Contact tracing and isoniazid preventive therapy for prevention of childhood tuberculosis in The Gambia

Background Tuberculosis is a major public health problem worldwide and is characterized by a high incidence in The Gambia. Children acquire infection primarily from adults in their households, and especially young children are at higher risk of progressing to disease and death. In The Gambia, childhood tuberculosis is poorly addressed in the routine national TB program activities; contact tracing and isoniazid preventive therapy (IPT) are not implemented. The burden of childhood TB is therefore poorly characterized and the operational challenges of implementing IPT are not well understood. Methods TB symptoms screening questionnaire and tuberculin skin testing were administered in the community to child contacts of adults recently diagnosed with TB. Those with TB suggestive symptoms and/or positive TST result were further evaluated in a dedicated clinic with physical examination, chest x ray, sputum induction and examination with smear, Xpert MTB/RIF and culture. Adherence to IPT was measured by pill count and IsoScreen test. Results Co-prevalent TB disease was detected in child contacts both within and outside immediate household of the adult index TB case. Altogether, 1.6% of all child contacts screened had co-prevalent TB disease. 42.2% of the co-prevalent TB cases were among asymptomatic but TST positive child contacts. A combination of Xpert and culture was positive in 32.3% of all children diagnosed with TB, an increase of 9.7 – 22.6% over the yields from microscopy, Xpert and culture alone as individual tests. 255/328 (77.7%) children completed each of six months of IPT with good adherence. Conclusions Contact tracing restricted to symptom screening and immediate households would have missed nearly half of all co-prevalent TB disease in child contacts in this setting. A combination of Xpert and mycobacterial culture had incremental benefit for the bacteriological confirmation of TB disease in actively traced child contacts. Uptake of, and adherence to, IPT were high among the eligible child contacts

Contact tracing and isoniazid preventive therapy for prevention of childhood tuberculosis in The Gambia

Background Tuberculosis is a major public health problem worldwide and is characterized by a high incidence in The Gambia. Children acquire infection primarily from adults in their households, and especially young children are at higher risk of progressing to disease and death. In The Gambia, childhood tuberculosis is poorly addressed in the routine national TB program activities; contact tracing and isoniazid preventive therapy (IPT) are not implemented. The burden of childhood TB is therefore poorly characterized and the operational challenges of implementing IPT are not well understood. Methods TB symptoms screening questionnaire and tuberculin skin testing were administered in the community to child contacts of adults recently diagnosed with TB. Those with TB suggestive symptoms and/or positive TST result were further evaluated in a dedicated clinic with physical examination, chest x ray, sputum induction and examination with smear, Xpert MTB/RIF and culture. Adherence to IPT was measured by pill count and IsoScreen test. Results Co-prevalent TB disease was detected in child contacts both within and outside immediate household of the adult index TB case. Altogether, 1.6% of all child contacts screened had co-prevalent TB disease. 42.2% of the co-prevalent TB cases were among asymptomatic but TST positive child contacts. A combination of Xpert and culture was positive in 32.3% of all children diagnosed with TB, an increase of 9.7 – 22.6% over the yields from microscopy, Xpert and culture alone as individual tests. 255/328 (77.7%) children completed each of six months of IPT with good adherence. Conclusions Contact tracing restricted to symptom screening and immediate households would have missed nearly half of all co-prevalent TB disease in child contacts in this setting. A combination of Xpert and mycobacterial culture had incremental benefit for the bacteriological confirmation of TB disease in actively traced child contacts. Uptake of, and adherence to, IPT were high among the eligible child contacts

Prevalence and risk factors for Staphylococcus aureus nasopharyngeal carriage during a PCV trial.

BACKGROUND: We conducted an ancillary study among individuals who had participated in a cluster-randomized PCV-7 trial in rural Gambia (some clusters were wholly-vaccinated while in others only young children had been vaccinated), to determine the prevalence and risk factors for Staphylococcus aureus nasopharyngeal carriage. METHODS: Two hundred thirty-two children aged 5-10 years were recruited and followed from 4 to 20 months after vaccination started. We collected 1264 nasopharyngeal swabs (NPS). S. aureus was isolated following conventional microbiological methods. Risk factors for carriage were assessed by logistic regression. RESULTS: Prevalence of S. aureus carriage was 25.9%. In the univariable analysis, prevalence of S. aureus carriage was higher among children living in villages wholly-vaccinated with PCV-7 [OR = 1.57 95%CI (1.14 to 2.15)] and children with least 1 year of education [OR = 1.44 95%CI (1.07 to 1.92)]. S. aureus carriage was also higher during the rainy season [OR = 1.59 95%CI (1.20 to 2.11)]. Carriage of S. pneumoniae did not have any effect on S. aureus carriage for any pneumococcal, vaccine-type (VT) or non-vaccine-type (NVT) carriage. Multivariate analysis showed that the higher prevalence of S. aureus observed among children living in villages wholly-vaccinated with PCV-7 occurred only during the rainy season OR 2.72 95%CI (1.61-4.60) and not in the dry season OR 1.28 95%CI (0.78-2.09). CONCLUSIONS: Prevalence of nasopharyngeal carriage of S. aureus among Gambian children increased during the rainy season among those children living in PCV-7 wholly vaccinated communities. However, carriage of S. aureus is not associated with carriage of S. pneumoniae. TRIAL REGISTRATION: ISRCTN51695599 . Registered August 04th 2006

