PREVENTION, CONTROL AND ERADICATION OF ZOONOSES

SHARON A J15 MVM 044

INTRODUCTION

The fundamental concept in prevention, control and eradication of zoonotic diseases is focused upon ‘breaking the chain of transmission at its epidemiologically weakest link’ in the infection cycle viz., controlling the reservoirs (animals), breaking the routes of transmission and immunization of susceptible hosts (human beings).

Epidemiologically weakest link in the transmission pathway

PREVENTION

• Prevention of disease in an epidemiological sense means all measures to exclude disease from an unaffected population of animals

• There are three types of prevention• Primary prevention• Secondary prevention• Tertiary prevention

PRIMARY PREVENTION

• Includes those activities directed towards preventing exposure to causal factors.

• Example: Quarantine and Vaccination.

SECONDARY PREVENTION

• Includes those activities designed to detect disease process as early as possible before clinical disease occurs.

• Examples• screening test to detect Tuberculosis, Brucellosis• Test slaughter and Depopulation

Milk ring test

TERTIARY PREVENTION• prevention by treatment.

CONTROL

• Strategy which employs all tactics useful for reducing the frequency of illness which are already present in a population

• It aims to reduce the mortality and morbidity caused by the disease.

• Effective control of a disease requires knowledge about its multifactorial causation, removal of the weakest link may be sufficient to control a disease.

CONTD..

• Host specific agents are easy to control example : Streptococcosis

• The infectious agents with wider host range or vector hosts may prove more difficult to control example : Paragonimosis

PARAGONIMOSIS, - MAMMAL-SNAIL-CRAB

ERADICATION

• Eradication is defined as the purposeful reduction in prevalence of a specific disease to the point of continued absence of transmission within a specified area by means of a time limited campaign

• (Andrews and Langmuir,1963)

ERADICATION: TERM IS USED IN FOUR SENSES:

• - To mean the extinction of an infectious agent. (Human Small pox)

- Reduction of infectious diseases prevalence in an area to a level at which transmission does not occur.

- Reduction of infectious diseases prevalence to a level at which disease ceases to be a major health problem, although some transmission may still take place.

- Refers to the regional extinction of an infectious agent

(Eradication of FMD in UK)

ERADICATION

• Means elimination of disease-producing agent from a defined population or geographical area

• Total Eradication: complete removal of the agent. example: small pox from the world.

• Practical Eradication: elimination of infectious agents from the reservoirs of importance to humans or their domestic animals in defined geographical area and making ‘Disease free zone’, rather than total eradication from the region.

• Example: (Eradication of canine rabies, where eradication of rabies from wildlife reservoirs may not be possible.)

BASIC PRINCIPLES OF DISEASE CONTROL

Source of

reservoirMode of transmis

sionSusceptible host

Focus on breaking the chain of transmission

1. Reservoir neutralization

2. Transmission from reservoir to susceptible host

3. Transmission between the susceptible host

RESERVOIR NEUTRALIZATION

• Early diagnosis• Cull infected animals • Manipulation of environment

Culling of birds during avian influenza outbreak

TRANSMISSION FROM RESERVOIR

Reducing contact potential

• Isolation and treatment of infected animals• Quarantine of susceptible animal• Population control

SUSCEPTIBLE HOST

• Increasing host resistance • Immunization• Chemo prophylaxis

APPROACHES EMPLOYED FOR PREVENTION &CONTROL OF

ZOONOSESQUARANTINETEST AND SLAUGHTERENVIRONMENTAL HYGIENEMASS IMMUNIZATIONVECTOR CONTROLRESERVOIR CONTROL

CONTD..

EARLY DIAGNOSISTREATMENT GENETIC IMPROVEMENTHEALTH EDUCATIONEPIDEMIOLOGICAL DIAGNOSISNICHE FILLING

QUARANTINE

• Quarantine: isolation of animals that are infected or suspected to be so or non-infected animals that are at risk. period depends on

- Incubation period - Time taken for infection to be confirmed - Time taken by infected animal to become uninfected

QUARANTINE

Limitation of freedom of movement of such well persons or

domestic animals exposed to communicable disease for

period of time not longer than the longest usual incubation

period of disease, in such manner as to prevent effective

contact with those not so exposed

-Park text book of preventive and social medicine

• The period of quarantine depends on 1) Incubation period of agent (15 – 30 d)2) Time taken for confirmation• for eg. isolation and identification of pathogen

• OIE was established in Paris in 1924 with a view to make uniform procedures for veterinary quarantine and developed appropriate regulations applicable throughout the world

CONTD..

