A multi-state Salmonella Typhimurium outbreak associated with frozen vacuum-packed rodents used to feed snakes

A Case of Food-Borne Salmonellosis in a Corn Snake (Pantherophis guttatus) after a Feeder Mouse Meal

Reptiles are usually asymptomatic carriers of Salmonella, with the manifestation of typical clinical signs of acute forms in adult and non-immunocompromised animals being considered exceptions. In the present case, an adult male corn snake (Pantherophis guttatus) was found dead due to septic shock 48 h after consuming a feeder mouse purchased online. The snake's tissue samples and faeces were cultured for bacteria isolation. Microbiological examinations of the snake and mouse livers revealed the presence of Salmonella enterica subsp. enterica serovar Midway. A whole-genome analysis of these two isolates showed a high correlation between them: they belonged to the strain type ST-357 for the classic MLST scheme and to the strain type ST 171322 for the cgMLST scheme. Also, a virulence gene analysis revealed the presence of stdB and STM3026 genes. This report conveys a case of food-borne salmonellosis in a pet snake, transmitted from a feeder mouse, likely responsible for the snake's death due to septic shock. It highlights the relevance of feeder mice as a source of Salmonella infections in snakes and the associated risks to human health.

Zoonotic Pathogens Associated with Pet and Feeder Murid Rodent Species: A Global Systematic Review

Background: Pet and feeder rodents are one of the main sources of emerging infectious diseases. These rodents are purchased from pet shops, breeders, and online. Consequently, some of these rodents may subtly transmit diseases as they may be asymptomatic to certain pathogens. Materials and Methods: We systematically searched four academic databases viz. Google Scholar, PubMed, Web of Science, and Scopus to determine zoonotic pathogens associated with pet and feeder rodents globally. Our searches were performed in R statistical software using the packages "metagear" and "revtool". Results: We found 62 studies reporting on zoonotic pathogens between 1973 and 2022 from 16 countries representing 4 continents, namely Africa, Europe, Asia, and North America. The review identified 30 zoonotic pathogens isolated from pet and feeder rodents, including the African pygmy mouse (Mus minutoides), brown rat (Rattus norvegicus), and the house mouse (Mus musculus). The greatest number of pathogens was reported from the United States, followed by Togo and the United Kingdom. Bacterial pathogens were the most prevalent. However, the Seoul virus and rat bite fever (Streptobacillus moniliformis) were the most studied pathogens, found in more than one country, with reported outbreak cases. Most of the zoonotic pathogens were isolated from rodents acquired from pet shops. Conclusions: We recommend that pet and feeder rodents purchased from pet shops should be regularly screened for potential zoonotic pathogens as some of these animals may not show clinical signs of the illness. There is also a critical need to develop strict regulations and policies, especially in underdeveloped and developing regions for an effective surveillance process, which will include early detection, rapid response, and control of zoonotic diseases globally.

Salmonella in Captive Reptiles and Their Environment-Can We Tame the Dragon?

Reptiles are considered a reservoir of a variety of Salmonella (S.) serovars. Nevertheless, due to a lack of large-scale research, the importance of Reptilia as a Salmonella vector still remains not completely recognized. A total of 731 samples collected from reptiles and their environment were tested. The aim of the study was to assess the prevalence of Salmonella in exotic reptiles kept in Poland and to confirm Salmonella contamination of the environment after reptile exhibitions. The study included Salmonella isolation and identification, followed by epidemiological analysis of the antimicrobial resistance of the isolates. Implementation of a pathway additional to the standard Salmonella isolation protocol led to a 21% increase in the Salmonella serovars detection rate. The study showed a high occurrence of Salmonella, being the highest at 92.2% in snakes, followed by lizards (83.7%) and turtles (60.0%). The pathogen was also found in 81.2% of swabs taken from table and floor surfaces after reptile exhibitions and in two out of three egg samples. A total of 918 Salmonella strains belonging to 207 serovars and serological variants were obtained. We have noted the serovars considered important with respect to public health, i.e., S. Enteritidis, S. Typhimurium, and S. Kentucky. The study proves that exotic reptiles in Poland are a relevant reservoir of Salmonella.

