Enfermedad de Chagas en México / Chagas disease in Mexico

Resumen México es un país endémico para la enfermedad de Chagas, donde dos terceras partes del territorio pueden ser consideradas en riesgo de transmisión vectorial, es decir que 1'100,000 individuos podrían estar infectados con Trypanosoma cruzi y 29'500,000 en riesgo de contraer la infección. En la morbimortalidad del padecimiento son importantes las características de la vivienda, condiciones biológicas, ambientales y factores socioculturales. El tamizaje en bancos de sangre, a la fecha, es de observancia obligatoria con una cobertura mayor al 92%. El diagnóstico no se establece frecuentemente debido al desconocimiento de la enfermedad por parte del personal de salud y de la población. La fase aguda generalmente pasa desapercibida y en la crónica, la patología se presenta principalmente en el corazón, con evolución lenta. La patogénesis de la miocardiopatía crónica es muy compleja y se presentan lesiones con mayor frecuencia en el sistema nervioso autónomo y miocardio, lo que genera trastornos en la conductibilidad y contractilidad del órgano. Se describen los principales mecanismos patogénicos implicados en el desarrollo de la enfermedad.

Abstract Mexico is a country endemic for Chagas disease in which two thirds of the territory can be considered at risk of vector-borne infection. This means that 1.1 million people could be infected with Trypanosoma cruzi and 29.5 million at risk of infection. Dwelling characteristics of poverty in these rural areas linked with biological conditions, lifestyle, environmental and sociocultural factors are important in the morbidity and mortality of the disease. Nowadays, the screening for the parasite is mandatory and at least 92% of blood banks are covered. The inadequate knowledge of the disease by the health personnel and the population limits the possibility of the diagnosis. The acute phase of the disease courses undetected. The main affected organ in Chagas disease is the heart, with a slow evolution; the pathogenesis of chronic cardiomyopathy is complex and lesions occur mainly in the autonomic nervous system and myocardium leading to disturbances in the conductivity and contractility of the organ. The main pathogenic mechanisms involved in the development of the disease are described.

Occurrence of hybrids and laboratory evidence of fertility among three species of the Phyllosoma complex (Hemiptera: Reduviidae) in Mexico

In seven studied communities of Western Mexico, triatomine specimens were sympatrically collected, some with atypical morphological characteristics in contrast to pure specimens, which were presumed to be hybrids. More than 200 specimens of Meccus pallidipennis and Meccus longipennis with brown-yellow markings on dorsal connexival segments were collected in Ahuacapán and Quitupan. In La Mesa, more than 60 specimens similar to Meccus picturatus in most morphological characteristics (including size) were collected, although they presented a largely yellowish corium like M. pallidipennis. Interfertility was proven between all of the studied wild hybrid specimens, as well as between all the experimental laboratory hybrids. Two different phenotypes (M. picturatus and M. longipennis) were obtained from crosses between M. picturatus x M. picturatus and M. longipennis x M. longipennis from the three studied localities in state of Nayarit as from La Mesita. Results support the hypothesis that the subspecific ranking of those triatomines may, therefore, be more appropriate because reproductive isolation has not been developed and complete interbreeding was recorded.

Evaluación de la función y sincronía de la contracción ventricular en pacientes con enfermedad de Chagas en estadio de latencia / Evaluation of the function and ventricular synchrony in patients with latency stage of Chagas' disease

OBJECTIVE: To compare the left ventricular function and the ventricular synchrony in patients with Chagas disease in latency stage respect to a control group. METHODS: We analyze a prospective, comparative, transversal and non randomized study of the left ventricular function (LVF) and the ventricular contraction synchronicity (VCS) in 36 subjects with positive serology for Chagas disease (18 males and 18 females), with mean of 15 +/- 5-years-old. The findings were compared with respect to 23 control volunteers (11 males and 12 females) with mean of 28 +/- 5-years-old. LVF and VCS were evaluated using equilibrium radionuclide angiography images (ERNA). The comparison of both Chagas and control populations was carried out by t Student test for independent samples, considering a statistically significant value of p < 0.05. RESULTS: The parameters of the ventricular function and the ventricular synchronicity in subjects with positive serology for Chagas disease were not statistically different with respect to the parameters of the control group. However, although they have a homogeneous contraction, the mean time of contraction for the right and the left ventricle is statistically smaller with respect to the control group. CONCLUSIONS: In clinically incipient stages of Chagas disease we do not found abnormalities in the ventricular function and the ventricular synchronicity. It's necessary to consider the follow up of the studied populations using indices for the identification of abnormalities of the autonomic nervous system.

