Characterisation of putative immunomodulatory gene knockouts of lumpy skin disease virus in cattle towards an improved vaccine.

Lumpy skin disease virus (LSDV) is responsible for causing severe economic losses to cattle farmers throughout Africa, the Middle East, and more recently, South-Eastern Europe and Russia. It belongs to the Capripoxvirus genus of the Poxviridae family, with closely related sheeppox and goatpox viruses. Like other poxviruses, the viral genome codes for a number of genes with putative immunomodulatory capabilities. Current vaccines for protecting cattle against lumpy skin disease (LSD) based on live-attenuated strains of field isolates passaged by cell culture, resulting in random mutations. Although generally effective, these vaccines can have drawbacks, including injection site reactions and/or limited immunogenicity. A pilot study was conducted using a more targeted approach where two putative immunomodulatory genes were deleted separately from the genome of a virulent LSDV field isolate. These were open reading frame (ORF) 005 and ORF008, coding for homologues of an interleukin 10-like and interferon-gamma receptor-like gene, respectively. The resulting knockout constructs were evaluated in cattle for safety, immunogenicity and protection. Severe post-vaccinal reactions and febrile responses were observed for both constructs. Two calves inoculated with the ORF008 knockout construct developed multiple lesions and were euthanised. Following challenge, none of the animals inoculated with the knockout constructs showed any external clinical signs of LSD, compared to the negative controls. Improved cellular and humoral immune responses were recorded in both of these groups compared to the positive control. The results indicate that at the high inoculation doses used, the degree of attenuation achieved was insufficient for further use in cattle due to the adverse reactions observed.

Prevalence of antimicrobial resistance from bacterial culture and susceptibility records from horse samples in South Africa.

The continuous increase in prevalence of antimicrobial resistant bacteria presents a significant public health problem and is an indicator that antimicrobial prudent usage guidelines are not being followed, especially in developing countries. Despite trends being available from numerous countries, there is little published for South Africa. This study was aimed at estimating the prevalence and trends of antimicrobial resistance from bacterial isolates from equine clinical samples submitted for culture and susceptibility testing to the veterinary bacteriology laboratory of the University of Pretoria. The study covered a period of seven years from 2007. A total of 1505 bacterial isolates were included in this study comprising isolates from 2007 (n=447); 2008 (n=285); 2009 (n=258); 2010 (n=102); 2011 (n=89); 2012 (n=248) and 2013 (n=76). For this study, multiple drug resistance was above 50% for all the isolates. The Cochran-Armitage test showed evidence of a significantly increasing trend in prevalence of resistance to several antimicrobial agents, including amikacin (E. coli, Staphylococcus), AMX/AMP (Corynebacteria, Lactobacillus and Salmonella), chloramphenicol (Enterococcus, E. coli, Pseudomonas, Streptococcus, Staphylococcus and Salmonella), enrofloxacin (E. coli, Staphylococcus, Salmonella and Pseudomonas) and gentamicin (Salmonella, Staphylococcus). The data obtained from this study is relevant to equine practitioners, as it helps enhance the body of veterinary knowledge pertaining to antimicrobial resistance in common equine pathogens in South Africa.

Peste des petits ruminants virus tissue tropism and pathogenesis in sheep and goats following experimental infection.

Peste des petits ruminants (PPR) is a viral disease which primarily affects small ruminants, causing significant economic losses for the livestock industry in developing countries. It is endemic in Saharan and sub-Saharan Africa, the Middle East and the Indian sub-continent. The primary hosts for peste des petits ruminants virus (PPRV) are goats and sheep; however recent models studying the pathology, disease progression and viremia of PPRV have focused primarily on goat models. This study evaluates the tissue tropism and pathogenesis of PPR following experimental infection of sheep and goats using a quantitative time-course study. Upon infection with a virulent strain of PPRV, both sheep and goats developed clinical signs and lesions typical of PPR, although sheep displayed milder clinical disease compared to goats. Tissue tropism of PPRV was evaluated by real-time RT-PCR and immunohistochemistry. Lymph nodes, lymphoid tissue and digestive tract organs were the predominant sites of virus replication. The results presented in this study provide models for the comparative evaluation of PPRV pathogenesis and tissue tropism in both sheep and goats. These models are suitable for the establishment of experimental parameters necessary for the evaluation of vaccines, as well as further studies into PPRV-host interactions.