Mitochondrial 16S DNA variation in populations of Triatoma infestans from Argentina

Variation in the mtDNA 16S ribosomal RNA gene in populations of Triatoma infestans (Klug) was surveyed. DNA sequence comparisons yielded 18 haplotypes among 130 individuals from 16 localities that represent a large proportion of the range of T. infestans in Argentina. The most common genotype in all populations was found in 76.9% of individuals and two other haplotypes were shared among different populations. The remaining 15 haplotypes were present exclusively in one of the populations, suggesting currently low levels of genetic exchange. Analysis of mtDNA 16S sequences uncovered substantial genetic variation among T. infestans populations. Haplotype and nucleotide diversities varied among populations, from 0% to 0.84% and 0% to 0.29%, respectively. It appears that this locus has a low mutation rate. Uncorrected pairwise differences of T. infestans haplotypes ranged from 0% to 1.2%. The molecular phylogeny supported the monophyly of T. infestans haplotypes and clustered two different pairs of haplotypes with a moderate degree of bootstrap support (approximately 60%). Mitochondrial DNA phylogeographic differentiation was not evident, suggesting a recent rapid spread of the species. Analysis of molecular variance showed hierarchical structure in the data. Considerably less variation was found among T. infestans populations from the northwest and northeast regions than among those belonging to the central area. Such a lack of variation may be indicative of one or more past population bottlenecks.

[Cutaneous leishmaniasis in Northern Argentina: identification of risk factors in a case-cohort study of three municipalities in Salta]

The objective of this work was evaluate risk factors for acquiring cutaneous leishmaniasis in Salta, the region with the greatest indices of transmission in Argentina. A Case-cohort study was realized from June 1989 to December 1992. The procedures performed on cases and controls included: a) socio-demographic questionnaire; b) domestic and peridomestic environment description; c) physical exam of skin and nasal and oral mucosal; d) Montenegro Skin Test. Multivariate analysis showed a significant risk for factors outside the home (cattle management, hunting, sleeping at the work place) and while at home (sleeping outside of the bedroom, presence of three or more pigs in the yard and windows that cannot be locked in the closed position). This association allowed the identification of risk factors linked to the transmission of leishmaniasis in the home for the first time in Salta (Argentina).

Humoral immune response to cruzipain and cardiac dysfunction in chronic Chagas disease

The humoral immune response to epitopes expressed on cruzipain was evaluated in 31 Chagas disease patients (CDP) with different degrees of cardiac dysfunction. We took advantage of the availability of anti-Trypanosoma cruzi microsomal fraction monoclonal antibodies (MoAbs) reactive with epitopes that are recognized (5A9B11) or not recognized (1A10C11) by CDP sera. The 5A9B11- and 1A10C11-like epitopes are expressed on cruzipain. The reactivity of 5A9B11 against cruzipain was completely inhibited by sera of severe cardiopathy patients while a partial inhibition was found with sera from chagasic patients with mild disease. CDP sera did not block cruzipain recognition by 1A10C11. The antigenic determinants recognized by CDP sera appeared to be linear and carbohydrate free. When the overall anti-cruzipain immune response was evaluated, 70% of CDP with severe disease showed cruzipain titers higher than 1/800 while none of them displayed titers lower that 1/400. This report shows for the first time that the humoral immune response against epitopes expressed on cruzipain appeared to be related with the severity of chronic Chagas disease.

[Regional differences and Hantavirus pulmonary syndrome]

Factors related to the characteristics of Hantavirus pulmonary syndrome in Argentina are described. Factors from different scientific fields converge to form the syndrome's analytical framework. Some of these factors are the history of spatial occupation, work and production structures, human migration patterns, ethnic composition, reservoir dynamics and its relationship to the different circulating viruses, and human behavior. Furthermore, the multiple factors are expressed in three ecological frameworks, associated with three different geographical regions of Argentina: 1) Northwest; 2) Central ("wet Pampa"); and 3) South Andean. In order to understand the actual causality of health or disease as an interaction of many factors, research on the primary biological, social, and environmental determinants of diseases should attend to the complexity of variable relationships in each region. The multiple-factor convergence approach allows for the design of appropriate strategies to improve the population's health status. Therefore, strategies should be developed and transferred by multidisciplinary teams, while their sustainability should be assured by community participation beginning with the earliest steps of research onward.

Assessment of Leishmaniasis notification system in Santiago del Estero, Argentina, 1990-1993

Using a capture-recapture method, this study evaluates the completeness of the cutaneous leishmaniasis (CL) surveillance system in four districts of Santiago del Estero province, Argentina, for the period 1990-1993. Four reporting sources were evaluated: medical records kept by health facilities, interviews conducted during a case-control study, and the national and provincial levels of the leishmaniasis surveillance system (LSS). Using the capture-recapture method it was estimated that 210 cases (95% confidence interval [CI]: 202-218) of CL occurred in the four districts during the study period. Completeness of reporting to the leishmaniasis surveillance system at the national level was estimated to be 44.8% (95% CI: 43.2-46.4). The study results indicate that there is substantial underreporting within the LSS, although it did show the appropriate secular trends. The reasons for under-reporting and methods for addressing this problem are discussed.

alpha 4 Integrins and sialyl Lewis x modulation in chronic Chagas disease: further evidence of persistent immune activation

