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Spatial characterization of colonies of the flying fox bat, a carrier of Nipah virus in Thailand.

Thanapongtharm W, Linard C, Wiriyarat W, Chinsorn P, Kanchanasaka B, Xiao X, Biradar C, Wallace RG, Gilbert M - BMC Vet. Res. (2015)

Bottom Line: While no evidence of infection in domestic pigs or people has been found to date, pig farming is an active agricultural sector in Thailand and therefore could be a potential pathway for zoonotic disease transmission from the bat reservoirs.Flying fox colonies are found mainly on Thailand's Central Plain, particularly in locations surrounded by bodies of water, vegetation, and safe havens such as Buddhist temples.Such proactive planning would help conserve flying fox colonies and should help prevent zoonotic transmission of Nipah and other pathogens.

View Article: PubMed Central - PubMed

Affiliation: Department of Livestock Development (DLD), Bangkok, Thailand. weeraden@yahoo.com.

ABSTRACT

Background: A major reservoir of Nipah virus is believed to be the flying fox genus Pteropus, a fruit bat distributed across many of the world's tropical and sub-tropical areas. The emergence of the virus and its zoonotic transmission to livestock and humans have been linked to losses in the bat's habitat. Nipah has been identified in a number of indigenous flying fox populations in Thailand. While no evidence of infection in domestic pigs or people has been found to date, pig farming is an active agricultural sector in Thailand and therefore could be a potential pathway for zoonotic disease transmission from the bat reservoirs. The disease, then, represents a potential zoonotic risk. To characterize the spatial habitat of flying fox populations along Thailand's Central Plain, and to map potential contact zones between flying fox habitats, pig farms and human settlements, we conducted field observation, remote sensing, and ecological niche modeling to characterize flying fox colonies and their ecological neighborhoods. A Potential Surface Analysis was applied to map contact zones among local epizootic actors.

Results: Flying fox colonies are found mainly on Thailand's Central Plain, particularly in locations surrounded by bodies of water, vegetation, and safe havens such as Buddhist temples. High-risk areas for Nipah zoonosis in pigs include the agricultural ring around the Bangkok metropolitan region where the density of pig farms is high.

Conclusions: Passive and active surveillance programs should be prioritized around Bangkok, particularly on farms with low biosecurity, close to water, and/or on which orchards are concomitantly grown. Integration of human and animal health surveillance should be pursued in these same areas. Such proactive planning would help conserve flying fox colonies and should help prevent zoonotic transmission of Nipah and other pathogens.

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Related in: MedlinePlus

Flying fox colonies compared to their environments. Comparison among the locations of the flying foxes’ colonies (circle) and variables in the study area: elevation (A); land cover (B); bodies of water (C); and human density (D).
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Fig2: Flying fox colonies compared to their environments. Comparison among the locations of the flying foxes’ colonies (circle) and variables in the study area: elevation (A); land cover (B); bodies of water (C); and human density (D).

Mentions: During field observation we observed flying foxes roosted on several types of trees: tamarind, coconut tree, bamboo (grass family), mangrove forests, and others (mostly members of evergreen forests) (Table 2). The colonies occupied a median area of 6,562 m2 (ranging 1,463-30,751 m2), and the median distance to the nearest neighbor colony was 23.2 km (ranging 12.5-57.7 km) (Table 3). Almost all colonies were located on the central plain (Figure 2A), with a median elevation of 9 m (ranging 5–65 m). The colonies clustered into 4 groups according to the type of roosting trees: 1) bamboo only; 2) mangrove forests only; 3) rubber trees only; and 4) various types of trees. We observed that while some trees failed to protect against sunlight, some colonies remained. Most colonies were located nearby Buddhist temples (median nearest distance 262 m, range 42–2704 m), with 13 of the 22 colonies roosting on trees located within the temple area (no. 3–7, 9–11, 13, 15, 16, 20 and 22). When overlaid over the land cover maps (Figure 2B), the majority of colonies were surrounded by irrigated vegetation covering 96% of the landscape within 10 km2, followed by settlement/rainfed vegetation (2.3%), bodies of water (1.5%), and forest (0.1%). Colonies were found on an island (no. 18) and riverside (no. 19), accessible to humans by boat alone. One colony was protected by the Wildlife Conservation Park (no. 1) and others located on private lands (no. 2, 8, 12, 14, 17, and 21). All colonies were located nearby bodies of water such as rivers, canals, ponds, and the sea (Figure 2C, median distance 120 m, range 30–4815 m). Some colonies were located in places with relatively high human population densities (Figure 2D), usually within Buddhist temples, where the number of tourists can be high (median population density of 232 people km−2, range 0–1307 people km−2), while one bat colony was located on an island uninhabited by humans. We observed that some colonies had moved away from their previously known sites. Colony no. 21 moved away from its old site to a new isolated site along the sea and colony no. 17 moved away from a site with numerous destroyed mangrove forest trees to an adjacent area.Table 2


Spatial characterization of colonies of the flying fox bat, a carrier of Nipah virus in Thailand.

