Outbreak of tick-borne encephalitis linked to raw milk cheese in France


France has identified its first outbreak of tick-borne encephalitis due to the consumption of raw dairy products, with more than 40 people affected.The infections are linked to the consumption of a brand of goat cheese with raw milk in the Ain, in the Rhône-Alpes region, between April and May this year, according to Public Health France.

The cheese producer is GAEC des Chevrettes du Vieux Valey, based in Condamine in Haut-Bugey, Ain. It is believed that ticks carrying the virus have contaminated a goat, then its milk, then cheeses, and finally consumers.

A total of 42 cases of lymphocytic meningitis, encephalitis and infectious syndromes have been identified in residents of the commune of Oyonnax, within a radius of 30 kilometers. Two more people live in Loire-Atlantique and the Jura but have consumed the raw milk goat cheese in question. Cases occurred between the week of April 13-19 and May 18-24 with a peak April 20-26.

Virus found in cheese
In late May, the diagnosis of tick-borne encephalitis virus (TBE), the agent responsible for tick-borne encephalitis, was confirmed for 33 of the 44 cases. The remaining 11 are under investigation and biological tests are underway to confirm or rule out the diagnosis of tick-borne encephalitis.

Among the confirmed cases, the median age is 49 years with the youngest patient 11 months old and the oldest 86 years old. Thirty people were hospitalized or hospitalized and two were admitted to intensive care.

Forty-one of 43 cases reported having raw milk cheese from the same producer in Ain from mid-April. The presence of the TBE virus was identified in a company goat cheese. The company’s dairy products were recalled before this result was known.

The producer started pasteurizing goat milk before processing. The products on sale at the time of the alert were withdrawn and recalled in late May.

A press release from the GAEC des Chevrettes du Vieux Valey indicates that the TBE virus transported by ticks was found on a single batch of cheeses produced on April 20 with negative controls on the most recent products, but it continues to eliminate the trafficked until authorities say it can restart sales. .

“We are awaiting the results of the blood tests on our goats to make sure that our animals are no longer carrying this virus. We also wish a speedy recovery to the victims of this virus and will keep you informed of the progress of the investigation concerning us, “said a statement from the owners of the farm.

Rare foodborne infections
The occurrence of sporadic cases of tick-borne encephalitis is not new in Auvergne-Rhône-Alpes with a few cases identified each year. A case was identified at the end of May 2020 in Ain in a person bitten several times by ticks but who did not eat the cheese.

Most virus infections result from infected ticks, which often remain attached to the skin for days. On rare occasions, the infection can result from the consumption of unpasteurized milk from infected goats, sheep or cows, according to the World Health Organization (WHO).

The incubation period for TBE is generally between 7 and 14 days. Symptoms at an early stage may include fever, malaise, anorexia, muscle pain, headache, nausea and / or vomiting. After an asymptomatic interval, a second phase of the disease occurs in some patients who may have symptoms of meningitis such as fever, headache, stiff neck and encephalitis (for example, drowsiness, confusion, sensory disturbances and / or abnormalities such as paralysis). The encephalitis that develops in this second phase can lead to paralysis, permanent health problems or death.

The severity of the disease increases with the age of the patient and there is no specific treatment for tick-borne encephalitis, according to the WHO.

The French Agency for Food, Environmental and Occupational Health Safety (ANSES) is carrying out additional environmental studies on ticks and the TBE virus in the geographic area concerned. Investigations are also underway, particularly among dairy farmers, as ticks carrying this virus may be present in other municipalities.

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