White spot syndrome virus (WSSV) is the most problematic pathogen in crustaceans. In this study, we investigated the horizontal transmission model of WSSV based on the correlation between the disease severity grade and viral shedding rate and determined the minimum infective dose of WSSV via the waterborne route. Intramuscular injection challenges at different doses and water temperatures revealed that the thresholds of viral shedding and mortality were G1 (3.1 × 103 copies/mg) and G2 (8.5 × 104 copies/mg), respectively. Furthermore, a positive linear correlation was observed between viral copies of pleopods and viral shedding rate (y = 0.7076x + 1.414; p < 0.001). Minimum infective doses of WSSV were determined via an immersion challenge. Infection was observed within 1, 3, and 7 d in 105-, 103-, and 101 copies/mL of seawater, respectively. In the cohabitation challenge, infection was observed within six days with viral loads of 101 to 102 copies/mL of seawater, which further increased in the recipient group. Our results indicate a positive correlation between disease severity grade and viral shedding rate of infected shrimp and suggest that the waterborne transmission of WSSV depends on the viral load and exposure period.

Human bocavirus (HBoV) has been recognized as one of the common pathogens which cause respiratory disease and acute gastroenteritis in children worldwide. Recently, our studies reported the detection of HBoV in children with acute gastroenteritis and in oysters in Thailand. However, studies on the presence of HBoV in environmental waters in Thailand have not yet been conducted. In this study, 126 environmental water samples collected from November 2016 to July 2018 were investigated. Detection of HBoV was based on amplification of the VP1/VP2 region of the HBoV genome by nested PCR followed by nucleotide sequencing and phylogenetic analysis. HBoV was detected in 34 out of 126 samples (27.0%). All four HBoV genotypes, HBoV1 to HBoV4, were detected. HBoV2 was the most frequently detected genotype (61.8%), followed by HBoV1 (23.5%), HBoV4 (8.8%), and HBoV3 (5.9%). The highest detection rate of HBoV was observed during the warmest months in Thailand: April 2017 and March 2018. Phylogenetic analysis of VP1/VP2 nucleotide sequences of HBoV genotypes revealed that all four of the genotypes detected in environmental waters were closely related to genotypes detected in patients with acute gastroenteritis, which had been reported previously in the same geographical area. This study reports the existence of multiple HBoV genotypes in environmental waters and provides evidence of a considerably high magnitude of HBoV contamination in these waters. These findings demonstrate the potential risk of waterborne transmission of HBoV to humans. IMPORTANCE Recently, we reported the detection of HBoV genotypes 1, 2, and 3 in pediatric patients with acute gastroenteritis, and the detection of HBoV1 and 2 in oysters in Thailand. In this study, we reported the detection of HBoV1, 2, 3, and 4 contamination in environmental waters within the same geographic area. Phylogenetic analysis demonstrated that the HBoV genotypes detected in environmental waters and in oysters were closely related to HBoV detected in patients. These findings imply that HBoV contamination in oysters and in environmental waters could be a potential sources of foodborne and waterborne transmission to humans.

As the world continues to cope with the COVID-19 pandemic, emerging evidence indicates that respiratory transmission may not the only pathway in which the virus can be spread. This review paper aims to summarize current knowledge surrounding possible fecal-oral transmission of SARS-CoV-2. It covers recent evidence of proliferation of SARS-CoV-2 in the gastrointestinal tract, as well as presence and persistence of SARS-CoV-2 in water, and suggested future directions. Research indicates that SARS-CoV-2 can actively replicate in the human gastrointestinal system and can subsequently be shed via feces. Several countries have reported SARS-CoV-2 RNA fractions in wastewater systems, and various factors such as temperature and presence of solids have been shown to affect the survival of the virus in water. The detection of RNA does not guarantee infectivity, as current methods such as RT-qPCR are not yet able to distinguish between infectious and non-infectious particles. More research is needed to determine survival time and potential infectivity, as well as to develop more accurate methods for detection and surveillance.

Cryptosporidium spp. is one of the prime agents of infectious diarrhea. Cryptosporidium spp. has been gaining awareness as a pathogen of public health importance in India and other developing countries. Owing to the nature of multiple transmission routes such as person-to-person, animal-to-person, waterborne and foodborne, the epidemiology of cryptosporidiosis in humans is not well known. A deeper understanding of the pathogenesis may lead to better diagnosis and better treatment of the condition. Asymptomatic human and animal transmission illustrates that the spread of infection through the environment is a more plausible explanation, waterborne transmission in particular. The disease burden is underestimated and its global impact is yet to be quantified due to the lack of country-specific estimates. Assessment of the disease itself has been crucial since the morphological indistinguishability, differences in distribution and transmission, and variations in the genotypes.

