Dr. V. I. Bishor
Research & Development Wing
Institute of Animal Health & Veterinary Biologicals
WHO defines Zoonoses
“Those diseases and infections which are naturally
transmitted between vertebrate animals and man”
According to Taylor et al. who in 2001 cata-
Zoon: Animals , Noses : Diseases.
logued 1,415 known human pathogens, 62%
were of zoonotic origin.
Rudolf Virchow was the first to use
most emerging infectious diseases in humans
the term in his Handbook of
History of Zoonoses
• Zoonoses have affected human health throughout times
• A possible epidemic of bubonic plague was described in the Old Testament, in the First Book
of Samuel. The so called Black Death emerged in the 14th century and caused vast losses
throughout Asia, Africa, and Europe. The epidemic, which originated in the Far East, killed
approximately one third of Europe’s population
• Rabies was described in Mesopotamia, in hunting dogs, as early as 2,300 BC. Recognizable
descriptions of rabies can also be traced back to early Chinese, Egyptian, Greek, and Roman
• Ancient accounts and modern hypotheses suggest that Alexander the Great, who died in
Babylon in 323 BC, died of encephalitis caused by West Nile virus, a virus that has a wild bird
In India 80 % of the population residing in approximately 575000 villages and
thousands of small towns.
Have close contact with domestic /wild animals population owing to their
occupation. Stand at greater chance of acquiring zoonoses.
Zoonoses Vs Major Killer diseases
Disease Death in Millions Disease Death
Pneumonia & Respiratory 3.5 Rabies 40000
Infections Yellow fever 30000
AIDS 2.3 JE 10000
Diarrhoeal Diseases 2.2 Ebola 1000
Tuberculosis 1.5 Monkey Pox 1000
Classification of zoonoses
Direct Zoonoses: Single vertebrate host: Rabies
Cyclozoonoses: More than one vertebrate host:
Taeniasis, Hydatid disease
Metazoonoses: Requires both vertebrate and invertebrate host
Saprozoonoses: Inanimate reservoirs and vertebrate host.
Anthrapozoonoses:: Animals to man
Zoo anthroponoses: Man to Man
Eg : Human TB, Amoebiasis
Amphizoonoses: Man Animals
Eg: Streptococcal infections
Factors affecting Disease emergence.
1. Introduction of a new host species in to an ecosystem.
2. Introduction of infected host in to new ecosystem.eg : Marburg Disease
3. Change in population dynamic
4. Ecological changes that bring two previously sepearted ecosystem into
contact. Eg. Trypansomiasis.
5. Change in habits including the food habits.
6. Technical changes brought about by man . Eg : Anisakiasis.
7. Mutation /genetic recombination of infectious agents . Eg Influenza.
Role of wild animals and Birds
The ecologic changes influencing the epidemiology of zoonoses with a wildlife reservoir can be of natural or
These include, but are not limited to,
Human population expansion and encroachment, reforestation and other habitat changes, pollution, and
The movement of pathogens, vectors, and animal hosts: Such movement can, for example,occur through hu-
man travel and trade, by natural movement of wild animals including migratory birds, and by anthropogenic
movement of animals.
Movement of infected wild and domestic animals is an important factor in the appearance of rabies in new
Microbial changes or adaptation : These changes include mutations, such as genetic drift in viruses; activation
and silencing of genes; genetic recombinations, such as genetic shift in viruses; and conjugation, transforma-
tion, and transduction in bacteria. Natural selection and evolution also play a role.
Severe acute respiratory syndrome (SARS) is a current example of likely microbial adaptation. This viral respi-
ratory illness, caused by SARS-associated coronavirus, is believed to have emerged in Guangdong, China, in
November 2002. SARS was first reported in Asia in February 2003, and over the next few months, the illness
spread to a global epidemic before it was contained. According to the World Health Organization, 8,098 cases,
including 774 fatalities, have occurred. The virus has an unknown reservoir, but wildlife is a likely source of
infection.Natural infection has been demonstrated in palm civet cats in markets and also in raccoon dogs, rats,
and other animals indigenous to the area where SARS likely originated.the live market and Restaurants in
china sold small carnivors and several species of civet cat.
