPs) circulating primarily among wild tetrapods, dominated by viruses (95) and protozoans (47). We estimate that reported MBPs represent ~1% of the actual number. Unlike mosquitoes, African arboviruses and mammalian plasmodia represent a higher share of the World's total based on the area- species richness relationship (P<0.0001), explaining the disproportional large share of global MBPs that originated from Africa. Species richness of African mosquitoes and MBPs are similarly concentrated along the equator, peaking in central Africa, with a secondary ridge along eastern Africa. Moderate diversity and low endemicity in mosquitoes across the Sahel reveals a fauna with high propensity for long-range migration. Regional differences in species richness, endemicity, and composition agreed with country-based results. The composition of mosquitoes and MBPs separates sub-Saharan Africa from north Africa, in accordance with the Palearctic and Afrotropical faunal realms, and west and central Africa are clustered together distinctly from the cluster of eastern and southern Africa. With ~25% of the species occupying a single country, ~50% in 1-3 countries and <5% found in >25 countries, the typical ranges of both mosquitoes and MBPs are surprisingly small. The striking similarity in diversity and especially in range distributions of mosquitoes and MBPs suggest that most MBPs are transmitted by one or few narrow-range mosquito vectors. Exceptionally widespread mosquito species (e.g., Ae. aegypti, Cx. quinquefasciatus, and 10 Anopheles species) feed preferentially on people and domestic animals, and nearly half are windborne migrants. Likewise, exceptionally widespread MBPs are transmitted between people or domestic animals and are vectored by one or more of the aforementioned widespread mosquitoes. Our results suggest that few MBPs have undergone a dramatic range expansion, after adapting to people or domestic animals as well as to exceptionally-widespread mosquitoes. During the intermediate phase of range expansion, MBPs extend their vector and vertebrate host ranges with a concomitant gradual increase in geographical range. Because range size may serve as a marker of the phase of range expansion, ranking the African MBPs according to range, we identified several MBPs that pose elevated risk for disease emergence (e.g., Wesselsbron virus). Taken together, our database, approach, and results can help improve MBD surveillance and lead to a better understanding of disease emergence. This knowledge has the potential to improve capacity to prevent and mitigate new and emerging MBD threats.

scholarly journals Modelling potential range expansion of an underutilised food security crop in Sub-Saharan Africa

2021 ◽  
Author(s):  
Olef Koch ◽  
Wendawek Abebe Mengesha ◽  
Samuel Pironon ◽  
Pagella Tim ◽  
Ian Ondo ◽  
...  
Keyword(s):  
Food Security ◽  
Range Expansion ◽  
Lake Victoria ◽  
Sub Saharan Africa ◽  
Eastern Africa ◽  
Small Scale ◽  
Potential Range ◽  
Niche Modelling ◽  
Ethical Implications ◽  
Sub Saharan

Abstract Despite substantial growth in global agricultural production, food and nutritional insecurity is rising in Sub-Saharan Africa. Identification of underutilised indigenous crops with useful food security traits may provide part of the solution. Enset (Ensete ventricosum) is a perennial banana relative with cultivation restricted to southwestern Ethiopia, where high productivity and harvest flexibility enables it to provide a starch staple for ~20 million people. An extensive wild distribution suggests that a much larger region may be climatically suitable for cultivation. Here we use ensemble ecological niche modelling to predict the potential range for enset cultivation within southern and eastern Africa. We find contemporary bioclimatic suitability for a 12-fold range expansion, equating to 21.9% of crop land and 28.4% of the population in the region. Integration of crop wild relative diversity, which has broader climate tolerance, could enable a 19-fold expansion, particularly to dryer and warmer regions. Whilst climate change may cause a 37% – 52% reduction in potential range by 2070, large centres of suitability remain in the Ethiopian Highlands, Lake Victoria region and the Drakensberg Range. We combine our bioclimatic assessment with socioeconomic data to identify priority areas with high population density, seasonal food deficits and predominantly small-scale subsistence agriculture, where integrating enset may be particularly feasible and deliver climate resilience. When incorporating the genetic potential of wild populations, enset cultivation might prove feasible for an additional 87.2 - 111.5 million people, 27.7 – 33 million of which are in Ethiopia outside of enset’s current cultivation range. Finally, we consider explanations why enset cultivation has not expanded historically, and ethical implications of expanding previously underutilised species.

