Objectives

    Infectious disease has become a significant global environmental problem. This study investigates the emergence and spread of Koi HerpesVirus (KHV) in Lake Biwa, Japan. KHV is a pathogen responsible for episodic mass mortality of commoncarp (Cyprinus carpio carpio)  since the late1990s. The common carp is the original domesticated aquaculture species, and an important source of protein today .

    This study has three main objectives: (1) To describe Koi Herpes Virus disease ecology, including: the specific links between anthropogenic changes to freshwater ecosystems and the emergence and spread of KHV disease; the impacts of KHV disease on local ecosystem services; the social and cultural attempts to address KHV disease; and the environmental changes associated with human adaptation; (2) To describe a general model of linkage between environments, pathogens and humans ; (3) To suggest how interactions between pathogen and humans may be modified in order to mitigate the human and environmental damages associated with infectious diseases.

 

Research Methods and Organization

    Fields surveys areconducted at Lake Biwa, Japan, and Lake Erhai, China.Laboratory work is undertaken at RIHN. Our project isorganized into five research groups, plus executive andadvisory groups, as follows: The Human AlterationsGroup investigates the effects of anthropogenicenvironmental alteration on the emergence and spread of KHV and thebehavior of its host Cyprinuscarpio carpio.The Pathogen and HostEcology Group defines the biology and ecology of KHVand carp, and so describes the environmental factorsinvolved in KHV infection and transmission.The Ecosystem ImpactsGroup examines the process of infection and theeffects of KHV disease on ecosystem functions such as materialcycling. The Economics and Culture Group investigates the losses associated with KHVdisease, including of ecosystem services or other economicand cultural phenomena, and describes the socialattempts to redress those losses. The Feedback Groupexamines the human response to losses caused by KHVdisease, and the environmental change associated withthis response. The Executive Group coordinates theactivities of each group and develops the model ofpathogen-human  interactions.Finally, an Advisory Group composed ofrecognized experts in relevant fields makes suggestionsin order to improve the research.

 

Perception and contribution to global environmental problems 

     Field surveys are being conducted primarily at Lake Biwa, Japan, where researchers from various disciplines and fishermen have accumulated much data, and at Lake Erhai, China. China is responsible for almost the entire global carp production. Lake Erhai is an inland lake in China that has never experienced an outbreak of KHV. We will create a model to predict the outbreak and spread ofKHV in Lake Biwa by accumulating and synthesizing both new and existing data from Lake Biwa.  The model will be applied to Lake Erhai to provide suggestions for how to manage the lake to lessen the probability ofan outbreak of KHV disease. The practical application of this model to such an important region is critical to attenuating the global problem of KHV disease.  The Lake Biwa model will be modified to apply to other infectious diseases in other areas, to suggest environments that might prevent the outbreak and spread of infectious disease, and to demonstrate how to facilitate the safe coexistence of humans and pathogens.

Main results to date

 

1) We found that gentle gradient lakeshores provide a wide range of thermal conditions, suggesting that fish can choose tempertures to alleviate stress associated with unfavorable water temperatures, and thus reduce susceptibility to KHV (Yamanaka et al., 2010).

2) We established an innnovative method to quantitatively detect KHV in natural environments (Minamoto et al., 2009;Honjo et al., 2010). The method revealed that since it was first detected in 2003, KHV is now found throughout the Lake Biwa ecosystem, including in plankton and sediment, lagoons and ponds, and now in almost all the rivers in Japan. We demonstrated that it is impossible to eliminate KHV, but that precautionary environmental management can eliminate

　"fertile" disease environments.

3) We have developed a preliminary break-through method allowing determination of the number and location of carp in their natural environments.

4) We found that breeding habitats can became hot spots for transmission of infectious diseases if hosts aggregate for mating and pathogen activation occurs during the host breeding season (Uchii et al., 2011) .

5) We developed a non-invasive method (i.e. a method that does not require handling fish) to quantify how water conditions stress carp. Using this method we found that changes in water temperature do induce stress.

6) We applied a Based on our assessment of KHV disease in Lake Biwa, we applied our conceptual model of linked environment-pathogen-human interactions to Lake Erhai, China, schistosomiasis in Kenya, fish diseases in the Ping River at Chaing Mai, Thailand, and Legionella disease (Yamaguchi et al., 2010), MRSA, Norovirus disease, and nontuberculous mycobacteria disease (Ichijo et al., 2010) in Japan. These applications helped us understand how pathogens interact with humans and suggested enviromental conditions that might prevent disease outbreaks and spread as well asstrategies for safe coexistence of humans with pathogens.

7) By combining the results from each work group, ranging from molecular biology to envirnmental sciences to human society, we are providing evidence to support the hypothesis that anthropogenic encironmental changes promote disease outbreaks.

8) We have presented our findings at national and international conferences of the linkages between the environment, pathogens and humans, emphsizing their significance to preventionand control of infectious disease.

Research objectives in 2011

 

1) Refine a method to quantify carp spatially and temporally and innovative method to describe our aonceptual model of environment-pathogen-human linkages including a deveropment of micro-device capable of in-situ measurment of KHV incidence and infectivity.

2) Determine the environmental factors involved in KHV abundance and its infectivity, and in carp population dencity and its susceptibility.

3) Conduct controlled experiments to reveal the relationship between water temperature, carp stress and susceptibility to KHV.

4) Assess the economic and cultural impacts of carp die-offs.

5) Apply the conceptual model of environment-pathogen-human linkage to other infectious diseases; KHV disease in Lake Erhai, China, Schistosomiasis in Kenya, fish deseases in the Ping River at Chaing Mai, Thailand, and Legionela disease, MRSA, Norovirus desease, and nontuberculous mycobacteria desease in Japan, and then describe the common parameters of KHV disease and other infectious diseases.

6) Continue to explore evidence that anthropogenic environmental changes can mediate disease outbreaks.

7) Synthesis of results of the work groupes in order to develop a set of recommendations desined to minimize the emergence and facilitate the safe coexistence of humans with pathogens.

8) Publish our results in international journals and books in order to disseminate the concepts and practical measures that can aid the control of "fertile" disease environments.

9) Organize a national and international symposium on environment-pathogen-human linkage to develop a network for this field of study.

 

  

Scheduled Research Activities in 2010

 

1) Develop a method to quantitatively detect KHV in sediment, organisms and other elements in aquatic ecosystems.

2) Clarify the distribution of infectious KHV in Lake Biwa.

3) Develop a micro-device to measure the quantity and infectivity of KHV in situ.

4) Determine the environmental factors involved in KHV dynamics and infectivity.

5) Use outdoor experimental tanks to define optimum water temperature for carp.

6) Describe the environmental characteristics of the places where KHV and carp interact, and clarify the behavior of the KHV-infected carp in order to reveal the locations where infection likely occurs .

7) Conduct controlled experiments to reveal the relationship water temperature and carp stress and susceptibility to KHV.

8) Demonstrate the ecological effects of carp on species composition in experimental ponds.

9) Evaluate the cultural and nutritional value of carp as a human food.

10) Assess the economic and cultural impacts of carp die-offs.

11) Create a preliminary model of the interactions between environmental change, KHV and humans.

12) Survey the spatial and temporal distribution of water temperature in Lake Erhai in order to establish the applicability of Lake Biwa findings to Lake Erhai.

13) Describe the common parameters of KHV andother infectious diseases.

14) Promote collaboration with the DIVERSITAS program of international biodiversity science.

15) Develop a set of recommendations to prevent or minimize the emergence and spread of infectious diseases.