Vector-borne Disease Outbreaks Research Articles

ICE-VDOP: an integrated clustering and ensemble machine learning methods for an enhanced vector-borne disease outbreak prediction using climatic variables

ICE-VDOP: an integrated clustering and ensemble machine learning methods for an enhanced vector-borne disease outbreak prediction using climatic variables

Effective partnership and in-country resource mobilization in Sudan for cVDPV2 outbreak response amid multiple emergencies in 2020-2021.

During 2020 and immediately prior to the COVID-19 pandemic, Sudan was experiencing multiple emergencies including violence, seasonal flooding, and vector-borne disease outbreaks. After more than ten years since its last case of wild poliovirus, Sudan declared a circulating vaccine-derived poliovirus type 2 (cVDPV2) outbreak on 9 August 2020. cVDPV2 outbreak response data and programme documents of the Federal Ministry of Health and WHO were reviewed. Surveillance data was verified through WHO-recommended procedures for detecting and characterizing polioviruses from stool and sewage samples collected from acute flaccid paralysis (AFP) cases and the environment. This outbreak in Sudan led to a total of 58 confirmed cases of cVDPV2 from 15 of the 18 states. Two nationwide vaccination campaigns were held to increase immunity of children under-five against poliovirus type 2. Funding challenges were overcome by intense additional resource mobilization from in-country sources. The funding gap was bridged from domestic resources (49%) sourced through GPEI partners, and in-country humanitarian funding mechanisms. During an outbreak response and challenge of funding shortfall, mobilizing in-country resources is possible through coordinated approaches, regular communication with partners, disaggregation of needs, and matching in-kind and financial support to fill gaps. A cVDPV2 outbreak requires a fast, resourced, and quality response to stop virus circulation.

Control of emerging and re-emerging zoonotic and vector-borne diseases in countries of the Eastern Mediterranean Region

Despite improvements in the detection and control of infectious diseases, many new pathogens are emerging and re-emerging in various parts of the world. Most of these emerging and re-emerging infections are of zoonotic origin, which highlights the importance of the human–animal interface. Similarly, the rate of vector-borne diseases has increased recently due to changes in human habitats, climate change, deforestation, changes in food production practices, and increased population movement. The risk of spread of these zoonotic and vector-borne diseases is higher in the Eastern Mediterranean Region (EMR) of the World Health Organization due to its topography and geopolitical situation, fragile health systems, complex humanitarian emergencies, and, in some countries, other socioeconomic risk factors. Many countries in the region have reported outbreaks of zoonotic and vector-borne diseases over the last few decades, and some of these diseases have spread to other WHO regions as well. Avian influenza A (H5N1) and Middle East respiratory syndrome coronavirus (MERS-CoV) are among the greatest threats to global health security and both viruses are endemic in the EMR. Countries in the EMR have made significant progress toward the control of zoonotic and vector-borne diseases in recent years, and prevention, preparedness, and response capacities have been improved. However, there are still many challenges associated with the control of these diseases in the EMR, particularly in countries facing humanitarian emergencies. In this paper, we present the current situation of emerging and re-emerging infections in the EMR and discuss progress, challenges, and ways forward.

Optimised neem oil-bilayer tablets: A safe, effective and stable tool for the prevention of vector-borne disease outbreaks by Aedes albopictus

The control of mosquito breeding is an essential step towards the reduction of vector-borne disease outbreaks. Synthetic larvicidal agents produce resistance in vectors and cause safety concerns in humans, animals and aquatic species. The drawback of synthetic larvicides opened a new avenue for natural larvicidal agents, but poor dosage accuracy, need for frequent applications, low stability and sustainability are the major challenges with them. Hence, this investigation aimed to overcome those drawbacks by developing bilayer tablets loaded with neem oil to prevent mosquito breeding in stagnant water. The optimised batch of neem oil-bilayer tablets (ONBT) had 65%w/w hydroxypropyl methylcellulose K100M and 80%w/w ethylcellulose in its composition. After the completion of 4th week, 91.98 ± 0.871% azadirachtin was released from the ONBT, which was followed by a subsequent drop in the in vitro release. ONBT reported long-term larvicidal efficacy (>75%) and a good deterrent effect which was better than neem oil-based marketed products. The acute toxicity study on a non-target fish model (Poecilia reticulata), OECD Test No.203 confirmed the safety of the ONBT on non-target aquatic species. The accelerated stability studies predicted a good stability profile for the ONBT. The neem oil-based bilayer tablets can be used as an effective tool for the control of vector-borne diseases in society. The product may be a safe, effective and eco-friendly replacement for the existing synthetic as well as natural products in the market.

