Salmonella infection in children from the wastewater-spreading zone of Marrakesh city (Morocco)

Characteristics and dynamics of Salmonella diversity and prevalence of biomarker genes in Port Blair Bays, South Andaman, India

Salmonella is a major cause of morbidity and mortality in humans worldwide, and the infection with multidrug-resistant strains can cause severe diseases. Many coastal cities around the world discharge their wastewaters into the marine environment. These wastewaters contain a variety of pathogenic microorganisms that may have a role in the contamination of this ecosystem and have potential risks for public health. Using an environmental approach, the present study investigated the presence of Salmonella in sediment and water samples collected from Port Blair Bays. In this environmental approach, the provided information about the diversity of the Salmonella serovars, antibiotic resistance and the prevalence of virulence factors in Salmonella, especially from the coastal waters of Port Blair Bays. The occurrence of Salmonellae was significantly higher in water column samples (2.9%) than in those taken from the marine sediments (0.7%). Of the 133 positive Salmonella strains, 22 different serovars were identified. Salmonella enterica serovar Senftenberg was the predominant serovar, being represented by 54 isolates (42.5%), followed by serovar Typhimurium (19 isolates [15%]) and serovar Agona (12 isolates [9.4%]). The presence of virulence genes (filC, sitC, hilA, invA, sipC, hilD, hilC, invF, invE, invH, sipF, aadA, pare, gyrA, spaP and parC) and susceptibility studies with 10 selected antibiotics were also performed. The results of this study revealed that all Salmonella isolates were positive for targeted virulence genes and were resistant to at least one antibiotic. Antibiotic susceptibility studies revealed the presence of multidrug resistant Salmonella strains in coastal water, which usually from land base sources end up in the marine environment and may pose a significant risk on public health.

Prevalence of enteric non-typhoidal Salmonella in humans in the Middle East and North Africa: A systematic review and meta-analysis

To enhance efforts related to controlling foodborne pathogens in the Middle East and North Africa (MENA), information on epidemiology of non-typhoidal Salmonella enterica (hereafter termed "Salmonella") is limited. We quantified the overall regional and country-specific Salmonella prevalence in different human populations and identified the most common serotypes. Published literature of Salmonella prevalence was systematically reviewed and reported following the Preferred Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Pooled Salmonella prevalence measures were estimated using a random-effects model. We identified 46 research reports that reported 84 Salmonella prevalence measures in 15 out of 24 countries in MENA. There were 252,831 tested humans with 6,356 Salmonella-positive cases. The pooled Salmonella prevalence in MENA was estimated at 6.6% (95% confidence interval (CI): 5.4%-7.9%). The highest pooled Salmonella prevalence measures were in Morocco (17.9%, 95% CI: 5.7%-34.8%, 1997-2012), Tunisia (10.2%, 95% CI: 4.3%-18.0%, 1988-2009) and Sudan (9.2%, 95% CI: 6.5%-12.2%, 2006-2008), while the lowest were in Jordan (1.1%, 95% CI: 0.1%-3.0%, 1993-2010), Oman (1.2%, 95% CI: 1.2%-1.3%, 1998-2002) and Palestine (1.2%, 95% CI: 0.4%-2.1%, 1999-2011). In MENA, Salmonella pooled prevalence in gastrointestinal symptomatic, gastrointestinal asymptomatic and food handlers population groups was 13.0% (95% CI: 7.6%-19.6%), 11.4% (95% CI: 2.2%-25.7%) and 3.8% (95% CI: 1.0%-8.0%), respectively. Salmonella prevalence was 14.5% (95% CI: 8.7%-26.1%) in studies tested <100 subjects, whereas 4.6% (95% CI: 3.6%-5.8%) in studies tested ≥100 subjects. Salmonella Enteritidis (29.8%) and Typhimurium (23.6%) were the most common serotypes. Salmonella was a common foodborne pathogen in MENA countries, particularly in North African countries. Findings inform the scientific community, the public and the decision-makers with Salmonella prevalence and gaps in evidence in MENA to support control and prevention strategies and could leverage more research studies.

