Dose-Response Models for Eastern US, Western US and Venezuelan Equine Encephalitis Viruses in Mice - Part II: Quantification of the Effects of Host Age on the Dose Response.

Many infectious disease hazards demonstrate higher susceptibility with regards to younger host ages. This trend of increased susceptibility with decreasing host age can also lead to an increased likelihood of mortality, and prolonged/chronic health effects. For quantitative microbial risk assessment (QMRA) modeling, the ability to quantify the effect of host age in the dose response model can allow modelers to account for these effects mechanistically. Additionally, QMRA modelers using age-dependent dose response models can model entire populations within the dose-response itself rather than modeling age ranges using susceptibility factors. This research developed host-age dependent exponential and beta Poisson dose response models for Eastern, Western and Venezuelan encephalitis viruses (EEV, WEV and VEV respectively) for two routes - intracranial and intraperitoneal. Improvement in fit was statistically tested as a means of assessing the benefit of including age dependency into the dose response models. EEV demonstrated improvement in fit using host-age dependency only for the exponential model except for intracranial exposure. EEV demonstrated an improvement in fit when using age dependency in the beta Poisson dose response model for both exposure routes. VEV demonstrated an improvement in fit using age dependency for both exposure routes. WEV demonstrated an improvement in fit for intracranial exposure, but neither of the age dependent dose-response models provided a good fit for WEV intraperitoneal exposure.

Development of a relative risk model for drinking water regulation and design recommendations for a peri urban region of Argentina.

Argentina is a developing Latin American nation that has an aim of achieving the United Nations Millennium Development Goals for potable water supplies. Their current regulations however, limit the continued development of improved potable water quality and infrastructure from a microbiological viewpoint. This is since the current regulations are focused solely to pathogenic Eschericia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) and fecal indicators. Regions of lower socioeconomic status such as peri-urban areas are particularly at risk due to lessened financial and political ability to influence their environmental quality and infrastructure needs. Therefore, a combined microbiological sampling, analysis and quantitative microbial risk assessment (QMRA) modeling effort were engaged for a peri-urban area of Salta Argentina. Drinking water samples from home taps were analyzed and a QMRA model was developed, results of which were compared against a general 1:10,000 risk level for lack of a current Argentinian standard. This QMRA model was able to demonstrate that the current regulations were being achieved for E. coli but were less than acceptable for P. aeruginosa in some instances. Appropriate health protections are far from acceptable for Giardia for almost all water sources. Untreated water sources were sampled and analyzed then QMRA modeled as well, since a significant number of the community (∼9%) still use them for potable water supplies. For untreated water E. coli risks were near 1:10,000, however, P. aeruginosa and Giardia risks failed to be acceptable in almost all instances. The QMRA model and microbiological analyses demonstrate the need for improved regulatory efforts for the peri-urban area along with improved investment in their water infrastructure.

Risk of Giardia infection for drinking water and bathing in a peri-urban area in Sao Paulo, Brazil.

A high incidence of waterborne diseases is observed worldwide and in order to address contamination problems prior to an outbreak, quantitative microbial risk assessment is a useful tool for estimating the risk of infection. The objective of this paper was to assess the probability of Giardia infection from consuming water from shallow wells in a peri-urban area. Giardia has been described as an important waterborne pathogen and reported in several water sources, including ground waters. Sixteen water samples were collected and examined according to the US EPA (1623, 2005). A Monte Carlo method was used to address the potential risk as described by the exponential dose response model. Giardia cysts occurred in 62.5% of the samples (<0.1-36.1 cysts/l). A median risk of 10⁻¹ for the population was estimated and the adult ingestion was the highest risk driver. This study illustrates the vulnerability of shallow well water supply systems in peri-urban areas.