Bovine transmissible abortion: a systematic review and meta-analysis

HECKER, YANINA PAOLA; SARA GONZÁLEZ-ORTEGA; SANTIAGO CANO; ORTEGA-MORA, LUIS M.; HORCAJO, PILAR

Seminario; 2023 Virtual Seminar on Bovine Neosporosis: "Quo Vadis"; 2023

Universidade Santo Amaro

The aim of the present study was to perform a systematic review and meta-analysis of the main transmissible agents involved in bovine abortion. Suitable scientific articles published in the period between 2000 and 2022 were identified through a systematic literature search and subjected to screening. More than three thousand studies were eligible for data extraction but finally only 76 were included in this work because they met the inclusion criteria established. The selected works were representative from 31 countries from four continents. First, we analysed the global prevalence of the abortifacient agents in bovine abortion samples. For this analysis, only 27 articles that diagnosed a wide panel of agents (viruses, bacteria, protozoa and/or fungi) were included. The estimated prevalence of the abortifacient agents in bovine abortion using a random effect model was 45.7%. The heterogeneity was high among studies (I2 = 99.2%) but Egger’s test showed that there was not publication bias on the overall prevalence estimated, even though the total number of samples analysed in these articles was variable. There was not a significant effect of the year of the study publication on the estimate prevalence, although a tendency to increase over time was observed, possibly due to the implementation of new diagnostic techniques. Then we analysed the prevalence of the main transmissible agents in bovine abortion. Of the over nineteen thousand cases of abortion, in over seven thousand cases at least one infectious agent was detected but only in around fifty percent of them the infectious agent was confirmed as the cause of abortion by finding compatible histopathological lesions. According to this study, Neospora caninum was the agent more frequently detected in cases of bovine abortion (22.2%), followed by opportunistic bacteria (21.0%), Chlamydaceae family (10.9%) and Coxiella burnetii (9.5%). Regarding viral agents, the Bovine Herpes Virus type 1 (BoHV-1) and Bovine Viral Diarrhoea (BVDV) displayed similar prevalence (around 5%). After considering the description of specific histopathological lesions, our analyses showed that N. caninum was a confirmed cause of abortion in the 16.7% of the analysed cases, Chlamydia spp. or Leptospira spp in around 5% and C. burnetii only in 1% of the cases analysed. For all agents the heterogeneity among studies was very high. The subgroup analyses based on the diagnostic method discarded this as the cause of such heterogeneity. The year of publication had no influence in the prevalence of the any agent.This work shows the relative importance of the infectious agents in bovine abortion, being N. caninum the most prevalent agents. In addition, this study reveals the existing deficiencies in the diagnosis of bovine abortion and the lack of information about the situation in regions with a relevant livestock industry.