Bush meat in Africa: a serious problem for the emergence of infection. (eg Ebola infection from Chimpanzee,
Incidence of HIV 2 from sooty mangabeys)
New Brucella spp. from marine mammals: The pathologic role of marine Brucella spp. in animals remains unclear, as
does their zoonotic potential. In 2003, two human cases of community-acquired granulomatous central nervous
system infections caused by marine Brucella spp. were reported
Brucella abortus/suis: occupational disease
Brucellosis Brucella melitensis: Foodborne.
Prevalent in most countries. Vaccination and brucellosis.
In India annual loss of Rs 350 Million S19 vaccine is infective. Avoid accidental inoculation.
due to brucellosis. RB-51 lacks LPS; so undetectable by common lab
Control tests. This strain is Rifampicin resistant, which is the
drug of choice in humans. Infection followed by the
Test and slaughter policy accidental inoculation of RB 51 have reported in US.
Immunisation: S19 Vaccine, RB-51 ,
45/20 vaccine, Rev 1,
Treatment in man
Anthrax Control in Man
20000-100000 human cases per year in the world. Immunisation
90-99 % are cutanious anthrax. Animal Industry hygiene and management
Potential Bioweapon( Pulmonary form of Anthrax). Medical care and management.
Common in southern part of India.
Control in animals.
Suitable disinfectant Immunisation
3 % peracetic acid. Proper carcuss disposal
3-5 % formaldehyde. Care in handling livestock
Most common infectious cause of death in the Mycobacterium tubeculosis which is virulent
world.The disease kills 3 million people a year, for humans but not for cattle.
with 7.3 million new cases annually. M. bovis in infective to man.
In india about 40 % of the population is infected Infection of cattle by human strain is usually
with TB. 2 out of 5 TB cases are found in india. self limiting and no cow-to-cow or cow-to-man
About 5 lakh people in india die every year of TB, trasmission.
more than 1000 every day- a patient per minute. M. Bovis can infect other animals as well as man.
Man may also act as a reservoir for bovine bacilli.
In india TB prevalent among cattle, Buffaloes and
and can transmit to cattle.
pigs. only 0.1 % of total cases are due to M. Bovis
(USA). Data not avialble in India.
Leptospirosis Primarly a disease of animals. Control
Organism isolated from almost all Man is the Dead-End host., also act Rodents control
free living species of animals. as a reservoir. sanitation
In india disease is wide spread in Rodents and mammals acts as natu- proper management of
Andaman, AP, Karnataka, Kerala, Animals
Tamil Nadu, W. Bengal. Immunisation
They excreate leptospira for about 1 Personal hygiene and
In Kerala L. grippotyphosa appeared
to be the common serotype.
year in rodents and weeks -months protection
in other animals. Health education
Reemerging in many part of India.
Primarly a disease of Rodents.
Domestic rodents-rat flea-man
Wild rodent-flea/direct contact -man
Low temperature and High humidity
Wild rodent-flea-domestic rodent-flea-
favour the pathogen.
Dogs acts as sentinel animals. man
Rabies Control of Animal Rabies
1. Immunisation of dogs should reach atleast 80 %of the
Obstacles in Rabies control population in higly endemic areas identified through a
1. Absence or insufficient enforcement of existing good surviellance system based on a network of diagnos-
legislation on animal rabies control( especially tic laboratories
for dog vaccination and control of dog 2. Responsible pet ownerships including dog registration
movementand population) and dog population control such as sterilisation, use of
2. Lack of affordable and high quality biologicals
hormones, elimination of unwanted dogs .
for both humans and animals.
3. The status of certain Rabies -free areas should be
3. lack of cooperation between the various
national sectors/agencies/disiplines concerned
maintained through strict implementation of national
with Rabies control and lack of involvement of and international regulations on animal movement.
NGOs which could contribute to rabies control 4. Community participation through the establishment
4. Lack of facilities and trained staff for the treat- of community funds, mobilisation of community
ment of bitten and rabid patients. volunters during vaccination campaign should be pro-
Control of Human Rabies
1. Government should allocate sufficient funds to procurement of human rabies vaccine and
immunoglobulins to be given at no cost to indigent risk bite cases.
2. Revised national guideline for pre and post exposure treatment based on WHO recom-
mendation should be issued.
3. Training for health personals for post exposure treatment and handling of rabid patients
should be provided, including health education with emphasis on precautionary measures to
be taken to prevent potential transmission within family members when a rabid patient is
cared for at home.
