An Outbreak of Shiga toxin-producing E. coli Associated with Venison Processed at the Same Processing Facility May-June 2025

https://www.marlerblog.com/files/2025/08/TN25-058-Outbreak-Summary_Final_7.31.25_Redacted.pdf

Background

On May 12, 2025, the Tennessee Department of Health’s (TDH) Foodborne and Enteric Diseases (FED) Program received a report of Hemolytic Uremic Syndrome (HUS) and Shiga toxin-producing E. coli (STEC) O157:H7 in a 4-year-old female from Henry County, TN. The case’s isolate was sent to the Kentucky Division of Laboratory Services for whole genome sequencing (WGS), and her isolate was compared to others in the National Center for Biotechnology Information (NCBI). In NCBI, a case from Texas matched the Tennessee case by zero single-nucleotide polymorphisms (SNPs). Since these two cases were indistinguishable by WGS, TDH initiated an outbreak investigation.

Epidemiology

The TDH FED nurse consultant received the initial case report through routine HUS surveillance. She interviewed the case’s mother to collect demographic, clinical, and exposure information (e.g. food eaten, places traveled, etc.) in the 7 days before illness onset. The FED Nurse Consultant reviewed NCBI to identify additional cases and contacted the Texas Department of Health (TXDH) to obtain information on a Texas resident who matched the TN case by 0 SNPs.

A confirmed case was defined as a person with diarrheal illness and laboratory confirmed infection with the outbreak strain of STEC O157:H7 based on whole genome sequencing.

Environmental Health

The Tennessee Department of Agriculture (TDA) routine inspector for this facility and environmental health staff from TDH FED jointly performed a site visit at meat processing Facility L, which had processed venison consumed by both the Tennessee and Texas cases. The purpose of the site visit was to assess potential contributing factors that may have led to contamination of venison. During this visit, TDA performed a routine inspection and FED staff performed environmental sampling of the facilities and equipment used during venison processing.

FED staff also collected the remaining frozen venison from the Tennessee case’s home and delivered to the Tennessee State Public Health Laboratory (SPHL) for STEC testing.

Laboratory

Stool specimens were tested at the Kentucky Division of Laboratory Services for the Tennessee case and at the Texas Department of State Health Services Public Health Laboratory for the Texas case. The Tennessee case’s stool was tested on a GI molecular panel (QIAstat-Dx) at the hospital laboratory. The isolate was sent to Kentucky Division of Laboratory Services where stool culture and subsequent whole genome sequencing were performed. The Texas case’s stool was culture positive ElA at a commercial laboratory then forwarded to a local health department’s laboratory with PFGE performed and positive ElA resulted. The sample was then sent to Texas DSHS, culture confirmed and whole genome sequenced performed inhouse.

The TN SPHL tested 14 environmental swabs and processed venison meat samples using the FDA BAM method for STEC PCR a n d culture. A total of 23 packs of venison meat were received which included 17 ground meat, 5 backstrap, and 1 loin. To ensure all meat was tested, portions from two packs were pooled for testing, while the loin was tested separately. This strategy allowed for the testing of the entire 40 pounds of venison among 11 pooled ground meat and backstrap samples and 1 individual loin sample.

Epidemiology

The Tennessee case became ill on May 5, 2025, and symptoms included fever and hives. On May 7, 2025, she developed bloody diarrhea and was hospitalized at the Murray Calloway County Hospital in Murray, KY. A stool sample was collected on May 8, 2025, and tested positive for STEC O157:H7. On May 10, 2025, she was transferred to Vanderbilt Children’s Hospital in Nashville, TN and diagnosed with HUS. The case died at Vanderbilt Children’s Hospital on May 12, 2025.

