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

Abstract

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.

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

“…The LSDV, Saratov/2017, was the first of many novel recombinants between vaccine-derived parental strains to be isolated from active LSD outbreaks in the field in Russia, Kazakhstan and China ( 18 ). Subsequent experiments using Saratov/2017 provided evidence that this recombinant vaccine-like strain is capable of infecting bulls via indirect contact and virus-inoculated feed, i.e., via the alimentary route, thus corroborating its contagious nature and resembling the transmission pathway described in the majority of poxviruses ( 16 , 19 , 20 ).…”

“…It is therefore imperative that the different phenotypic characteristic between the novel recombinant strains as well as the differences between the recombinants and the classical strains be identified in order to link future targeted mutational genotypes to these phenotypes. In a previous experiment, virulent Saratov/2017 with the genomic backbone of a Neethling commercial vaccine, first demonstrated the potential for non-vector borne transmission and in a subsequent study it was shown to cause a mild infection via the alimentary route ( 19 ). By contrast, Udmurtiya/2019 with the genomic backbone of a Kenyan vaccine strain KSGP showed a similar characteristic.…”

Genomic characterization of Lumpy Skin Disease virus (LSDV) from 2019 outbreak in India reveals circulation of Kenyan-like LSDV strains with unique kelch-like proteins

“…Kenyan strains have caused outbreaks in Kenya, but however never been reported in subsequent epidemics in Africa, the Middle East, and Europe (Tulman et al, 2001). Since 2017, recombinant LSDV strains have been detected in infected cattle in Russia (Sprygin et al, 2018;Sprygin et al, 2020;Shumilova et al, 2022); Krotova et al, 2022a), China (Ma et al, 2021), Hongkong (Flannery et al, 2021), Taiwan (Huang et al, 2022) and Vietnam (Mathijs et al, 2021;Tran et al, 2021). In phylogenetic analysis, recombinant strains formed four monophyletic groups R1, R2, R3, and R4 as described in section 3.3.…”

“…These recombinant LSDV strains have demonstrated an increase in virulence as compared to other field LSDV strains and can be transmitted in vector-independent mode (Aleksandr et al, 2020;Kononov et al, 2020). Even, LSDV-Saratov/19 has been demonstrated to persist in winter in absence of vectors through direct contact or fomites (Shumilova et al, 2022). LSDV has also been reported in a giraffe in Vietnam which is closely related to recombinant Vietnamese LSDV strains (Dao et al, 2022).…”

The genome sequence of the Lumpy Skin Disease virus from the outbreak in India suggests a distinct lineage of the virus

“…Lumpy Skin Disease (LSD) is a virus disease of cattle, with significant morbidity and mortality. The disease is characterised by nodular skin lesions evident as lumps along with lymphadenopathy, with severe cases resulting in the death of the affected animal (Shumilova et al, 2022). The morbidity rate in LSD varies widely from 50–100% (Tuppurainen and Oura, 2012).…”