Molecular Prevalence of Avian Haemosporidian Parasites in Southeast Asia: Systematic Review and Meta-Analysis

In this study, for the first time, a systematic review and meta-analysis were conducted to understand the prevalence and genetic diversity of haemosporidian parasites-namely, Plasmodium, Haemoproteus and Leucocytozoon-in avian species in Southeast Asia. Following the PRISMA guidelines, 14,211 studies were retrieved from PubMed, ScienceDirect and Scopus, which contain data relevant to 'Plasmodium' or 'Haemoproteus' or 'Leucocytozoon' and 'birds' or 'chickens'. Of these, 15 articles reporting the prevalence of Plasmodium, Haemoproteus or Leucocytozoon in Southeast Asia were selected for meta-analysis. The pooled prevalence estimates with 95% confidence intervals (CIs) of Plasmodium, Haemoproteus and Leucocytozoon were analyzed using a meta-analysis of their proportions, implemented in R programming. The publication bias was checked using a funnel plot and Egger's test. Consequently, the pooled prevalences of Plasmodium, Haemoproteus and Leucocytozoon in Southeast Asia were found to be 21% (95% CI: 18-25%), 18% (95% CI: 15-22%) and 34% (95% CI: 30-37%), respectively. The prevalence of Plasmodium in domestic poultry (37.94%) was found significantly higher than in wild birds (6.46%). There was substantial heterogeneity among studies related to Plasmodium (χ² = 171.50, p < 0.0001, I² = 94.84%), Haemoproteus (χ² = 52.20, p < 0.0001, I² = 90.4%) and Leucocytozoon (χ² = 433.90, p < 0.0001, I² = 98.80%). Additionally, this review revealed 23 lineages of Plasmodium, 35 lineages of Haemoproteus and 21 lineages of Leucocytozoon reported from both domestic poultry and wild birds in Southeast Asia. In conclusion, this systematic review suggested that the prevalence of avian haemosporidian parasites in Southeast Asia is high. Particularly, domestic poultry has a high prevalence of Plasmodium, suggesting that monitoring of this parasite should be implemented in the poultry production system. Furthermore, several parasites found in wild birds are undescribed species. Further experimental studies using combined microscopic and molecular techniques might reveal the characteristics of overlooked parasites.