Influence of temperature and humidity on the biology of Triatoma mexicana (Hemiptera: Reduviidae: Triatominae) under laboratory conditions

Several biological parameters related to the Triatoma mexicana life-cycle were evaluated in this study. Three cohorts were maintained under different combinations of temperature and relative humidity (RH): 25ºC/50 percent RH; 25ºC/75 percent RH; and 30ºC/75 percent RH. Observed hatching rates varied from 49-57.5 percent whereas the average time of hatching varied from 19.5-22.7 days. In the three cohorts studied, the mean time-lapse between presentation of the blood meal and the beginning of feeding was less than 5 min in all instars; the mean feeding time was longer than 10 min in all the instars; the post-feed defecation delay was over 10 min in all the instars. Less than 50 percent of nymphs in each cohort completed the cycle and the average time from 1st instar nymph to adult was more than 255 days for the three cohorts. The number of blood meals before molt at each nymphal instar varied from 1-9. Our results appear to indicate a lack of influence of temperature and RH on the biological parameters of T. mexicana that were studied, which could reflect the adaptation capacity of this species. We also conclude that T. mexicana can not be considered an effective transmitter of Trypanosoma cruzi to human populations in areas where this species is currently present.

Triatoma mexicana (Hemiptera: Reduviidae) in Guanajuato, Mexico: house infestation and seasonal variation

Triatoma mexicana was described by Herrich-Schaeffer in 1848. In 1940, a male specimen was found in Hidalgo. In 1970, this species was recorded in the state of Queretaro. Later, it was registered in Guanajuato and San Luis Potosi. In the present paper we performed an investigation in 545 dwellings from three counties in the state of Guanajuato, Mexico, from March 2003 to May 2004. The search and capture of triatomines were seasonally performed indoors and outdoors. Entomological indexes were calculated. The risk and no risk relations between triatomine presence and housing construction materials were analyzed. Fourteen triatomines were collected indoors and 151 outdoors. The vectors were collected in houses built with either risky and non-risky materials. Adults go indoors but do not settle there, hence, no relationship was found between the building materials and infestation of houses. Conventional interventions like house improvement or insecticide spraying are not efficient for the control of T. mexicana, because its developmental cycle is accomplished outdoors in the area surrounding the houses.

Insecticide and community interventions to control Triatoma dimidiata in localities of the State of Veracruz, Mexico

Three different interventions to control Triatoma dimidiata in the State of Veracruz were implemented: X-1 = whole dwelling spraying, X-2 = middle wall spraying, X-3 = household cleaning. Cyfluthrin was sprayed 3 times with 8 month intervals. After each spraying, insects were collected and sent to the laboratory to be recorded and to determine genus and species of the adult triatomine bugs, and nymphs were counted. Trypanosoma cruzi presence was determined. With X-1, the infestation, colonization, and natural infection indexes were reduced to 0 percent in the 3 localities, with respect to t0. With X-2, the infestation index was reduced to 10 percent at t3 in 3 localities; the colonization index was reduced to 0 percent in only 1 locality at t3, and the natural infection index was reduced to 0 percent at t3. With X-3 the 3 indexes were not effectively reduced but they decreased with respect to the baseline study. Insecticide application to the whole dwelling is a more efficient intervention than its application to only the lower half of the walls and to the cleaning of houses.

Detection of antibodies against Trypanosoma cruzi in blood donors in the General Hospital of Mexico city / Detection of antibodies against Trypanosoma cruzi in blood donors in the General Hospital of Mexico city

A doença de Chagas é um problema importante de súde pública no México, onde estimativas recentes demonstraram a prevalência de 540 mil indivíduos infectados com o Trypanosoma cruzi. Neste trabalho deterimnou-se a sororreatividade ao T. cruzi em 2.210 doadores de sangue, no perído de 1998-2000, de 28/31 estados de México, bem como da cidade do México. Todos os soros foram testados por meio de hemaglutinação indireta e do imunoensaio enzimático (ELISA. Aplicou-se, na ocasião, um questionário para obter dados sociodemográficos. Em seguida, os indivíduos foram levados a identificar visualmente o vetor (Triatoma pallidipennis) e a assinar uma carta de consentimento. Dos 2.210 casos soros, 151 foram positivos em ambos os testes. Os indivíduos eram provenientes de 12 estados e da cidade do México, sendo 85,4 por cento homens e 14,6 por cento mulheres. Somente 14 por cento (6/151) identificaram o vetor. Essa elevada soroprevalência foi atribuída não só ao local inde foi realizado o estudo, Hospital General de México, um centro nacional de atenção à saúde, que assiste a população de todo o país, masa também ao elevado movimento migratório das áreas endêmicas para a cidade do México.