We have previously shown that titers of soluble platelet selectin (s-P-selectin) and soluble vascular cell adhesion molecule-1 (s-VCAM-1) were increased in sera of patients with chronic Trypanosoma cruzi infection. In this study, we analyzed the expression of CD49d-integrins, that bind to VCAM-1, and sialyl Lewis x (SLe(x)), which binds selectins, in peripheral blood lymphocytes of 27 patients with Chagas' disease at different levels of disease severity. Patients with a mild form of Chagas' disease showed a lower number of CD49d(+) cells, in comparison with those with severe chronic cardiopathy. Decreased levels of CD49d(+) cells were detected in CD3(-) cell populations. Conversely, SLe(x) expression was found to be decreased in patients with severe Chagas' disease. Levels of soluble platelet endothelial cell adhesion molecule-1 (s-PECAM-1) were significantly increased in the plasma of patients with severe Chagas' disease while unaltered levels of MCP-1 were recorded. These data show that VCAM-1 and P-Selectin ligands are differentially expressed during the chronic phase of the Trypanosoma cruzi infection. These findings also reinforce a role of the P-selectin/SLe(x) adhesion pathway rather than very late antigen-4 (VLA-4)/VCAM-1, in the pathogenesis of Chagas' disease.

Tegumentary leishmaniasis in Northern Argentina: distribution of infection and disease, in three municipalities of Salta, 1990-1992

This work describes the epidemiological pattern of tegumentary leishmaniasis in an area north of Salta, Argentina. The prevalence and incidence were estimated by means of a cross-sectional study and two follow-up studies during two consecutive years. The Montenegro Skin Test (MST) was administered to 7336 subjects at baseline. The prevalence and incidence between 1990 and 1992 of infection (MST reactive) was 38 per mil persons and 4.5 per mil persons/year respectively. The prevalence and incidence of tegumentary leishmaniasis (presence of clinical signs) was 1.8 per mil and 0.8 per mil persons/year, respectively. A physical examination performed on 264 patients with MST reactive during three years revealed that 130 cases (49.2%) had some evident sign of infection (scar and/or lesion), with a clinical presentation compatible with leishmaniasis. Our study demonstrated that after the epidemic outbreak of 1985 the transmission in the study area returned to endemic levels in 1992, and also demonstrated the presence of the asymptomatic infection in the area.

Transfusion-transmitted infectious diseases in Argentina, 1995 through 1997

BACKGROUND

Assessment of the safety of the blood supply, the quality of screening procedures, and the risk of transfusion transmission of infectious diseases in any country can be estimated by reviewing the records of blood donations and screening procedures and the prevalence of serologic markers of infectious diseases.

STUDY DESIGN AND METHODS

Information on blood donors, particularly the number of screened donors, and on the prevalence of serologic markers of infectious diseases was available from Argentina for 1995 through 1997. This information permitted the estimation of the risks and costs of preventing transfusion transmission of infectious diseases within the country during this period.

RESULTS

Screening coverage was higher in the private sector. The proportion of donors screened for HIV increased from 84.52 percent in 1995 to 97.97 percent in 1997; in the same period, serologic screening for HbsAg increased from 83.71 percent to 98.48 percent; that for HCV from 69. 92 percent to 97.83 percent; and that for syphilis from 87.94 percent to 98.71 percent. One hundred percent of donors were screened for Trypanosoma cruzi throughout the period. The overall prevalence of HIV per year varied from 2.42 to 3.36 per 1,000 donors; that of HBV, from 5.80 to 9.76 per 1,000; of HCV, from 7.39 to 16.61 per 1,000; and of syphilis, from 5.25 to 7.65 per 1,000. The overall prevalence of antibodies to T. cruzi ranged from 36.53 to 49.20 per 1,000 donors. The overall index of the spread of infectious viral disease through blood transfusion decreased from 47. 74 per 10,000 donations in 1995 to 4.75 per 10,000 in 1997. The ratio of acquired infections to donations improved from 1:209 to 1:2, 102 during the same period. The risk of T. cruzi infection from 1995 through 1997 was, in theory, nil, given the 100-percent screening. The greatest threat to the quality of the blood supply throughout the period studied was HCV.

CONCLUSION

The status of the blood supply in Argentina improved steadily from 1995 to 1997, as shown by the increase in screening coverage.

Molecular and biologic characterization of Leishmania parasites implicated in an epidemic outbreak in northwestern Argentina

Leishmania (Viannia) braziliensis and its variants were implicated in the epidemic outbreak of mucocutaneous leishmaniasis that occurred in Salta, northwestern Argentina, in 1985. A total of 24 suspected, untreated cases were evaluated clinically and parasitologically. Four of five stable isolates were consistent with the reference strain of L. (V.) braziliensis as determined by monoclonal antibodies and indirect immunofluorescence or radioimmunobinding assays. Zymodeme analysis in agarose gels showed a close relationship with L. (V.) guyanensis and L. (V.) panamensis. All zymograms obtained with polyacrylamide gels belonged to the subgenus Viannia; the patterns were different from, but very closely related to, the reference strains of L. (V.) braziliensis as determined by dendrogram analysis. Hamsters infected with two isolates showed a pattern consistent with L. (V.) braziliensis. The pattern of development in the gut of Lutzomyia longipalpis was consistent with members of Viannia.

