Background: Foot-and-mouth disease virus (FMDV) is a highly contagious viral infection of large ruminants. Despite the massive application of vaccines against FMDV, several outbreaks are still being reported in Africa and Asia.

Aim: To perform molecular characterization of FMDV in an outbreak among a cattle herd Saudi Arabia in 2016. This herd had been vaccinated with a polyvalent FMDV vaccine.

Methods: To investigate this outbreak, we collected specimens from 77 animals showing typical clinical signs of FMDV. Specimens including sera, nasal swabs, and tissues (tongue, coronary bands, hooves, and hearts) were collected. We tested the collected cattle sera for the presence of FMDV antibodies with commercial ELISA kits. In addition, we tested the swabs for the presence of the most common FMDV strains (O, A, Asia-1 and SAT-2) with RT-PCR using serotype-specific oligonucleotides.

Results: Serology showed that 22% of the tested sera were positive. Molecular testing of the examined swabs confirmed that 24% of the tested animals were positive. Our sequencing analysis confirmed that the circulating strains of FMDV belonged to FMDV serotype O. The phylogenetic tree based on the FMDV-VP-1 gene revealed high nucleotide identity between the circulating strains and the Bangladesh strain (99%). These strains were distinct (shared 89% nucleotide identity) from the FMDV-O strains used for the preparation of the vaccine administered to the animals in this herd. Moreover, they had 7% nucleotide difference between the FMDV-O strains reported in Saudi Arabian in 2013.

Conclusion: More in-depth molecular characterization of these FMDV strains is warranted.

背景：口蹄疫病毒（FMDV）是大型反刍动物的高度传染性病毒感染。尽管针对FMDV的疫苗大量应用，但非洲和亚洲仍报告了几次暴发。

目的：在2016年沙特阿拉伯的牛群爆发中对FMDV进行分子鉴定。该牛群已接种多价FMDV疫苗。

方法：为了调查这次疫情，我们从77头动物中采集了标本，这些标本显示了FMDV的典型临床体征。收集标本，包括血清，鼻拭子和组织（舌，冠状动脉带，蹄和心脏）。我们使用商业ELISA试剂盒测试了收集的牛血清中是否存在FMDV抗体。此外，我们使用血清型特异性寡核苷酸通过RT-PCR测试了棉签中最常见的FMDV菌株（O，A，Asia-1和SAT-2）的存在。

结果：血清学检查显示22％的血清呈阳性。对受检拭子的分子测试证实，有24％的受测动物为阳性。我们的测序分析证实，FMDV的循环菌株属于O型血清型FMDV。基于FMDV-VP-1基因的系统进化树显示，该循环菌株与孟加拉菌株之间具有高度核苷酸同一性（99％）。这些菌株与FMDV-O菌株截然不同（共有89％的核苷酸同一性），所述FMDV-O菌株用于制备向该猪群中的动物施用的疫苗。此外，2013年在沙特阿拉伯报道的FMDV-O菌株之间，它们的核苷酸差异为7％。

结论：这些FMDV菌株的更深入的分子表征是有必要的。