Brief  26  More meat, milk and fish by and for the poor December 2016 Pig vaccines and diagnostics for African swine fever: the case of Uganda Lucilla Steinaa, Richard Bishop, Edward Okoth, Nicholas Svitek and Victor Riitho (ILRI) Key messages transmitted indirectly through fomites, through soft ticks and the virus can be maintained in through a wildlife cycle.  Rapid diagnostics for African swine fever in In endemic areas such as in sub-Saharan Africa, an added outbreak areas and sensitive diagnostics for risk to the spread of the disease is the underreporting of detecting chronical infected pigs are needed for outbreaks. A vaccine could provide a means of controlling the control of the disease. the disease in areas prone to outbreaks and high quality  A vaccine for African swine fever could greatly diagnostic tools would prevent outbreak response delays. enhance the control of the disease in sub-Saharan Africa where the large-scale use of strict biosecurity measures are unfeasible. African swine fever (ASF) is a haemorrhagic fever affecting  Collaboration between International Livestock pigs. If introduced into a farm, it can kill all the animals Research Institute (ILRI) and Friedrich Loefler within a few days. It is a large DNA virus and the only Institute, the first of its kind in the field of ASF member of Asfaviridae family, but has similarities with the vaccinology/vaccine development between these pox viruses, such as chicken pox and goat pox, among organizations, has been very valuable in starting others. The virus is initially found in cells of the up activities in this area and this work is now macrophage type; but in the later phases of the disease, it followed up in a new project. also infects other cell types such as epithelial cells. Distinct clinical symptoms are high fever, redness (haemorrhage) of Infectious livestock diseases have a huge negative impact on the the ears and on other patches of the skin, and death. incomes of resource-poor farmers and the development of national economies. In developing countries, meat consumption Unfortunately, there are no available commercial vaccines has increased by 6% annually over the last five decades and this or treatment to control or prevent ASF virus infection. trend is rising. Pigs are among the most profitable livestock for The only method of preventing ASF is by using strict poor farmers and pig farming is recognized as means of biosecurity methods, e.g. fencing of animals, avoiding increasing food security and smallholder livelihoods (Costard et contact with wild pigs, washing of boots before entering al. 2009), particularly of women and young people in sub- pig enclosures, use of quarantine pens for new animals, etc. Saharan Africa who are disproportionately involved in pig Compartmentalization and zoning of pig herds can be used farming due to cultural norms. to keep areas ASF-free; however, this approach can be However, the viability of pig farming is constantly difficult to introduce and maintain on a large-scale in Africa threatened by viral diseases; one of the most deadly and as pigs often roam freely in rural and peri-urban systems. devastating, African swine fever (ASF) virus, seriously threatens food security and impedes development. Some Moreover, poor African pig producers are less likely to viral genotypes can cause up to 100%, and less virulent implement control strategies or report disease outbreaks strains between 30–70% mortality. ASF is a very acute because of a lack of knowledge and incentives to do so. disease with death from virulent strains occurring between Therefore, this disease poses serious socio-economic 6 and 13 days post-infection. From 2009–2011, ASF was consequences in affected and nearby countries and reported in 26 African countries (Penrith et al. 2013). highlights the urgency of developing efficient When it spread to Ivory Coast and Madagascar, ASF countermeasures against ASF. With an estimated 34 decimated 30–50% of the national pig population (el million pigs in sub-Saharan Africa, an ASF vaccine could Hicheri et al. 1998; Roger et al. 2001). Recent outbreaks in benefit from 6–17 million smallholder farmers, providing the Russian Federation caused losses of approximately protection in cases of generalized outbreaks and USD 1 billion (FAO 2013) and the virus has now spread to preventing outbreaks in nearby areas. As the pig other eastern European countries. The epidemiology of population in Africa rises, disease spread could be ASF is complex. The most efficient transmission is direct increasingly problematic. contact between pigs, but the disease can also be 1 Towards an African swine fever African swine fever diagnostics vaccine A number of commercial diagnostic platforms are available for the detection of ASF (Agüero et al. 2003; King et al. ILRI scientists recently initiated work on the development 2003; Agüero et al. 2004; Zsak et al. 2005; Tignon et al. of an ASF vaccine. In collaboration with the Friedrich 2011; OIE, 2012; Fernández et al. 2013; Haines et al. Loeffler Institute (FLI), scientists involved in the CGIAR 2013), but they have not been widely validated in the Research program on Livestock and Fish attempted to African context. Confirmation of ASF outbreaks in Africa generate an attenuated vaccine—reducing the virulence of can take up to three weeks from the moment symptoms a pathogen, but still keeping it alive, by a method known as are initially observed and field samples collected to di-codon deoptimization. Though the approach has been laboratory confirmation of infected pigs. This delay