Background:
Pneumococcal disease is a significant cause of morbidity and mortality in young children in Nepal, and
currently available pneumococcal conjugate vaccines offer moderate coverage of invasive disease isolates.
Methods:
A prevalence study of children aged 1.5 to 24 months in urban and rural Nepal was conducted. In the urban
group, nasopharyngeal swabs (NPS) were transported using silica desiccant packages (SDP) with delayed processing (2
weeks), or skim-milk-tryptone-glucose-glycerin (STGG) with immediate processing (within 8 hours). Pneumococcal
nasopharyngeal carriage prevalence, serogroup/type distribution and isolate genotypes (as defined by multilocus sequence
typing) were determined.
Results:
1101 children were enrolled into the study: 574 in the urban group and 527 in the rural group. Overall carriage
prevalence based on culture from specimens transported and stored in STGG was 58.7% (337/574), compared to 40.9%
(235/574) in SDP. There was concordance of detection of pneumococcus in 67% of samples. Using the SDP method,
pneumococcal carriage prevalence was higher in the rural population (69.2%; 364/526) compared to the urban population
(40.9%; 235/574). Serogroup/type distribution varied with geographical location. Over half of the genotypes identified in
both the urban and rural pneumococcal populations were novel.
Conclusion:
The combination of delayed culture and transport using SDP underestimates the prevalence of pneumococcal
carriage; however, in remote areas, this method could still provide a useful estimate of carriage prevalence and serogroup/
type distribution. Vaccine impact is unpredictable in a setting with novel genotypes and limited serotype coverage as
described here. Consequently, continued surveillance of pneumococcal isolates from carriage and disease in Nepali children
following the planned introduction of pneumococcal conjugate vaccines introduction will be essential.