《主催者および座長メッセージ

ORGANIZER & CHAIR MESSAGE》

保全医学と生態系の健康
Conservation Medicine and Ecological Health日本大学 生物資源科学部 教授／よこはま動物園ズーラシア 園長／
日本野生動物医学会 会長・村田 浩一

Koichi MURATA, PhD, Professor, College of Bioresource Sciences, Nihon University,Director, Zoorasia Yokohama Zoological Gardens
President, Japanese Society of Zoo and Wildlife Medicine
Hello everyone. I am Koichi Murata, President of thehealth. It is an interdisciplinary approach that reaches

Japanese Society of Zoo and Wildlife Medicine, and I

into a variety of research fields including political andwill be acting as the coordinator of today’s symposium.

social issues. It involves NPOs and ordinary citizens
rather than scholars, per se.

Let me begin by saying a big “thank you” to all of you
for coming. It is wonderful to see so many people here

The core aim and target of conservation medicine is

despite it being a cold Sunday morning.

the protection and preservation of biodiversity because
maintaining biodiversity is extremely important. I’

First of all, I would like to speak to you about them sure you have all had many opportunities to hearpurpose and intent of this symposium project. Thethe word “biodiversity”. The mass media takes up

theme of the present symposium is “One World, One

the subject frequently and in 2010 an international

Health.” In other words, conservation medicine is anconference called the ‘COP 10 (The 10th Conference ofacademic and research discipline aimed at the concept

the Parties to the Convention on Biological Diversity)’that the entire earth has its own health.

was held at Nagoya. But what exactly is biodiversity?
And why is it so important? When we ask theseNow, what does conservation medicine actually consist

questions again, we see that there are some areas thatof? In all probability, most of you here are hearing theremain unclear.

term “conservation medicine” for the first time. Thatis reasonable and totally understandable because theAs this figure indicates, the global environment isdiscipline of conservation medicine was not pioneered

facing many threats at present. The red marks show

here in Japan but in North America, where it was firstthe causes of this critical situation. Among the criticalestablished just 15 years ago in 1997.

factors harming the Earth that we hear about often are
climate change (or global warming), the eutrophication

This slide shows how conservation medicine is aimed atof lakes, and the problem of acid rain. But in fact itachieving human health, animal health and ecosystemis the disappearance of biodiversity itself which ishealth in a comprehensive manner that addresses theconsidered to be the single biggest risk to the Earthrelationship between all three. Put simply, the concept

at present. The entire global ecosystem itself may beof health does not exist individually and separately

endangered if that risk continues to increase. Actually,in people, animals or ecologically, but stems frombiodiversity is considered to have a greater effect on

their mutual relationships. This is a quite radical andthe global environment than is usually stated in theessential definition of health.

mass media.

Conservation medicine, which focuses on addressing

So what is the significance or meaning of protecting

these issues, is an idea that at heart pursues ecologicalbiodiversity? Up until now, various researchers and2nd Live Love Animals International Conference on Animal Care in Kobe 20127academics have tried to explain why it is so important.

species coexist. A specialized book has been written

A great many theories have been postulated and, amongon the subject, as is shown on the slide. In illustrating

them, the idea put forward by Stanford University

the dilution effect, Keesing took up the subject of

researcher Dr. Gretchen C. Daily of “ecosystem

Lyme disease, an infectious disease transmitted byservices” is considered particularly important. The

arthropods. Lyme disease is a zoonosis, meaning that it

idea behind ecosystem services is that protecting andis a disease transmitted between animals and humans.

preserving biodiversity can yield benefits for people.

It is actually a bacterial infection commonly spread

Accordingly, we must preserve biodiversity sustainably

by ticks. The disease-causing agents are bacteria

so that people can continue to enjoy the benefits ofbelonging to the genus Borrelia. Essentially, thebiodiversity. Personally I don’t like this idea very muchdisease is maintained through a relationship linking

because it is rather anthropocentric but, as a theory,the disease-causing bacteria, ticks and wild animals.

it has the merit of being very easy to understand andFrom time to time, people also become infected. The

is useful for providing a rationale for why biodiversity

disease causes a distinctive circular skin rash (known asshould be preserved.

erythema migrans), as well as flu-like symptoms suchas fever. Lyme disease is not life threatening although,These ecosystem services can be grouped into several

if treatment is delayed, symptoms can become severe.

categories. For example, there are so-called “culturalHowever it is not something we need to fear very much.

services,” so-called “conservation services,” andwhat can be termed “supply” services. Ecosystems

These days however, the incidence of people infected

are considered to provide various services that areby Lyme disease is spreading worldwide. In particular,

beneficial to people, and these services are related

many cases of infections are reported among urban

to each other. Among them are so-called “regulatingdwellers who go camping or pursue other outdoorservices”. These include such things as flood regulation,activities in the countryside.

weather regulation, and disease regulation. Or in otherwords, by conserving biodiversity we can enjoy theIn a short while I would like to talk in a little more

benefit of controlling diseases. So from this point ofdetail about the connection between Lyme disease andview, biodiversity is very important.

the preservation of biodiversity. But before that, I will
try to give a simple description of the life cycle of ticks.

