RESUMO
We assessed microbial safety and quality of raw fish sold in Singapore during 2015-2016 to complement epidemiologic findings for an outbreak of infection with group B Streptococcus serotype III sequence type (ST) 283 associated with raw fish consumption. Fish-associated group B Streptococcus ST283 strains included strains nearly identical (0-2 single-nucleotide polymorphisms) with the human outbreak strain, as well as strains in another distinct ST283 clade (57-71 single-nucleotide polymorphisms). Our investigations highlight the risk for contamination of freshwater fish (which are handled and distributed separately from saltwater fish sold as sashimi) and the need for improved hygienic handling of all fish for raw consumption. These results have led to updated policy and guidelines regarding the sale of ready-to-eat raw fish dishes in Singapore.
Assuntos
Surtos de Doenças , Peixes/microbiologia , Manipulação de Alimentos , Doenças Transmitidas por Alimentos/etiologia , Infecções Estreptocócicas/etiologia , Streptococcus agalactiae , Animais , Doenças Transmitidas por Alimentos/epidemiologia , Humanos , Filogenia , Restaurantes , Singapura/epidemiologia , Infecções Estreptocócicas/epidemiologia , Streptococcus agalactiae/genéticaRESUMO
BACKGROUND: As the preparation of salads involves extensive handling and the use of uncooked ingredients, they are particularly vulnerable to microbial contamination. This study aimed to determine the microbial safety and quality of pre-packed salads and salad bar ingredients sold in Singapore, so as to identify public health risks that could arise from consuming salads and to determine areas for improvement in the management of food safety. RESULTS: The most frequently encountered organism in pre-packed salad samples was B. cereus, particularly in pasta salads (33.3%, 10/30). The most commonly detected organism in salad bar ingredients was L. monocytogenes, in particular seafood ingredients (44.1%, 15/34), largely due to contaminated smoked salmon. Further investigation showed that 21.6% (37/171) of the pre-packed smoked salmon sold in supermarkets contained L. monocytogenes. Significantly higher prevalence of L. monocytogenes and higher Standard Plate Count were detected in smoked salmon at salad bars compared to pre-packed smoked salmon in supermarkets, which suggested multiplication of the organism as the products move down the supply chain. Further molecular analysis revealed that L. monocytogenes Sequence Type (ST) 2 and ST87 were present in a particular brand of pre-packed salmon products over a 4-year period, implying a potential persistent contamination problem at the manufacturing level. CONCLUSIONS: Our findings highlighted a need to improve manufacturing and retail hygiene processes as well as to educate vulnerable populations to avoid consuming food prone to L. monocytogenes contamination.
Assuntos
Contaminação de Alimentos/análise , Manipulação de Alimentos , Microbiologia de Alimentos , Listeria monocytogenes/isolamento & purificação , Salmão/microbiologia , Alimentos Marinhos/microbiologia , Verduras/microbiologia , Animais , Bacillus cereus/crescimento & desenvolvimento , Bacillus cereus/isolamento & purificação , Técnicas de Tipagem Bacteriana , Sequência de Bases , Campylobacter/crescimento & desenvolvimento , Campylobacter/isolamento & purificação , Contagem de Colônia Microbiana , DNA Bacteriano , Escherichia coli/enzimologia , Escherichia coli/crescimento & desenvolvimento , Escherichia coli/isolamento & purificação , Contaminação de Alimentos/prevenção & controle , Manipulação de Alimentos/métodos , Indústria Alimentícia/normas , Embalagem de Alimentos/métodos , Embalagem de Alimentos/normas , Qualidade dos Alimentos , Inocuidade dos Alimentos , Humanos , Higiene , Listeria monocytogenes/genética , Listeria monocytogenes/crescimento & desenvolvimento , Listeriose/microbiologia , Filogenia , Prevalência , Saúde Pública , Sorotipagem/métodos , Singapura , Staphylococcus aureus/isolamento & purificação , Vibrio/classificação , Vibrio/isolamento & purificação , beta-Lactamases/biossínteseRESUMO
