ABSTRACT
BACKGROUND: A serogroup A meningococcal polysaccharide-tetanus toxoid conjugate vaccine (PsA-TT, MenAfriVac) was licensed in India in 2009, and pre-qualified by WHO in 2010, on the basis of its safety and immunogenicity. This vaccine is now being deployed across the African meningitis belt. We studied the effect of PsA-TT on meningococcal meningitis and carriage in Chad during a serogroup A meningococcal meningitis epidemic. METHODS: We obtained data for the incidence of meningitis before and after vaccination from national records between January, 2009, and June, 2012. In 2012, surveillance was enhanced in regions where vaccination with PsA-TT had been undertaken in 2011, and in one district where a reactive vaccination campaign in response to an outbreak of meningitis was undertaken. Meningococcal carriage was studied in an age-stratified sample of residents aged 1-29 years of a rural area roughly 13-15 and 2-4 months before and 4-6 months after vaccination. Meningococci obtained from cerebrospinal fluid or oropharyngeal swabs were characterised by conventional microbiological and molecular methods. FINDINGS: Roughly 1·8 million individuals aged 1-29 years received one dose of PsA-TT during a vaccination campaign in three regions of Chad in and around the capital N'Djamena during 10 days in December, 2011. The incidence of meningitis during the 2012 meningitis season in these three regions was 2·48 per 100,000 (57 cases in the 2·3 million population), whereas in regions without mass vaccination, incidence was 43·8 per 100,000 (3809 cases per 8·7 million population), a 94% difference in crude incidence (p<0·0001), and an incidence rate ratio of 0·096 (95% CI 0·046-0·198). Despite enhanced surveillance, no case of serogroup A meningococcal meningitis was reported in the three vaccinated regions. 32 serogroup A carriers were identified in 4278 age-stratified individuals (0·75%) living in a rural area near the capital 2-4 months before vaccination, whereas only one serogroup A meningococcus was isolated in 5001 people living in the same community 4-6 months after vaccination (adjusted odds ratio 0·019, 95% CI 0·002-0·138; p<0·0001). INTERPRETATION: PSA-TT was highly effective at prevention of serogroup A invasive meningococcal disease and carriage in Chad. How long this protection will persist needs to be established. FUNDING: The Bill & Melinda Gates Foundation, the Wellcome Trust, and Médecins Sans Frontères.
Subject(s)
Meningitis, Meningococcal/prevention & control , Meningococcal Vaccines , Neisseria meningitidis, Serogroup A/isolation & purification , Adolescent , Adult , Age Distribution , Carrier State/diagnosis , Carrier State/epidemiology , Carrier State/prevention & control , Chad/epidemiology , Child , Child, Preschool , Epidemics , Humans , Incidence , Infant , Meningitis, Meningococcal/diagnosis , Meningitis, Meningococcal/epidemiology , Population Surveillance/methods , Vaccination , Young AdultABSTRACT
AIMS: Greenhouse misting systems used for watering plants produce fine aerosols. They are a possible cause for bacterial infections. This study investigates the colonization of greenhouse misting systems with Legionella spp. and Pseudomonas spp. and evaluates a possible health hazard. METHODS AND RESULTS: Between June and September 2003, a total of 80 water samples were collected in 20 different greenhouse systems in Germany, each tested on two different occasions. Each time, water was drawn at a central tap and at the outlet of spray nozzles. Sampled greenhouses were used to cultivate various plants and trees for commercial, recreational or scientific reasons, some of them in tropical conditions. Legionella spp. were detected in 10% of the systems (two systems), but only in low numbers. On the contrary, Pseudomonas spp. were recovered from 70% of the greenhouse watering systems (14 systems), occasionally at counts greater than 10,000 CFU per 100 ml. A random amplified polymorphic DNA polymerase chain reaction typing method was used to demonstrate that each colonized greenhouse had one or several individual strains of Legionella and Pseudomonas that could not be detected in any other system. CONCLUSIONS: This study demonstrates that aerosolizing greenhouse watering systems may be contaminated with Legionella or Pseudomonas which under certain circumstances could become a potential source of infection for workers and visitors. SIGNIFICANCE AND IMPACT OF THE STUDY: The study results indicate that greenhouse misting systems should be included in Legionella and Pseudomonas monitoring and control programs.
