The changing epidemiology of lumpy skin disease in Russia since the first introduction from 2015 to 2020

A systematic review of epidemiological modelling in response to lumpy skin disease outbreaks

Lumpy skin disease (LSD) is an infectious disease currently spreading worldwide and poses a serious global threat. However, there is limited evidence and understanding to support the use of models to inform decision-making in LSD outbreak responses. This review aimed to identify modelling approaches that can be used before and during an outbreak of LSD, examining their characteristics and priorities, and proposing a structured workflow. We conducted a systematic review and identified 60 relevant publications on LSD outbreak modelling. The review identified six categories of question to be addressed following outbreak detection (origin, entry pathway, outbreak severity, risk factors, spread, and effectiveness of control measures), and five analytical techniques used to address them (descriptive epidemiology, risk factor analysis, spatiotemporal analysis, dynamic transmission modelling, and simulation modelling). We evaluated the questions each analytical technique can address, along with their data requirements and limitations, and accordingly assigned priorities to the modelling. Based on this, we propose a structured workflow for modelling during an LSD outbreak. Additionally, we emphasise the importance of pre-outbreak preparation and continuous updating of modelling post-outbreak for effective decision-making. This study also discusses the inherent limitations and uncertainties in the identified modelling approaches. To support this workflow, high-quality data must be collected in standardised formats, and efforts should be made to reduce inherent uncertainties of the models. The suggested modelling workflow can be used as a process to support rapid response for countries facing their first LSD occurrence and can be adapted to other transboundary diseases.

Genetic Characterization of Lumpy Skin Disease Viruses Circulating in Lesotho Cattle

Lumpy skin disease is one of the fast-spreading viral diseases of cattle and buffalo that can potentially cause severe economic impact. Lesotho experienced LSD for the first time in 1947 and episodes of outbreaks occurred throughout the decades. In this study, eighteen specimens were collected from LSD-clinically diseased cattle between 2020 and 2022 from Mafeteng, Leribe, Maseru, Berea, and Mohales' Hoek districts of Lesotho. A total of 11 DNA samples were analyzed by PCR and sequencing of the extracellular enveloped virus (EEV) glycoprotein, G-protein-coupled chemokine receptor (GPCR), 30 kDa RNA polymerase subunit (RPO30), and B22R genes. All nucleotide sequences of the above-mentioned genes confirmed that the PCR amplicons of clinical samples are truly LSDV, as they were identical to respective LSDV isolates on the NCBI GenBank. Two of the elevem samples were further characterized by whole-genome sequencing. The analysis, based on both CaPV marker genes and complete genome sequences, revealed that the LSDV isolates from Lesotho cluster with the NW-like LSDVs, which includes the commonly circulating LSDV field isolates from Africa, the Middle East, the Balkans, Turkey, and Eastern Europe.

Subclinical infection caused by a recombinant vaccine-like strain poses high risks of lumpy skin disease virus transmission

Lumpy skin disease (LSD) is a transboundary viral infection, affecting cattle with characteristic manifestations involving multiple body systems. A distinctive characteristic of lumpy skin disease is the subclinical disease manifestation wherein animals have viremia and shed the virus through nasal and ocular discharges, while exhibiting no nodules but enlarged lymph nodes that are easily oversighted by inexperienced vets. Further research on the role of subclinically ill animals in the transmission of LSD virus (LSDV) can contribute to the development of more effective tools to control the disease worldwide. Thus, this study aims to determine the potential role of subclinical infection in virus transmission in a non-vector-borne manner. To achieve this, we inoculated animals with the recombinant vaccine-like strain (RVLS) Udmurtiya/2019 to cause clinical and subclinical LSDV infection. After the disease manifestation, we relocated the subclinically ill animals to a new clean facility followed by the introduction of another five animals to determine the role of RVLS-induced subclinical infection in the virus transmission via direct/indirect contact. After the introduction of the naïve animals to the relocated subclinically ill ones in a shared airspace, two introduced animals contracted the virus (clinically and subclinically), showing symptoms of fever, viremia, and seroconversion in one animal, while three other introduced animals remained healthy and PCR-negative until the end of the study. In general, the findings of this study suggest the importance of considering LSDV subclinical infection as a high-risk condition in disease management and outbreak investigations.

