DCE scientific strategy focuses on investigating the interactions between hosts, pathogens and vectors; and evaluating interventions aimed at interrupting transmission and/or reducing the disease burden. Each component can inform the other and provide new opportunities for understanding the dynamics of transmission and identifying new targets for interventions. The multidisciplinary DCE approach comprises a large epidemiological component combined with strong laboratory (mainly diagnosis) support. The core component of epidemiology and laboratory sciences is complemented, whenever possible, by social sciences investigating the human factors influencing the epidemiology of the diseases and the uptake/coverage of interventions.
In addition, the theme has started adding health system and health economic research components to some of its projects with the aim of ensuring the interventions evaluated, when successful, are promptly translated into practice. As the aim of the DCE Theme is to control and eliminate disease, it targets not only the disease itself but also asymptomatic or subclinical infections as these are key components for maintaining transmission at community level.
The DCE theme currently has a large heterogeneous but coherent research portfolio that includes diseases of public health importance in West Africa at different stages of control or elimination. The theme combines both well‐established with more innovative research lines; and internally‐ (malaria, bacterial and viral diseases) with externally‐led research (hepatitis B). The research activities span from large epidemiological studies assessing burden of disease to clinical trials (individual or cluster randomized) testing or assessing the effectiveness of new public health interventions.
Umberto D’Alessandro has substantial work experience in Africa, first as a clinician and later as a clinical epidemiologist. He has been involved in malaria research since 1990, when he carried out the evaluation of the Gambian National programme on insecticide-treated bed nets. He joined the Department of Parasitology at the Prince Leopold Institute of Tropical Medicine, Antwerp, Belgium in 1996, where he set up and led the Epidemiology Unit in the Parasitology Department where he developed a research programme around malaria. In 2011, he joined the MRC Unit The Gambia at LSHTM as Theme Leader and developed a research program around the malaria elimination in The Gambia and West Africa. It includes studies on the dynamics of malaria transmission and factors related to its heterogeneity, and the evaluation of different primaquine doses as gametocytocidal. In January 2014, he became both Professor of Epidemiology at the LSHTM and Director of the MRC Unit The Gambia at LSHTM.
Watch Professor D'Alessandro’s inaugural lecture at LSHTM Week 2019.
Professor Anna Roca
Deputy Theme Leader
Anna Roca is an infectious disease epidemiologist with significant experience leading research groups in Southern and Western Africa. She has an honorary appointment as a Senior Lecturer at the London School of Hygiene and Tropical Medicine and is in the MRC Program Leader Track. She has served in several international pneumonia experts groups; including WHO, BMGF, Global Burden of Disease and Decade of Vaccines. Dr Roca leads an independent line of research focused on the dynamics of bacterial infections and how these dynamics are modified by public health interventions. To understand how bacteria are transmitted to the neonates and design novel interventions to block neonatal transmission are her main research priorities. Her research portfolio includes the evaluation on how new intervention impact on antibiotic resistance.
- Oral azithromycin given during labour decreases bacterial carriage in the mothers and their offspring: a double-blind randomized trial
Bacterial sepsis remains a leading cause of death among neonates with Staphylococcus aureus, Group B Streptococcus (GBS) and Streptococcus pneumoniae identified as the most common causative pathogens in Africa. Asymptomatic bacterial colonization is an intermediate step towards sepsis. We conducted a phase-III, double-blind, placebo-controlled randomized trial to determine the impact of giving one oral dose of azithromycin to Gambian women in labour on the nasopharyngeal carriage of S. aureus, GBS or S. pneumoniae in the newborn at day 6 post-partum. Study participants were recruited in a health facility in Western Gambia. They were followed during 8 weeks and samples were collected during the first 4 weeks. Between April 2013-2014, we recruited 829 women who delivered 843 babies, including 13 stillbirths. Sixteen babies died during the follow-up period. No maternal deaths were observed. No serious adverse events related to the intervention were reported. According to the intention-to-treat analysis, prevalence of nasopharyngeal carriage of the bacteria of interest in the newborns at day 6 was lower in the intervention arm [65.1% versus 28.3% – Prevalence Ratio (PR)=0.43; 95%CI: 0.36-0.52, p<0.001]. At the same time point, prevalence of any bacteria in the mother was also lower in the azithromycin group [nasopharynx (40.0% versus 9.3%, p<0.001); breast milk (21.6% versus 7.9%, p<0.001); and the vaginal tract (24.2% versus 13.2%, p<0.001)]. Differences between arms lasted for at least 4 weeks. Oral azithromycin given to women in labour decreased carriage of bacteria of interest in mothers and newborns and may lower the risk of neonatal sepsis.