Childhood Diarrhoea in the Eastern Mediterranean Region with Special Emphasis on Non-Typhoidal Salmonella at the Human⁻Food Interface

Diarrhoeal disease is still one of the most challenging issues for health in many countries across the Eastern Mediterranean region (EMR), with infectious diarrhoea being an important cause of morbidity and mortality, especially in children under five years of age. However, the understanding of the aetiological spectrum and the burden of enteric pathogens involved in diarrhoeal disease in the EMR is incomplete. Non-typhoidal Salmonella (NTS), the focus of this review, is one of the most frequently reported bacterial aetiologies in diarrhoeal disease in the EMR. Strains of NTS with resistance to antimicrobial drugs are increasingly reported in both developed and developing countries. In the EMR, it is now widely accepted that many such resistant strains are zoonotic in origin and acquire their resistance in the food-animal host before onward transmission to humans through the food chain. Here, we review epidemiological and microbiological aspects of diarrhoeal diseases among children in the EMR, with emphasis on the implication and burden of NTS. We collate evidence from studies across the EMR on the zoonotic exposure and antimicrobial resistance in NTS at the interface between human and foods of animal origin. This review adds to our understanding of the global epidemiology of Salmonella with emphasis on the current situation in the EMR.

The Impact of Climate Change on Raw and Untreated Wastewater Use for Agriculture, Especially in Arid Regions: A Review

Climate change is one of the major challenges of our time that pose unprecedented stress to the environment and threats to human health. The global impacts of climate change are vast, spanning from extreme weather events to changes in patterns and distribution of infectious diseases. Lack of rainfall associated with higher temperatures has a direct influence on agricultural production. This is compounded by a growing population forecasted to expand further with increasing needs for food and water. All this has led to the increasing use of wastewater worldwide. In this review, we more specifically discuss the use of untreated wastewater in agriculture in the Middle East and North Africa (MENA) countries, the most arid region in the world. This presents challenges for agriculture with respect to water availability and increasing wastewater use in agri-food chain. This in turn exerts pressures on the safety of food raised from such irrigated crops. Current practices in the MENA region indicate that ineffective water resource management, lack of water quality policies, and slow-paced wastewater management strategies continue to contribute to a decline in water resources and an increased unplanned use of black and graywater in agriculture. Radical actions are needed in the region to improve water and wastewater management to adapt to these impacts. In this regard, the 2006 WHO guidelines for the use of wastewater contain recommendations for the most effective solutions. They provide a step-by-step guide for series of appropriate health protection measures for microbial reduction targets of 6 log units for viral, bacterial, and protozoan pathogens, but these need to be combined with new varieties of crops that are drought and pest resistant. More research into economic local treatment procedures for wastewater in the region is warranted.

Epidemiological Evidence and Health Risks Associated With Agricultural Reuse of Partially Treated and Untreated Wastewater: A Review

The use of partially treated and untreated wastewater for irrigation is beneficial in agriculture but may be associated with human health risks. Reports from different locations globally have linked microbial outbreaks with agricultural reuse of wastewater. This article reviews the epidemiological evidence and health risks associated with this practice, aiming toward evidence-based conclusions. Exposure pathways that were addressed in this review included those relevant to agricultural workers and their families, consumers of crops, and residents close to areas irrigated with wastewater (partially treated or untreated). A meta-analysis gave an overall odds ratio of 1.65 (95% CI: 1.31, 2.06) for diarrheal disease and 5.49 (95% CI: 2.49, 12.10) for helminth infections for exposed agricultural workers and family members. The risks were higher among children and immunocompromised individuals than in immunocompetent adults. Predominantly skin and intestinal infections were prevalent among individuals infected mainly via occupational exposure and ingestion. Food-borne outbreaks as a result of crops (fruits and vegetables) irrigated with partially or untreated wastewater have been widely reported. Contamination of crops with enteric viruses, fecal coliforms, and bacterial pathogens, parasites including soil-transmitted helminthes (STHs), as well as occurrence of antibiotic residues and antibiotic resistance genes (ARGs) have also been evidenced. The antibiotic residues and ARGs may get internalized in crops along with pathogens and may select for antibiotic resistance, exert ecotoxicity, and lead to bioaccumulation in aquatic organisms with high risk quotient (RQ). Appropriate mitigation lies in adhering to existing guidelines such as the World Health Organization wastewater reuse guidelines and to Sanitation Safety Plans (SSPs). Additionally, improvement in hygiene practices will also provide measures against adverse health impacts.