4. Pre exposure treatment of Children which may easily come in contact with dogs and cats
of unknown origin when the family can afford it , sholud be considered
Most important cause of viral encephalitis in
eastern and southern Asia.
30000-50000 cases reported annually.
Of these about 25-30 % are fatel and 50 % reuslts in
premanent neuropsychiatric sequelae.
Major vector: Culex tritaeniorhynchus.
The virus exists in a zoonotic transmission cycle
A disease of rural population. with between mosquitoes and pigs and /or water birds.
culex Tri. breeding in rice paddies and Human get infection by the bite of mosquitoes and
pigs providing the main source of blood are dead-end host.
1. MOSQUITO CONTROL
2. AVOIDING HUMAN EXPOSURE
Inactivated mouse brain vaccine, in china a live attenuated vaccine SA 14-14-2 strain is
Toxoplasma gondii : Possibly the most wide spread & prevalent protozoan parasite on earth.In many
countries the seroprevalence for women of child bearing age ranges between 30 and 45%. Seroprevalence is
reported from almost all animals. Beef is not a major source of infection to humans. In US studies shows that
25% of the house cats were seropositive for toxoplasms.
Sarcocystiosis: Herbivors are the intermediate host and carnivors and humans are the definitive host. Hu-
man get infection by the consumption of uncooked beef or pork.
Giardiosis: infect 2-5 % of the people. companion animals may be a good sourse of infection.
Cryptosporidiosis: only C. parvum is zoonotic. An emerging problem in HIV patient . Sourse of infection
may be calves, sheep, goat, deer, horses, dogs, cats and turkeys.1n 1993 a severe outbreak in USA : more than
403000 cases were reported. 12-27 % prevalence in HIV patients worldwide.
F. hepatica, liver fluke of cattle affects about 2.4 million people worldwide.
Clonorchis human liver flukes, a parasite of fish affects about 20 million people world wide , mainly in
far east Asia.
Taeniosis is a common problem in Asia and Africa. Neurocysticercosis alone causes more than 50000 deaths
Echinococcosis, where the humans are the intermediate host
Trichinella: a cosmopoliten helminth zoonosis. infection from meat of infected pigs, wild boars, horses, dog.
Anisakiasis: larvae of Psedoterranova decipiens, a nematode parasite of marine manmmal.
also with larvae of Anisakis. which infect sea fish. Tingling sore throat syndrome and ulceration of gut.
The inability of the non-industrialised
Major cause of human intestinal diseases.
countries to keep pace with the population
Can be Infection/Intoxication
Infections: Salmonellosiss, Brucellosis, growth, migration to rural to urban areas
Camphylobacter , Listeriosis,E. coli and the demand for clean safe drinking
Intoxication: Bacillus cereus, Botulism, water and proper sanitation are the rea-
sons for food borne infections
Consumption of raw or undercooked
meat, crustaceans and fresh water 1. Through heating and rapid cooling of food
fish and veghetables facilitate 2.Avoid raw or undercooked foods
transmission of food borne 3.Pasteurise milk and avoid post
infections. pasteurisation contamination
4.Proper sanitation at the farm and also in
the processing plant
Control of food borne 5.Water sanitation
infections 6.Sanitary disposal of faeces
7.Avoid toxin containing fishes like puffer
8.Refrigerate fish immediately after catch
9.Proper surveillance of food poisoning
10. Public education
• Influenza: Mainly by Influenza A virus causes pandemic in humans. Usually the transmis-
sion of avian or Animal influenza to man require a reassortment between human and avian influ-
enza viruses.Such events occured in 57 and 68. in 1997, Hong Kong, new sub type H5 noticed in
which all the genes of the virsus were derived from chicken influenza virus that was apparantly
circulating among the chicken market of Hong Kong. Again in 1999 another outbrake with
another type of Chicken influenza virus in man occured.
The virus is of great concern in view of the potential for reassortment with a human influenza
virus which will produce a virus with high human transmissibility which is compleate novel to
the world. The recent (2004) infections are caused by H5N1 avian virus.
• Filovirus: Ebola and Marburg, human infections from monkeys.
• Hendra : First reported in Horses in 1994 in Australia. Bats may act as
• Nipha (Barking Pig Syndrome): ( Named after village Sungai nipha in
Malaysia) reported in pigs from Malaysia during 1998 causing viral encephalitis in
humans ( 265 cases and 105 death.).Pigs, dogs and humans were infected.
