Diphtheria epidemiology in the UK and Europe

Wagner, Karen Susan (2015) Diphtheria epidemiology in the UK and Europe. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

A resurgence of diphtheria (Corynebacterium diphtheriae) occurred in the former Soviet Union in the 1990s. Concerted control measures brought about a decline in cases, however some endemic transmission has continued and increasingly C. ulcerans cases have been reported in some Western European countries. Questions existed regarding risk factors for infection, availability of diphtheria antitoxin (DAT) treatment, circulation of potentially toxigenic Corynebacteria, and UK population immunity. Surveillance data from the World Health Organization European Region, Diphtheria Surveillance Network (DIPNET) and UK were analysed. In addition, 47 countries provided information regarding their DAT treatment supplies. To examine circulation of Corynebacteria, throat swabs were screened across ten countries. UK diphtheria immunity was assessed by serosurvey, and vaccination coverage data from nine London Primary Care Trusts (PCTs) were analysed by ethnicity. During 2000-2009 C. diphtheriae cases declined across the European Region. C. ulcerans cases (associated with domestic animals) outnumbered C. diphtheriae (associated with travel to endemic areas) in DIPNET countries outside the former Soviet Union. There was a clear protective effect of vaccination. The case fatality rate for respiratory diphtheria was lower in Latvia than in other DIPNET countries. Global shortages of DAT were highlighted. Screening identified endemic transmission of toxigenic C. diphtheriae in Latvia and Lithuania, and circulation of non-toxigenic strains in several countries. UK population immunity had increased since the last serosurvey in 1996; in 2009 75% of the population had at least basic protection. Low childhood vaccination coverage in London related partly to the size of ethnic groups within a PCT but also to completeness of data records. Surveillance and screening datasets likely missed some cases/isolates due to lost clinical and/or laboratory expertise. These skills need to be retained and high vaccination coverage levels achieved, as well as records accurately maintained. A DAT alternative is needed, with improved availability and access.