A Review on the Rising Prevalence of International Standards: Threats or Opportunities for the Agri-Food Produce Sector in Developing Countries, with a Focus on Examples from the MENA Region

Food safety standards are a necessity to protect consumers' health in today's growing global food trade. A number of studies have suggested safety standards can interrupt trade, bringing financial and technical burdens on small as well as large agri-food producers in developing countries. Other examples have shown that economical extension, key intermediaries, and funded initiatives have substantially enhanced the capacities of growers in some countries of the Middle East and North Africa (MENA) region to meet the food safety and quality requirements, and improve their access to international markets. These endeavors often compensate for the weak regulatory framework, but do not offer a sustainable solution. There is a big gap in the food safety level and control systems between countries in the MENA region and those in the developed nations. This certainly has implications for the safety of fresh produce and agricultural practices, which hinders any progress in their international food trade. To overcome the barriers of legal and private standards, food safety should be a national priority for sustainable agricultural development in the MENA countries. Local governments have a primary role in adopting the vision for developing and facilitating the implementation of their national Good Agricultural Practices (GAP) standards that are consistent with the international requirements and adapted to local policies and environment. Together, the public and private sector's support are instrumental to deliver the skills and infrastructure needed for leveraging the safety and quality level of the agri-food chain.

Health risks from exposure to untreated wastewater used for irrigation in the Mezquital Valley, Mexico: A 25-year update

Wastewater reuse for agriculture is common worldwide; wastewater treatment, however, is rare in many countries, leading to high potential for exposure to harmful pathogens. Mexico City, one of the largest producers of untreated wastewater for agricultural use worldwide, was the site of key epidemiologic studies conducted in the 1990s. We both reviewed the literature on and conducted a cross-sectional study of diarrheal risk and wastewater contamination to provide an updated assessment of health risks and to inform an upcoming update of the 2006 WHO guidelines on wastewater reuse. We surveyed communities in the Mezquital Valley that use wastewater for irrigation and communities that use well water to compare the prevalence of self-reported diarrheal disease in children under five years old. Wastewater, well water, household environmental samples, and stool samples were collected and analyzed. Communities exposed to wastewater had a higher one-week prevalence of diarrhea (10%) compared to unexposed communities (5%). This association remained in an adjusted modified Poisson regression model (PR = 2.31, 95% CI 1.00, 5.31), but not when limited to households engaged in agriculture. Water quality indicators document differences between irrigation water from the two community groups. These results are in agreement with 25 population studies identified by our review that were conducted since or not included in the 2006 WHO guidelines and show consistent negative impacts of wastewater exposure on health. While overall diarrheal prevalence has declined when compared to studies conducted over 25 years ago in the same region, the association of diarrheal disease and wastewater exposure has remained and possibly increased. With rising urbanization worldwide, attention to these risks and wastewater treatment is becoming increasingly important.

A Review of Health Risks and Pathways for Exposure to Wastewater Use in Agriculture

BACKGROUND

Wastewater is increasingly being used in the agricultural sector to cope with the depletion of freshwater resources as well as water stress linked to changing climate conditions. As wastewater irrigation expands, research focusing on the human health risks is critical because exposure to a range of contaminants must be weighed with the benefits to food security, nutrition and livelihoods.

OBJECTIVES

The goal of this paper was to review research examining health risks and exposure pathways associated with wastewater irrigation to identify research trends and gaps.

METHODS

We conducted a review of the literature and identified a total of 126 studies published from 1995 to 2013. Findings were summarized based on several themes including types of exposure pathways, wastewater contaminants, methodological approaches and the geographical distribution of research.

RESULTS

Only 23 studies used epidemiological methods, while most research applied alternative methods to estimate risk, such as quantitative risk assessment models or comparisons of crop contamination to established guidelines for wastewater reuse. A geographic breakdown demonstrated a focus on microbiological contaminants in specific regions such as sub-Saharan Africa and Southeast Asia, despite growing chemical risks associated with rapid urbanization and industrialization that may change the types and distribution of wastewater contaminants.

CONCLUSIONS

To provide a more comprehensive understanding of the health risks of wastewater use in agriculture, future research should consider multiple exposure routes, long-term health implications, and increase the range of contaminants studied, particularly in regions heavily dependent on wastewater irrigation.

CITATION

Dickin SK, Schuster-Wallace CJ, Qadir M, Pizzacalla K. 2016. A review of health risks and pathways for exposure to wastewater use in agriculture. Environ Health Perspect 124:900-909; http://dx.doi.org/10.1289/ehp.1509995.

Health effects of wastewater reuse for agriculture in the suburbs of Asmara city, Eritrea

The health impact of utilization of raw domestic sewage for vegetable cultivation in the suburbs of Asmara, Eritrea, was assessed. Results showed heavy contamination of vegetables by fecal coliforms and Giardia cysts as well as other pathogenic bacteria such as Shigella and Salmonella. Stool samples from 75 occupationally exposed farmers revealed that 45% of them were harboring Giardia cysts. Dietary intake of raw greens (lettuce, cabbage) grown on the raw sewage appears to cause giardiasis, amebiasis, and diarrhea in the farming community as well as in the surrounding area. Comparison of hospital data from the affected area with data from other areas of Eritrea indicated that agriculture use of untreated wastewater was the major cause of the increase in giardiasis and other gastrointestinal diseases.

