Bauer et al.
Increasing awareness for tick-borne encephalitis virus using small ruminants as suitable sentinels: preliminary observations
One Health. 2021; 12:100227, doi.org/10.1016/j.onehlt.2021.100227
Various animals have been shown to be suitable as sentinel to monitor TBE virus infections (see e.g., Newsletter January 2021, Snapshot week 8/2021, Snapshot week 41/2020, Snapshot week 18/2020, Snapshot week 7/2020).
Examining sera for TBE antibodies from sheep and goats, living in the environment where human cases have occurred, have been useful to identify TBE foci. A study has been carried out in five federal states with the largest sheep population in Germany from winter 2017 to spring 2018 to analyze TBE antibodies. A total of 36 ruminant flocks (1396 sheep and 323 goats) from 27 districts located in TBE risk areas and 35 ruminant flocks (1331 sheep and 124 goats) from 22 districts in TBE non-risk areas were involved in this study. TBE antibodies were analyzed by a commercial ELISA and were verified by neutralization assay.
In the TBE risk areas (southern Germany), 78 sheep and 22 goats tested positive for TBE antibodies and positive results coincided with human cases in 14 districts. In addition, there were also five districts with zero human incidence in 2017, where antibodies were positive between 2.3% and 25% of animals tested. Positive sheep and goats were also found in northern Germany (non-risk areas with only spontaneously reported TBE cases).
In summary, the numbers of TBE positive small ruminants were higher in TBE risk areas compared to non-risk areas. The authors concluded that small ruminants are suitable sentinel animals for identifying new TBE virus foci independent from reported human cases.