Distribution and species-specific occurrence of cyathostomins (Nematoda, Strongylida) in naturally infected horses from Italy, United Kingdom and Germany.

A broad scale study was carried out in 2008 to evaluate the distribution and species-specific occurrence of cyathostomin populations in horse yards from Europe. In total 102 properties and 3123 horses were included in Italy (60 yards and 1646 animals), United Kingdom (22 yards and 737 animals) and Germany (20 yards and 740 animals). Individual faecal samples were examined with a McMaster technique while pooled samples were subjected to the microscopic examination of in vitro cultured larvae and to a Reverse Line Blot (RLB) assay able to molecularly identify the most diffused 13 species of cyathostomins. All yards were positive for the presence of cyathostomins both at the McMaster technique and at the microscopic examination of cultured larvae. One thousand and nine hundred thirty-one horses (61.8%) showed a positive faecal egg count, i.e. 1110 (67.4%), 463 (62.8%) and 358 (48.3%) from Italy, UK and Germany respectively. Out of the 1931 positive animals 1133 (36.3%) showed a faecal egg count per gram >150, specifically 694 (42.2%) from Italy, 237 (32.2%) from UK and 202 (27.3%) from Germany. The molecular results showed that all 13 species that can be detected by the RLB were found in each of the three countries, with a range of 3-13 species present in individual yards. The five most prevalent were Cylicocyclus nassatus, Cylicostephanus longibursatus, Cyathostomum catinatum, Cylicocyclus goldi and Cyathostomum pateratum. The relevance of these results and related biological and epidemiological features are discussed, together with their significance for both future studies of cyathostomins and further intervention programs aiming to control the spread of anthelmintic-resistant populations.