Home Economics American Trypanosomiasis Chagas Disease, Second Edition: One Hundred Years of Research
Initiative of the Central American countries: epidemiological trends
In these countries there are 2 million infected individuals and 26 million are at risk of contracting the infection. This represents 11% of the prevalence of infected individuals of the whole continent.
As the vectors of Chagas disease in these countries are not strictly domiciliated, it is necessary to adapt and test the vector control strategies to the local entomological conditions.
In the Central American countries, Belize, Costa Rica, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, and Panama, progress in blood banks control is also proceeding well and all of them except one have issued legislation for compulsory blood screening against blood infected by T. cruzi.
Similarly, the elimination of the vectorial transmission was launched at an Intergovernmental meeting held in Tegucigalpa in October 1997 where detailed country by country plans of action including annual goals, budgetary needs, evaluation mechanisms, and research needs were prepared.55
The advances made in vector control and in control of blood transfusions in these countries include58:
Progress in control in each country is reported as follows:
The only vector species of epidemiological importance is T. dimidiata, but it is restricted to the wild environment. There are sporadic reports of insect adults attracted by light that are frequently found in the periphery of the cities and villages. The seroprevalence in the general population is very low and the seropositives found are migrants from neighboring countries. The screening of blood banks has 100% coverage and the prevalence among blood donors in 2000 was 0.5%.
The main vector is T. dimidiata. The vectors are found in the central plain, extending primarily to the northwest and southwest regions of the country. Seroprevalence of 1.94% was found in some blood banks of the country that participated in one study in 2000. A survey carried out in the Heredia Province in 2001 in school children aged 7—12 years showed an infection rate of 0.2%. Chagas disease is not considered a public health problem.59
T. dimidiata is the main vector. R. prolixus was detected in the country in the 1980s, but this species has since disappeared from El Salvador. T. dimidiata is the only vector currently detected in all Departments with a house infestation rate of 21% in the dwellings in rural areas and in the small or medium townships. In 2000 the prevalence of the infection in school children aged 7—14 years was 0.3% and 2.1% in the population older than 14 years.
The blood screening coverage was 100% in 2000 when the prevalence of infected blood was 2.48%. The vector control program treated in that year 67.3% of infested dwellings in areas where there is coexistence of infestation by anophelins and triatominos.
T. dimidiata is found in 18 of the 22 departments and R. prolixus in 5 departments. The infestation rate varies from 12% to 35%. The infection rate in school children in the five most endemic departments, namely, Zacapa, Chiquimula, Jalapa, Jutiapa, and Santa Rosa was 4.9% in a survey carried out in 2000. There is a poor blood bank control system and prevalence of seropositive blood donations in 2000 was 0.84%.
Vector control activities are carried out by the control program of the Ministry of Health in the mentioned Departments with highest house infestation rates.59 Interruption of transmission of T. cruzi by R. prolixus was certified in 2005.
The main vector R. prolixus is present in 11 departments of the country and the second vector T. dimidiata is present in 16 departments. Vectors are present in the departments of Choluteca, Comayagua, Copan, Francisco Morazan, Intibuca, Lempira, Ocotepeque, Olancho, El Paraiso, La Paz, Santa Barbara, and Yoro. In 1983, the highest infection rates were found in the western and eastern departments and in the southern region. About half of the population is estimated to be at risk. Infection rates of 32% or more in the vectors have been reported. The most frequent clinical manifestation is cardiopathy.
Vector control activities are carried out in six of the nine Health Regions of the country.
A recent seroepidemiological survey carried out in areas under chemical control in children aged less than 5 years was 0.36% and in school children aged 7—14 years was 3.3%. The coverage of the control of transfusional transmission is 100% and the national seroprevalence in blood donors in 2000 was 1.53% as compared to 11% in 1985.59 Interruption of transmission of T. cruzi by R. prolixus is in the process of certification.
Vectors and infected mammals are found in the states of Chiapas, Guanajuato, Guerrero, Hidalgo, Jalisco, Mexico, Michoacan, Morelos, Nayarit, Oaxaca, Puebla, Sonora, Yucatan, and Zacatecas. The prevalence of the disease is highest in the pacific coast states from Chiapas to Nayarit, in the Yucatan peninsula, and in some areas of the central part of the country. Although most of the human infections and clinical forms in Mexico are considered to be mild, there have been recent reports of some cases of mega-viscera. Mexico has not introduced routine screening for T. cruzi in blood banks where 850,000 donations are made every year and where around 12,760 units of blood could be infected.
There is no vector control program although there is a renewed interest of the health authorities to organize national and state vector control activities.
T. dimidiata is present in 14 of 17 departments of the country and R. prolixus in five departments. The control of transfusional transmission is made in 70% of the blood banks with a prevalence of infected blood of 0.33%. A seroepidemiological survey carried out in 2000 in school children showed a prevalence rate of 3.3% in this age group.59 Interruption of transmission of T. cruzi by R. prolixus is the process of certification.
The main vector is R. pallescens found inside the dwellings of the Chorrera district. This vector is present also in palms in the wild environment. T. dimidiata is also an important vector. There is no compulsory screening in blood banks or vector control programs.
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