Monitoring mosquito richness in an understudied area: can environmental DNA metabarcoding be a complementary approach to adult trapping?

Mosquito surveillance programmes are essential to assess the risks of local vector-borne disease outbreaks as well as for early detection of mosquito invasion events. Surveys are usually performed with traditional sampling tools (i.e., ovitraps and dipping method for immature stages or light or decoy traps for adults). Over the past decade, numerous studies have highlighted that environmental DNA (eDNA) sampling can enhance invertebrate species detection and provide community composition metrics. However, the usefulness of eDNA for detection of mosquito species has, to date, been largely neglected. Here, we sampled water from potential larval breeding sites along a gradient of anthropogenic perturbations, from the core of an oil palm plantation to the rainforest on São Tomé Island (Gulf of Guinea, Africa). We showed that (i) species of mosquitoes could be detected via metabarcoding mostly when larvae were visible, (ii) larvae species richness was greater using eDNA than visual identification and (iii) new mosquito species were also detected by the eDNA approach. We provide a critical discussion of the pros and cons of eDNA metabarcoding for monitoring mosquito species diversity and recommendations for future research directions that could facilitate the adoption of eDNA as a tool for assessing insect vector communities.

How Antimicrobial Resistance Is Linked to Climate Change: An Overview of Two Intertwined Global Challenges.

Globally, antimicrobial resistance (AMR) and climate change (CC) are two of the top health emergencies, and can be considered as two interlinked public health priorities. The complex commonalities between AMR and CC should be deeply investigated in a One Health perspective. Here, we provided an overview of the current knowledge about the relationship between AMR and CC. Overall, the studies included pointed out the need for applying a systemic approach to planetary health. Firstly, CC increasingly brings humans and animals into contact, leading to outbreaks of zoonotic and vector-borne diseases with pandemic potential. Although it is well-established that antimicrobial use in human, animal and environmental sectors is one of the main drivers of AMR, the COVID-19 pandemic is exacerbating the current scenario, by influencing the use of antibiotics, personal protective equipment, and biocides. This also results in higher concentrations of contaminants (e.g., microplastics) in natural water bodies, which cannot be completely removed from wastewater treatment plants, and which could sustain the AMR spread. Our overview underlined the lack of studies on the direct relationship between AMR and CC, and encouraged further research to investigate the multiple aspects involved, and its effect on human health.

Outbreaks of Vector-borne Infectious Disease Following a Natural Disaster

Introduction Over the past century, global disaster deaths have averaged approximately 45,000 people annually. Vector-borne pathogens are susceptible to climatic conditions influencing vector survival, gonotrophic cycle, and transmission efficiency in human hosts. However, the literature has not collectively analyzed the relationship between natural disasters and vector-borne disease (VBD) outbreaks over decades. Objective This literature review identifies and examines published papers documenting VBD outbreaks associated with natural disasters. Additionally, information was gathered about the kinds of natural disasters commonly associated with VBD outbreaks and which diseases typically occur post- disasters. Methods A literature review was performed using two search strategies with terms for natural disasters and vector-borne infectious diseases as identified in the title, keywords, or abstract. Observational studies and systematic review papers were screened on the occurrence of a VBD post-disaster. Results A total of 30 studies were captured. Eight disaster types were captured: flood, hurricane, tropical cyclone, typhoon, tsunami, drought, monsoon, and earthquake. Floods (n=21), hurricanes (n=20), tsunamis (n=8), and drought (n=8) account for the top four disaster events commonly associated with VBDs. Of the VBDs identified, malaria outbreaks were identified in 16 papers, while dengue outbreaks were captured in 11. Conclusion The literature reveals a predominance of floods, malaria and dengue. While there is increasing acknowledgment that disasters can lead to outbreaks of VBDs, there is limited research and consistent data available. Future research should rely on well-defined, consistent case detection and enrollment procedures, preferably at various lag periods following a disaster event.