Thanapongtharm W, Linard C, Wiriyarat W, Chinsorn P, Kanchanasaka B, Xiao X, Biradar C, Wallace RG, Gilbert M - BMC Vet. Res. (2015)

Flying fox colonies compared to their environments. Comparison among the locations of the flying foxes’ colonies (circle) and variables in the study area: elevation (A); land cover (B); bodies of water (C); and human density (D).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4389713&req=5

Fig2: Flying fox colonies compared to their environments. Comparison among the locations of the flying foxes’ colonies (circle) and variables in the study area: elevation (A); land cover (B); bodies of water (C); and human density (D).
Mentions: During field observation we observed flying foxes roosted on several types of trees: tamarind, coconut tree, bamboo (grass family), mangrove forests, and others (mostly members of evergreen forests) (Table 2). The colonies occupied a median area of 6,562 m2 (ranging 1,463-30,751 m2), and the median distance to the nearest neighbor colony was 23.2 km (ranging 12.5-57.7 km) (Table 3). Almost all colonies were located on the central plain (Figure 2A), with a median elevation of 9 m (ranging 5–65 m). The colonies clustered into 4 groups according to the type of roosting trees: 1) bamboo only; 2) mangrove forests only; 3) rubber trees only; and 4) various types of trees. We observed that while some trees failed to protect against sunlight, some colonies remained. Most colonies were located nearby Buddhist temples (median nearest distance 262 m, range 42–2704 m), with 13 of the 22 colonies roosting on trees located within the temple area (no. 3–7, 9–11, 13, 15, 16, 20 and 22). When overlaid over the land cover maps (Figure 2B), the majority of colonies were surrounded by irrigated vegetation covering 96% of the landscape within 10 km2, followed by settlement/rainfed vegetation (2.3%), bodies of water (1.5%), and forest (0.1%). Colonies were found on an island (no. 18) and riverside (no. 19), accessible to humans by boat alone. One colony was protected by the Wildlife Conservation Park (no. 1) and others located on private lands (no. 2, 8, 12, 14, 17, and 21). All colonies were located nearby bodies of water such as rivers, canals, ponds, and the sea (Figure 2C, median distance 120 m, range 30–4815 m). Some colonies were located in places with relatively high human population densities (Figure 2D), usually within Buddhist temples, where the number of tourists can be high (median population density of 232 people km−2, range 0–1307 people km−2), while one bat colony was located on an island uninhabited by humans. We observed that some colonies had moved away from their previously known sites. Colony no. 21 moved away from its old site to a new isolated site along the sea and colony no. 17 moved away from a site with numerous destroyed mangrove forest trees to an adjacent area.Table 2

Bottom Line: While no evidence of infection in domestic pigs or people has been found to date, pig farming is an active agricultural sector in Thailand and therefore could be a potential pathway for zoonotic disease transmission from the bat reservoirs.Flying fox colonies are found mainly on Thailand's Central Plain, particularly in locations surrounded by bodies of water, vegetation, and safe havens such as Buddhist temples.Such proactive planning would help conserve flying fox colonies and should help prevent zoonotic transmission of Nipah and other pathogens.

View Article: PubMed Central - PubMed

Affiliation: Department of Livestock Development (DLD), Bangkok, Thailand. weeraden@yahoo.com.

ABSTRACT

Background: A major reservoir of Nipah virus is believed to be the flying fox genus Pteropus, a fruit bat distributed across many of the world's tropical and sub-tropical areas. The emergence of the virus and its zoonotic transmission to livestock and humans have been linked to losses in the bat's habitat. Nipah has been identified in a number of indigenous flying fox populations in Thailand. While no evidence of infection in domestic pigs or people has been found to date, pig farming is an active agricultural sector in Thailand and therefore could be a potential pathway for zoonotic disease transmission from the bat reservoirs. The disease, then, represents a potential zoonotic risk. To characterize the spatial habitat of flying fox populations along Thailand's Central Plain, and to map potential contact zones between flying fox habitats, pig farms and human settlements, we conducted field observation, remote sensing, and ecological niche modeling to characterize flying fox colonies and their ecological neighborhoods. A Potential Surface Analysis was applied to map contact zones among local epizootic actors.

Results: Flying fox colonies are found mainly on Thailand's Central Plain, particularly in locations surrounded by bodies of water, vegetation, and safe havens such as Buddhist temples. High-risk areas for Nipah zoonosis in pigs include the agricultural ring around the Bangkok metropolitan region where the density of pig farms is high.

Conclusions: Passive and active surveillance programs should be prioritized around Bangkok, particularly on farms with low biosecurity, close to water, and/or on which orchards are concomitantly grown. Integration of human and animal health surveillance should be pursued in these same areas. Such proactive planning would help conserve flying fox colonies and should help prevent zoonotic transmission of Nipah and other pathogens.

Show MeSH
Related in: MedlinePlus