Cuticular hydrocarbons of Chagas disease vectors in Mexico

Capillary gas-liquid chromatography was used to analyse the cuticular hydrocarbons of three triatomine species, Triatoma dimidiata, T. barberi and Dipetalogaster maxima, domestic vectors of Chagas disease in Mexico. Mixtures of saturated hydrocarbons of straight and methyl-branched chains were characteristic of the three species, but quantitatively different. Major methylbranched components mostly corresponded to different saturated isomers of monomethyl, dimethyl and trimethyl branched hydrocarbons ranging from 29 to 39 carbon backbones. Sex-dependant, quantitative differences in certain hydrocarbons were apparent in T. dimidiata

Manual de laboratorio para el diagnóstico de la infección por trypanosoma cruzi / Laboratory manual for diagnosis of infection by trypanosoma cruzi

Describe el proceso que se sigue en el laboratorio para la detección y el diagnóstico de la enfermedad de chagas . Contenido: 1) Introducción y epidemiología. 2) Antecedentes en México. 3) Biología del Tripanozoma cruzi (T. cruzi). 4) Vectores de T. cruzi. 5) Mecanismos de infección. 6) Clínica. 7) Patogenia. 8) Patología. 9) Respuesta inmune a la infección por T. cruzi. 10) Antígenos del T. cruzi en diagnóstico. 11) Diagnóstico de la infección por T. cruzi. 12) Métodos parasitológicos e inmunológicos. 13) Técnicas: parasitológicas, serológicas. 14) Control de calidad en el laboratorio. 15) Recolección y toma de muestras en bancos de sangre. 16) Importancia del tamizaje serológico. 17) Marco legal

Comportamiento biológico de triatoma pallidipennis en el estado de Morelos México / Biological behavior of triatoma pallidipennis in the state of Morelos México

T. pallidipennis was found naturally infected in localities of domestic, peridomestic and wild areas in the State of Morelos, México. In agreement with the triatomines high potentiality like vectors of T. cruzi, protozoan that causes Chagasïdisease and the Knowledge of these bugs in México, the aim of the present research was to collect triatomines for assessment of T. cruzi infection, to characterize and compare life cycles, identification of feeding preferences and observe indexes of experimental infectivity. Seven isolates of T. cruzi were obtained, from differents localities which curves of parasites showed different behaviors. Histopathological study, carried out by counting of amastigotes nests, which affected the gastrocnemius muscle and heard was observed. The life cycles of T. pallidipennis was completed in 131 days. The feeding preferences were rats, cats and pigs

Iniciativa México: propuesta para el control y vigilancia epidemiológica de la enfermedad de Chagas en México / Mexico iniciative: a proposal for the epidemiological control and surveillance of Chagas disease in Mexico

It is showed the proposal for the knowledge, control and epidemiological suverillance of Chagas diseases in Mexico

Estudio de la respuesta inmune humoral en cerdos infectados con huevos y posoncósferas de taenia solium / Study on immune humoral response in pigs infected with eggs and posoncospheres of taenia solium

Due to the importance of cysticercosis in Mexico and Latin America and to the fact that in the last years another mechanism of infection for this disease has been proposed, i.e. through postoncospheres and immunosuppression of the host, we have considered relevant to perform the present work, which consisted in assessing the immune response induced by dexamethasone as well as that produced by parasites in pigs infected with T. solium eggs, or postoncosphere-infected, and in postoncosphere-infected and dexamethasone treated animals. We used 10 recently weaned pigs, three were used as controls, two of them without the drug and one with it; two were infected with T. solium eggs; five with postoncospheres receiving also dexamethasone three of them. We evaluated the humoral response against parasite antigen using indirect haemagglutination (IH) and ELISA methods. Results of the immune humoral response revealed titres of up to 1:128 in T. solium eggs infected animals, of 1:16 in postoncosphere infected animals. Absorbance titres with of 1:32 towards the end of the experiment in postoncosphere plus dexamethasone animals. Absorbance titres with Elisa confirmed these findings. Data obtained by IH show that the antibody titres of the pigs challenged with postoncospheres and postoncospheres plus dexamethasone are positive as compared to the titres obtained in the pigs infected with T. solium eggs. Results from the Elisa confirmed this finding, since, from weeks 14 to 17, the pigs became positive, behaving as those pigs that developed cysticercosis. This is revelant as it indicates that the antiposcosphere antibodies recognized antigens of T. solium larvae

