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Current Status and Measures of Zoonosis Control in Japan
Yasuhiro YOSHIKAWA
Graduate School of Agricultural and Life Sciences, The University of Tokyo
1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japane-mail: ayyoshi@mail.ecc.u-tokyo.ac.jp

Abstract
The main cause of human infectious diseases and public health threats these days has been thought tobe “emerging and re-emerging diseases” such as BSE, highly pathogenic avian influenza (HPAI), SARS, etc.
These infectious diseases were derived from pathogens from animals (zoonosis) and their products(food-borne infections). Recent zoonoses worldwide are reviewed here by origin, environment and relationship to human activities both in developing and developed countries. Emerging zoonosis is a kind of warning to humanity and we need to build ubiquitous, scientific zoonosis control methods acceptable to mostcountries of the world. The WHO and OIE serve as internationally responsible organs for disease control inhumans and domestic animals, respectively. I explain a path to global zoonosis control, recent experiencesin risk assessment and new measures for zoonosis control in Japan, which have been conducted concomitantwith renovation of the “Infectious Diseases Control Law” which was established about a hundred years ago.
The renovated law calls for cooperation between central and local government, between the MAFF (Ministry of Agriculture, Fishery and Forestry) and MHLW (Ministry of Health Labor and Welfare), and between
medical doctors and veterinarians.
Key words: conservation medicine, domestic animal, OIE, risk assessment, WHO, zoonosis

1. Introduction
Recently, the cause of many human infectious diseases posing a public health threat is considered to be
derived from so-called “emerging and re-emerging diseases.” These diseases are caused mainly by pathogens
originating from animals (zoonoses) and their products(food born infections). Particularly in tropical countries,
there are many factors causing an emergence of infectious diseases. These include the pathogenic agentsthemselves, their reservoirs (natural hosts) and vectors(intermediate hosts), which may be resident in nature.
The acceleration of expanding international tradeenhanced by the World Trade Organization (WTO),
especially in food products and exotic pet animals may
produce newly emerging diseases. Moreover, the aging
populations of the developed countries, increasing thenumber of people who are potentially more susceptible
to opportunistic infections, is also connected with anincrease in outbreaks of emerging and re-emerging
diseases. A wide variety of animal species, both domesticated and wild, has acted as reservoirs for thesepathogens, which include viruses, bacteria and parasites.
In nature, human beings are heterotrophic organismsthat depend on animals and plants as sources of nourishment. Most of our needs for protein and fat are supplemented by consuming the milk, meat, internal organs
Global Environmental Research
12: 55-62 (2008)
printed in Japanand other parts of domestic animals. Thus, we have had
a long relationship with domestic animals, some ofwhich were already living among us when our ancestors
started culturing the land 10,000 years ago. A look atthat history shows that almost all current infectious
diseases suffered by humans have had animal origins. In
other words, diseases such as smallpox, measles andinfluenza that were once thought to be unique to human,
all either originated in other animals or share common
ancestors with viruses infecting other animals. For
example, the smallpox virus is a relative of the cowpox
virus, the measles virus originated from rinderpest or
canine distemper viruses, and influenza virus is derived
from avian influenza viruses. There are also many
infectious diseases even today that can be transmitted
between people and domestic animals. We humans do
not inhabit a special world separate from that of otheranimals.

2. Diseases from Animals to Humans
Zoonotic infections are diseases caused by a pathogen that infects both animals and humans (but natural
hosts infected by the pathogen often do not suffer
adverse effects or sickness). They consist mostly of diseases passed on to humans from animals. Somezoonoses, however, originally passed on to animals from©2008 AIRIES56