Seasonality of Pneumococcal Nasopharyngeal Carriage in Rural Gambia Determined within the Context of a Cluster Randomized Pneumococcal Vaccine Trial.

BACKGROUND: We conducted an ancillary study among individuals who had participated in a PCV-7 trial in rural Gambia, to determine the influence of season on the prevalence of pneumococcal carriage. METHODS: 636 individuals above 30 months of age were followed from 4 to 20 months after vaccination with PCV-7 or meningococcal-conjugate-vaccine. Nasopharyngeal swabs were collected periodically between November 2006 and June 2008. Overall, 4,495 NPS were collected. RESULTS: Prevalence of pneumococcal nasopharyngeal carriage in the study subjects (median age 11 years) was 55.0%; this prevalence decreased linearly with increasing age (p = 0.001). Prevalence of carriage was significantly higher during the dry than the rainy season for any pneumococcal carriage [57.6% versus 47.8% (p<0.001)], pneumococcal vaccine serotype carriage [10.3% versus 6.5% (p< 0.001)] and non-vaccine serotype carriage [49.7% versus 42.7% (p<0.001)]. Differences remained significant in the adjusted analysis. CONCLUSIONS: In areas of Africa with marked variation in rainfall, seasonality of pneumococcal carriage needs to be considered when interpreting carriage data

Temporal changes in nasopharyngeal carriage of Streptococcus pneumoniaeserotype 1 genotypes in healthy Gambians before and after the 7-valent pneumococcal conjugate vaccine

Streptococcus pneumoniae serotype 1 is one of the leading causes of invasive pneumococcal disease. However, this invasive serotype is hardly found in nasopharyngeal asymptomatic carriage and therefore large epidemiological studies are needed to assess the dynamics of serotype 1 infection. Within the context of a large cluster randomized trial conducted in rural Gambia to assess the impact of PCV-7 vaccination on nasopharyngeal carriage, we present an ancillary analysis describing the prevalence of nasopharyngeal carriage of pneumococcal serotype 1 and temporal changes of its more frequent genotypes. Nasopharyngeal swabs (NPS) were collected before PCV-7 vaccination (December 2003–May 2004) and up to 30 months after PCV-7 vaccination. The post-vaccination time was divided in three periods to ensure an equal distribution of the number of samples: (1) July 2006–March 2007, (2) April 2007–March 2008 and (3) April 2008–Feb 2009. S. pneumoniae serotype 1 were genotyped by MLST. Serotype 1 was recovered from 87 (0.71%) of 12,319 NPS samples collected. In the pre-vaccination period, prevalence of serotype 1 was 0.47% in both study arms. In the post-vaccination periods, prevalence in the fully vaccinated villages ranged between 0.08% in period 1 and 0.165% in period 2, while prevalence in partly vaccinated villages was between 0.17% in period 3 and 1.34% in period 2. Overall, four different genotypes were obtained, with ST3081 the most prevalent (60.71%), followed by ST618 (29.76%). ST3081 was found only in post-vaccination period 2 and 3, while ST618 had disappeared in post-vaccination period 3. Distribution of these major genotypes was similar in both study arms. Emergence of ST3081 and concomitant disappearance of ST618 may suggest a change in the molecular epidemiology of pneumococcal serotype 1 in this region. This change is not likely to be associated with the introduction of PCV-7 which lacks serotype 1, as it was observed simultaneously in both study arms. Future population-based epidemiological studies will provide further evidence of substantive changes in the pneumococcal serotype 1 epidemiology and the likely mechanisms

Seasonality and outbreak of a predominant Streptococcus pneumoniae serotype 1 clone from The Gambia: expansion of ST217 hypervirulent clonal complex in West Africa.

