Spatial analysis of tuberculosis in an urban west African setting: is there evidence of clustering?

OBJECTIVES: To describe the pattern of tuberculosis (TB) occurrence in Greater Banjul, The Gambia with Geographical Information Systems (GIS) and Spatial Scan Statistics (SaTScan) and to determine whether there is significant TB case clustering. METHODS: In Greater Banjul, where 80% of all Gambian TB cases arise, all patients with TB registered at chest clinics between March 2007 and February 2008 were asked to participate. Demographic, clinical characteristics and GPS co-ordinates for the residence of each consenting TB case were recorded. A spatial scan statistic was used to identify purely spatial and space-time clusters of tuberculosis among permanent residents. RESULTS: Of 1145 recruited patients with TB, 84% were permanent residents with 88% living in 37 settlements that had complete maps available down to settlement level. Significant high- and low-rate spatial and space-time clusters were identified in two districts. The most likely cluster of high rate from both the purely spatial analysis and the retrospective space-time analysis were from the same geographical area. A significant secondary cluster was also identified in one of the densely populated areas of the study region. CONCLUSIONS: There is evidence of significant clustering of TB cases in Greater Banjul, The Gambia. Systematic use of cluster detection techniques for regular TB surveillance in The Gambia may aid effective deployment of resources. However, passive case detection dictates that community-based active case detection and risk factor surveys would help confirm the presence of true clusters and their causes.

Equine trypanosomosis in the Central River Division of The Gambia: a study of veterinary gate-clinic consultation records.

The objective of this study was to provide epidemiological information of equine trypanosomosis in the Central River Division (CRD) of The Gambia. Therefore, 2285 consultations records of equines, admitted in a gate-clinic at Sololo in CRD, were studied retrospectively. The data were recorded in the period between September 1995 and July 2002 and comprised consultations of 2113 horses and 172 donkeys. 'Trypanosome infection' was the most frequently diagnosed condition and accounted for 61% of the cases. Horses were more frequently diagnosed with trypanosome infections than donkeys (p<0.001), with an occurrence of 63% compared to 43% in donkeys. In both horses and donkeys, trypanosome infections were mainly due to Trypanosoma congolense (64%) and T. vivax (32%). There was no difference observed in the occurrence of trypanosome infections in male or female donkeys (p=0.585), but there were more female (67.8%) horses observed with trypanosome infections than male horses (60.7%; p=0.003). There was no difference observed in the occurrence of trypanosome infections in donkeys older or younger than 1 year (p=0.130), but more older horses (63.2% >1 year) were observed with trypanosome infections than young horses (54.5% <1 year; p=0.033). The number of donkeys and horses with trypanosome infections decreased during the rainy season (June-September). The majority of equines that were admitted with trypanosome infections were severely anaemic. The average packed cell volume (PCV) declined with increasing parasitaemia (p=0.006). Seventy-four percent of the farmers' predictions of trypanosome infections in their equines were confirmed by darkground-microscopy. That proved that farmers had a fairly accurate knowledge of the diseases affecting their equines. The treatments executed at the gate-clinic were generally effective. The few (0.4%) relapses of the T. vivax infections that were previously treated with diminazene aceturate in this study were not sufficient to prove drug resistance. The study showed that the analysis of consultation records at a gate-clinic can provide complementary information to conventional epidemiological studies in the same research area.

Isoniazid preventive treatment among child contacts of adults with smear-positive tuberculosis in The Gambia.

Setting: Greater Banjul area of The Gambia. Objectives: To evaluate uptake, adherence and completion of treatment among tuberculosis (TB) exposed children in The Gambia when isoniazid preventive treatment (IPT) is delivered at home Design: Child (age <5 years) contacts of adults with smear-positive TB were prospectively enrolled. Following symptom screening, tuberculin skin testing and clinical evaluation where indicated, those without disease were placed on daily isoniazid, provided monthly at home. Adherence was assessed by pill counts and IsoScreen™ urine test. Results: Of 404 contacts aged <5 years, 368 (91.1%) were offered IPT. Of the 328 (89.4%) for whom consent was received and who commenced IPT, 18 (5.5%) dropped out and 310 (94.5%) remained on IPT to the end of the 6-month regimen. Altogether, 255/328 children (77.7%, 95%CI 73.2-82.2) completed all 6 months, with good adherence. The IsoScreen test was positive in 85.3% (435/510) of all tests among those defined as having good adherence by pill count and in 16% (8/50) of those defined as having poor adherence (P < 0.001). A cascade of care analysis showed an overall completion rate with good adherence of 61% for all child contacts. Conclusion: Home-delivered IPT among child contacts of adults with smear-positive TB in The Gambia achieved verifiable high uptake and adherence rates. System rather than patient factors are likely to determine the success of IPT at national level.