- High genetic diversity of Staphylococcus aureus strains colonising the nasopharynx of Gambian villagers before widespread use of pneumococcal conjugate vaccines
With the global efforts of reducing pneumococcal disease through widespread introduction of pneumococcal vaccines, concerns have emerged on the potential increase of morbidity and mortality from S. aureus disease. Little is known however, of the carriage rates of S. aureus or of its’ relationship with carriage of S. pneumoniae in rural Africa, and West Africa in particular where very high rates of carriage of S. pneumoniae have been reported. This study aims to evaluate the prevalence, antibiotic susceptibility patterns and genotypes of S. aureus isolated from the nasopharynx of healthy individuals in rural Gambia before the introduction of routine use of pneumococcal conjugate vaccines in the country. RESULTS: Overall prevalence of S. aureus nasopharyngeal carriage was 25.2 %. All S. aureus isolates tested were susceptible to methicillin. Resistant was observed for sulphamethoxazole-trimethoprim (15 %) and tetracycline (34.3 %). We found 59 different sequence types (ST), 35 of which were novel. The most prevalent sequence types were ST 15 (28 %) and ST 5 (4 %). Eighty two percent (494/600) of study individuals were S. pneumoniae carriers with S. pneumoniae carriage rates decreasing with increasing age groups. S. aureus carriage among pneumococcal carriers was slightly lower than among non-pneumococcal carriers (24.3 versus 29.3 %; p = 0.324). There were no associations of carriage between these two bacteria across the 4 age groups. However, analysis of pooled data children < 2 years and children 2 to < 5 years of age showed a statistically significant inverse association (24.1 and 50.0 % for S. aureus carriage among S. pneumoniae carriers and non-carriers respectively; p = 0.015). CONCLUSIONS: We report that nasopharyngeal carriage of S. aureus in rural Gambia is high in all age groups, with approximately 1 out of 4 individuals being carriers in the pre-pneumococcal vaccination era. There are indications that nasopharyngeal carriage of S.aureus could be inversely related to carriage of S. pneumoniae amongst younger children in The Gambian and that S. aureus clones in The Gambia show significant genetic diversity suggesting worldwide dissemination. Findings from this study provide a useful background for impact studies evaluating the introduction of pneumococcal vaccines or other interventions targeting the control of S. aureus infections and disease.
- Hepatitis E virus infection and acute-on-chronic liver failure in West Africa: a case-control study from The Gambia.
In sub-Saharan Africa, it is unknown whether hepatitis E virus (HEV) infection is a common precipitating event of acute-on-chronic liver failure (ACLF).
To estimate the prevalence of HEV infection in general population and assess whether HEV is a common trigger of ACLF in cirrhotic patients in The Gambia, West Africa.
We first conducted an HEV sero-survey in healthy volunteers. We then tested cirrhotic patients with ACLF (cases) and compensated cirrhosis (controls) for anti-HEV IgG as a marker of exposure to HEV, and anti-HEV IgA and HEV RNA as a marker of recent infection. We also described the characteristics and survival of the ACLF cases and controls.
In the healthy volunteers (n = 204), 13.7% (95% CI: 9.6-19.2) were positive for anti-HEV IgG, and none had positive HEV viraemia. After adjusting for age and sex, the following were associated with positive anti-HEV IgG: being a Christian, a farmer, drinking water from wells, handling pigs and eating pork. In 40 cases (median age: 45 years, 72.5% male) and 71 controls (39 years, 74.6% male), ?70% were infected with hepatitis B virus. Although hepatitis B flare and sepsis were important precipitating events of ACLF, none had marker of acute HEV. ACLF cases had high (70.0%) 28-day mortality.
Hepatitis E virus infection is endemic in The Gambia, where both faecal-oral route (contaminated water) and zoonotic transmission (pigs/pork meat) may be important. However, acute HEV was not a common cause of acute-on-chronic liver failure in The Gambia.