Rabies

This particular presentation includes slide on basic virology about rabies virus, pathogenesis of rabies and it's management specially emphasized on guide of pre and post exposure vaccination.

1. RABIES Dr. Tarek Mahbub Khan

2. RABIES TLO: The virus Animal susceptibility Street and fixed virus Replication Pathogenesis of rabies encephalitis Clinical features of rabies Outline of lab diagnosis Prevention: Vaccines

3. Salient features of Rabies Rabies is an acute infection of the CNS Rabies is caused by rabies virus (Rabdoviridiae family) Transmission: Through saliva of infected animal Mode of transmission: Animal bites, licks on abrasion Incubation period: 4 to 8 weeks (9-90 days) Variation of incubation period: depends on site of bite Human is dead end host

4. Family : Rhabdoviridae Genus : Lyssavirus Shape : Rod or bullet shaped Nucleocapsid : Helical Genome : Single stranded RNA with negative polarity, hence posses their own RNA depended RNA polymerase. Replicates in cell cytoplasm Envelope: contains virus encoded glycoproteins The Virus

5. Diagrammatic structure of the virus

6. Antigenic properties of the virus Single serotype Antigenically different strains are prevalent in various geographical location due to: Epitopes difference in nucleoprotein Epitopes difference in surface glycoprotein

7. The virus susceptibility to environmental factors Heat: 50 C for 1 hour Ultraviolet light Inactivated by CO 2 (e.g., dry ice) Chemicals: Ether, alcohol, detergents, trypsin Extreme of pH

8. Animal susceptibility VERY HIGH HIGH MODERATE LOW Foxes, Jackals, Wolves, Cotton rats Hamster, Cat, Bats, Rabbit, Cattle Dogs, Sheep, Goats, Horse, non-human primates Opossums

9. Shunk and Raccoon

10. Hamster and Opossum

11. Street virus versus Fixed virus STREET VIRUS FIXED VIRUS Freshly isolated from the infected samples Propagated in serial passage in the rabbit brain Variable incubation period (21-60 days) Fixed incubation period (varies between 5-10 days Inclusion bodies are commonly formed Not commonly formed

12. STREET VIRUS FIXED VIRUS Wide host range Host range becomes diminished Extra-neuronal multiplication occurs Extra-neuronal multiplication does not occur Can not be used in vaccine Used in vaccine Street virus versus Fixed virus

13. Replication BINDS WITH Ach- Choline receptor RNA-RNA pol transcribe mRNA Five virion proteins Replications: RNA(-)--RNA(+)---RNA(-) Assemble and release by budding Endosomal fusion and uncoating

14. Rabies encephalitis Viral entry: Initial multiplication in the muscles and connective tissues Retrograde neuronal transmission Reach CNS: Encephalomyelitis Spread through peripheral nerves Muscles of pharynx Salivary gland Salivation Hydrophobia Pancreas, Kidney Heart, Retina and cornea

15. Pathogenesis of Rabies

16. Pathology Neuronal death and deyelination Brain edema Vascular congestion Accumulation of inflammatory cells (lymphocytes) Presence of eosinophilic, cytoplasmic inclusion body

17. Negri body & Perivascular infiltration of lymphocytes

18. Susceptibility to infection and incubation period depends on: Host factors: Age, genetic configuration, immune status, degree of laceration, site of bite Viral factors: Viral strain Amount of inoculum

19. Average incubation period : 1-3 months in human Shorter among children than adults Prodromal period(2-10 days) Anorexia, nausea, sore throat, photophobia and change in the sensation of skin at the bite site Clinical presentation

20. Acute neurological phase (2-7 days) Occurs 80% of the cases and is ‘Furious’ form Nervousness, hallucination, bizarre behavior Increase sympathetic activity: Lacrimation pupillary dilatation, salivation Hydrophobia: Due to painful spasm of throat muscles Aerophobia: breathing difficulty against blowing air Clinical presentation

21. Neurological deficit(‘dumb’): Involves spinal cord Ascending paralysis Coma Clinical presentation

22. Laboratory diagnosis SPECIMEN HUMAN: Skin biopsy from hair line Corneal and brain tissue impression CSF and blood Saliva ANIMAL : Brain biopsy of dead animal

23. Laboratory diagnosis MICROSCOPY : of skin biopsy and corneal smear Rabies antigens by IF method Negri body by giemsa stain SEROLOGY : Detects viral antibody Serum antibodies are detected by IF and Nt test Vaccination induces antibody in serum but not in CSF

24. Definitive diagnosis in brain and spinal cord STRUCTURE: Shape: Spherical and sharply demarcated Size: 2-10 µm Internal structure: Basophilic granules in eosinophilic matrix Contents: Sub-viral particles-viral nucleocapsids Laboratory diagnosis (Negri body)

25. VIRAL CULTURE and ISOLATION Infected tissue material is inoculated into the mice brain or hamster and mouse cell line Viral growth is identified by Negri body, IF Laboratory diagnosis

26. ANIMAL OBSERVATION : All suspected animals should be sacrificed to recover the virus from the brain tissue 1O days observation for otherwise apparently healthy animals Laboratory diagnosis

27. Management (Treatment) ESTABLISHED CASE Anti-Rabies serum( Immunoglobulin): high dose Anti- convulsant and sedatives Antibiotics: to prevent bacterial wound infection Parenteral nutrition

28. Management (Vaccination) PRE-EXPOSURE PROPHYLAXIS : Day 0,7,21 or 28 Booster dose may need to maintain the antibody titer of 1:5 POSTEXPOSURE PROPHYLAXIS : Day 0,3,7,14 and 28 Wound cleaning with soup and water, DO NOT STICH Anti rabies Immunoglobulin and vaccine Tetanus prophylaxis

29. CATEGORY I: Touching or feeding animals, licking of intact skin CATEGORY II: Nibbling of uncovered skin, minor scratch, abrasions without bleeding, licks on broken skin CATEGORY III: Single or multiple transdermal bites or scratches, contamination of mucous membrane with saliva, bites of bat Types of exposures

30. Management according to category CATEGORY I: No treatment is required CATEGORY II: Only vaccination is required CATEGORY III: Vaccination and Immunoglobulin are required Intramuscular administration of 1ml or 0.5 ml HDCV preferably in deltoid region or anterolateral aspect of thigh (in children)

31. Vaccine Candidate Preexposure : Rabies virus contacts: Research and laboratory workers Rabid animal contacts: Veterinarians, zoo keepers Postexposure : depends on Nature of biting animal Provocative or unprovocative bite Severity of the bite Availability of the animal

32. Types of vaccines Human diploid cell vaccine (HDCV): Virus grown in MRC-5 human diploid cell line Virus is inactivated by β - propiolactone Purified chick embryo cell vaccine(PCEC): Grows in chicken fibroblast Inactivated by β - propiolactone Duck embryo vaccine Nerve tissue vaccine: causes allergic encephalomyelitis

33. REFERENCES Jawetz , Melnick , Adelberg . Medical Microbiology . 25 th ed. Lange publication; 2010. Kenneth J.R, C. George Ray, editors. Sherris Medical Microbiology .4 th edition. McGraw-Hill, Inc; 2004. Alan L. Rothman. Current topics in Microbiology and Immunology, vol 336: Springer- Verlag Berlin Heidelberg, 2010. Nipah virus infection: WHO 33 Dr. Tarek/SSMC/2016 2/14/2018