Congenital transmission of Trypanosoma cruzi: an operational outline for detecting and treating infected infants in north-western Argentina

We designed a set of procedures for first-line local health services to detect and treat the congenital transmission of Trypanosoma cruzi at a province-wide scale, and field-tested the programme in the province of Tucumán, northwestern Argentina, from 1992 to 1994. The programme consists of routine screening of pregnant women for seroreactivity to T. cruzi, serological and parasitological follow-up of the newborn at least twice during the first year of age, treatment of the infected infants, and evaluation of the outcome. 927 (5.5%) of 16 842 pregnant women were seroreactive to T. cruzi by indirect haemagglutination assay and ELISA. Twenty-one (6.7%) of 315 newborns to seroreactive mothers were diagnosed as infected with T. cruzi parasites microhaematocrit concentration before 30 days of age. Five newborns who initially tested negative had a T. cruzi infection detected by microhaematocrit and/or serological techniques at 3 or 6 months of age. Thus, congenital infection was diagnosed in 26 (7.1%) infants born to seroreactive women and residing in houses free of triatomine bugs. Four of 6 infants born to seroreactive mothers died during the first year of age and had some evidence of T. cruzi infection; one of the deaths was attributed to T. cruzi based on clinical evidence. After specific treatment with nifurtimox or benznidazole, 30 of 32 infants remained parasitologically and serologically negative. This study shows the feasibility of controlling the incidence of congenitally acquired T. cruzi infections at a province-wide scale by means of a specific screening programme at first-line health services level.

[Control of the transmission of Trypanosoma cruzi in Argentina 1999]

Approximately 2 million people in Argentina are infected with Trypanosoma cruzi, the etiologic agent of Chagas disease, thereby constituting the major tropical disease in the country. As in other six Southern Cone countries, Triatoma infestans is the only or major vector of T. cruzi among human and domestic animals. In Argentina, a vertically structured National Chagas Control Program was established in 1962. Such a program pursued the elimination of domestic and peri-domestic populations of T. infestans through insecticidal spraying, and the serological control of blood donors to prevent transfusion-related infections. This program strongly reduced the nation-wide serological prevalence of T. cruzi in the population. For example, in 18 or 20 year-old men drafted into military service, the seroprevalence decreased from 10.1% in 1964 for those who had been born in 1944 to 1.9% in 1993 for those born in 1975. However, the vertical strategy failed to reach and sustain the surveillance phase in widespread rural areas with disperse populations due to its intrinsic limitations and the reduced priority level assigned to rural health programs. An alternative, horizontally-structured control strategy of T. infestans was developed and assayed in the Province of Santiago del Estero between 1985-1989, and 1991-1992. The projects demonstrated that insecticidal spraying carried out with community participation combined effectiveness and commitment in such a way as to produce a strong impact on house reinfestation and the extension of the area under entomological surveillance. This experience has been transferred in a chain of responsibilities to the personnel of the National Chagas Control Program, using participating workshops, procedural guidelines, and practical training. This personnel transferred the strategy using similar methods to the field health care agents and volunteers chosen by their own communities (community leaders). After the workshops, the leaders received all the materials needed to install and develop the ongoing surveillance activities: third generation pyrethroid insecticides, manuals, hand-operated sprayers, and sensor boxes to detect domiciliary infestations. From 1993 to 1998, a total of 15,000 health care agents or community leaders were trained. A total of 675,000 houses were sprayed with residual insecticides in the attack phase, and 850,000 houses entered the surveillance phase. This is the first time that such large coverage has been accomplished in Argentina. The network of laboratories installed a quality assurance program to current serological procedures applied to blood donors, organ transplant, and the detection and treatment of newborns to women sero-reactive for T. cruzi in Argentina. We expect to interrupt the vector-mediated transmission of T. cruzi in the next 18 months, but the sustainability of such a program depends on, at least, additional work with the community to achieve a change of attitudes and practices related to house infestation for the next 10 years. A social effort will be needed to cover those expenses, but the expected economic returns exceed largely the cost of any such program, as suggested by cost-benefit studies. To illustrate, the annual treatment costs of one Chagas patient can help maintain 25 households free from triatomine bugs in Argentina.

[Treatment of Trypanosoma cruzi infection in the indeterminate phase: experience and current guidelines in Argentina]

An effective treatment for Trypanosoma cruzi infection has been investigated, since the 30s. The goals of the specific treatment against T. cruzi infection are, at the individual level, to eliminate the parasite, and to reduce the probability of developing Chagas disease. At the end of the 60s and at the beginning of the 70s, two compounds were clinically investigated in Argentina: Nifurtimox and Benznidazole. After the approval by the Ministry of Health, in 1983 the first guidelines for the treatment of T. cruzi infection were proposed and approved. These guidelines recommended the treatment of cases in the acute phase. Due to the publication of new information in support of the utility of these drugs for treating cases in the indeterminate phase of Chagas disease, in 1997 the original guidelines were revised and new procedures were approved. At present, the treatment is recommended for: 1) all patients undergoing the acute phase; 2) children and young people undergoing the indeterminate phase; 3) adult patients undergoing the indeterminate phase or with incipient heart lesions; 4) laboratory accidents and during surgery, and 5) organ transplant recipients or donors. The general clinical laboratory control is needed for the intra-treatment monitoring of the patient. Titration of specific antibodies with monospecific antigens has been shown to be an adequate marker of therapeutic efficacy.

[Control of congenital transmission of Trypanosoma cruzi in Argentina]