has reportedly successful in slowing down the speed of virus serious consequences in terms of increasing the risk of the growth (Nouen et al. 2014), it was not so when based on further spread of the disease while diagnosis is being the major capsid protein p72 from the virus. The work is confirmed. Rather than wait for their herds to be ongoing to broaden the approach to include other genes slaughtered as a biosecurity measure, farmers tend to sell from the virus. sick pigs in the market at the first hint of an ASF outbreak. Instead, two modified viruses were developed based on An ASF rapid diagnostic test, in the form of a pen-side/ the deletion of the gene CD2v—a gene involved in the point-of-care test that is suitable for use in African village- attachment of the virus to the host cells. This was done in level pig production environments would greatly reduce two different genotype backgrounds, genotype I and the diagnosis time lag to less than one hour, greatly genotype IX. The modified viruses are now ready to be reducing associated costs and increasing the efficiency of tested in animal experiments. ILRI then employed the disease control. To this end scientists have evaluated the necessary laboratory methods for immunological and use of a rapid diagnostic approach using TETRACORE, a virological ASF work, including developing an animal model commercial real-time polymerase chain reaction (PCR) using a Kenyan genotype IX isolate. (Zsak et al. 2005; LeBlanc et al. 2013). The test is applicable at the point of care and has proved useful in the Scientists also designed a way of inducing immunity to the early confirmation of outbreaks in Kenya and Uganda. same virulent strain by using a sequential immunization schedule with increasing doses. In this way, five pigs Standardised ASF diagnostic tests tailored for local treated were rendered immune when subjected to a lethal application are currently lacking (Okoth et al. 2013). Based dose of ASF virus (Riitho et al. in preparation). This is a new on recent studies in East Africa, diagnostic platforms way of inducing ASF immunity. It may prove very useful as addressing various scenarios are needed: epidemiological it has been reported that attenuated viruses sometimes situations that vary from acute to chronic infections; mixed change the genome substantially, as well as the disease infections from diseases with ASF-like clinical signs that pattern and immunological responses (Takamatsu et al. confound diagnosis; a range of samples available to confirm 2013). diagnosis including blood, serum, oral fluids, tissue exudates and internal organs; host characteristics that Scientists have also sequenced new indigenous pig MHC influence performance e.g. absence of neutralizing class I molecules1 (Ilsoe et al. submitted). MHC molecules antibodies to ASF virus; and virus genotypes including from the pig bind the T-cell epitopes; this complex is then virulent and avirulent strains. recognized by the immune cells. The MHC class I molecules have never been defined in indigenous pigs in Studies have shown that PCR tests are suitable for early Africa, and this is important for developing vaccines detection of the ASF virus genome during epidemics comprising particular proteins/genes when a cellular (Gallardo et al. 2009; 2011). However, specific tests should response, including T cells is needed. An additional 33 pig be matched with their robustness in pigs with low levels of samples are currently being sequenced. the virus, especially in endemic areas. Due to the limited sensitivity of some ELISA tests in samples with low Furthermore, efforts are ongoing to improve antibody titres (Okoth et al. 2013), improved serological bioinformatics tools for predicting T-cell epitopes together tests are needed that can detect antibodies within a short with University of Copenhagen and Danish Technical period post infection. University. So far, three swine leucocyte antigen (SLA) molecules have been expressed and produced by Proof-of-concept and standardisation of the diagnostic University of Copenhagen, and they are in the process of products and associated assay protocols will inform actors being tested for binding of peptides from a random peptide in ASF surveillance, enhancing adoption and application of library. The resultant data will be analysed and used for relevant disease-control technologies in Africa. The target neural network training for the NetMHCpan program for ASF diagnostic products profile and standardized assay prediction of CTL epitopes. This will then improve the protocols suitable for disease surveillance in East Africa programs performance on predicting new CTL epitopes in are currently being evaluated. This new knowledge on the context of SLAs. product profiles for effective ASF diagnostics will result in the appropriate targeting of a panel of diagnostics needed for early detection of the disease in African village-level pig production systems to identify index cases of ASF, followed by rapid response and control. 1 MHC molecules are tissue type antigens (swine leucocyte antigens  (SLAs) from pigs) which bind the T cell epitopes.  2 Conclusions Acknowledgements African swine fever, is a devestaing disease which can This brief was produced as part of a synthesis activity of decimate whole herds of pigs when introduced, impacting the CGIAR Research Program on Livestock and Fish. It negatively on the livelihoods and economy of smallholder focuses on work on livestock health carried out between farmers in Africa. 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