Raw goats’ milk outbreak investigated after 11 sickened

By Joseph James Whitworth

- Last updated on GMT

Positive results from a commercial laboratory were later found to be negative
Positive results from a commercial laboratory were later found to be negative

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An outbreak of Cryptosporidiosis from raw milk which sickened 11 people in Idaho highlights an infrequently reported risk, according to a report.

Raw goat milk produced on or after August 24 last year by Treasured Sunrise Acres in Parma was identified as the source of infections in two residents, said the Idaho Department of Health and Welfare's Division of Public Health (DPH).

Cryptosporidiosis, or Crypto, is a microscopic parasite causing a diarrheal illness.

The Centers for Disease Control and Prevention (CDC) blamed the increasing legal sales of raw milk for an increase in associated outbreaks  in a previous study.  

Milk produced before August 18, the date of illness onset, was unavailable for testing from retail stores, the household, or the dairy, said the Morbidity and Mortality Weekly (MMWR) report.

Negative test validation

Four samples from containers of raw goat milk produced on August 18, 21, 25, and 28 all tested positive for Cryptosporidium by real-time polymerase chain reaction (PCR) at a commercial laboratory.

Five samples were collected along the production line on September 2 and tested positive by PCR at the commercial laboratory.

Testing of all nine milk samples at CDC by PCR and direct fluorescent antibody test was negative.

CDC and the commercial laboratory validated the negative result by using sequencing to determine false-positive results were likely caused by goat DNA amplification during PCR.

An inspection of the dairy did not reveal any obvious contamination sources. Water from the producer's well tested negative at Idaho Bureau of Laboratories by direct fluorescent antibody test after ultrafiltration and goat stool was unavailable for testing.

Public Health Districts interviewed ill persons or their parents using a standardized questionnaire.

Outbreak investigation

Idaho's Southwest District Health (SWDH) and the Central District Health Department identified nine ill persons in four households.

Four had regularly consumed raw goat milk produced before August 18 and fell ill and five household members who had not experienced symptoms of gastroenteritis 3–8 days after the first household member became ill. 

In total, the 11 ill persons were aged two months to 76 years, six were female and one patient was hospitalized.

Stool specimens in three primary cases (i.e., illnesses in those who drank the raw goat milk) and three secondary cases (i.e., illness in contacts of those who drank the milk) led to CDC isolating Cryptosporidium parvum subtype IIaA16G3R1 from all six.

The last reported outbreak-associated illness was a secondary case dated September 3.

Milk consumed before illness onset was unavailable for testing and could have been subjected to a single, undetected contamination event, said the report. 

“This outbreak highlights an infrequently reported cryptosporidiosis risk from unpasteurized milk, the value of sequencing to validate PCR protocols, the utility of genotyping Cryptosporidium isolates for strengthening epidemiologic evidence, and the risk for secondary transmission of Cryptosporidium. 

“An increasing number of enteric outbreaks are associated with raw milk consumption.”

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