Non-typhoidal salmonella: invasive, lethal, and on the loose
Authors: John H Amuasi, Jürgen May
Journal: The Lancet Infectious Diseases (2019)

In The Lancet Infectious Diseases, the GBD 2017 Non-Typhoidal Salmonella Invasive Disease Collaborators1GBD 2017 Non-Typhoidal Salmonella Invasive Disease CollaboratorsThe global burden of non-typhoidal salmonella invasive disease: a systematic analysis for the Global Burden of Disease Study 2017.Lancet Infect Dis. 2019; published online Sept 24. https://doi.org/10.1016/S1473-3099(19)30418-9Google Scholar estimate the global burden of invasive non-typhoidal salmonella disease using Bayesian meta-regression tools. The results show a high but decreasing number of cases since 2005 with a continuously high case fatality rate, consistent with previous estimates. These findings show that serotypes of Salmonella enterica subspecies that cause invasive non-typhoidal salmonella disease are "low-incidence, high-consequence" pathogens.2Belay ED Monroe SS Low-incidence, high-consequence pathogens.Emerg Infect Dis. 2014; 20: 319-321Crossref PubMed Scopus (19) Google Scholar The unique potentiation of mortality from invasive non-typhoidal salmonella disease through HIV infection, malnutrition, and malaria,3Crump JA Heyderman RS A perspective on invasive salmonella disease in Africa.Clin Infect Dis. 2015; 61: S235-S240Crossref PubMed Scopus (56) Google Scholar has further prompted investigation into the burden of this infectious disease in recent times to inform measures for mitigation. The estimates are an important addition to the sparse literature on invasive non-typhoidal salmonella disease. The most recent estimate of disease burden involved information from only ten studies, of which 70% were from Africa.4Ao TT Feasey NA Gordon MA Keddy KH Angulo FJ Crump JA Global burden of invasive nontyphoidal salmonella disease, 2010.Emerg Infect Dis. 2015; 21: 941-949Crossref Scopus (309) Google Scholar Most of the 66 studies contributing to the GBD 2017 estimates still come from Africa, with a few from Asia and none from Latin America. The paucity of data, particularly from the Indian subcontinent, which shares many of the risk factors for invasive non-typhoidal salmonella disease with Africa (eg, urbanisation with large populations living in crowded and insanitary conditions with poor access to potable water), is one of several clear indications of the need for more epidemiological research on invasive non-typhoidal salmonella disease. However, estimates of the burden of invasive non-typhoidal salmonella disease have as yet not been able to account for several other potentially important influences, such as exposure to neglected tropical diseases, as well as influenza and other viral diseases. Recent work has further shown the potential role of the microbiota in invasive salmonellosis.5Libertucci J Young VB The role of the microbiota in infectious diseases.Nat Microbiol. 2019; 4: 35-45Crossref PubMed Scopus (168) Google Scholar, 6Zhang Y Brady A Jones C et al.Compositional and functional differences in the human gut microbiome correlate with clinical outcome following infection with wild-type Salmonella enterica serovar Typhi.mBio. 2018; 9: e00686-e00718PubMed Google Scholar Living in close proximity to a farm and other domestic animals, using animal faeces as manure in subsistence farming, watering of crops with water from drains and other contaminated water sources, along with unhygienic slaughtering of animals and meat processing are common practices in many developing countries. These factors might vary widely and be independent to access to safe drinking water. Global measures of these factors do not exist, but they might substantially affect the global burden of invasive non-typhoidal salmonella disease and therefore have implications for efforts to develop and deliver effective vaccines against the disease. These considerations make invasive non-typhoidal salmonella disease, which is caused by serovars for which both humans and animals are host species, an important infectious disease requiring a One Health approach for an effective reduction in burden, as is being pursued by WHO.7WHOSalmonella (non-typhoidal).https://www.who.int/news-room/fact-sheets/detail/salmonella-(non-typhoidal)Date: Feb 20, 2018Date accessed: August 13, 2019Google Scholar Without adequate, geographically representative, epidemiological mapping of invasive non-typhoidal salmonella disease and investigation into the sources and transmission pathways of the disease, estimations of the global disease burden might continue to change with very wide margins. Making appropriate global health policy recommendations towards control of invasive non-typhoidal salmonella disease that are relevant to various regions and countries is challenging in the face of varying estimates. Around 6 years ago, less than 5% of clinically important infectious diseases were considered to have been mapped reliably.8Hay SI Battle KE Pigott DM et al.Global mapping of infectious disease.Philos Trans R Soc B Biol Sci. 2013; 368: 20120250Crossref PubMed Scopus (147) Google Scholar Within Africa, for example, a recently published article on Kenya9Frings M Lakes T Müller D et al.Modeling and mapping the burden of disease in Kenya.Sci Rep. 2018; 8: 1-9Crossref PubMed Scopus (9) Google Scholar was the first, and is likely to be the only study to date, to use subnational data on premature mortality across an entire country to systematically assess the spatial patterns of disease burden, taking into consideration the risk of infectious diseases and environmental and sociodemographic factors. This study showed significant spatial clusters of high numbers of years of life lost (YLLs) to premature mortality subnationally, with crowded households showing strongest associations with YLLs.9Frings M Lakes T Müller D et al.Modeling and mapping the burden of disease in Kenya.Sci Rep. 2018; 8: 1-9Crossref PubMed Scopus (9) Google Scholar Such findings have important implications for targeting not only health but also other national policies. Now, more than ever, innovative applications of internet and mobile phone technology and infrastructure enable us to collect, share, and use new data to rapidly improve our knowledge of the burden of a wide range of infectious diseases in an increasingly accurate and efficient manner. No vaccine against non-typhoidal salmonella disease is available for use in humans. However, by contrast with many other vaccine-preventable diseases, non-typhoidal salmonella disease has clearly defined major risk factors that are preventable through relatively simple solutions compared with vaccine development and deployment. Death from invasive non-typhoidal salmonella disease is usually due to delayed diagnosis and delayed treatment or treatment with inappropriate antibiotics. Particularly in developing countries, multidrug-resistant and even extensively drug-resistant salmonella serotypes10Chatham-Stephens K Medalla F Hughes M et al.Emergence of extensively drug-resistant Salmonella Typhi infections among travelers to or from Pakistan—United States, 2016-–2018.MMWR Morb Mortal Wkly Rep. 2019; 68: 11-13Crossref PubMed Google Scholar further compound the persistent high case fatality from invasive non-typhoidal salmonella disease. This threat raises the need for not only diagnostics to identify infection but also blood culture and sensitivity investigations to be available as part of routine clinical care and public health surveillance. We declare no competing interests. The global burden of non-typhoidal salmonella invasive disease: a systematic analysis for the Global Burden of Disease Study 2017We present the first global estimates of non-typhoidal salmonella invasive disease that have been produced as part of GBD 2017. Given the high disease burden, particularly in children, elderly people, and people with HIV infection, investigating the sources and transmission pathways of non-typhoidal salmonella invasive disease is crucial to implement effective preventive and control measures. Full-Text PDF Open Access