Irrigation water as source of foodborne pathogens on fruit and vegetables

Awareness is growing that fresh or minimally processed fruit and vegetables can be sources of disease-causing bacteria, viruses, protozoa, and helminths. Irrigation with poor-quality water is one way that fruit and vegetables can become contaminated with foodborne pathogens. Groundwater, surface water, and human wastewater are commonly used for irrigation. The risk of disease transmission from pathogenic microorganisms present in irrigation water is influenced by the level of contamination; the persistence of pathogens in water, in soil, and on crops; and the route of exposure. Groundwater is generally of good microbial quality, unless it is contaminated with surface runoff; human wastewater is usually of very poor microbial quality and requires extensive treatment before it can be used safely to irrigate crops; surface water is of variable microbial quality. Bacteria and protozoa tend to show the poorest survival outside a human host, whereas viruses and helminths can remain infective for months to years. Guidelines governing irrigation water quality and strategies to reduce the risk of disease transmission by foodborne pathogens in irrigation are discussed.

Prevalence of Giardiasis due to wastewater reuse for agriculture in the suburbs of Asmara City, Eritrea

A study was undertaken to assess the health impact of utilization of the raw domestic sewage for vegetable cultivation in the suburbs of the capital city of Asmara, Eritrea. Standard techniques were adopted for the analysis of the samples. Results showed heavy contamination of vegetables by faecal coliforms as well as with Giardia cysts. Stool samples of 75 farmers who were occupationally exposed revealed that 45% of them were harbouring giardia cysts. The dietary intake of raw salads (lettuce, cabbage) grown on the raw sewage appear to be a causative factor of Giardiasis in the farming community as well as in the town of Tsadachristian located on the suburbs of the capital city of Asmara. The hospital data of the affected town is compared with other towns of Eritrea. The result indicates agriculture reuse of untreated wastewater is a major cause for the increase in Giardasis.

Solar inactivation of mesophilic Aeromonas by exogenous photooxidation in high-rate algal pond treating waste water

AIMS

Investigations were carried out to observe the effect of sunlight on the survival of mesophilic Aeromonas (A. caviae, A. hydrophila and A. sobria) in high-rate algal pond.

METHODS AND RESULTS

Light damage was estimated by loss of bacterial culturability, using simple beaker experiments. Survival of the strains studied under illuminated conditions was highly affected by the physico-chemical conditions within the microcosms. The inactivation of Aeromonas increased strongly as dissolved oxygen was increased, and was dependent on exogenous sensitizers. This process was enhanced by the high pH of water. Die-off of bacteria was prevented by adding catalase and pyruvate (H2O2 scavengers) into the microcosms.

CONCLUSIONS

The damage of Aeromonas was mainly due to exogenous photooxidation. Hydrogen peroxide at least was involved in light-induced damage of bacteria. Aeromonas sobria appeared to be slightly less sensitive to photooxidation than A. hydrophila and A. caviae.

SIGNIFICANCE AND IMPACT OF STUDY

The present study could explain the relative resistance of A. sobria to treatment in wastewater stabilization ponds.

Prevalence of Escherichia coli associated with a cabbage crop inadvertently irrigated with partially treated sewage wastewater

Preharvest contamination of field crops may have many sources, including feces, soil, and irrigation water. In March 2000, a sewage spill released unchlorinated tertiary-treated effluent into a creek used to irrigate commercial produce. A field of young cabbage transplants was irrigated with creek water as the contaminated water flowed past this land. Cabbage samples were taken from plots within this field, and Escherichia coli was isolated from the roots of these plants but not from the edible portion of the cabbage. No E. coli was isolated from water samples or from control samples taken from a nearby cabbage field watered with chlorinated municipal water. The cabbage field under study had not been fertilized with manure for at least 2 years prior to the contamination incident. Six different E. coli serotypes were identified, although none of them proved to be pathogenic. These serotypes were separated into five groups by a RiboPrinter; the resulting groups correlated well with the serotypes and the locations in the field from which these strains were isolated. We previously found that certain nonpathogenic E. coli strains displayed lower levels of adherence to lettuce seedling roots in a hydroponic adherence assay. The E. coli field strains displayed variable patterns of adherence to lettuce seedlings: strain MW421 showed significantly lower root and shoot adherence levels than did the other field strains, while strains MW423 and MW425 showed significantly higher root and shoot adherence levels. These data suggest that water quality is of paramount importance for the food safety of growing crops.