Now I would like to speak a little more on the subject

Near the end of this symposium, I believe Dr. Goka ofof disease regulation, which is one of the points we will

the National Institute for Environmental Studies will

be discussing during this symposium. In the context ofbe talking about ticks. But in simple terms, ticks growdisease regulation there is a phenomenon called thethrough the larval and nymph stages by sucking the‘dilution effect’. What this means is that biodiversity

blood of many kinds of vertebrate animals, and then,has the effect of diluting the incidence of disease.

when they reach the adult stage they lay eggs. That’sFirst proposed by the ecological researchers Ostfeld

their life cycle in a nutshell.

and Keesing, this is now a fairly well understood andaccepted theory that mainly deals with the relationshipTo sustain their life, ticks require nutrition in the form

between the amount of biodiversity and the prevalenceof blood from mammals or birds. However, they don’of vector-borne diseases carried by arthropods such ast draw this blood from pre-selected hosts, but rather,ticks and mosquitoes.

they encounter a host animal at random and then begin
sucking its blood. They may end up drinking the blood

I would like at this point to explain the dilution effectof an animal whose blood is unpalatable to them and if

in some detail. The main idea is that certain kinds ofthe blood is unpalatable they may die, (or at least theirdiseases are kept under control where there is sufficient

growth may be retarded).

biodiversity, such as in environments where many8

りぶ・らぶ・あにまるず 神戸アニマルケア国際会議 2012

In the case of Lyme disease, it turns out that ticks

recently begun to spread in the human world, and in

harboring the bacteria that cause Lyme disease

most cases emerging infectious diseases are zoonoses.

are particularly fond of the blood of mice. It isA zoonosis occurs when a disease-causing agent thatwell understood that if they get the opportunity tois present in one or more species of animals newly

drink mouse blood, they grow very well and tend tocrosses over to infect and cause disease in humans. Asproliferate. This is a key point. For instance, let’s takethis map shows, most zoonoses originate in tropicala look at an environment model. There are lots ofregions such as Africa, South America and Southeast

animals here. This environment has lots of different

Asia.

kinds of animals that ticks feed on, and within it there
are some mice. But there are also animals not favoredThe reason is that originally in such areas, wildby the ticks that transmit Lyme disease, such as birds

animals, pathogens and vectors had been living quietly

and skunks. For some reason the blood of skunks

together in a delicate balance, but that balance became

appears to be particularly unpalatable. Ticks feed on

destroyed because of developments such as agriculture.

the blood of individual animals at random so in thisThe collapse of the relationships between wild animals,environment their chances of encountering a mousepathogens and vectors allows new infections to spreadare extremely low. As a result, their rates of growth andto the people and livestock that colonized the areas.

proliferation are not very high. But on the other hand,This map suggests that perhaps airplanes and ships

within a different environment where biodiversity is

carry diseases that occur in such places to industrialized

extremely low, (such as, for example, an environment incountries such as the nations of North America, Europe

which most animals are mice, with only the occasional

and Japan where they can spread further.

raccoon - a foreign exotic species), then most ticks willencounter mice, their favorite food source, and so their

On the other hand, there are some areas that are

rates of growth and proliferation will be high.

known as biodiversity hotspots. This slide shows thedistribution of rare animals, endangered species andKeesing and his fellow researchers conducted field

species indigenous to only a small area. Actually, manystudies to investigate how Lyme disease is actuallyrare species of wildlife are found where biodiversity

propagated in a species-rich environment. In this figure,is abundant and the environment is rich. The places

the horizontal axis shows the species diversity andmarked in red on the map are such hotspots and they

the ratio of ticks infected with Lyme disease is plotted

actually overlap quite well with the places I showedalong the vertical access. The environment on the leftearlier where new infectious diseases emerge.

is extremely simple with impoverished biodiversity
and with hardly any mammals apart from mice. WhenAs you are such an intelligent audience, I am sure you

ticks obtained from this environment were examined, ahave understood what I’ve said up to now. Although thelarge number of Borrelia bacteria, the pathogen causing

wild animals and pathogens living in these biodiversity

Lyme disease, were found on the ticks’ bodies. But

hotspots affect each other and the balance between

when the same kind of survey was carried out on ticks

them is delicate, under natural conditions things tendfrom within a biodiversity-rich environment, only a very

to work out somehow and diseases do not spread very

few were found to be carrying Borrelia.

