Rabies
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Rabies is a fatal viral disease spread to humans through animal bites, especially from rabid dogs. It causes acute encephalitis and is almost always fatal once symptoms start. Mass dog vaccination programs can eliminate rabies transmission by vaccinating at least 70% of dogs. In Bangladesh, efforts are underway to reduce rabies deaths by 90% by 2015 and eliminate the disease by 2020 through dog vaccination campaigns and ensuring bite victims receive post-exposure prophylaxis.
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Rabies
- 6. Man’s bestMan’s best unvaccinatedunvaccinated friendfriend
- 9. World Rabies Day (Sept. 28)World Rabies Day (Sept. 28) …… to reduce theto reduce the suffering fromsuffering from rabiesrabies
- 11. At the end of session you will learnAt the end of session you will learn • Rabies:Rabies: an invariably fatalan invariably fatal encephalitisencephalitis • Only mammals affected. Always endemic in the wildOnly mammals affected. Always endemic in the wild • 1111thth killer IDkiller ID • Wound Rx and ARV ± ARIg are main Px measureWound Rx and ARV ± ARIg are main Px measure • VirusVirus descendsdescends from brain tofrom brain to salivary glandssalivary glands • 90% from rabid domestic dog bite.90% from rabid domestic dog bite. Bats spread by aerosolBats spread by aerosol • Elimination is feasibleElimination is feasible by vaccinating dogsby vaccinating dogs • BangladeshBangladesh 22ndnd in mortalityin mortality 100% preventable100% preventable ARVL: anti-rabies vx. ARIg: AR ImmunoglobulinARVL: anti-rabies vx. ARIg: AR Immunoglobulin
- 13. KEY FACTS: RABIESKEY FACTS: RABIES • Globally >60k deaths/yGlobally >60k deaths/y (150 countries)(150 countries) • Almost always fatal once symptomaticAlmost always fatal once symptomatic • 95% deaths in Asia Africa.95% deaths in Asia Africa. India: (~30,000)India: (~30,000) • 40% children <15y40% children <15y • >15million worldwide get a post-bite vax./y>15million worldwide get a post-bite vax./y • Bangladesh: mBangladesh: most people are unprotectedost people are unprotected • Rabies costs the world $124 billion/yRabies costs the world $124 billion/y • Mass dog vaccination breaks the transmissionMass dog vaccination breaks the transmission
- 16. • R. is an imp. PH problem and is the top zoonotic d.R. is an imp. PH problem and is the top zoonotic d. • >2k deaths in2010; now <1k in 2013>2k deaths in2010; now <1k in 2013 • Control centre, at IDH: Rx 400 dog bites/d. Still, many bitesControl centre, at IDH: Rx 400 dog bites/d. Still, many bites remains untreated.remains untreated. 2 targets:2 targets: reducing deaths by 90%/2015 and eliminating R./2020reducing deaths by 90%/2015 and eliminating R./2020 • Dog is the main transmitter (95%); others: cats and jackalsDog is the main transmitter (95%); others: cats and jackals Mass canine vax. program is running to stop transmission.Mass canine vax. program is running to stop transmission. This can be achieved with 3 rounds vax. of 70% dogsThis can be achieved with 3 rounds vax. of 70% dogs Bangladesh ScenarioBangladesh Scenario
