Detection of Anaplasma phagocytophilum in horses from Germany by molecular and serological testing (2008-2021).

The research paper investigated the prevalence of the tick-borne disease Equine granulocytic anaplasmosis in horses in Germany, looking at over fourteen years of data from a commercial lab. The findings highlight the seasonal and geographic trends in infection rates and suggest specific symptoms for diagnosis.

Research Methodology

• The study is retrospective, meaning it looked at existing data from A. phagocytophilum testing of horses done in a commercial laboratory (LABOKLIN) in Germany from 2008 to 2021. The focus was on evaluating both direct and indirect detection methods.
• Direct detection was based on the Polymerase chain reaction (PCR), a technique used to amplify small segments of DNA. Indirect detection, on the other hand, used the immunofluorescence antibody test (IFAT) which detects antibodies and thus shows exposure rather than current infection.
• The research also evaluated potential risk factors and analyzed hematological abnormalities in horses with positive PCR results.
• For horses that tested positive, additional tests such as a Complete Blood Count (CBC) and Serum Amyloid A (SAA) were also conducted.

Key Findings

• Out of 4834 horses, 1217 tested positive in total. Of this number, 190 out of 1246 horses (15.2%) were positive according to PCR, while 1036 out of 3849 horses (26.9%) were positive according to IFAT.
• Both seasonality and location (measured by federal state) significantly affected the PCR results.
• The research found hematological abnormalities in 112 out of 118 horses (95%) with positive PCR results, with the most common disorders being thrombocytopenia (86%) and anemia (52%). The remaining 6 out of 118 horses (5%) showed no abnormalities in their blood counts.
• An analysis of SAA results in 35 horses with positive results revealed a significant increase in levels.

Conclusions

• The trend in the timing of A. phagocytophilum infections, as confirmed by PCR testing, was aligned with the known periods of increased vector (in this case, tick) activity in Germany.
• The high infection rates in horses compared to dogs and cats might be due to insufficient preventative measures against ectoparasites (ticks).
• Given the prevalence and diagnosable symptoms of the infection, the study advises that A. phagocytophilum infections should be considered in the differential diagnosis of horses showing cytopenia in CBC and elevated SAA, especially during the summer and following possible tick exposure.