ZOONOSESZOONOSES

Dr.Nan Nitra ThanM.B.,B.S DTM&H M.C.T.M(Tropical medicine)

The outcome

Able to illustrate the basic concepts and terminologies used in zoonosis

Able to illustrate the epidemiological concepts relating to Rabies

Able to state the epidemiological concepts relating to Plague

Contents

Classification of zoonosis

The epidemiology of Rabies

The epidemiology of Plague

Definition

Zoonoses are diseases of vertebrate animals (WHO 1959)

Transmitted to man: either directly or indirectly through an insect vector( Arbovirus infection)

Not all arboviral diseases are zoonosis e.g. dengue and urban yellow fever

Examples of viral zoonoses that can be transmitted to man directly include rabies, hantaviruses, lassa and ebola fevers

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Zoonoses: Classification

DIRECT ZOONOSES:[one host for completion of its life cycle] Rabies, Trichinosis, Brucellosis

CYCLOZOONOSES:[at least two species of vertebrates as

definitive and intermediate hosts] Human Taeniasis, Echinococcosis

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METAZOONOSES: [Requires both a vertebrate and an invertebrate host for completion of the life cycle] Arboviral diseases, Plague, schistosomiasis

SAPHROZOONOSES: [A zoonosis whose causative agent requires both a vertebrate host and a non animal reservoir or developmental site for completion of its life cycle]Various Larva migrans and mycoses

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Zoonoses: Animal Species

Dogs & Cats

Rabies

Round worm

Ringworm

Lyme Disease (dogs only)

Cat Scratch Disease (cats only)

Food Animals

Salmonella

E. coli

Brucellosis

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Zoonoses: Animal Species

Birds:

Psittacosis

West Nile

Cryptococcus

Reptiles, Fish, & Amphibians

Salmonella

Mycobacterium

Wild Animals

Hantavirus

Plague

Tularemia

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Zoonoses: Viral Examples

Zoonoses: Bacterial Examples

Zoonoses: Parasitic Examples

Zoonoses: Mycotic Examples

AspergillosisBlastomycosisCryptococcosis

DermatophytosisHistoplasmosis

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Structure

‘bullet’ shaped , RNA structure

Caused by neurotropic viruses in the family Rhabdoviridae, genus Lyssavirus.

Regardless of the viral variant found throughout the world, all lyssa viruses cause rabies

Picture from Centers for Disease Control and Prevention

www.cdc.gov/ncidod/dvrd/rabies

G proteinM proteinEnvelope

RNP core

Distribution of important rabiesvector species

AFRICA: Domestic dog, jackals, mongoose

AMERICAS: Fox, skunk, racoon, bats, dog

ASIA: Domestic dog, wolf

EUROPE: Fox, wolf, dog, bats

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High Risk Animals

Raccoon

Skunk

Groundhog

Fox

Bat

“free-roaming” cats

Intermediate Risk Animals

Dogs

Cats – vaccinated or non-roaming

Livestock – horses, cattle, pigs

Other non-rodent wild animal species

i.e, bear, deer, coyote, etc

Low Risk Animal

Squirrels, chipmunks

Rats

Mice

Indoor small caged pet rodents

Logomorphs

Public Health importance

> 2.5 billion at risk in over 100 countries

50,000-70,000 human deaths annually

10 million people treated for exposure to rabies every

year

90% in developing countries in Tropics i.e. Africa,

Asia, South America, Oceania

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Global distribution ofmammalian reservoirs and vectors

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Mode of Transmission

1) ANIMAL CONTACT: inoculation of virus laden saliva into a wound or on a mucous membrane (BITES & LICKS)

2) Human-to-Human: very rare! (corneal grafts,transplacental infection?)

3) INHALATION: very rare! (bat-infested caves, laboratories)

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Pathogeneis

Virus binds to a nerve cell & migrates to spinal cord to brain (centripetal spread)- viral replication occurs & produces encephalitis

Viral particles travel out from brain (centrifugal spread) via nerve cells to salivary glands, where further replication occurs & secretion in saliva, rendering the person or animal to be infectious

At the time it gets to the salivary glands, this is the end stage of the disease, and death usually occurs shortly thereafter – within several days

Transmission Cycle of Rabies24

Rabies attacks the Central Nervous System

rabies virus from an exposure on the leg spreads up the spinal cord to the brain and throughout the rest of the body

Rabies virus entering the body.

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Was There An Exposure?

