Detection of Anaplasma phagocytophilum in Ovine Serum Samples—A Retrospective Study

Abstract

Tick-borne fever in sheep is caused by Anaplasma phagocytophilum and this obligate intracellular bacterium multiplies mostly in neutrophil granulocytes of its host. In Europe, the pathogen is mainly transmitted by the tick species Ixodes ricinus. Data on the dissemination of A. phagocytophilum in the German sheep population are scarce. Hence, this pilot study aimed to investigate the presence of A. phagocytophilum in ovine serum samples retrospectively. The use of sera is beneficial because the specimens are available in large numbers and usually stored over a long period of time. Ten sheep flocks located in five federal states of Germany (Baden-Württemberg, Bavaria, Lower Saxony, North Rhine-Westphalia, Schleswig-Holstein) were included in the investigations, due to the high intra-flock seroprevalence (>63%) of antibodies against the Anaplasma species. In total, 357 serum samples from seropositive sheep were analysed by 16S rRNA real-time PCR. DNA of A. phagocytophilum was detected in two ewes from the same farm in the northern German federal state of Schleswig-Holstein and represented an overall detection rate of 0.6%. Serum samples can be used to determine A. phagocytophilum, but sensitivity might be reduced in comparison to whole blood samples. Moreover, the sampling time may influence the detection of A. phagocytophilum in sheep, due to the seasonal pattern of tick activity in Germany. Our results support the findings of previous studies and demonstrate that A. phagocytophilum is also present in sheep from northern Germany (Schleswig-Holstein).