• International quarantine the imported cattle are to be held at the port of entry for 90days

• Sheep and pigs 15 days

• The first organized quarantine on the movement of people was imposed by the republic of Venice in 1374 on plague exposed travelers.

• The first international livestock quarantine was put in use by US in 1890

MASS TREATMENT

• The mass treatment approach to disease control depends upon the availability of safe and cheap therapeutic agents.

• Antibiotics, anthelmintic and other drugs like hyper immune serum used (therapeutically)

• Administered (prophylactically) at times of high risk to prevent disease and thus to increase productivity.

• Example: sulfonamides in drinking water for coccidiosis in chickens.

SELECTIVE SLAUGHTER

• The deliberate killing of a minority of infected animals to protect the well majority of healthy population.

• The selective slaughter of diseased animals or reactors is to be found at by immunodiagnostic screening test.

CONTD..

• Affected animals - source of infection

• Slaughter ill minority of animals to protect healthy majority

• Surveillance through mass testing

Tuberculin test

SLAUGHTER:

• Affected animal can act as source of infection, also productivity reduces- so technically expedient to slaughter

-Test & removal strategy: Only reactive animals are culled. eg: bovine TB.

- Pre-emptive slaughter: Animals that have risk of developing disease are

slaughtered to prevent risk of an outbreak.

- Blanket slaughter: Animals in areas of close contact with affected area are slaughtered.

DIFFICULTY IN APPLICATION OF SLAUGHTER

1) High initial cost of operation2) Compensation3) High prevalence of disease - replacement stock is a

problem

EXAMPLE• Over 15,000 ducks had died at Thalavadi and Purakkad in the

Kuttanad area of Alappuzha district during the first two weeks of November 2014. the tests of samples of dead birds conducted in high security animal disease laboratory (HSADL), Bhopal, had confirmed that avian influenza was the cause of the death.

• Teams of rapid response force, comprising personnel of the Animal Husbandry and Health Departments started culling of thousands of ducks. nearly 2.60 lakh ducks have been culled within one week after the outbreak of H5N1 virus in Kottayam, Alappuzha and Pathanamthitta districts of Kerala. the state government announced a compensation of Rs.100 for birds that are less than two months old and Rs. 200 for those older than two months.

Avian Influenza Virus outbreak in Kerala November 2014

Mad cow disease outbreak in UK 1980

HYGIENE AND CONTROL OF THE ENVIRONMENT

• 1st public health measure to be applied on a population example. protecting the public water supply

• Implementation of farm hygienic practice improves sanitary environment of animals

• Sanitary control of animal slaughter• (Critical supervision of animal slaughter provides excellent

opportunities for early detection of livestock diseases in the area)

HYGIENE

• Sanitary controls in slaughter house

• Proper ventilation, Clean water in farms , Pest control , Improvement of housing , General cleanliness

• Rotational grazing of the pasture

• Proper disposal of dead animals

MASS IMMUNIZATION

• Immunization reduces number of susceptible animals in the population, augments herd immunity

• An immunization programme must be1) Epidemiologically relevant2) Immunologically effective3) Operationally feasible4) Socially acceptable

VACCINATION

• Can be different types.

-Strategic vaccination- to prevent the

incursion of diseases from an endemic area.

-Emergency vaccination-at the time of an epidemic.

-Ring vaccination- around an infected area at

the time of an outbreak.-FMD vaccination

IMPORTANCE OF VACCINATION

http://www.mpdah.gov.in/PDF/VaccinationSchedule(Madhya Pradesh department of animal husbandry)

• Aerosol vaccination were tried experimentally against Tularemia and Anthrax

• Oral vaccination/ Bait vaccination against Rabies

NICHE FILLING

• The presence of one organism within a niche can prevent its occupation by another organism.

• This is epidemiological interference-investigated, experimentally in the poultry industry - Suspensions of endogenous intestinal microbes fed to one-day-old chicks prevent colonization of their digestive tract by virulent salmonella spp., Campylobactor jejuni and E.Coli.

