Results of this meta-analysis revealed that age plays an important role in development of Theileriosis in cattle. Adult cattle are found twice at risk for BTT than the younger stocks with an odds ratio of 2.062 (95% CI 1.352 – 3.145) which was highly significant (Q= 38.729; p=0.0) with substantial heterogeneity (I² = 476.76%). As regards age factor in the distribution of BTT these findings correspond to earlier reports by Panda et al. (2011); Kumar (2012); Agrawal (2016); Kolte et al. (2017); Ghosh et al. (2020). However, several other studies contradicted these findings (Salih et al., 2013; Velusamy et al., 2014). Since adult cattle particularly cows are usually subjected to milk production, the stress due to lactation and pregnancy will be a major predisposing factor for getting BTT and other infectious disease. Additionally, higher exposure of vectors to adult cattle due to open grazing is also an important contributing factor. On the other hand, young stock which are generally raised on intensive feeding and confined housing are less prone to attack by vectors and therby vector borne diseases (Bhutto et al., 2010). Even earlier reports justifying the age related resistance in young stock to most of the tick borne protozoan and rickettsial diseases including T.annulata (Dumanli et al., 2005).

Sex of cattle was found to have moderate impact to make the animal susceptible for BTT. It was estimated that cows are little more susceptible to BTT than bullocks / bulls with an odds ratio of 1.632 (95% CI 1.266 – 2.104). However, with lower heterogeneity between studies (I² = 42.54%) this estimate was non-significant (Q = 13.923; p=0.08). These findings also corroborates with earlier reports by Zaman et al. (2020). However, the rationale for such distribution may be attributed to certain intrinsic factors such as hormones may have a role to play (Kumar et al., 2017). As males are either culled or utilized for drought purposes as against cows which are raised longer for milk production and breeding are under persistent physiological stress due to pregnancy and/or lactation. This stress along with suppression of immunity may predispose those cows to higher risk of getting infected with BTT (Kamani et al., 2010, Ghosh et al., 2018).

As being reported since long, exotic / crossbred cattle are more prone to contract BTT with an odds ratio of 2.113 (95% CI = 1.315 – 3.396) which was even supported by several earlier evidences based on molecular studies (Kumar et al., 2017). Similarly, the estimates of current meta-analysis also seconded this, however there is absence of heterogeneity (I² = 0%) between the studies under this meta-analysis. The results on the basis of Q statistics (0.304; p= 0.99) are non-significant. Yet the current metaanalysis revealed that exotic and cross bred cattle are two fold at risk of getting infected with BTT than those cattle of domestic breeds. Similar trends were reported earlier by Salih et al., (2013); Ghosh et al., (2018); Gharbi et al., (2020). The observations of current study have strongly justified the earlier report by Kolte et al., (2017) wherein they have validated that germplasm of the cattle was crucial for the infection of Theileriosis and found that carrier crossbred cattle attracts more maintenance costs to the dairy enterprises. Furthermore, earlier reports also pointed out low case fatality and infection rates in local breeds while the higher morbidity and mortality in exotic and crossbred cattle (Jensen et al., 2007).

Since the 95% confidence intervals of odds ratios for all the factors under this study are more than 1 and did not include 1 (i.e. OR ≠1), the effects size i.e. pooled ORs are significant at 5% level of significance.

The meta-analysis conducted for individual risk factor with selected set of studies for each of them has also tested for publication bias and presented through LFK Index and Doi plot individually. The LFK indices for each of them are in the range of 0 – 1 which signifies no publication bias (Table 2). Also visual observation of Doi plots also seconded the absence of publication bias between the studies included for this analysis (Figs. 2, 3, 4). No publication bias in meta-analysis of risk factors of BTT in Indian cattle was found for individual analysis conducted (Barendregt and Doi, 2011 and Kanamori et al., 2018).