Contexte : Région du Grand Banjul en Gambie.Objectifs : Evaluer la couverture, l'adhésion et l'achèvement du traitement parmi des enfants exposés à la tuberculose (TB) en Gambie quand le traitement préventif par isoniazide (TPI) est donné à domicile.Schéma : Les enfants âgés de <5 ans, contacts d'adultes atteints de TB à frottis positif, ont été enrôlés de manière prospective. Après dépistage sur les symptômes, test cutané à la tuberculine et évaluation clinique quand cela était indiqué, les enfants non malades ont été mis sous isoniazide, fourni une fois par mois à domicile. L'adhésion a été évaluée par un comptage des comprimés et par un test urinaire IsoScreen™.Résultats : Sur 404 contacts âgés de <5 ans, 368 (91,1%) ont été invités à bénéficier du TPI, et 328 (89,4%) ont consenti et commencé le TPI. Sur ces 328 enfants, 18 (5,5%) ont abandonné et 310 (94,5%) sont restés sous TPI jusqu'à la fin du 6e mois. Au total, 255/328 enfants (77,7% ; IC95% 73,2­82,2) ont achevé les 6 mois de traitement avec une bonne adhésion. Le test IsoScreen a été positif chez 85,3% (435/510) de tous les tests parmi ceux définis comme ayant une bonne adhésion par le comptage des comprimés et chez 16% (8/50) de ceux définis comme ayant une adhésion médiocre (P < 0,001). L'analyse de la « cascade des soins ¼ a montré, pour tous les enfants contacts, un taux de bonne adhésion d'ensemble de 61%.Conclusion: L'administration à domicile du TPI à des enfants contacts d'adultes atteints de TB à frottis positif en Gambie a abouti à une bonne couverture et à un bon taux d'adhésion, tous deux vérifiables. Ce sont les facteurs de système plutôt que ceux liés au patient qui sont susceptibles de déterminer le succès du TPI au niveau national.

Marco de referencia: La zona del Gran Banjul en Gambia.Objetivos: Evaluar la aceptación del tratamiento preventivo con isoniazida (TPI), su cumplimiento y su compleción por parte de los niños expuestos en Gambia, cuando se suministra el tratamiento en los hogares.Método: Se incluyeron en el estudio de manera prospectiva los niños menores de 5 años de edad que eran contactos de un adulto con diagnóstico de tuberculosis (TB) y baciloscopia positiva. Luego de la detección sistemática a partir de los síntomas, se practicaron la prueba cutánea de la tuberculina y la evaluación clínica cuando estaban indicadas; en caso de ausencia de enfermedad activa se inició el tratamiento diario con isoniazida, la cual se suministraba en el hogar cada mes. Se evaluó el cumplimiento en función del recuento de los comprimidos y la prueba IsoScreen™ en muestras de orina.Resultados: En los 404 contactos menores de 5 años de edad, se ofreció el TPI a 368 niños (91,1%) y 328 lo aceptaron y comenzaron a recibirlo (89,4%). De este grupo, 18 niños abandonaron el tratamiento (5,5%) y 310 recibían aun el medicamento al final del 6 mes (94,5%). De los 328 niños, 255 terminaron los 6 meses de tratamiento, con un cumplimiento satisfactorio (77,7%; IC del 95% de 73,2 hasta 82,2). La prueba IsoScreen fue positiva en el 85,3% (435/510) de los casos definidos con cumplimiento adecuado según el recuento de comprimidos y en el 16% (8/50) de los casos cuyo cumplimiento se consideró deficiente (P < 0,001). El análisis de la trayectoria asistencial reveló que en todos los contactos la tasa global de compleción con cumplimiento satisfactorio fue 61%.Conclusión: El TPI suministrado en el hogar a los niños que son contactos de un adulto con diagnóstico de TB y baciloscopia positiva alcanza altas tasas de aceptación y de cumplimiento que se pueden verificar. Los factores que determinan el éxito del TPI a escala nacional dependen del sistema de salud y no del paciente.

Risk factors for defaulting from tuberculosis treatment: a prospective cohort study of 301 cases in the Gambia.

SETTING: An urban tuberculosis (TB) clinic, The Gambia. OBJECTIVE: To identify patient characteristics associated with increased rates of defaulting from treatment, specifically knowledge and cost factors amenable to intervention. DESIGN: Prospective cohort study of TB cases at least 15 years of age commencing treatment, interviewed by semi-structured questionnaire and followed for attendance at thrice-weekly directly observed treatment (DOT). RESULTS: Of 301 patients, 76 (25.2%) defaulted from treatment and 25 did not return for treatment. The defaulting rate was higher among those who said they were uncertain that their treatment would work (HR 3.64; 95%CI 1.42-9.31, P = 0.007) and among those who incurred significant time or money costs travelling to receive treatment (HR 2.67; 95%CI 1.05-6.81; P = 0.04). These factors had differing effects with respect to time: uncertainty over treatment success was important in the first 90 days of treatment, while increased cost of travelling to the clinic was important after 90 days. CONCLUSION: In The Gambia, risk groups for defaulting can be recognised at the start of treatment and are at highest risk at different times. Home-based self-administration of medications after 3 months of DOT should be considered as confidence in treatment success rises, and the costs of travelling to receive treatment start to take their toll.