Lumpy skin disease: Insights into current status and geographical expansion of a transboundary viral disease

Lumpy skin disease (LSD) is an emerging transboundary viral disease of livestock animals which was first reported in 1929 in Zambia. Although LSD is a neglected disease of economic importance, it extends a direct impact on the international trade and economy in livestock-dependent countries. Lumpy skin disease virus (LSDV) has been endemic in African countries, where several outbreaks have been reported previously. However, the virus has spread rapidly across the Middle East in the past two decades, reaching Russia and, recently, the Asian subcontinent. With unprecedented cluster outbreaks being reported across Asian countries like India, China, Nepal, Bangladesh, and Pakistan, LSDV is certainly undergoing an epidemiological shift and expanding its geographical footprint worldwide. Due to high mortality among livestock animals, the recent LSD outbreaks have gained attention from global regulatory authorities and raised serious concerns among epidemiologists and veterinary researchers. Despite networked global surveillance of the disease, recurrent LSD cases pose a threat to the livestock industry. Hence, this review provides recent insights into the LSDV biology by augmenting the latest literature associated with its pathogenesis, transmission, current intervention strategies, and economic implications. The review critically examines the changing epidemiological footprint of LSDV globally, especially in relation to developing countries of the Asian subcontinent. We also speculate the possible reasons contributing to the ongoing LSD outbreaks, including illegal animal trade, climate change, genetic recombination events between wild-type and vaccine strains, reversion of vaccine strains to virulent phenotype, and deficiencies in active monitoring during the COVID-19 pandemic.

Lumpy skin disease: history, current understanding and research gaps in the context of recent geographic expansion

Lumpy skin disease is recognized as a transboundary and emerging disease of cattle, buffaloes and other wild ruminants. Being initially restricted to Africa, and since 1989 the Middle East, the unprecedented recent spread across Eurasia demonstrates how underestimated and neglected this disease is. The initial identification of the causative agent of LSD as a poxvirus called LSD virus, was well as findings on LSDV transmission and epidemiology were pioneered at Onderstepoort, South Africa, from as early as the 1940s by researchers such as Weiss, Haig and Alexander. As more data emerges from an ever-increasing number of epidemiological studies, previously emphasized research gaps are being revisited and discussed. The currently available knowledge is in agreement with the previously described South African research experience that LSDV transmission can occur by multiple routes, including indirect contact, shared water sources and arthropods. The virus population is prone to molecular evolution, generating novel phylogenetically distinct variants resulting from a diverse range of selective pressures, including recombination between field and homologous vaccine strains in cell culture that produce virulent recombinants which pose diagnostic challenges. Host restriction is not limited to livestock, with certain wild ruminants being susceptible, with unknown consequences for the epidemiology of the disease.

Lumpy Skin Disease: A Systematic Review of Mode of Transmission, Risk of Emergence and Risk Entry Pathway

The spread of lumpy skin disease (LSD) to free countries over the last 10 years, particularly countries in Europe, Central and South East Asia, has highlighted the threat of emergence in new areas or re-emergence in countries that achieved eradication. This review aimed to identify studies on LSD epidemiology. A focus was made on hosts, modes of transmission and spread, risks of outbreaks and emergence in new areas. In order to summarize the research progress regarding the epidemiological characteristics of LSD virus over the last 40 years, the Preferred Reporting Items for Systematic reviews and Meta-Analyses statement guidelines were followed, via two databases, i.e., PubMed (biomedical literature) and Scopus (peer-reviewed literature including scientific journals, books, and conference proceedings). A total of 86 scientific articles were considered and classified according to the type of epidemiological study, i.e., experimental versus observational. The main findings and limitations of the retrieved articles were summarized: buffaloes are the main non-cattle hosts, the main transmission mode is mechanical, i.e., via blood-sucking vectors, and stable flies are the most competent vectors. Vectors are mainly responsible for a short-distance spread, while cattle trade spread the virus over long distances. Furthermore, vaccine-recombinant strains have emerged. In conclusion, controlling animal trade and insects in animal transport trucks are the most appropriate measures to limit or prevent LSD (re)emergence.