Pet Reptiles: A Potential Source of Transmission of Multidrug-Resistant Salmonella

Salmonella spp. is widely considered one of the most important zoonotic pathogens worldwide. The close contact between reptiles and their owners provides favourable conditions for the transmission of zoonotic pathogen infections, and ~6% of human salmonellosis cases are acquired after direct or indirect contact with reptiles. Moreover, antimicrobial resistance is one of the most important health threats of the twenty-first century and has been reported in Salmonella strains isolated from pet reptiles, which could entail therapeutic consequences for their owners and breeders. The aim of this study was to assess Salmonella carriage by pet reptiles in pet shops and households, and their role in the transmission of antimicrobial resistance, to inform the owners about the possible risks factors. During the period between January 2019 and December 2019, 54 reptiles from pet shops and 69 reptiles from households were sampled in the Valencian Region (Eastern Spain). Three different sample types were collected from each reptile: oral cavity, skin, and cloacal swabs. Salmonella identification was based on ISO 6579-1:2017 (Annex D), serotyped in accordance with Kauffman-White-Le-Minor technique, and antibiotic susceptibility was assessed according to Decision 2013/652. The results of this study showed that 48% of the pet reptiles examined from households and pet shops carry Salmonella spp. All the strains isolated presented resistance to at least one antibiotic, and 72% were multidrug-resistant strains, the most frequently observed resistance patterns being gentamicin-colistin and gentamicin-colistin-ampicillin. The present study demonstrates that pet reptiles could be a source of human multidrug-resistant Salmonella infection. In this context, the most optimal prevention of multidrug-resistant Salmonella infections necessarily involves strict control of the sanitary status of reptile pet shops and hygienic handling by the individual owners at home.

The diversity, evolution and ecology of Salmonella in venomous snakes

BACKGROUND

Reptile-associated Salmonella bacteria are a major, but often neglected cause of both gastrointestinal and bloodstream infection in humans globally. The diversity of Salmonella enterica has not yet been determined in venomous snakes, however other ectothermic animals have been reported to carry a broad range of Salmonella bacteria. We investigated the prevalence and diversity of Salmonella in a collection of venomous snakes and non-venomous reptiles.

METHODOLOGY/PRINCIPLE FINDINGS

We used a combination of selective enrichment techniques to establish a unique dataset of reptilian isolates to study Salmonella enterica species-level evolution and ecology and used whole-genome sequencing to investigate the relatedness of phylogenetic groups. We observed that 91% of venomous snakes carried Salmonella, and found that a diverse range of serovars (n = 58) were carried by reptiles. The Salmonella serovars belonged to four of the six Salmonella enterica subspecies: diarizonae, enterica, houtanae and salamae. Subspecies enterica isolates were distributed among two distinct phylogenetic clusters, previously described as clade A (52%) and clade B (48%). We identified metabolic differences between S. diarizonae, S. enterica clade A and clade B involving growth on lactose, tartaric acid, dulcitol, myo-inositol and allantoin.

SIGNIFICANCE

We present the first whole genome-based comparative study of the Salmonella bacteria that colonise venomous and non-venomous reptiles and shed new light on Salmonella evolution. Venomous snakes examined in this study carried a broad range of Salmonella, including serovars which have been associated with disease in humans such as S. Enteritidis. The findings raise the possibility that venomous snakes could be a reservoir for Salmonella serovars associated with human salmonellosis.

Outbreak of Salmonella Typhimurium associated with feeder rodents

In December 2012, an increase in human Salmonella Typhimurium cases was identified in the province of Ontario, Canada launching an outbreak investigation. The outbreak spanned 3 years (2012-2014), with 134 cases reported from five Canadian provinces. There was a substantial burden of illness among children: 45% of cases were children 12 years old or under, and 23% of cases were under 5 years old. Epidemiologic, traceback and laboratory findings linked this outbreak to feeder rodents (used to feed snakes) supplied by a network of rodent breeders in Ontario. Cases likely acquired their illness through either direct or indirect contact with feeder rodents. This investigation not only contributes to the weight of evidence on the risk that feeder rodents pose, but also underscores the importance of investigating indirect animal contact and associated risks, especially for high-risk individuals.