• This technique of control has the advantage over prophylactic antibiotic chemotherapy that antibiotic resistance is not encouraged.

CONTROL OF VECTORS

• Biological vectors: infectious diseases transmitted by biological vectors can be controlled removing the vectors. insect vectors can be killed with insecticides.

• Control of mechanical vectors: living organisms that mechanically transmit infectious agents can be controlled by destruction and disinfection.

EXAMPLES• Equine encephalomyelitis (destruction of mosquito larvae

and breeding places, use of protective screens in dwellings)

• Leishmaniosis (control of sand flies and reduction of contact with humans)

METHODS OF VECTOR CONTROL

a) Environmental measures• source reduction

• Drainage operations

• Planned water management

• Proper disposal of wastes

B) Chemical measures• Contact poisons: 1) Natural: pyrethrum, derris, mineral oil2) Synthetic: a) organochlorines – DDT, Lindane

b) organophosphates - Dichlorvos, Carbamates• Stomach poison: Paris green, Sodium fluoride• Fumigants: Hydrogen cyanide, Methyl bromide

Pyrethrum

BIOLOGICAL CONTROL

• 1) Fishes: : Gambusia affinis , Aplochilus panchax , Paecelia holbrooki effective predators of anopheline

• 2) Fungi: Goelomomyces

• 3) Protozoa: Nosema algerae

• 4) Bacteria: Bacillus thuringiensis, Bacillus sphaericus

• 5) Genetic manipulation of insect vectors

RESERVOIR CONTROL

• Reservoir control is applicable when a population of expendable wild animals act as reservoirs for an infection

• Helpful against rats, stray dogs, other noxious reservoir hosts for leptospirosis, rabies, plague, typhus etc.

• Wild animals - Poison baiting and Trapping is widely used• Isolation and treatment - Domestic animals• Rodenticides and Fumigation

Reservoir is defined as any person animal or non living thing in which infectious agent lives and multiplies and can be transmitted to a susceptible host (Elements of Public Health pg. 460)

EARLY DIAGNOSIS

• To assess the presence of a disease and to establish the pathogen(s) involved

• Brucellosis : Agglutination /CFT (Complement fixation test)• Glanders: Mallein test• leptospirosis: MAT (Microscopic agglutination test)• Rabies: FAT (Fluorescent Agglutination test)• Tuberculosis: Tuberculin Test• Newcastle Disease: HI• Swine Influenza: Complement Fixation test (CFT)

Tuberculin Test

Fluorescent Agglutination test

GENETIC IMPROVEMENTS

• Incidences of some infectious disease can be reduce by Selective breeding.

Eg: Breeds of cattle in Tse Tse zones of Africa N’Dama breed tolerant for Trypanosomosis

FMD and TB in Ongole and HF cattle

N’DamaOngole

HEALTH EDUCATION• Health education is a most effective preventive devices

not only in man but also in diseases of lower animals where educating the owner is of paramount importance.

• Educating the community about the cause and mode of diseases transmission prevention and treatment of diseases.

• Education helps create cooperation and participation of the public in fulfilling the goals of Diseases management.

EPIDEMIOLOGICAL DIAGNOSIS

• The frequency and patterns of diseases occurrence are quantified with possible determinants

• Epidemiological intelligence and Epidemiological analysis are used

• Determines immediate and long term needs for purposeful action against the disease.

• It helps in developing appropriate approaches against emerging infectious diseases

EPIDEMIOLOGICAL SURVEILLANCE

• Main tool of Epidemiological diagnosis

• Helps in identifying priorities for long term action against a disease and keeping the field level personnel informed

• Facilitate rational setting of appropriate disease management actions

www.fao.orgFigure 1: The epidemiological triad (Snieszko, 1974)

www.fao.orgFigure 2: Factors influencing veterinary diagnoses (from Pfeiffer, 1998)

PREVENTION OF ZOONOTIC DISEASES IN HUMAN

POPULATION• High risk group population must be protected from

occupational zoonotic diseases.• Examples: Anthrax, Leptospirosis.