A bite (penetration of the skin by teeth) from a known or suspect rabid animal

Scratches, abrasions, open wounds (bleeding within 24 hrs), or mucous membranes (eyes) contaminated with saliva or other potentially infectious material from a known or suspect rabid animal

Other contact - such as petting an animal or contact with urine, feces or skunk spray - does NOT constitute an exposure

WHO Definition of Exposure

Category Type of contact Type of exposure

Recommended treatment

I Touching or feeding of animals; Licks on intact skin;

None None if reliable history is taken

II Nibbling of uncovered skinMinor scratches or abrasions without bleeding

Minor Administer vaccine immediately; Stop treatment if animal remains healthy for of 10 days or if animal is proven to be negative for rabies by a reliable laboratory using appropriate diagnostic techniques  

III Single or multiple transdermal bites or scratches, licks on broken skin; Contamination of mucous membrane with saliva (i.e. licks); Exposures to bats

Severe Administer RIG and vaccine immediately. Stop if animal remains healthy for 10 days or if animal is negative for rabies

Headache, fever, sore throat

Nervousness, confusion

Pain or tingling at the site of the bite

Hallucinations

Seeing things that are not really there ( Cowering in the corner like a caged animal)

Hydrophobia

“Fear of water" due to spasms in the throat(I throw up every time I try to eat or drink something. I can’t swallow my spit)

Paralysis

Unable to move parts of the body

Coma and death

Symptoms

Laboratory Diagnosis

Histopathology - Negri bodies are pathognomonic of rabies. Negri bodies are only present in 71% of cases

Rapid virus antigen detection -Direct Fluorescent Antibody test (DFA)

Virus cultivation - definitive means of diagnosis

Serology - circulating antibodies appear slowly in the course of infection but they are usually present by the time of onset of clinical symptoms

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Diagnosis of Rabies

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Management and Prevention

Inactivated whole virus vaccines

•Nervous Tissue Preparation e.g. Sample Vaccine - associated with the rare complication of demyelinating allergic encephalitis.

• Duck Embryo Vaccine - this vaccine strain is grown in embryonated duck eggs, (a lower risk of allergic encephalitis but is considerably less immunogenic)

•Human Diploid Cell Vaccine (HDCV) - currently the best vaccine

•Other Cell culture Vaccines - (developing countries)

Prevention

Pre- exposure prophylaxis

• Provides protection from unapparent exposures and when treatment is delayed

• persons at increased risk of being exposed to rabies e.g. vets, animal handlers, laboratory workers etc.

• spending 1 month or more in countries with endemic dog rabies and in which PEP would likely be significantly delayed to geographic distances/ lack of medical infrastructure

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Pre-exposure Vaccination Protocol

Three doses of vaccine administered on days 0, 7 and 21 or 28

Dosage: 1.0 ml administered IM in the upper deltoid

Test serum every 2 years to determine if an adequate antibody level persists

If absent, administer booster

WHO Recommended Pre-exposure(PreEP)

3-dose series intramuscular or intradermal regimen

Exposure: No Rabies immunoglobulin needed

day 0 7 21 or 28

day 0 3

WHO Recommended Post-exposure prophylaxis

1. Immediate flushing and washing of the wound with soap and water, or other detergent

If soap or detergent are not available, flush extensively with water

2. Passive immunization: Administration of Rabies immune globulin for Category III contacts/exposures

3. Active immunization: Administration of tissue culture vaccine according to one of WHO regimens

Standard intramuscular regimen. One dose into deltoid on each of days:

Essen intramuscular Regimen

WHO Recommended PEP Schedule

5 vials 5 visits

day 0 3 7 14 28

Rabies immunoglobulin

Control of Rabies

Urban - canine rabies accounts for more than 99% of all human rabies. Control measures against canine rabies include;

stray dog control

Vaccination of dogs

quarantine of imported animals

Wildlife - this is much more difficult to control than canine rabies { trials in Europe -where bait containing rabies vaccine is given to foxes}

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Plague

Introduction

Plague has a long history as a biological weapon

A bacterial disease, caused by Yersinia pestis

Primarily affects wild rodents- spread from one rodent to another by fleas-Humans bitten by an infected flea

Develop a bubonic form of plague(a bubo- a swelling of the lymph node) draining the flea bite site

IP, Bubonic plague appear 7–10 days after infection

If the bacteria reach the lungs, the patient develops pneumonia (pneumonic plague) - transmissible from person to person (coughing)

The History of Plague

Historians think that the plague arrived in England during the summer of 1348. By 1350, nearly the whole of Britain was infected with the plague

At the end of 1350 nearly two and a half million people were dead!

