Abstract
Over the last two decades, the pig population in Africa has grown rapidly, reflecting the increased adoption of pig production as an important economic activity. Of all species, pigs are likely to constitute a greater share of the growth in the livestock subsector. However, constraints such as respiratory infectious diseases cause significant economic losses to the pig industry worldwide. Compared to industrialized countries, the occurrence and impacts of respiratory diseases on pig production in Africa is under-documented. Hence, knowledge on prevalence and incidence of economically important swine respiratory pathogens in pigs in Africa is necessary to guide interventions for prevention and control. The purpose of this review was to document the current status of research on five important respiratory pathogens of swine in Africa to inform future research and interventions. The pathogens included were porcine reproductive and respiratory syndrome virus (PPRSv), porcine circovirus 2 (PCV2), Mycoplasma hyopneumoniae (M. hyopneumoniae), Actinobacillus pleuropneumoniae (APP) and swine influenza A viruses (IAV). For this review, published articles were obtained using Harzing’s Publish or Perish software tool from GoogleScholar. Articles were also sourced from PubMed, ScienceDirect, FAO and OIE websites. The terms used for the search were Africa, swine or porcine, respiratory pathogens, M. hyopneumoniae, APP, PCV2, PPRSv, IAV, prevention and control. In all, 146 articles found were considered relevant, and upon further screening, only 85 articles were retained for the review. The search was limited to studies published from 2000 to 2019. Of all the studies that documented occurrence of the five respiratory pathogens, most were on IAV (48.4%, n = 15), followed by PCV2 (25.8%, n = 8), PPRSv (19.4%, n = 6), while only one study (3.2%, n = 1) reported APP and M. hyopneumoniae. This review highlights knowledge and information gaps on epidemiologic aspects as well as economic impacts of the various pathogens reported in swine in Africa, which calls for further studies.
Highlights
Pig production accounts for a large share of growth in the livestock subsector worldwide [1]
Inclusion and exclusion criteria Based on the reported economic importance for the swine industry, five key swine respiratory disease pathogens were identified: M. hyopneumoniae, Actinobacillus pleuropneumoniae (APP), porcine circovirus 2 (PCV2), PRRSv and influenza A viruses (IAV)
Of the 85 papers retained, only 41 (48.2%) studies reported the occurrence of selected respiratory pathogens in swine and of the 41 studies, only 16 (39%) demonstrated the actual occurrence of selected pathogens, while most studies 25 (61%) were based on serologic assays, suggesting exposure of pigs to these pathogens or closely related strains
Summary
Pig production accounts for a large share of growth in the livestock subsector worldwide [1]. The growing global human population creates an increased demand for animal source foods To meet this demand, pigs are one of the preferred species due to their efficient feed conversion and fast growth rates [1]. While pig production offers opportunities for both commercial and smallholder producers, the industry faces several constraints [5, 6] Transboundary diseases such as African swine fever (ASF) pose a threat to international trade, livelihoods and food security due to high economic impacts. Besides ASF, respiratory pathogens such as PPRSv, PCV2, M. hyopneumoniae, APP and IAV are likely to play an important role, given experiences from industrialized systems These diseases account for economic losses [6–8] due to mortalities, reduced growth, poor feed conversion and reproductive (2020) 6:5 performance [9], their impacts on Africa’s predominantly extensive smallholder pig production systems is unexplored and unknown
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