Experimental infection of common warthogs (Phacochoerus africanus) and bushpigs (Potamochoerus larvatus) with classical swine fever virus. II : a comparative histopathological study

Wild African Suidae, the common warthog (Phacochoerus africanus) and bushpig (Potamochoerus larvatus), were experimentally infected with classical swine fever (CSF) virus following the diagnosis of CSF subtype 2.1 in domestic pigs in South Africa in 2005. No data regarding the susceptibility or potential lesions of these African wild suids are available. Seven subadult warthogs and six bushpigs were captured and infected intranasally with the South African isolate. Two in-contact control animals of the same species in each experiment verified intra-species transmission. Surviving animals were euthanized after 44 days. Formalin-fixed tissue samples collected from them as well as animals euthanized during the trial were evaluated for histological lesions. The warthogs, which were clinically normal throughout the study, developed histological lesions that were inconsistently present and sometimes subtle. Three individuals, including one in-contact control, developed distinct lympho-plasmacytic cuffing in their brains. Subtle lesions included scant lympho-plasmacytic infiltration of various organs, occasionally accompanied by perivascular cuffing. In contrast, the bushpigs developed overt clinical signs similar to CSF in domestic pigs. Four of six animals, including two in-contact controls, died or were euthanized during the trial. On postmortem examination, intestinal necrosis and ulceration, purulent rhinitis and pneumonia were present. Affected animals developed lymphoid necrosis and depletion whilst surviving individuals showed perivascular cuffing in multiple organs. From the present work, we conclude that these wild Suidae are susceptible to CSF virus and intra-species transmission under experimental conditions can occur

Evaluation of a Virus Neutralisation Test for Detection of Rift Valley Fever Antibodies in Suid Sera

Rift Valley fever (RVF) is a vector-borne viral disease of ruminants mainly, and man, characterized by abortions and neonatal deaths in animals and flu-like to more severe symptoms that can result in death in humans. The disease is endemic in Africa, Saudi Arabia and Yemen, and outbreaks occur following proliferation of RVF virus (RVFV) infected mosquito vectors. Vertebrate animal maintenance hosts of RVFV, which serve as a source of virus during inter-epidemic periods remain unknown, with wild and domestic suids being largely overlooked. To address this, we evaluated the virus neutralization test (VNT) for RVF antibody detection in suid sera, as a first step in assessing the role of suids in the epidemiology of RVF in Africa. Testing of experimental and field sera from domestic pigs and warthogs with a commercial RVF competitive antibody ELISA, served as a reference standard against which the VNT results were compared. Results indicate that VNT can detect anti-RVFV antibodies within three days post-infection, has an analytical specificity of 100% and diagnostic sensitivity and specificity of 80% and 97%, respectively. Although labour-intensive and time-consuming, the VNT proved suitable for screening suid sera and plasma for presence of RVFV antibodies in viraemic and recovered animals

A comparative genome analysis of Rift Valley Fever virus isolates from foci of the disease outbreak in South Africa in 2008-2010.

Rift Valley fever (RVF) is a re-emerging zoonotic disease responsible for major losses in livestock production, with negative impact on the livelihoods of both commercial and resource-poor farmers in sub-Sahara African countries. The disease remains a threat in countries where its mosquito vector thrives. Outbreaks of RVF usually follow weather conditions which favour increase in mosquito populations. Such outbreaks are usually cyclical, occurring every 10-15 years. Recent outbreaks of the disease in South Africa have occurred unpredictably and with increased frequency. In 2008, outbreaks were reported in Mpumalanga, Limpopo and Gauteng provinces, followed by 2009 outbreaks in KwaZulu-Natal, Mpumalanga and Northern Cape provinces and in 2010 in the Eastern Cape, Northern Cape, Western Cape, North West, Free State and Mpumalanga provinces. By August 2010, 232 confirmed infections had been reported in humans, with 26 confirmed deaths.To investigate the evolutionary dynamics of RVF viruses (RVFVs) circulating in South Africa, we undertook complete genome sequence analysis of isolates from animals at discrete foci of the 2008-2010 outbreaks. The genome sequences of these viruses were compared with those of the viruses from earlier outbreaks in South Africa and in other countries. The data indicate that one 2009 and all the 2008 isolates from South Africa and Madagascar (M49/08) cluster in Lineage C or Kenya-1. The remaining of the 2009 and 2010 isolates cluster within Lineage H, except isolate M259_RSA_09, which is a probable segment M reassortant. This information will be useful to agencies involved in the control and management of Rift Valley fever in South Africa and the neighbouring countries

Assessment of reproducibility of a VP7 Blocking ELISA diagnostic test for african horse sickness

The laboratory diagnosis of African horse sickness (AHS) is important for: (a) demonstrating freedom from infection in a population, animals or products for trade (b) assessing the efficiency of eradication policies; (c) laboratory confirmation of clinical diagnosis; (d) estimating the prevalence of AHS infection; and (e) assessing postvaccination immune status of individual animals or populations. Although serological techniques play a secondary role in the confirmation of clinical cases, their use is very important for all the other purposes due to their high throughput, ease of use and good cost-benefit ratio. The main objective of this study was to support the validation of AHS VP7 Blocking ELISA up to the Stage 3 of the World Animal Health Organization (OIE) assay validation pathway. To achieve this, a collaborative ring trial, which included all OIE Reference Laboratories and other AHS-specialist diagnostic centres, was conducted in order to assess the diagnostic performance characteristics of the VP7 Blocking ELISA. In this trial, a panel of sera of different epidemiological origin and infection status was used. Through this comprehensive evaluation we can conclude that the VP7 Blocking ELISA satisfies the OIE requirements of reproducibility. The VP7 Blocking ELISA, in its commercial version is ready to enter Stage 4 of the validation pathway (Programme Implementation). Specifically, this will require testing the diagnostic performance of the assay using contemporary serum samples collected during control campaigns in endemic countries