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2.characteristics of biowarfare agents and their methods of spread
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2.characteristics of biowarfare agents and their methods of spread

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  • 1. Potential Biowarfare Agents and their Methods of Spread Dr Kamran Afzal Classified Pathologist and Microbiologist
  • 2. I. Potential BW Agents
  • 3. Potential BW Agents: CDC Category A FEATURES AGENTS Easily disseminated or  Anthrax transmitted person -  Plague person  Smallpox High mortality – major  Tularemia public health impact  Viral Public panic and social haemorrhagic fevers disruption  Botulinum toxin Special action for public health preparedness
  • 4. Potential BW Agents: CDC Category B FEATURES AGENTS Moderately easy to  Brucellosis disseminate Q fever Moderate morbidity, low mortality  Glanders & melioidosis Require enhancement of  VEE, EEE and WEE diagnostic capacity and  Enteric pathogens surveillance  Other toxins
  • 5. Potential BW Agents: CDC Category C FEATURES AGENTS Emerging agents  Nipah virus Availability  Hantaviruses Easy to produce and  Tickborne HF disseminate Potential for high mortality  Tickborne encephalitis and morbidity  Yellow fever  MDR-TB
  • 6. Desirable Features of Biological Agents tobe used as Biological WeaponsLess expensiveAvailableEasily transported/concealed and dispersedIncubation period “Hides Tracks” of perpetratorModifiable (resistance, virulence)Produce ‘anxiety factor’, over-loading health servicesProduce social disruption, reduce productivityImpact on morale, create epidemic
  • 7. Characteristics of BW Agent Infective dose should be low Should be highly contagious Should be stable and robust Can be aerosolized (1-10 µm) Survives sunlight, drying, heat Cause lethal or disabling disease Person-to-person transmission Should consistently produce given effect, death or disease Should have a short and predictable incubation period
  • 8. Characteristics of BW AgentThe agent should be amenable to easy and economical mass productionStorage methods should be availableTarget population should have little or no natural or acquired immunityProphylaxis against the agent should not be available to the target populationLittle or no treatment for the disease caused by the agent should be availableThe aggressor should have means to protect its own forces and population
  • 9. Characteristics of BW AgentIt should be capable of efficient disseminationStable during dissemination. If it is to be delivered via an aerosol, it must survive and remain stable in air until it reaches the target populationIf it cannot be delivered via an aerosol, living vectors (e.g. fleas, mosquitoes or ticks) should be available for dispersal of some form of infected substrateAfter delivery, the agent should have a low persistence, surviving only for a short time, thereby allowing a prompt occupation of the attacked area by the aggressor’s troops
  • 10. Aerosol : Infectivity Relationship Particle Size Infection The ideal aerosol (Micron, Mass Severity Mediancontains a homogeneous Diameter) Less population Severe of 2 or 3 micron 18-20 particulates that contain one or more 15-18 viable organisms 7-12 Maximum human 4-6 (bronchioles) respiratory infection is a particle that falls within 1-5 (alveoli) 1 to 5 micron size More Severe Source: San Diego Medical Society
  • 11. Uniqueness of Biological Attacks Responders – medical Response System – untested Medical System may be a target Biological  Onset - incubation, primary cases  Secondary cases – contagiousness, contamination
  • 12. Difficulties in useIncubation period ranges from hours to daysRain, sunlight and temp extremes reduce the virulenceNatural and acquired immunity against pathogens make it impossible to predict the exact number of casualties from any BW attackConsequently, BW today is primarily for harassment and special operations
  • 13. Potential BW AgentsBacteria Mode of I.P. Mortality Vaccine Treatment TransmissionBacillus anthracis A, D, I 1–7 5-100 + E(Anthrax)Brucella group A, D, I 5-21 2-6 + E(Brucellosis)Francisella tularensis A, D, I, V 1-10 <30 ++ E(Tularemia)Yersinia pestis A, V 2-6 25-100 +++ E(Plague)Vibrio cholerae (Cholera) I 1-5 15-90 +++ ECorynebacterium diphtheriae A, D 2-5 5-12 +++ E(Diphtheria)A - Aerosol D - Direct contact I - Ingestion V - Vector E - Effectivetreatment available N - Non-specific treatment
  • 14. Potential BW AgentsSalmonella typhi I 6-21 7-14 +++ E(Typhoid fever)Rickettsiae V 6-15 10-40 +++ ERickettsia prowazeki(Epidemic or louse-borne typhyus)Rickettsia mooseri V 6-14 2-5 E(Endemic or flea-borne typhyus) -Rickettsia rickettsii V 3-10 30 (Approx) E(Rocky Mountain spotted fever) -Coxiella burneti A, I 14-21 <1 ++ E(Q fever)A - Aerosol D - Direct contact I - Ingestion V - Vector E - Effectivetreatment available N - Non-specific treatment
