Biology subjects

Killeen, G. F.

Publications and source records attributed to Killeen, G. F..

5 recordsLinked to original sources

bioRxiv2026

Potential impacts of supplementing next generation long-lasting insecticidal nets with household-scale micro-mosaic deployment of indoor residual spraying with insecticides upon rates of incipient resistance trait emergence and selection

Prolonged use of the few insecticide classes available for long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) has driven widespread physiological resistance of malaria vector mosquitoes to this limited arsenal of active ingredients. However, recent innovations like next-generation LLINs (NG-LLINs) containing two complementary insecticides and new insecticide classes for IRS offer new opportunities for pre-emptive resistance management by deploying more diversified actives as mixtures, combinations, rotations or mosaics. Here a deterministic model of mosquito foraging behaviour was formulated to predict the probabilities of deterrence, mortality or successful feeding across repeated feeding attempts in scenarios with different combinations of NG-LLINs and/or IRS micro-mosaics with varying levels of insecticide diversification between neighbouring houses. Final fates were classified based on whether or not the mosquito eventually died or successfully fed, and whether the latter occurred indoors or outdoors after exposure to zero, one or several IRS insecticides. The primary outcome was the probability that a single F mosquito carrying a novel resistance trait to a new IRS insecticide successfully feeds, survives and reproduces, thereby establishing those traits within the population. The secondary outcome was the selection coefficient governing the spread of such novel resistance traits from the F generation onwards. For highly anthropophagic and endophagic vectors like Anopheles funestus, combining NG-LLINs with IRS micro-mosaics using two insecticides may reduce emergence rates for novel resistance traits against IRS insecticides by approximately 2 to 2.5-fold, mainly through direct killing by NG-LLINs, although exposure to both IRS actives when forced to visit multiple houses also contributes to a lesser extent. However, such resistance management benefits are fundamentally constrained by outdoor feeding behaviours that limit or completely prevent indoor insecticide exposure. Increasing IRS micro-mosaic insecticide diversity beyond two actives is unlikely to further dampen resistance emergence rates because few mosquitoes survive long enough without feeding to encounter several IRS treatments. Once a resistance trait becomes established in the vector population, selection coefficients remain consistently high enough to force the spread of those traits, regardless of intervention combination. For more exophagic, zoophagic vectors like An. arabiensis, NG-LLINs plus IRS micro-mosaics are not expected to provide any meaningful resistance management benefit because frequent outdoor feeding, often on animals, allows them to largely avoid insecticide exposure altogether. Exclusively indoor-focused vector control strategies may not satisfactorily slow insecticide resistance emergence and spread, so new outdoor protection measures that close these coverage gaps with complementary insecticides will be needed.

genetics↗

bioRxiv2025

The Role of Resident Custodian Communities in Devolved Forest Conservation Lessons from a retrospective, mixed-method observational study of the Ifakara-Lupiro-Mang'ula Wildlife Management Area in Southern Tanzania

The establishment of Wildlife Management Areas (WMAs) in Tanzania aims to involve local communities in conserving natural resources on their land, while also yielding sustainable socio-economic benefits. WMAs are established on community lands to ensure the protection of wildlife and their habitats along the fringes of centrally managed protected areas like National Parks and Game Reserves. A recent cross-sectional study of the Ifakara-Lupiro-Mangula (ILUMA) WMA in the south of the country suggests that small, authorized fishing camps established legally inside the designated conservation area act as resident custodian communities who actively collaborate with the WMA to enforce conservation of the surrounding forest ecosystem. Here a retrospective cartographic analysis of a longitudinal series of surveys of human, livestock and wildlife activities across ILUMA between 2022 and 2025 reveal a clear increase of illegal timber harvesting in forested areas around custodian communities immediately after they were displaced by extreme floods in 2024. Furthermore, recorded narratives of resident members of these fishing camps indicate that charcoal burners, timber harvesters and even game meat poachers have taken advantage of such absences to exploit the forest undetected. These observations further support the view that resident custodian communities living within WMAs may play vital roles in conservation efforts, particularly in settings where financial resources for enforcement of regulations are limited.

ecology↗

bioRxiv2024

Stakeholder perspectives on the effectiveness of the Ifakara-Lupiro-Mang'ula Wildlife Management Area in Southern Tanzania

