Prevalence of trichomonads in the cloaca of wild wetland birds in the Netherlands.

Severe granulomatosis in productive layer chickens due to Tetratrichomonas gallinarum strain 13/16632 infection occurred in 2013 and 2017 on farms situated in a wetland area in the Netherlands. We hypothesized that wetland birds could be the source of the infection. Therefore, a prevalence study on trichomonads was performed by analysing cloaca swabs of 526 birds belonging to 13 species of wetland birds. The number of birds sampled ranged from 1 to 275 per species. Birds were sampled at 15 locations in the Netherlands. DNA extracted from the cloaca swabs was subjected to nested PCR using trichomonad-specific primers targeting the internal transcribed spacer 1 (ITS1)-5.8S rRNA-ITS2 region followed by cloning and sequencing. In nine bird species, trichomonads were detected; the overall prevalence was 9% (47/526), while the prevalence in the five species for which a substantial number of birds were examined (at least 39 per species) ranged from 4% to 24%. Three trichomonad species were found: T. gallinarum, Trichomonas tenax and Simplicimonas sp. of which T. gallinarum dominated. The virulent T. gallinarum strain 13/16632 was not detected, but closely related strains were. Phylogenetic analysis revealed that all T. gallinarum isolates belonged to two clusters within lineage 15 of Tetratrichomonas lineages. All T. tenax isolates were identical and clustered with reference strain H95, while Simplicimonas sp. isolates showed large genetic diversity. Some isolates may represent a new species of the genus Simplicimonas. We conclude that trichomonads are widespread amongst wetland birds, raising the question, amongst others, of their relevance for commercial poultry.RESEARCH HIGHLIGHTSTrichomonads occur among wild wetland birds in the Netherlands.T. gallinarum is the dominant trichomonad species in the cloaca of wetland birds.Some T. gallinarum isolates are closely related to a strain causing granulomas in layer chickens.Some isolates may represent a new species of the genus Simplicimonas.

Serologic evidence of West Nile virus and Usutu virus infections in Eurasian coots in the Netherlands.

West Nile virus (WNV) and Usutu virus (USUV) are arboviruses that are maintained in enzootic transmission cycles between mosquitoes and birds and are occasionally transmitted to mammals. As arboviruses are currently expanding their geographic range and emerging in often unpredictable locations, surveillance is considered an important element of preparedness. To determine whether sera collected from resident and migratory birds in the Netherlands as part of avian influenza surveillance would also represent an effective source for proactive arbovirus surveillance, a random selection of such sera was screened for WNV antibodies using a commercial ELISA. In addition, sera of jackdaws and carrion crows captured for previous experimental infection studies were added to the selection. Of the 265 screened serum samples, 27 were found to be WNV-antibody-positive, and subsequent cross-neutralization experiments using WNV and USUV confirmed that five serum samples were positive for only WNV-neutralizing antibodies and seven for only USUV. The positive birds consisted of four Eurasian coots (Fulica atra) and one carrion crow (Corvus corone) for WNV, of which the latter may suggest local presence of the virus, and only Eurasian coots for USUV. As a result, the screening of a small selection of serum samples originally collected for avian influenza surveillance demonstrated a seroprevalence of 1.6% for WNV and 2.8% for USUV, suggesting that this sustained infrastructure could serve as a useful source for future surveillance of arboviruses such as WNV and USUV in the Netherlands.