viral zoonoses (rabies and vhfs)- 2013 (fn) [compatibility mode].pdf

7/30/2019 Viral zoonoses (Rabies and VHFs)- 2013 (FN) [Compatibility Mode].pdf

1/29

Viral ZoonosesViral Zoonoses -- Rabies andRabies andViral haemorrhagic feversViral haemorrhagic fevers

Dr F Noordeen

Department of Microbiology

Faculty of Medicine

University of Peradeniya

May 2013


2/29

Modes of transmission and the pathogenesis of viral

zoonoses including rabies in humans

Clinical features of viral zoonoses including rabies

Principles of diagnosis, management and prevention

viral zoonoses including rabies in Sri Lanka

Learning outcomes


3/29

Aim:

Make students aware pathogenesis &ake students aware pathogenesis &clinical significance of rabies virusclinical significance of rabies virus

Objectives:

1. to diagnose a clinical presentation of

rabies (History + Symptoms + Lab)

2. to prevent disease progression after anexposure (post exposure immunization)

3. to prevent/control rabies in Sri Lanka


4/29

Rabies and rabies virus Rabies - Acute viral infection resulting

in encephalomyelitis

Family - RHABDOviridae - (Bullet shaped)

Genus - LYSSAvirus - (Madness)

Genome - ssRNA

Envelope - Lipoprotein envelope Hosts - All warm blooded animals + man


5/29

EM appearanceEM appearance Rabies virusRabies virus


6/29

PathogenesisPathogenesis

Animal biteAnimal bite C N SC N S

Salivary glands +

hair bearing tissues

Sensory nerves

Centripetal spread

Neuronal axons

Centrifugal

spreadAerosol

Conjunctiv

al/

olfactory nerve

1. Virusacquisition

2. Virus acquisition


7/29

ClinicoClinico--pathological aspectspathological aspects

Incubation periodIncubation period -- 10 days to year or >

1. Quantity of virus deposited

2. Distance of bite site from head

OnsetOnset -- Insidious with 1-10 days of prodrome

malaise, fever, headache, psychological

disturbances, pain and tingling

around the bite - neurological phase


8/29

Clinical presentationClinical presentation

Furious rabies

80% patients Hyperactive to

various stimuli

Dumb rabies

20% patients Hyperactivity

is absent

Paralysis


9/29

Furious form of rabies

1. After 3/4 days

symptoms

become worse

2. Restless and

hypersensitive

to stimuli


10/29

3. Hydrophobia

4. On attempting/site of

water produces violentspasms in respiratory& swallowing actions

5. Respiratory & cardiacarrest Death

Furious form of rabies cont...


11/29

Dumb rabiesDumb rabies1. 20% patients may

present with this form

2. Hyperactivity is absent

3. Expressionless

4. Paralysis and death


12/29

Infection of brain - coma and death

Antibody response is apparent only in latterstage of the disease when virus has entered

the CNS and other tissues

Rx with antibodies X progression to C N S

Rabies is fatal unless the vaccine is given


13/29

DiagnosisDiagnosis

Clinical - History of animal bite and

neurological signs

Lab tests - to confirm diagnosis

Viral antigen in skin by FAT (AM)

Viral specific inclusion bodies (70-90%)

hippocampus of brain (PM)(Sellers stain or Mann stain)

Antibodies in serum + CSF in terminal

disease


14/29

Negri bodies in the brain section

Rabies virus antigen -IFA


15/29

Epidemiology

Spread - Zoonosis

Urban rabies - Unvaccinated dogs & catsWild rabies - Wild animals

Transmission - Animal bite or aerosols

Risk group - Veterinarians, veterinarystudents, animal handlers, wild lifeofficers, students/scientists involve inecological/zoological camping


16/29

Occurrence - Worldwide, common in Sri

Lanka, India and Latin AmericaFree in Australia and some islands

Prevention1. Vaccination of reservoirs

(pet dogs/cats)

2. Vaccination of high risk personals3. Stray dog elimination

4. Proper post exposure immunization

5. Public education programs on rabies


17/29

TreatmentTreatment

Human vaccine - human diploid cellculture vaccine - HDCV (killed by

formaldehyde or propiolactone) Post exposure treatment - prevent

disease

Immediate cleaning of wound

Vaccination with killed vaccine

Administration of human rabies Igs (ARS)

Symptoms - Death is inevitable


18/29


19/29

Rabies immunisation (HDVC)

Pre-exposure Rx

3 dose regime

Day 0, 7, 21 or 28

Route - deep

subcutaneous/IM

Post-exposure Rx

5 dose regime

Day 0, 3, 7, 14, 28

Route - deepsubcutaneous/IM


20/29

Human rabies

a. May be transmitted by the bite of cats

b. May be prevented by adequate immunization and

control of dogs

c. The best available vaccine is the human diploidcell culture vaccine

d. Specific immunoglobulin should be injected

around the bite wound as soon as possible after

the bitee. The development of hypersensitivity reactions are

major complication of the human diploid cell

culture vaccine


21/29

RNA viruses includeRNA viruses include

a. Chicken pox virus

b. Rabies virus

c. Hepatitis A virus

d. Hepatitis C virus

e. Hepatitis B virus


22/29

Viral haemorrhagic fevers (VHFs)Viral haemorrhagic fevers (VHFs)

Aetiology:A number of arboviruses (Toga

and Bunyaviruses) and some similar viruses

(Arena and Filoviruses)

Disease: Similar to the rather non-specific

flu-like illness but which rapidly progresses to

a severe disseminated illness with a markedbleeding tendency and multi-organ failure


23/29

There is usually a considerable mortality

in VHFs

The following may produce a similar

clinical picture & requires to be excluded

Meningococcal disease

Rickettsial disease

Leptospirosis

Hepatitis

Malaria

Snake bites

Tryponosomiasis


24/29

Crimean Congo Haemorrhagic Fever (CCHF)

Eastern Europe, Central and Southern Africa

Yellow fever Could be urban

Lassa fever West Africa

Ebola Africa

Marburg Central Africa

Hanta Africa and Asia


25/29

FAMILY Bunyaviridae

GENUS Hantavirus

More than 30 different hantavirus

species have been found (20 of whichare known to be pathogenic to humans)

Hantavirus infection/disease


26/29

Hantavirus diseaseHantavirus disease

1. Hemorrhagic fever with renal syndrome (HFRS)

2. Hantavirus pulmonary disease (HPS)

Deer mouse Cotton rat

Rice rat White footed mouse

Hantavirus

vectors


27/29


28/29

PreventionPrevention

Avoid contact with rodents and their habitats

Do not keep rodents as pets

Keep all food in sealed containers

Virions may be stable for 2 days on a dry surface sodisinfect areas contaminated by rodents

Disinfect using a 10% solution of household bleach

Eradication unlikely due to the large percentage ofrodents which carry these viruses


29/29

Three young men presented to Pollunnaruwa hospital with a 2 day

history of high fever with chills, intense myalgia and deteoriating

renal function. Two required ventilation due to respiratorycomplications. They all gave a history of exposure to rats during

different activities they perform in the paddy stores and

warehouses they work.

1. What 2 infective diseases may produce these clinicalfeatures and what is the route of transmission in each of the

diseases? (30 Marks)

2.How can you make an aetiological diagnosis of ONE

disease that you have identified in 2.2. (50 Marks)

3.How can you advise those who work in similar settings to

prevent exposure to infective agent responsible for the above

clinical scenario. (20 marks)

viral zoonoses (rabies and vhfs)- 2013 (fn) [compatibility mode].pdf

Documents