• Hantavirus: HFRS, HPS. Rodent reservoir, aerosol transmission, reported from Asia and
Bovine spongiform encephalopathy (BSE) in the United Kingdom may provide
more lessons than any other recent emergent zoonotic disease episode.
The disease was first diagnosed in the United Kingdom in 1986; as of 1997, more
than 170,000 cattle had been reported as infected, but modern statistical meth-
ods have indicated that about one million cattle had been infected, roughly half
of which entered the human food chain in the United Kingdom
In 1995, the BSE agent was reported to be the cause of a new human zoonotic dis-
ease, new-variant Creutzfeldt-Jakob disease. By 1997, 26 cases had been re-
ported in the United Kingdom and one in France.
A recent report from The Royal Society states that there is now a compelling case
regarding new-variant Creutzfeldt-Jakob disease as the human manifestation of
BSE. With such a small number of cases, it is impossible to predict future num-
bers of cases of the human disease,
BSE may be instructive in other ways, especially in its extension into the worlds of
macroeconomics, international trade, political science, and even global gover-
Zoonoses and Immune status
Immunocompromised persons , Elderly people, HIV patients, Patients under cancer treatment are
more suceptible to zoonotic infection.
Enteric infections by Salmonella, Camphylobactor and Cryptosporidia may result in life
threatning Diarrhoea in these group.
Systemic infections like Toxoplasmosis, Tuberculosis, Cryptococcosis, Q fever and Cat Scratch
Fever may lead to fatel encephalitis and /or Pneumonia.
Always seek the advice of a Veterinarian while selecting a pet
Xenotransplantations and Zoonoses
Xenotransplantations is the use of animal Management
organs, tissues or cells for transplantation into
humans to treat a variety of medical conditions.
1. Development of Xenotransplant-grade
Domestic pigs are considered the most likely animals which meet the exacting microbial
sources for transplantable organs, tissues and agent status.
cells. 2. The implementation of a comprehensive
The risk factors health surveillance and clinical investigation
1. The systemic presence of agents. programme for timely detection and response
2. The latent sequestration of agents in a to infectious diseses occuring in xenotransplant
xenotransplanted organ( Salmonella , source of animals and colonies.
Mycobacterium) 3. Strict application and monitoring of
3. Agents contamination of a xenotransplant
husbandry and biosecurity practices.
during harvesting procedure.
4. Support the development and refinement of
Eg: Toxoplasma, Trichinella, Cryptiosporidium,
Viruses like Influenza .
Zoonosis -An International problem
Most tremendous impact on evolution of man especially on societies/culture that
domesticated and bred animals for food and clothing.
Most frequent and dreaded risk to mankind.
Transcend natural boundries, occur world wide
Impact on global economy and Health Importation of disease
Ban on animals and Animal products
Global surveillance in necessary
Inter relationship among countries has led to the internationalisation of control effort to
technical, Economical and Social fields.
Zoonoses Control: General Strategies
Procure personels Training, allocation
Hygiene in animal production
Alter agricultural practices Disposal/recycling animal wastes
Type of Husbandry Law
Establish/modify regulations Ordinences
Procure facilities Severity of unrecognised, untreated diseases Export/import
Prevalence/incidence of diseases
Epidemiological conditions Importance of carriers, subclinical infections
Medial/public health Routs of Transmission
Intesectoral Veterinary/agricultural/wild life Density, composition, activity
Ensure awareness of high risk people Literacy rate
Human factors Economic values of Animals
Social value of Animal
International/regional Information Exchange
Procure equipment, material
Control of Zoonoses: strategies and tactices for control in Animals
Infected/contact animals destroy
Uncontrolled , owned suceptible identification
Control of animal
capture / euthanize
populations. Stray suceptible animals
consider if pests or commensal
Wild vertebrate reservoir Hunt, trap, poison,antifertility
Vectors environmental/ecological control
chemical/biological agents/fertilty control
prophylactic treatment Chemotherapy
change conditions, population Change Husbandry
quarantine of animals Entry to disease free area.
Maintain Disease free /products/feeds Treat animals
status Control animal movement
protect animals at risk Control factors of environment
Control of Zoonoses: strategies and tactices to Control vehicles of Transmission.
control risk factors associated
with water, feeds, land, presonal.
