Reviewing the ecological evidence base for management of emerging tropical zoonoses: Kyasanur Forest Disease in India as a case study

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.

1 Appendix S1 Contents   Table A: Empirical support for current KFD management practices, critical evaluation of whether management is justified, and relevant responses from key informant interviews (p1)     (2). The management type indicates whether the measure targets reservoir hosts, vectors or human hosts and which barrier to human spillover the management addresses (see Figure 1 in the main paper). We detail the main assumptions underpinning the management advice in terms of how such practice would reduce human transmission via infected tick bites, review the empirical support for the assumptions made. We detail responses from key informant interviews undertaken within the KFD endemic area, relating to how the current management recommendations for preventing human cases of KFD are being applied in the field in order to illustrate challenges or misconceptions associated with management practices. Finally, based on the balance of supporting empirical evidence, we recommend whether the current management practice is justified or could be improved. Covering up the body will prevent tick bites Yes, this is a well-endorsed practice for tick prevention. The World Health Organisation (WHO) recommend that clothing provides some protection if, for example, trousers are tucked into boots or socks and if shirts are tucked into trousers. However, there is strong evidence that clothes and clothing impregnated with repellents provide more protection than simply covering up (3).
"…Nobody [affected groups] wears shoes or anything and you apply the oil also, it is only going to be protective for 3 to 4 hours but these people go in the morning and come in the night, so, no oil is going to work…" Yes but further education is needed as this strategy alone will not prevent tick bites. The advice needs to be updated to highlight the need to cover the feet and ankles, and that clothing needs to form a continuous protective barrier by e.g. tucking trousers into socks, shirts into trousers. We recommend an integrated approachuse of protective clothing and tick repellents, checking the entire body daily after having been in tick-infested habitats, and prompt and effective removal of any attached ticks.  (4). Repellents may last longer if applied to clothing. However, both permethrin and DEET-based repellents are not be widely available in India and are prohibitively expensive. Local repellents vary in efficacy and there is currently no local guidance on when and how often to apply. DMP oil is distributed in areas where KFDV has previously been reported but is not very effective (5). Use of natural repellents has been reported in some areas of the Western Ghats (6) but efficacy is unknown. Repellents do not last more than a few hours when applied directly to the skin due to sweating, absorption and abrasion.
"…We ask them to apply DMP oil whenever they go to forest; I think few people… hardly 20% follow the precautions we suggest during outbreaks." "…Nobody [affected groups] wears shoes or anything and you apply the oil also, it is only going to be protective for 3 to 4 hours but these people go in the morning and come in the night, so, no oil is going to work…" "We are also trying to create habits on that but why should we do pressurise so much on them, we know that it is tick repellent and even mosquito repellent…, it is good if it is used regularly, even if you say all this, they don't use it. So, we have not understood why that gap still exists." Yes but further education is needed as this strategy alone will not prevent tick bites and the provided repellents are not very effective (DMP oil). We recommend an integrated approachuse of protective clothing and tick repellents, checking the entire body daily after having been in risky habitats, and prompt and effective removal of any attached ticks. Washing clothes and body will remove ticks Yes, the removal and washing of potentially contaminated clothes is a well endorsed recommendation. The WHO recommends that clothing should be removed and examined for the presence of ticks after a tick-infested area has been visited (3). However, there is evidence that ticks can survive even after washing clothes using washing machines and dryers (7,8). Most households in rural India hand-wash clothes in cold water, which will be ineffective at removing ticks. Washing the body may remove unattached ticks but will not remove attached ones. Moreover, current guidance is misleading because it leads to the widespread belief that taking a shower will remove ticks and hence reduce the need for other protective measures such as daily body checks, or use of repellents.
Yes regarding washing of clothes but this will not be completely effective. KFDV-infected monkeys are known to have high titres of virus (9) and so are likely to bear infected ticks. There is evidence that engorged ticks can move up to 30cm (10) but no empirical data exists on whether and how successfully interrupted feeding occurs in the species of tick most commonly found to transmit KFDV.
Partially-fed ticks infected with KFDV have been found at sites of monkeydeaths, but experimental transmission studies suggest that these have limited potential to transmit virus by feeding on a second host (11). Indeed, such interrupted feeding (intra-stadial feeding) has only rarely been recorded in other tick-borne disease systems and most often under laboratory conditions, for example in Rhipicephalus spp. (12,13). There is therefore no direct empirical evidence that locations of monkey deaths are hotspots of hostseeking infected ticks capable of transmitting the virus to humans.
