Tuberculosis Transmission to Young Children in a South African Community: Modeling Household and Community Infection Risks

Abstract

Introduction Tuberculosis (TB) transmission is determined by contact between infectious and susceptible individuals. A recent study reported a 4% annual risk of child TB infection (ARTI) in a Southern African township. A model was used to explore the interactions between prevalence of adult TB infection, adult-to-child contacts and household ventilation which could result in such a high ARTI. Methods Number of residents per household and TB incidence were derived from a household census and community TB registers. Using the “Wells-Riley” equation and probability analyses of contact between TB infectious adults and pre-school children, we estimated the ARTI within and outside of the home. Results There was a mean of 2.2 adults per child-household with a 1.35% annual adult smear-positive TB notification rate. The maximal household ARTI was 3% which was primarily determined by the number of resident adults. Transmission risk outside the home increased with numbers of households visited. Transmission probabilities were sensitive to exposure time, ventilation and period of adult infectivity. The benefits of increased ventilation were greatest when the period of infectivity was reduced. Similar reductions in household transmission could be achieved by increasing ventilation from 2 to 6 air changes/hour or separating child and adult sleeping areas. Conclusions The ARTI of pre-school children predominantly results from infectious residents in the home. However, even with limited social interactions, a substantial proportion of transmission may occur from non-resident adults. The benefits of increased ventilation are maximized when the period of infectivity is reduced by prompt treatment of source cases.

Pathological Changes of Mycobacterium Tuberculosis and Treatments with Alcoholic Extract of Arachis hypogaea and Ethambutol in Mice

“…Argenine also may play a role in elaborate high percentage of nitrous oxide which consider as effective supporting factor to the activated macrophage (Schon et al, 2003;Wood et al, 2010). The present study shown that intra peritoneal infection does result in chronic TB infection in mice organs similar to that observed during low dose aerosol infection mentioned by (Cardona et al, 1999).…”

“…Peanuts are known to be rich in L-arginine and supplementation of nutrition rich in arginin may shorten duration of treatment as well as increase recovery in tuberculosis patients (Schon et al, 2003), Arginine increase nitrogen dioxide level which has a role in stimulating the body defences, patient show shorter duration of cough, increased weight gain and higher seputum conversion rate, all tuberculosis patients had lower levels of plasma L-arginine than healthy one (Wood et al, 2010). Therefor, the aim of this study is to demonstrate the effect of Arachis hypogaea and ethambutol on mice infected with mycobecterim tuberculosis.…”

Yield of contact tracing from pediatric tuberculosis index cases in Gaborone, Botswana

“…1,9 The current study challenges this notion, suggesting that contact tracing of pediatric cases is as good as the traditional approach. We postulate that because newly diagnosed pediatric TB generally reflects TB transmission within the past year, 10 often from a household contact, 2,11 a pediatric TB case will frequently signify the presence of an undiagnosed infectious case in the household. Furthermore, pediatric cases may have been infected in the community and represent source cases at home, responsible for child-to-adult and child-to-child transmission.…”

Advances in childhood tuberculosis – contributions from the University of Cape Town

“…Reductions in household transmission could be achieved by increasing ventilation or by separating child and adult sleeping areas. 6 Some important insights into the epidemiology of paediatric TB in high prevalence settings have also been gained through trials of novel TB vaccines. 7 Mahomed et al 8 reviewed the clinical records of all children under 2 years of age diagnosed with TB disease in the greater Cape Town area who were born during a change in the vaccination programme from percutaneous (PC) Tokyo to intradermal (ID) Danish BCG.…”