- 17. Good News for BangladeshGood News for Bangladesh • WHOWHO pilot project in Cox's Bazaarpilot project in Cox's Bazaar is a success. GoB is nowis a success. GoB is now vaccinating dogs in all 64 districtsvaccinating dogs in all 64 districts • Dog killers are now friendly dog catchers! >1k dogDog killers are now friendly dog catchers! >1k dog catchers now focus on vax.catchers now focus on vax. • Despite progress in this, fund remains a major challengeDespite progress in this, fund remains a major challenge • Dog-bite victims can get free ARV, in all 64 districtsDog-bite victims can get free ARV, in all 64 districts • Dog vax. costs, US $3/dog (total 1.2 million)Dog vax. costs, US $3/dog (total 1.2 million) GoB: govt. of Bangladesh. ARV: anti-rabies vax. Vax.: vaccineGoB: govt. of Bangladesh. ARV: anti-rabies vax. Vax.: vaccine
- 18. What is Rabies?What is Rabies? .. a zoonosis c/by.. a zoonosis c/by rabiesrabies virusvirus • Infects both domestic and wild animalsInfects both domestic and wild animals • Causes ac. encephalitisCauses ac. encephalitis Symptomatic rabies:Symptomatic rabies: 100% fatal100% fatal
- 19. Rhabdo/lyssa virusesRhabdo/lyssa viruses • Bullet shaped.Bullet shaped. RNARNA • EnvelopedEnveloped • Killed by ethanol ether,Killed by ethanol ether, iodine, soap/detergents,iodine, soap/detergents, chloroform, acetone,chloroform, acetone, heat (60heat (6000 c x5 min)c x5 min) Lyssa means rageLyssa means rage
- 20. Fixed and Street VirusFixed and Street Virus • Fixed virusFixed virus (lab virus)(lab virus):: Rabies virus after serial passageRabies virus after serial passage through rabbits to stabilize its virulence and IPthrough rabbits to stabilize its virulence and IP • Street virus:Street virus: wild viruswild virus IP: incubation periodIP: incubation period
- 21. EpidemiologyEpidemiology • R. is present on all continents except AntarcticaR. is present on all continents except Antarctica • Endemic in countries except Australia, Malaysia, Japan,Endemic in countries except Australia, Malaysia, Japan, Bhutan, NepalBhutan, Nepal • Primary reservoirs: wild mammalsPrimary reservoirs: wild mammals • Only mammals affected;Only mammals affected; except mice !except mice ! • A neglected d. of poor remote rural people; deaths rarelyA neglected d. of poor remote rural people; deaths rarely reported; vax and Ig are NA/affordable or accessiblereported; vax and Ig are NA/affordable or accessible • Common:Common: man, dogs, raccoons, skunks, foxes, bats, cattleman, dogs, raccoons, skunks, foxes, bats, cattle Ig: immunoglobulin. NA: not availableIg: immunoglobulin. NA: not available
- 23. Distribution of rabies reservoirsDistribution of rabies reservoirs
- 24. RaccoonsRaccoons
- 25. Skunks; a major reservoir of rabies in USASkunks; a major reservoir of rabies in USA
- 27. WHOWHO
- 28. • Bites, abrasionsBites, abrasions • ScratchesScratches • AAerosol (bats)erosol (bats) • Mucosal exposureMucosal exposure RarelyRarely • eating infected meateating infected meat • corneal transplantationcorneal transplantation TransmissionTransmission
- 29. PathogenesisPathogenesis • IP: 9-90dIP: 9-90d (several years):(several years): depends on:depends on: • inoculum, siteinoculum, site • wound severity, innervationwound severity, innervation • Untreated:Untreated: 50% rabid bites will develop R:50% rabid bites will develop R: • virulence, dosevirulence, dose • route, site, age, host defenseroute, site, age, host defense
- 30. Pathogenesis ..Pathogenesis .. • Commonly RV replicates in muscles: enters nerves andCommonly RV replicates in muscles: enters nerves and ascends to CNS (ascends to CNS (3 mm/h)3 mm/h) • Spread within CNS is rapidSpread within CNS is rapid • Then spreads centrifugally by nerves to salivary g., eyes,Then spreads centrifugally by nerves to salivary g., eyes, kidneys, breastskidneys, breasts • This time the classic CF developThis time the classic CF develop RV: rabies virusRV: rabies virus