• It can be achieved through following measures• Health education• Personal hygiene• Protective clothing• Immunization• Regular testing• Reducing the contact potential

CONTD…• Improving social customs, norms, condition of life style.• Early diagnosis, isolation and therapy• Keeping the environment hygiene• Regular ante mortem inspection animals at slaughter

houses following consumer protection strategies (HACCP - hazard analysis critical control point).

• Coordination between Medical, Veterinary and public health personnel.

• Notification and reporting disease and outbreaks.• Disinfection and sanitation.• Public health awareness.

www.indiasanitationportal.org

riceinstitute.org

FACTORS INOLVED IN DISEASE CONTROL AND ERADICAITON

PROGRAMME• Veterinary Infrastructure• Diagnostic Feasibility• Adequate Surveillance• Availability of Replacement Stock• Producers opinion And Co-operation• Public opinion• Public Health Considerations• Requirements For Legislation And Compensation• Ecological Consequences• Financial Support

VETERINARY INFRASTRUCTURE

• Three Main Components

- Mobile Field Service comprising of adequately trained Veterinarians and Veterinary auxiliaries.

- Adequate Diagnostic facilities.

- Adequate Research Facilities

DIAGNOSTIC FEASIBILITY

• Disease should be promptly recognized

- Clinical signs.

- Pathological changes.

- Isolation of causative agents.

- Demonstration of immune, allergic or biochemical response.

- Epidemiological identification of changes of a variable in a population.

ADEQUATE SURVEILLANCE

• Three components

Data collection- from field, clinics, slaughter houses etc.

Processing & analysis - local/state level & national level.

Prompt feed back - to programme planners and implementers.

PRODUCER’S AND PUBLIC OPINION

• Producer’s co-operation depends on their understanding of campaign- preliminary step- detailed explanation of the rationale of the programme.

• Public – mass slaughter of animals may not be possible in many countries.

PUBLIC HEALTH CONSIDERATION

• Control of zoonotic disease is an important concern. Public health significance is an important factor if disease can be fatal or clinically severe. Eg- Rabies, Leptospirosis.

• In livestock- mainly due to financial consideration, reduction of human incidence is an added advantage.

CONTD…

• Legislation & compensation: programmes will be more effective with supporting legislation. Eg.- Australia- without quarantine no entry for animals from countries having rabies.

• Availability of replacement stock: if slaughter is involved sufficient replacement stock should be available to reduce disruption to production, not a very critical concern.

CONTD…

• Ecological consequences: eradication of agent may affect the balance of nature. Only theoretical concern.

• The elimination of an infectious may free a niche that could be occupied by more virulent organism.

• Financial support: government need to support diagnosis, vaccination, quarantine, veterinary services

• Before starting an eradication programme agency must ensure that-

- All technical resources are available including man power.

- Agricultural community supports the policy.

- State borders can be adequately policed.

- Adequate diagnostic & other tools are available.

• Should only begin when success is reasonably certain.

GENERAL OBJECTIVES OF ZOONOSES CONTROL

OPERATIONAL PHASE IN ZOONOSES CONTROL

• SURVEILLANCE• CONTROL IN ANIMALS• CONTROL OF INFECTIVE MEDIA• PREVENTION IN MAN• STRATEGY SELECTION

ESTABLISHMENT OF SURVEILLANCE

• Establishment of diagnostic services1. Clinical pathological diagnosis2. Laboratory testing

• Establishment of epidemiological intelligence service

1. Data collection processing and analysis2. Prompt feed back to implementing officers

CONTD…

• Data collected froma. Diagnostic labsb. Slaughterhousesc. Clinical facilitiesd. Insurance schemese. Field vets.

CONTD…• Slaughter house data has greater potential for

epidemiological research on diseases and for control programme design, monitoring & evaluation

• ( Elements of Public Health. page 466)

CONTROL IN ANIMALS

• Quarantine Test and destruction (Brucellosis, Glanders , Leishmaniosis, salmonellosis of poultry,

rabies, bovine tuberculosis)

• Test and segregation Leptospirosis, FMD

• Immunization Brucellosis, Equine encephalomyelitis, Leptospirosis , Rabies,

Rift valley fever, ND in poultry

CONTD..

• Treatment Echinococcosis (deworming of dogs and destruction of

the excreta), Leishmaniosis, Leptospirosis,

Restriction of animal movements and population• Equine Encephalomyelitis, Rabies and Rift valley fever

CONTD….