The Euler characteristic as a topological marker for outbreaks in vector-borne disease

Epidemic outbreaks represent a significant concern for the current state of global health, particularly in Brazil, the epicentre of several vector-borne disease outbreaks and where epidemic control is still a challenge for the scientific community. Data science techniques applied to epidemics are usually made via standard statistical and modelling approaches, which do not always lead to reliable predictions, especially when the data lacks a piece of reliable surveillance information needed for precise parameter estimation. In particular, dengue outbreaks reported over the past years raise concerns for global health care, and thus novel data-driven methods are necessary to predict the emergence of outbreaks. In this work, we propose a parameter-free approach based on geometric and topological techniques, which extracts geometrical and topological invariants as opposed to statistical summaries used in established methods. Specifically, our procedure generates a time-varying network from a time-series of new epidemic cases based on synthetic time-series and real dengue data across several districts of Recife, the fourth-largest urban area in Brazil. Subsequently, we use the Euler characteristic (EC) to extract key topological invariant of the epidemic time-varying network and we finally compared the results with the effective reproduction number (R t ) for each data set. Our results unveil a strong correlation between epidemic outbreaks and the EC. In fact, sudden changes in the EC curve preceding and/or during an epidemic period emerge as a warning sign for an outbreak in the synthetic data, the EC transitions occur close to the periods of epidemic transitions, which is also corroborated. In the real dengue data, where data is intrinsically noise, the EC seems to show a better sign-to-noise ratio once compared to R t . In analogy with later studies on noisy data by using EC in positron emission tomography scans, the EC estimates the number of regions with high connectivity in the epidemic network and thus has potential to be a signature of the emergence of an epidemic state. Our results open the door to the development of alternative/complementary topological and geometrical data-driven methods to characterise vector-borne disease outbreaks, specially when the conventional epidemic surveillance methods are not effective in a scenario of extreme noise and lack of robustness in the data.

Evaluation of Extreme Soil Moisture Conditions During the 2020 Sahel Floods and Implications for Disease Outbreaks

AbstractThe June‐October 2020 growing season was characterized by sustained and extreme flooding across the African Sahel. One consequence of flooding events such as this is outbreaks of vector borne diseases (VBDs) which are often associated with climate anomalies. In this study, data from the soil moisture active passive (SMAP) mission is used with other soil moisture and precipitation data to show that the 2020 Sahelian growing season was the most extreme over the past four decades, ranking first in seasonally accumulated precipitation, which on average exceeded the climatology by around 300 mm. VBD outbreaks of Rift Valley fever and Chikungunya followed in Mauritania/Senegal and Chad, respectively. In some cases, soil moisture is a better indicator of VBD outbreak risk than precipitation, which has so far been more commonly used in studies of VBD outbreaks. It is expected that this finding will inform future monitoring and prediction efforts for VBD risk.

Building community and health system resilience to climate disasters in Australia

Australia has recently experienced severe climate disasters, ranging from bushfires and droughts to floods and vector borne disease outbreaks. IPCC identified the inability of institutions to manage climate risks as a key risk for Australia. The unprecedented 2019-20 wildfires and the 2022 floods have raised questions about the resilience of the Australian health system and communities to intensifying extreme events in the context of climate change. The 2022 floods caused 23 deaths, large-scale community devastation, and disrupted health services. They increased COVID-19 and other infectious disease risks and long-lasting mental health consequences. Furthermore, they exposed health inequities and vulnerabilities related to non-communicable diseases in Aboriginal and low socio-economic communities. The Black Summer (2019-20) wildfires caused 33 fatalities, extensive damage to property, and destruction of flora and fauna, as well as exposing millions of people to extreme levels of air pollution. Bushfire smoke, a complex mixture of particles and gases, was transported by the wind over long distances affecting populated areas for several weeks. Public health interventions at both community, household and personal levels can mitigate the impact of climate disasters. The effectiveness, feasibility and scalability of these interventions, as well as any potential health co-benefits or other unintended consequences, need to be evaluated holistically taking into account quantitative and qualitative evidence. The impact of these interventions on health equity, particularly in relation to First Nations, at-risk and socioeconomically marginalized groups needs to be assessed, as these groups are typically more vulnerable to climate extremes. Strengthening the long-term resilience of the health sector and communities to climate disasters is crucial. The HEAL (Healthy Environments And Lives) Network is taking leadership in environmental change and health research that will provide the evidence, capacity and capability, and tools urgently needed to build community and health system resilience to intensifying climate disasters in Australia.