- 31. Pathogenesis ..Pathogenesis .. Live virusLive virus skin: mucosa: muscleskin: mucosa: muscle Peripheral nervePeripheral nerve CNS (gray matter)CNS (gray matter) Salivary, eyes, breast, kidneysSalivary, eyes, breast, kidneys moves centripetally moves centrifugally
- 32. HistopathologyHistopathology • EncephalomyelitisEncephalomyelitis • Perivascular inflammatory cellsPerivascular inflammatory cells • NeuronalNeuronal cytoplasmic inclusioncytoplasmic inclusion (Negri bodies) esp. in(Negri bodies) esp. in pyramidal cellspyramidal cells
- 34. Early CF: (often vague)Early CF: (often vague) • Flu-like:Flu-like: malaise, LGF, chills, HA, fmalaise, LGF, chills, HA, fatigue, poor sleepatigue, poor sleep • Anorexia, anxiety, irritability, sore throatAnorexia, anxiety, irritability, sore throat • Discomfort/ paresthesiaDiscomfort/ paresthesia at bite site (50%)at bite site (50%) • BBizarre behaviorizarre behavior On progression:On progression: neuro-symptoms:neuro-symptoms:
- 35. Neuro-symptomsNeuro-symptoms BBroadlyroadly • Furious rabies (80%)Furious rabies (80%) • Dumb/paralytic R (GBS)Dumb/paralytic R (GBS)
- 36. Furious rabiesFurious rabies • Anxiety, delirium, insomnia, nervousness, seizure,Anxiety, delirium, insomnia, nervousness, seizure, aggressivenessaggressiveness, hallucinations,, hallucinations, fear of deathfear of death • BitingBiting, delusions, HGF, hyperhydrosis, goose skin, priopism,, delusions, HGF, hyperhydrosis, goose skin, priopism, hypersalivationhypersalivation, dysphagia, hydrophobia (50%), aero-, photo-, dysphagia, hydrophobia (50%), aero-, photo- • Coma and death in a few daysComa and death in a few days
- 38. Dumb/paralytic rabiesDumb/paralytic rabies • S/of partial/full paralysisS/of partial/full paralysis usually begins in the limbs andusually begins in the limbs and spreads all overspreads all over • Hydrophobia isHydrophobia is unusualunusual • Progress to coma and death (heart or lung failure)Progress to coma and death (heart or lung failure)
- 39. 3 dogs with classic dumb/3 dogs with classic dumb/ paralytic R: depression, self-paralytic R: depression, self- imposed isolation; cranial-nerveimposed isolation; cranial-nerve deficits and hypersalivationdeficits and hypersalivation
- 40. Routine rabies tests:Routine rabies tests: • Direct fluorescent antibody test (dFA): only post mortem.Direct fluorescent antibody test (dFA): only post mortem. Ideal tissue is nerve (brain). Fl. anti-R Ab incubated withIdeal tissue is nerve (brain). Fl. anti-R Ab incubated with brain fixes RV; seen by Fl. MC. Unbound Ab washed awaybrain fixes RV; seen by Fl. MC. Unbound Ab washed away • Histopathology:Histopathology: NegriNegri b. Immunohistochemistry. EMb. Immunohistochemistry. EM Importance:Importance: • For timely PEPFor timely PEP • Save a pt. from unnecessary physical and psycho. traumaSave a pt. from unnecessary physical and psycho. trauma if the animal is not rabidif the animal is not rabid Diagnosis in AnimalsDiagnosis in Animals
- 41. IHCIHC • Like dFA, IHC uses sp. Ab to detect RV inclusions in tissues.Like dFA, IHC uses sp. Ab to detect RV inclusions in tissues. More sensitive than histopathologyMore sensitive than histopathology Fl: fluorescence. MC: microscopeFl: fluorescence. MC: microscope
