To get sick or not to get sick-Trichomonas infections in two Accipiter species from Germany.

Trichomonosis caused by the flagellate Trichomonas gallinae is one of the most important avian diseases worldwide. The parasite is localised in the oesophageal area of its host and mainly infects pigeon and dove species. During the last decade, a host expansion to passerine birds occurred, making the disease a potential threat for passerine predators as naïve host species. Here, we investigated the effect of the parasite on two Accipiter species in Germany which show a comparable lifestyle but differ in prey choice, the Northern goshawk (Accipiter gentilis) mainly hunting pigeons and the Eurasian sparrowhawk (Accipiter nisus) mainly feeding on passerines. We genetically identified the parasite strains using the Fe-Hydrogenase gene as marker locus and compared the incidence of parasite presence and clinical signs of trichomonosis between nestlings of the two Accipiter species. In total, we identified 14 strains, with nine strains unknown so far. There was a higher strain diversity and prevalence of Trichomonas spp. in goshawks than sparrowhawks (42.4% vs. 21.2%) whereas sparrowhawks when being infected more often displayed clinical signs of trichomonosis than goshawks (37.1% vs. 6.1%). Even though sparrowhawks were mainly infected with the finch epidemic strain and genetic data indicated some variation between isolates, no correlation with virulence could be detected. All in all, goshawks seem to be better adapted to Trichomonas infections, whereas to sparrowhawks, this is a novel disease with more severe manifestations, from individual morbidity to a higher risk of population decline caused by trichomonosis.

Chronic lead intoxication decreases intestinal helminth species richness and infection intensity in mallards (Anas platyrhynchos).

Lead (Pb) pollution of aquatic habitats is a known threat to vertebrate health. Depending on Pb dosage, resulting symptoms can be chronic (sublethal) or acute (lethal). While acute exposure results in death of the animal, chronic sublethal exposure can also have consequences, reproduction, antioxidant defense and immunity being the most affected traits. While a great deal is known about Pb intoxication on avian health, relatively little is known about how intoxication impacts parasites dependent on their avian hosts. The effect of Pb on intestinal helminth species richness and infection intensity was investigated in mallards (Anas platyrhynchos, n = 100) from German waters. Coracoid bones were used to measure chronic Pb exposure. Intestinal helminths were characterized morphologically. Molecular approaches were also applied to identify poorly morphologically preserved parasites to obtain sequence data (cox1 gene) for species identification and future parasitological studies. Parasite species richness and infection intensity was found to be significantly lower in birds with higher chronic Pb levels suggesting both host and parasites respond to Pb exposure. Altered immune modulation in the avian host may be the underlying mechanisms of Pb triggered decrease of parasites. However, it also likely reflects differences in the susceptibility of different helminths to Pb. Cestode and acanthocephala species richness were particularly impacted by Pb exposure. We conclude that, Pb intoxication may both negatively impact avian host and parasite diversity in aquatic habitats.