Salmonella enterica serovar Abortusequi as an emergent pathogen causing equine abortion in Argentine

Serological investigation and isolation of Salmonella abortus equi in horses in Xinjiang

BACKGROUND

Salmonella enterica subspecies enterica serovar abortus equi (S. abortus equi) is one of the main pathogens that causes abortion in pregnant horses and donkeys, which was highly infectious and greatly restricts the healthy development of the horse industry.

OBJECTIVES

In order to investigate the prevalence and biological characteristics of S. abortus equi in different regions and breeds of horses in Xinjiang.

METHODS

This study conducted ELISA detection of S. abortus equi antibodies on serum samples of 971 horses collected from three large-scale horse farms and five free-range horse farms in Yili Prefecture and Bayingol Mongolian Autonomous Prefecture of Xinjiang from 2020 to 2023. On this basis, bacterial isolation, culture, identification, and drug sensitivity tests were conducted on 42 samples of aborted foal tissues and 23 mare vaginal swabs.

RESULTS

The results showed that the positive rate of S. abortus equi antibody was as high as 20.91% in 971 horse serum samples. Among them, the positive rate in the Ili region (29.09%) was significantly higher than that in the Bayingole region (11.24%), and the positive rate in mares (22.45%) was higher than that in stallions (14.05%). In terms of horse breeds, the positive rates of self-propagating thoroughbred horses, half-bred horses, Ili horses and Yanqi horses were 43.22%, 28.81%, 14.72% and 11.24% respectively. In addition, S. abortus equi was more susceptible to juvenile and elderly horses, with positive rates of 70.00%and 41.86%, respectively, both of which were significantly higher than young (10.97%) and adult (19.79%) horses. Further, 9 strains of S. abortus equi were obtained through bacterial isolation, culture and identification, which were resistant to five antibiotics (Clarithromycin, Clindamycin, penicillin, Sulfamethoxazole and Rifampicin), and sensitive to 13 antimicrobial agents (Amoxicillin, Ciprofloxacin and Gentamicin, et al.).

CONCLUSION

There was a high infection rate of S. abortus equi in Ili Prefecture and self-propagating thoroughbred horses, and juvenile or old mares were more susceptible, which will provide scientific basis for the prevention of S. abortus equi infection in different regions and breeds of horses in Xinjiang.

Complete genome sequencing of a Tequintavirus bacteriophage with a broad host range against Salmonella Abortus equi isolates from donkeys

Salmonella enterica subspecies enterica serovar abortus equi (S. Abortus equi) is the most common cause of abortion in mares. It has recently been found to cause abortion in donkeys more frequently in China. A novel virulent bacteriophage vB_SabS_Sds2 (hereafter designated as Sds2) was isolated from the feces of donkeys using a S. Abortus equi strain as a host. Phage Sds2 had an isometric polyhedral head and an uncontracted long tail, belonging to the Tequintavirus, Markadamsvirinae, Demerecviridae, Caudovirales. The genome of phage Sds2 was 114,770 bp, with a GC content of 40.26%. The genome contained 160 open reading frames (ORFs), and no ORFs were associated with pathogenicity, drug resistance, or lysogenization by sequence analysis. Both genome annotation and phylogenetic analysis indicated that phage Sds2 was highly similar to T5-like bacteriophages. Phage Sds2 could lyse 100% (30/30) of S. Abortus equi strains, 25.3% (24/95) of other serotypes of Salmonella strains, and 27.6% (8/29) of Escherichia coli strains using the double-layer agar plate method. The in vitro test showed that phage Sds2 had high bactericidal activity against S. Abortus equi at a wide range of MOIs. The in vivo test indicated that phage Sds2 had an inhibitory effect on abortion in mice challenged with S. Abortus equi. In general, phage Sds2 is a novel lytic phage with a wide host range and has the potential to prevent abortion caused by S. Abortus equi.

Characterization of Salmonella isolated from donkeys during an abortion storm in China

In China, abortions of donkeys caused by Salmonella have dramatically stifled the growth of the donkey industry. However, pathogenicity of Salmonella linked to abortions in donkeys has not been previously described. Bacteria were isolated and identified from 45 donkeys that experienced abortions, and antibiograms were conducted. Pathogenicity, as median lethal dose (LD₅₀) in mice was then determined. Furthermore, a mouse abortion model was used to re-create the disease observed in donkeys. The pathologic changes in spleen, liver, intestine and embryo were observed by histological examination. An immunofluorescence assay was used to determine the location and distribution of Salmonella colonization in tissues. A clear link was made between S. abortus equi and abortions in donkeys. The bacterial strains isolated from these cases were either highly or moderately sensitive to the 8 antibiotics tested here. The strain of S. abortus equi isolated here was lethal to mice (LD₅₀ value is 1.88 × 10⁸ CFU), and caused abortions in pregnant mice. The 50% abortion-causing dose was 1.22 × 10⁸ CFU. Pathological and immunofluorescence data confirmed that the abortions in pregnant mice and donkeys were accompanied by similar disease processes. Therefore, a Salmonella induced abortion model in mice was developed, characterized by abortion, aberrant embryo development, and parenchymal hypoplasia. The mouse abortion model developed here is an important tool for the future characterization and testing therapeutic interventions.