- 42. DFA negativeDFA negative DFA positiveDFA positive
- 43. • Negri bodiesNegri bodies are pathognomonic:are pathognomonic: only in 20%only in 20%
- 44. Rabies Dx in HumansRabies Dx in Humans • No test available before cl. diseaseNo test available before cl. disease • Confirmed pre- and post mortem by detecting RV, viral Ag inConfirmed pre- and post mortem by detecting RV, viral Ag in brain, skin, urine, salivabrain, skin, urine, saliva • Saliva is tested by reverse transcription followed by PCR (RT-Saliva is tested by reverse transcription followed by PCR (RT- PCR)PCR) • Antibody: serum, CSFAntibody: serum, CSF Ag: antigenAg: antigen
- 45. PreventionPrevention • Vaccinating dogsVaccinating dogs • Vax. for at risk personsVax. for at risk persons • Cost of PEP can be catastrophic for poor: income is $ 2/dCost of PEP can be catastrophic for poor: income is $ 2/d • No contact with stray/wild animalsNo contact with stray/wild animals • Not touching animal carcassesNot touching animal carcasses • Don’t capture or provoke stray animalsDon’t capture or provoke stray animals • Secure garbageSecure garbage • Cover chimneys and other entrancesCover chimneys and other entrances
- 46. Treat the biteTreat the bite If bitten by bats, skunks, foxes, other carnivoresIf bitten by bats, skunks, foxes, other carnivores • regard as rabid unless the area is R free or until animalregard as rabid unless the area is R free or until animal is negative by lab testingis negative by lab testing • immediate immunization and HRIGimmediate immunization and HRIG •Bites by squirrels, gerbils, hamsters, G. pigs, rats, mice,Bites by squirrels, gerbils, hamsters, G. pigs, rats, mice, other rodents, almost never require anti-R Rxother rodents, almost never require anti-R Rx HRIG: human rabies immunoglobulinHRIG: human rabies immunoglobulin PreventionPrevention
- 48. VaccinationVaccination Killed R virus vaccine PreexposurePreexposure PostexposurePostexposure Animal vaccinationAnimal vaccination 15million vaccines are pushed worldwide15million vaccines are pushed worldwide
- 49. Who should get the vaccine?Who should get the vaccine? Pre-exposure (PrEP)Pre-exposure (PrEP) • High-risk people:High-risk people: vets., animal handlers, R lab. workers,vets., animal handlers, R lab. workers, spelunkers (cave explorer), forestry workers, wildspelunkers (cave explorer), forestry workers, wild explorers,explorers, travelers in endemic areastravelers in endemic areas • Also for:Also for: people having frequent contact with RV, travelerspeople having frequent contact with RV, travelers to endemic areasto endemic areas • 3 doses: 0-7-21/283 doses: 0-7-21/28thth dd
- 50. Benefits of pre-exposure VaxBenefits of pre-exposure Vax • No need of HRIGNo need of HRIG • Less post-expo. vax. dosesLess post-expo. vax. doses • Post exposure Rx might be delayedPost exposure Rx might be delayed • Protects from inapparent exposures to RProtects from inapparent exposures to R • For repeated exposure screen for boosterFor repeated exposure screen for booster
- 51. Post-exposurePost-exposure • bitten by an animal, or contactbitten by an animal, or contact • 4 doses: 0-3-7-144 doses: 0-3-7-14thth daysdays • They should also get HRIG with first dose vax.They should also get HRIG with first dose vax. • Pre-vaccinated person get 2 doses: 0-3Pre-vaccinated person get 2 doses: 0-3rdrd d; no HRIGd; no HRIG • Should the animal be kept for 10 d?Should the animal be kept for 10 d?