Patterns of species richness in two African-centered, aridity-adapted flightless weevil lineages (Coleoptera: Curculionoidea)

Zootaxa ◽  
2017 ◽  
Vol 4323 (4) ◽  
pp. 593 ◽  
Author(s):  
TAYLOR HICKMAN ◽  
ŞERBAN PROCHEŞ ◽  
SYD RAMDHANI
Keyword(s):  
Species Richness ◽  
Plant Diversity ◽  
Cape Floristic Region ◽  
Sub Saharan Africa ◽  
Eastern Africa ◽  
African Origin ◽  
Succulent Karoo ◽  
Multiple Factors ◽  
The Family ◽  
Sub Saharan

Weevils (Coleoptera: Curculionoidea) represent a remarkable proportion of global biodiversity, yet studies addressing their biogeography remain scarce. The arid parts of sub-Saharan Africa harbour several interesting weevil lineages, the most spectacular being the larger flightless weevils such as the Microcerinae and Brachycerus. Here we map the species richness of these two groups to identify hotspots in their diversity, and make inferences regarding the factors that may have contributed to the observed patterns. Exceptional richness values in both groups are found in southern Africa, and more specifically in the Nama Karoo, which is unremarkable in terms of plant diversity. By comparisons, plant diversity hotspots such as the Succulent Karoo and the Cape Floristic Region appear to have high, but not exceptional, weevil richness. Species richness levels were also high in the grassland and savanna areas of south-eastern Africa, which are not arid. The representation of genera considered here and their closest relatives, suggest an African origin for both lineages. This, combined with recent insights into weevil evolution, raise the possibility that advanced weevils as a whole (the family Curculionidae) originated in Africa and that some of its earliest offshoots survived and subsequently diversified here thanks to multiple factors, relating to climate and plant diversity alike. 

scholarly journals Should seasonal rainfall forecasts be used for flood preparedness?

2017 ◽  
Vol 21 (9) ◽  
pp. 4517-4524 ◽  
Author(s):  
Erin Coughlan de Perez ◽  
Elisabeth Stephens ◽  
Konstantinos Bischiniotis ◽  
Maarten van Aalst ◽  
Bart van den Hurk ◽  
...  
Keyword(s):  
Central Africa ◽  
Sub Saharan Africa ◽  
Seasonal Rainfall ◽  
Eastern Africa ◽  
Total Rainfall ◽  
Climate Services ◽  
Dry Spells ◽  
Flood Preparedness ◽  
Sub Saharan ◽  
Seasonal Rainfall Forecasts

Abstract. In light of strong encouragement for disaster managers to use climate services for flood preparation, we question whether seasonal rainfall forecasts should indeed be used as indicators of the likelihood of flooding. Here, we investigate the primary indicators of flooding at the seasonal timescale across sub-Saharan Africa. Given the sparsity of hydrological observations, we input bias-corrected reanalysis rainfall into the Global Flood Awareness System to identify seasonal indicators of floodiness. Results demonstrate that in some regions of western, central, and eastern Africa with typically wet climates, even a perfect tercile forecast of seasonal total rainfall would provide little to no indication of the seasonal likelihood of flooding. The number of extreme events within a season shows the highest correlations with floodiness consistently across regions. Otherwise, results vary across climate regimes: floodiness in arid regions in southern and eastern Africa shows the strongest correlations with seasonal average soil moisture and seasonal total rainfall. Floodiness in wetter climates of western and central Africa and Madagascar shows the strongest relationship with measures of the intensity of seasonal rainfall. Measures of rainfall patterns, such as the length of dry spells, are least related to seasonal floodiness across the continent. Ultimately, identifying the drivers of seasonal flooding can be used to improve forecast information for flood preparedness and to avoid misleading decision-makers.

scholarly journals Mozambican genetic variation provides new insights into the Bantu expansion

2019 ◽  
Author(s):  
Armando Semo ◽  
Magdalena Gayà-Vidal ◽  
Cesar Fortes-Lima ◽  
Bérénice Alard ◽  
Sandra Oliveira ◽  
...  
Keyword(s):  
Iron Age ◽  
Genetic Relationships ◽  
Central Africa ◽  
Sub Saharan Africa ◽  
Eastern Africa ◽  
Nucleotide Polymorphisms ◽  
Wide Range ◽  
The Rich ◽  
Sub Saharan ◽  
Genetic Substructure