Hygiene in animal
production proper use of drugs,
Develop and follow proper meat
hygiene. Hygiene at slaughter inspection, judgement, and Hy-
safe collection of milk, eggs,, seafood
Hygiene in handling and
processing foodstuffs safe handling, processing
storage, marketing of foods.
Ensure safety of other
animal products(wool, Hygiene during collection, storage,
hide, horn, bones, fat) processing, transport
Safe collection systems,
rendering plant operations,
Safe disposal or use of product safety
animal carcusses and Animal Carcuss disposal
Ensure safe disposal by burning
wastes. or burial
Control hazards to water supplies.
sites/vehicles/persons Excreta/garbage disposal Recycle safely as fertilizer, fuel,
Control of Zoonoses: strategies and tactices applicable to man
Protect high risk 2. Immunisation, chemoprophylaxis.
groups 3. Monitoring health status, including
occupational health program
1. Medical intervention, isolation
Prevent spread by man 2. Prevent environmental contamination
3. Prevent food contamination
4. Prevent animal contact
1. Imrove diagnosis
Treat 2. Laboratory diagnosis
Man Diagnose Improve diagnostic 3. Feedback to epidemiological and
services control services
infection 4. Referral capability
1. Referral capability
Establish facilities and 2. Monitor treatment outcome
Treat disease therapeutic regimens 3. Feedback to epidemiological services.
Role of Public helath Veterinarians.
1. Diagnosis, treatment, control and erradication of zoonotic diseases of major human
2. Use of biologicals(vaccines/sera) for prevention /control of zoonotic diseases.
3. Development and testing of newer drugs for important zoonotic diseases’ treatment.
4. Preparation of strategies and methods for the surveillance and control of important
5. Development of suitable animal models for important zoonotic diseases.
6. Supervision of food hygienic practices in slaughterhouses, dairy frams and other food
7. Production of wholesome and safe foods of animal and non-animal origin.
8. Investigation of food borne and other zoonotic disease.
9. Statistical reporting of morbidity and mortality of food borne and other zoonotic diseases.
10. Epidemiological studies on zoonotic and food borne diseases.
11. Participation in environmental health programs.
12. Notification to higher authorities about a notifiable disease/exotic disease.
13. Health education to public about the source of infection, mode of transmission, personal
hygiene, environmental hygiene and control measure against commonly occuring
14. Collaboration in medical relief during calamities and diseses.
15. Maintain close coordination with medical and public health department.
16. Conduct periodic meeting to review situation on the prevalence of zoonotic diseases in an
Public Health Implications of emerging Zoonoses.
Morbidity and Mortality of new, emerging zoonoses
Large out break : Tip of the iceberg : gross under reporting of infections through out the world.
for eg only 10-30 % of the salmonella infections are reported even in developed countries.
Invisible Diseases: Some disease may not be recognised as Zoonotic at the outset. these disease
can spread undetected from many years particularly if the incubation period is too long or the
number of cases in human or animals is too small, as happend in case of BSE/CJD and Nipha Virus.
Influences on public health practices and structure.
The threat of communicable Disease: Threat of spreading infection like Ebola from rural areas to
larger cities. Risk of introduction of infections in other continents- a threat whole world. The Ebola virus
attack contributed greatly to promoting the concept of emerging communicable disease among public
health officials, stressing the renewed importance of microbes and the need of surveillance.
A strong support to the opinion that the emergence of a killer disease in avery remote area of the world represent
as threat for all humans, therby reinforcing the sense of belonging to the same world.
Pandemic planning: Sharing and cross over of animal pathogens can cause a pandemic as we learned
from the Influenza outbreak in Hong Kong.
Global Alert and Response: Regarding the new infections and reservoirs. WHO/FAO/OIE/PAHO/
Uncertain Risks and precautionary Principle: for eg BSE Crisis changed the feeding method of
Animals, introduced major rearrangement in the food safety issues, questioned the safety of using animal
tissues for the production of human biologicals and medical devices( remember our sheep brain vaccine),
This particular disease has led to the renewal of an old concept” The precautionary principle”
Intersectoral collaboration for the control of zoonoses.: Need of high leval of Governmental
commitment for the containment of infections and Co-ordination between Medical and Veterinary health
Who will be the world’s expert on Zoonotic diseases?
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