- 53. Cell culture VaccinesCell culture Vaccines Human diploid cell vaccine (HDCV)Human diploid cell vaccine (HDCV) Purified chick embryo cell vaccine (PCEC)Purified chick embryo cell vaccine (PCEC) Purified Vero cell vaccine (PVRV)Purified Vero cell vaccine (PVRV) Purified duck embryo vaccine (PDEV)Purified duck embryo vaccine (PDEV) Vaccines in BD:Vaccines in BD: Rabipur (PCEC)Rabipur (PCEC) Verorab (PVRB)Verorab (PVRB)
- 54. Future Rabies VaccinesFuture Rabies Vaccines • Vaccines under development may be safe, potent andVaccines under development may be safe, potent and cheapercheaper • DNA vaccinesDNA vaccines, recombinant vaccines, recombinant vaccines • Plant biotechnology for making AgPlant biotechnology for making Ag • Neutralizing monoclonal antibodyNeutralizing monoclonal antibody
- 55. Adverse ReactionsAdverse Reactions • Less in childrenLess in children • Adults: local reactions (25%), systemic- (20%)Adults: local reactions (25%), systemic- (20%) • HA, nausea, AP, aches and dizziness (5-40%)HA, nausea, AP, aches and dizziness (5-40%) • Very rare:Very rare: illness like GBSillness like GBS • Immune-complex with boosters: hives, arthralgia, F (6%)Immune-complex with boosters: hives, arthralgia, F (6%) • Different brands differDifferent brands differ • Anaphylaxis, if any, occurs within a min- to an hr. withAnaphylaxis, if any, occurs within a min- to an hr. with dyspnoea, hoarseness, wheeze, throat swelling, hives,dyspnoea, hoarseness, wheeze, throat swelling, hives, pallor, weakness, tachycardia, or dizzinesspallor, weakness, tachycardia, or dizziness
- 56. Human Rabies IG (HRIG)Human Rabies IG (HRIG) • Category iii bite: 20iu/kgCategory iii bite: 20iu/kg with vax. but different siteswith vax. but different sites • ½ at the site (infiltrate the½ at the site (infiltrate the wound); ½ IMwound); ½ IM
- 57. Basic Care in Animal BitesBasic Care in Animal Bites • Immediate thorough toileting x15min with soapImmediate thorough toileting x15min with soap water, detergent, povidone iodine.water, detergent, povidone iodine. Don't suture!Don't suture! • Categorize the bite:Categorize the bite: • Post- exposure prophylaxisPost- exposure prophylaxis
- 59. CategoryCategory -- WHOWHO • Category I: 1.Category I: 1. touching/feeding suspect animalstouching/feeding suspect animals 2.2. licks on intact skinlicks on intact skin • Category II: 1.Category II: 1. nibbling of skinnibbling of skin 2.2. scratches/abrasionsscratches/abrasions, but no hge., but no hge. 3.3. licks on broken skinlicks on broken skin • Category III:Category III: 1 or more1 or more bites/scratches, licks with hge.;bites/scratches, licks with hge.; contamination of m. membrane with saliva, contactscontamination of m. membrane with saliva, contacts with batswith bats
- 60. Category ICategory I no treatmentno treatment Category IICategory II wound disinfection, vaccine onlywound disinfection, vaccine only
- 61. Category IIICategory III wound cleansing, HRIG and vaccinewound cleansing, HRIG and vaccine • Animal observation in our country is not practical: frequentAnimal observation in our country is not practical: frequent bitesbites • Delay Rx only ifDelay Rx only if • Species unlikely to be infectedSpecies unlikely to be infected • Lab Dx in 48hrLab Dx in 48hr • Dog >1yr old with current vaccination (observe forDog >1yr old with current vaccination (observe for 10d)10d)
- 62. Category III bite:Category III bite: bites withbites with bleedingbleeding
- 65. • To date only 6 cases survivedTo date only 6 cases survived • Once clinical, rabies is always fatal, Rx is only supportiveOnce clinical, rabies is always fatal, Rx is only supportive • Rabies typically ends after 2-10 d (6d)Rabies typically ends after 2-10 d (6d) No danger of nursing R pts with precautionsNo danger of nursing R pts with precautions PrognosisPrognosis
- 66. DDDD Other encephalitisOther encephalitis Hysteria reaction to animal biteHysteria reaction to animal bite GBSGBS PoliomyelitisPoliomyelitis Allergic encephalomyelitis ( rabies vaccine )Allergic encephalomyelitis ( rabies vaccine )
- 67. MCQMCQ • Most rabies are from bite by rabid dogsMost rabies are from bite by rabid dogs • Most of rabid-dog bites develop into rabiesMost of rabid-dog bites develop into rabies • HDCV is at present the best ARVHDCV is at present the best ARV • Rabies is not transmitted by contaminated corneal graftRabies is not transmitted by contaminated corneal graft • Rabies is always endemic in the forestRabies is always endemic in the forest
- 68. MCQMCQ • Vaccinating pet dogs is essential to control rabiesVaccinating pet dogs is essential to control rabies • Everyone should be vaccinated against rabiesEveryone should be vaccinated against rabies • Rabies virus spread to CNS via bloodRabies virus spread to CNS via blood • It can be transmitted by foodIt can be transmitted by food • Saliva contains R virus after brain involvementSaliva contains R virus after brain involvement • Rabies can be eradicatedRabies can be eradicated
- 70. Next LecNext Lec Snake BiteSnake Bite
- 71. THANK YOU
Hinweis der Redaktion