The case’s mother was interviewed with a standard case report form on May 13, 2025. Exposures reported by the case’s mother included daycare, eating chicken at a fast food and a Mexican restaurant, contact with a family member who worked as a farrier on farms in Kentucky and Tennessee, contact with a horse and a donkey at home, private well at home, likely eating venison processed at Facility L in Puryear, TN, drinking unpasteurized goat’s milk provided by a private individual, and eating fresh strawberries, raspberries and mangoes purchased at Wal-Mart. The case’s mother reported local travel only for daycare (Benton, KY) and restaurants (Murray, KY and Paris, TN). No recreational water exposure was reported. The case’s mother reported she had diarrhea the week before the child’s illness, the case’s father reported vomiting the week before the child’s illness, and the case’s 11-month-old sibling had fever and one day of diarrhea the week before the child’s illness. None were reported to seek treatment or testing.

After finding the genetically related case in NCBI, TDH reached out to TXDH to see if the Texas case shared any common exposures. The Texas case’s illness onset was November 17, 2024. Symptoms experienced by the Texas case included bloody diarrhea, fever, vomiting, nausea, chills and abdominal pain. The Texas case visited the emergency room but was not hospitalized and did not develop HUS. The duration of illness was 15 days. The father stated the case, and her family traveled to Murray, KY, a week before her illness onset.

Other exposures shared between cases were either eating or having contact with deer processed at meat processing Facility L, family members who are farriers, and the Texas case and her family traveled to the same area of Kentucky where the Tennessee case resided.

Environmental Health

No immediate violations or practices that could have contributed to m e a t contamination were identified during the site visit. The facility employs 10 people and noted no facility issues during their venison processing period.

During deer season (end of October through early January), pork and beef processing is ceased at this facility to focus solely on venison. No venison is processed outside this window of time. When a deer is brought to the facility for custom meat processing, butchers on staff assess the deer visually to ensure the meat looks appropriate for processing (i.e., meat is appropriate color, no bugs). The deer is then field dressed (if not already done outside of the facility). brought inside, placed onto hooks, skinned, and offal removed prior to being placed in a walk-in blast cooler for at least 1-2 days at 32°F prior to further processing. The meat is then washed with a warm wash and sprayed with vinegar water before cooling again for 3-4 days at 35°F.

Following cooling, the meat is brought into the processing room where it is cut into steaks or ground prior to being packaged in vacuum sealed packages or sausage casings according to the customer’s preferences. Any spices used are pre-packaged from a commercial spice supplier. The meat is then labeled and placed into a walk-in freezer for at least 36 hours to fully freeze prior to notifying the customer to pick it up.

Each night, all equipment is disassembled, and the entire facility is cleaned by an independent cleaning service. No product is co-mingled other than in the machines – grinders and stuffers are not cleaned between individual deer.

Environmental samples were collected in each of the processing rooms in places that would have had contact with venison meat. Of note, sampling was done over 5 months since the last deer oF the 2024-2025 deer season was processed at the facility.

Laboratory

The Kentucky Division of Laboratory Services and the Texas Department of State Health Services Public Health Laboratory isolated STEC O157:H7 from the Tennessee and Texas cases, respectively. Whole genome sequencing results for the clinical STEC isolates indicated relatedness within 0-5 SNPs and 0 alleles by cgMLST. No other isolates were closely related to these two clinical isolates in the NCBI dendrogram.

Approximately 40 lbs. of frozen meat from one deer were collected from the Tennessee case’s home for testing. All samples were PCR and culture negative for STEC.

One environmental sample was PCR positive for STEC, but STEC was not isolated by culture. Without a cultured isolate, no WGS could be performed on this sample to see if it matched the outbreak strain of STEC O157:H7. This sample was collected from a hide pull that is used exclusively for venison. The chain, floor plate, bolts, and plate-chain attachment were swabbed

Discussion

This STEC )157:H7 outbreak had a suspected link to contact with deer processed at the Facility L in Puryear, TN. Whole genome sequences of the two human stool STEC O157:H7 isolates were identical, indicating a common exposure that was epidemiologically identified through case interviews. Other common exposures may have contributed to illness, including travel to similar areas of Kentucky and Tennessee, and family members of both cases who worked as farriers. However, investigators could not find any connection where the farriers would have worked with one another or had contact with similar people. Also, there were no common restaurants or events in Kentucky a n d Tennessee shared by the two cases seven days before their illness onset.