Validación del proceso de obtención de datos para un estudio sobre trypanosomiasis americana en el estado de Morelos, México / Validation of data colection process for an american trypanosomiasis epidemiological study in the state of Morelos, México

The purpose of this paper is to show up the importance of the standardization concepts in american trypanosomiasis epidemiological studies. The consistence in the measurement of some dwelling characteristics was evaluated. A validation of the queretaro antigen for indirect hemagglutination reaction as a diagnostic test and the interobserver concordance for the serologic readings were also made. The observers were instructed in some sessions. The pretests were made in the laboratory with positive and negative sera, with sera from the studied population. Results show that the interobserver concordance after the instruction, for the dwelling variables ranged from 70 percent to 100 percent. Sensitivity of the queretaro antigen was 100 percent, specificity 55 percent, the predictive value of a positive test 55 percent, and the predictive value of a negative test 93 percent. The interobserver concordance was 47 percent. The pretest and the pilot study are very important in getting the objetives of the principal study

First case of natural infection in pigs. Review of Trypanosoma cruzi reservoirs in Mexico

An epidemiological research project was performed in the State of Morelos including collection of samples for blood smears and culture, serological tests, and xenodiagnoses from a total of 76 domestic and peridomestic mammals. Two strains of Trypanosoma cruzi were isolated by haemocultures; one from a pig (Sus scrofa), the first case of natural infection reported in Mexico, and the other from a dog (Canis familiaris). This study summarizes current information in Mexico concerning confirmed reservoirs of T. cruzi.

Parasite search in strawberries from Irapuato, Guanajuato and Zamora, Michoacan (Mexico)

A seasonal research was carried out in Irapuato, Guanajuato and Zamora, Michaocan, Mexico, the location of the most important producers of strawberries, in order to assess fecal contamination through the findig of protozoan cysts and helminth eggs, specifically of Taenia sp eggs. Three techniques were used: direct observation, flotation and sedimentation. Low numbers of protozoan cysts and only one Ascaris egg were found. What is most interesting is that no Taenia eggs were identified. Results indicate that although strawberries are contaminated with human feces, contamination is minimal

Estudio cualitativo y cuantitativo de la presencia de posoncósferas de taenia solium en el tejido muscular de cerdos con y sin cisticercosis / Qualitative and quantitative study on taenia solium posoncospheres in pigs with and without cysticercosis in muscular tissues

It was determined the presence of posoncospheres in muscular tissues in 20 natural cysticercotic pigs and in 20 pigs apparently free of taenia solium metacestodes. Ten differents anatomical regions were dissected, giving 400 samples in total. The animals were slaugthered in Ecatepec, México State, México. The samples were kept in bottles with saline and were processed in the Laboratorio de Biología de Parásitos, Facultad de Medicina, Universidad Nacional Autónoma de México (UNAM); cysticercus were counted and later on the resulting muscular mass was grinded and observations were made in the sediment for posoncospheres search. Mann-Withney statistical method revealed meaningful differences between postoncospheres in cysticercotic pigs and not apparently cysticercotic pigs. The linear correlation analysis showed no relation between cysticercus quantity and postoncospheres quantity in the same samples. Postoncospheres were found in cysticercotic animals and in those apparently free of cysticercus, in the last group the quantity was bigger

Epidemiologia de la enfermedad de Chagas en una poblacion de Oaxaca, México / Epidemiologic study of Chagas' disease in a town in Oaxaca, México

A survey was made of residents and hospital patients in Miahuatlan, Oaxaca, México, for cases of Chagas'disease. This survey focused primarily upon 85 patients attending the local hospital who had clinical pictures suggesting the disease, 14 with possible acute cases and 71 with possible chronic cases. In addition, sera from 14 Miahuatlan blood donors were examined; seroepidemiologic testing was performed with 52 sera from schoolchildren at another community nearby, and triatomine bugs were collected from Miahuatlan residences. Each of the 85 patients provided a complete clinical history and blood specimen, and each was given an ECG and a series of heart X-rays or chest teleradiography. In some cases biopsy or necropsy speciments were obtained. A variety of parasitologic and serologic test performed with these specimens indicated chagasic infections in four of the 14 subjects with possible acute cases and eight of the 71 subjects with possible chronic cases. One of these latter subjects had the first case of Chagas'disease involving a megasigmoid that had ever been reported in México. A high proportion (78 percent of the sera from Miahuatlan blood donors tested positive for Trypanosoma cruzi antibodies by complement fixation, as did 88 percent of the sera from the 52 schoolchildren. A total of 57 triatomid vector insects were captured alive and tested for T. cruzi. Most (92 percent) were