Developmental Results of a Vaccine against Salmonella-Induced Equine Abortion

An inactivated vaccine based on the Sal. abortus equi BN-12 strain with the Bac. subtilis TNP-3 strain filtrate used as immunomodulator has been developed in order to prevent salmonella-induced equine abortion. Preclinical and clinical trials with the white mice and the horses, respectively, are carried out. The lack of toxicity is proven. The vaccine immunogenicity for mouse and mare models comprised 90 and 100%, respectively. The industrial vaccine tests showed that the industrial output of foals increased by 13.8% after immunization. Cost-effectiveness of the vaccine used with the Bac. subtilis TNP-3 strain filtrate comprised 14.1 rubles per 1 ruble of costs, which was 1.8-fold greater when compared to the vaccine used with a polyribonate medicine. It is ascertained that administration of the inactivated vaccine with the Bac. subtilis TNP-3 strain is an effective method to prevent infectious abortion. Scientific and technical documentation is developed based on the survey results in order to submit it for approval to the Rosselkhoznadzor Federal Service for Veterinary and Phytosanitary Surveillance. The instruction is compliant with the approved use. The registration certificate (71-1-10.19-4495 no. PVR-1-1-.6/01631, as of June 10, 2019) has been issued.

Abortion in donkeys associated with Salmonella abortus equi infection

BACKGROUND

Salmonella enterica subspecies enterica serovar abortus equi (S. abortus equi) is well known as the aetiological agent of equine abortion. However, abortion caused by S. abortus equi has not been previously described in donkeys.

OBJECTIVES

To investigate whether S. abortus equi was correlated with an abortion outbreak consisting of 61 abortions.

STUDY DESIGN

Investigation of the clinical cases using pathoanatomical, bacteriological, serological and molecular approaches.

METHODS

Autopsies on nine aborted foetuses were performed. Tissue specimens from seven aborted foetuses and two mares were cultured and subjected to detection of equine herpesvirus 1 (EHV-1), equine herpesvirus 4 (EHV-4) and equine arteritis virus (EAV) by polymerase chain reaction. The isolates were serotyped according to the Kaufmann-White scheme and analysed by multi-locus sequence typing (MLST). Detection of EHV and EAV antibodies was performed in all pregnant mares.

RESULTS

No obvious gross lesions were observed in the foetuses. Nine Gram-negative isolates were obtained from all nine tissue samples and were identified as Salmonella spp. All of the isolates belonged to the B group, the O antigen epitope was 4, 12 and H antigen was not obtained. The isolates of Salmonella were characterised as sequence type (ST) 251. Detection of EHV-1, EHV-4 and EAV was negative.

MAIN LIMITATIONS

The mechanism that causes abortion in donkeys needs further study and the lack of histological examination.

CONCLUSION

Salmonella abortus equi was isolated as the single agent and was responsible for the abortions. Equine practitioners should be aware of S. abortus equi infection as a cause of abortion in donkeys.

High mortality in foals associated with Salmonella enterica subsp. enterica Abortusequi infection in Italy

Salmonella enterica subsp. enterica serovar Abortusequi is frequently reported as a cause of abortion in mares and neonatal septicemia and polyarthritis in Asian and African countries, but only sporadically in Europe and the United States. We report an outbreak of S. Abortusequi in foals in Italy, characterized by high mortality. In a herd of Murgese horses, 10 of 34 newborns died at birth and a further 7 died, after developing severe clinical signs, during the first 10 d of life. Tissue specimens from different organs of 2 dead foals, synovial fluids from 4 sick foals, and vaginal and rectal swabs from their dams were cultured. A total of 16 isolates, all as pure cultures, were obtained and identified as Salmonella. The isolates exhibited the same antimicrobial resistance pattern and the same sequence type, ST251, a type that has been associated with S. Abortusequi. Six of 16 isolates were serotyped and found to be S. Abortusequi 4,12:-:e,n,x. Equine practitioners should be aware of S. Abortusequi infection as a cause of neonatal mortality in foals.