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Climate Change and Spatiotemporal Distributions of Vector-Borne Diseases in Nepal--A Systematic Synthesis of Literature.

Dhimal M, Ahrens B, Kuch U - PLoS ONE (2015)

Bottom Line: We found 12 studies that analysed the trend of climatic data and are relevant for the study of VBDs, 38 studies that dealt with the spatial and temporal distribution of disease vectors and disease transmission.Furthermore, significant relationships between climatic variables and VBDs and their vectors are found in short-term studies.Taking into account the weak health care systems and difficult geographic terrain of Nepal, increasing trade and movements of people, a lack of vector control interventions, observed relationships between climatic variables and VBDs and their vectors and the establishment of relevant disease vectors already at least 2,000 m above sea level, we conclude that climate change can intensify the risk of VBD epidemics in the mountain regions of Nepal if other non-climatic drivers of VBDs remain constant.

View Article: PubMed Central - PubMed

Affiliation: Nepal Health Research Council (NHRC), Ministry of Health and Population Complex, Kathmandu, Nepal; Biodiversity and Climate Research Centre (BiK-F), Senckenberg Gesellschaft für Naturforschung, Frankfurt am Main, Germany; Institute for Atmospheric and Environmental Sciences (IAU), Goethe University, Frankfurt am Main, Germany; Institute of Occupational Medicine, Social Medicine and Environmental Medicine, Goethe University, Frankfurt am Main, Germany.

ABSTRACT

Background: Despite its largely mountainous terrain for which this Himalayan country is a popular tourist destination, Nepal is now endemic for five major vector-borne diseases (VBDs), namely malaria, lymphatic filariasis, Japanese encephalitis, visceral leishmaniasis and dengue fever. There is increasing evidence about the impacts of climate change on VBDs especially in tropical highlands and temperate regions. Our aim is to explore whether the observed spatiotemporal distributions of VBDs in Nepal can be related to climate change.

Methodology: A systematic literature search was performed and summarized information on climate change and the spatiotemporal distribution of VBDs in Nepal from the published literature until December 2014 following providing items for systematic review and meta-analysis (PRISMA) guidelines.

Principal findings: We found 12 studies that analysed the trend of climatic data and are relevant for the study of VBDs, 38 studies that dealt with the spatial and temporal distribution of disease vectors and disease transmission. Among 38 studies, only eight studies assessed the association of VBDs with climatic variables. Our review highlights a pronounced warming in the mountains and an expansion of autochthonous cases of VBDs to non-endemic areas including mountain regions (i.e., at least 2,000 m above sea level). Furthermore, significant relationships between climatic variables and VBDs and their vectors are found in short-term studies.

Conclusion: Taking into account the weak health care systems and difficult geographic terrain of Nepal, increasing trade and movements of people, a lack of vector control interventions, observed relationships between climatic variables and VBDs and their vectors and the establishment of relevant disease vectors already at least 2,000 m above sea level, we conclude that climate change can intensify the risk of VBD epidemics in the mountain regions of Nepal if other non-climatic drivers of VBDs remain constant.

No MeSH data available.


Related in: MedlinePlus

Spatiotemporal distribution of lymphatic filariasis in Nepal (2001–2012).In 2001, lymphatic filariasis mapping using immunochromatographic card tests in 37 districts of Nepal showed that LF was endemic in only 33 districts. Between 2002 and 2012, LF was confirmed as endemic in 60 districts of Nepal including mountain region districts.
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pone.0129869.g007: Spatiotemporal distribution of lymphatic filariasis in Nepal (2001–2012).In 2001, lymphatic filariasis mapping using immunochromatographic card tests in 37 districts of Nepal showed that LF was endemic in only 33 districts. Between 2002 and 2012, LF was confirmed as endemic in 60 districts of Nepal including mountain region districts.

