2016 Salmonella Outbreak Linked to Contact with Dairy Calves

• Read the Advice to Calf Handlers »
• Read the Advice to Veterinarians »
• Read the Information for Health Care Providers »
• Since the last update on August 2, 2017, eight more ill people have been reported from six states.
• CDC, several states, and the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (USDA-APHIS) are investigating a multistate outbreak of multidrug-resistant Salmonella Heidelberg infections.
• A total of 54 people infected with the outbreak strains of Salmonella Heidelberg have been reported from 15 states.
  • Seventeen (35%) people have been hospitalized. No deaths have been reported.
  • Illnesses started on dates ranging from January 27, 2015 to October 15, 2017.
  • Eighteen (33%) people in this outbreak are children under the age of 5.
• Epidemiologic and laboratory investigations linked ill people in this outbreak to contact with calves, including dairy calves.
  • In interviews, ill people answered questions about contact with animals and foods eaten in the week before becoming ill. Of the 54 people interviewed, 34 (63%) reported contact with dairy calves or other cattle. Some of the ill people interviewed reported that they became sick after their dairy calves became sick or died.
  • Ongoing surveillance in veterinary diagnostic laboratories showed that calves in several states continue to get sick with the outbreak strains of multidrug resistant Salmonella Heidelberg. ‎
  • Information collected earlier in the outbreak indicated that most of the calves came from Wisconsin. Regulatory officials in several states are now tracing the origin of the calves that are linked to the newer illnesses.
• Antibiotic resistance testing conducted by CDC on clinical isolates from ill people shows that the isolates were resistant to multiple types of antibiotics.

• Antibiotic resistance may be associated with increased risk of hospitalization, development of a bloodstream infection, or treatment failure in patients.
• Whole genome sequencing has identified multiple antimicrobial resistance genes in outbreak-associated isolates from 43 ill people, 87 isolates from cattle, and 11 isolates from animal environments.
• These findings match results from standard antibiotic resistance testing methods used by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) laboratory on clinical isolates from eight ill people in this outbreak.
• All eight isolates from ill people were resistant to amoxicillin-clavulanic acid, ampicillin, cefoxitin, ceftriaxone, streptomycin, sulfisoxazole, and tetracycline, and had reduced susceptibility to ciprofloxacin. Seven isolates were also resistant to trimethoprim-sulfamethoxazole. Five were also resistant to nalidixic acid. Three were also resistant to chloramphenicol. All eight isolates tested were susceptible to azithromycin and meropenem.
• Follow these steps to prevent illness when working with any livestock:
  • Always wash your hands thoroughly with soap and water right after touching livestock, equipment, or anything in the area where animals live and roam. Use dedicated clothes, shoes, and work gloves when working with livestock. Keep and store these items outside of your home.
  • It is especially important to follow these steps if there are children under age 5 in your household. Young children are more likely to get a Salmonella infection because their immune systems are still developing.
  • Work with your veterinarian to keep your animals healthy and prevent diseases.
• This investigation is ongoing and we will provide updates as more information becomes available. Livestock owners should continue to watch for increased sicknesses in dairy calves and consult their veterinarian if needed.

• Read the Advice to Calf Handlers and Veterinarians »
• Read the Information for Health Care Providers »
• CDC, several states, and the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (USDA-APHIS) are reopening the investigation of a multistate outbreak of multidrug-resistant Salmonella Heidelberg infections.
• Ten more people infected with the outbreak strains of Salmonella Heidelberg have been reported since March 20, 2017, when CDC closed the outbreak investigation.
  • Whole genome sequencing on clinical samples from ill people showed a close genetic relationship between the bacteria that sickened people after March 20, 2017, and the bacteria that sickened people before that time. This means that people in both groups were more likely to share a common source of infection and that this outbreak is ongoing.
• A total of 46 people infected with the outbreak strains of Salmonella Heidelberg have been reported from 14 states.
  • 14 (30%) people have been hospitalized. No deaths have been reported.
  • Illnesses started on dates ranging from January 27, 2015 to July 11, 2017.
  • 15 (33%) people in this outbreak are children under the age of 5.
• Epidemiologic and laboratory investigations linked ill people in this outbreak to contact with calves, including dairy bull calves. Dairy bull calves are young, male cattle that may be raised for meat.
  • In interviews, ill people answered questions about contact with animals and foods eaten in the week before becoming ill. Of the 44 people interviewed, 29 (66%) reported contact with dairy bull calves or other cattle. Some of the ill people interviewed reported that they became sick after their dairy bull calves became sick or died.
  • Ongoing surveillance in veterinary diagnostic laboratories showed that calves in several states continued to get sick with the outbreak strain of multidrug resistant Salmonella Heidelberg after reports of illnesses in people had stopped. ‎
  • Information collected earlier in the outbreak indicated that most of the calves came from Wisconsin. Regulatory officials in several states are now tracing the origin of the calves that are linked to the newer illnesses.
• Antibiotic-resistance testing conducted by CDC on clinical isolates from ill people shows that the isolates were resistant to multiple types of antibiotics.
  • Antibiotic resistance may be associated with increased risk of hospitalization, development of a bloodstream infection, or treatment failure in patients.
  • Whole genome sequencing has identified multiple antimicrobial resistance genes in outbreak-associated isolates from 33 ill people, 65 cattle, and 11 from animal environments. This correlates with results from standard antibiotic resistance testing methods used by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) laboratory on clinical isolates from eight ill people in this outbreak.
  • The eight isolates tested were susceptible to gentamicin, azithromycin, and meropenem. All eight were resistant to amoxicillin-clavulanic acid, ampicillin, cefoxitin, ceftriaxone, streptomycin, sulfisoxazole, and tetracycline, and had reduced susceptibility to ciprofloxacin. Seven isolates were also resistant to trimethoprim-sulfamethoxazole. Five were also resistant to nalidixic acid. Three were also resistant to chloramphenicol.
• Follow these steps to prevent illness when working with any livestock:
  • Always wash your hands thoroughly with soap and water right after touching livestock, equipment, or anything in the area where animals live and roam. Use dedicated clothes, shoes, and work gloves when working with livestock. Keep and store these items outside of your home.
  • It is especially important to follow these steps if there are children under age 5 in your household. Young children are more likely to get a Salmonella infection because their immune systems are still developing.
  • Work with your veterinarian to keep your animals healthy and prevent diseases.
• This investigation is ongoing and we will provide updates as more information becomes available. Livestock owners should continue to watch for increased sicknesses in dairy calves and consult their veterinarian if needed.

