Notes from the Field: Brucella abortus RB51 Infections Associated with Consumption of Raw Milk from Pennsylvania — 2017 and 2018

Joann F. Gruber, PhD1,2; Alexandra Newman, DVM3; Christina Egan, PhD3; Colin Campbell, DVM4; Kristin Garafalo, MPH4; David R. Wolfgang, VMD5; Andre Weltman, MD2; Kelly E. Kline, MPH2; Sharon M. Watkins, PhD2; Suelee Robbe-Austerman, DVM, PhD6; Christine Quance6; Tyler Thacker, PhD6; Grishma Kharod, MPH1; Maria E. Negron, DVM, PhD1; Betsy Schroeder, DVM2 (View author affiliations)

View suggested citation
Article Metrics
Altmetric:
Citations:
Views:

Views equals page views plus PDF downloads

Related Materials

In December 2018, the Pennsylvania Department of Agriculture (PDA) and Pennsylvania Department of Health (PADOH) were notified of a New York patient with brucellosis caused by infection with Brucella abortus RB51, the live attenuated vaccine strain of B. abortus used to prevent brucellosis in cattle (1). Brucellosis is a serious zoonotic infection caused by the bacteria Brucella spp. The most common sign is fever, followed by osteoarticular symptoms, sweating, and constitutional symptoms (2). Without proper treatment, infection can become chronic and potentially life-threatening (2). The patient had consumed raw (unpasteurized) milk from dairy A in Pennsylvania.* In July 2017, Texas health officials documented the first human case of domestically acquired RB51 infection associated with raw milk consumption from a Texas dairy (3). In October 2017, a second RB51 case associated with raw milk consumption was documented in New Jersey; the milk source was not identified at the time.

To determine the RB51 source for the New York case, PDA conducted an environmental investigation at dairy A in December 2018. PDA collected individual milk samples from all cows, excluding those known not to have been vaccinated against B. abortus, and from the bulk milk tank, which included milk pooled from all cows. All milk samples underwent polymerase chain reaction (PCR) testing and culture; whole-genome sequencing (WGS) was performed on patient and milk sample isolates. PDA conducted a traceback investigation of any cow with a milk sample that tested positive for RB51. PADOH worked with the raw milk cooperative that distributed dairy A’s milk to notify potentially exposed consumers and distributed notifications through Epi-X§ to identify cases.

Dairy A sold only raw milk and did not provide RB51 vaccination to cows born there (16 of the 30-cow herd). The remaining 14 cows were born outside the dairy and had inadequate vaccination records to determine whether they had received RB51. Because these cows might have been vaccinated, milk samples were collected from them. RB51 was detected by PCR and isolated in milk samples collected from the bulk tank and a single cow (cow 122). WGS identified two distinct RB51 strains shed by cow 122: one matched the 2018 New York patient’s isolate (3 single nucleotide polymorphisms [SNPs] different) and one, unexpectedly, matched the 2017 New Jersey patient’s isolate (1 SNP different). The two different RB51 strains were also shed from different quarters of cow 122’s udder.

Traceback revealed that cow 122 had received RB51 in 2011 and was purchased by dairy A in 2016. During 2016–2018, dairy A distributed raw milk potentially contaminated with RB51 to 19 states; PADOH notified those states’ public health veterinarians. PADOH provided a letter with RB51 information and brucellosis prophylaxis recommendations to the cooperative, which they distributed to dairy A customers. No additional cases were identified. Cow 122 was excluded from milk production, and serial PCR testing of bulk milk samples were subsequently negative for RB51.

Isolation of two different RB51 strains from different quarters of a cow’s udder has not previously been reported. These infections highlight the need to prevent RB51 infections. Raw milk consumption is also associated with serious illnesses caused by other pathogens, including Campylobacter spp., Shiga toxin–producing Escherichia coli, and Salmonella spp. (4). During 2007–2012, the number of raw milk outbreaks in the United States increased; 66 (81%) of 81 reported outbreaks occurred in states where raw milk sale is legal (5). Pregnant women, children, older adults, and persons with immunocompromising conditions are at greatest risk for infection.

To eliminate infection risk from milkborne pathogens, including RB51, all milk should be pasteurized. Because limited information is available about intermittent or continuous RB51 shedding among dairy cows, more research is needed to more fully understand this emerging public health threat for milk consumers. States can also consider the United States Animal Health Associations’ recommendations regarding the need for RB51 vaccination in areas where B. abortus is not endemic in wildlife.**

Corresponding author: Joann F. Gruber, okn2@cdc.gov, 717-787-3350.


1Epidemic Intelligence Service, CDC; 2Pennsylvania Department of Health; 3New York State Department of Health; 4New Jersey Department of Health; 5Pennsylvania Department of Agriculture; 6Animal and Plant Health Inspection Services, U.S. Department of Agriculture, Washington, DC.

All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed.


References

  1. Ragan VE; Animal and Plant Health Inspection Service. The Animal and Plant Health Inspection Service (APHIS) brucellosis eradication program in the United States. Vet Microbiol 2002;90:11–8. CrossRefexternal icon PubMedexternal icon
  2. Franco MP, Mulder M, Gilman RH, Smits HL. Human brucellosis. Lancet Infect Dis 2007;7:775–86. CrossRefexternal icon PubMedexternal icon
  3. Cossaboom CM, Kharod GA, Salzer JS, et al. Notes from the field: Brucella abortus vaccine strain RB51 infection and exposures associated with raw milk consumption—Wise County, Texas, 2017. MMWR Morb Mortal Wkly Rep 2018;67:286. CrossRefexternal icon PubMedexternal icon
  4. Langer AJ, Ayers T, Grass J, Lynch M, Angulo FJ, Mahon BE. Nonpasteurized dairy products, disease outbreaks, and state laws—United States, 1993-2006. Emerg Infect Dis 2012;18:385–91. CrossRefexternal icon PubMedexternal icon
  5. Mungai EA, Behravesh CB, Gould LH. Increased outbreaks associated with nonpasteurized milk, United States, 2007–2012. Emerg Infect Dis 2015;21:119–22. CrossRefexternal icon PubMedexternal icon

Suggested citation for this article: Gruber JF, Newman A, Egan C, et al. Notes from the Field: Brucella abortus RB51 Infections Associated with Consumption of Raw Milk from Pennsylvania — 2017 and 2018. MMWR Morb Mortal Wkly Rep 2020;69:482–483. DOI: http://dx.doi.org/10.15585/mmwr.mm6915a4external icon.

MMWR and Morbidity and Mortality Weekly Report are service marks of the U.S. Department of Health and Human Services.
Use of trade names and commercial sources is for identification only and does not imply endorsement by the U.S. Department of Health and Human Services.
References to non-CDC sites on the Internet are provided as a service to MMWR readers and do not constitute or imply endorsement of these organizations or their programs by CDC or the U.S. Department of Health and Human Services. CDC is not responsible for the content of pages found at these sites. URL addresses listed in MMWR were current as of the date of publication.

All HTML versions of MMWR articles are generated from final proofs through an automated process. This conversion might result in character translation or format errors in the HTML version. Users are referred to the electronic PDF version (https://www.cdc.gov/mmwr) and/or the original MMWR paper copy for printable versions of official text, figures, and tables.

Questions or messages regarding errors in formatting should be addressed to mmwrq@cdc.gov.

View Page In:pdf icon PDF [70K]
Page last reviewed: April 16, 2020