Multilaboratory Survey To Evaluate Salmonella Prevalence in Diarrheic and Nondiarrheic Dogs and Cats in the United States between 2012 and 2014

Eleven laboratories collaborated to determine the periodic prevalence of Salmonella in a population of dogs and cats in the United States visiting veterinary clinics. Fecal samples (2,965) solicited from 11 geographically dispersed veterinary testing laboratories were collected in 36 states between January 2012 and April 2014 and tested using a harmonized method. The overall study prevalence of Salmonella in cats (3 of 542) was <1%. The prevalence in dogs (60 of 2,422) was 2.5%. Diarrhea was present in only 55% of positive dogs; however, 3.8% of the all diarrheic dogs were positive, compared with 1.8% of the nondiarrheic dogs. Salmonella-positive dogs were significantly more likely to have consumed raw food (P = 0.01), to have consumed probiotics (P = 0.002), or to have been given antibiotics (P = 0.01). Rural dogs were also more likely to be Salmonella positive than urban (P = 0.002) or suburban (P = 0.001) dogs. In the 67 isolates, 27 unique serovars were identified, with three dogs having two serovars present. Antimicrobial susceptibility testing of 66 isolates revealed that only four of the isolates were resistant to one or more antibiotics. Additional characterization of the 66 isolates was done using pulsed-field gel electrophoresis and whole-genome sequencing (WGS). Sequence data compared well to resistance phenotypic data and were submitted to the National Center for Biotechnology Information (NCBI). This study suggests an overall decline in prevalence of Salmonella-positive dogs and cats over the last decades and identifies consumption of raw food as a major risk factor for Salmonella infection. Of note is that almost half of the Salmonella-positive animals were clinically nondiarrheic.

A Multistate Investigation of Antibiotic-Resistant Salmonella enterica Serotype I 4,[5],12:i:- Infections as Part of an International Outbreak Associated with Frozen Feeder Rodents

While most human Salmonella infections result from exposure to contaminated foods, an estimated 11% of all Salmonella infections are attributed to animal exposures, including both direct animal handling and indirect exposures such as cleaning cages and handling contaminated pet food. This report describes the epidemiologic, environmental and laboratory investigations conducted in the United States as part of the response to an international outbreak of tetracycline-resistant Salmonella enterica serotype I 4,[5],12:i:- infections with over 500 illnesses occurring from 2008 to 2010. This investigation found that illness due to the outbreak strain was significantly associated with exposure to pet reptiles and frozen feeder rodents used as food for pet reptiles. Salmonella isolates indistinguishable from the outbreak strain were isolated from a frozen feeder mice-fed reptile owned by a case patient, as well as from frozen feeder mice and environmental samples collected from a rodent producing facility (Company A). An international voluntary recall of all Company A produced frozen feeder animals sold between May 2009 and July 2010 occurred. Only 13% of cases in our investigation were aware of the association between Salmonella infection and mice or rats. Consumers, the pet industry, healthcare providers and veterinarians need to be aware of the potential health risk posed by feeder rodents, whether live or frozen. Frozen feeder rodent producers, suppliers and distributors should follow the animal food labelling requirements as described in 21 CFR §501.5, and all packages of frozen feeder rodents should include safe handling instructions. Persons should wash their hands thoroughly with soap and water after handling live or frozen feeder rodents, as well as reptiles or anything in the area where the animals live. Continued opportunities exist for public health officials, the pet industry, veterinarians and consumers to work together to prevent salmonellosis associated with pet food, pets and other animals.

