Global prevalence of Anaplasma species infection in domestic small ruminants: a systematic review and meta-analysis.

Abstract

Anaplasma species are obligate intracellular pathogens primarily transmitted by ticks, posing significant threats to livestock health and economic stability worldwide. This systematic review and meta-analysis evaluated the global infection burden of Anaplasma spp. in domestic small ruminants. Three electronic databases were systematically searched for literature published up to 2023, yielding 52 eligible cross-sectional studies evaluating 6,112 goats (31 studies) and 6,671 sheep (40 studies). To prevent diagnostic confounding, datasets were stratified by methodology into serological and molecular (PCR) investigations. In goats, the stratified pooled estimates were 43% for serology and 44% for PCR, demonstrating highly comparable detection frequencies, with macro-geographical trends peaking in Africa (52%), followed by Europe (41%) and Asia (34%). In sheep, serological assays yielded a pooled estimate of 50%, while PCR testing produced a consistent baseline of 46%. A. ovis emerged as the predominant species in both goats (41%) and sheep (45%), whereas the lowest baseline frequencies involved A. capra in goats (19%) and Anaplasma platys in sheep (10%). Exploratory seasonal trends indicated elevated detection rates during warmer months, peaking during autumn for goats (24%) and summer for sheep (26%). However, extreme between-study heterogeneity ([Formula: see text]) persisted across all subgroups, confirming that these pooled estimates represent approximate literature averages influenced by localized variables rather than precise global benchmarks. These insights underscore the necessity for standardized, multi-element One Health surveillance systems to effectively manage tick-borne pathogens in small ruminants.