- Hydrophobia is common with furious R (80%); 20% are paralytic/dumb R (muscle weakness, loss of sensation); does not usually cause it R causes H in the encephalitic stage which means when it affects the brain and causes inflam of multiple areas of the brain. It affects the complex swallowing areas in the brain. Initially, the pt has involuntary contractions of neck muscles when he drinks water. Later, he starts contracting even at the thought of water. RV is a neurotropic virus; it travels through nerves because of its preference to attach to Ach receptors in the neurons. That is how the virus spreads
- Bats possible source of rabies
- Rabies is present on all continents except the Antarctica Dog vax is more cost-effective than human PEP
- Vax 70% of dogs, prevents transmission. A R. elimination program in BD, with mass dog vax, has resulted in a 50% fall in human deaths 2010-13
- The reservoirs vary geographically; commonly dogs, bats, raccoons, foxes, cats, and skunks. The primary cause of human rabies worldwide is from dogs In the US, dogs are vaccinated, the primary c/of R in humans is from wildlife (particularly bats)
- Transmission of R usually begins with infected saliva. Routes: skin, mucous m. (eyes, nose, mouth), aerosol, and corneal transplant. The most common is through bite. Following inf, RV enters an eclipse phase and cannot be easily detected within the host. This may last for several d-mo. Both direct entry of virus into PN and indirect entry after viral replication in non-nervous tissue (muscle) occur. During the eclipse phase, the host immune defenses may confer CMI as RV is a good Ag. The uptake of virus into PN is important for progressive inf. After uptake into PN, RV is transported to CNS via retrograde axoplasmic flow. Typically this occurs via sensory and motor nerves. The IP may vary from a few days to several years, but is typically 1-3 mo. Dissemination of RV within the CNS is rapid, and includes early involvement of limbic system neurons Active cerebral infection is followed by passive centrifugal spread of RV to PN. The amplification of inf within the CNS occurs through cycles of viral replication and cell-to-cell transfer of progeny virus. Centrifugal spread of virus may lead to the invasion of highly innervated sites: salivary glands. During this period of cerebral infection, the classic behavioral changes of R develop
- Encephalomyelitis. Perivascular infiltration with lymphocytes, polys, and plasma cells throughout CNS. R frequently causes cytoplasmic inclusions (Negri bodies) in especially pyramidal cells of the hippocampus and Purkinje cells of the cerebellum. These are areas of active viral replication. Several factors may affect the outcome: the virus variant, inoculum, route and location of exposure, as well as host age and host defenses
- Later R: difficulty swallowing, panic when to drink, and the pt. can&apos;t quench its thirst. Aerophobia: sensitivity to air or its movement
- Rabies diagnosis in humans. Immunohistochemistry (IHC) Ultrastructure Amplification methods New standard DFA protocol for rabies Rabies diagnosis in animals The direct fluorescent antibody test (dFA) is the test most frequently used to diagnose rabies. This test requires brain tissue from animals suspected of being rabid. The test can only be performed post-mortem Rabies diagnosis in humans Several tests are necessary to diagnose rabies ante-mortem (before death) humans; no test sufficient. Tests are performed on samples of saliva, serum, CSF, and skin biopsies of hair follicles at the nape of the neck. Saliva can be tested by virus isolation or reverse transcription followed by polymerase chain reaction (RT-PCR). Serum and spinal fluid are tested for antibodies to rabies virus. Skin biopsy specimens are examined for rabies antigen in the cutaneous nerves at the base of hair follicles. The importance of routine rabies tests Rapid and accurate laboratory diagnosis of rabies in humans and other animals are essential for timely administration of postexposure prophylaxis. Within a few hours, a diagnostic laboratory can determine whether or not an animal is rabid and inform the responsible medical personnel. The laboratory results may save a patient from unnecessary physical and psychological trauma, and financial burdens, if the animal is not rabid. In addition, identification of positive rabies cases may aid in defining current epidemiologic patterns of disease and provide appropriate information for the development of rabies control programs. Essential characteristics for routine rabies test The nature of rabies disease dictates that laboratory tests be standardized, rapid, sensitive, specific, economical, and reliable. Laboratory tests for rabies The standard test for rabies testing is dFA. This test has been thoroughly evaluated for more than 40 years, and is recognized as the most rapid and reliable of all the tests available for routine use. All rabies laboratories in the United States perform this test (post-mortem) on animals suspected of having rabies. Other tests for diagnosis and research, such as electron microscopy (EM), histologic