Efficacy of metal nanoparticles as a control tool against adult mosquito vectors: A review

Presently, there is a need to develop effective and novel modes of control for mosquitoes, which remain a key driver of infectious disease transmission throughout the world. Control methods for these vectors have historically relied on a limited number of active ingredients (AIs) that have not experienced significant change in usage since the mid-20th century. The resulting development of widespread insecticide resistance has consequently increased the risk for future vector-borne disease outbreaks. Recently, metal nanoparticles have been explored for potential use in mosquito control due to their demonstrated toxicity against mosquitoes at all life stages. However, the majority of studies to date have focused on the larvicidal efficacy of metal nanoparticles with few studies examining their adulticidal potential. In this review, we analyze the current literature on green synthesized metal nanoparticles and their effect on adult mosquitoes.

Effect of land use change on the phlebotomine sand fly assemblages in an emergent focus of cutaneous leishmaniasis in Yucatan, Mexico

As land use intensifies in tropical forests, it is expected that species assemblages will be modified and that key functions of these ecosystems will be affected. The latter scenario is important from a public health perspective, because the land use change has been linked the outbreaks of vector-borne diseases. In this study, we evaluated the response of Phlebotominae (Diptera: Psychodidae) assemblages and their pattern of co-occurrence in four sites with different land use in an emerging cutaneous leishmaniasis focus in Yucatan, Mexico. Our hypothesis is that the conservation status (as forest cover) will positively influence the structure and composition of sand flies’ assemblages. Using three different traps over a period of five months, a sampling effort of 1, 440 night-traps was performed. A total of 7, 897 sand fly specimens belonging to six genera and 10 species were collected. Our hypothesis was partially achieved since sand fly diversity increased as forest cover increased and vice versa, however random patterns of co-occurrence in assemblages were detected among sites. Even though the high abundance of sand flies in the forest fragment suggests an amplification effect, our results show that different vector species directly dominate in each site. We discuss the potential implications of the nestedness of species dominance. We suggest that in this emerging focus and under the land use gradient, Lutzomyia cruciata and Psathyromyia cratifer could play a pivotal role in maintaining the transmission cycles of Leishmania. The apparent generalist or colonialist profile of Lu. cruciata in disturbed areas deserves attention, due to the potential risk of leishmaniasis “domiciliation”. This information is essential to understand the eco-epidemiology of leishmaniasis and the factors associated with its emergence in Yucatan, Mexico.

Needs Assessment of Southeastern United States Vector Control Agencies: Capacity Improvement Is Greatly Needed to Prevent the Next Vector-Borne Disease Outbreak.

A national 2017 vector control capacity survey was conducted to assess the United States’ (U.S.’s) ability to prevent emerging vector-borne disease. Since that survey, the southeastern U.S. has experienced continued autochthonous exotic vector-borne disease transmission and establishment of invasive vector species. To understand the current gaps in control programs and establish a baseline to evaluate future vector control efforts for this vulnerable region, a focused needs assessment survey was conducted in early 2020. The southeastern U.S. region was targeted, as this region has a high probability of novel vector-borne disease introduction. Paper copies delivered in handwritten envelopes and electronic copies of the survey were delivered to 386 unique contacts, and 150 returned surveys were received, corresponding to a 39% response rate. Overall, the survey found vector control programs serving areas with over 100,000 residents and those affiliated with public health departments had more core capabilities compared to smaller programs and those not affiliated with public health departments. Furthermore, the majority of vector control programs in this region do not routinely monitor for pesticide resistance. Taken as a whole, these results suggest that the majority of the southeastern U.S. is vulnerable to vector-borne disease outbreaks. Results from this survey raise attention to the critical need of providing increased resources to bring all vector control programs to a competent level, ensuring that public health is protected from the threat of vector-borne disease.

An outbreak of malaria caused by increase in malaria breeding sites in swamps.

