1. Dr Ubaid N P Community Medicine Dept ACME, Pariyaram

2. Zoonoses
Definition - “those diseases and infections which are naturally transmitted between vertebrate animals and man”
Anthropo-zoonoses – infections transmitted to man from lower vertebrate animals
Zoo-anthroponoses - infections transmitted from man to lower vertebrate animals
Amphixenoses – infections maintained in both man and lower vertebrate animals that may be transmitted in either direction

3. Classification based on the type of life cycle of the infecting organism
Direct zoonoses: Transmitted from infected vertebrate host to a susceptible host by direct contact, fomites or by a mechanical vector. Undergoes little or no propogative or development changes during transmission. Eg – Rabies, trichinosis, Brucellosis
Cyclo zoonoses: Require more than one vertebrate host species to complete the developmental cycle; no invertebrate host. Eg – Echinococcosis, human taeniases
Meta zoonoses: Transmitted biologically by invertebrate vectors; multiplies or develops or do both in vectors. There is always an extrinsic incubation period before transmission to another vertebrate host. Eg – Arbovirus infection, Plague, Schistosomiasis
Sapro zoonoses: Have both a vertebrate host & a non animal developmental site or reservoir like, food, soil, plants. Eg – Larva migrants, some mycoses

4. Yellow Fever

6. Introduction Zoonotic disease caused by an arbovirus
Spectrum of disease varies from clinically indeterminate to severe cases
Severe cases develop jaundice with hemorrhagic manifestations, albuminuria/ anuria, shock, stupor and coma
Can have severe hepatic and renal involvement
Death occurs between 5th and 10th day of illness
Case fatality rate may reach 80% in severe cases
45 countries in Africa & Latin America has reported cases, with at risk population of 900 million
No case has been reported in Asia, although the region is at risk as the conditions required for transmission are present there

8. Epidemiological determinants Agent factors
Flavivirus fibricus; group B arbovirus; Togavirus family
Reservoir of infection
In forest: monkeys & forest mosquitoes;
In urban areas: Man & Aede aegypti mosquitoes
Period of communicability
Man: first 3 to4 days of illness;
Mosquitoes: After an extrinsic incubation period of 8 to 12 days, mosquitoes becomes infective for life

9. Host factors Age & sex – All ages and sexes
Occupation – person who has contact with forests (wood cutters, hunters)
Immunity – one attack gives life long immunity; Infants born to immune mothers have antibodies up to 6 months of life

10. Environmental factors
Climate – temp. of 24°C or over and relative humidity of over 60% is required for multiplication of virus and for the mosquitoes to live long respectively
Social factors – Urbanization, dense population, increases in number of people who travel from endemic to receptive areas

11. Modes of transmission
Sylvatic(forest) YF Intermediate YF Urban YF

13. Incubation period - 3 to 6 days
Treatment:
No specific treatment
Supportive care to treat dehydration and fever
Antibiotics for secondary bacterial infections

14. Control of YF Jungle YF – continues to be uncontrollable Urban YF
Vaccination
17D live attenuated
Sensitivity
Dose & Route of administration
Contra indications and ADRs
Vaccine interaction
Vector control
Surveillance
Aedes aegypti index <1%

16. International measures
Missing link of YF in receptive countries
International Health Regulations(IHR) to restrict the spread of YF
Travellers
Mosquitoes
International certificate of vaccination
Reference centres
National Institute of Virology, Pune
Central Research Institute, Kasauli

17. Thank You