examination, immunohistochemistry (IHC), RT-PCR, and isolation in cell culture are useful tools for studying the virus structure, histopathology, typing, and virulence of rabies viruses. Direct fluorescent antibody test (dFA) The dFA test is based on the observation that animals infected by rabies virus have rabies virus proteins (antigen) present in their tissues. Because rabies is present in nervous tissue (and not blood like many other viruses), the ideal tissue to test for rabies antigen is brain. The most important part of a dFA test is flouresecently-labelled anti-rabies antibody. When labelled antibody is incubated with rabies-suspect brain tissue, it will bind to rabies antigen. Unbound antibody can be washed away and areas where antigen is present can be visualized as fluorescent-apple-green areas using a fluorescence microscope. If rabies virus is absent there will be no staining. Antigen detection by dFA The rabies antibody used for the dFA test is primarily directed against the nucleoprotein (antigen) of the virus (see The Virus section on viral structure). Rabies virus replicates in the cytoplasm of cells, and infected cells may contain large round or oval inclusions containing collections of nucleoprotein (N) or smaller collections of antigen that appear as dust-like fluorescent particles if stained by the dFA procedure
- Diagnosis. Human R can be confirmed intra-vitam and post mortem by various diagnostic techniques aimed at detecting whole virus, viral antigens or nucleic acids in infected tissues (brain, skin, urine or saliva). Antigen detection by dFA General histopathology Negri bodies Immunohistochemistry (IHC) Ultrastructure Amplification methods New standard DFA protocol for rabies Rabies diagnosis in animals The direct fluorescent antibody test (dFA) is the test most frequently used to diagnose rabies. This test requires brain tissue from animals suspected of being rabid. The test can only be performed post-mortem Rabies diagnosis in humans Several tests are necessary to diagnose rabies ante-mortem (before death) humans; no test sufficient. Tests are performed on samples of saliva, serum, CSF, and skin biopsies of hair follicles at the nape of the neck. Saliva can be tested by virus isolation or reverse transcription followed by polymerase chain reaction (RT-PCR). Serum and spinal fluid are tested for antibodies to rabies virus. Skin biopsy specimens are examined for rabies antigen in the cutaneous nerves at the base of hair follicles. The importance of routine rabies tests Rapid and accurate laboratory diagnosis of rabies in humans and other animals are essential for timely administration of postexposure prophylaxis. Within a few hours, a diagnostic laboratory can determine whether or not an animal is rabid and inform the responsible medical personnel. The laboratory results may save a patient from unnecessary physical and psychological trauma, and financial burdens, if the animal is not rabid. In addition, identification of positive rabies cases may aid in defining current epidemiologic patterns of disease and provide appropriate information for the development of rabies control programs. Essential characteristics for routine rabies test The nature of rabies disease dictates that laboratory tests be standardized, rapid, sensitive, specific, economical, and reliable. Laboratory tests for rabies The standard test for rabies testing is dFA. This test has been thoroughly evaluated for more than 40 years, and is recognized as the most rapid and reliable of all the tests available for routine use. All rabies laboratories in the United States perform this test (post-mortem) on animals suspected of having rabies. Other tests for diagnosis and research, such as electron microscopy (EM), histologic examination, immunohistochemistry (IHC), RT-PCR, and isolation in cell culture are useful tools for studying the virus structure, histopathology, typing, and virulence of rabies viruses. Direct fluorescent antibody test (dFA) The dFA test is based on the observation that animals infected by rabies virus have rabies virus proteins (antigen) present in their tissues. Because rabies is present in nervous tissue (and not blood like many other viruses), the ideal tissue to test for rabies antigen is brain. The most important part of a dFA test is flouresecently-labelled anti-rabies antibody. When labelled antibody is incubated with rabies-suspect brain tissue, it will bind to rabies antigen. Unbound antibody can be washed away and areas where antigen is present can be visualized as fluorescent-apple-green areas using a fluorescence microscope. If rabies virus is absent there will be no staining. Antigen detection by dFA The rabies antibody used for the dFA test is primarily directed against the nucleoprotein (antigen) of the virus (see The Virus section on viral structure). Rabies virus replicates in the cytoplasm of cells, and infected cells may contain large round or oval inclusions containing collections of nucleoprotein (N) or smaller collections of antigen that appear as dust-like fluorescent particles if stained by the dFA procedure.