Lumpy skin disease as an emerging infectious disease

Lumpy skin disease (LSD) is one of the most important emerging transboundary diseases. Recently, LSD has emerged in many countries in the northern hemisphere. The LSD virus has a huge genome and is highly resistant to environmental conditions. The virus is also host-specific and large ruminants, such as cattle and domestic water buffalo, are particularly susceptible. In addition, wild ruminants can serve as potential reservoirs for spreading the LSD virus. The emergence might be related to climate change in various regions because LSD is an arthropod-borne infectious disease. This disease causes enormous economic losses, such as leather damage, decreased milk production, abortion, and death in infected ruminants. The economic importance of LSD in the bovine industry has forced countries to develop and implement control strategies against the disease. With the recent global spread and the economic impact, LSD will be discussed intensively. In addition, effective preventive measures are suggested based on the presence or absence of LSD outbreaks.

Evidence of lumpy skin disease virus infection in camels

Countries in the Indian subcontinent are currently facing a deadly epidemic of lumpy skin disease (LSD).  LSD is primarily a disease of cattle. Buffaloes may sometimes develop mild illness, however, other domestic animals are considered resistant to LSD. We confirmed the LSDV infection in camels as evidenced by skin nodules on the body surface of the affected camels, isolation of LSD virus (LSDV) and amplification of LSDV-specific gene segments from the skin nodules (PCR), nucleotide sequencing of the viral genome and, demonstration of anti-LSDV antibodies in serum. Phylogenetic analysis based on nucleotide sequencing of ORF011, ORF012 and ORF036 revealed that the virus (LSDV/Camel/India/2022/Bikaner) is related to the historical NI-2490/Kenya/KSGP-like field strains which are predominantly circulating in the Indian subcontinent. This is the first report wherein LSDV has been to infect camels.

Retrospective genomic analysis of the first Lumpy skin disease virus outbreak in China (2019)

Lumpy skin disease caused by Lumpy skin disease virus (LSDV) is a severe systemic disease affecting cattle and other ruminants. Lumpy skin disease was first reported in northwest China in August 2019 and has severely threatened the cattle breeding industry in China. However, there have been limited genomic studies of LSDV from the first outbreak and its subsequent epidemics. This study aims to characterize the comparative genomic evolution of the LSDV strain from the first outbreak in China. The etiological agent was isolated in a Madin-Darby bovine kidney cell culture and subsequently identified by PCR and Sanger sequencing of six selected genes. The genome sequence was determined using Illumina sequencing and analyzed through genome alignment and phylogenetic tree. The results showed that all six genes were successfully amplified and genetically clustered into LSDV. The virus presented the highest homology to strain China/GD01/2020, which shared 100% identities among 150 open reading frames (ORFs), and 97.1-99.7% identities among additional 6 ORFs. Bayesian inference tree analysis revealed that the virus shared a common ancestor with LSDV strains from China and Vietnam. The study provides an additional genomic data for LSDV tracking and control in China and neighboring countries.

The Characterization and Differentiation of Recombinant Lumpy Skin Disease Isolates Using a Region within ORF134

The recent description and characterization of several novel and unique lumpy skin disease virus (LSDV) strains have revealed the inadequacy of current techniques for differentiating between vaccine- and wild-type viruses. The lack of reliable sequencing targets for promptly distinguishing circulating recombinant vaccine-like strains (RVLSs) highlights the need to develop a single and simple differentiation tool. In this study, we analyzed the available LSDV whole-genome sequences and identified a 705-bp region in open reading frame (ORF) LW134. Based on a single run of nucleotide sequencing and phylogenetic analysis, the region with 13 informative single nucleotide polymorphisms (SNPs) was capable of accurately segregating the novel RVLSs into the same five clusters previously confirmed by whole-genome sequencing. In addition, archived RVLSs from Russia were analyzed for further characterization using the newly described single PCR and sequencing assay. The ORF LW134 assay identified one archived RVLS as a novel cluster distinct from the previously described five clusters, while clustering the remaining samples into previously designated lineages, demonstrating the reliability of the assay. The novel PCR and sequencing assays described in this study have great potential for accurately delineating the molecular and evolutionary affiliation of circulating RVLSs.

Genetic characterization and epidemiological analysis of the first lumpy skin disease virus outbreak in Mongolia, 2021

Novel lumpy skin disease virus (LSDV) strains of recombinant origin are on the rise in South East Asia following the first emergence in 2017, and published evidence demonstrates that such genetic lineages currently dominate the circulation. Mongolia reported first LSD outbreaks in 2021 in a north-eastern region sharing borders with Russia and China. For each of 59 reported LSDV outbreaks, the number of susceptible animals ranged from 8 to 8600 with a median of 572, while the number of infected animals ranged from one to 355 with a median of 14. Phylogenetic inferences revealed a close relationship of LSDV Mongolia/2021 with recombinant vaccine-like LSDV strains from Russia, China, Taiwan, Thailand and Vietnam. These findings support the published data that the circulating strain of LSDV belongs to the dominant recombinant lineage recently established in the region.

