Association between Anaplasma phagocytophilum seroprevalence in dogs and distribution of Ixodes ricinus and Ixodes persulcatus ticks in Latvia

Anaplasma phagocytophilum has been detected in ticks in Latvia; however, this is the first study to investigate this pathogen in dogs in Latvia. The aims of this study were: (i) to determine A. phagocytophilum seroprevalence in dogs, (ii) to correlate A. phagocytophilum seroprevalence in dogs with the geographic distribution of the tick species Ixodes ricinus and Ixodes persulcatus, and (iii) to determine if seroprevalence for A. phagocytophilum is higher in dogs with clinical signs suggestive of canine granulocytic anaplasmosis (CGA). Peripheral venous blood samples were collected from 3 dog groups: (i) clinically healthy dogs (HD, n=400), (ii) clinically healthy hunting dogs (HHD, n=41), and (iii) dogs with a clinical suspicion of anaplasmosis (SD, n=29). Sampling was carried out in regions inhabited by I. ricinus (IR), I. persulcatus (IP), and in regions where both tick species were present (M). SNAP 4Dx test (IDEXX) was used to detect antibodies against A. phagocytophilum in the blood of all dogs; nested PCR was performed in selected dogs of the SD group. Seroprevalence for A. phagocytophilum was calculated and correlated with the prevalent tick species in the region. A. phagocytophilum seroprevalence was 11.0% in HD, 12% in HHD, and 17% in SD with no significant differences among groups. In the IR region, seroprevalence was 12.5% (34/272) while seroprevalence in the M region was 17% (13/76), and both were significantly higher than the seroprevalence of 2% in the IP region (2/93; p<0.0005). One CGA case was diagnosed. We conclude that A. phagocytophilum seroprevalence in Latvia is within the range reported from other European countries. CGA should be included in the differential list in Latvian dogs with appropriate clinical signs and laboratory abnormalities, especially in I. ricinus habitat areas.