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

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.

Development and validation of a foot-and-mouth disease virus SAT serotype-specific 3ABC assay to differentiate infected from vaccinated animals.

The effective control of foot-and-mouth disease (FMD) requires sensitive, specific and rapid diagnostic tools. However, the control and eradication of FMD in Africa is complicated by, among other factors, the existence of five of the seven FMD virus (FMDV) serotypes, including the SAT-serotypes 1, 2 and 3 that are genetically and antigenically the most variable FMDV serotypes. A key diagnostic assay to enable a country to re-gain its FMD-free status and for FMD surveillance, is the 3ABC or the non-structural protein (NSP) enzyme-linked immunosorbent assay (ELISA). Although many kits are available to detect 3ABC antibodies, none has been developed specifically for the variable SAT serotypes. This study designed a SAT-specific NSP ELISA and determined whether this assay could better detect NSP-specific antibodies from FMDV SAT-infected livestock. The assay's performance was compared to validated NSP assays (PrioCheck®-NSP and IZSLER-NSP), using panels of field and experimental sera, vaccinated and/or infected with FMDV SAT1, SAT2 or SAT3. The sensitivity () of the SAT-NSP was estimated as 76% (70%, 81%) whereas the specificity was 96% (95%, 98%) at a 95% confidence interval. The sensitivity and specificity were comparable to the commercial NSP assays, PrioCheck®-NSP (82% and 99%, respectively) and IZSLER-NSP (78% and 98%, respectively). Good correlations were observed for all three assays.

Foot-and-mouth disease virus serotype SAT1 in cattle, Nigeria.

The knowledge of foot-and-mouth disease virus (FMDV) dynamics and epidemiology in Nigeria and the West Africa subregion is important to support local and regional control plans and international risk assessment. Foot-and-mouth disease virus serotype South African territories (SAT)1 was isolated, identified and characterized from an FMD outbreak in cattle in Nigeria in 2015, 35 years after the last report of FMDV SAT1 in West Africa. The VP1 coding sequence of the Nigerian 2015 SAT1 isolates diverges from reported SAT1 topotypes resulting in a separate topotype. The reporting of a novel FMDV SAT1 strain in the virus pool 5 (West and Central Africa) highlights the dynamic and complex nature of FMDV in this region of Africa. Sustained surveillance is needed to understand the origin, the extent and distribution of this novel SAT1 topotype in the region as well as to detect and monitor the occurrence of (re-)emerging FMDV strains.

Detection and Molecular Characterization of Foot and Mouth Disease Viruses from Outbreaks in Some States of Northern Nigeria 2013-2015.

Control measures for foot and mouth disease (FMD) in Nigeria have not been implemented due to the absence of locally produced vaccines and risk-based analysis resulting from insufficient data on the circulating FMD virus (FMDV) serotypes/strains. In 2013-2015, blood and epithelial samples were collected from reported FMD outbreaks in four states (Kaduna, Kwara, Plateau and Bauchi) in northern Nigeria. FMDV non-structural protein (NSP) seroprevalence for the outbreaks was estimated at 80% (72 of 90) and 70% (131 of 188) post-outbreak. Antibodies against FMDV serotypes O, A, SAT1, SAT2 and SAT3 were detected across the states using solid-phase competitive ELISA. FMDV genome was detected in 99% (73 of 74) of the samples from FMD-affected animals using rRT-PCR, and cytopathic effect was found in cell culture by 59% (44 of 74) of these samples. Three FMDV serotypes O, A and SAT2 were isolated and characterized. The phylogenetic assessments of the virus isolates showed that two topotypes of FMDV serotype O, East Africa-3 (EA-3) and West Africa (WA) topotypes were circulating, as well as FMDV strains belonging to the Africa genotype (G-IV) of serotype A and FMDV SAT2 topotype VII strains. While the serotype O (EA-3) strains from Nigeria were most closely related to a 1999 virus strain from Sudan, the WA strain in Nigeria shares genetic relationship with three 1988 viruses in Niger. The FMDV serotype A strains were closely related to a known virus from Cameroon, and the SAT2 strains were most closely related to virus subtypes in Libya. This study provides evidence of co-occurrence of FMDV serotypes and topotypes in West, Central, East and North Africa, and this has implication for control. The findings help filling the knowledge gap of FMDV dynamics in Nigeria and West Africa subregion to support local and regional development of vaccination-based control plans and international risk assessment.

A Refined Guinea Pig Model of Foot-and-Mouth Disease Virus Infection for Assessing the Efficacy of Antiviral Compounds.

An antiviral containment strategy for foot-and-mouth disease (FMD) outbreaks could support or replace current contingency plans in case of an outbreak in Europe and could spare many healthy animals from being pre-emptively culled. Recently, substantial progress has been made towards the development of small molecule drugs that inhibit FMD virus (FMDV) replication in vitro. For the initial in vivo evaluation of antiviral lead molecules, a refined FMDV-infection model in guinea pigs (GP) is herewith described. This GP model was validated by demonstrating the antiviral effect of T-1105 (an influenza virus inhibitor with reported activity against FMDV). Sixteen animals were orally administered with T-1105 twice daily (400 mg/kg/day) for five consecutive days and inoculated intraplantarly with 100 GPID50 of the GP-adapted FMDV strain O1 Manisa 1 h after the first administration. The efficacy of T-1105 was compared with that of prophylactic vaccination with a highly potent double-oil emulsion-inactivated O1 Manisa vaccine. Ten animals received a single, full (2 ml) cattle vaccine dose and were inoculated 3 weeks later. Fourteen T-1105-treated and all vaccinated GP were completely protected from generalization of vesicular lesions. At 2 dpi, viral RNA was detected in serum of 9/16 T-1105-treated and of 6/10 vaccinated animals. At 4 dpi, viral RNA was detected in serum, organs and oral swabs of half of the T-1105-treated animals and only in the serum of 1/10 of the vaccinated animals. Mean viral RNA levels in serum and organs of T-1105-treated and vaccinated animals were reduced compared to untreated controls (P < 0.01). T-1105 conferred a substantial clinical and virological protection against infection with O1 Manisa, similar to the protection afforded by vaccination. These results validate the suitability of the enhanced GP model for the purpose of initial evaluation of inhibitors of FMDV replication and illustrate the potential of selective inhibitors of viral replication to control FMD outbreaks.

Proof of concept for the inhibition of foot-and-mouth disease virus replication by the anti-viral drug 2'-C-methylcytidine in severe combined immunodeficient mice.

Recent European contingency plans envisage emergency vaccination as an animal-friendly control strategy for foot-and-mouth disease (FMD). Anti-viral drugs may be used as an alternative or complementary measure. We here demonstrate that the nucleoside analogue 2'-C-methylcytidine (2'CMC) protects severe combined immunodeficient (SCID) mice against lethal FMD virus infection. In brief, SCID mice were inoculated with serotype A FMD virus and treated for five consecutive days with 2'CMC. All 15 treated mice remained healthy until the end of the study at 14 days post-infection (dpi). At that time, viral RNA was no longer detected in 13 of 15 treated mice. All eight untreated mice suffered from an acute generalized disease and were euthanized for ethical reasons on average at 4 dpi. These results illustrate the potential of small molecules to control FMD.