A scoping review of viral diseases in African ungulates

Abstract

Rationale: Viral diseases are important in the African context as they cause significant clinical disease in both wild and domestic animals, as well as in humans. Viral diseases make up a large proportion of emerging infectious diseases. The management and prevention of these diseases have proven to be challenging due to the large population of reservoir hosts consisting of African wildlife. There is no comprehensive publication investigating viruses in African ungulates. Hence, this research study will provide comprehensive analyses to add to the current global knowledge base and provide guidance about areas where there is little information. Aim of the study: Provide a scoping review of viral diseases, which occur in free-ranging African ungulates and identify knowledge gaps with regards to these diseases. Objectives: 1. List and describe viruses diagnosed in free-ranging African ungulates 2. Identify ungulates affected by viruses 3. Describe the geographical distribution of viruses 4. Identify viruses which appear to be “under-studied” Study design: This is a scoping review of peer reviewed publications pertaining to viruses and viral diseases in African ungulates. The methodology for this scoping review was based on the guidelines set out in the PRISMA extension for scoping reviews. A search string was developed and run in three major databases, namely Scopus, Web of Science and Wildlife and Ecology Worldwide, to obtain publications relevant to the research topic. Publications were screened using predetermined inclusion and exclusion criteria to obtain a final set of publications to undergo data extraction and analysis. Results: The final set of publications consisted of 145 publications. A total of 32 viruses were identified in the publications. The range of the publication dates were from 1957 to 2018. Nine out of 32 viruses accounted for 74% of the total reports of viruses detected by antigen/antibody testing in African ungulates. African elephant polyomavirus 1 was the only virus that was solely detected in captive animals according to published literature using antigen/antibody detection. A total of 50 African ungulates were reported/diagnosed with viral infections. The four most frequently mentioned African ungulates in publications reporting on viruses or viral diseases, in descending order, were the African buffalo, blue wildebeest, impala and warthog (common and desert). Of the 52 countries on the African continent, only 18 countries (35%) had viruses diagnosed in wild ungulates reported in the literature. All the publications in this study reported on viruses or viral diseases in ungulates from only sub-Saharan Africa. Foot-and-mouth disease, African swine fever, Rift Valley fever, bluetongue and rabies were frequently reported in the literature. On the contrary, lumpy skin disease, peste des petits ruminants, African horse sickness, enzootic hemorrhagic disease, bovine viral diarrhoea, infectious bovine rhinotracheitis/infectious pustular vulvovaginitis, equine influenza, equine viral arteritis, equine viral rhinopneumonitis and classical swine fever were infrequently reported on. Conclusion: There are a variety of viruses which have been diagnosed in African ungulates and all African ungulates identified have had one or more viruses or viral diseases associated with them. The findings will be valuable to policymakers, funding bodies, researchers and other stakeholders who need an understanding of viral diseases in African ungulates. Research opportunities in this field will allow them to make informed decisions about investment in future research projects and animal health policies and protocols. It is recommended that governments and research institutions offer more funding to investigate and report viral diseases of greater clinical and zoonotic significance, such as rabies and Rift Valley fever. This is especially important in the current climate of emerging diseases and the related overflow of disease from wild to domestic animals and from animals, both wild and domestic, to humans. A further recommendation is for appropriate One Health approaches to be adopted for investigating, controlling, managing and preventing diseases (Cunningham et al., 2017). This is especially true for diseases such as African swine fever and Rift Valley fever where human actions, poor biosecurity and natural weather changes play a major role in the transmission of diseases (Cunningham et al., 2017, Penrith et al., 2019a, Swanepoel and Coetzer, 2004). Diseases which may threaten the conservation of certain wildlife species also require focused attention. In order to keep track of these diseases it may be necessary to consider adding a “wildlife” category to the OIE-listed diseases. Viral diseases, as a whole, are of great significance and require extra attention in the future as they make up a large proportion of emerging infectious diseases and can often infect multiple hosts (Bengis et al., 2004, Cleaveland et al., 2001). Hence, the viruses and viral diseases diagnosed in African ungulates are of significance, particularly at the wildlife/livestock interface and many of them have the potential of becoming emerging wildlife diseases.