Global prevalence of Toxoplasma gondii infection in the aborted fetuses and ruminants that had an abortion: A systematic review and meta-analysis

Toxoplasma gondii (T. gondii) is a zoonotic apicomplexan protozoan that can cause reproductive losses in ruminants across the world. Therefore, a meta-analysis was conducted to estimate the worldwide prevalence of T. gondii infection in the aborted fetuses and stillbirths of sheep, goat, and cattle. Moreover, it attempted to evaluate the prevalence rate of T. gondii infection in ruminants that had abortions using serological methods. Based on the keywords, a systematic search of six databases was conducted to retrieve cross-sectional articles in English-language. Data were synthesized to calculate the overall prevalence of T. gondii infection worldwide using the random-effects model with a 95 % confidence interval (CI). Moreover, the present study includes sensitivity analysis, publication bias test, and quality assessment of the studies. The final analyses included 37, 19, and 8 studies conducted on sheep (4383 aborted fetuses and stillbirths as well as 1940 abortive sheep), goat (248 aborted fetuses and stillbirths and 533 abortive goats), and cattle (460 aborted fetuses and stillbirths and 165 abortive cattle). The overall prevalence rates of T. gondii infection in aborted fetuses and stillbirths globally were 42 % (95 % CI: 17 %-67 %), and 31 % (95 % CI: 11 %-51 %) using molecular methods for sheep and goats, as well as 16 % (95 % CI: 11 %22 %) and 27 % (95 % CI: 1 %-54 %) using serological tests for sheep and goats, respectively. In addition, the overall prevalence rates of T. gondii infection in sheep and goats that had abortions were 56 % (95 % CI: 35 %-76 %) and 50 % (95 % CI: 6 %-94 %), respectively. These analyses could not be performed in cattle due to the small number of studies and the small number of animals under study. According to the high prevalence of T. gondii infection in sheep and goats that had an abortion, T. gondii could be a potential factor of causing reproductive failures in ruminants worldwide. So, effective control measures and strategies are needed to reduce the rate of abortion in sheep and goats as well as reduce the economic damage to the livestock industry.