Mentions: The mosquito species Culex. quinquefasciatus, the principal vector of Wuchereria bancrofti microfilaria in South Asia, was first recorded in Nepal in 1956 [91] and found to occur within the LF endemic zones of this country[50,52,53]. In the year 2001, LF was endemic in 33 out of 37 surveyed districts of Nepal. The majority of cases were confined to an altitudinal range between 500–700 m asl, however, with a substantial number of cases at altitudes between 900–1400 m asl[84]. A sentinel surveillance conducted in 2007 among 7,000 people residing in six districts of the lowland (Terai), hill and mountain regions of Nepal reported the highest microfilaria infection rate (2.0%) in the mountain district of Sidhupalanchowk [85], suggesting a shift of LF transmission to the mountain region of Nepal after the introduction of mass drug administration (MDA) programmes in lowland and hill districts which had started in Parsa district in 2003. By 2013, six rounds of MDA had been completed in 16 endemic districts and four, three, two and one round of MDA in 10 districts each, and a gradual expansion of MDA reached 5 endemic districts covering 74% of the total population at risk (N = 21,852,201) [50]. However, 61 out of 75 administrative districts have already been reported as being LF endemic, and Nepal plans to cover the remaining six endemic districts with MDA by 2014 and achieve <1% prevalence in all endemic districts by 2018 [50]. Previously, Cx. quinquefasciatus mosquitoes had been recorded in all endemic districts ranging from 90 to 1,800 m asl[102], and recent studies report the distribution of Cx. quinquefasciatusup to at least 2,100 m (the highest sampled altitude in that study) in the districts of Dhunche and Rasuwa which had previously been regarded as non-endemic for LF [94], and above 2,000 m in Nagarkot of Bhaktapur district [93]. Moreover, significant effects of the climatic factors temperature and relative humidity, physiographic region and month of collection on the mean abundance of Cx. quinquefasciatusper (per trap) were found [94]. The spatiotemporal distribution of LF in Nepal (2001–2012) is shown in Fig 7[84,85,102]


Climate Change and Spatiotemporal Distributions of Vector-Borne Diseases in Nepal--A Systematic Synthesis of Literature.

Dhimal M, Ahrens B, Kuch U - PLoS ONE (2015)

Spatiotemporal distribution of lymphatic filariasis in Nepal (2001–2012).In 2001, lymphatic filariasis mapping using immunochromatographic card tests in 37 districts of Nepal showed that LF was endemic in only 33 districts. Between 2002 and 2012, LF was confirmed as endemic in 60 districts of Nepal including mountain region districts.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4472520&req=5

pone.0129869.g007: Spatiotemporal distribution of lymphatic filariasis in Nepal (2001–2012).In 2001, lymphatic filariasis mapping using immunochromatographic card tests in 37 districts of Nepal showed that LF was endemic in only 33 districts. Between 2002 and 2012, LF was confirmed as endemic in 60 districts of Nepal including mountain region districts.
Mentions: The mosquito species Culex. quinquefasciatus, the principal vector of Wuchereria bancrofti microfilaria in South Asia, was first recorded in Nepal in 1956 [91] and found to occur within the LF endemic zones of this country[50,52,53]. In the year 2001, LF was endemic in 33 out of 37 surveyed districts of Nepal. The majority of cases were confined to an altitudinal range between 500–700 m asl, however, with a substantial number of cases at altitudes between 900–1400 m asl[84]. A sentinel surveillance conducted in 2007 among 7,000 people residing in six districts of the lowland (Terai), hill and mountain regions of Nepal reported the highest microfilaria infection rate (2.0%) in the mountain district of Sidhupalanchowk [85], suggesting a shift of LF transmission to the mountain region of Nepal after the introduction of mass drug administration (MDA) programmes in lowland and hill districts which had started in Parsa district in 2003. By 2013, six rounds of MDA had been completed in 16 endemic districts and four, three, two and one round of MDA in 10 districts each, and a gradual expansion of MDA reached 5 endemic districts covering 74% of the total population at risk (N = 21,852,201) [50]. However, 61 out of 75 administrative districts have already been reported as being LF endemic, and Nepal plans to cover the remaining six endemic districts with MDA by 2014 and achieve <1% prevalence in all endemic districts by 2018 [50]. Previously, Cx. quinquefasciatus mosquitoes had been recorded in all endemic districts ranging from 90 to 1,800 m asl[102], and recent studies report the distribution of Cx. quinquefasciatusup to at least 2,100 m (the highest sampled altitude in that study) in the districts of Dhunche and Rasuwa which had previously been regarded as non-endemic for LF [94], and above 2,000 m in Nagarkot of Bhaktapur district [93]. Moreover, significant effects of the climatic factors temperature and relative humidity, physiographic region and month of collection on the mean abundance of Cx. quinquefasciatusper (per trap) were found [94]. The spatiotemporal distribution of LF in Nepal (2001–2012) is shown in Fig 7[84,85,102]

