Addressing the neglect: Chagas disease in London, UK
Authors: Ana Requena-Méndez, David A J Moore, Carme Subirà, Jose Muñoz
Journal: The Lancet Global Health (2016)

Chagas disease is an emerging but still largely unrecognised infectious parasitic disease in European countries.1Basile L Jansa JM Carlier Y et al.Chagas disease in European countries: the challenge of a surveillance system.Euro Surveill. 2011; 16 (pii=19968)Google Scholar It has important public health implications because, although the classic vector-borne route of transmission only occurs in endemic areas of Latin America, the less common transmission routes—blood transfusion, transplantation, and vertical transmission from mother to child—have been shown in Europe.2Requena-Méndez A Albajar-Viñas P Angheben A Chiodini P Gascón J Muñoz J Health policies to control Chagas disease transmission in European countries.PLoS Negl Trop Dis. 2014; 8: e3245Crossref Scopus (63) Google Scholar Therefore, providing policy makers with accurate estimates of country-specific prevalence of Chagas disease should inform the design and implementation of the most cost-effective health interventions.3Requena-Méndez A Aldasoro E de Lazzari E et al.Prevalence of Chagas disease in Latin-American migrants living in Europe: a systematic review and meta-analysis.PLoS Negl Trop Dis. 2015; 9: e0003540Crossref Scopus (215) Google Scholar We used demographic data from London, UK, and Trypanosoma cruzi seroprevalence data from source countries to generate high-resolution estimates of the burden of undetected T cruzi infection in London, and compared these estimates with the actual number of cases reported. The number of residents in London who were originally from the 21 endemic countries in Central and South America was calculated from the 2011 UK National Census4Office for National Statistics2011 Census for England and Wales.http://www.ons.gov.uk/ons/guide-method/census/2011/index.html?utm_source=twitterfeed&utm_medium=twitterDate: 2011Google Scholar and was stratified by borough. We did not include undocumented migrants and individuals born to mothers from endemic Latin American countries. To calculate the expected number of people infected with T cruzi, the number of migrants from each country of origin was multiplied by that country's specific Chagas disease prevalence among migrants living in Europe, as estimated in a meta-analysis.3Requena-Méndez A Aldasoro E de Lazzari E et al.Prevalence of Chagas disease in Latin-American migrants living in Europe: a systematic review and meta-analysis.PLoS Negl Trop Dis. 2015; 9: e0003540Crossref Scopus (215) Google Scholar For endemic Latin American countries without data in the meta-analysis, the prevalence was obtained from a report based on 2010 estimates of Chagas disease in Latin America.5WHOChagas disease in Latin America: an epidemiological update based on 2010 estimates.Wkly Epidemiol Rec. 2015; 90: 33-43Google Scholar The minimum and maximum prevalence estimates for countries in the meta-analysis were derived from the 95% CIs. Finally, the total expected number of cases was divided by the total Latin American population living in each London borough. The actual number of diagnosed cases of Chagas disease in London registered from Jan 1, 2001, to Sept 30, 2014, was derived from the number of positive serological tests reported by the UK National Parasitology Reference Laboratory, where all UK serological testing for this disease is done. To estimate the index of underdiagnosis, we calculated the rate ratio between observed and expected prevalence (ie, the proportion of diagnosed cases divided by the total estimated cases). The index was calculated as 1–rate ratio. We estimated that 95 579 individuals originally from the 21 T cruzi endemic countries of Central and South America were living in London in 2011.4Office for National Statistics2011 Census for England and Wales.http://www.ons.gov.uk/ons/guide-method/census/2011/index.html?utm_source=twitterfeed&utm_medium=twitterDate: 2011Google Scholar Lambeth, Southwark, Wandsworth, and Brent were the boroughs with the largest Latin American migrant populations (figure). 1211 migrants were estimated to have Chagas disease in 2011, giving a London-wide prevalence of 1·27%. The numbers of expected cases of Chagas disease were highest in Lambeth (n=133) and Southwark (n=198). Four other boroughs were predicted to have between 50 and 100 cases of Chagas disease (figure). Although Brazil, Colombia, Guyana, and Ecuador contributed the largest migrant populations, higher prevalence in Bolivia meant that the predicted estimate of Chagas disease was highest in these migrants (table). In descending order of prevelance, Brazilian, Argentinian, Colombian, and Mexican migrants also contributed notably to the total predicted burden in London.TableExpected prevalence of Chagas disease in London in 2011, by country of originNumber of migrantsExpected cases (range*Minimum and maximum values could be derived from 95% CIs in the meta-analysis but not the 2010 report.)Estimated prevalence†Based on a meta-analysis3 and a report of Chagas disease prevalence in Latin America in 2010.5Argentina4567100 (37–189)2·2%Belize21210·3%Bolivia2694485 (374–610)18·0%Brazil31 357188 (50–351)0·6%Chile291329 (5–69)1·0%Colombia19 33897 (29–178)0·5%Costa Rica25400·2%Ecuador717129 (13–52)0·4%El Salvador36436 (6–43)3·7%French Guiana12110·8%Guatemala30541·2%Guyana13 7981160·8%Honduras1647 (2–12)4·2%Mexico378557 (9–142)1·5%Nicaragua1547 (1–17)4·6%Panama22910·5%Paraguay28716 (10–23)5·5%Peru330120 (8–39)0·6%Suriname20320·8%Uruguay5404 (0–12)0·8%Venezuela382234 (6–85)0·9%Total95 57912111·3%* Minimum and maximum values could be derived from 95% CIs in the meta-analysis but not the 2010 report.