Foot-and-mouth disease (FMD) has not been reported in the U.S. since 1929. Recent outbreaks in previously FMD-free countries raise concerns about potential FMD introductions in the U.S. Mathematical modeling is the only tool for simulating infectious disease outbreaks in non-endemic territories. In the majority of prior studies, FMD virus (FMDv) transmission on-farm was modeled assuming homogenous animal mixing. This assumption is implausible for U.S. beef feedlots which are divided into multiple home-pens without contact between home-pens except fence line with contiguous home-pens and limited mixing in hospital pens. To project FMDv transmission and clinical manifestation in a feedlot, we developed a meta-population stochastic model reflecting the contact structure. Within a home-pen, the dynamics were represented assuming homogenous animal mixing by a modified SLIR (susceptible-latent-infectious-recovered) model with four additional compartments tracing cattle with subclinical or clinical FMD and infectious status. Virus transmission among home-pens occurred via cattle mixing in hospital-pen(s), cowboy pen rider movements between home-pens, airborne, and for contiguous home-pens fence-line and via shared water-troughs. We modeled feedlots with a one-time capacity of 4,000 (small), 12,000 (medium), and 24,000 (large) cattle. Common cattle demographics, feedlot layout, endemic infectious and non-infectious disease occurrence, and production management were reflected. Projected FMD-outbreak duration on a feedlot ranged from 49 to 82 days. Outbreak peak day (with maximum number of FMD clinical cattle) ranged from 24 (small) to 49 (large feedlot). Detection day was 4-12 post-FMD-introduction with projected 28, 9, or 4% of cattle already infected in a small, medium, or large feedlot, respectively. Depletion of susceptible cattle in a feedlot occurred by day 23-51 post-FMD-introduction. Parameter-value sensitivity analyses were performed for model outputs. Detection occurred sooner if there was a higher initial proportion of latent animals in the index home-pen. Shorter outbreaks were associated with a shorter latent period and higher bovine respiratory disease morbidity (impacting the in-hospital-pen cattle mixing occurrence). This first model of potential FMD dynamics on U.S. beef feedlots shows the importance of capturing within-feedlot cattle contact structure for projecting infectious disease dynamics. Our model provides a tool for evaluating FMD outbreak control strategies.

We assessed the potential contribution of hospitals to contaminations of wastewater by enteric protists, including Cryptosporidium spp., Giardia duodenalis, and Enterocytozoon bieneusi in raw wastewater. Wastewater samples were collected from storage tanks in two hospitals and one associated wastewater treatment plant in Shanghai, China, from March to November 2009. Enteric pathogens were detected and identified using PCR and DNA sequencing techniques. Among a total of 164 samples analyzed, 31 (18.9%), 45 (27.4%), and 122 (74.4%) were positive for Cryptosporidium spp., G. duodenalis, and E. bieneusi, respectively. Altogether, three Cryptosporidium species, four G. duodenalis assemblages, and 12 E. bieneusi genotypes were detected. Cryptosporidium hominis, G. duodenalis sub-assemblage AII, and E. bieneusi genotype D were the dominant ones in wastewater from both hospitals and the wastewater treatment plant. A similar distribution in genotypes of enteric pathogens was seen between samples from hospitals and the wastewater treatment plant, suggesting that humans are one of the major sources for these pathogens and hospitals are important contributors of enteric parasites in urban wastewater. Data from this study might be useful in the formulation of preventive measures against environmental contamination of waterborne pathogens.

BACKGROUND: Pseudomonas aeruginosa is a ubiquitous and important opportunistic pathogen in immunocompromised or critically ill patients. Nosocomial P. aeruginosa outbreaks have been associated with hospital water sources.
OBJECTIVE: To describe engineering interventions to minimize contamination of water outlets and the subsequent clinical impact.
METHODS: New tap outlets were fitted at selected outlets across the intensive care unit (ICU). Laboratory testing demonstrated that, following artificial contamination with P. aeruginosa, these taps could be effectively decontaminated using a thermal washer-disinfector. Water samples were collected weekly from new outlets on the ICU over an eight-month period and tested for the enumeration of P. aeruginosa via membrane filtration. Surveillance of P. aeruginosa from clinical specimens was routinely undertaken.
RESULTS: Prior to the interventions, water sampling on ICU indicated that 30% of the outlets were positive for P. aeruginosa at any one time, and whole genome sequencing data suggested at least 30% transmission from water to patient. Since their installation, weekly sampling of the new tap outlets has been negative for P. aeruginosa, and the number of P. aeruginosa clinical isolates has fallen by 50%.
CONCLUSIONS: Installation and maintenance of tap outlets free of P. aeruginosa can substantially reduce the number of P. aeruginosa clinical isolates in an ICU.

