Bovine parafilariosis – New autochthonous cases from Germany and summary of recent reports from Europe

Bovine parafilariosis is an emerging fly-borne disease in central Europe, characterized by seasonal occurrence of hemorrhagic exudations (ʽbleeding spotsʼ) from the end of winter to end of summer. In two cases from Germany reported here, one animal of a small herd in Bavaria and 20 animals on a farm in Baden-Württemberg presented bleeding spots from late March and late April 2020, respectively. Exudate samples from both cases were positive for larvated Parafilaria eggs. Examination of the skin and trimmed tissue after slaughter of the animal from Bavaria resulted in the collection of 11 nematodes (two males, eight females, one specimen in fragments). The animal's carcass presented typical yellow-greenish areas and bloody spots on the subcutaneous tissue of the flesh side of the skin. The nematodes were microscopically determined as Parafilaria bovicola. Basic morphometric measurements of two (one intact) male and six female nematodes are within the ranges of published data; length (male/female) 28.8/48.0–64.5 mm; width, 397.6 μm/430.7–527.6 μm; distance of cervical papillae to anterior end, 177.6/248.9–337.4; left spiculum/right spiculum (male), 365.3–379.4/149.5–180.3 μm; gubernaculum 45.0–48.1 μm; distance of vulva to anterior end (female), 37.3–66.0 mm. In order to gain information on P. bovicola in its vector, 91 cattle-visiting Musca autumnalis flies were collected from the affected animal in Bavaria (36 flies) and from co-pastured animals (55 flies) for PCR analysis and sequencing. A total of 14 flies were PCR-positive for filarial DNA, and sequencing of a fragment of the cox1 gene resulted in identification of P. bovicola (n = 10) and Thelazia gulosa (n = 5). This study report presents further cases of bovine parafilariosis in Germany, provides morphometric data on male and female P. bovicola nematodes retrieved from cattle and identified DNA of P. bovicola and Tmetonyx gulosa in M. autumnalis flies collected at a site of occurrence of bovine parafilariosis.