Conservation and agricultural intensification are two important pathways of large-scale land-use change in rural Africa. Besides their anticipated effects, these top-down strategies of future-making may have unknown and unintended consequences on human and animal well-being, in particular the emergence of novel infectious diseases. A large proportion of infectious diseases are transmitted primarily by blood-feeding arthropods and caused by so-called arthropod-borne viruses (arboviruses), e.g. Rift Valley fever virus. Arboviruses and their vectors are particularly sensitive to ecological changes, such as changes in the species composition of the flora and fauna. This project aims to understand how ecosystem diversity and complexity influences vector and virus populations in the light of large-scale land-use changes and socio-ecological trans¬formation in rural Africa.
The presence of a great variety of infectious pathogens detected in the first funding phase may be responsible for high levels of uncertainties in shaping the future. This calls for more detailed analyses of risks and perceptions of arboviral diseases by different communities in KAZA and KRV, key among them pastoralists, using a holistic One Health approach. We will investigate in greater detail how land-use changes will affect the prevalence and impact of vector-borne diseases in the KAZA and KRV regions of Africa.
Research Regions:Namibia and Kenya
Keywords: Virology, Ecology of Land Use
How do social-ecological transformations and land-use changes affect vector populations and concomitant viral pathogens they transmit?
How does ecosystem diversity influences vectors and virus populations?
How does the taxonomic diversity of vectors, host, and vegetation affect pathogen transmission dynamics?
Our methodological approach relies on a combination of field and laboratory analyses. Diverse traps are used to collect mosquito vectors in conserved areas (with varying vegetation and elephant densities) and in agricultural areas (with and without invasive plants present). Mosquito species are identified to species based on morphological criteria. Samples are screened for arbovirus infections using broad-range generic RT-PCR assays followed by molecular characterization of detected viruses. Longevity of vectors and host meal analyses (blood and plant meal sources) are also investigated.
We found that elephant densities in KAZA affected mosquito species composition as well as mosquito densities. Similarly, in the KRV land-use changes caused by invasive plants like Parthenium, Prosopis and Lantana had a strong effect on mosquito community composition. Several pathogenic arboviruses, like West Nile virus that can cause encephalitis in humans were found in Cx. univittatus mosquitoes in KAZA. In total, we detected ten strains of WNV which grouped in two different phylogenetic clades. Our data indicate that two different variants were simultaneously circulating in Namibia and suggest that WNV may contribute to unknown disease aetiologies. In addition, novel orthobunya- and orbiviruses that are likely to cause malformations and abortions in livestock, were detected in mosquitoes and midges in KAZA. The presence of such a great variety of infectious pathogens may be responsible for high levels of uncertainties in shaping the future.
Heiko Guggemos, Matthias Fendt, Christian Hieke, Verena Heyde, John K. E. Mfune, Christian Borgemeister, Sandra Junglen: (2021) Simultaneous circulation of two West Nile virus lineage 2 clusters and Bagaza virus in the Zambezi region, Namibia. PLoS Neglected Tropical Diseases 15(4): e0009311. DOI
Outlook for phase II (2022 - 2025)
In the previous project phase (2018-2021), we addressed how future-making is influenced by unplanned and unintended side-effects of changes in vector populations and concomitant arboviral infections focusing on large-scale land-use changes (mainly agricultural intensification in KRV and conservation in KAZA). In the second funding phase, we will explore whether we can improve our understanding of the complex links between environmental, animal, and human health by using a One Health approach. In brief, we will explore the links between land-use changes and diseases in the most important and prevalent livestock species (cattle) by studying various biotic (e.g. cattle density and migration pattern, disease infection rates, vector and small mammal species composition, abundance of invasive plants, vegetation structure and diversity) and abiotic (temperature, rainfall and humidity, also in respect to climate change) factors, as well as taking into account the socio-cultural behavior (e.g. risk perception, awareness) of pastoralists. This will be addressed in an interdisciplinary fashion together with projects A01, A02, A04, A05, B01 and C07.