The vertical transmission of Trypanosoma cruzi has been augmenting its relative importance as vector and transfusion-mediated transmission routes have been, and continue to be, increasingly controlled. The vertical transmission of T. cruzi cannot be prevented; but early detection and treatment of congenital infection achieve cure rates close to 100%. In Argentina, the Subprogram of Control of Pregnant Women examined 58,196 women from 13 provinces in 1997 and found a 9% seropositivity to T. cruzi. In spite of such high maternal prevalence rates of T. cruzi, only a small proportion of live newborns to infected mothers acquires the infection. The probability of vertical transmission was 1.9% (range: 0.1% to 3.5%) in surveys carried out in the '70s, and 2.5% (range: 0.7% to 10.4%) in others conducted in the '70-'80s. Other more recent studies in Argentina estimated the probability of transmission in 2.6%-6.7%, but studies from Paraguay estimated 10.5% by PCR or serodiagnosis. The microhematocrit technique is the recommended parasitologic method to detect congenital infection. Routine serodiagnosis that detects IgG against T. cruzi is only helpful after the newborn reaches 6 months of age. Detection of specific IgM using recombinant antigens and PCR constitute excellent alternatives, but their feasibility from operational and cost-effective viewpoints in affected endemic areas remains to be considered. In a longitudinal project carried out in Maternidad Nuestra Señora de la Merced in the city of Tucumán between 1992-1994, the majority of congenital cases were asymptomatic. They were diagnosed through the microhematocrit technique, but a number of cases could only be detected later as a result of the parasitological and/or serological follow-up. Of a total of 32 newborns infected with T. cruzi who were treated with nifurtimox or benznidazole, 30 had a negative microhematocrit and serodiagnosis between 6 months and 2 years post-treatment. The magnitude of congenital transmission, and its associated morbidity and mortalidad, largely justify the efforts needed to detect T. cruzi infection in the mothers and newborns. This project demonstrated that the transmission of T. cruzi can be successfully controlled at a provincial scale through a specific program inserted in the primary health care system or at the first level of attention. The congenital transmission of T. cruzi clearly represents a public health problem in areas that in the past were of active transmission, even years after being under entomologic surveillance.

Long-term effects of a nationwide control program on the seropositivity for Trypanosoma cruzi infection in young men from Argentina

Unselected nationwide cohorts of Argentine men 18 years of age summoned for military service were tested for antibodies to Trypanosoma cruzi each year from 1981 to 1993. After an initial screening using indirect hemagglutination test, the positive sera were retested by titrated indirect hemagglutination and immunofluorescence antibody tests at 39 laboratories or at the national reference center in Buenos Aires. Nearly 1.8 million men were examined for T. cruzi antibodies using the same standardized procedures under a quality assurance program. The prevalence of seropositivity for T. cruzi decreased significantly from 5.8% in 1981 to 1.9% in 1993, but the decrease was not homogeneous among provinces within each region or constant over time. Prior to the nationwide control campaign initiated in 1961-1962, 15 provinces had high (> 20%) percentages of houses with domiciliary infestation by Triatoma infestans bugs, which decreased to nine provinces in 1982, and four provinces in 1992. The observed decrease in the prevalence of seropositivity for T. cruzi may be mostly attributed to the spraying with insecticides to eliminate the domiciliary populations of Triatoma infestans. The lack of a sustainable triatomine surveillance program set a limit to the decrease of seropositivity rates and prompted a revised strategy based on community participation.

Development and evaluation of a solid-phase enzyme immunoassay based on Andes hantavirus recombinant nucleoprotein

Hantavirus pulmonary syndrome (HPS) with high mortality rate has been reported in five countries in South America. Rapid accurate methods are important both for monitoring acute infections and for epidemiological studies. The Andes virus nucleoprotein amino acid sequence has a high identity percentage compared with other sequences of this region and has been chosen for the development of diagnostic reagents. Andes nucleoprotein expressed in Escherichia coli was applied as antigen in IgG, IgA and mu-capture IgM enzyme-linked inmunosorbent assays (ELISAs). An evaluation of this reagent was conducted to establish its usefulness for differential diagnosis of HPS and seroprevalence studies. Samples from 135 reverse transcription (RT)-PCR-confirmed HPS cases, 77 individuals with other respiratory infections and 957 healthy inhabitants from endemic and non-endemic areas were analysed. The hantavirus-infected patients had an early and strong IgM, IgG and IgA serum antibody response, in most of the cases as early as 1, 7 and 1 days following onset of symptoms, respectively. IgM and IgG detection showed a specificity and sensitivity of 100%. Andes-specific IgM antibodies were found in all patients in the first available sample, which remained detectable for at least 43 days. Specific IgA antibodies were also detected in saliva of patients with acute HPS. The short duration of the disease and the risk for contacts due to person-to-person transmission of Andes virus necessitate the use of highly sensitive tests which might lead to earlier detection of infected people and improve the treatment and management of patients with HPS.

Soluble platelet selectin (sP-selectin) and soluble vascular cell adhesion molecule-1 (sVCAM-1) decrease during therapy with benznidazole in children with indeterminate form of Chagas' disease

The immune response against Trypanosoma cruzi infection has been associated with both protection and pathogenesis. Central events in host defence system- and immune-mediated damage are tightly regulated by cell adhesion molecules (CAM). Levels of sP-selectin and sVCAM-1 were measured in sera from 41 children with the indeterminate phase of Chagas' disease. Simultaneously, levels of soluble adhesion molecule were also quantified in Chagas' disease children undergoing specific chemotherapy with benznidazole. Levels of sP-selectin and sVCAM-1 were found to be elevated in children with indeterminate Chagas' disease before aetiologic therapy was started. However, a small group of patients showed sP-selectin and sVCAM-1 levels comparable to those of non-infected children. A positive correlation between levels of sVCAM-1 and sP-selectin in sera from Chagas' disease patients was found. There was a significantly greater decrease in the titres of sP-selectin and sVCAM-1 in those children receiving benznidazole therapy compared with those children receiving placebo. Measurement of soluble adhesion molecules revealed differences in the activation of the immune system in children with the indeterminate form of Chagas' disease. The early decrease of sP-selectin and sVCAM-1 levels after anti-parasitic treatment suggests that these molecules might be valuable indicators of effective parasitologic clearance.