Mikrocytos mackini is an intracellular parasite of oysters and causative agent of Denman Island disease in Pacific oysters Crassostrea gigas. Although M. mackini has been investigated for decades, its natural mode of transmission, mechanism for host entry, and environmental stability are largely unknown. We explored these biological characteristics of M. mackini using a recently described quantitative PCR (qPCR) assay. We detected M. mackini in the flow-through tank water of experimentally infected oysters and during disease remission in host tissues following 6 wk of elevated water temperature. Waterborne exposure of oysters to M. mackini further confirmed the potential for extracellular seawater transmission of this parasite and also identified host gill to have the highest early and continued prevalence for M. mackini DNA compared to stomach, mantle, labial palps, or adductor muscle samples. However, infections following waterborne challenge were slow to develop despite a substantial exposure (>106 M. mackini l-1 for 24 h), and further investigation demonstrated that M. mackini occurrence and infectivity severely declined following extracellular seawater incubation of more than 24 h. This study demonstrates a potential for using qPCR to monitor M. mackini in wild or farmed oyster populations during periods of disease remission or from environmental seawater samples. This work also suggests that gill tissues may provide a primary site for waterborne entry and possibly shedding of M. mackini in oysters. Further, although extracellular seawater transmission of M. mackini was possible, poor environmental stability and infection efficiency likely restricts the geographic transmission of M. mackini between oysters in natural environs and may help to explain localized areas of infection.

BACKGROUND: Helicobacter pylori infection has been consistently associated with lack of access to clean water and proper sanitation, but no studies have demonstrated that the transmission of viable but nonculturable (VBNC) H. pylori can occur from drinking contaminated water. In this study, we used a laboratory mouse model to test whether waterborne VBNCH. pylori could cause gastric infection.
METHODS: We performed five mouse experiments to assess the infectivity of VBNCH. pylori in various exposure scenarios. VBNC viability was examined using Live/Dead staining and Biolog phenotype metabolism arrays. High doses of VBNCH. pylori in water were chosen to test the \"worst-case\" scenario for different periods of time. One experiment also investigated the infectious capabilities of VBNC SS1 using gavage. Further, immunocompromised mice were exposed to examine infectivity among potentially vulnerable groups. After exposure, mice were euthanized and their stomachs were examined for H. pylori infection using culture and PCR methodology.
RESULTS: VBNC cells were membrane intact and retained metabolic activity. Mice exposed to VBNCH. pylori via drinking water and gavage were not infected, despite the various exposure scenarios (immunocompromised, high doses) that might have permitted infection with VBNCH. pylori. The positive controls exposed to viable, culturable H. pylori did become infected.
CONCLUSIONS: While other studies that have used viable, culturable SS1 via gavage or drinking water exposures to successfully infect mice, in our study, waterborne VBNC SS1 failed to colonize mice under all test conditions. Future studies could examine different H. pylori strains in similar exposure scenarios to compare the relative infectivity of the VBNC vs the viable, culturable state, which would help inform future risk assessments of H. pylori in water.

BACKGROUND: Toxoplasma gondii is a zoonotic coccidian parasite causing morbidity and mortality. In Yemen, T. gondii infection has been reported among pregnant women seeking healthcare in the main cities. However, no data are available on the prevalence of T. gondii infection and its associated risk factors among pregnant women in the rural communities of the country. Thus, the present study aimed to determine the seroprevalence of T. gondii and identify its risk factors among pregnant women in the rural communities of Taiz governorate, Yemen.
METHODS: A total of 359 pregnant women living in the rural communities of Taiz governorate were enrolled in this study by house-to-house visits. Data were collected using a pre-designed questionnaire, and blood samples were collected and tested for the detection of anti- T. gondii IgM and IgG antibodies by enzyme-linked immunosorbent assay.
RESULTS: The prevalence of T. gondii infection among pregnant women in this study was 46.2% (166/359). Bivariate analysis identified the age of  ≥ 30 years (odds ratio [OR] = 1.7; 95% confidence interval [CI] = 1.09-2.65, P = 0.019) and unimproved water sources (OR = 2.2; 95% CI = 1.10-4.55, P = 0.023) as factors associated with T. gondii infection among pregnant women. The multivariable analysis, however, identified unimproved water sources as an independent risk factor (adjusted OR = 2.4; 95% CI = 1.16-5.0, P = 0.018) associated with T. gondii infection among pregnant women.
CONCLUSIONS: Pregnant women in the rural communities of Taiz, Yemen are at high risk of contracting T. gondii infection. Unimproved water sources (wells, water streams and water tanks) are significantly associated with T. gondii infection and should be considered in prevention and control strategies, especially among pregnant women.