AbstractThe Bantu expansion, which started in West Central Africa around 5,000 BP, constitutes a major migratory movement involving the joint spread of peoples and languages across sub-Saharan Africa. Despite the rich linguistic and archaeological evidence available, the genetic relationships between different Bantu-speaking populations and the migratory routes they followed during various phases of the expansion remain poorly understood. Here, we analyze the genetic profiles of southwestern and southeastern Bantu-speaking peoples located at the edges of the Bantu expansion by generating genome-wide data for 200 individuals from 12 Mozambican and 3 Angolan populations using ∼1.9 million autosomal single nucleotide polymorphisms. Incorporating a wide range of available genetic data, our analyses confirm previous results favoring a “late split” between West and East Bantu speakers, following a joint passage through the rainforest. In addition, we find that Bantu speakers from eastern Africa display genetic substructure, with Mozambican populations forming a gradient of relatedness along a North-South cline stretching from the coastal border between Kenya and Tanzania to South Africa. This gradient is further associated with a southward increase in genetic homogeneity, and involved minimum admixture with resident populations. Together, our results provide the first genetic evidence in support of a rapid North-South dispersal of Bantu peoples along the Indian Ocean Coast, as inferred from the distribution and antiquity of Early Iron Age assemblages associated with the Kwale archaeological tradition.

scholarly journals Modelling potential range expansion of an underutilised food security crop in Sub-Saharan Africa

2021 ◽  
Author(s):  
Olef Koch ◽  
Wendawek A. Mengesha ◽  
Samuel Pironon ◽  
Tim Pagella ◽  
Ian Ondo ◽  
...  
Keyword(s):  
Food Security ◽  
Range Expansion ◽  
Lake Victoria ◽  
Sub Saharan Africa ◽  
Eastern Africa ◽  
Small Scale ◽  
Potential Range ◽  
Niche Modelling ◽  
Ethical Implications ◽  
Sub Saharan

Despite substantial growth in global agricultural production, food and nutritional insecurity is rising in Sub-Saharan Africa. Identification of underutilised indigenous crops with useful food security traits may provide part of the solution. Enset (Ensete ventricosum) is a perennial banana relative with cultivation restricted to southwestern Ethiopia, where high productivity and harvest flexibility enables it to provide a starch staple for ~20 million people. An extensive wild distribution suggests that a much larger region may be climatically suitable for cultivation. Here we use ensemble ecological niche modelling to predict the potential range for enset cultivation within southern and eastern Africa. We find contemporary bioclimatic suitability for a 12-fold range expansion, equating to 21.9% of crop land and 28.4% of the population in the region. Integration of crop wild relative diversity, which has broader climate tolerance, could enable a 19-fold expansion, particularly to dryer and warmer regions. Whilst climate change may cause a 37% - 52% reduction in potential range by 2070, large centres of suitability remain in the Ethiopian Highlands, Lake Victoria region and the Drakensberg Range. We combine our bioclimatic assessment with socioeconomic data to identify priority areas with high population density, seasonal food deficits and predominantly small-scale subsistence agriculture, where integrating enset may be particularly feasible and deliver climate resilience. When incorporating the genetic potential of wild populations, enset cultivation might prove feasible for an additional 87.2 - 111.5 million people, 27.7 - 33 million of which are in Ethiopia outside of enset's current cultivation range. Finally, we consider explanations why enset cultivation has not expanded historically, and ethical implications of expanding previously underutilised species.

scholarly journals Along the Indian Ocean Coast: Genomic Variation in Mozambique Provides New Insights into the Bantu Expansion

2019 ◽  
Vol 37 (2) ◽  
pp. 406-416 ◽  
Author(s):  
Armando Semo ◽  
Magdalena Gayà-Vidal ◽  
Cesar Fortes-Lima ◽  
Bérénice Alard ◽  
Sandra Oliveira ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Iron Age ◽  
Genetic Relationships ◽  
Central Africa ◽  
Genomic Variation ◽  
Sub Saharan Africa ◽  
Eastern Africa ◽  
Nucleotide Polymorphisms ◽  
Wide Range ◽  
The Indian Ocean

Abstract The Bantu expansion, which started in West Central Africa around 5,000 BP, constitutes a major migratory movement involving the joint spread of peoples and languages across sub-Saharan Africa. Despite the rich linguistic and archaeological evidence available, the genetic relationships between different Bantu-speaking populations and the migratory routes they followed during various phases of the expansion remain poorly understood. Here, we analyze the genetic profiles of southwestern and southeastern Bantu-speaking peoples located at the edges of the Bantu expansion by generating genome-wide data for 200 individuals from 12 Mozambican and 3 Angolan populations using ∼1.9 million autosomal single nucleotide polymorphisms. Incorporating a wide range of available genetic data, our analyses confirm previous results favoring a “late split” between West and East Bantu speakers, following a joint passage through the rainforest. In addition, we find that Bantu speakers from eastern Africa display genetic substructure, with Mozambican populations forming a gradient of relatedness along a North–South cline stretching from the coastal border between Kenya and Tanzania to South Africa. This gradient is further associated with a southward increase in genetic homogeneity, and involved minimum admixture with resident populations. Together, our results provide the first genetic evidence in support of a rapid North–South dispersal of Bantu peoples along the Indian Ocean Coast, as inferred from the distribution and antiquity of Early Iron Age assemblages associated with the Kwale archaeological tradition.

scholarly journals Should seasonal rainfall forecasts be used for flood preparedness?