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humans and then back to humans from the infectedanimals are called anthropozoonoses (e.g., dysentery,tuberculosis, viral hepatitis, and other diseases found in
non-human primates).
Zoonotic diseases include such well-known examples from ancient times as the plague, which is transferred from wild rodents (rats, prairie dogs, etc.) to
humans through fleas. It is by no means a disease of thepast and nowadays the plague is still prevalent in thecontinents of Africa, Asia and America. Rabies, which ispassed on to humans from infected dogs, bats and otheranimals, is reported to cause more than 40,000 fatalities
a year, and several tens of millions of people are postexposure vaccinated all over the world every year.
There are of course many other parasitic, rickettsial
and chlamydial, bacterial and viral diseases affecting
humans. In 1959, a World Health Organization (WHO)and Food and Agriculture Organization (FAO) joint expert committee listed over 150 such diseases, and now
there are thought to be 500-700 noteworthy diseases.
Infectious diseases that have sent shockwaves throughout the world in recent times include diseases of wild
animal origin such as Ebola hemorrhagic fever (HF),
Nipah virus infection, severe acute respiratory syndromecaused by a corona virus (SARS), and West Nile fever;diseases of domestic animal origin such as enterohemorrhagic E. coli infection (EHEC) caused by O-157,
bovine spongiform encephalopathy (BSE, a prion disease resulting in variant Creutzfeldt Jacob disease;
vCJD), and highly pathogenic avian influenza (HPAIV);and diseases of arthropod origin such as dengue fever
and dengue hemorrhagic fever. About two-thirds of all
viral diseases emerging in the latter half of the 20th century are zoonotic (Table 1). Infectious diseases ofTable 1

domestic animal origin such as toxoplasmosis, salmonella and campylobacter infections, hepatitis E, O-157
enteritis, Crimean-Congo hemorrhagic fever, bovine
tuberculosis, brucellosis, and BSE-vCJD also warrant
serious consideration from the food safety perspective
since they invariably spread through foodstuffs.
Retrospectively, it was in 1980 that the WHO declared that smallpox had been eradicated. Though it is
only one pathogen, this was the first time in history thatmankind had defeated a virus (though recently people
have voiced concern that it has not been completely
eradicated insofar as it continues to exist in the form ofsamples that might some day be used as pathogens inacts of bioterrorism). With the development of antibiotics, we also became able to suppress bacterial infections,giving rise to optimism about our ability to protect ourselves from infectious diseases. In Japan too, infectious
diseases that were long the top causes of death declined
rapidly after the 2nd World War, making way for cancer
to become the leading cause of death by 1951. As
circulatory disorders such as brain stroke and myocardial infarction became the second most prominent causeof death, Japan’s healthcare authorities (Ministry of
Health Labor and Welfare; MHLW) began to focus more
on welfare and countering cancer and lifestyle disorders,so called “metabolic syndrome,” rather than infectious
diseases.
However, new infectious diseases such as acquired
immune deficiency syndrome (AIDS) and various viralhemorrhagic fevers have emerged worldwide, and diseases such as dengue fever and tuberculosis have reemerged to become serious threats to human health once
again. Excessive use of antibiotics has given rise to the
spread within hospitals of antibiotic-resistant bacteria

Main emerging & re-emerging viral diseases (past 30 years).

* Black letters indicate zoonosis

Zoonosis Countermeasures in Japansuch as methycillin-resistant Staphylococcus aureus(MRSA), vancomycin-resistant enterococci (VRE),
vancomycin-resistant Staphylococcus aureus (VRSA)
and multi-drug-resistant Mycobacterium tuberslosis.
Given such developments, the WHO has revised its optimistic forecasts regarding the fight against infectious
diseases, and countries throughout the world havedeclared states of crisis with regard to infectious diseases. Since then, infectious disease control has become
a hot topic at summit meetings.

3. Factors Behind the Occurrence and Spreadof Zoonotic Diseases
The majority of zoonotic diseases can be traced todeveloping countries. The reasons for this include,
first, increased contact with pathogens carried by wild
animals in tropical rainforests and other natural habitats
concomitant with a development of the rain forest
resulting from human production activities (Ebola HF,
Marburg disease, monkeypox); second, a disruption of
ecosystems by rodents and other animals whose numbers have been elevated by increased human foodproductivity such as grain production (Bolivian HF,
Lassa fever, Argentine HF, etc.); third, establishment of
infectious diseases in cities of developing countries
which is normally circulate between monkeys andmosquitoes in forests, owing to rapid urbanization andpopulation concentration combined with poor urban
infrastructure (yellow fever, dengue fever, dengue HF,etc.); and fourth, rapid spread of infections from developing to developed countries as a result of the rapid airtransport of both people and animals during thediseases’ latent period (Lassa fever, Marburg disease,
SARS, etc.).
There are also factors contributing to zoonosis outbreaks in developed countries, such as keeping wild

