Experimental evidence of mechanical lumpy skin disease virus transmission by Stomoxys calcitrans biting flies and Haematopota spp. horseflies

Abstract

Lumpy skin disease (LSD) is a devastating disease of cattle characterized by fever, nodules on the skin, lymphadenopathy and milk drop. Several haematophagous arthropod species like dipterans and ticks are suspected to play a role in the transmission of LSDV. Few conclusive data are however available on the importance of biting flies and horseflies as potential vectors in LSDV transmission. Therefore an in vivo transmission study was carried out to investigate possible LSDV transmission by Stomoxys calcitrans biting flies and Haematopota spp. horseflies from experimentally infected viraemic donor bulls to acceptor bulls. LSDV transmission by Stomoxys calcitrans was evidenced in 3 independent experiments, LSDV transmission by Haematopota spp. was shown in one experiment. Evidence of LSD was supported by induction of nodules and virus detection in the blood of acceptor animals. Our results are supportive for a mechanical transmission of the virus by these vectors.

Quantifying and modelling the acquisition and retention of lumpy skin disease virus by haematophagus insects reveals clinically but not subclinically-affected cattle are promoters of viral transmission and key targets for control of disease outbreaks

“…These data were then used to estimate the risk of transmission by these species with the aim of providing evidence with which to inform decisions during the implementation of measures to control LSDV. In our experimental model we observed that 37.5% of calves developed generalised LSD with the remaining 62.5% of calves classified as subclinical (no cutaneous nodules, positive qPCR in blood 27 ). This attack rate of 0.37 is comparable to other experimental models with field strains of LSDV (0.57 27 and 0.50 32 ).…”

“…This study describes a controlled experimental model of LSD that mimics disease features described in field outbreaks 2,4,8,11,12,37 and other experimental models 27,32 . Inoculated calves (both clinical and subclinical) were used to measure the acquisition (transmission from bovine to insect) and retention of LSDV by four potential vector species.…”

“…Three previous studies have investigated the transmission of LSDV from insects to cattle, where insects of species included in the present study were allowed to feed on an infected donor and were subsequently allowed to refeed on a naïve recipient 21,27,29 . The number of positive insects refeeding was not determined in these studies.…”

“…However transmission of LSDV to susceptible 4 of 45animals has not been confirmed for these species. To date the mode of LSDV arthropod transmission has been assumed to be mechanical as no evidence of active virus replication in insects or ticks has been found 30 .LSDV can be detected in skin lesions, blood (primarily in peripheral blood mononuclear cells), and in nasal, oral and ocular excretions of infected cattle 27,31,32 . Viraemia is considered of short duration and relatively low level, though the virus can survive for longer periods of time in skin lesions 31 .…”

“…LSDV can be detected in skin lesions, blood (primarily in peripheral blood mononuclear cells), and in nasal, oral and ocular excretions of infected cattle 27,31,32 . Viraemia is considered of short duration and relatively low level, though the virus can survive for longer periods of time in skin lesions 31 .…”