Lumpy Skin Disease

Lumpy skin disease virus (LSDV) is a vector-transmitted poxvirus that causes disease in cattle. Vector species involved in LSDV transmission and their ability to acquire and transmit the virus are poorly characterized. Using a highly representative bovine experimental model of lumpy skin disease, we fed four model vector species (Aedes aegypti, Culex quinquefasciatus, Stomoxys calcitrans, and Culicoides nubeculosus) on LSDV-inoculated cattle in order to examine their acquisition and retention of LSDV. Subclinical disease was a more common outcome than clinical disease in the inoculated cattle. Importantly, the probability of vectors acquiring LSDV from a subclinical animal (0.006) was very low compared with that from a clinical animal (0.23), meaning an insect feeding on a subclinical animal was 97% less likely to acquire LSDV than one feeding on a clinical animal. All four potential vector species studied acquired LSDV from the host at a similar rate, but Aedes aegypti and Stomoxys calcitrans retained the virus for a longer time, up to 8 days. There was no evidence of virus replication in the vector, consistent with mechanical rather than biological transmission. The parameters obtained in this study were combined with data from studies of LSDV transmission and vector life history parameters to determine the basic reproduction number of LSDV in cattle mediated by each of the model species. This reproduction number was highest for Stomoxys calcitrans (19.1), followed by C. nubeculosus (7.1) and Ae. aegypti (2.4), indicating that these three species are potentially efficient transmitters of LSDV; this information can be used to inform LSD control programs.IMPORTANCE Lumpy skin disease virus (LSDV) causes a severe systemic disease characterized by cutaneous nodules in cattle. LSDV is a rapidly emerging pathogen, having spread since 2012 into Europe and Russia and across Asia. The vector-borne nature of LSDV transmission is believed to have promoted this rapid geographic spread of the virus; however, a lack of quantitative evidence about LSDV transmission has hampered effective control of the disease during the current epidemic. Our research shows subclinical cattle play little part in virus transmission relative to clinical cattle and reveals a low probability of virus acquisition by insects at the preclinical stage. We have also calculated the reproductive number of different insect species, therefore identifying efficient transmitters of LSDV. This information is of utmost importance, as it will help to define epidemiological control measures during LSDV epidemics and of particular consequence in resource-poor regions where LSD vaccination may be less than adequate.

Lumpy skin disease (LSD) is a vector-borne infection caused by the poxvirus lumpy skin disease virus (LSDV) and is a serious disease of cattle, water buffalo, and banteng. While the disease has never occurred in Australia, it is regarded as a growing threat to the Australian cattle industry as there is on-going spread of the disease throughout Asia. The development of geospatial decision support tools, such as spatial epidemiological modelling, may assist in assessing areas at greater risk of this threat. To guide the design of disease modelling approaches to support future risk-based surveillance, existing LSDV epidemiological models need to be evaluated. In this study, we performed a literature review to evaluate existing LSDV epidemiological models, identify key risk factors for introduction and spread of LSDV, and consider previously adopted control strategies. The PRISMA guidelines were used to establish the processes for article selection and information extraction, and the PICO process was used to formulate search terms. From studies that met our inclusion criteria, we extracted information on LSDV epidemiological model structure and parameterisation, risk factors for LSDV transmission and spread, and biosecurity control strategies. The literature search retrieved a total of 402 articles from four databases, of which 68 were identified for inclusion in this review following screening. Of the 68 articles reviewed, 47 explored risk factors associated with LSDV transmission and spread, four explored risk factors of LSDV introduction, four explored existing surveillance strategies in LSD-free countries, and 14 presented epidemiological models. Our findings indicate that there are various risk factors for LSDV transmission in LSD endemic countries, including long-distance airborne movement of infected vectors such as stable flies and cattle movement between countries over land borders. Key risk factors for LSDV spread in LSD endemic countries include physical environmental characteristics, weather conditions, and population distributions of livestock and vectors. Our results indicate that while a variety of modelling studies have been conducted, the majority of studies experimentally explored LSD transmission mechanisms in vectors and cattle. Spatial and spatio-temporal models have primarily been developed for LSD endemic countries and focus on the spread of the disease in terms of environmental factors in relation to previous LSD events. There were very few studies on LSD-free countries, and these only focussed on risk of LSD introduction through specific entry pathways. This review did not identify any literature exploring the risk of spread of LSDV following introduction in LSD-free countries or geospatial modelling of the suitability of LSD-free countries for LSDV incursions. In conjunction with the risk parameters and models described in the identified literature, there is need to consider a wide range of risk factors specific to Australia to inform the design of risk-based surveillance for LSD in Australia.