Intervention is not currently justified, further empirical evidence is needed to address whether this is a valid management practice. Humans are mainly infected by nymphal ticks (14). For the dead monkey to constitute an infection risk to humans, either infected partially-fed nymphs must be leaving the dead monkey and searching for a new host (which assumes that intra-stadial feeding is occurring) or infected larvae, infected either by co-feeding or systemically, leave the dead monkey and then pose a risk to humans after they have moulted to become nymphs and seek new hosts. Management currently assumes that the focal risk arises from ticks leaving the dead monkey-if no questing behaviour is occurring in partially-fed nymphs then the likely rate of potentially infected and viable ticks arising from the host is no greater than for any suitable habitat where the monkey has spent time. Cattle are known to have high tick loads, including high loads of feeding adults and including H. spinigera, although the most common tick species found on cattle have not been incriminated in the KFDV transmission cycle (16,17). Hence, cattle may act both as an amplifier of tick numbers and as a disperser of ticks between habitats.
Handling of cattle was also identified as a significant risk factor associated with human KFD infection in a case-control study from the 2011-12 outbreak (18 (20,21).
Acaricides are used widely globally to reduce tick loads on cattle, however, effectiveness depends on the substance used, the species of ticks being targeted and on whether there is acaricideresistance in tick populations (see review by (22)).
"…When pet animals visit the forest, not only buffalo, rat and dog also, they have a chance to carry ticks on their body, those nymph stage ticks become adult. In this situation, veterinary department helps to control the adult tick by applying chemical [acaricides] on the animal body." "We said to people that do not leave the cattle to the forest because they carry ticks to home so that leads to disease. Vaccination of people in areas where KFD is known to be a risk will prevent human cases of the disease.
Yes. The vaccine is known to give protection against KFD if the correct dose procedure is followed (26,27). However, in recent outbreaks there is some evidence that vaccine efficacy was reduced compared to previous outbreaks and there have been problems with poor uptake of the vaccine in some areas (27,28).
"…And vaccine, first dose immunity is only 33% of immunity, second dose you get around 60%, booster dose you get around 80, after 5 doses, 5 years, you get about 90% immunity." "As far as KFD is concerned, no definite proper research has happened. We are struggling with the age-old vaccine, which was prepared in the 90s I think. We are going with the same. We don't know about the strain change…the virus... Even the research has not done. Even the cases which (who were) vaccinated fully, also were [re]infected. So, for that we need to do some research on whether the prevalence has changed it or not." "Only problem is with, in my view, the vaccine… vaccine is the main hitches.
Because the acceptance of that vaccine is not so… welcoming sign is not seen." One more point is the doses also. We need to give multiple doses to get what we need. To get some protection he/she needs to take full course. After that every year he/she needs to get booster dose for five years. Those are all hitches. I think one single injection that can protect the person for five years is needed. If we invent such vaccines then we can contain these measures, in my view." "..Where the vaccination is good, there should be less number of cases… but still we are seeing cases so… There that time we had a doubt whether the vaccination is working properly but I think it is not about the vaccine only -the timing of the vaccine is also important -like they have to take the vaccine at the specified time otherwise the potency of the vaccine would be decreased." Yes but targeting of areas could be improved beyond responding to outbreaks. Modelling ecological and social factors linked to human disease cases and barriers to vaccine uptake can provide more tailored risk maps and help target vaccination strategies. "…Even while burning monkey carcass, they handle with bare hands without proper PPE and precautions. They also won't be having precautions…" "…There used to be one group D, health inspector and medical officer and together they were supposed to do it. This was from the KFD unit…Before that we used to close with a local plastic sheet until they come, and after they come, they used to perform autopsy in the open and take it and burn it. With bare hands!" "Difficulties, they don't follow strictly whatever we say and we know that, it is difficult to follow because if we advise them not to go to forest, it is not possible as their livelihood depends on it…" "…One is the gap between acceptance of our services offered by health department and acceptance level of the beneficiaries, there is big gap, they are not ready to accept us, we are not able to make it out why it is so." Yes, although a more integrated approach is needed. People need educating to make them aware of risky habitats and behaviours, and why it is important to use protective clothing, repellents and undertake prompt removal of any attached ticks. Yes, human cases tend to be clustered and identification of cases has been used to target vaccination (28).
"…The handicap thing is, this season, so, it is rainy or it is very cold or there is no road, there is no vehicle to go and one house you visit and come back, it takes one day. So, the whole team, manpower is wasted to save one person, the one house, the other person affected and die and you can't identify them…" Yes, this is justified.
Surveillance (potential to inform multiple barriers) Tick surveillancesurveillance is undertaken within 5km of areas where human cases were recorded in the previous year (for up to five years) or within 5km of areas with current monkey deaths. Surveillance is not undertaken if current human cases are recorded.
Ticks are the known vectors for KFDV and hence surveillance of infection levels is useful for predicting the severity and locations of outbreaks.
Yes, many species of ticks, primarily Haemaphysalis species, are known to be vectors for KFDV and surveillance is used to predict spill-over in other systems (32,33).
