Diversity of bird schistosomes in anseriform birds in Iceland based on egg measurements and egg morphology

Abstract

Radix balthica is the only freshwater mollusc in Iceland that has been found to be the intermediate host of ocellate furcocercariae. Infections are common. On average, 4.8% out of almost 7,000 snails examined during 2003-2006 were found to shed cercariae in late summer and autumn. Search for adult bird schistosome worms, eggs and miracidia in the intestines and in the nasal cavity of 110 water birds of the orders Gaviiformes (one species), Podicipediformes (one species) and Anseriformes (nine species) revealed 39 (35.5%) infected hosts. Exclusively, anseriform birds were infected. Based on morphological features and measurements of eggs, seven distinct bird schistosome species were detected in four of the bird species. Allobilharzia visceralis was found in 26.7% of the whooper swans Cygnus cygnus. In Anas platyrhynchos, the nasal Trichobilharzia sp. I (prevalence 73.3%) and the visceral Trichobilharzia sp. III (66.7%) were detected. In Mergus serrator, the distinct egg types of Trichobilharzia sp. IV and Trichobilharzia sp. V were found in 83.3% of examined birds. In Anser anser, also two different egg types were found: large eggs, referred to as Trichobilharzia sp. II (prevalence 54.2%), and the small eggs of Dendritobilharzia sp. (8.3%). Egg size and shape comparisons indicate that Trichobilharzia sp. III and T. franki might be the same species.

Final hosts and variability of Trichobilharzia regenti under natural conditions

“…Focusing on the nasal species, T. regenti, five final hosts have already been identified in France; A. platyrhynchos and A. fuligula, previously described by Rudolfová et al (2002) and Picard and Jousson (2001), and also C. olor, M. merganser and A. clypeata (Jouet et al 2009). In Iceland, recent molecular analyses of eggs and adult worms of a nasal Trichobilharzia found in A. platyrhynchos in Landmannalaugar, previously reported by Skírnisson and Kolářová (2008;Skírnisson et al 2009) and Aldhoun et al (2009) as undescribed species, have now confirmed that the involved species actually was T. regenti. Moreover, the detection of T. regenti eggs in the nasal cavity of A. anser represents a new final host record.…”

“…The birds were examined for nasal schistosomes by the perfusion of nostrils with water (to find eggs or freeswimming miracidia in fresh material) and the dissection of the nasal tissue (to find adults) according to Skírnisson and Kolářová (2008). Eggs and fragments of adult worms were measured and usually photographed before fixation in 95°e thanol and freezing for molecular investigations or for staining.…”

“…Some fragments of worms collected from these birds were analysed by molecular methods (Picard and Jousson 2001;Rudolfová et al 2007). The presence of a nasal schistosome was also reported in A. platyrhynchos in Iceland (Skírnisson and Kolářová 2008).…”

Historical analysis of the type species of the genus Trichobilharzia Skrjabin et Zakharov, 1920 (Platyhelminthes: Schistosomatidae)

“…These isolates come from different parts of Europe (Germany, Czech Republic, France, Finland, Denmark, Belarus, Russia) and one from the USA, which proves that T. szidati is a widespread species. Moreover, the size and shape of eggs (important identification characters of Trichobilharzia species as shown by Skírnisson & Kolářová (2008)) in Brumpt's drawings also correspond to T. szidati.…”

Morphological features of the nasal blood fluke Trichobilharzia regenti (Schistosomatidae, Digenea) from naturally infected hosts

“…In late summer this year, and again in 2004, an immense swimmer's itch affected thousands of bathers at this natural bathing site where geothermally heated water is slowly streaming in a brook. This place attracts anseriform birds and the intermediate snail host, Radix peregra (Radix balthica), that is active in the warm ecosystem all around the year (Skírnisson and Kolářová 2008;Skírnisson 2010). Systematic position of the schistosome remained unclear until 2009 when sequencing of eggs of the fluke collected in 2004, and fragments collected in 2009, confirmed the haplotype of T. regenti (Jouet et al 2010).…”