Academic journal article Environmental Health Perspectives

Precipitation and Salmonellosis Incidence in Georgia, USA: Interactions between Extreme Rainfall Events and Antecedent Rainfall Conditions

Academic journal article Environmental Health Perspectives

Precipitation and Salmonellosis Incidence in Georgia, USA: Interactions between Extreme Rainfall Events and Antecedent Rainfall Conditions

Article excerpt

Introduction

Every year, over 9 million cases of foodborne illness occur in the United States. Nontyphoidal Salmonella is estimated to cause 1 million of these cases (with 23,000 hospitalizations and 450 deaths) and is second only to norovirus as the most common foodborne pathogen (Scallan et al. 2011). Infection with nontyphoidal Salmonella is associated with diarrhea, abdominal cramps, and fever and these symptoms are often self limiting (Giannella 1996). Nationwide, Salmonella is also estimated to have a yearly economic burden of $3.7 billion (Hoffmann et al. 2015). The southeastern region of the United States consistently has higher incidence rates of salmonellosis compared with other parts of the country (CDC 2016)--its rate was 11% higher than the national rate in 2015 (CDC 2017).

Numerous public health initiatives have been undertaken to better understand the epidemiology of foodborne diseases such as infections from Salmonella. The U.S. Centers for Disease Control and Prevention (CDC) has maintained its Foodborne Disease Active Surveillance Network (FoodNet) since 1995. FoodNet represents a long-standing collaboration between the CDC, the U.S. Food and Drug Administration (FDA), the U.S. Department of Agriculture (USDA), and 10 state health departments. FoodNet conducts rigorous surveillance and promotes behavioral changes to limit the public's contact with foodborne diseases. However, although the United States has seen a marked decrease in the incidence of certain foodborne illnesses over the past two decades, this reduction has not been observed for salmonellosis. In fact, salmonellosis incidence has experienced an overall 35% increase since 2001--national incidence was approximately 11 cases per 100,000 population in 2001 but in 2015, it was 14.9 (CDC 2016; CDC 2017). In Georgia, there has been an 11% increase since 2001 (data obtained through GA DPH's Public Health Information Portal: https://dph.georgia. gov/phip-data-request).

There are over 2,500 serovars of Salmonella, but human illnesses have been attributed to fewer than 100 serovars (CDC 2015). Salmonellae live and reproduce in the gastrointestinal tracts of humans and other animals and are shed through feces. Direct or indirect contact with contaminated feces can result in infection. Humans can come in contact with the pathogen through fecal matter in or on food and water and through contact with wild and domesticated animals (Ricke et al. 2013). When Salmonella is isolated from clinical and food samples during outbreaks, certain serovars (e.g., Enteritidis, Heidelberg, Kentucky) are often associated with animal-derived food commodities (Shah et al. 2017) and others (e.g., Muenchen, Javiana), with plant-derived food commodities (Gomba et al. 2016; Reddy et al. 2016). The serovars found on contaminated plant-derived food commodities have also been isolated from non-livestock reservoirs, such as birds, amphibians, water, and soil (Jackson et al. 2013; Micallef et al. 2012; Srikantiah et al. 2004). This may indicate that these serovars are more often associated with environmental reservoirs as opposed to animal-derived food production, and we therefore refer to them here as environmental serovars. These environmental serovars include: Javiana, Litchfield, Mbandaka, Muenchen, Poona, and Senftenberg. In Georgia, many of these serovars are also frequently detected in clinical cases (Maurer et al. 2015). Approximately 19% of the cases from 1997 to 2016 were attributed to these serovars (data obtained through GA DPH's Public Health Information Portal: https://dph.georgia.gov/phipdata-request). The prevalence of infection with environmental serovars may indicate the potential for human exposure to Salmonella in the environment.

Environmental transmission is further supported by the regular detection of Salmonella in surface water and samples from other environmental sources in Georgia and neighboring states (Antaki et al. 2016; Haley et al. …

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