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animals as so-called exotic pets (tularemia, plague,monkeypox, etc., transmitted by pet prairie dogs), andcontact with wild animals during outdoor recreationsuch as camping or forest walking (Japanese spotted
fever, scrub typhus, Hantavirus pulmonary syndrome
and Lyme disease transmitted by such animals as wildrodents and ticks, echinococcosis transmitted by foxes,etc.). New infectious diseases have also emerged indeveloped countries as a result of the pursuit of economic efficiency in the form of intensive factory farming and rendering of animal parts not consumed byhumans (animal offal) as sources of protein for feed(salmonella and campylobacter infections, BSE-vCJD,
EHEC by O-157, etc.). In recent years, moreover, we areseeing transmission patterns of a more complicated kind,such as the Hendra and Nipah viruses transmitted fromtropical fruit bats to humans through domestic animals
such as horses and pigs, respectively.
The chances of coming into contact with infectious
diseases transmitted by domestic animals such as pigs
(Nipah virus), horses (Hendra virus), cattle (BSE), or
chickens (HPAIV) are much higher than for those ofwild animal origin. Domestic animals are increasingly
raised for human consumption in large-scale factory
farms, and once a pathogen invades such an intensive
rearing environment, it can spread like wildfire, with thelikelihood that its frequent transmission among hosts insuch an environment will also facilitate genetic mutation,
making for a much more dangerous situation than in thepast (Fig.1).
Even among wild animals, we may be facing new
risks. For example, increasing environmental pollution
may reduce host immune functions, as a result of whicha virus that has up to now coexisted with a host suddenly begins to spread explosively (North Sea seal morbilli virus, etc.), or environmental pollutants may elevate
the frequency of virus mutations because the majority ofFig. 1 Risks of domestic animals.
(a) Nipah virus (killing pigs in Malaysia) (by the CDC)(b) HPAI (killing chickens in Japan)

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persistent organic pollutants (POPs) may have amutagenic potential. This kind of possibility suggests aneed for changing paradigms and taking actions different from earlier measures for suppressing zoonoses andavoiding risks. Conservation medicine is a new approach to the control of zoonoses that incorporates theconcept of environmental conservation in the consideration human and animal health. Thus, top down approaches from wildlife ecology and field science will
become more important than bottom up research such as
ordinal analysis of pathogens isolated from humans or
domestic animals, which are the final hosts of the infections.

4. Zoonosis is a Warning to Humanity
The way in which zoonoses emerge and spread ischanging in connection with the expansion of human
production activities, the pursuit of economic efficiency,changing lifestyles, and so forth. In this respect,
zoonoses have much in common with environmental
pollutants such as PCBs, DDT, and dioxins. There isnothing evil about pursuing comfort and convenience,but if in our anthropocentric pursuit of ever moreadvanced technology we continue to ignore the need forbalance and continue to destroy the environment andecosystems, we are doomed to suffer the consequences.
Attempts to resolve issues by pushing the contradictionsof developed countries onto developing countries or bya country just looking out for only itself are alreadyproving to be bankrupt. What is needed is global
cooperation among governments on countermeasures tozoonoses led by the WHO and Office International desEpizooties (OIE, now called “World Organization for
Animal Health”). National governments should also be
reminded that covering up or failing to report outbreaks,
issuing “all clear” declarations prematurely, and otheracts aimed simply at protecting one’s own country’s
economy or calming the populace will in the end only
raise the risks of a big outbreak (SARS in China,
Table 2Strategy for zoonosis control.