Furthermore, venison is a rare exposure among STEC cases in Tennessee, with approximately 2% of all STEC cases annually reporting contact with any wild game meat, including venison. The rarity of this shared exposure, combined with the link to a shared processing facility, contributed to a high level of suspicion of venison as the suspected source in this outbreak over other possible modes of transmission.

The literature reports outbreaks of O157:H7 linked to venison contact and consumption (Kenne al., 1997; Smith-Palmer et al., 2018; Laidler 2013). Shiga toxin-producing E. coli. can colonize in the gastrointestinal tract of ruminant animals such as cattle, goats and deer, and be shed in their feces. Deer, like other ruminant animals such as cattle and goats, can shed STEC in their stool without being ill. Transmission can occur to humans who have contact with the animal’s f e c e s or ingest foods contaminated with their feces.

The absence of STEC in venison from the Tennessee case’s household d o e s does not indicate that the venison was not contaminated. It is possible that the section of the deer that was contaminated was already consumed, or laboratory testing could not isolate the pathogen. Shiga toxin-producing E. coli was detected by PCR on a hide pull swab; however, STEC could not be isolated from this sample. Since STEC was not isolated, G S could not be performed to determine if it matched the outbreak strain. Shiga toxin-producing E. coli was not detected or identified in any venison samples or other environmental swabs from the production facility. This could have been due in part to the lag time between the two cases’ illness onset (November 2024 for the Texas case and May 2025 for the Tennessee case) and the fact that the facility was no longer processing deer for the season at the time of our investigation. Since no environmental samples were culture positive for STEC and no process breakdowns or issues of concern were identified at the facility, no additional public health control measures were implemented beyond the processes already in place.

Safe food handling practices, such as cooking venison steaks and roasts to 145°F and ground venison to 160°F, combined with safe handling during processing, are the best way to prevent STEC and other infections since deer can carry STEC and other bacteria without appearing ill. Young children, older adults, pregnant women, and those who are immunocompromised should not eat undercooked meats and should wash their hands with warm water and soap after being in contact with raw meats or ruminant animals, such as deer. Our investigation found that venison was the most likely common source of infection in this outbreak; however, this could not be confirmed by environmental sampling and testing.

References

Keene WE, Sazie E, Kok J, Rice DH, Hancock DD, Balan VK, Zhao T, Doyle MP. An outbreak of Escherichia coli O157:H7 infections traced to jerky made from deer meat. JAMA. 1997 Apr 16;277(15):1229-31. doi: 10.1001/jama. 1997.03540390059036. PMID: 9103348.

Smith-Palmer A, Hawkins G, Browning L, Allison L, Hanson M, Bruce R, McElhiney J, Horne J. Outbreak of Escherichia coli O157 Phage Type 32 linked to the consumption of venison products. Epidemiol Infect. 2018 Nov; 146(15):1922-1927. doi: 10.1017/S0950268818001784. Epub 2018 Jul 6. PMID: 29976259; PMCID: PMC6452997.

Laidler MR, Tourdjman M, Buser GL, Hostetler T, Repp KK, Leman R, Samadpour M, Keene WE. Escherichia coli O157:H7 infections associated with consumption of locally grown strawberries contaminated by deer. Clin Infect Dis. 2013 Oct;57(8): 1129-34. doi: 10.1093/cid/cit468. Epub 2013 Jul 21. PMID: 23876397.

Republished with permission from Bill Marler and Marler Clark. Copyright (c) Marler Clark LLP, PS. All rights reserved.

Source: https://www.marlerblog.com/case-news/an-outbreak-of-shiga-toxin-producing-e-coli-associated-with-venison-processed-at-the-same-processing-facility-may-june-2025/