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Epidemiology

First Pandemic: Early Middle Ages (Plague of Justinian)

Second Pandemic: 14th (Black Death) to 19th century

Third Pandemic: 19th and 20th centuries

10 August 2010 -Plague in Peru

11 August 2009 -Plague in China

7 November 2006 - Suspected plague in the Democratic Republic of the Congo

13 October 2006/June 2006 /15 March 2005 -Plague in the Democratic Republic of the Congo

AGENTS FACTORS

Causative Agent - Yersinia pestis (Gram-ve coccobacilli, non-motile)

Virulence- cytotoxin & endotoxin

RESERVOIR: Wild rodents, gerbils, Skunks etc

In India: Tatera indica (Immune to plague)

Source of infection: Infected RODENTS FLEAS & Case of Pneumonic Plague

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BLOCKED FLEA

Blood meal (0.5 cu m)containUp to 5000 bacilli

Multiply enormously in the GUT

blocked proventriculusFood cannot pass through

Frantic Efforts to suck blood

REGURTITATES Plague Bacilli Inoculation

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BLOCKED FLEA

Blocked is an efficient transmitter of plague

Blocked flea eventually dies

A partially blocked flea may live longer and

more efficient transmitter

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HOST FACTORS

All ages & both sexes

Man may contact with natural ‘foci’ while Hunting, grazing, cultivation & harvesting

Movement of people and Cargo by sea or land

No natural immunity

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ENVIRONMENTAL FACTORS

Season: from September to May

Temperature: 20-25 C Humidity 60%,

POOR HOUSING conditions & abundance of Rats and rat

fleas

VECTORS: Xenopsilla cheopis - Rat Flea, Others X. astia,

X. braziliensis ,Pulex Irritans—Human Flea

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Disease Progression in Human

Incubation period:

Bubonic and septicemia 2-7 days

Pneumonic- 2-3 days

BUBONIC PLAGUE: sudden fever, chills, headache, prostration,

painful buboes

PNEUMONIC PLAGUE: complication of bubonic-septicemic

plague

SEPTICEMIC PLAGUE: Rare, lab infection

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Bubonic plague

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Laboratory Criteria for Diagnosis

1. Presumptive

• Elevated serum antibody titer(s) to Yersinia pestis fraction 1 (F1) antigen or

• Detection of F1 antigen in a clinical specimen by immunofluorescent assay

2. Confirmatory

• Isolation of Y. pestis from a clinical specimen {Yersinia pestis… Non spore forming , G (-) ,non motile coccus bacillus ( exhibit bipolar staining- characteristic safety pin appearance)} or

• Fourfold or greater change in serum antibody titer to Y. pestis F1 antigen

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Treatment

If diagnosed early, bubonic plague can be successfully treated with antibiotics

Pneumonic plague ( most deadly infectious diseases)-patients can die 24 hours after infection

The mortality rate depends on how soon treatment is started, but is always very high.

Prevention & Control

Isolate infected animals

Limit number of people in contact

Personal protection

Surgical mask, gloves, eye protection

Flea control

Dogs and cats (Use flea control products for the pets)

Spring to fall

Commercial Premise for rat control

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Prevent roaming or hunting of pets

( Cats & dogs should not be allow to roam freely or hunt-

outdoor cats are at risk)

Rodent control

Eliminate rodent habitat around home [Brush, food sources, firewood, junk]

Undertaken only after insecticide use

Insect repellents for skin & clothes for flea

bites [DEET to skin and permethrin on clothes]

Insecticide use in epizootic areas

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Public health education

Prophylactic antibiotics [ tetra or sulfonamides

2-3wks]

Plague outbreak/flea bites

Handled infected animal

Close contact with plague case

Vaccine Live and killed developed/No longer available in the U.S.

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Prevention and Awareness

Report suspected animal cases

State health department

State veterinarian

Education of clients and public

Risks, transmission, prevention

Take precautions in enzootic and epizootic areas

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MANAGING SPECIAL SITUATIONS

Bioterrorist Event

• Yersinia pestis has been classified as a "category A" agent for bioterrorism

• easily disseminated by aerosol, can be transmitted from person to person (pneumonic plague)

• capacity to cause severe illness and death

• An intentional release (bioterrorist event) should be suspected if unusual clusters of pneumonia are seen in otherwise healthy individuals or in people in buildings with common ventilation systems

• In the setting of a biological attack, antibiotic prophylaxis may be recommended for those with a suspected or known exposure to Y. pestis, as determined by public health officials

Conclusion

• Rabies

• Plague

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THE END

THANK YOU FOR YOUR ATTENTION