BACKGROUND: Streptococcus pneumoniae serotype 1 causes > 20% of invasive disease, among all age groups combined, in The Gambia. In contrast, it is rarely detected in carriage studies. This study compares the molecular epidemiology of S. pneumoniae serotype 1 causing invasive disease in The Gambia between 1996 and 2005 to those carried in the nasopharynx between 2004 and 2006. RESULTS: A total of 127 invasive and 36 nasopharyngeal carriage serotype 1 isolates were recovered from individuals of all age groups and were analyzed by serotyping, antibiotic susceptibility testing and MLST. MLST analysis revealed 23 different sequence types (STs), 18 of which were novel. The most prevalent clone among the 163 isolates was ST618 (70.5%), followed by ST3575 (7.4%), ST2084 (2.5%) and ST612 (2.5%). A single ST (ST618), previously shown to belong to the ST217 hypervirulent clonal complex, was frequent among carriage (61.1%) and invasive (72.7%) serotype 1 isolates. ST618 causing both paediatric and adult disease peaked annually in the hot dry season and caused outbreak in 1997 and 2002. CONCLUSION: For over a decade, isolates of ST618 have been the dominant lineage among serotype 1 carriage and disease isolates circulating in the Gambia. This lineage shows similar epidemiological features to those of the meningococcus in the African meningitis belt being able to cause outbreaks of disease

Perspectives of TB survivors and policymakers on post-TB disability

Background: An international multistakeholder participatory workshop was hosted in the Gambia, West Africa, in November 2021. Objectives: To explore the experiences, challenges and recommendations of workshop participants on health and wellbeing after TB treatment. Methods: An exploratory, descriptive, qualitative approach was used for data collection through facilitator-guided group discussions. Workshop participants included adolescent and adult TB survivors, and representatives of TB advocacy groups and the policy sector. Discussions were audio-recorded and transcribed verbatim, and the data were analysed using a deductive thematic approach. Results: Overall, 38 participants (22 women) from six West African countries participated in the workshop, comprising 33 TB survivors and advocacy group representatives and 5 participants from the policy sector. Although some TB survivors noted improved ability to carry out physical activities, others continued to experience detrimental effects on their family life, social interactions, physical health and ongoing stigma. Policymakers emphasised the lack of data and clear guidelines on post-TB disability. Conclusions: Some TB survivors continue to suffer detrimental effects of the illness even after treatment completion. However, available data on post-TB disability is inadequate to support policy adoption. Therefore, there is an urgent need for increased advocacy, awareness and research to bridge knowledge gaps

Vitamin D in Gambian children with discordant tuberculosis (TB) infection status despite matched TB exposure: a case control study.

Using a matched case control design conducted at MRC Gambia in 2015, we measured vitamin D levels in pairs of asymptomatic children with discordant tuberculin skin test status despite the same sleeping proximity to the same adult TB index case. Median ages of groups (infected; 10.0 years, uninfected 8.8 years) were not significantly different (p = 0.13). Mean vitamin D levels were 2.05 ng/mL (95% CI - 0.288 to 4.38) higher in 24 highly TB-exposed uninfected children compared with 24 matched highly TB-exposed infected children (p = 0.08). The findings warrant further investigation in larger studies to understand the implications and significance. Conclusion: Vitamin D levels were higher in TB-uninfected children compared with TB-infected despite equal high exposure to a TB case

Effect on nasopharyngeal pneumococcal carriage of replacing PCV7 with PCV13 in the Expanded Programme of Immunization in The Gambia.

INTRODUCTION: In 2011, two years after the introduction of 7-valent Pneumococcal conjugate vaccine (PCV7), the Gambian immunization programme replaced PVC7 with PCV13 (13-valent). Our objective was to assess the additional impact of PCV13 on prevalence of pneumococcal nasopharyngeal carriage. METHODS: We recruited healthy Gambian infants who had received three PCV doses. Nasopharyngeal swabs were collected from infants and their mothers during two cross-sectional surveys (CSS) conducted in infants vaccinated with PCV7 (CSS1) and vaccinated with PCV13 (CSS2). Pneumococci were isolated and serotyped following standardized methods. Whole genome sequencing was performed on non-typable pneumococcus isolated in CSS1 and CSS2. RESULTS: 339 and 350 infants and their mothers were recruited in CSS1 and CSS2, respectively. Overall prevalence of pneumococcal carriage was 85.4% in infants. Among infants, prevalence of vaccine type (VT) carriage was lower in CSS2 [9.4% versus 4.9% (p=0.025) for PCV7-VT; 33.3% versus 18.3% (p<0.001) for PCV13-VT and 23.9% versus 13.7% (p=0.001) for the 6 additional serotypes included in PCV13]. At CSS2, there was a decrease of serotypes 6A (from 15.3% to 5.7%, p<0.001) and 19F (from 5.6% to 1.7%, p=0.007), and an increase of non-typable pneumococci (0.3-6.0%, p<0.001), most of which (82.4%) were from typable serotype backgrounds that had lost the ability to express a capsule. Prevalence of overall and VT carriage in mothers was similar in CSS1 and CSS2. CONCLUSIONS: Replacing PCV7 for PCV13 rapidly decreased prevalence of VT carriage among vaccinated Gambian infants. An indirect effect in mothers was not observed yet. Vaccine-driven selection pressure may have been responsible for the increase of non-typable isolates