Breakfast with Brucellosis

The following commentary does not necessarily reflect the views of AgWeb or Farm Journal. The opinions expressed below are the author's own.

I’ll have a glass of milk please, without the Brucella abortus if you don’t mind. Oh, and also leave out the tuberculosis, diphtheria, scarlet fever, salmonella, listeria, yersinia, campylobacter, Staphylococcus aureus and E. coli O157:H7.

By that, of course, I mean pasteurized milk – one of the most important innovations in the history of food safety. But that’s just me. Some consumers want their milk raw, or unpasteurized.

Generally, targeting agricultural products to address specific consumer-demand niches can provide opportunities for producers, as long as market prices support any associated increases in production costs. But in marketing raw milk, dairies can put themselves at significant risk.

That again became clear last week when the Centers for Disease Control and Prevention (CDC) and state health officials announced an investigation into potential exposures to Brucella abortus strain RB51 in 19 states, connected to consuming raw milk from Miller’s Biodiversity Farm in Quarryville, Pennsylvania. Milk samples from that farm tested positive for RB51, and animal-health officials have removed a cow that tested positive for RB51 from the milking herd.

Brucella RB51 is a live, weakened strain used in a vaccine to protect cows against a more severe form of Brucella infection. However, the CDC notes that sometimes cows vaccinated with RB51 vaccine can shed the bacteria in their milk, and people who drink raw milk from cows shedding RB51 can develop brucellosis. CDC also notes RB51 is resistant to rifampin, an antibiotic commonly used to prevent or treat brucellosis.

The National Institutes of Health (NIH) notes that unlike wild strains of B. abortus, RB51 does not stimulate an antibody response detectable by routine serological assays, requiring culture for confirmation.

To date, the CDC has confirmed one case of human RB51 infection brucellosis in New York, with an unknown number of people potentially by drinking the milk from this farm. As of January 22, 2019, investigators determined that people in 19 states bought or consumed raw milk from the implicated farm. The states are Alabama, California, Connecticut, Florida, Georgia, Iowa, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, South Carolina, and Virginia.

The CDC alert says people who consumed raw milk or raw milk products from this dairy farm since January 2016 may have been exposed and should talk to their physician. Anyone consuming the suspect milk within the last six months have increased risk for brucellosis, should receive antibiotic treatment and should monitor for possible symptoms for six months. Anyone who last drank raw milk from this dairy more than six months ago and have experienced but not treated brucellosis symptoms should see their doctor immediately for testing.

This is not the first case of brucellosis in humans associated with B. abortus, RB51 in raw milk. Two cases occurred in 2017 in New Jersey and Texas, which authorities traced to raw milk from an online retailer and a Texas farm.

Veterinarians can help advise dairy clients on the risks of marketing raw milk and regulations specific to their states. While those risks probably cannot be eliminated, management practices regarding farm sanitation, biosecurity and animal health, including vaccination protocols, can influence risk levels positively or negatively.

Read more about the risks of consuming raw milk from the CDC.

For more on brucellosis and other zoonotic diseases, see these articles on BovineVetOnline:

Prevent Zoonotic Diseases on Your Dairy Farm

One stop shop for 'One Health' approach to zoonotic threats

Brucellosis Vaccination: Still a Good Idea?