Despite previous evidence being inconclusive, an Article published Online First and in an upcoming edition of the Lancet shows that the organisms causing bacterial infections in African children with sickle-cell anaemia are the same as those in developed countries. Vaccination against these bacterial infections, with vaccines that are readily available in developed nations, could substantially improve survival in these children. The Article is written by Dr Thomas N Williams, KEMRI/Wellcome Trust Programme, Kilifi, Kenya, and colleagues across Africa and the UK.
In sub-Saharan Africa, more than 90% of children with sickle-cell anaemia die before the diagnosis can be made. The introduction of penicillin prophylaxis and immunisation with conjugate vaccines directed against S. pneumonia and H. influenzae type b have led to substantial improvements in the prognosis of patients born with sickle-cell anaemia in developed countries. The causes of death are poorly documented, but bacterial sepsis is probably important. Available evidence has suggested that the range of organisms causing invasive bacterial disease in African patients with sickle-cell anaemia might differ from those in developed countries. The authors examined the risk of invasive bacterial diseases in children with sickle-cell anaemia. They prepared blood cultures from all children younger than 14 years who were admitted from within a defined study area to Kilifi District Hospital between Aug 1, 1998, and March 31, 2008; those with bacteraemia were defined as cases.
The researchers found 2157 episodes of bacteraemia in 38 441 admissions (6%). 1749 of these children with bacteraemia (81%) were typed for sickle-cell anaemia, of whom 108 (6%) were positive as were 89 of 13 492 controls (1%). The organisms most commonly isolated from children with sickle-cell anaemia were Streptococcus pneumoniae (44/108 isolates; 41%), non-typhi Salmonella species (19/108; 18%), Haemophilus influenzae type b (13/108; 12%), Acinetobacter species (seven of 108; 7%), and Escherichia coli (seven of 108; 7%). Children with sickle-cell anaemia were 26 times more likely to have an invasive bacterial infection than those without; the strongest associations for specific bacteria were for S. pneumonia (33 times more likely for children with sickle-cell anaemia) certain types of Salmonella species (36 times more likely), and H. influenzae type b (28 times more likely).
The authors say: "Overall, more than 10% of episodes of pneumococcal bacteraemia in our study occurred in children with sickle-cell anaemia, three quarters of which were of serotypes that are represented in the licensed ten-valent pneumococcal conjugate vaccine. Although the introduction of pneumococcal conjugate vaccine into routine immunisation schedules in Africa will be of benefit to all, it is likely to be particularly beneficial for children with sickle-cell anaemia."
They conclude: "The organisms causing bacteraemia in African children with sickle-cell anaemia are the same as those in developed countries. Introduction of conjugate vaccines against S. pneumoniae and H. influenzae into the childhood immunisation schedules of African countries could substantially affect survival of children with sickle-cell anaemia."
In an accompanying Comment, Dr Jane Hankins and Dr Russell E Ware, St Jude Children's Research Hospital, Memphis, TN, USA, say: "Whether in the Americas, Europe, or Africa, sickle-cell disease remains an affliction affecting millions of persons, but the lessons are clear. The key to reducing morbidity and mortality involves early identification through screening, early antibiotic prophylaxis, education about disease complications, and appropriate immunisations against bacterial pathogens, especially S pneumoniae. When these ounces of prevention are put into place, we make important strides toward a pound of improvement and eventual cure."
Dr Thomas N Williams, KEMRI/Wellcome Trust Programme, Kilifi, Kenya. T) +254 733 411021 E) twilliams@kilifi.kemri-wellcome.org
For Dr Russell E Ware, St Jude Children's Research Hospital, Memphis, TN, USA, please contact St Jude's Press Office. T) +1 901 595-3061 / +1 901 595-2295 E) Russell.Ware@STJUDE.ORG / summer.freeman@stjude.org / carrie.strehlau@stjude.org
For full Article and Comment, see: http://press.thelancet.com/sicklecellfinal.pdf
Journal
The Lancet