Bottom Line: We found 12 studies that analysed the trend of climatic data and are relevant for the study of VBDs, 38 studies that dealt with the spatial and temporal distribution of disease vectors and disease transmission.Furthermore, significant relationships between climatic variables and VBDs and their vectors are found in short-term studies.Taking into account the weak health care systems and difficult geographic terrain of Nepal, increasing trade and movements of people, a lack of vector control interventions, observed relationships between climatic variables and VBDs and their vectors and the establishment of relevant disease vectors already at least 2,000 m above sea level, we conclude that climate change can intensify the risk of VBD epidemics in the mountain regions of Nepal if other non-climatic drivers of VBDs remain constant.

View Article: PubMed Central - PubMed

Affiliation: Nepal Health Research Council (NHRC), Ministry of Health and Population Complex, Kathmandu, Nepal; Biodiversity and Climate Research Centre (BiK-F), Senckenberg Gesellschaft für Naturforschung, Frankfurt am Main, Germany; Institute for Atmospheric and Environmental Sciences (IAU), Goethe University, Frankfurt am Main, Germany; Institute of Occupational Medicine, Social Medicine and Environmental Medicine, Goethe University, Frankfurt am Main, Germany.

ABSTRACT

Background: Despite its largely mountainous terrain for which this Himalayan country is a popular tourist destination, Nepal is now endemic for five major vector-borne diseases (VBDs), namely malaria, lymphatic filariasis, Japanese encephalitis, visceral leishmaniasis and dengue fever. There is increasing evidence about the impacts of climate change on VBDs especially in tropical highlands and temperate regions. Our aim is to explore whether the observed spatiotemporal distributions of VBDs in Nepal can be related to climate change.

Methodology: A systematic literature search was performed and summarized information on climate change and the spatiotemporal distribution of VBDs in Nepal from the published literature until December 2014 following providing items for systematic review and meta-analysis (PRISMA) guidelines.

Principal findings: We found 12 studies that analysed the trend of climatic data and are relevant for the study of VBDs, 38 studies that dealt with the spatial and temporal distribution of disease vectors and disease transmission. Among 38 studies, only eight studies assessed the association of VBDs with climatic variables. Our review highlights a pronounced warming in the mountains and an expansion of autochthonous cases of VBDs to non-endemic areas including mountain regions (i.e., at least 2,000 m above sea level). Furthermore, significant relationships between climatic variables and VBDs and their vectors are found in short-term studies.

Conclusion: Taking into account the weak health care systems and difficult geographic terrain of Nepal, increasing trade and movements of people, a lack of vector control interventions, observed relationships between climatic variables and VBDs and their vectors and the establishment of relevant disease vectors already at least 2,000 m above sea level, we conclude that climate change can intensify the risk of VBD epidemics in the mountain regions of Nepal if other non-climatic drivers of VBDs remain constant.

No MeSH data available.


Related in: MedlinePlus