ABSTRACT:
The classification of causative Theileria parva strains for East Coast fever, Corridor disease and Zimbabwean theilerioses syndromes has been a contentious matter for decades. The systematic review and meta-analysis were conducted to evaluate the carrier state, pathogenicity and parasitological characteristics of various T. parva strains prevalent in southern Africa. An electronic search was conducted using PubMed, ScienceDirect, and Google Scholar, and a manual search at the Onderstepoort Veterinary Institute Library. Raw proportions for carrier-state and case-fatality risk were transformed using the Freeman-Tukey double-arcsine transformation to normalise the sampling distribution, and heterogeneity was assessed using the I2 value. The pooled estimate of the incidence proportion for Zimbabwean theileriosis was 88% (95% CI: 75–97%; I2 = 80.11%; p < 0.001). The case fatality risk estimate for Zimbabwean theileriosis was 55% (95% CI: 42-68%; I2 = 62.18%; p = 0.001). The incidence proportion estimates for Corridor disease were 86% (95% CI: 69-98%; I2 = 34.80; p = 0.151) and 47% (95% CI: 12-84%; I2 = 87.47; p = <0.001) for buffalo and cattle, respectively. The overall case fatality risk for Corridor disease was 92% (95% CI: 82–98; I2 = 47.08; p < 0.034). The macroscizont index (MSI) ranged from <0.1–69% with an average of 4.3%, while the piroplasm parasitemia ranged from <0.1–48% with an average of 2.15% in Zimbabwean theileriosis. For corridor disease, MSI ranged from 0.1% to 23%, with an average of 7.5%. Piroplasm parasitemia ranged from <0.01% to 0.3%, with an average of 0.1%. This systematic review and meta-analysis showed the extent of carrier state of corridor disease and Zimbabwean theilerioses in cattle and buffalo. The results support earlier observations of distinct parasitological and clinical features of Theileria parva strains prevalent in South Africa and Zimbabwe.