Abstract
Water contaminated with microbiological and chemical constituents can cause a variety of diseases. Water bodies may become contaminated by wild and domestic animal feces, agricultural runoff or sewage, and are often overlooked as a reservoir and source of human infection by pathogenic microorganisms. The objectives of this study were to evaluate the presence of the zoonotic pathogens, Salmonella spp. and Listeria monocytogenes, in various water bodies located in urban and rural areas in the north of Portugal. Water samples were collected from six sites, including natural and artificial ponds, in two different time periods. Several water quality physicochemical parameters, as well as fecal indicator bacteria, were evaluated. High levels of total coliforms (>1.78 log CFU/100 mL) were detected in all samples, and substantial numbers of Enterococcus (>2.32 log CFU/100 mL) were detected in two ponds located in a city park and in an urban garden. Escherichia coli counts ranged from undetectable to 2.76 log CFU/100 mL. Salmonella spp. was isolated from two sites, the city park and the natural pond, while L. monocytogenes was isolated from three sites: the city garden, the natural pond and the artificial pond, both in the rural area. These data show that artificial and natural ponds are a reservoir of fecal indicator bacteria and enteric and zoonotic pathogens. This may impact the potential risks of human infections by potential contaminants during recreational activities, being important for assessing the water quality for strategic management of these areas.
Highlights
Zoonoses, i.e., infections caused by pathogenic organisms that jump from an animal reservoir to humans, either through direct contact or through contaminated food, water or environment, are a continuous threat to human health [1]
Two artificial ponds were located in a city garden (P1, Figure 1a) and a city park (P2, Figure 1b), respectively; one small pond was located on a roof terrace in the city, at the level of the seventh floor (P3, Figure 1c); an artificial pond was set up as a biological swimming pool, i.e., a swimming pool where the traditional chemical disinfection is replaced by natural biological processes for water purification, located in a private house in a rural area, serving three persons (P4, Figure 1d); a natural pond located in a rural protected area (P5, Figure 1e); and, an artificial pond (P6, Figure 1f), receiving treated wastewater by a constructed wetland in a tourism house
The lower pH values were verified for the natural pond (P5) (5.570), while in the artificial ponds, pH varied between 6.138–7.860, whereas the highest value (8.993) was detected in the city park pond (P2)
Summary
I.e., infections caused by pathogenic organisms (bacteria, viruses or parasites) that jump from an animal reservoir to humans, either through direct contact or through contaminated food, water or environment, are a continuous threat to human health [1]. Listeriosis and salmonellosis are more frequently associated with the consumption of contaminated animal and animal-derived food products (e.g., fish, meat, poultry, eggs, dairy products, etc.), or by non-animal products (e.g., fresh produce) contaminated by agricultural environments, via soil, irrigation water or manure used as fertilizer [6]. Some cases of disease caused by direct contact with infected animals or indirect contact with a contaminated environment have been reported [7,8]. A diverse range of reservoirs have been associated with these pathogens, including the gut of healthy farm animals (cattle, swine or poultry) and wild animals, pets, fish or rodents [9], and, they are expected to be present in the natural environment
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