Michel et al.
Role of ducks in the transmission cycle of tick-borne encephalitis virus?
Transbound. Emerg. Dis., in press, doi: 10.1111/tbed.13704

It is so far not clearly understood if birds play an active role in the transmission cycle of the TBE virus, although a variety of wild and domestic bird species have been tested during the last sixty years. Mallards (Anas platyrhynchos) from Northern European countries are usually partial migratory birds, while ducks in Central Europe travel over shorter distances.

It has been evaluated if domestic Peking ducks are susceptible to the TBE virus strain Neudörfl (a strain with low neuropathogenicity). Nineteen six-week-old ducks were subcutaneously infected with 105 TCID50/ml virus dilution of strain Neudörfl and one duck was kept negative. None of the infected ducks showed clinical symptoms, however, virus-specific RNA was detected in few blood samples, oropharyngeal and cloacal swab samples, in the spleen of some ducks and in the brain of all infected ducks. All infected ducks seroconverted – beginning at day 6 post-infection (pi). showing only a short viremia – with high neutralizing antibody titers. The gross examination of all animals revealed no specific lesions indicating a viral disease. However, in the histopathology, all ducks showed various mild (5/19), moderate (13/19), or severe (1/19) alterations, and the cerebrum was affected in all cases, but only a small amount of virus was found , and it was not possible to re-isolate the virus.

The authors concluded that ducks do not play a role as undetected TBE virus reservoir. However, due to their rapid and high seroconversion, slaughtered ducks may serve to define the occurrence of TBE virus in affected areas and to detect natural foci.

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