2017 ◽  
Author(s):  
Erin Coughlan de Perez ◽  
Elisabeth Stephens ◽  
Konstantinos Bischiniotis ◽  
Maarten van Aalst ◽  
Bart van den Hurk ◽  
...  
Keyword(s):  
Central Africa ◽  
Sub Saharan Africa ◽  
Seasonal Rainfall ◽  
Eastern Africa ◽  
Total Rainfall ◽  
Climate Services ◽  
West And Central Africa ◽  
Flood Preparedness ◽  
Sub Saharan ◽  
Seasonal Rainfall Forecasts

Abstract. In light of strong encouragement for disaster managers to use climate services for flood preparation, we question whether seasonal rainfall forecasts should indeed be used as indicators of the likelihood of flooding. Here, we investigate the primary drivers of flooding at the seasonal timescale across sub-Saharan Africa. Given the sparsity of hydrological observations, we input bias-corrected reanalysis rainfall into the Global Flood Awareness System to identify seasonal indicators of floodiness. Results demonstrate that in wet climates, even a perfect tercile forecast of seasonal total rainfall would provide little to no indication of the seasonal likelihood of flooding. The number of extreme events within a season shows the highest correlations with floodiness consistently across regions. Otherwise, results vary across climate regimes: floodiness in arid regions in Southern and Eastern Africa shows the strongest correlations with seasonal average soil moisture and seasonal total rainfall. Floodiness in wetter climates of West and Central Africa and Madagascar shows the strongest relationship with measures of the intensity of seasonal rainfall. Measures of rainfall patterns, such as the length of dry spells, are least related to seasonal floodiness across the continent. Ultimately, identifying the drivers of seasonal flooding can be used to improve forecast information for flood preparedness, and avoid misleading decision-makers.

scholarly journals Impact of seasonality and malaria control interventions on Anopheles density and species composition from three areas of Uganda with differing malaria endemicity

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Henry Ddumba Mawejje ◽  
Maxwell Kilama ◽  
Simon P. Kigozi ◽  
Alex K. Musiime ◽  
Moses Kamya ◽  
...  
Keyword(s):  
Species Composition ◽  
Vector Control ◽  
Malaria Control ◽  
Mosquito Species ◽  
Density Ratio ◽  
Indoor Residual Spraying ◽  
Sub Saharan Africa ◽  
Malaria Vector Control ◽  
Vector Density ◽  
Llin Distribution

Abstract Background Long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are the malaria control interventions primarily responsible for reductions in transmission intensity across sub-Saharan Africa. These interventions, however, may have differential impact on Anopheles species composition and density. This study examined the changing pattern of Anopheles species in three areas of Uganda with markedly different transmission intensities and different levels of vector control. Methods From October 2011 to June 2016 mosquitoes were collected monthly using CDC light traps from 100 randomly selected households in three areas: Walukuba (low transmission), Kihihi (moderate transmission) and Nagongera (high transmission). LLINs were distributed in November 2013 in Walukuba and Nagongera and in June 2014 in Kihihi. IRS was implemented only in Nagongera, with three rounds of bendiocarb delivered between December 2014 and June 2015. Mosquito species were identified morphologically and by PCR (Polymerase Chain Reaction). Results In Walukuba, LLIN distribution was associated with a decline in Anopheles funestus vector density (0.07 vs 0.02 mosquitoes per house per night, density ratio [DR] 0.34, 95% CI: 0.18–0.65, p = 0.001), but not Anopheles gambiae sensu stricto (s.s.) nor Anopheles arabiensis. In Kihihi, over 98% of mosquitoes were An. gambiae s.s. and LLIN distribution was associated with a decline in An. gambiae s.s. vector density (4.00 vs 2.46, DR 0.68, 95% CI: 0.49–0.94, p = 0.02). In Nagongera, the combination of LLINs and multiple rounds of IRS was associated with almost complete elimination of An. gambiae s.s. (28.0 vs 0.17, DR 0.004, 95% CI: 0.002–0.009, p < 0.001), and An. funestus sensu lato (s.l.) (3.90 vs 0.006, DR 0.001, 95% CI: 0.0005–0.004, p < 0.001), with a less pronounced decline in An. arabiensis (9.18 vs 2.00, DR 0.15 95% CI: 0.07–0.33, p < 0.001). Conclusions LLIN distribution was associated with reductions in An. funestus s.l. in the lowest transmission site and An. gambiae s.s. in the moderate transmission site. In the highest transmission site, a combination of LLINs and multiple rounds of IRS was associated with the near collapse of An. gambiae s.s. and An. funestus s.l. Following IRS, An. arabiensis, a behaviourally resilient vector, became the predominant species, which may have implications for malaria vector control activities. Development of interventions targeted at outdoor biting remains a priority.