BACKGROUND: Due to the absence of available therapeutics and good vaccines, vector control solutions are needed to mitigate the spread of dengue. Matings between male Aedes aegypti mosquitoes infected with the wAlbB strain of Wolbachia and wildtype females yield non-viable eggs. We evaluated the efficacy of releasing wAlbB-infected A aegypti male mosquitoes to suppress dengue incidence. METHODS: In this synthetic control study, we conducted large-scale field trials in Singapore involving release of wAlbB-infected A aegypti male mosquitoes for dengue control via vector population suppression, from epidemiological week (EW) 27, 2018, to EW 26, 2022. We selected two large towns (Yishun and Tampines) to adopt an expanding release strategy and two smaller towns (Bukit Batok and Choa Chu Kang) to adopt a targeted-release approach. Releases were conducted two times a week in high-rise public housing estates. All intervention and control locations practised the same baseline dengue control protocol. The main outcome was weekly dengue incidence rate caused by any dengue virus serotype. We used incidence data collected by the Singapore Ministry of Health to assess the efficacy of the interventions. To compare interventions, we used the synthetic control method to generate appropriate counterfactuals for the intervention towns using a weighted combination of 30 control towns between EW 1, 2014 and EW 26, 2022. FINDINGS: Our study comprised an at-risk population of 607 872 individuals living in intervention sites and 3 894 544 individuals living in control sites. Interventions demonstrated up to 77·28% (121/156, 95% CI 75·81-78·58) intervention efficacy despite incomplete coverage across all towns until EW 26, 2022. Intervention efficacies increased as release coverage increased across all intervention sites. Releases led to 2242 (95% CI 2092-2391) fewer cases per 100 000 people in intervention sites during the study period. Secondary analysis showed that these intervention effects were replicated across all age groups and both sexes for intervention sites. INTERPRETATION: Our results demonstrated the potential of Wolbachia-mediated incompatible insect technique for strengthening dengue control in tropical cities, where dengue burden is the greatest. FUNDING: Singapore Ministry of Finance, Ministry of Sustainability, and the National Environment Agency, and the Singapore National Robotics Program.
Assuntos
Aedes , Dengue , Controle de Mosquitos , Mosquitos Vetores , Wolbachia , Wolbachia/fisiologia , Dengue/prevenção & controle , Dengue/epidemiologia , Dengue/transmissão , Singapura/epidemiologia , Animais , Aedes/microbiologia , Aedes/virologia , Incidência , Feminino , Masculino , Controle de Mosquitos/métodos , Mosquitos Vetores/microbiologia , Mosquitos Vetores/virologia , Humanos , Vírus da Dengue , Controle Biológico de Vetores/métodosRESUMO
BACKGROUND: Matings between male Aedes aegypti mosquitoes infected with wAlbB strain of Wolbachia and wildtype females yield non-viable eggs. We evaluated the efficacy of releasing wAlbB-infected Ae. aegypti male mosquitoes to suppress dengue. METHODS: We specified the protocol of a two-arm cluster-randomized test-negative controlled trial (cRCT) and emulated it using a nationally representative test-negative/positive database of individuals reporting for febrile illness to any public hospital, general practitioner or polyclinic. We retrospectively built a cohort of individuals who reside in Wolbachia locations versus a comparator control group who do not reside in Wolbachia locations, using a nationally representative database of all individuals whom report for febrile illness and were tested for dengue at the Environmental Health Institute/hospital laboratories/commercial diagnostic laboratories, through general practitioner clinic, polyclinic or public/private hospital from EW1 2019-EW 262022. We emulated a constrained randomization protocol used in cRCTs to balance dengue risk between intervention and control arms in the pre-intervention period. We used the inverse-probability weighting approach to further balance the intervention and control groups using a battery of algorithmically selected sociodemographic, environmental and anthropogenic variables. Intention-to-treat analyses was conducted to estimate the risk reduction of dengue given Wolbachia exposure. RESULTS: Intention-to-treat analyses revealed that, compared with controls, Wolbachia releases for 3, 6, 12 or more months was associated to 47%(95%CI:25-69%), 44%(33-77%) and 61%(38-78%) protective efficacy against dengue, respectively. When exposed to 12 or more months of Wolbachia releases, protective efficacies ranged from 49%(13-72%) to 77%(60-94%) across years. The proportion of virologically confirmed dengue cases was lower overall in the intervention arm. Protective efficacies were found across all years, age and sex subgroups, with higher durations of Wolbachia exposure associated to greater risk reductions of dengue. CONCLUSION: Results demonstrated that Wolbachia-mediated sterility can strengthen dengue control in tropical cities, where dengue burden is the greatest.