HPAIV in Southeast Asia, BSE-vCJD in the UK, etc.).
Even the USA, which has the most advanced infectious disease defense system in the world and is home to
the Centers for Disease Control and Prevention (CDC),
which play a leading role in controlling infectious diseases worldwide, has not had an easy time controlling
zoonoses like West Nile fever that are transmitted
through wild animals (birds and mosquitoes). West Nile
fever first appeared in eastern New York in 1999, infecting seven people, and by 2003, it had spread throughout
the country and still shows no signs of abating, with
infections now standing at over 8,000 and deaths at over200. The epidemic now involves Canada and Mexico.
The USA is also finding it extremely difficult to suppress plague, which is endemic to arid Midwest regions(being transmitted between prairie dogs and fleas),rabies transmitted by bats and Hantavirus pneumonia
syndrome (HPS) transmitted by wild rodents.
Meanwhile, the fact that SARS, which is thought tobe of wild animal origin (now it is considered to be derived from a kind of bat corona virus), spread throughout the world in a matter of months demonstrates thatnational borders and other artificial barriers are no
obstacle to modern infectious diseases. HPAIV-H5N1
has also spread from Asia to the Middle East, Europe,and Africa. The large number of countries involved, thebig scale and persistence of infections in Southeast Asia,and the virulence that has enabled it to infect humans
directly, have prompted the WHO to issue dire warnings
about the dangers it poses. In addition, however, toconventional downstream, end-result-oriented infection
countermeasures taken by the Ministry of Agriculture,
Forestry and Fisheries (MAFF) and MHLW, targetingpeople and domesticated animals, in the 21st century,
investigation is needed of zoonoses originating in wild
animals from a more upstream perspective that also
considers the environment and the ecology of pathogens
parasitizing wild animals and natural hosts in order todevelop more global countermeasures (Table 2).

Zoonosis Countermeasures in Japan

5. The Path to Controlling Zoonoses
Including pathogenic microorganisms, there are currently about 1.4 million known species on Earth(approximately 750,000 insects, 280,000 other animals,
250,000 higher plants, 70,000 fungi, 30,000 protozoa,
5,000 bacteria, and 1,000 viruses). When one considers
the complexity of the ecosystems that these organisms
have built up as the present-day descendants of
3.7 billion years of life on the Earth, it is impossible for
us humans to completely control zoonoses for the sakeof our own convenience. Basically we need to recognize
the importance of biodiversity and seek to achieve abalanced coexistence with other life forms.
Even so, we need to do what we can to control infectious diseases that endanger humanity. The organizations charged with responsibility for controlling infectious diseases on an international level are the
Geneva-based WHO for human infectious diseases, andthe OIE, headquartered in France, for infectious diseases
among animals and infectious diseases whose origins
can be traced to foodstuffs. Since OIE decisions
frequently directly affect the husbandry of domestic animals in all member countries (now 176 countries) andtrade in foodstuffs of domestic animal origin, the OIE
serves as an affiliate of the WTO.
The expert committees of these internationalorganizations frequently use risk analysis as an analytical method. This methodology was recently establishedand originally used to decide international safety criteriawith respect to humans for drugs, food additives, and soforth, but has come to be used also in the control of foodpoisoning and infection by microorganisms. Risk analysis is a field that merges natural science with social
science, and comprises three key aspects – risk assessment, risk management, and risk communication. Based

Fig. 2 The path to controlling zoonoses.

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on scientific, quantitative or qualitative risk assessment,
the risk managers or policy makers concerned consider
cost-effectiveness, cost-benefit or trade-offs of the risk,
etc., and draft a realistic plan that they explain to stakeholders in easily understandable terms (to get so-called
informed consent), and attempt to establish a more efficient defense system. In Japan after the BSE panic, theFood Safety Commission was established within the
Cabinet Office as a risk assessment organ independent
from risk management organs such as the MHLW and
MAFF. International organizations are already bringing
together infectious disease experts and government officials from different countries or regions in field-specificforums to consider measures for the sustained control of
infectious diseases.
However, the control of such infectious diseases isbasically a political and economic issue. As long as poverty, famine, and war continue, there is little hope for
improving public hygiene globally. The path to controlling infectious diseases is one of international cooperation in the building of standards and systems for global
defense against such diseases that also respect diversity
in the form of national and regional differences in culture, national character and everyday life and customs(Fig.2).

