Table 3.
Key study findings.
| key finding | level of certainty | new data needed |
|---|---|---|
| key findings from prior studies | ||
| FMDV is trophic for animal skin | well established | |
| skin is a major secondary FMD viral replication site | well established | |
| FMDV is present both in skin lesions and in skin appearing clinically normal | probable | |
| FMDV skin concentrations are highest in the epidermal layer | probable | FMDV concentration and infectivity of apparently normal stratum corneum samples (by species and body region) |
| in the normal skin growth cycle, epidermal skin cells are shed into the environment | well established | |
| skin cells constitute a significant fraction of ambient aerosols and settled dust | well established | |
| skin cell aerosols can deposit within the respiratory system | probable | |
| airborne skin cells are a known vehicle for disease transmission | well established for bacteria; probable for viruses (e.g. VZV) | measurement of concentration and infectivity of FMDV on exfoliated skin cell surface and intracellularly in fresh and environmentally aged skin cells |
| dead animals emit infectious aerosols | probable | confirmatory studies; current data come from a single study |
| peak FMDV aerosol emissions are coincident with peak FMDV skin concentrations | well established | |
| FMDV has high stability in detached (whole animal) skin | probable | confirmatory studies; current data come from two studies |
| key findings from this study | ||
| estimates of the peak FMDV-infected animal skin cell shedding rate | ||
| — are comparable to measured peak whole-animal aerosol emissions | probable | skin cell shedding rates for domestic animals; updated FMDV skin concentrations |
| — exceed the minimum infectious dose by orders of magnitude | possible | degree to which FMDV is liberated from skin cells in the respiratory system |
| stability of naturally generated infectious FMDV aerosols is consistent with that expected of FMDV-infected skin aerosols | possible | confirmatory studies; conclusion based on data from a single study and assumption that FMDV stability in skin aerosols is comparable to whole skin |
| the whole-animal FMDV infectious aerosol size distribution is consistent with that expected for skin cell aerosols | well established | enhanced characterization of (i) skin aerosol size distribution and (ii) infectious whole-animal FMDV aerosol size distribution |
| utility of study hypothesis | ||
| may point to new methods for FMD surveillance (e.g. settled dust) | possible | stability and infectivity of FMDV in dust |
| potential to develop new, more effective disease control measures | possible | degree to which infectious skin cells contribute to disease transmission |
| may lead to new studies on the persistence of the virus in the environment | possible | analysis of settled dust and other potential environmental reservoirs |
| may lead to better understanding of sources and vehicles of infectious aerosols with applicability to other diseases | possible | degree to which infectious skin cells contribute to viral disease transmission |