Prevalence of Haemoparasites Species Infecting Free-Range Chickens in Africa: A Systematic Review and Meta-Analysis

The overall burden and distribution of haemoparasite infections in free-range chickens remain inadequately studied, even though these parasites can pose serious threats to poultry health and productivity throughout Africa. Therefore, this study aimed to assess the prevalence and diversity of haemoparasites using a systematic review and meta-analysis approach. A comprehensive literature search was conducted across four electronic databases for peer-reviewed articles published from 1995 to 2024. Following critical appraisal, twenty-three studies met the inclusion criteria. The pooled overall prevalence of haemoparasite infection was 5% (95% CI: 3–7%). Eastern Africa recorded the highest prevalence at 18% (95% CI: 5–36%), whereas western Africa reported the lowest prevalence at 5% (95% CI: 3–7%). Comparatively, cocks exhibited a higher pooled prevalence of 28% (95% CI: 17–39%) than hens at 12% (95% CI: 2–25%). Among genus infections, Plasmodium showed the highest pooled prevalence at 14% (95% CI: 8–21%), while Leucocytozoon and Haemoproteus had low pooled prevalence (both 4%). Mixed-infections of Plasmodium and Leucocytozoon showed a pooled prevalence of 3% (95% CI:0–14%). A high level of heterogeneity was observed across all genera, except Trypanosoma (I2 = 0%). Studies which used nested PCR reported a higher pooled prevalence (9%; 95% CI: 2–19%) compared with microscopy (5%; 95% CI: 3–8%). Univariate meta-regression identified parasite species and sample size as significant sources of heterogeneity in the prevalence estimates (p < 0.05). Overall, these findings provide valuable insights into the prevalence of haemoparasite infections in free-range chickens and underscore the need for improved diagnostic capacity, through improved access and use of sensitive molecular techniques such as nested PCR, and provision of resources for improved surveillance systems across African countries.