Bovine infectious abortion: a systematic review and meta-analysis

Abstract

The aim of the present systematic review and meta-analysis was to identify the main infectious agents related to bovine abortion worldwide in the period between 2000 and 2022. First, we investigated the global prevalence of infectious agents related to bovine abortion. For this analysis, only 27 articles detected of a wide panel of agents were included. The random effects model revealed that the estimated prevalence of the abortifacient agents in bovine abortion was 45.7%. The heterogeneity among studies was high, but Egger’s test showed that there was no publication bias, even though the total number of samples analyzed in these articles was variable. There was no significant effect of the year of the study publication on the estimated prevalence, although an increasing trend was observed over time, possibly due to the implementation of new diagnostic techniques. Then, we analyzed the prevalence of the main transmissible agents in bovine abortion. For this analysis, 76 studies that analyzed 19,070 cases were included. Some infectious agent was detected in 7,319 specimens, and a final diagnosis was reached in 3,977 of these, when both the infectious agent and compatible histopathological changes were detected. We found that Neospora caninum was the most detected agent (22.2%), followed by opportunistic bacteria (21.4%), Chlamydiaceae family (10.9%) and Coxiella burnetii (9.5%). Regarding viral agents, bovine herpes virus type 1 and bovine viral diarrhea displayed similar prevalence rates (approximately 5%). After considering the description of specific histopathological changes, our analyzes showed that N. caninum was a confirmed cause of abortion in 16.7% of the analyzed cases, followed by opportunistic bacteria (12.6%) and Chlamydia spp. (6.8%); however, C. burnetii was only confirmed as a cause of abortion in 1.1% of the cases. For all agents, the heterogeneity among studies was high, and the subgroup analyzes discarded the diagnostic method as the cause of such heterogeneity. This study provides knowledge about the global prevalence of the different infectious agents related to bovine abortion, the most coming of which is N. caninum. In addition, this review reveals the existing deficiencies in the diagnosis of bovine abortion that must be addressed in the future.

A Review on the Methodology and Use of the Pregnant Mouse Model in the Study of Brucella Reproductive Pathogenesis and Its Abortifacient Effect

“…In ruminants, abortions at mid-late gestation are the main clinical manifestation of Brucella infection in the field [77]. Abortions at this stage have been linked to hormonal and nutritional factors [31,78], but the underlying mechanisms are poorly understood, and it is possible that foetal deaths during the first trimester of pregnancy may go unnoticed [79]. This way, Brucella-induced abortions are mainly noticed at stillbirth [31], as happens with other abortifacient pathogens such as C. abortus or Toxoplasma gondii [80,81].…”

Cytokine production by bovine adipose tissue stromal vascular fraction cells upon Neospora caninum stimulation

“…N. caninum , unlike T. gondii , is not considered a zoonotic protozoan 22 . Although N. caninum can infect many species, it assumes particular importance in cattle being the most frequent infectious agent detected upon bovine abortion in the 2000–2022 period worldwide 23 , 24 . Neosporosis leads to substantial economic losses in dairy and beef industry that have been estimated at over one billion dollars per year 21 , 25 , 26 .…”