Chagas' disease in patients with kidney transplants: 7 years of experience 1989-1996

Chagas' disease was present in 17.22% of persons undergoing kidney transplantation in an Argentine Hospital. The criterion for attributing reactivation of chronic Chagas' disease and transmission of Trypanosoma cruzi to grafts was detection of parasites in blood (patent parasitemia) or tissues. Reactivation was diagnosed in 5 (21.7%) of 23 recipients. Ten (43.4%) of 23 chagasic recipients without reactivation of chronic Chagas' disease had abrogation of serological reactivity. T. cruzi infection was transmitted to 3 (18.7%) of 16 non-chagasic recipients. Reactivation and infection were diagnosed by patent parasitemia or cutaneous panniculitis. For diagnosis, detection of parasites in blood and tissues had more relevance than serology. Sequential monitoring detected early reactivation and infection, permitting application of preemptive or therapeutic therapy with benznidazole, thus inhibiting, in all patients, severe clinical disease produced by a progressive and systemic replication of the parasite.

The cytostome of Trypanosoma cruzi epimastigotes is associated with the flagellar complex

Okuda, K., Esteva, M., Segura, E. L., and Bijovsky, A. T. 1999. The cytostome of Trypanosoma cruzi epimastigotes is associated with the flagellar complex. Experimental Parasitology 92, 223-231. Proliferative forms of Trypanosoma cruzi, amastigotes and epimastigotes, have a cytostome, a specialized structure formed by an invagination of the flagellar pocket's membrane surrounded by microtubules and frequently followed by a row of vesicles. All this assemblage penetrates deeply into the cytoplasm overpassing the nucleus. This structure, together with the flagellar pocket, appears to play an important role in the nutrition of the parasite. We demonstrated that the monoclonal antibody 2C4, made-up against isolated flagellar complex of T. cruzi epimastigotes, recognizes a protein doublet of 76 and 87 kDa in total epimastigotes homogenate. The 76-kDa polypeptide is enriched in the detergent-soluble fraction whereas the 87-kDa polypeptide is highly represented in the insoluble fractions and the purified flagella. Immuno-fluorescence assays show the antigen as a small spot at the flagellar pocket region. Immunogold labeling of ultrathin sections of epimastigote forms reveals gold particles at the opening of flagellar pocket, concentrated in the cytostome region. Immunocytochemistry of epimastigote whole-mount cytoskeletons reveals the labeling on an array of three to four microtubules that appears attached to flagellum, running in the direction of the nucleus. Ultrastructural observations have shown that the posterior region of isolated flagella, corresponding to the level of the flagellar pocket, possesses a microtubular structure compatible with that from the cytostome. The relationship between the cytostome, an endocytic organelle, and the flagellum is here described for the first time.

Identification of immunodominant antigens in Mexican strains of Trypanosoma cruzi

Chagas disease represents an important public health problem. In Mexico most studies have been performed using Trypanosoma cruzi' antigens extracted from strains of other geographical origins. This work was aimed at developing a reactive antigen to perform serological diagnosis of Chagas' disease, using Mexican T. cruzi strains. We prepared antigenic extracts from epimastigotes, trypomastigotes and sphaeromastigotes of three Mexican strains. Parasites homogenate was obtained by lysis and sonication, solubilized proteins were analyzed by SDS-PAGE, Western-blot assays, and ELISA to determine the reactivity against sera from chagasic reference serum and chagasic and leishmaniasic patients and healthy donors. Western Blot profiles revealed, with the reference serum, eleven main components between 212 to 25 kDa; however, five bands corresponding to 74, 44, 31, 25 and 18 kDa antigens were recognized by the T. cruzi reactive sera from Mexican chagasic patients, which did not cross-react with Leishmania mexicana. Antigens from the Tequesquitengo strain yielded the best reactivity in the enzymatic immunoassay, thus enabling us to propose their use for serodiagnoses of Chagas' disease in Mexico.

[Clinical features and diagnosis of mucocutaneous leishmaniasis in patients of an endemic area in Salta]

A total of 39 patients with a clinical diagnosis of mucocutaneous leishmaniasis, in an endemic area for leishmaniasis in Salta, Argentina, were examined between June 1990 and December 1992. Of these cases, 87% (34/39) presented the cutaneous simple form, 10.3% the cutaneous multiple form and 2.6% the mucosal form. Lesions were more frequently located in legs and arms (71.8%), followed by trunk and multiple location (10.3%). Of the patients, 43% were housewives, students or children, suggesting that the infection could be contracted in the domestic or peridomestic environment. Of 39 patients diagnosed, in 22 (56.4%) the parasite was found. Direct microscopy (smear) permitted a diagnosis in 13 (59.4%) of these 22 patients. Among these, 5 (22.7%) had positive diagnosis by culture, and 9 (40.9%) by inoculation in hamsters. Ten parasite isolates (45.4%) were obtained. The smear is recommended as a diagnostic method for epidemiological surveillance due to the sensibility demonstrated herein and its easy application in the endemic area. The time of clinical evolution, from the appearance of the lesion up to the detection of the patient by Sanitary Agents, was approximately 90 days. This would be related to the frequency of the visits, usually every 3 months. Only one of 30 treated patients had a relapse at 6 months, due to non fulfillment of the treatment.

