Tools for Preventing Enteric Fever
Typhoid and Paratyphoid Fever
Typhoid and paratyphoid fever are caused by the consumption of contaminated water or food and remain endemic in impoverished regions of Asia, Africa, and Oceania. Estimating the burden of these diseases is challenging due to their nonspecific clinical presentation and limited blood-culture surveillance worldwide.
Study by John et al.
A large, prospective two-component study conducted from 2017 through 2020 in India revealed high rates of blood culture-confirmed typhoid fever, particularly in urban areas and larger households with fewer assets and no sanitary toilet. Salmonella enterica serovar Typhi (S. typhi) was the most common pathogen isolated from blood culture, and 98% of isolates were nonsusceptible to quinolones, a pattern consistent with other data from Southeast Asia.
Typhoid Conjugate Vaccines
Recent randomized controlled trials have shown that a single dose of a typhoid conjugate vaccine is safe, immunogenic, and 79 to 85% efficacious at preventing culture-confirmed typhoid fever in children aged 6 months to 15 years. The World Health Organization (WHO) recommends the use of such vaccines in countries with the highest burden of typhoid disease or a high burden of antimicrobial-resistant S. typhi. India qualifies as a priority country based on both criteria. Vaccines against paratyphoid are not yet available, but several are in clinical development, including combination vaccines that cover both S. typhi and S. paratyphi. Such combination vaccines would provide an attractive option to prevent enteric fever in areas where both pathogens are endemic.
Alternative Surveillance Methods
More feasible alternatives to blood culture-based surveillance are urgently needed, as resource-intensive studies are difficult to replicate in many parts of the world. Serosurveillance using new antibody diagnostic tools, environmental sampling with refined molecular techniques, and monitoring nontraumatic ileal perforations can help generate population-level incidence estimates for typhoid fever.
Public Health Threat
Typhoid and paratyphoid fevers continue to pose a substantial public health threat in low-resource settings. The ultimate goal should be building and maintaining water and sanitation infrastructure to eliminate waterborne diseases. In the meantime, the deployment of typhoid conjugate vaccines should be broadened and the development of a paratyphoid vaccine accelerated to reduce the burden of these diseases in endemic regions.