Experimentally controlled study indicates that the naturally occurring recombinant vaccine-like lumpy skin disease strain Udmurtiya/2019, detected during freezing winter in northern latitudes, is transmitted via indirect contact

Lumpy skin disease (LSD) caused by LSD virus (LSDV), is a member of the poxvirus genus Capripoxvirus. It is classified as a notifiable disease by the World Organization for Animal Health (WOAH) based on its potential for rapid spread and global economic impact. Due to these characteristics, the mode of LSDV transmission has prompted intensive research efforts. Previous experimental studies using the virulent vaccine-derived recombinant LSDV strain Saratov/2017, demonstrated that this strain has the capacity for transmission in a vector-proof environment. This study demonstrated that a second novel recombinant vaccine-derived LSDV strain Udmurtiya/2019, can infect bulls in contact with diseased animals, in the absence of insect vectors. Bulls were housed in an insect proof animal biosafety level 3 facility, where half the animals were inoculated intravenously with the recombinant LSDV (Udmurtiya/2019), whilst the remaining five animals were mock-inoculated but kept in contact with the inoculated group. Both the infected / inoculated group (IN) and uninfected / incontact group (IC), were monitored for 41 days with continuous registration of body temperature, observations for clinical signs and collection of blood samples and nasal swabs for testing of LSDV presence using real-time PCR. Results indicated that cohabitation of animals from both groups was sufficient to transmit the virus from the IN to the IC-group, with the onset of clinical signs including pyrexia (~41°C) and classical LSD nodular skin lesions starting at 10 dpi for the IN group and 16 dpi for the IC-group. Additionally, the presence of LSDV genomes as well as anti-LSDV antibodies were detected in swabs, blood and serum samples from animals belonging to both groups. These results provides additional evidence of LSDV transmission in a controlled environment without direct contact between diseased and healthy animals, yet in the absence of vectors. Based on these observations, the question concerning a hypothetical relation between mutations in the virus genome and its mode of transmission gains more importance and requires additional investigations with direct comparisons between classical and novel recombinant LSDV strains.

A Recombinant Vaccine-like Strain of Lumpy Skin Disease Virus Causes Low-Level Infection of Cattle through Virus-Inoculated Feed

Since 1989, lumpy skin disease of cattle (LSD) has spread out of Africa via the Middle East northwards and eastwards into Russia, the Far East and South-East Asia. It is now threatening to become a worldwide pandemic, with Australia possibly next in its path. One of the research gaps on the disease concerns its main mode of transmission, most likely via flying insect vectors such as biting flies or mosquitoes. Direct or indirect contact transmission is possible, but appears to be an inefficient route, although there is evidence to support the direct contact route for the newly detected recombinant strains first isolated in Russia. In this study, we used experimental bulls and fed them via virus-inoculated feed to evaluate the indirect contact route. To provide deeper insights, we ran two parallel experiments using the same design to discover differences that involved classical field strain Dagestan/2015 LSDV and recombinant vaccine-like Saratov/2017. Following the attempted indirect contact transmission of the virus from the inoculated feed via the alimentary canal, all bulls in the Dagestan/2015 group remained healthy and did not seroconvert by the end of the experiment, whereas for those in the Saratov/2017 recombinant virus group, of the five bulls fed on virus-inoculated feed, three remained clinically healthy, while two displayed evidence of a mild infection. These results provide support for recombinant virus transmission via the alimentary canal. In addition, of particular note, the negative control in-contact bull in this group exhibited a biphasic fever at days 10 and 20, developed lesions from day 13 onwards, and seroconverted by day 31. Two explanations are feasible here: one is the in-contact animal was somehow able to feed on some of the virus-inoculated bread left over from adjacent animals, but in the case here of the individual troughs being used, that was not likely; the other is the virus was transmitted from the virus-fed animals via an airborne route. Across the infected animals, the virus was detectable in blood from days 18 to 29 and in nasal discharge from days 20 to 42. Post-mortem and histological examinations were also indicative of LSDV infection, supporting further evidence for rapid, in F transmission of this virus. This is the first report of recombinant LSDV strain transmitting via the alimentary mode.