Assessment of regions affected by Chagas disease
In the last 10 years, due to the successful interruption of the vectorial and transfu- sional transmission of infection by T. cruzi, its incidence has been dramatically reduced in the entire American continent and the raising of awareness of Chagas disease has globalized due to migration to nonendemic countries. Fig. 5.3 shows the approximate distribution of the main active triatomine domiciliated foci that still requires control actions.
According to WHO,65 the estimates based on 2010 data, 5,742,167 people were infected with T. cruzi in 21 Latin American countries, of which 62.4% (3,581,423 people) were from countries of the Southern Cone Initiative. Argentina, Brazil, and Mexico were the three countries with the highest estimated number of infected people (1,505,235, 1,156,821, and 876,458, respectively), followed by Bolivia (607,186). In the Andean Region, which accounts for 958,453 infected people, 45.7% of these (437,960) were from Colombia. Countries with 100,000—200,000 infected people included 2 in the Southern Cone subregion (Chile and Paraguay), 3 in the Andean subregion (Bolivarian Republic of Venezuela, Ecuador, and Peru), and 1 in Central America (Guatemala).
Of new cases due to vectorial transmission, Bolivia had the highest estimated number (8087), followed by Mexico (6135) and Colombia (5274). Between 850 and 2055 new cases were found in 7 countries: Peru (2055), Ecuador (2042), Guatemala (1275), Argentina (1078), El Salvador (972), Honduras (933), and Venezuela (873).
Bolivia accounted for 92.6% of all new cases in the Southern Cone Subregion, and Argentina and Bolivia together accounted for 30.62% of the new cases in Latin America. The Andean subregion, comprising Colombia, Ecuador, Peru, and Venezuela, accounted for 34.23% of the new cases in that Region. Guatemala, El Salvador, and Honduras accounted for 84.62% of the new cases in the seven Central American countries.
In the United States, Chagas disease exists almost exclusively as a zoonosis; only six autochthonous cases have been reported in humans, and the two most recent66 were both attributable to Triatoma sanguisuga. T. sanguisuga has a broad distribution across the south from Texas to Maryland. T. gerstaekeri also shows anthropophilic tendencies and is found in Texas and New Mexico.67
The southern states of the United States have an active sylvatic transmission cycle involving numerous wild animal reservoirs. Recent serological surveys suggest that raccoons and possums are the main hosts68 with prevalences as high as 68%. Different T. cruzi strains have been associated with these two main hosts57: TcI and TcIV with raccoons and TcI with possums. A recent report69 shows 61% of Triatoma rubida collected in Texas infected with TcI. In another study conducted in Arizona,70 41.5% of the 164 triatomine insects were infected with T. cruzi (no DTU was reported). In the United States, based on population figures from countries where Chagas disease is endemic, it is estimated that in 2011 there were about
300,000 people infected with T. cruzi.71
In nonendemic countries, migration flows have been the key for the emergence of Chagas disease in areas where it was not previously reported. The importance of Chagas disease in this new scenario is directly related to the volume of migration flows received by each host country and also related to the specific origin of migrants received, since the distribution of Chagas disease is not homogeneous within endemic countries.72 It is estimated that in Europe there are between 68,000 and 123,000 infected people with T. cruzi, most of them living in Spain.
Figure 5.3 Approximate distribution of the main insect vectors associated with the human habitat that still require control activities in the Americas.
Spain has by far the most Latin American immigrants in Europe, with annual numbers increasing dramatically almost fivefold over the past decade from 446,000 in 2001 to more than 2 million in 2008.73 Another estimate for 2008 is slightly lower, stating that Spain has approximately 1.7 million Latin American immigrants. Of these, an estimated 5.2% were potentially infected with T. cruzi, approximately 17,000 of whom may be expected to eventually present with Chagas disease.74 The same study suggested that there may have been as many as 92 congenital infections of newborns in Spain in 2007. A survey of recent literature72 reveals that numerous
cases have been reported from the immigrant population, mostly by congenital (vertical) transmission and by contaminated blood transfusion.
A case study75 assessed the prevalence of Chagas disease in Bolivian pregnant women in a Spanish hospital for 2 years and found a 17.7% rate (71/401), with a 1.4% vertical transmission rate (1/71). Screening for T. cruzi has been implemented in Spain since 2005.
The survey of literature by Castro et al.76 reveals that Chagas disease has been reported from immigrants in Denmark, Germany, Italy, Netherlands, and Switzerland, and congenital cases have been documented in Romania and France.
Estimates as of 2008 state that Italy has 230,000 Latin American immigrants from Chagas disease endemic countries, while Portugal has 121,001 and Switzerland has 57,000 such immigrants.73 The estimated number of Latin Americans living in France has risen from 27,400 in 1999 to 105,000 in 2005.77 The varying estimates and recent increases in immigration trends to Europe in general highlight the need for European Union-centered assessment of Chagas disease for the region, including comprehensive efforts to halt transfusional and congenital transmission. The number of people infected by T. cruzi ranges from 140 (Austria) to over 12,000 (England).