On 10th June 2019, routine analysis of malaria surveillance data at the National Malaria Control Division, Ministry of Health in Uganda revealed that there was an unusual increase in the number of malaria cases reported in the Oyam District. On 11th June 2019, the District Health Officer in Oyam District convened a meeting with the District Health Team (DHT) in which the District Biostatistician confirmed that the number of malaria cases had indeed exceeded the upper limit, starting in epidemic week 24 (approximately the week of June 10). The District Health Officer issued a formal request to the Ministry of Health for assistance in dealing with the malaria outbreak in Oyam. Two field epidemiology residents were assigned to work with the District Health Team to investigate the outbreak. The residents followed the steps in conducting vector borne disease outbreak investigations including preparation for field work, establishment of the existence of an outbreak by analyzing surveillance data, descriptive data analysis, hypothesis generation, conducting environmental and entomological assessments, conducting analytic studies with a focus on the utility of retrospective cohort studies as well as reporting findings. This case study teaches trainees in Field Epidemiology and Laboratory Training Programs, public health students, public health workers who are interested or who may participate in vector borne disease outbreak investigation and response.

Ethnic conflict as a risk amplifier for resurgent P. vivax malaria in temperate zones: A case study from the Caucasus region

One of the most protracted post-Soviet conflicts of the 1990s was a territorial dispute between Armenia and Azerbaijan over the contested Karabakh region. Years of ethnic violence led to the displacement of nearly a million refugees, as well as a public health crisis that included epidemics of malaria, diphtheria and other preventable diseases. Malaria is not usually considered a health risk in temperate climates, but seasonal epidemics were widespread throughout the Caucasus in the early decades of the twentieth century. This paper combines qualitative historical research with geospatial analysis to explore how endemic malaria was controlled during the Soviet era, and how ethnic conflict reconfigured local ecologies to facilitate the re-emergence of P. vivax after the Soviet collapse in the 1990s. This research reveals that ethnic conflicts have specific qualities that increase risks of infectious and vector borne disease outbreaks, even in places that have successfully achieved a modern health and mortality profile. The risk amplifiers of ethnic conflicts include 1) the creation of contested spaces controlled by separatists that are outside of any national public health surveillance system; 2) mass population movements and refugee outflows due to ethnic violence; and 3) changes in land use that expand potential mosquito breeding sites throughout the conflict zone. Continued hostilities between Armenia and Azerbaijan, combined with the repopulation of key vector species (specifically An. sacharovi) lead us to conclude that populations in the Caucasus remain vulnerable to resurgent outbreaks of ethno-nationalist violence as well as the return of seasonal malaria, even after decades of successful control.

ARBO: Arbovirus modeling and uncertainty quantification toolbox.

The ongoing pandemic of COVID-19 has highlighted the importance of mathematical tools to understand and predict outbreaks of severe infectious diseases, including arboviruses such as Zika. To this end, we introduce ARBO, a package for simulation and analysis of arbovirus nonlinear dynamics. The implementation follows a minimalist style, and is intuitive and extensible to many settings of vector-borne disease outbreaks. This paper outlines the main tools that compose ARBO, discusses how recent research works about the Brazilian Zika outbreak have explored the package’s capabilities, and describes its potential impact for future works on mathematical epidemiology.

Video analysis of the locomotory behaviour of Aedes aegypti and Ae. japonicus mosquitoes under different temperature regimes in a laboratory setting

