Abstract
The tick-borne flaviviruses (TBFV) occur worldwide and the tick-borne encephalitis virus (TBEV) members of the group often cause severe, debilitating neurological disease in humans. Although the primary route of infection is through the bite of an infected tick, alimentary infection through the consumption of TBEV-contaminated dairy products is also well-documented and is responsible for some disease in endemic areas. Experimental infection of goats, cattle, and sheep with TBEV shows that the virus can be excreted in the milk of infected animals. Additionally, the virus remains infectious after exposure to low pH levels, similar to those found in the stomach. To evaluate the survival of virus in milk, we studied the stability of the BSL-2 TBFV, Langat virus, in unpasteurized goat milk over time and after different thermal treatments. Virus was stable in milk maintained under refrigeration conditions; however, there was a marked reduction in virus titer after incubation at room temperature. High temperature, short time pasteurization protocols completely inactivated the virus. Interestingly, simulation of a typical thermal regime utilized for cheese did not completely inactivate the virus in milk. These findings stress the importance of proper milk handling and pasteurization processes in areas endemic for TBEV.
Highlights
The tick-borne encephalitis virus (TBEV) group of tick-borne flaviviruses (TBFV) are pathogenic members of the Flaviviridae family
Fresh, unpasteurized goat milk was obtained from a local goat breeder and, along with complete DMEM, was added to a final concentration of 106 ffu/ml Langat virus (LGTV) TP21 in quintuplicate 1 ml aliquots
When LGTV in DMEM was incubated at 4°C, there was an approximate 0.5 log10 decrease over the 72-h period (Figure 1A)
Summary
The tick-borne encephalitis virus (TBEV) group of tick-borne flaviviruses (TBFV) are pathogenic members of the Flaviviridae family. Testing of domestic animals after a suspected alimentary outbreak has shown seropositivity in goats, cows, and sheep, but milk samples are frequently negative for virus (Zeman et al, 2004; Balogh et al, 2010; Caini et al, 2012). This may be due to the length of time between diagnosis of human disease and sampling of suspected animals. Results were not considered to be statistically significant unless a p-value of
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