- programs of animal vax and elimination of stray dogs can reduce human rabies, but exposure to rabid dogs is still the cause of &gt;90% of human rabies and of &gt;99% of human deaths
- Eliminating rabies in dogs Vx dogs is the most cost-effective strategy. It will drive down not only the deaths but also the need for PEP Immunization in people. The same vax can be used for PrEP recommended for travelers spending a lot of time in rural areas, bicycling, camping, or hiking as well as for long-term travelers and expatriates living in areas with a significant risk. PrEP is also recommended for lab workers and other rabies-related viruses, and people involved in any activities that might bring them professionally or otherwise into direct contact with bats, carnivores, and other mammals in rabies-affected areas. As children are considered at higher risk, may receive more severe bites, or may not report bites, their immunization could be considered if living in or visiting high-risk areas
- Spelunkers: cave explorers
- Purpose of PrEP: First, although it does not eliminate the need for additional medical attention after a exposure, it simplifies therapy by eliminating the need for HRIG and decreasing the number of vaccine doses needed – a point of particular importance for persons at high risk of being exposed to rabies in areas where immunizing products may not be available, and it minimizes SE to multiple doses of vaccine. Second, it may enhance immunity in persons whose postexposure Rx might be delayed. Finally, it may provide protection to persons with inapparent exposures to rabies. It consists of 3 doses: on days 0, 7, and 21 or 28
- RIG: Rabies Immune Globulin
- Vero cells are used in cell cultures; first isolated from kidney epith cells from an African green monkey in 1962 They are used for: screening toxin of E coli (&quot;Vero toxin“ or &quot;Shiga-like toxin“), for growing virus; testing for rabies virus, growth of viral stocks for research purposes, host cells for eukaryotic parasites. The Vero cell lineage is continuous and aneuploid meaning an abnormal number of chromosomes. Vero cells are interferon-deficient; they do not secrete interferon when infected by viruses though they have Interferon receptor
- Local treatment of the wound: Removing the RV at the site by chemical or physical means is an effective means of protection, prompt local treatment of all bite wounds and scratches that may be contaminated with RV is important. Immediate and thorough flushing and washing of the wound for a minimum of 15 min with soap and water, detergent, povidone iodine or other substances that kill the rabies virus
- Signs and symptoms The first symptoms of rabies may be nonspecific flu-like signs — malaise, fever, or headache, which may last for days. There may be discomfort or paresthesia at the site of exposure (bite), progressing within days to symptoms of cerebral dysfunction, anxiety, confusion, agitation, progressing to delirium, abnormal behavior, hallucinations, and insomnia. The acute period of disease typically ends after 2 to 10 days (6). Once clinical signs of rabies appear, the disease is nearly always fatal, and treatment is typically supportive. Disease prevention is entirely prophylactic and includes both passive antibody (immune globulin) and vaccine. Non-lethal exceptions are extremely rare. To date only six documented cases of human survival from clinical rabies have been reported and each included a history of either pre- or postexposure prophylaxis.