| Toxoplasma gondii(T.gondii)is a worldwide zoonotic parasite that can infect almost all warm-blooded animals,including humans,livestock,and wild mammals.Recent epidemiological investigations have demonstrated that T.gondii is widely present in marine ecosystems,and has become one of the lethal causes of endangered marine mammals.This poses a serious threat to the stability of marine ecosystems and public health security.As a link between land and sea,terrestrial runoff is considered to be the main carrier and channel for T.gondii oocysts from land to the sea.In order to systematically assess the current situation of T.gondii infection in marine mammals worldwide and explore the role of terrestrial runoff in the migration of T.gondii oocysts from land to the sea,this study conducted a meta-analysis and meta-regression of the global prevalence of T.gondii infection in wild marine mammals.Then,an epidemiological survey of marine organisms was conducted to analyze the impact of terrestrial runoffs on the pollution of T.gondii in the marine habitat,based on the hypothesis that terrestrial runoff is an important channel for T.gondii oocysts from land to the sea.A two-dimensional free surface flow model is established to simulate the the migration and decay process of T.gondii oocysts in the Muzhu river,Weihai,and preliminarily estimate the flux into the sea.The main conclusions are as follows:(1)PubMed,Web of Science,Science Direct,China National Knowledge Infrastructure,and Wanfang Data databases were searched literatures related to the prevalence of T.gondii in marine mammals.And identified 84 studies according to the criteria for inclusion in this study.Results of meta-analysis showed that the overall pooled prevalence of T.gondii infection was 22.44%(95%CI:17.29%-28.04%),and the prevalence of T.gondii varied among animal groups,ranging from 3.24%to 65.08%.The subgroup and meta-regression analyses showed that study-level covariates,including age,country,continent,and mean temperature,partly explained the between-study heterogeneity,suggesting that it may be potential risk factors for T.gondii infection in wild marine mammals.(2)The present study investigated the association between T.gondii prevalence and terrestrial runoff using four marine animal species as bioindicators.The results show that the terrestrial runoff is an important factor affecting the prevalence of T.gondii in marine organisms.Pearson’s correlation test showed that there was a significant correlation between the prevalence of T.gondii and the temperature in the study area.The results of this study further demonstrate the advantages of filter-feeding marine shellfish as biological indicators of T.gondii pollution in coastal waters due to their strong water filtering ability.(3)This study establish a two-dimensional free surface flow model to simulate the the migration and attenuation process of T.gondii oocysts in the Muzhu river.The simulation results show that the seasonal runoff affects the transport speed of T.gondii oocysts in Muzhu rivers.The decay degree of T.gondii oocysts in rivers is related to decay rate,migration distance,and initial concentration.By setting different levels of runoff,initial pollution concentration,and decay rate,the flux of T.gondii oocysts into the sea varies,but all above 107 day-1.This indicates that the terrestrial runoff can serve as an important channel for the transmission of T.gondii oocysts from land to the sea. |
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