Household prevalence of seropositivity for Trypanosoma cruzi in three rural villages in northwest Argentina: environmental, demographic, and entomologic associations

Environmental, demographic, and entomologic variables were analyzed by logistic multiple regression analysis for their association with the likelihood of being seropositive for Trypanosoma cruzi in three highly infested rural villages of northwest Argentina. The prevalence of seropositivity for T. cruzi, as determined by the composite results of three serologic tests, was 34% among 338 persons in 1992. The strongest positive predictors of the adjusted odds of being infected were the household number of dogs, the density of T. cruzi-infected Triatoma infestans in bedroom areas, and each person's age. Dwellers from houses with roofs made completely or partly with a grass called simbol, or which used insecticides rudimentarily and nonsystematically, had a significantly lower odds of being seropositive for T. cruzi than residents from other types of dwellings. The adjusted odds of infection also increased with the number of T. cruzi-infected dogs or cats and the presence of chickens in bedroom areas. No significant effects on the adjusted odds of infection of a community-wide deltamethrin spraying carried out in one of the villages seven years before were detected. Socioeconomic indicators, such as domiciliary area, and numbers of corrals and livestock, were inversely related to being infected. Our study identified several manageable variables suitable for control actions, most of them not examined before in univariate or multivariate analyses. Environmental management based on low-cost housing with appropriate local materials and removal of domestic animals from domiciliary areas have a crucial role to play in the control of Chagas' disease in rural areas.

Efficacy of chemotherapy with benznidazole in children in the indeterminate phase of Chagas' disease

A double-blind, randomized, clinical field trial was designed to test the efficacy and tolerance of a specific drug treatment in children in the indeterminate phase of infection by Trypanosoma cruzi. Children were treated with benznidazole at a dose of 5 mg/kg/day for 60 days or placebo and followed-up for 48 months. The treated children showed a significant decrease in geometric mean titers of antibodies against T. cruzi measured by indirect hemagglutination, indirect immunofluorescence, and ELISA. After a four year follow-up, 62% of the benznidazole-treated children and no placebo-treated child were seronegative for T. cruzi when tested by an ELISA using a T. cruzi flagellar calcium-binding protein (F29). Xenodiagnosis carried out after 48 months of follow-up was positive in 4.7% of the benznidazole-treated children and in 51.2% of the placebo-treated children. These results show the tolerance to and efficacy of benznidazole against T. cruzi in seropositive children six to 12 years of age. We used an early serologic marker of cure after treatment, consisting of a recombinant antigen implemented in a rapid, conventional serologic procedure.

Immunodiagnosis of Trypanosoma cruzi (Chagas' disease) infection in naturally infected dogs

This study reports on the standardization of an enzyme-linked immunosorbent assay (ELISA) for detecting specific antibodies anti-Trypanosoma cruzi in naturally infected dogs. Sera from 182 mongrel dogs of all ages residing in four rural villages in Santiago del Estero, Argentina, were collected in November 1994 and preserved in buffered neutral glycerin. All sera were tested by indirect hemagglutination test (IHAT), indirect immunofluorescence test (IFAT), and ELISA using the flagellar fraction of T. cruzi as antigen. Dog sera from an area without vectorial transmission were used to calculate ELISA specificity and cut-off value. Eighty-six percent of sera had concordant results for all tests. All sera reactive for IHAT and IFAT were also reactive for ELISA, except in one case. Sera tested by ELISA when diluted 1:200 allowed a clearer division between non-reactive and reactive sera than when 1:100 with greater agreement among serologic techniques. The specificity of ELISA was 96.2%. Among 34 adult dogs with a positive xenodiagnosis, sensitivity was 94% both for ELISA and IFAT. ELISA is the first choice for screening purposes and one of the pair of techniques recommended for diagnostic studies in dog populations.

Influence of humans and domestic animals on the household prevalence of Trypanosoma cruzi in Triatoma infestans populations in northwest Argentina

In three rural villages of northwest Argentina, the overall proportion of domiciliary Triatoma infestans infected with Trypanosoma cruzi was 49% among 1,316 bugs individually examined for infection in March and October 1992). Most of the variation among individual households in the proportion of infected triatomines was explained by variations among houses in the proportion of bugs that fed on dogs or cats, the prevalence of infected dogs or cats, and the proportion of bugs that fed on humans, according to a logistic multiple regression analysis. The effects of human infection rates on bug infection rates were not statistically significant. After adjusting for the effects of other predictors, the presence of chickens in bedroom areas had negative and significant effects on the proportion of infected Triatoma infestans, and positive and significant effects on the number of T. cruzi-infected triatomines collected per person-hr per house. Dog or cat infection rates and the proportion of bugs that fed on dogs or cats and on chickens explained 80% of the total variance of infected-bug numbers in a linear multiple regression model. This is the first study to use detailed field data to show that variations in triatomine infection rates depend on bug host feeding patterns and dog or cat infection rates, while the presence of chickens in bedroom areas exerts opposite effects on the proportion and number of infected triatomines. Domestic animals play a crucial role in the domiciliary transmission of T. cruzi.

Quality assurance of the serologic diagnosis of Chagas' disease

A quality assurance program of the Chagas' disease laboratory network of Argentina has been conducted by the National Reference Center since 1988, with the aim of assessing the reliability of serologic test results. Chagas' disease is endemic in Argentina, but the prevalence of seropositivity for Trypanosoma cruzi among 18- to 20-year-old men decreased from 5.8% in 1981 to 1.8% in 1994. About 600 laboratories form the Chagas' disease laboratory network, with main central laboratories in each of the 24 provinces in Argentina. The quality assurance program promotes regular use of good laboratory practice and internal and external quality control to improve performance of the participants; it also provides technical assistance and guidelines. Eventual corrective measures are discussed in workshops. Results of the first external evaluation by proficiency testing of serum panels and confirmation of results for 58 of the main laboratories reveal that from 1988 to 1994 the rate of agreement has increased.

