ABSTRACT
OBJECTIVE: Although amphibians are known Salmonella carriers, no such outbreaks have been reported. We investigated a nationwide outbreak of human Salmonella Typhimurium infections occurring predominantly among children from 2008 to 2011. METHODS: We conducted a matched case-control study. Cases were defined as persons with Salmonella Typhimurium infection yielding an isolate indistinguishable from the outbreak strain. Controls were persons with recent infection with Salmonella strains other than the outbreak strain and matched to cases by age and geography. Environmental samples were obtained from patients' homes; traceback investigations were conducted. RESULTS: We identified 376 cases from 44 states from January 1, 2008, to December 31, 2011; 29% (56/193) of patients were hospitalized and none died. Median patient age was 5 years (range <1-86 years); 69% were children <10 years old (253/367). Among 114 patients interviewed, 69 (61%) reported frog exposure. Of patients who knew frog type, 79% (44/56) reported African dwarf frogs (ADF), a type of aquatic frog. Among 18 cases and 29 controls, illness was significantly associated with frog exposure (67% cases versus 3% controls, matched odds ratio 12.4, 95% confidence interval 1.9-infinity). Environmental samples from aquariums containing ADFs in 8 patients' homes, 2 ADF distributors, and a day care center yielded isolates indistinguishable from the outbreak strain. Traceback investigations of ADFs from patient purchases converged to a common ADF breeding facility. Environmental samples from the breeding facility yielded the outbreak strain. CONCLUSIONS: ADFs were the source of this nationwide pediatric predominant outbreak. Pediatricians should routinely inquire about pet ownership and advise families about illness risks associated with animals.
Subject(s)
Contact Tracing , Disease Outbreaks , Disease Vectors , Pets/microbiology , Pipidae/microbiology , Salmonella Infections/epidemiology , Salmonella typhimurium/isolation & purification , Adolescent , Adult , Aged , Aged, 80 and over , Animals , Case-Control Studies , Child , Child, Preschool , Female , Humans , Infant , Logistic Models , Male , Middle Aged , Multivariate Analysis , Retrospective Studies , Salmonella Infections/diagnosis , Salmonella Infections/transmission , United States/epidemiology , Young AdultABSTRACT
In the United States, the detection of paralytic shellfish poisoning (PSP) for regulatory purposes relies on the mouse bioassay (MBA). Using a saxitoxin presence/absence test could reduce animal usage significantly. Three in vitro methods, the RIDASCREEN Saxitoxin kit, MIST Alert, and a 5 h neuroblastoma assay, were evaluated in parallel with the MBA using 106 twice-frozen, acidified extracts from California-grown mussel and oyster tissues. For each assay, a cutoff point was established whereby data below or equal to that point were scored as negative and were assigned a score of zero. Data above the cutoff were considered positive and assigned a score of one. Pearson correlation coefficients were generated. The RIDASCREEN, MIST Alert, and neuroblastoma bioassay correlated to the MBA at 0.849, 0.853, and 0.832 when used for presence/absence detection. These data suggest that a reduction in MBA usage could be achieved in the surveillance of California-grown mussels and oysters for PSP-associated toxins. Correlation data between the in vitro assays, cost comparisons, and the potential for false negatives and false positives were examined. Implications of these methodologies in protecting public health are discussed.