6. Japan’s New Zoonosis Countermeasures
After the postwar period of rapid economic growth
in Japan (1950s), drastic changes in Japan’s social system and values fueled trend towards nuclear families
and a declining birthrate, and pets as companion animals
came to serve as substitutes for people in the family.
Then during the economic bubble of the 1980s, in placeof the traditional species of pet animals, it became popular to import and keep so-called exotic animals. Japan’s

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birthrate declined and the population aged at a pace thatwas exceptional even among the developed countries,
and Japan also stood out from the rest in the quantity of
its wild animal imports. Under the MHLW’s emerging
and re-emerging infectious disease research project, thestatus of animal importation was first investigated withthe help of quarantine offices in 2000. Before that time,
importation data on domestic animals and dogs was covered by the MAFF, and those on dogs, primates andhoneybees were recorded by the Ministry of Finance fortaxation. Data on other animals, however, were not covered by any of the ministries. The survey results indicated that about 4 million live animals were imported
every year. They included about one million rodents,
2 million reptiles and 0.6 million birds and others(Table 3).
These changes in society and diversification in lifestyles prompted increasing concern over the possibility
that novel zoonoses would emerge. Therefore, when the
Infectious Diseases Control Law which was established
about a hundred years ago was enacted (effective from1999), in addition to diseases transmitted between
people, zoonoses were also considered for the first time
to be within the scope of the law and monkeys became
subject to legal quarantine. Veterinarians were obligatedto notify authorities when they diagnosed monkeys
infected with Ebola HF or Marburg disease. Concomitant with an expanded application of the Rabies Prevention Law, cats, skunks, raccoons and foxes in addition todogs also became subject to legal quarantine, as didmonkeys. However, no other infectious zoonotic diseases and animal species were subject to regulation atthat time, so when the Infectious Diseases Control Law
came up for revision five years later, stronger measures

were considered.
For the revision, data on outbreaks of zoonosis,
statistics on imported animals and disease risk assessment were obtained and analyzed. An MHLW zoonotic
disease study team carried out the first ever zoonosis
risk analysis on imported animals in Japan. Briefly, forthe prior five to ten years outbreaks of important zoonosis (about 50 diseases) worldwide were listed up (dataobtained from the OIE, WHO and commercial data baseof GIDEON) and each country’s risk status was categorized from negligible to very high in regard to eachzoonosis. Then, the number of imported animals fromcountries involved was classified from low (<100) tovery high (>10,000). The first-step risk level was classified from negligible to very high by combining the risk
status and number of imported animals in the country
concerned as a lengthwise and crosswise matrix. Then
quantitative risk points from zero to ten were calculated
by combining the first-step risk level and severity ofeach zoonosis among human populations (Fig. 3). The
total risk points of individual imported animal species
were summed up for each zoonosis risk point from eachcountry or area. If a certain animal species got high total
risk points, importation of the animal was banned, and if
the total points were relatively high, the animals werequarantined for one month or 21 days. For other animals,
notification of animal importation became obligatory
and certificate of purpose of breeding and pathogen-freecertification by an authorized veterinarian were needed.
As a result, a total import ban was imposed on all
Chiroptera (bats) and rodents of the Mastomys genus(the natural hosts of Lassa fever) from November 2003,
and requirements such as import notification, healthcertification, and regulation according to risk level wereTable 3 Animals imported into Japan per year (2000).

* AP means airport and P means port.

Zoonosis Countermeasures in Japanapplied to all other animals apart from prairie dogs (forplague control) and civet cats (for SARS control) whose
importation was already prohibited, and monkeys andcarnivores already subject to legal quarantine. In otherwords, unlike previous revisions which tended to simply
increase legal animal quarantines, the new revisionapplied import bans to certain species, and according to
the risk level, introduced stronger measures against
imported animals and indigenous wildlife (migratory
birds, crows, etc.) including surveillance systems,
investigation of animals in the event of outbreaks of azoonosis and stronger measures to combat zoonoses.
Particularly the animal import notification system andrequirements for health certificates and furnishing of
proof of non-infection with certain pathogens effectively
put a stop to the importation of wild animals that hadgone unchecked up to then, and this has proved to be aneffective alternative to quarantine as a means of
avoiding risks (Fig 4).