much. But when people go into such places and exert
an influence on the environment or damage it with

Naturally, there are counterarguments. But on the otherdevelopment, this balance can collapse. And when thehand, there are reports that a similar dilution effect canbalance collapses, the pathogens can exert an influence

be observed in the case of West Nile virus and otheron livestock or people. In other words, we can say thatviral diseases such as the Sin Nombre virus. I’m sureby damaging biodiversity, people unleash a process ofyou have all heard of the term “emerging infectious

destruction that comes back to people again.

diseases.” These are infectious diseases that have

2nd Live Love Animals International Conference on Animal Care in Kobe 20129I’ve been taking about ecosystem services so far, but

researching tick damage to agriculture. Ticks are also

more fundamentally, unless people establish a bettervery important organisms in the environment, andrelationship with pathogens, vectors and wild animals,

probably the soil cannot be kept in a healthy condition

in my opinion we will not be able to maintain the earth’

without their help. This means that environmentss ecological health. This is one of the major reasons

without ticks are environments where people cannot

why we planned this symposium at this time.

live either. I would like everyone to realize this, and thatis why I have invited Dr. Goka to speak to us.

So, in order to spread understanding of this purpose
more widely, I have requested three lecturers to giveNow, I’d like to tell you about to the relationships I havetalks on the subject.

with these three lecturers.

The first lecturer is Prof. Michael Huffman, an associate

As for Prof. Huffman, although I have known hisprofessor at the Primate Research Institute, Kyoto

name for a long time, as I mentioned I first became

University. Prof. Huffman has studied self-medicationacquainted with him in a research context at anby primates, and specifically by the great apes. He

international conference held several years ago on

has observed that apes control their own bodies,

the non-human primate malaria parasite Plasmodium.

which means they can maintain their own health, heal

At that time, Prof. Huffman was also working as athemselves when they become ill, and even prevent

coordinator of the International Primatological Society

illnesses from arising in the first place. From before,(IPS). In spite of his busy schedule, he participated inI have read Prof. Huffman’s papers and specialized

the primate malaria conference, where he delivered

books with interest. I’ve invited him to talk to us todaya lecture. Perhaps because he was tired after that, Ibecause I thought it would be a good opportunity forremember he slept deeply during the conference.

us to learn about the intelligence of apes and about
their lifestyles, which are adapted successfully to theI met Prof. Tsuda for the first time five or six years ago.

environment.

Although my specialty was avian malaria, I was almost
totally ignorant about mosquitoes. I wanted to develop

Our second lecturer today is Prof. Yoshio Tsuda,

avian malaria research in some way by obtaining Prof.

a researcher at the National Institute of Infectious

Tsuda’s cooperation, so I have accompanied him onDiseases. Prof. Tsuda is proceeding with his research

fieldwork across Japan and carried out research withfrom a stance of looking at disease from the perspective

him as his co-researcher. Even today I receive guidanceof mosquito biology rather than that of the relationshipfrom him about mosquito biology, behavior andbetween mosquitoes and infectious disease. Whenclassification.

you think of mosquitoes, you may only be thinking
about how to squash them, but I think that if there isI have also been acquainted with Dr. Goka’s name foran environment in which mosquitoes can’t live, thenmany years. Perhaps you too are aware of his activities

perhaps it is an environment where people can’t live

through the mass media including TV. Althougheither. In this sense, I would like us all to learn how

he is extremely busy with his research, he actively

skillfully mosquitoes are engaged in their environment

participates in drinking sessions outside of researchand how important an element of the environment they

hours and he has developed a habit of taking photosare.

with his students. These are posted on Facebook. I
introduced one of these photos earlier showing him andDr. Koichi Goka, who is also a researcher at the National

me together. At this symposium too, he has been taking

Institute of Infectious Diseases, will give today’s lastphotos with many people, and these will also be posted

lecture. Dr. Goka is now working mainly on the controlon Facebook.

of invasive alien species. However, originally he was10

りぶ・らぶ・あにまるず 神戸アニマルケア国際会議 2012

Now it is time to hear the lectures from these threeacademics, which is the original purpose of thissymposium. First, Prof. Michael Huffman, please start
your talk now. I invite you all to enjoy his lecture.

【Slide 4】【Slide 1】【Slide 5】【Slide 2】【Slide 6】【Slide 3】【Slide 7】

2nd Live Love Animals International Conference on Animal Care in Kobe 2012

1112

【Slide 8】【Slide 12】【Slide 9】【Slide 13】【Slide 10】【Slide 14】【Slide 11】【Slide 15】

りぶ・らぶ・あにまるず 神戸アニマルケア国際会議 2012

【Slide 16】【Slide 20】【Slide 17】【Slide 18】【Slide 19】

2nd Live Love Animals International Conference on Animal Care in Kobe 201213