Advice for Livestock Handlers

This outbreak is a reminder to use a One Health approach to preventing illness, which recognizes that the health of people is connected to the health of animals and the environment. Follow these steps prevent illness when handling any livestock, like dairy calves:

• Always wash hands thoroughly with soap and water right after touching livestock, equipment for animals, or anything in the area where animals live and roam.
  • This is especially important to do before preparing or consuming food or drink for yourself or others.
  • Adults should supervise hand washing for young children.
  • Use hand sanitizer if soap and water are not available right away.
• Use dedicated shoes, work gloves, and clothing that you only use when working with livestock. Keep these items outside of your home.
  • Do not eat or drink in the areas where livestock live and roam.
  • Do not allow toys, pacifiers, spill-proof cups, baby bottles, strollers, or similar items in livestock areas.
  • Wash hands after removing any clothes and shoes you wore while working with livestock.
• Work with your veterinarian to keep your livestock healthy.
  • If you think your livestock are sick, talk to your veterinarian as soon as possible and take extra care to wash your hands after working with the animals and use separate clothes when caring for them.
  • Children, adults over age 65, and people with compromised immune systems should limit their contact with sick animals.

Advice for Veterinarians

• If veterinarians recognize ill dairy calves with laboratory-confirmed Salmonella Heidelberg, they should report the illness to their State Animal Health Official.
  • Laboratory testing, to include antimicrobial susceptibility testing, is recommended among dairy calves diagnosed with Salmonella Heidelberg, especially those associated with human illness.
  • A list of State Animal Health Officials can be found here. [PDF – 15 pages]
• If you suspect that a calf has a Salmonella infection, collect a fecal sample and submit it to a state or university veterinary diagnostic laboratory for culturing and pulsed-field gel electrophoresis (PFGE) testing.
  • For testing, the American Association of Veterinary Laboratory Diagnosticians (AAVLD) recommends submitting fecal samples to a state or university veterinary diagnostic laboratory for Salmonella culturing and PFGE.
  • If the laboratory isolates Salmonella but cannot perform PFGE, the isolate may be forwarded to a laboratory that can perform the procedure.  This may be one of the AAVLD labs in your area. To locate an AAVLD laboratory in your area, go to AAVLD Accredited Labs, or go to the AAVLD’s home page and click on the “Accreditation” link on the top menu bar.
  • Isolates may also be sent to USDA National Veterinary Services Laboratories (NVSL). To submit isolates to NVSL, complete Form VS 10-3 indicating whether serotyping, PFGE, or both are requested.
• Talk to your clients about reducing the risk of transmission of Salmonella illness from cattle to their family.
  • Be sure to tell clients that Salmonella infections are a zoonotic disease, meaning that the infection can spread between animals and people. If the client or any of their family members are ill, encourage them to contact a health care provider immediately.
  • Direct clients to the Advice for Livestock Handlers above.

Information for Health Care Providers

Salmonella bacteria live in the intestinal tracts of animals, including cattle. Cattle may become ill from Salmonella, but usually have no signs of illness. Young calves are more susceptible to being ill. The primary mode of transmission to humans is fecal-oral and is associated with contact with animals or their environments.

Clinicians should consider multidrug-resistant (MDR) Salmonella Heidelberg infection in the differential diagnosis of patients with exposure to cattle, farms, or farm workers and symptoms compatible with salmonellosis (e.g., diarrhea, fever, and abdominal cramps).

Guidance for clinicians whose patients have suspected or confirmed Salmonella Heidelberg infection related to this outbreak:

• Testing
  • Obtain a culture (stool or blood, as indicated by symptoms and signs).
  • Request antimicrobial susceptibility testing.
• Treatment
  • Most patients with nontyphoidal Salmonella do not require antibiotic treatment (exceptions may include patients <6 months, >50 years, and those who are immunocompromised or severely ill; please refer to treatment guidelines for additional information).
    • If treatment is indicated and MDR Salmonella Heidelberg infection is suspected, clinicians should begin treatment with azithromycin until susceptibility results of the patient’s isolate are available.
• Follow up
  • Obtain follow-up stool cultures for patients who have culture-confirmed MDR Salmonella Heidelberg and who are:
    • Food handlers
    • Health care workers
    • Childcare workers or attendees
• Patient counseling
  • Counsel patients to follow prevention practices. Key messages for counseling patients with salmonellosis:
    • Wash hands carefully with soap after going to the bathroom.
    • Don’t prepare food for others while ill. After you recover, wash hands carefully with soap before preparing food for others.
  • Before returning to work or childcare, these patients should have two consecutive negative stool cultures taken at least 24 hours apart and at least 48 hours after resolution of symptoms.