scholarly journals Within-Season Changes in Land-Use Impact Pest Abundance in Smallholder African Cassava Production Systems

Insects ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 269 ◽  
Author(s):  
Andrew Kalyebi ◽  
Sarina Macfadyen ◽  
Andrew Hulthen ◽  
Patrick Ocitti ◽  
Frances Jacomb ◽  
...  
Keyword(s):  
Land Use ◽  
Bemisia Tabaci ◽  
Large Scale ◽  
Production Systems ◽  
Smallholder Farmers ◽  
Negative Relationship ◽  
Central Africa ◽  
Sub Saharan Africa ◽  
Smallholder Farming ◽  
Manihot Esculenta Crantz

Cassava (Manihot esculenta Crantz), an important commercial and food security crop in East and Central Africa, continues to be adversely affected by the whitefly Bemisia tabaci. In Uganda, changes in smallholder farming landscapes due to crop rotations can impact pest populations but how these changes affect pest outbreak risk is unknown. We investigated how seasonal changes in land-use have affected B. tabaci population dynamics and its parasitoids. We used a large-scale field experiment to standardize the focal field in terms of cassava age and cultivar, then measured how Bemisia populations responded to surrounding land-use change. Bemisia tabaci Sub-Saharan Africa 1 (SSA1) was identified using molecular diagnostics as the most prevalent species and the same species was also found on surrounding soybean, groundnut, and sesame crops. We found that an increase in the area of cassava in the 3–7-month age range in the landscape resulted in an increase in the abundance of the B. tabaci SSA1 on cassava. There was a negative relationship between the extent of non-crop vegetation in the landscape and parasitism of nymphs suggesting that these parasitoids do not rely on resources in the non-crop patches. The highest abundance of B. tabaci SSA1 nymphs in cassava fields occurred at times when landscapes had large areas of weeds, low to moderate areas of maize, and low areas of banana. Our results can guide the development of land-use strategies that smallholder farmers can employ to manage these pests.

Pre-Katangan geochronology of Zambia and adjacent parts of Central Africa

1968 ◽  
Vol 5 (3) ◽  
pp. 621-628 ◽  
Author(s):  
J. R. Vail ◽  
N. J. Snelling ◽  
D. C. Rex
Keyword(s):  
Lake Tanganyika ◽  
Central Africa ◽  
New Age ◽  
Orogenic Belt ◽  
Eastern Africa ◽  
Sedimentary Sequence ◽  
Precambrian Rocks ◽  
Late Precambrian ◽  
Orogenic Belts ◽  
Age Determinations

The significance of new age determinations on pre-Katangan (Late Precambrian) rocks and minerals from Zambia and adjacent parts of Tanzania and Rhodesia is discussed. In northwestern Rhodesia, the Lomagundi-Piriwiri sediments were deposited between 2500 and 2000 m.y. ago and were folded along meridional trends at circa 1940 m.y. A later episode of folding and metamorphism along similar trends occurred about 1700 m.y. ago, but only affected the western part of the sedimentary sequence (the Piriwiri Series). This latter date is comparable to that which appears to characterize the Tumbide trend, a N- to NE-trending fold system, in Zambia.In Zambia the Tumbide trend is the oldest tectonic episode preserved in the basement and is found only in isolated blocks and cores into which later tectonisms have not penetrated. The dominant pre-Katangan tectonism is represented by the NE to ENE Irumide trend. Such tectonic trends are particularly well developed in the Irumide Orogenic Belt of northern Zambia and adjacent Tanzania. Age determinations set a younger limit of circa 900 m.y. to this trend and the existence of an Irumide Cycle between about 1600 and 900 m.y. is suggested. The possibility that the relatively unmetamorphosed sediments of the Upper Plateau Series and Abercorn Sandstones at the southern end of Lake Tanganyika, the Mafingi Series of northern Malawi, and the Konse Series of Tanzania, represent near-contemporaneous platform deposition associated with the Irumide belt is considered.From this and other recent studies the distribution of orogenic belts in central and eastern Africa can be revised and a number of features of their pattern and inter-relationships noted.

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