Abstract
.Although typhoid is endemic to Southeast Asia, very little is known about the disease in Laos. Typhoid vaccination is not included in the national immunization program. Although sanitation has improved, one million people still do not have access to basic clean water sources. We describe the epidemiology and antimicrobial susceptibility patterns of Salmonella enterica serovar Typhi (S. Typhi) infection in Laos based on isolates accrued over 18 years at Mahosot Hospital, Vientiane. All blood cultures collected from patients presenting with fever submitted to the Microbiology Laboratory at Mahosot Hospital (February 2000–December 2018) were included. This included patients from Vientiane and four provincial hospitals and one typhoid outbreak investigation. A total of 913 (1.5%) of 60,384 blood cultures were positive for S. Typhi. The majority of isolates with data available (712/898, 79.3%) were susceptible to all antibiotics tested, with 59 (6.5%) multidrug-resistant (MDR) isolates, mostly from one outbreak. Of 854 isolates, 12 (1.4%) were fluoroquinolone resistant. Patient admissions peaked between March and June at the end of the dry season. Although there are key limitations, these data give the first detailed epidemiological evidence of typhoid in Laos. However, estimates will be greatly influenced by access to blood culture services and health-seeking behavior. Although typhoid multidrug resistance and fluoroquinolone resistance are not currently major issues in Laos, continued surveillance and improved antibiotic stewardship are necessary to forestall worsening of the situation. Cost-effectiveness analysis is needed to inform decisions regarding typhoid vaccine introduction.
Highlights
Typhoid, caused by Salmonella enterica serovar Typhi
There were differences between provinces in the main water source for villages in 2015, with Vientiane Capital and Vientiane Province predominantly using bottled water (398/481 villages, 82.7% and 250/434 villages, 57.6%, respectively), whereas in Luang Namtha, majority of the people (258/362, 71.3%) sourced their water from mountain-fed water sources. These data from blood cultures received in a single hospital from diverse parts of Laos provide a minimal estimate of inpatient culture-positive typhoid incidence, with the most recent annual incidence in 2018 of 0.59 cases per 100,000 people
This estimate of annual incidence of hospitalized typhoid is a significant underestimate of the true incidence of the disease in the community as few hospitals have blood culture facilities and not all typhoid patients will access hospitals or will be admitted
Summary
Typhoid, caused by Salmonella enterica serovar Typhi Typhi), is transmitted through contaminated food and water and is estimated to cause > 10 million illnesses and 128,000 deaths annually worldwide.[1,2] Salmonella enterica serovar Typhi is an important cause of community-acquired bacteremia in South and Southeast Asia. Thailand reported a decrease in cases from 8.6 cases/100,000 people in 2003 to 3/100,000 people in 2014,3 and Vietnam has reported a continued decline from an estimated incidence of 14.7/100,000 people in 2003.4 Immunization programs were started in Thailand in the 1970s and Vietnam in the 1990s, which may have led to these decreases in case burden.[3,4] The role that water, sanitation, and hygiene initiatives and economic growth have had in this decline is difficult to judge, they have probably played a major role. The WHO has long recommended immunization for people living in endemic areas and has recently advised the use of a new prequalified typhoid conjugate vaccine.[5]
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