Abstract
Zoonoses disproportionately affect tropical communities and are associated with human modification and use of ecosystems. Effective management is hampered by poor ecological understanding of disease transmission and often focuses on human vaccination or treatment. Better ecological understanding of multi-vector and multi-host transmission, social and environmental factors altering human exposure, might enable a broader suite of management options. Options may include “ecological interventions” that target vectors or hosts and require good knowledge of underlying transmission processes, which may be more effective, economical, and long lasting than conventional approaches. New frameworks identify the hierarchical series of barriers that a pathogen needs to overcome before human spillover occurs and demonstrate how ecological interventions may strengthen these barriers and complement human-focused disease control. We extend these frameworks for vector-borne zoonoses, focusing on Kyasanur Forest Disease Virus (KFDV), a tick-borne, neglected zoonosis affecting poor forest communities in India, involving complex communities of tick and host species. We identify the hierarchical barriers to pathogen transmission targeted by existing management. We show that existing interventions mainly focus on human barriers (via personal protection and vaccination) or at barriers relating to Kyasanur Forest Disease (KFD) vectors (tick control on cattle and at the sites of host (monkey) deaths). We review the validity of existing management guidance for KFD through literature review and interviews with disease managers. Efficacy of interventions was difficult to quantify due to poor empirical understanding of KFDV–vector–host ecology, particularly the role of cattle and monkeys in the disease transmission cycle. Cattle are hypothesised to amplify tick populations. Monkeys may act as sentinels of human infection or are hypothesised to act as amplifying hosts for KFDV, but the spatial scale of risk arising from ticks infected via monkeys versus small mammal reservoirs is unclear. We identified 19 urgent research priorities for refinement of current management strategies or development of ecological interventions targeting vectors and host barriers to prevent disease spillover in the future.
Highlights
Zoonotic diseases disproportionately affect tropical communities, resulting in 26% of disability-adjusted life years lost to infectious diseases in lower middle-income countries [1,2,3]
The review of existing management practices and supporting empirical evidence for Kyasanur Forest Disease (KFD) identified 257 sources based on the keywords “KYASANUR” and an additional 67 sources (108 citations identified in total) based on the keywords “HAEMAPHYSALIS AND INDIA” (Table 1)
There is an urgent need to systematically review the natural repellents currently used by people in the Western Ghats [58] and test their efficacy compared to repellents recommended and distributed by the Indian Government (DHFWS), primarily dimethyl phthalate (DMP) oil, or those recommended by the World Health Organization (WHO) (Priority 1, Table 3)
Summary
Zoonotic diseases disproportionately affect tropical communities, resulting in 26% of disability-adjusted life years lost to infectious diseases in lower middle-income countries [1,2,3]. Many zoonotic disease control programmes utilise interventions that are focused on humans (e.g., vaccination and preventative drug treatment) Such conventional interventions are applied without understanding or consideration of the underlying ecological complexity and environmental settings in which spillover to humans occurs (spillover defined as transmission of a pathogen from a vertebrate animal to a human [5,10]). This is true of neglected zoonoses, for example, rabies, echinococcosis, leishmaniasis, and leprosy that primarily affect poor and marginalised populations in low-resource settings. There are widespread examples of effective disease control being hampered by a poor ecological evidence base or limited application of existing evidence into policy and practice (see reviews in [5,13])
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