RESUMO
BACKGROUND: Dengue is a severe environmental public health challenge in tropical and subtropical regions. In Singapore, decreasing seroprevalence and herd immunity due to successful vector control has paradoxically led to increased transmission potential of the dengue virus. We have previously demonstrated that incompatible insect technique coupled with sterile insect technique (IIT-SIT), which involves the release of X-ray-irradiated male Wolbachia-infected mosquitoes, reduced the Aedes aegypti population by 98% and dengue incidence by 88%. This novel vector control tool is expected to be able to complement current vector control to mitigate the increasing threat of dengue on a larger scale. We propose a multi-site protocol to study the efficacy of IIT-SIT at reducing dengue incidence. METHODS/DESIGN: The study is designed as a parallel, two-arm, non-blinded cluster-randomized (CR) controlled trial to be conducted in high-rise public housing estates in Singapore, an equatorial city-state. The aim is to determine whether large-scale deployment of male Wolbachia-infected Ae. aegypti mosquitoes can significantly reduce dengue incidence in intervention clusters. We will use the CR design, with the study area comprising 15 clusters with a total area of 10.9 km2, covering approximately 722,204 residents in 1713 apartment blocks. Eight clusters will be randomly selected to receive the intervention, while the other seven will serve as non-intervention clusters. Intervention efficacy will be estimated through two primary endpoints: (1) odds ratio of Wolbachia exposure distribution (i.e., probability of living in an intervention cluster) among laboratory-confirmed reported dengue cases compared to test-negative controls and (2) laboratory-confirmed reported dengue counts normalized by population size in intervention versus non-intervention clusters. DISCUSSION: This study will provide evidence from a multi-site, randomized controlled trial for the efficacy of IIT-SIT in reducing dengue incidence. The trial will provide valuable information to estimate intervention efficacy for this novel vector control approach and guide plans for integration into national vector control programs in dengue-endemic settings. TRIAL REGISTRATION: ClinicalTrials.gov, identifier: NCT05505682 . Registered on 16 August 2022. Retrospectively registered.
Assuntos
Aedes , Dengue , Wolbachia , Animais , Masculino , Humanos , Controle de Mosquitos/métodos , Dengue/epidemiologia , Dengue/prevenção & controle , Mosquitos Vetores , Incidência , Estudos Soroepidemiológicos , Singapura/epidemiologia , Ensaios Clínicos Controlados Aleatórios como AssuntoRESUMO
Hepatitis E virus (HEV) causes 20 million infections worldwide yearly, of which only about 3.3 million are symptomatic. In developed Asian countries, HEV strains detected in human sera and in food sources were genetically similar, suggesting that indigenous HEV infections may be largely food-borne. To assess the burden of hepatitis E in Singapore, we performed a seroepidemiologic study of the infection. Additionally, we carried out HEV genotyping on archived, residual HEV IgM-positive serum samples collected between 2014 and 2016 (n = 449), and on pig liver samples (n = 36) purchased from wet markets and supermarkets. Our study shows a rise in hepatitis E incidence (IgM) from 1.7 to 4.1 cases per 100,000 resident population from 2012 to 2016 and an increase in hepatitis E IgG positivity rate among residents from 14% in 2007 to 35% in 2016. Other findings also suggest the epidemiology of hepatitis E in Singapore has shifted, from it being mainly a disease imported from the Indian subcontinent, to one that is now increasingly prevalent in our resident population. Genotypes obtained from 143 human samples identified the majority to be genotype 3 (n = 121), 21 to be genotype 1 and one to be genotype 4. Further phylogenetic analyses suggest genotype 3a to be the cause of indigenous infections in residents, which showed genetic similarity to the genotype 3a strains detected in pig livers. This link between the strains in the majority of human samples and those in pig livers consumed by the public suggests a possible food-borne route of HEV infection in Singapore.