A longitudinal study of Salmonella from snakes used in a public outreach program

Snakes are considered to be a source of Salmonella infection for humans, but little is known about the actual serotype prevalence in healthy snakes over time. Twelve snakes involved in a public outreach program, representing seven different species, were tested weekly for shedding of Salmonella sp. over a period of 10 consecutive weeks. The snakes were housed in close proximity but in separate exhibits. Fresh fecal samples (when available) or cloacal swabs were cultured for Salmonella sp., and subsequent Salmonella isolates were serotyped. As representatives of the feed source, the feces of two mice and the intestines of one rat were cultured weekly. Fecal samples from 11 of the 12 snakes were positive for Salmonella at least once. Seven (58%) of 12 snakes were culture positive five times or more. The weekly prevalence of Salmonella shedding varied between 25% and 66%. Two or more different serotypes were isolated from nine snakes over time; however, a predominant serotype was generally isolated from each of these snakes. Altogether 15 different serotypes were identified. Serotypes of public health concern included Newport, Oranienburg, and Muenchen. Two samples from feeder rodents were positive for Salmonella. The results are consistent with previous studies showing high intestinal colonization rates with Salmonella sp. in snakes. Frequent and intermittent shedding of multiple serotypes was evident. Feeder rodents might serve as a source for intestinal colonization. Appropriate handling protocols should be implemented for all reptiles associated with public outreach programs to minimize risk of Salmonella transmission to the public.

Frequency of Detection of Escherichia coli, Salmonella spp., and Campylobacter spp. in the Faeces of Wild Rats (Rattus spp.) in Trinidad and Tobago

The study was conducted to determine the frequency of isolation of Salmonella, Campylobacter and E. coli O157 in the faecal samples of rats trapped across the regional corporations in Trinidad and to assess their resistance to antimicrobial agents. A total of 204 rats were trapped for the detection of selected bacteria. Standard methods were used to isolate Salmonella, Campylobacter and E. coli O157. Characterization of E. coli was done on sorbitol MacConkey agar to determine non-sorbitol fermentation, blood agar to determine haemolytic and mucoid colonies and by using E. coli O157 antiserum to determine O157 strain. The disc diffusion method was used to determine resistance to nine antimicrobial agents. Of the 204 rats, 4 (2.0%), 7 (3.4%) and 171 (83.8%) were positive for Salmonella spp., Campylobacter spp. and E. coli, respectively. Of the 171 isolates of E. coli tested 0 (0.0%), 25 (14.6%) and 19 (11.1%) were haemolytic, mucoid and non-sorbitol fermenters, respectively. All isolates were negative for the O157 strain. The frequency of resistance to the 9 antimicrobial agents tested was 75% (3 of 4) for Salmonella, 85.7% (6 of 7) of Campylobacter spp. and 36.3% (62 of 171) for E. coli (P < .05; χ(2)).

Animal contact as a source of human non-typhoidal salmonellosis

Non-typhoidal Salmonella represents an important human and animal pathogen world-wide. Most human salmonellosis cases are foodborne, but each year infections are also acquired through direct or indirect animal contact in homes, veterinary clinics, zoological gardens, farm environments or other public, professional or private settings. Clinically affected animals may exhibit a higher prevalence of shedding than apparently healthy animals, but both can shed Salmonella over long periods of time. In addition, environmental contamination and indirect transmission through contaminated food and water may complicate control efforts. The public health risk varies by animal species, age group, husbandry practice and health status, and certain human subpopulations are at a heightened risk of infection due to biological or behavioral risk factors. Some serotypes such as Salmonella Dublin are adapted to individual host species, while others, for instance Salmonella Typhimurium, readily infect a broad range of host species, but the potential implications for human health are currently unclear. Basic hygiene practices and the implementation of scientifically based management strategies can efficiently mitigate the risks associated with animal contacts. However, the general public is frequently unaware of the specific disease risks involved, and high-risk behaviors are common. Here we describe the epidemiology and serotype distribution of Salmonella in a variety of host species. In addition, we review our current understanding of the public health risks associated with different types of contacts between humans and animals in public, professional or private settings, and, where appropriate, discuss potential risk mitigation strategies.