Pautienius et al.
Bulk milk tank samples are suitable to assess circulation of tick-borne encephalitis virus in high endemic areas.
Viruses. 2021; 13:1772 doi: 10.3390/v13091772
In countries with a high prevalence of TBE virus and common occurrence of foodborne infections, milk sample testing may help to assess the prevalence of TBE virus in a certain region and may serve as a complement to monitoring foci by dragging/flagging of ticks.
Goat and milk samples were collected every 4-5 days from farms in Lithuania in 2018/19 in areas with known or suspected association with foodborne TBE outbreaks and were tested by RT-PCR for TBE virus.
A total of 1363 goat and 312 sheep non-pasteurized bulk milk samples were taken from 17 and 4 farms, respectively. Overall, 4.54% of goat and 4.48% of sheep bulk milk samples were found positive. At least one positive sample was detected in 70.58% and 64.70% of tested goat farms in 2018 and 2019, respectively, and at least one positive sample was detected in 75% of sheep farms in both years. Analysis of the geographic distribution showed that positive samples were evenly distributed throughout the territory of Lithuania.
Analyses of TBE virus prevalence in 2685 dragged ticks revealed nine pools out of 283 tick pools positive, but only two were corresponding to positive milk sampling sites.
Milk sampling and analyzing showed a greater effectiveness in terms of time and personnel resources compared to tick dragging and the surveillance strategy based on milk samples proved to be a robust and reliable method. Thus, milk testing for TBE virus can be integrated into milk-borne disease monitoring programs and for epidemiological studies of TBE virus.