Salmonella prevalence and serovar distribution in reptiles: a systematic review and meta-analysis

Reptiles are recognized as reservoirs of Salmonella bacteria, and the expansion of the global pet reptile trade has led to reptile-associated salmonellosis emerging as a significant public health concern. To characterize the risk posed by reptiles as a source of Salmonella transmission to humans, we conducted the first comprehensive meta-analysis to estimate the worldwide prevalence of Salmonella in both wild and captive reptiles and identify the primary factors influencing this prevalence.

We systematically reviewed publications reporting the prevalence of Salmonella spp. intestinal isolation in reptiles, published between 1986 and 2023, across the PubMed, Scopus and Web of Science databases. The 179 studies included examined a total of 23,411 reptiles from 56 countries across all continents, with 49.9% being free-ranging animals and 48.4% living in captivity, mainly from zoos, pet shops, or households. The overall pooled prevalence of Salmonella spp. in reptiles was estimated at 30.4% (95% confidence interval, CI: 27.4-33.6%). Notably, significant variations in Salmonella spp. colonization rates were observed across different reptile taxa, with snakes exhibiting the highest prevalence at 63.1% (95%CI: 57.4-68.4%), followed by lizards at 33.6% (95%CI: 28.6-39.0%), and turtles and crocodiles with similar rates of 11.2% (95%CI: 8.8-14.2%) and 10.5% (95%CI: 5.7-18.6%), respectively. Furthermore, significant differences in Salmonella spp. prevalence were observed across different reptile families within each taxon. The data suggest that captivity is a contributing factor to Salmonella spp. colonization, as captive reptiles showed significantly higher prevalence rates (37.8%, 95%CI: 34.3-41.4%) compared to their wild counterparts (14.8%, 95%CI: 11.0-19.6%). Additionally, we found that the inclusion of pre-enrichment and selective enrichment steps in culture broths significantly improved the sensitivity of both culture-based and PCR-based Salmonella detection methods. Importantly, the study revealed that reptiles primarily carried Salmonella enterica subspecies enterica, responsible for most human salmonellosis cases. Of particular concern, several human-pathogenic Salmonella serovars of public health relevance, such as Enteritidis, Typhimurium and Newport, were identified among the 10 most common serovars colonizing reptiles.

Collectively, these findings highlight the substantial health threat posed by reptiles as a source of human Salmonella infection and may inform the development of policies and strategies for prevention and public education to mitigate the risk of reptile-associated salmonellosis.