Wide spread incidences of vaccine-like strains of lumpy skin disease virus (LSDV) have recently been reported in a Russian region with a neighboring country that actively vaccinate with a live attenuated LSD vaccine. The use of live-attenuated viruses (LAVs) as vaccines during an active outbreak, creates potential ground for coinfection of hosts and emergence of a strain combining genetic fragments of both parental vaccine and field strains. In this study, we analyse the vaccine-like strain LSDV RUSSIA/Saratov/2017 detected in Saratovskaya oblast, a region sharing border with Kazakhstan. To gain insight into possible recombination signals, a full-genome next-generation sequencing of the viral genome was performed using the Illumina platform. The genome contains the backbone of a live-attenuated vaccine with a patchwork of wild-type field virus DNA fragments located throughout. A total of 27 recombination events were identified. The average distance between the recombination sites was 3400 base pairs (bp). The impact of the recombination events on the virulence and transmission capacity of the identified virus remains to be clarified. These findings provide evidence for the first time of genetic exchanges between closely related strains of capripoxviruses in the field and a vaccine strain, and prompt a revisiting of the vaccination issue for a safe and efficacious prevention and control strategy of LSD.
The transmission of "lumpy skin disease virus" (LSDV) has prompted intensive research efforts due to the rapid spread and high impact of the disease in recent years, especially in eastern europe and Balkan countries. in this study, we experimentally evaluate the vaccine-derived virulent recombinant LSDV strain (Saratov/2017) and provide solid evidence on the capacity of the virus for transmission in a vectorproof environment. In the 60-day long experiment, we used inoculated bulls (IN group) and two groups of in-contact animals (C1 and C2), with the former (C1) being in contact with the inoculated animals at the onset of the trial and the latter (C2) being introduced at day 33 of the experiment. The infection in both groups of contact animals was confirmed clinically, serologically and virologically, and viremia was demonstrated in blood, nasal and ocular excretions, using molecular tools. further studies into LSDV biology are a priority to gain insights into whether the hypothesized indirect contact mode evidenced in this study is a de novo-created feature, absent from both parental stains of the novel (recombinant) LSDV isolate used, or whether it was dormant, but then unlocked by the process of genetic recombination. Author summary: in global terms, LSD has been termed a "neglected disease" due to its historic natural occurrence of being restricted to Africa and, occasionally, israel. However, after its slow spread throughout the Middle east, the disease is now experiencing a resurgence of research interest following a recent and rapid spread into more northern latitudes. Given the dearth of solid findings on potential transmission mechanisms, no efficient or reliable control program currently exists, which does not involve the use of live attenuated vaccines or stamping out policies-both of which are controversial for implementation in non-endemic regions or countries. the vector-borne mode is the only working concept currently available, but with scarce evidence to support the aggressive spread northwards-except for human-assisted spread, including legal or illegal animal transportation. the emergence of outbreaks is not consistently linked to weather conditions, with the potential for new outbreaks to occur and spread rapidly. Here, for the first time, we provide evidence for indirect contact-mode transmission for a naturally-occurring recombinant LSDV isolated from the field. In an insect-proof facility, we obtained solid evidence that the novel LSDV strain can pass to in-contact animals. Given the recombinant nature of the virus utilised, its genetic background relating to the observed transmission pattern within the study needs to be delineated.
Objective The resurgence of lumpy skin disease virus isolates of different genotypic natures abolishes the accuracy of assays that target either vaccine or field strain genome. The aim of the present study was to develop a universal real-time PCR assay using TaqMan chemistry to cover field, vaccine, and recombinant strains of lumpy skin disease virus isolates. Results The PCR assay was designed based on a LSDV044 target region that offers a unique identification locus to facilitate the sensitive and specific detection of all isolates known to date. The efficiency of amplification, determined over five orders of magnitude, was 93%, with the standard deviation remaining in the range of 0.11–0.23. Evaluation of the assay repeatability on three different days revealed that the inter-run variability ranged from 0.83 to 1.22 over five repetitions across three runs. This new screening assay is proposed as a fast, efficient, and sensitive tool that can be employed in the basic or applied surveillance studies regardless of the genotype. Moreover, the assay can be used for the routine laboratory testing of animal samples during eradication programs for lumpy skin disease.
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