Leishmania (Viannia) braziliensis: biological behavior in golden hamsters of isolates from Argentine patients

This study reports intraspecific variations of native isolates of Leishmania (Viannia) braziliensis from patients with leishmaniasis from Salta, Argentina. These isolates induced skin lesions in golden hamsters, initially showing rapid development, reaching their largest size between 28 and 35 days postinfection (PI). Thereafter, the infections were self-limiting and total regression was observed at 80-150 days PI. The majority of the native isolates were characterized by low infectivity in the experimental animals, and a classic pattern of dissemination to systemic organs was established. However, unusual features for L. braziliensis were displayed by two isolates; one showed evidence of high infectivity in hamsters characterized by a short prepatent period and larger, severe and persistent lesions at the inoculation site. The other isolate, of low infectivity, showed cutaneous metastasis and recurrent systemic dissemination in the same animals, suggesting dissociation between infectivity and pathogenicity. Metastasis has been frequently described in hamsters infected with L. (V) guyanensis and L. (V) panamensis, but not in infections induced by L. (V) braziliensis, as was observed in this study. Active and/or regressive histopathologic lesions were observed, depending on the stage of the infection. An exudative and mixed inflammatory pattern with microabscesses and necrotic areas was observed during early infection, while well-defined granulomas and collagen formation were the predominant features detected at a later time. Amastigotes were easily detected in the tissues, although in low numbers. Schaumann bodies were always detected. The characterization of the unique features of these native isolates, and the verification of their reproducibility in vitro and in vivo will be useful tools in tests related to immunoprophylaxis and chemotherapy.

Trypanosoma cruzi: specific detection of parasites by PCR in infected humans and vectors using a set of primers (BP1/BP2) targeted to a nuclear DNA sequence

In the present work we evaluate Trypanosoma cruzi DNA detection by PCR using the nuclear oligonucleotides BP1/BP2 as primers. These primers are targeted to the 5' and 3' ends of the coding region for the flagellar protein F29. An amplification product of BP1/BP2 is a DNA band 692 bp long. Titration assays were performed to evaluate the minimum amount of parasite DNA that can be detected by this assay, resulting in 10 fg (equivalent to about 1/20 of the genome). The assay was also performed using T. cruzi DNA from different strains, clones, and human-derived isolates obtaining, in all cases, amplification products. No DNA amplification was observed when the PCR was performed using DNA from Leishmania braziliensis, but when T. rangeli DNA was used, a 615-bp-long fragment was amplified. Under appropriate gel conditions T. cruzi and T. rangeli DNA amplicons could be differentiated. When both conventional xenodiagnosis and PCR detection of parasite DNA in the feces of insect vectors fed with blood from infected patients were compared, 10 of 20 samples were positive by both techniques. However, 2 other samples with positive serology were also positive by PCR. When PCR was performed on blood samples from infected and uninfected individuals, 62 of 65 serologically positive human samples amplified the BP1/BP2 692-bp T. cruzi DNA fragment (sensitivity >95%). The 3 negative samples were positive when Southern blot hybridization was performed using the radiolabeled PCR amplification product as probe (sensitivity 100%).

Inhibition of trypomastigotes' infectivity by a monoclonal antibody directed to a glycoconjugated fraction of epimastigotes of Trypanosoma cruzi

In this work it was shown that the infectivity of trypomastigote forms of Trypanosoma cruzi was affected upon the interaction with the Monoclonal Antibody (McAb) 2E9, which was raised against a glycoconjugated fraction of membranes of epimastigotes (Tulahuen strain). Characterization of the epitope recognized by this McAb, as well as its effects on complement mediated lysis and host cell invasion are reported. Immunocytochemical analysis showed that the McAb was reactive with two macromolecules (41-58 kDa) present on Trypanosoma cruzi epimastigotes (Tulahuen and Y strain), while it recognized several trypomastigotes macromolecules, showing a more intense reactivity with a band of 80 kDa. By indirect immunofluorescence, it was found there were subpopulations of blood and tissue culture derived trypomastigotes which attach the antibody to varying degrees. Studies using chemical or enzymatically treated antigens suggested that the McAb 2E9 was directed against carbohydrate epitopes, which were identified as being--galactosyl residues. In addition, preliminary results are shown, suggesting that the epitope recognized by the McAb 2E9 is involved in adhesion/or internalization of trypomastigotes.

An unusual hantavirus outbreak in southern Argentina: person-to-person transmission? Hantavirus Pulmonary Syndrome Study Group for Patagonia

Hantavirus pulmonary syndrome is a rodent-borne zoonosis first recognized in the United States in 1993. Person-to-person transmission has not been reported; however, in the outbreak of 20 cases reported here, epidemiologic evidence strongly suggests this route of transmission.

Epitopes common to Trypanosoma cruzi and mammalian tissues are recognized by sera from Chagas' disease patients: prognosis value in Chagas disease