• Prohibition to slaughter of diseased animals for human consumption

• (Anthrax, Glanders, Rift valley fever, Bovine TB )

DESTRUCTION OF PATHOGENIC MATERIAL

• Brucellosis (safe disposal of aborted foetus)• Anthrax safe disposal of carcass • Echinococcosis (destruction of dog faeces and infected

viscera from secondary hosts)Disinfection of contaminated areas (brucellosis,

salmonellosis, tuberculosis)

PREVENTION IN MAN

• Public awareness

• Recommend pasteurization of milk

• Use safe milk and meat products

• Proper disposal of suspected material

• Vaccination

DISEASES ERADICATED OR UNDER PROCESS OF

ERADICATION• RABIES: Lyssa virus - Difficult to control due to sylvatic cycle, Reservoirs, contact between

Urban & sylvatic cycles etc. - Globally 55000 deaths - India around 20000 deaths ( Who 2009).

PREVENTION CONTROL AND ERADICATION

• Vaccination of the pet animals• Control of stray animals and reporting of ill animals• Reduce the pet animal exposure to wild life• Spaying and neutering of stray animals to decrease the

dog population

ANTHRAX

• Bacillus anthracis

- 20000 to 100000 human cases per annum - 95- 99% cutaneous form - wide host range - spore –can survive for very long time

PREVENTION CONTROL AND ERADICATION

• Antibiotics after exposure to humans• Educating the farmers about Anthrax• Vaccinations (ring vaccinations during outbreak)• Vaccination of livestock (Spore vaccine using Sterne's strain)• Disinfection of wool, hide & skin, soil (4% formaldehyde is the

best disinfectant)

• Proper disposal of Anthrax carcass –incineration best method• Disease epidemiological surveillance and quick response• Proper handling of wild life diagnosed with anthrax

http://articles.extension.org/pages/13386/anthrax#.VkoYH7crI_4

Global surveillance on anthrax incidence is quite poor, particularly in endemic areas. The map below, produced by the World Health Organization Collaborating Center for Remote Sensing and Geographic Information Systems for Public Health, depicts the general areas of Endemicity by country across the world.

PLAGUE

• Yersinia pestis

- Many pandemic outbreaks - Wide host range & reservoirs are obstacles - India- no occurrence after 1994 - Now mainly in African countries

Xenopsylla cheopis

Buboes

PREVENTION AND CONTROL• Early diagnosis and immediate therapy• Vector control• Rodent control– Rodenticides (Red squill, Zinc phosphide)• Rat traps • Avoid contact with infected rodents & fleas• Strict isolation of sick persons• Chemotherapy with tetracycline• Immunotherapy in high risk groups• Health Education & enviornmental sanitation

BRUCELLOSIS

• Brucella spp

-In humans undulant/ Malta fever -Vaccination, test & slaughter policy -eradicated from UK, Australia -No cases from US after 2000 -National Brucellosis control programme in India- Vaccination & milk screening

PREVENTION & CONTROLVaccination• Killed vaccine- B. abortus

B. melitensis H-38• Live vaccine - B. abortus –Strain 19

Control

• Care in handling & disposal of Foetus, Placental membrane, Uterine discharges

• Wear protective clothing such as Rubber gloves , Goggles ,Face mask, Apron

• Proper pasteurization of milk and milk products

• Maintenance of hygiene at farm slaughter house• Regular screening of animals – milk ring test• Test slaughter• Environmental hygiene and personal hygiene• Animals nearing parturition transferred to separate areas

Disinfection• Installation – 5% chlorine• Instruments -- Boil 30 minutes in 2% solution of caustic

soda• Clothes -- 2% solution of chloramine• Hands -- Soaked in 1% solution of chloramine for 5

min & wash with soap & water

• Mycobacterium bovis

- Tuberculin test- to detect infected ones - Reactors are slaughtered - Reservoir like Badgers - Eradicated from Australia - Ongoing in countries like UK, USA

BOVINE TUBERCULOSIS:

 badger

PREVENTION & CONTROL

• Early diagnosis and chemotherapy• Use of masks & other protective clothing• Screening using tuberculin test• Test slaughter in case of animals• Proper pasteurization of milk & cooking of meat• BCG vaccination of all individuals• Health education & personal hygiene