"Mainly the lack of trained and experienced entomologists is the challenge. There is only one person (for the district possibly), for some people training has been given and there is a need to supervise them. So, they tell us to train to ASHA (health) workers and male health worker, but that is risky now. It is currently unclear, due to a lack of robust empirical data, whether monkeys are involved in the transmission of KFD to humans or whether they act as sentinels for high prevalence of infection in ticks that may have been infected from other hosts.
"…Lack of prompt reporting with monkey death occurring outside the forest reserves going unnoticed." "First is monkey deaths are not immediately reported so there is a chance of KFD spreading there. So, focus is not known first.
Even in Aralagudu what happened is we never had monkey deaths reported. Actually, they had monkey deaths but none of them were reported. So, we didn't know there was a focus of KFD over there. Until unless the cases started appearing. That is very important I feel that the monkey deaths need to be reported immediately.
"As per norm, we are not going to conduct the post mortem in that PHC area if suddenly positive case reports. Once positive report in human, ticks, or monkey within 5km PHC area, there is no question of repeated postmortem because we have to dispose the carcasses as early as possible. Important is health and forest, who burn it and health department spread the malathion." "Staff shortage affecting surveillance efforts." "It is a challenge. If, there is a monkey death, they (the vets or forest department or others) tell some other reason and burn it and dispose it but every monkey death should go to post mortem examination for cause of death and tissue analysis should be done and should be followed up for whether it is KFD or not…" "…Our group consist of 10 members in this taluk. If monkey death reported within 12      Table 2).
Tick sampling (by dragging and flagging) was undertaken from leaf litter collected as fodder, animal bedding and fertilizer for both fresh leaf litter and leaf litter that had been stored for varying lengths of time. Taxonomic identification and assessment of KFDV infection of tick samples is currently being undertaken.
A monkey sanctuary was planned to be set up within the Shimogga district, within endemic KFD area, to deal with problem monkeys (destroying crops and buildings): what if monkeys were infected with KFDV? What adverse effects could the monkey sanctuary have on other primates in the area?
Determine the role of dead and dying monkeys in generating hotspots of transmission. Need to determine role of live monkeys in KFDV transmission through infection of larvae via systemic circulation and/or supporting co-feeding between nymphs and larvae: quantify burdens, age structure, feeding history, and infection rates of ticks found on live monkeys, small mammals, and nearby habitats and people at the same time as measuring host infection levels. If monkeys are confirmed as important amplifying hosts for KFDV and contributing to transmission to humans, quantify their habitat associations, movement rates and interactions with people across agro-forest landscapes (Research Priorities 10, 11 and 13, Table 2).
Ticks were sampled in a robust, stratified way across habitats, including areas close to the sites of monkey deaths in order to ascertain whether monkeys represent hot-spots of infection risk or whether they may be acting as sentinels of risk across a broader area of habitat. Laboratory processing of samples (species identification and KFDV-testing of ticks) is currently being undertaken.

Key Questions identified via Whatsapp
Research that is needed to answer question and address knowledge gap Details of relevant data collection from MonkeyFeverRisk project Guidelines for Malathion dusting Determine the role of dead and dying monkeys in generating hotspots of transmission. Need to determine role of live monkeys in KFDV transmission through infection of larvae via systemic circulation and/or supporting co-feeding between nymphs and larvae: quantify burdens, age structure, feeding history, and infection rates of ticks found on live monkeys, small mammals, and nearby habitats and people at the same time as measuring host infection levels. If monkeys are confirmed as important amplifying hosts for KFDV and contributing to transmission to humans, quantify their habitat associations, movement rates and interactions with people across agro-forest landscapes (Research Priorities 10, 11 and 13, Table 2).
We did not produce guidelines for this. Current management guidelines stipulate that malathion dusting should be undertaken within 50 feet of an area where a monkey has died. However, this is predicated on the assumption that the area close to monkey deaths is the main focus of risk from infected tick bites, whereas it is possible that the scale of risk is broader.
In order to address this ticks were sampled in a robust, stratified way across habitats, including areas close to the sites of monkey deaths in order to ascertain whether monkeys represent hotspots of infection risk or whether they may be acting as sentinels of risk across a broader area of habitat. Laboratory processing of samples (species identification and KFDV-testing of ticks) is currently being undertaken. Request for certain Standard Operating Procedures from the stakeholders, for clinical management of KFD, for outbreak investigation, for monkey autopsy, for drag and flag for tick surveillance were requested.

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We have developed videos illustrating good practice for sampling ticks from the environment via dragging and flagging in order to provide guidance for tick surveillance. It is imperative to engage with stakeholders in order to establish the purposes of surveillance before devising clear protocols and surveillance strategies. For example, if the purpose of surveillance is to maximise the chances of finding an infected tick then should focus sampling within habitats with the greatest density of infected ticks. If the purpose is to better understand scale of risk and better understand disease-vectorhabitat associations then need stratified sampling across habitats and across a broader spatial scale than at the village level.