Global status of Anaplasma phagocytophilum infections in human population: A 50-year (1970–2020) meta-analysis

Background & objectives: Anaplasma phagocytophilum causes human granulocytic anaplasmosis; a febrile tick-borne bacterial zoonosis of increasing public health importance in many parts of the world which is life threatening in undiagnosed, misdiagnosed and untreated cases. In this study we determined and reported the global status of the pathogen in man. Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines was used to perform a systematic review and meta-analysis of data published in six electronic databases between 1970 and 2020. We pooled data using the random-effects model, performed sensitivity analysis by the single study deletion method and assess across study bias by the funnel plot and its statistical significance by the Egger's regression test. Results: A total of 7018 cases of A. phagocytophilum were reported from 48,619 individuals examined across 22 countries in three continents. Overall pooled estimate was 8.13% (95% CI: 5.70 – 11.47) with a range of 4.64 (95% CI: 1.78 – 11.54) to 12.18% (95% CI: 7.66 – 18.83) across sub-groups. Regional prevalence was highest in North America 11.07% (95% CI: 3.13 – 32.38), while that in relation to study population was highest among occupationally exposed population 11.41% (95% CI: 5.69 – 21.56). Interpretation & conclusion: The study revealed a significant variation in the prevalence of A. phagocytophilum across Asia, Europe and North America, with the highest prevalence in North America and among occupationally exposed population. To curtail the menace of this growing public health crisis, we recommend integrated control programmes involving tick control, the use of appropriate clothing by occupationally exposed population and health education.