Estimated tuberculosis incidence rates, 2012

Data from the World Health Organization’s tuberculosis database. Available from: www.who.int/tb/country/data/download/en/index.html

BOVINE SPONGIFORM ENCEPHALOPATHY

• In UK in 1986. -Caused massive culling & slaughter -Ban on animals & products -connection With creutzfeld Jacob disease (CJD) -Countries with negligible risk: Argentina, Iceland, Panama, Australia, India, Sweden, Colombia, new Zealand, USA, Denmark, Norway, Uruguay, Finland,

PREVENTION & CONTROL

• Compulsory slaughter and compensation• Ban on ruminant derived protein foods to ruminants• Ban on feeding of bovine offal to pigs & poultry• Milk & Meat from infected animals are banned• Surveillance systems using histopathological examination of

dead cattle• Ban on importation of animal and animal protein from

countries with disease• Avoid cattle feed with materials containing rendered

products from scrapie affected flock• Dispose off the scrapie affected sheep carcass

MASSIVE CULLING

GLANDERS

• Burkholderia mallei

-Mainly in equines, mules

-Spread by direct contact

-Eradicated from North America,

Most of Europe & Australia.

-Under eradication in countries

like Turkey.

-Endemic in Asia, Middle east

& Africa.

• Early detection • Elimination of affected animals• Complete quarantine• Disinfection of the area involved• Treatment given only in endemic areas

PREVENTION & CONTROL

DRACUNCULIASIS

• Dracunculus medinensis

Started in 1980 by CDC,

with help of carter center

& UNICEF.

-Reduced from 3.5 million cases

in 1986 to 1058 in 2011.

-India- eradicated in 2000-

national Guinea Worm

Eradication Programme,

started in 1983-84.

• Prompting health education and behavior change• Implementing vector control using larvicidal drugs• Filtering water from open water bodies before drinking• Prevent transmission from each worm by treatment,

cleaning and bandaging regularly the affected skin and until the worm is completely eliminated

• Heightening surveillance• Improving drinking water qualities

PREVENTION & CONTROL

SCHISTOSOMIASIS

• Schistosoma spp

-200 million of 74 countries affected -85% in sub-saharan africa -Control measures by carter center & world health assembly.

PREVENTION & CONTROL

• Snail control• Reducing the number of infection• Improved sanitation prevent transmission• Mass drug treatment of entire communities especially

school children• Avoid swimming in fresh water • Drink safe water

ONCHOCERCIASIS

• O. Volvulus

- Spread by simulid flies - Endemic in many African Countries - Under eradication in Latin American & African Countries

Onchocerciasis Elimination Programme: started in Central & South America in 1992 spending 124 million US Dollars since then.

• Treatment -- treatment of onchocerciasis is ivermectin (it prevents adult worms from producing more microfilaria thus reducing transmission.

• Vector control –killing the larvae of the black fly vectors using insecticides

• Mechanical traps for vector control

PREVENTION & CONTROL

Simulium damnosum flies caught in the trap

ONCHOCERCIOSIS ELIMINATION

• Programme: started in central • & south America in 1992• Spending 124 million• US dollars since then.

FOOT & MOUTH DISEASE

• : Aphtho Virus -20000 crore annual loss in India -FMDCP-central government funded -ASCAD- by state & central governments -Aim: freedom with vaccination status by 2020 -Still endemic in more than 100 countries -Eradicated from USA, Canada, Australia,

most of European countries.

Vaccination of the animals Quarantine of affected animals Hygienic methods in farm equipment's and farms to prevent the

spread of diseases. Proper hygienic methods to be taken up by the farmer and the

person milking the animal The method used by developed countries in eradication of FMD is

strict vaccination and stamping out policy of the affected animals.

PREVENTION & CONTROL

REFERENCE

• Michael thrusfield.2005.Veterinary epidemiology.(3rd ed.).Blackwell publishing, 584p.

• Park textbook of preventive and social medicine (22nd edition)• Sherikar, a.T., Bachhil, V.N., Thapliyal, D.C. 2004. Textbook of elements of

veterinary public health. ICAR, new delhi,572p.

• www.who.int• www.oie.int• www.cdc.gov• www.ncbi.nlm.nih.gov• www.cartercenter.org