In Tanzania, Wildlife Management Areas (WMAs) are established on village lands, usually adjacent to centrally managed core protected areas like national parks and game reserves, and managed in a devolved manner by local village authorities. WMAs are intended to conserve wildlife outside such core protected areas, while also providing opportunities for local communities to derive tangible benefits from wildlife and other natural resources. This study evaluates the perceived effectiveness of the Ifakara-Lupiro-Mangula (ILUMA) WMA in southern Tanzania among various stakeholders, focusing on its conservation, livelihoods and community development functions. Based on thematic analysis of perspectives shared by stakeholders at national, regional, district and village levels through in-depth interviews, focus group discussions and a public stakeholders meeting, the WMA was considered to have succeeded to only a very modest extent in achieving its intended goals. Essentially all participants narrated that the area is heavily encroached by human activities, including livestock grazing, agriculture, illegal fishing, meat poaching, deforestation, charcoal burning, timber harvesting and even permanent settlements. Contributing factors include a recently growing influx of agro-pastoralist immigrants, top-down political interference, financial constraints, financial mismanagement, limited resources for operations, lack of conservation education, investors or government support, and recent displacement of encroachment pressure from newly upgraded, centrally-managed protected areas nearby. To ensure future success and sustainability of the WMA, participants recommended enhancing stakeholder involvement and community participation in WMA management, improved collaboration with nearby centrally-managed protected areas for implementing operations, overhaul of the WMA constitution to reflect current best practices, building capacity among relevant village leaders and elected WMA representatives and initiating conservation education initiatives for the local community. Overall, the WMA should explore alternative income sources beyond tourism, to ensure direct benefits for the community member through sustainable, carefully-regulated access to natural resources, and resolve ongoing conflict over land use between the long-established villages that govern ILUMA and agro-pastoralists immigrants who have moved into the area more recently.

ecology↗

bioRxiv2024

Blood host preferences and competitive inter-species dynamics within an African malaria vector species complex inferred from signs of animal activity around aquatic larval habitats.

The dual-specialized behavioural adaptions of Anopheles arabiensis, to feed readily upon either people or cattle, enable it to thrive and mediate persistent residual malaria transmission across much of Africa, despite widespread use of long-lasting insecticidal nets (LLINs). Indeed, LLIN scale up has often resulted in it dominating the more efficient but vulnerable malaria vector Anopheles gambiae, its sibling species within a complex of the latter name. However, the feeding behaviours and competitive relationships of An. arabiensis with other sibling species in well conserved natural ecosystems, where its known preferred hosts are scarce or absent, remain largely unexplored. Potential aquatic habitats were surveyed for An. gambiae complex larvae across a gradient of natural ecosystem integrity in southern Tanzania, encompassing fully domesticated human settlements, a partially encroached Wildlife Management Area (WMA), and well conserved areas of the recently gazetted Nyerere National Park (NNP) before substantive development of tourist access or accommodation. Direct observations, tracks, spoor and other signs of human, livestock or wild animal activity around these water bodies were recorded as indirect indicators of potential blood source availability. While only An. arabiensis was found in fully domesticated ecosystems, its non-vector sibling species An. quadriannulatus occurred in conserved areas and dominated the most intact natural ecosystems. Proportions of larvae identified as An. arabiensis were positively associated with human and/or cattle activity and negatively associated with distance inside NNP and away from human settlements. Proportions of An. quadriannulatus were positively associated with activities of impala and bushpig, implicating both as likely preferred blood hosts. While abundant impala and lack of humans or cattle in intact acacia savannah within NNP apparently allowed it to dominate An. arabiensis, presence of bushpig seemed to provide it with a foothold in miombo woodlands of the WMA, despite encroachment by people and livestock. While this antelope and suid are essentially unrelated, both are non- migratory residents of small home ranges with perennial surface water, representing preferred hosts for An. quadriannulatus that are widespread across extensive natural ecosystems all year round. Despite dominance of An. quadriannulatus in well-conserved areas, An. arabiensis was even found in absolutely intact environments >40km inside NNP, suggesting it can survive on blood from one or more unidentified wild species. While self-sustaining refuge populations of An. arabiensis inside conservation areas, supported by wild blood hosts that are fundamentally beyond the reach of insecticidal interventions targeted at humans or their livestock, may confound efforts to eliminate this key malaria vector, they might also enable insecticide resistance management strategies that could restore the effectiveness of pyrethroids in particular.

ecology↗

bioRxiv2021

Heritability and phenotypic plasticity of biting time behaviors in the major African malaria vector Anopheles arabiensis

Use of Insecticide Treated Nets for malaria control has been associated with shifts in mosquito vector feeding behavior including earlier and outdoor biting on humans. The relative contribution of phenotypic plasticity and heritability to these behavioural shifts is unknown. Elucidation of the mechanisms behind these shifts is crucial for anticipating impacts on vector control. We used a novel portable semi-field system (PSFS) to experimentally measure heritability of biting time in the malaria vector Anopheles arabiensis in Tanzania. In PSFS assays, the biting time of F2 offspring (early: 18:00-21:00, mid: 22:00-04:00 or late: 05:00-07:00) was significantly associated with that of their wild-caught F0 grandmothers, corresponding to an estimated heritability of 0.30 (95% CI: 0.20, 0.41). F2 from early-biting F0 were more likely to bite early than F2 from mid or late late-biting F0. Similarly, the probability of biting late was higher in F2 derived from mid and late-biting F0 than from early-biting F0. Our results indicate that variation in biting time is attributable to additive genetic variation. Selection can therefore act efficiently on mosquito biting times, highlighting the need for control methods that target early and outdoor biting mosquitoes.

evolutionary biology↗