Environmental Changes and Infectious Disease in Tropical Asia

Moji Kazuhiko RIHN

nishimoto Futoshi RIHN

kobayashi Jun National Center for Global Health and Medicine kobayashi Shigeo Kyoto University iijima Wataru Aoyama Gakuin University itoh Makoto Aichi Medical University tomita Shinsuke University of Tokyo asakura Takashi Tokyo Gakugei University yamamoto Taro Nagasaki University kaneko Satoshi Nagasaki University hashizume Masahiro Nagasaki University sunahara Toshihiko Nagasaki University ahmed, Kamruddin Oita University boupha, Boungnong National Institute of Public Health, Lao PDR kounnavong, Sengchanh National Institute of Public Health, Lao PDR pongvongsa, Tiengkham Savannakhet Malaria Station, Lao PDR islam, Sirajul ICDDR, B, Bangladesh hunter, Paul University of East Anglia, UK mascie-Taylor, Nick Cambridge University, UK hossain, Moazzem Institute of Allergy and Clinical Immunology, Bangladesh rahman, Mahmudur IEDCR, Bangladesh zhang Kong-Lai Peking Union Medical College, China zhang Kaining YHDRA, China ichikawa, Tomo Shanghai Jiao Tong University, China cai, Gouxi RIHN tojo, Bunpei RIHN

The health profile of a human population can be seen as a product of the human ecosystem—an ecosystem comprised of both biophysical and human elements. The construction and conservation of sound human ecosystems, therefore, is essential to the livelihood, health and survival of human populations. The field of ecohealth considers human livelihood and health in relation to environmental conditions; it can improve attempts to address disease and local and global environmental problems.

Project background

The health profile of a human population can be seen as a product of the human ecosystem—an ecosystem comprised of both biophysical and human elements. The construction and conservation of sound human ecosystems, therefore, is essential to the health and survival of human populations. The field of ecohealth considers human health and disease in relation to environmental conditions; it can improve attempts to address disease and local and global environmental problems.

Progress to date

Table 1  Target diseases of the RIHN Ecohealth Project (click to see bigger image)

The RIHN Ecohealth Project is studying major infectious diseases in tropical monsoon Asia (Table 1).

Several research groups comprise our project. The Lahanam Study Group’s research in Savannakhet Province, Laos, examines patterns of liver fluke infection of Opisthorchis viverrini (Ov), a parasital infection associated with consumption of raw freshwater fish. In 2011 the principal objectives of this group are to:

1) Maintain and expand the Lahanam Health and Demographic Surveillance System (HDSS) and analyse life expectancy and causes of death;

2) Study the relation between modern irrigation/wet-rice cultivation and liver fluke infection (Fig. 1);

3) Study fish and snail ecology, fishery ecology, and consumption of fish, and;

4) Determine feasible educational, behavioural, and/or environmental control of liver fluke infection. Studies on young children and school health and nutrition are also underway.

Figure 1  Life cycle of liver fluke (Ov) and research strategies (click to see bigger image)

The Sepone Study Group's work in Savannakhet Province, Laos, is developing an integrated ecological and medical approach to malaria control and elimination in Southeast Asia. This group established a mobile phone-based health information network system covering all 158 villages in Sepone. Land-cover studies and satellite image analysis (ALOS) were conducted in Lahanam and Sepone. In 2010 this group found the very high mortality of young children among mountain farmers. The principal objectives of this group in 2011 are to:

1) Maintain the Sepone Health Information Network in order to monitor monthly incidence of malaria and other diseases;

2) Analyze the relation of forest cover change, settlement, subsistence, mosquito population/ecology with malaria endemiology/epidemiology;

3) Analyze the environmental and societal changes within the Banhiang River catchment area (a tributary of the Mekong River), including rainfall, flood, land- cover/use, and water quantity and quality;

4) Analyze the effects of the Vietnam War on the occurrence of malaria (Fig. 2).

Figure 2  ALOS image of Savannakhet Province of Lao PDR with density of bombing during the Vietnam War

The Vietnam Study Group is focusing on transmission of new human malaria, Plasmodium knowlesi (Pk) in humans as well as in monkeys. The group found a very high mix-infection of Pk with P. vivax in humans. The group therefore has begun to analyse Pk incidence through a multi-disciplinary approach including malariology, entomology, primatology, forestry, epidemiology and social sciences. The team also is assessing the prevalence of Pk near the Sepone border of Laos.

The Bangladesh Study Group is working in collaboration with the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR, B) to study the relationship between the Indian Ocean Dipole and the incidence of cholera in Dhaka. This group is also studying the long-term effects of flood on morbidity and mortality in Matlab. In collaboration with the Ministry of Health and Welfare, a subgroup is studying epidemiology of rabies in the entire nation, and of filariasis in the north-west of the country.

Table 2  Disease profile of Indochina in 1922

The China Study Group investigates how social and environmental change affects health in the Greater Mekong Subregion. There are many vulnerable populations, including male and female commercial sex workers, IV drug users, migrant urban labourers, poor rural farmers and international migrants. The Yunnan Health and Development Research Association (YHDRA) is conducting research to improve the ecohealth of such vulnerable populations, and Ecohealth Project researchers are also describing the prevalence of HIV/AIDS among vulnerable peoples in the region. The China History Study Group is making a database documenting control of malaria and schistosomiasis in the 20th Century. The disease profile of colonial Indochina is also described (Table 2).