Lumpy skin disease (LSD) has emerged as a threat to cattle production in Asia, and India has been facing LSD epidemics since 2019. Although water buffalo (Bubalus bubalis) is susceptible to natural LSDV infection, there have been no confirmed reports of LSDV infection in water buffalo in India. In this study, we investigated suspected cases of LSD in water buffaloes from 12 Indian states and one union territory during 2020-2023. Buffaloes showed mild to moderate clinical disease with fever and nodular skin lesions, but most remained asymptomatic. Eighteen of 177 (10.18%) buffaloes in 12 districts in three states tested positive for LSDV by real-time PCR, while 22 of 57 (38.59%) from nine districts in six states tested positive for LSDV-neutralizing antibodies, demonstrating the prevalence of LSDV infection in buffaloes over a wider geographic area. Successful virus isolation and nucleotide sequencing confirmed natural LSDV infection in buffaloes. Phylogenetic analysis of complete GPCR, RPO30, and EEV gene sequences revealed the presence of wild-type strains of two divergent LSDV lineages (1.2.1 and 1.2.2) in buffaloes. The 1.2.2 strains were closely related to the dominant LSDV strain (subcluster 1.2.2, KSGP-like) circulating in India, while the 1.2.1 strains clustered with strains from the Middle East, Europe, and the Balkans, confirming that there have been multiple introductions of LSDV into India. The detection of viruses with identical sequences in buffaloes and local cattle implied that the LSDV strain found in buffaloes is probably of cattle origin. We also found evidence of cocirculation of LSDV 1.2.1 and 1.2.2 wild-type strains in the same area, highlighting the importance of LSDV surveillance and genetic analysis. This is the first confirmed report of natural LSDV infection in water buffaloes in India. Further investigations are needed to assess the impact of LSDV infection in buffalo production and the role of buffalo in LSD epidemiology.

Infection, dissemination, and transmission of lumpy skin disease virus in Aedes aegypti (Linnaeus), Culex tritaeniorhynchus (Giles), and Culex quinquefasciatus (Say) mosquitoes

Potential mechanical transmission of Lumpy skin disease virus (LSDV) by the stable fly (Stomoxys calcitrans) through regurgitation and defecation

A quantitative risk assessment for the incursion of lumpy skin disease virus into Australia via long-distance windborne dispersal of arthropod vectors.

Since 2012, lumpy skin disease virus (LSDV) has been spreading from the Middle East to south-east Europe and Russia. Although vaccination campaigns have managed to contain LSDV outbreaks, the risk of further spread is still high. The most likely route of LSDV transmission in short distance spread is vector-borne. Several arthropod species have been suggested as potential vectors, but no proven vector has yet been identified. To check whether promiscuous-landing synanthropic flies such as the common housefly (Musca domestica) could be involved, we carried out entomological trapping at the site of a recent LSDV outbreak caused by a vaccine-like LSDV strain. The presence of vaccine-like LSDV DNA was confirmed by the assay developed herein, the assay by Agianniotaki etal. (2017) and RPO30 gene sequencing. No evidence of field LSDV strain circulation was revealed. In this study, we discovered that M.domestica flies carried vaccine-like LSDV DNA (Ct >25.5), whereas trapped stable flies from the same collection were negative for both field and vaccine LSDV. To check whether flies were contaminated internally and externally, 50 randomly selected flies from the same collection were washed four times and tested. Viral DNA was mainly detected in the 1st wash fluid, suggesting genome or even viral contamination on the insect cadaver. In this study, internal contamination in the insect bodies without differentiation between the body locations was also revealed; however, the clinical relevance for mechanical transmission is unknown. Further work is needed to clarify a role of M.domestica in the transmission of LSDV. To our knowledge, this is the first report demonstrating that an attenuated LSD vaccine strain has been identified in Russian cattle given the ban on the use of live attenuated vaccines against LSDV.

Lumpy skin disease (LSD) is a serious threat to the global cattle farming, including that in the Russian Federation where the frst outbreak was reported in 2015. Since the disease occurred for the frst time, it has continued to spread in this country; however, virus transmission mechanisms have not yet been studied. Transmission through insect bites is considered to be the most likely mechanism of virus shortrange transmission. At present, such arthropod species as stable fly (Stomoxysсalcitrans), Aedes aegyptimosquitoes, as well asAmblyomma hebraeumandRhipicephalus appendiculatusticks are regarded as potential vectors. Viral DNA has also been detected on the exoskeletons of house flies (Musca domestica). The available literature describes the results of many studies on the role of arthropods in LSD virus spread, but the data presented are inconsistent and do not provide an unambiguous answer concerning the level of signifcance of potential LSD virus vectors in the progression of the feld epizootic. These papers investigate the ability of gadflies, flies and ticks to act as mechanical vectors. Currently, there is no unequivocal viewpoint with respect to the proved LSD vector. This paper reviews the entomological papers aimed at studying possible LSD virus transmission by arthropods.

