Abstract
Risk assessment regarding the distribution of malaria vectors and environmental variables underpinning their distribution under changing climates is crucial towards malaria control and eradication. On this basis, we used Maximum Entropy (MaxEnt) Model to estimate the potential future distribution of major transmitters of malaria in Nigeria—Anopheles gambiae sensu lato and its siblings: Anopheles gambiae sensu stricto, and Anopheles arabiensis under low and high emissions scenarios. In the model, we used mosquito occurrence data sampled from 1900 to 2010 alongside land use and terrain variables, and bioclimatic variables for baseline climate 1960–1990 and future climates of 2050s (2041–2060) and 2070s (2061–2080) that follow RCP2.6 and RCP8.5 scenarios. The Anopheles gambiae species are projected to experience large shift in potential range and population with increased distribution density, higher under high emissions scenario (RCP8.5) and 2070s than low emission scenario (RCP2.6) and 2050s. Anopheles gambiae sensu stricto and Anopheles arabiensis are projected to have highest invasion with 47–70% and 10–14% percentage increase, respectively in Sahel and Sudan savannas within northern states in 2041–2080 under RCP8.5. Highest prevalence is predicted for Humid forest and Derived savanna in southern and North Central states in 2041–2080; 91–96% and 97–99% for Anopheles gambiae sensu stricto, and 67–71% and 72–75% for Anopheles arabiensis under RCP2.6 and RCP8.5, respectively. The higher magnitude of change in species prevalence predicted for the later part of the 21st century under high emission scenario, driven mainly by increasing and fluctuating temperature, alongside longer seasonal tropical rainfall accompanied by drier phases and inherent influence of rapid land use change, may lead to more significant increase in malaria burden when compared with other periods and scenarios during the century; especially in Humid forest, Derived savanna, Sahel and Sudan savannas.
Highlights
Noticeable changes have been projected to occur in potential distribution of the dominant malaria vector species complex, An. gambiae s.l. and its two major siblings under the chosen climate change scenarios within bioclimatic and ecological domains in the tropical country— Nigeria
This is expected to translate into large range expansions and high prevalence with increased distribution density within Humid forest (36.51% and 39.70% under RCP8.5) and (19.19% and 23.30% under RCP2.6), Derived savanna (48.60% and 52.26% under RCP8.5) and (43.69% and 43.03% under RCP2.6), Sudan savanna (37.66% and 44.31% under RCP8.5) and (28.02% and 26.66% under RCP2.6), and Sahel savanna (47.725 and 54.13% under RCP8.5) and (24.99% and 22.96% under RCP2.6) in 2050s and 2070s, respectively (Table 1; Fig 3)
The Mid Altitude zone is projected to become less suitable for the An. gambiae complex under RCP2.6 with percentage decrease of 1.58% in 2050s and 1.44% in 2070s, and 0.66% in 2050s under RCP8.5, the Mid Altitude areas of Jos plateau, Mambilla plateau and highlands in Adamawa, Borno and Cross River states (Table 1; Fig 3; S1 Fig)
Summary
An. gambiae species under low and high emissions scenarios in Nigeria diseases, human immunodeficiency virus / acquired immunodeficiency syndrome (HIV/ AIDS) and tuberculosis, among countries in the tropical region of the world [2]. Almost half of all global cases were accounted for by five tropical countries: Nigeria (25%), Democratic Republic of the Congo (11%), Mozambique (5%), India (4%) and Uganda (4%) [1,3]. Climate change resulting from the enhanced greenhouse effect [4] together with the direct effect of increased urbanisation / land use [5] and population drivers, is expected to produce changes in species distribution including that of malaria vectors in tropical ecosystems [6,7,8,9]. Shifts and increased prevalence induced by anthropogenic drivers [10,11] on vectors distribution may exacerbate human exposure to malaria infection [12]
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