A cross-sectional seroepidemiological survey of typhoid fever in Fiji

• Published in: PLoS neglected tropical diseases 2017-07, Vol.11 (7), p.e0005786
• Main Authors: Watson, Conall H, Baker, Stephen, Lau, Colleen L, Rawalai, Kitione, Taufa, Mere, Coriakula, Jerimaia, Thieu, Nga Tran Vu, Van, Tan Trinh, Ngoc, Dung Tran Thi, Hens, Niel, Lowry, John H, de Alwis, Ruklanthi, Cano, Jorge, Jenkins, Kylie, Mulholland, E Kim, Nilles, Eric J, Kama, Mike, Edmunds, W John
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Age; Age Distribution; Age factors; Aged; Agglutination tests; Antibodies, Bacterial - blood; Antigens; Biology and Life Sciences; Care and treatment; Child; Child, Preschool; Clinical medicine; Cross sections; Cross-Sectional Studies; Data processing; Demography; Disease control; Disease transmission; Dosage and administration; Epidemiology; Ethnicity; Exposure; Female; Fever; Fiji - epidemiology; Funding; Health; Hospitals; Housing; Humans; Hygiene; Immunoglobulin G; Immunoglobulin G - blood; Incidence; Infant; Infections; Infectious diseases; Latrines; Logistic Models; Logistic regression; Male; Management; Medicine; Medicine and Health Sciences; Middle Aged; Minority & ethnic groups; Multivariate Analysis; Odds Ratio; Outbreaks; People and Places; Prevalence studies (Epidemiology); Public health; Regression analysis; Regressions; Research and Analysis Methods; Salmonella; Salmonella typhi; Sanitation; Seroepidemiologic Studies; Seroepidemiology; Sex Distribution; Socioeconomic Factors; Software; Supervision; Surveillance; Surveying; Surveys and Questionnaires; Transmission; Tropical diseases; Typhoid; Typhoid fever; Typhoid Fever - epidemiology; Vaccination; Vaccination - statistics & numerical data; Vaccines; Waterborne diseases; Young Adult
• ISSN: 1935-2735; 1935-2727; 1935-2735
• DOI: 10.1371/journal.pntd.0005786

Fiji, an upper-middle income state in the Pacific Ocean, has experienced an increase in confirmed case notifications of enteric fever caused by Salmonella enterica serovar Typhi (S. Typhi). To characterize the epidemiology of typhoid exposure, we conducted a cross-sectional sero-epidemiological survey measuring IgG against the Vi antigen of S. Typhi to estimate the effect of age, ethnicity, and other variables on seroprevalence. Epidemiologically relevant cut-off titres were established using a mixed model analysis of data from recovering culture-confirmed typhoid cases. We enrolled and assayed plasma of 1787 participants for anti-Vi IgG; 1,531 of these were resident in mainland areas that had not been previously vaccinated against S. Typhi (seropositivity 32.3% (95%CI 28.2 to 36.3%)), 256 were resident on Taveuni island, which had been previously vaccinated (seropositivity 71.5% (95%CI 62.1 to 80.9%)). The seroprevalence on the Fijian mainland is one to two orders of magnitude higher than expected from confirmed case surveillance incidence, suggesting substantial subclinical or otherwise unreported typhoid. We found no significant differences in seropositivity prevalences by ethnicity, which is in contrast to disease surveillance data in which the indigenous iTaukei Fijian population are disproportionately affected. Using multivariable logistic regression, seropositivity was associated with increased age (odds ratio 1.3 (95% CI 1.2 to 1.4) per 10 years), the presence of a pit latrine (OR 1.6, 95%CI 1.1 to 2.3) as opposed to a septic tank or piped sewer, and residence in settlements rather than residential housing or villages (OR 1.6, 95% CI 1.0 to 2.7). Increasing seropositivity with age is suggestive of low-level endemic transmission in Fiji. Improved sanitation where pit latrines are used and addressing potential transmission routes in settlements may reduce exposure to S. Typhi. Widespread unreported infection suggests there may be a role for typhoid vaccination in Fiji, in addition to public health management of cases and outbreaks.