Lumpy skin disease virus (LSDV) is a vector-transmitted capripox virus that causes disease in cattle. Stomoxys calcitrans flies are considered to be important vectors as they are able to transmit viruses from cattle with the typical LSDV skin nodules to naive cattle. No conclusive data are, however, available concerning the role of subclinically or preclinically infected cattle in virus transmission. Therefore, an in vivo transmission study with 13 donors, experimentally inoculated with LSDV, and 13 naïve acceptor bulls was performed whereby S. calcitrans flies were fed on either subclinical- or preclinical-infected donor animals. Transmission of LSDV from subclinical donors showing proof of productive virus replication but without formation of skin nodules was demonstrated in two out of five acceptor animals, while no transmission was seen from preclinical donors that developed nodules after Stomoxys calcitrans flies had fed. Interestingly, one of the acceptor animals which became infected developed a subclinical form of the disease. Our results show that subclinical animals can contribute to virus transmission. Therefore, stamping out only clinically diseased LSDV-infected cattle could be insufficient to completely halt the spread and control of the disease.

This study was carried out to explore epidemiological and molecular features of lumpy skin disease virus (LSDV) in the Aegean, Central Anatolian and Mediterranean regions of Turkey, to evaluate the risk factors associated with LSDV infection and to investigate the financial impact of LSD and potential role of the Culicoides spp. in the transmission of LSDV. Samples were obtained from 611 cattle, each from different farms, and each clinically suspected to be infected with LSDV during the months of July 2014 and June 2015. Culicoides spp. were trapped from April to June 2015. Genetic characterization of the local LSDV field isolates was conducted by sequencing G-protein-coupled chemokine receptor gene segment. Real-time PCR high-resolution melting analysis was used for distinguishing each type of capripoxviruses. Viral DNA was detected in 448 of the 611 animals and Culicoides midges. Three hundred and ninety-three of the 448 affected farms were surveyed. The morbidity and mortality rates detected were 12.3% and 6.4%, respectively. Phylogenetic analysis showed that the field isolates in this study were clustered together with other Africa and Middle East isolates. Genotyping of isolates from infected cattle has revealed the presence of LSDV. A generalized mixed linear model showed that there were positive associations between LSDV infection, European breeds, small-sized family-type farms and nearness of farm to a lake. The financial cost of disease presence in surveyed cattle farms was estimated to be 72.75 GBP per head. The sequence analysis of the mitochondrial cytochrome oxidase subunit I gene showed that the species of Culicoides in LSDV-positive pools was Culicoides punctatus. Detection of LSDV in Culicoides punctatus suggests that it may have played a role in transmitting LSDV. Furthermore, movement of infected animals into disease-free areas increases the risk of the transmission of LSD. Control strategies for LSDV infection should include consideration of the risk factors identified in this study.

Detection of lumpy skin disease (LSD) virus and distribution of blood-sucking insects as potential vector in Indonesia.

The vector of lumpy skin disease (LSD), a viral disease affecting Bovidae, is currently unknown. To evaluate the possible vector of LSD virus (LSDV) under field conditions, a yearlong trapping of dipterans was conducted in dairy farms that had been affected by LSD, 1-2 years previously. This was done in order to calculate monthly relative abundances of each dipteran in each farm throughout the year. The relative abundances of Stomoxys calcitrans (Diptera: Muscidae) in the months parallel to the outbreaks (December and April) were significantly higher than those of other dipterans. A stable fly population model based on weather parameters for the affected area was used to validate these findings. Its results were significantly correlated with S. calcitrans abundance. This model, based on weather parameters during the epidemic years showed that S. calcitrans populations peaked in the months of LSD onset in the studied farms. These observations and model predictions revealed a lower abundance of stable flies during October and November, when LSD affected adjacent grazing beef herds. These findings therefore suggest that S. calcitrans is a potential vector of LSD in dairy farms and that another vector is probably involved in LSDV transmission in grazing herds. These findings should be followed up with vector competence studies.

Demonstration of lumpy skin disease virus infection in Amblyomma hebraeum and Rhipicephalus appendiculatus ticks using immunohistochemistry

Lumpy skin disease is an acute, subacute, or asymptomatic viral infection in cattle, marked by fever and the abrupt emergence of hard, confined skin nodules that often undergo necrosis. The 151-kbp LSDV genome has a core coding region flanked by identical 2.4 kbp inverted terminal repeats and includes 156 putative genes. The dissemination of "lumpy skin disease virus" (LSDV) has incited rigorous research initiatives owing to the fast proliferation and significant consequences of the disease in recent years. Disease transmission primarily occurs by insects, sometimes through mechanical vectors, contaminated feed and water, infected saliva, and seldom through natural contact. LSD is prevalent in several African nations and primarily coexists with sheeppox and goatpox. Affected cattle had acute clinical manifestations including dermal nodules, pyrexia, lymphadenopathy, cachexia, and edema of the lower limbs. The disease has proliferated swiftly and extensively over the globe, predominantly in Asian nations and Pakistan. The disease has disseminated by the end of year 2021 in Sindh province Pakistan and then spread across all provinces of Pakistan, affecting large number of cattle and to some extent buffalo also. The purpose of this review is to strengthen and examine the previous as well as the most current research findings on lumpy skin disease virus transmission (vector and non-vector), clinical signs, geographical distribution, and vaccination against this virus.

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.