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With respect to wild and domestic animals within
Japan, everyday surveillance is important, which meansthat it is also vital to establish an organization for
diagnosing infections in animals. With regard to highrisk infectious diseases, there is a need to identify
high-risk localities or zones, localities in which animal
intrusion is likely, and habitats of wild animals carrying
the infectious diseases concerned, and take comprehensive measures to combat the spread of the disease, curb
the number and habitats of natural hosts and animal vectors, exterminate intruders, and so forth. This is a fieldthat calls for cooperation between central and local governments, between the MAFF and MHLW, and between
doctors and veterinarians.
Figure 4 bottom is posters for zoonosis control by
the new regulation of animal importation.
Left: Importation ban of mastomis and chiropters.
Middle: Flow chart of the newly established animal
importation procedure.

Fig. 3 Risk assessment of zoonoses in Japan.
1st : Risk status of the zoonosis concerned in each region or country
2nd : Annual importation data on living animals
3rd : Assessment of each zoonosis for its severity to humans

Fig. 4 Risk management for zoonosis control in Japan.

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Table 4 Effects of new zoonosis control on risk avoidance.

Right: New compulsory notification for importationof pet animals such as birds and rodents.

7. Validation of the Effect of New Zoonosis
Control on Risk Avoidance
Since the imported animal notification system was a
precautionary measure under risk assessment, verification of the system was conducted two years after the
introduction of the new zoonosis control system, i.e., fornotification of imported animals. From September 2005
(the starting point of the new measures) to August 2006
and from September 2006 to August 2007, the numberof annual live animal imports was calculated and compared with that of 2000.
It is clear that the number of imported animals drastically decreased, both mammalian and avian. Moreover,
the origin of animals shifted from wild caught topurposefully bred (Table 4). This was reflected inchanges in the order of exporting countries, i.e., before
2005 many animal species, including rodents, camefrom the Middle East, Near East Asia and African countries, but after 2005 the exporting countries shifted to
Far East Asia, European countries and the USA (data notshown). It appears that this risk assessment and precaution measures worked effectively to avoid the risk ofzoonosis outbreaks.

8. Prospects
Recently the main cause of human infectious diseases and public health threats has been considered“emerging and re-emerging diseases.” These infectious
diseases are mainly derived from pathogens from animals (zoonosis) and their products (food-borne infections). The zoonoses worldwide were reviewed by their
origin, environment and relationship to human activities

in both developing and developed countries. Emerging
zoonosis is a kind of warning with regard to humanactivities and we need to create ubiquitous scientific
zoonosis control methods acceptable to almost all countries of the world. The WHO and OIE are working as
internationally responsible organs for disease control inhumans and domestic animals, respectively. I have
explained herein a path to global zoonosis control andour recent experiences in risk assessment and measuresfor zoonosis control in Japan. The prospect’ for zoonosis
control are based on the Precautionary Principle andcrisis management which should be implemented bycooperation between central and local governments,
between the MAFF and MHLW, and between medical
doctors and veterinarians, as well as with collaboration
between countries and international organs.

Yasuhiro YOSHIKAWA
Yasuhiro YOSHIKAWA is a Professor of
Veterinary Medicine at the University ofTokyo Graduate School of Agriculturaland Life Sciences, in which capacity hehas served since 1997. He teaches laboratory animal science, toxicology andzoonosis at various universities. He
received his Doctorate in Veterinary
Medicine from the University of Tokyo and finished the PhD course in
Veterinary Pathology at the University of Tokyo in 1976. After that, heconducted research on viruses at the National Institute of Health of Japanand the Virus Institute of Giessen University as a senior researcher(1976-1979). He worked as Assistant Professor, Lecturer and Associate
Professor at the University of Tokyo Institute of Medical Science(1980-1990). He served as General Director of the Tsukuba Primate
Center of the NIH of Japan (1990-1996). He currently works as a memberof the Infectious Disease Committee of the MHLW and the Food Security
and Consuming Committee of the MAFF, and he serves as Chairman of
the Prion Expert Committee of the Cabinet Office Food Safety
Commission.

(Received 22 April 2008, Accepted 27 May 2008)