Prevalence of subclinical mastitis, its associated bacterial isolates and risk factors among cattle in Africa: a systematic review and meta-analysis

Table 1 Heterogeneity statistics for prevalence of sub-clinical mastitis among cattle in Africa based location and publication period. Data sets for the period 2010 to 2020

Variable	Subgroup	No. of studies	Cattle tested by CMT			Heterogeneity			Univariate meta-regression
			No. tested	No. positive	% (95% CI)	χ²	p-value	I² (%)	p-value	τ², H²	Cochran Q statistic	R² (%)
Period									0.417	0.04, 53.6	0.66 (df = 1)	0.00
	Before 2015	36	10,947	4225	46.0 (39.1–52.9)	1545.06	< 0.01	98 (97 to 99)
	After 2015	46	14,158	7076	49.9 (43.7–55.9)	1778.64	< 0.0001	98 (97 to 99)
	Total	82	25,105	11,301
Region									0.0092	0.04, 47.0	13.47 df=(4)	10.84
	Horn of Africa^a	43	14,208	6040	47.4 (41.4–53.3)	1318.46	< 0.01	97 (96 to 98)
	East Africa	10	3056	2009	67.7 (55.7–78.7)	186.91	< 0.01	95 (94 to 96)
	West Africa	4	1239	591	50.5 (31.4–69.5)	361.02	< 0.01	99 (98 to 100)
	North Africa	23	5846	2422	40.3 (32.3–48.6)	671.61	< 0.01	97 (96 to 98)
	Southern Africa^a	2	756	239	49.4 (23.2–75.8)	289.34	< 0.01	100
	Total	82	25,105	11,301

CI: Confidence intervals. 95% CIs were calculated as described by Higgins and Thompson [85]
I² (%): Residual heterogeneity (unaccounted heterogeneity)
R²: Proportion of between-study variance explained
QM: Coefficient of test for heterogeneity between subgroups; df = degrees of freedom
τ² (tau squared) = between-study variance - estimated variance of the distribution of true prevalence in the population of sub-clinical mastitis studies
H² = unaccounted variability (sampling variability) – the ratio of the standard deviation of the estimated overall prevalence from the random-effects model compared to the standard deviation from the fixed-effects model
^a Studies were from only one country: Horn of Africa (Ethiopia); Southern Africa (Zimbabwe)
CMT = California mastitis test; df = degrees of freedom

ISSN: 1746-6148