Mosquito-borne diseases impose a high burden on human and animal health. Temperature strongly influences the physiology and life cycle of mosquitoes, but also the development and/or propagation of the pathogens they transmit. Thus, the vector capacity of mosquitoes depends strongly on temperature and their behavioural thermoregulation through microhabitat selection. Expanding on a previous study of static thermal preferences, the locomotory dynamics of temperate Aedes japonicus (reared from eggs collected in the field) and tropical Ae. aegypti (from a laboratory colony) was investigated at constant temperatures (10 °C, 25 °C, 40 °C) and in temperature gradients (10–20 °C, 20–30 °C, 30–40 °C). Blood-fed or non-blood-fed female mosquitoes were released in groups of 15 individuals into a Plexiglas box positioned on two thermoregulators connected by an aluminium plate to automatically monitor by video analysis mosquito flying, walking and resting duration, covered distances and velocity. Mosquitoes were predominantly resting, followed by walking and flying. At constant 10 °C, flights were rare and brief, and walking was slow. Most activity was observed at 25 °C for Ae. japonicus and 40 °C for Ae. aegypti. In the 30–40 °C gradient, activity of Ae. aegypti increased towards the cold end, suggesting active avoidance of very high temperatures. In the 20–30 °C gradient, edge effects were prominent, nevertheless revealing a greater proportion of mosquitoes gathered at the cooler end. Video analysis showed that this effect was not caused by a cold trap but represents true thermal preference. In the coolest gradient (10–20 °C), mosquitoes were active in all sectors without displaying a preference for either side. Overall, both the tropical and temperate mosquito species preferred cooler temperatures and actively avoided the hottest temperatures. Further studies with infected mosquitoes should provide important insights for developing models of vector-borne disease outbreaks.

The role of agriculture in human infectious disease outbreaks

AbstractThis study uses the available data to explore the temporal and geographical patterns of infectious diseases and their links between human demography, human-induced land-use change, livestock and poultry expansion, and biodiversity loss. Over the last decades, the number of outbreaks of zoonotic and vector-borne diseases increased mostly in the intertropical zone. The increase in cropland, grassland, tree plantation, livestock, poultry, biodiversity at threat (using the Red List index) mostly occurred in the intertropical zone. Using structural equation modeling, significant relationships were observed between disease outbreaks, human demography, livestock (cattle and pigs), poultry (chickens), tree plantation and artificial land expansion as well as with increasing biodiversity at threat. While agricultural expansion is seen as a driver of biodiversity loss and potentially emerging infectious diseases, here we show that cropland and grassland expansion does not appear to enhance disease outbreaks directly, but indirectly and only for cropland on biodiversity loss. The links observed between infectious disease outbreaks, human demography, agriculture, livestock, urbanization and biodiversity should help rethink the global food system in ways that minimize the risk of infectious diseases while preserving biodiversity and contributing to Sustainable Goals.

Impacts of fungal entomopathogens on survival and immune responses of Aedes albopictus and Culex pipiens mosquitoes in the context of native Wolbachia infections.

Microbial control of mosquitoes via the use of symbiotic or pathogenic microbes, such as Wolbachia and entomopathogenic fungi, are promising alternatives to synthetic insecticides to tackle the rapid increase in insecticide resistance and vector-borne disease outbreaks. This study evaluated the susceptibility and host responses of two important mosquito vectors, Ae. albopictus and Cx. pipiens, that naturally carry Wolbachia, to infections by entomopathogenic fungi. Our study indicated that while Wolbachia presence did not provide a protective advantage against entomopathogenic fungal infection, it nevertheless influenced the bacterial / fungal load and the expression of select anti-microbial effectors and phenoloxidase cascade genes in mosquitoes. Furthermore, although host responses from Ae. albopictus and Cx. pipiens were mostly similar, we observed contrasting phenotypes with regards to susceptibility and immune responses to fungal entomopathogenic infection in these two mosquitoes. This study provides new insights into the intricate multipartite interaction between the mosquito host, its native symbiont and pathogenic microbes that might be employed to control mosquito populations.

Climate change and infectious disease in Europe: Impact, projection and adaptation.

SummaryEuropeans are not only exposed to direct effects from climate change, but also vulnerable to indirect effects from infectious disease, many of which are climate sensitive, which is of concern because of their epidemic potential. Climatic conditions have facilitated vector-borne disease outbreaks like chikungunya, dengue, and West Nile fever and have contributed to a geographic range expansion of tick vectors that transmit Lyme disease and tick-borne encephalitis. Extreme precipitation events have caused waterborne outbreaks and longer summer seasons have contributed to increases in foodborne diseases. Under the Green Deal, The European Union aims to support climate change health policy, in order to be better prepared for the next health security threat, particularly in the aftermath of the traumatic COVID-19 experience. To bolster this policy process we discuss climate change-related hazards, exposures and vulnerabilities to infectious disease and describe observed impacts, projected risks, with policy entry points for adaptation to reduce these risks or avoid them altogether.