Aerosol infectious dose

In the case of chemical pesticides, these include factors such as molecular weight and vapor pressure that determine the rate of evaporation into air of the pesticide in an applied material such as paint, or the release from aqueons solntion. In the case of biological agents, these include, for example, pathogenicity to hnmans, allergenicity, infectious dose levels and aerosol particle size distribntion. 

Death occurs 24 h after the onset of this second phase secondary to toxemia and suffocation (Atlas, 2002 Bales, 2002 Dixon et al., 1999 Friedlander, 1999). Although the lung is the primary site of infection here, inhalational anthrax is not considered a trae pneumonia. In most, but not all cases, there is no infection in the lungs (Abramova et al., 1993 Albrink, 1961). An infectious dose is estimated at 8,000 to 50,000 spores via aerosol (Franz et al., 1997). 

Different methods of delivery of nanotechnology-enabled CB weapons wiU likely require different countermeasures. Delivery via aerosol, food, water, or skin will potentially elicit different physiological and biological reactions and wiU require different treatments. For example, prions and other proteins may be able to attach to nanoenabled aerosol particles that have the capability to cross the blood-brain barrier. Research to understand delivery mechanisms for prions, levels of infectious doses, and overall time dependence is needed. 

Sensitivity to infectious dose level is probably not important for early warning, since an aerosol cloud intended to kill or incapacitate even one individual will certainly involve concentrations far in excess of the infectious dose (later decisions about clean-up and reoccupation of contaminated areas may need that level of sensitivity, but speed will be less of an issue, and respiratory protection will allow use of more sensitive point detectors). Specificity also may not be critical in the use of stand-off detectors. For example, we may just need to be alerted to the presence of live biologicals. This is also true for the control of contaminated environments, determination of decon efficacy, and dynamic threat assessment (real-time assessment of a threat, including remediation). 

Aerobiologists at the U.S. Army Medical Research Institute of Infectious Diseases (Fort Detrick, MD) have developed a reproducible, head-only ricin aerosol exposure model for laboratory nonhuman primates (NHP) that yielded acute LCtso values for African green monkeys or rhesus monkeys corresponding to approximately 6-10 or 15 pg/kg, respectively (Wilhelmsen and Pitt, 1996). Exposure of NHP to aerosolized ricin (particle size 1-2 pm) caused a dose-dependent toxicity that is delayed from 8 to 24 h early anorexia and lethargy were frequently observed, followed by gastric distress, hypothermia, hypotension, acute respiratory distress, and death. Rhesus monkeys exposed to the equivalent of approximately 20-40 pg/kg ricin by aerosol died from acute respiratory distress about 36-48 h after exposure necropsy revealed fibrinopurulent pneumonia, acute inflammation of the trachea and airways, and massive pulmonary alveolar flooding (Wilhelmsen and Pitt, 1996). 

Although natural infections are acquired by mosquito bite, these viruses are also highly infectious in low doses as aerosols. They can be produced in large amounts in inexpensive and unsophisticated systems, are relatively stable, and are readily amenable to genetic manipulation. For these reasons, the equine encephalomyelitis viruses are classic biological warfare threats. 

Biological samples from patients are generally not as useful for diagnosis of intoxications as they are for diagnosis of infectious diseases or chemical intoxications. The same is true of postmortem samples. Ricin can be identified with immunoassays in extracts of lung, liver, stomach, and intestines up to 24 hours after aerosol exposure. High doses of ricin can be identified in fixed lung tissue of aerosol-exposed laboratory animals by immunohistochemical methods. The staphylococcal enterotoxins can be detected by immunoassay in bronchial washes. Like blood and swab samples, postmortem tissue or fluid samples should be kept cold, preferably frozen, until they can be assayed. 

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