  • 15. Potential BW AgentsViruses Mode of I.P. Mortality Vaccine Treatment TransmissionGroup A Arboviruses V 4-24 60 - NEastern equine encephalitis (EEE) (Approx) Venezuelan equine encephalitis V 4-24 <1 ++ N (VEE)Group B Arboviruses V (mosquito) 4-24 - - N St. Louis encephalitis Japanese B encephalitis V (mosquito) 5-15 10-80 ++ N Russian spring-summer V (tick) 7-14 3-40 + N encephalitis (RSSE) Yellow fever V (mosquito) 3-6 5-40 +++ NA - Aerosol D - Direct contact I - Ingestion V - Vector E - Effectivetreatment available N - Non-specific treatment
  • 16. Potential BW AgentsDengue virus V (mosquito) 4-10 <1 - NUngrouped Arbovirus V (mosquito) 4-6 1 - NRift Valley fever virusPoxvirus A, D 7-16 1-35 +++ NVariola virus (Smallpox)Myxovirus A, D 6-365 100 ++ ERabies virusInfluenza virus A, D 1-2 - +H5N1 EA - Aerosol D - Direct contact I - Ingestion V - Vector E - Effectivetreatment available N - Non-specific treatment
  • 17. Potential BW AgentsFungi A, D 10-21 1-51 - ECoccidioides immitis(Coccidioidomycosis)Histoplasma A 5-18 - - EcapsulatumA - Aerosol D - Direct contact I - Ingestion V - VectorE - Effective treatment available N - Non-specific treatment
  • 18. Potential BW Toxins NAME SOURCE EFFECTSBotulinum toxin A Clostridium botulinum Dizziness, sore throat, and dry mouth followed by paralysis Death by suffocation (respiratory paralysis) or heart failureRicin Castor bean plant Nausea, vomiting, bloody diarrhea, and drowsiness Death by kidney failure (uremia)Saxitoxin Dino-flagellates Tingling around face, loss of sensation(Shellfish toxin) in extremities Death by paralysisTricothecenes- Fungus Nausea, vomiting, diarrheamyco toxins Death by internal hemorrhaging
  • 19. Comparison of Bioterrorism Toxins and Chemical AgentsToxins ChemicalNatural origin Man-madeGenerally more toxic Generally less toxicDifficult, small-scale Large-scale, industrialproduction productionNone volatile Many volatileAerosol delivery Vapor or aerosol delivery
  • 20. Comparison of Bioterrorism Toxins and Chemical AgentsToxins ChemicalOdorless and tasteless Noticeable odor or tasteNot dermally active* Dermally activeLegitimate medical uses No legitimate medical useMany effective immunogens Poor immunogens * Exceptions, trichothecene (T-2) mycotoxins
  • 21. II. Methods of Spread
  • 22. Modes of Exposure / Routes Of EntryInhalation  Inhalation of spores, droplets and aerosols  Powder  Spray - Small scale - Large scale  Explosive  Pulmonary infection is by far most effective
  • 23. Ingestion Food  Potentially significant route of delivery  Secondary to either purposeful or accidental exposure to aerosol Water  Capacity to affect large numbers of people  Dilution factor  Water treatment may be effective in removal of agents
  • 24. Inoculation / Contact / Absorption  Cuts/Abrasions on skin or mucosal membranes  Vectors (mosquitoes, ticks, fleas and lice)  Fomites  Explosive
  • 25. Delivery via Aerosols (Inhalation)Aerosol- Small droplet particles composed of many organisms dispersed into air and carried by air currents Explosive bomb-lets consist of low grade explosive, explode on impact and release biological agent which disseminates as aerosol Generators have biological agents filled in a pressure chamber and are released through a nozzle Agent may by released during flight over enemy area or covertly set up in the target areaSlurred mixture – Spray of Anthrax and Botulinum toxin
  • 26. Spray tanks can be carried by aircrafts or missile. Tanks contain large quantity of agent and can be effective over a large areaVariables altering effectiveness of a delivery system Particle size of the agent Stability of the agent under desiccating conditions, UV light Wind speed, wind direction, and atmospheric stability
  • 27. Anthrax TransmissionInhalation Spores in Postal envelopes Spray  Aeroplane  Spray machine Aerosol  AerialbombsSkin inoculationIngestion
  • 28. Smallpox TransmissionCommon: Person – to –person by large airborne droplets  Face-to-face contact (i.e., 6 feet)  Should be interrupted by mask protection (e.g., NIOSH N-95)Rare: Airborne over long distanceRare: As fomites (e.g., Bed linens)Not transmitted by food
  • 29. VHF Agents TransmissionFrom reservoirs to vectors to humansLess common route Contact with infected animal tissues, urine, feces, and other excreta Via Aerosols
  • 30. ConclusionBW agents are easy to acquire, synthesize and use (Poor man’s nukes) Small amount of agents can kill hundreds of thousands of people in a metropolitan area Concealment, transportation, and dissemination of biological agents relatively easyBW agents are difficult to detect or protect against; being invisible, odorless, and tasteless, dispersal can be performed silentlyTransmitted via inhalation, ingestion and inoculation