4 National Institute of Health Research and Development, Jakarta, Indonesia ... in Karachi, Pakistan, one in Kolkata, India, and two in North Jakarta, Indonesia.
Tropical Medicine and International Health
doi:10.1111/j.1365-3156.2010.02553.x
volume 15 no 8 pp 960–963 august 2010
Non-typhoidal Salmonella rates in febrile children at sites in five Asian countries M. Imran Khan1, R. L. Ochiai1, L. von Seidlein1, B. Dong2, S. K. Bhattacharya3, M. D. Agtini4, Z. A. Bhutta5, G. C. Do6, M. Ali1, D. R. Kim1, M. Favorov1 and J. D. Clemens1 1 2 3 4 5 6
International Vaccine Institute, Seoul, Korea Guangxi Centers for Disease Control and Prevention, Guangxi, China National Institute of Cholera and Enteric Diseases, Kolkata, India National Institute of Health Research and Development, Jakarta, Indonesia Department of Paediatrics, Aga Khan University, Karachi, Pakistan National Institute of Hygiene and Epidemiology, Hanoi, Viet Nam
Summary
There is increased recognition of non-typhoidal Salmonella (NTS) as a major cause of severe febrile illness in sub-Saharan Africa. However, little is known about community-based incidence of NTS in Asia. In a multicentre, community-based prospective Salmonella surveillance study, we identified a total of six NTS cases: three in Karachi, Pakistan, one in Kolkata, India, and two in North Jakarta, Indonesia. No NTS cases were identified in Hechi, People’s Republic of China, and Hue, Viet Nam. Three cases were in children under 3 years, and one case was in a child aged 10 years and one in a child aged 15 years. Only one case was an adult (29 years). The highest incidence of NTS infection was in Karachi (7.2 culture-proven NTS cases per 100 000 person years in age group of 2–15 years). However, in comparison with sub-Saharan Africa, the NTS burden in Asia appears rather limited. keywords non-typhoidal Salmonella, disease burden, Asia, invasive disease
Background
Methods
Salmonelloses are infections caused by gram-negative bacteria called Salmonella. Salmonella enterica serovar typhi (S. typhi) and, to a lesser extent, Salmonella enterica serovar paratyphi (S. paratyphi) are the predominant Salmonella serotypes causing infection in urban squatter settlements of Asia, particularly in South Asia (Ochiai et al. 2008). Non-typhoidal Salmonella (NTS) is common both in developed and developing countries (Arshad et al. 2008). In settings where appropriate surveillance mechanism is available; S. typhimurium and S. enteritidis are major NTS serovars isolated. Non-typhoidal Salmonella organisms are most often found in animals, including poultry, livestock, reptiles and pets. Infection with NTS usually presents with mild gastroenteritis (Grisaru-Soen et al. 2004). However, in the developing countries, especially Africa, NTS is a major source of severe clinical illness in children (Graham et al. 2000). Similarly, the rapid increase in the antibiotic resistance of NTS is major public health concern both in the developing and developed world. We therefore analysed population-based data from five sites across Asia to estimate the incidence of NTS infection.
As part of a vaccine trial, fever surveillance was conducted in China, India, Indonesia, Pakistan and Viet Nam (Ochiai et al. 2008). Following a baseline census to collect sociodemographic information of the study population, 12-month surveillance in the five study sites started between August 2001 (in Hechi) and November 2003 (in Kolkata) (Table 1). A total of 441 435 individuals were under surveillance in the five study sites. Target age for surveillance varied across sites as well as the socio-economic and geographic characteristics. In Kolkata and North Jakarta all age groups were included, whereas in Karachi only children 2–16 years old were invited to participate. Surveillance was conducted through the existing health care system, if the system was deemed efficient for the study. In Karachi and Kolkata, the project established study health centres to enrol eligible populations. Private-sector health care providers were included, and a referral system was established to increase the capture rate for febrile episodes at all sites. Details of the surveillance methods are reported elsewhere (Khan et al. 2006; Ochiai et al. 2007). The surveillance targeted cases of fever who lived in the study area. Patients with fever episodes lasting three or
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ª 2010 Blackwell Publishing Ltd
Tropical Medicine and International Health
volume 15 no 8 pp 960–963 august 2010
M. I. Khan et al. Non-typhoidal Salmonella in Asia
Table 1 Distribution and incidence of Salmonella species in 5 settings in Asia
Site
Hechi, China
Kolkata, India
North Jakarta, Indonesia
Karachi, Pakistan
Hue, Viet Nam
Surveillance target age group (years) Target population Mean age (years) Febrile episodes analysed Febrile episodes analysed with blood taken Febrile episodes Incidence (per 1000 population) Typhoid cases Typhoid incidence (per 1000 population) Paratyphoid A cases Paratyphoid A Incidence (per 1000 population) Other (NTS) Salmonella cases Other NTS Salmonella Incidence (per 100 000 population) Malaria cases Malaria Incidence (per 1000 population)
5–60 97 928 31.2 1215 1215 12.4 15 15.3 26 26.6 0 0.0 – –
all ages 56 946 28.6 4378 4342 76.9 122 214.2 63 110.6 1* 1.8 145 2.5
all ages 160 261 26.7 4867 3954 30.4 131 81.7 22 13.7 2 1.0 – –
2–15 41 845 8.5 7736 7415 184.9 189 451.7 32 76.5 3à 7.2 63 1.5
5–18 84 55 12.1 3678 3611 43.5 18 21.3 0 0.0 0 0.0 – –
*Salmonella Group A. Salmonella Group E & C. àSalmonella Group D.
more days were invited to participate in the study, and 3–8 ml of blood was collected in a culture bottle (BACTEC Peds Aerobic for children and BACTEC Aerobic for adults; Becton Dickinson, USA). All Salmonella isolates identified during this study were confirmed at a reference laboratory (University of Oxford, Wellcome Trust Clinical Research Unit, Ho Chi Minh City, Vietnam). The study was approved by the Institutional Review Board of the International Vaccine Institute (Seoul, Korea) and the local ethical committee of each site. Results During 12 months of surveillance, 21 874 febrile episodes were enrolled, of which 20 537 (94%) episodes involved blood taken for culture and microbiological assessment. A total of 6 (