† Based on a meta-analysis3Requena-Méndez A Aldasoro E de Lazzari E et al.Prevalence of Chagas disease in Latin-American migrants living in Europe: a systematic review and meta-analysis.PLoS Negl Trop Dis. 2015; 9: e0003540Crossref Scopus (215) Google Scholar and a report of Chagas disease prevalence in Latin America in 2010.5WHOChagas disease in Latin America: an epidemiological update based on 2010 estimates.Wkly Epidemiol Rec. 2015; 90: 33-43Google Scholar Open table in a new tab The total number of reported cases of T cruzi infection diagnosed in London from 2001 to 2014 was 41 (Allen J, Hospital for Tropical Diseases, personal communication), giving a prevalence among Latin American migrants in London of 0·043%. The rate ratio between the observed and the expected prevalence of T cruzi infection was 3·34%, resulting in an index of underdiagnosis of 96·6%. On the basis of epidemiological and demographic predictions, the estimated Chagas disease prevalence among Latin American migrants exceeds 1%. However, with only 41 reported cases, this finding would mean that more than 1000 people in London are unknowingly infected with T cruzi. The level of underdiagnosis is very high,6Allen J Chagas disease at the Hospital for Tropical Diseases, London. In: Conference proceedings. American Society of Tropical Medicine and Hygiene, New Orleans, LA2014Google Scholar although the proportion is similar to those other non-endemic countries.1Basile L Jansa JM Carlier Y et al.Chagas disease in European countries: the challenge of a surveillance system.Euro Surveill. 2011; 16 (pii=19968)Google Scholar, 7Bern C Montgomery SP An estimate of the burden of Chagas disease in the United States.Clin Infect Dis. 2009; 49: e52-e54Crossref PubMed Scopus (442) Google Scholar Despite the increase in the number of people arriving in London from endemic countries each year, studies of Chagas disease and the health status of Latin America migrants are scarce.8Roura M Domingo A Leyva-Moral JM Pool R Hispano-Americans in Europe: what do we know about their health status and determinants? A scoping review.BMC Public Health. 2015; 15: 472Crossref Scopus (10) Google Scholar Thus, health-care providers' knowledge of this disease might not be proportionate to the increasing chance that they could unknowingly encounter infected patients. Estimation of the real size of the Latin America migrant population is constrained by the use of official data. Accordingly, our analysis did not include irregular migrants or second-generation Latin American migrants in London. If these groups are included, we estimate (albeit crudely) that 133 500 Latin American migrants would have been in London in 2011.9McIlwaine C Camilo-Cock J Linneker B Queen MaryUniversity of LondonNo longer invisible: the Latin America community in London. Queen Mary, University of London, London2011Google Scholar Inclusion of second-generation Latin American migrants might be useful because they could have been exposed to T cruzi through vertical transmission without ever having travelled to Latin America. Another group to consider is Latin America migrants who have been granted citizenship in other European countries and, therefore, might no longer be identifiable as being of Latin America origin.9McIlwaine C Camilo-Cock J Linneker B Queen MaryUniversity of LondonNo longer invisible: the Latin America community in London. Queen Mary, University of London, London2011Google Scholar Antenatal screening for and treatment of vertically infected neonates are not being done in the UK, although these strategies are recommended by WHO because of high treatment efficacy.10WHOControl of Chagas disease. Second report of the WHO Expert Committee. World Health Organization, Geneva2002Google Scholar Implementation of Chagas disease screening strategies in antenatal care programmes in London, where half of all Latin American migrants in the UK reside, should be urgently considered by policy makers. Integration into existing antenatal screening programmes for other infectious diseases (eg, HIV and syphilis) or haemoglobinopathies (for which data on country of origin are already collected) could facilitate uptake by antenatal units. To be cost-effective, screening should be limited to people from countries likely to yield the most cases. We found that Bolivian migrants had the highest burden of infection despite the number of residents in London not being high. Argentina, Brazil, and Colombia were also associated with high predicted numbers of Chagas disease cases in London. Moreover, efforts to promote screening should target those for whom screening could be most beneficial, such as pregnant Latin American women or those of childbearing age. Finally, prioritising screening in boroughs of London with the largest burdens of underdiagnosis should deliver the greatest yields on time and resources invested. We declare no competing interests. The ISGlobal Research group receives funds from AGAUR, (project-2009SGR385) and RICET (RD12/0018/0010) within the Spanish National plan of R+D+I, which is cofunded by ISCIII-(FEDER).