Monoclonal antibodies (MoAbs) raised against Trypanosoma cruzi microsomal fraction (Mc) and cross-reactive with mammalian tissues were used to evaluate the ability of cross-reactive T. cruzi antigens to induce an immune response in Chagas' disease. Thus, we studied the ability of sera from Chagas' disease patients (CDP) with different degrees of cardiac dysfunction to block the immune recognition of these MoAb to the target antigen determining for each serum an inhibition index (II). By means of this approach we inferred that blocking of monoclonal antibody binding to T. cruzi microsomes by subjects' serum represents antibodies with the same reactivity. After serological and medical examinations, individuals were separated into the following groups: Chagas' disease patients without manifest cardiac involvement (CDP-0), CDP with suspected or borderline cardiac disease (CDP-1), CDP with moderate myocardial dysfunction (CDP-2), CDP with overt cardiac dysfunction (CDP-3) and controls including healthy subjects (HS) and patients with idiopathic myocarditis (IMP). The reactivity between MoAb 5F2 and its target antigen was significantly (p < 0.05) inhibited by sera from CDP irrespective of the clinical stage [CDP: n = 46, 50 +/- 20, mean II +/- SD: control: n = 16, 18 +/- 8]. Moreover, 5F2 was able to distinguish (p < 0.05) sera from CDP with mild disease (CDP clinical grade 0/1: n = 26, 34 +/- 18) from that of CDP with severe disease (CDP clinical grade 2/3: n = 20, 67 +/- 7). Moreover, the inhibitory capacity of sera from asymptomatic CDP (CDP-0) correlated with patients age (r = 0.66, p < 0.05). CDP-0 below or equal 40 years of age had results (n = 15, 25 +/- 13) comparable (p > 0.05) to that of controls while mean inhibition of CDP-0 over 40 years of age (n = 5, 60 +/- 5) was indistinguishable (p > 0.05) from that of patients with severe disease. Competitive assay with MoAb 5A9B11 also showed significant differences (p < 0.05) between sera from CDP (n = 46, 46 +/- 24) and controls (n = 13, 5 +/- 5). On the contrary, the differences observed between CDP with different cardiac involvement was not significant (mild: n = 26, 31 +/- 22; severe: n = 20, 66 +/- 11). However a thorough study of data from asymptomatic sera revealed the existence of two levels of reactivity, with low and high capacity to inhibit the reaction of 5A9B11 against Mc. On the contrary, CDP sera showed a blocking activity for 1A10C11 comparable to that of controls (CDP: n = 25, 19 +/- 9; control: n = 12, 14 +/- 6). Some cross-reactive MoAbs recognized epitopes partially composed of carbohydrates. Interestingly, 5F2 and 5A9B11 epitopes did not appear to have carbohydrates moieties. In summary, immunoinhibition assays revealed differences in the immune response of chronic chagasic patients against parasite epitopes. These results have opened the possibility to identify a prognosis marker of the disease suggesting the clinical utility of monitoring levels of these anti-Mc antibodies in patients with chronic Chagas' disease.

Trypanosoma rangeli and Trypanosoma cruzi: molecular characterization of genes encoding putative calcium-binding proteins, highly conserved in trypanosomatids

Genes encoding a 29-kDa flagellar calcium-binding protein (F29) in Trypanosoma cruzi, strongly homologous to EF-hand calcium-binding protein-encoding genes previously reported in this parasite, were isolated by immunoscreening. F29 is encoded by a number of very similar genes, highly conserved among different T. cruzi isolates. The genes are located on a pair of homologous chromosomes, arranged in one or two clusters of tandem repeats. PCR amplification of Trypanosoma rangeli genomic DNA, using primers derived from the T. cruzi F29 sequence made it possible to isolate the homologous gene in T. rangeli, encoding a 23-kDa protein called TrCaBP. Gene sequence comparisons showed homology to EF-hand calcium-binding proteins from T. cruzi (82.8%), Trypanosoma brucei brucei (60.2%), and Entamoeba histolytica (28.4%). Northern blot analysis revealed that the TrCaBP gene is expressed in T. rangeli as a polyadenylated transcript. The TrCaBP-encoding genes are present in at least 20 copies per cell, organized in tandem arrays, on large T. rangeli chromosomes in some isolates and on two smaller ones in others. This gene, however, seems to be absent from Leishmania.

The flagellar fraction of Trypanosoma cruzi depleted of an immunosuppressive antigen enhances protection to infection and elicits spontaneous T cell responses

The flagellar fraction (FF) of Trypanosoma cruzi can be separated by immunoaffinity chromatography in two fractions with balanced but opposite immunological effects. The immunoaffinity purified fraction has immunosuppressive activity mediated at least partially by TGF-beta (Hansen et al., submitted). Here we report that the fraction depleted of immunosuppresive antigens (FT) administered with iscom-matrix as adjuvant provides enhanced protection to an infection challenge in immunized mice. In vitro, the FT but not the FF stimulated resident peritoneal cells to produce IL-1 and IL-6. In immunized mice, the FT elicited higher levels of antigen-specific IgG2a than the FF as well as broader recognition of T. cruzi antigens. Splenocytes from mice immunized with FT proliferated spontaneously in vitro and secreted TH1 and TH2 cytokines. The protection provided by FT correlates with its capacity to enhance the secretion of IFN-gamma. We postulate that immunosuppressive antigens present in the FF prevent the development of memory cells secreting IFN-gamma through a TGF-beta dependent mechanism.

Soluble cell adhesion molecules in human Chagas' disease: association with disease severity and stage of infection

Formation of inflammatory lesions, one of the pathologic consequences of infection with Trypanosoma cruzi, involves intricate cell-cell interactions in which cell adhesion molecules (CAMs) are involved. Sera from 56 Chagas' disease patients grouped according to disease severity were studied for the presence of soluble intercellular adhesion molecule-1 (s-ICAM-1), soluble endothelial selectin (s-E-selectin), soluble vascular cell adhesion molecule-1 (s-VCAM-1), soluble platelet selectin (s-P-selectin), and s-CD44 were studied to determine if they could be used alone or in different combinations as markers for specific diagnostic procedures. Comparisons were made between congenitally, acutely, and chronically infected patients and aged-matched, noninfected individuals, as well as between patients with chronic Chagas' disease grouped according to the severity of their heart-related pathology. No differences in levels of s-CAMs were detected between sera from children with congenital T. cruzi infection and sera from noninfected infants born from chagasic mothers. In contrast, titers of s-ICAM-1, s-VCAM-1, s-selectin, and s-CD44 but not s-P-selectin were significantly increased in sera from patients during the acute phase of infection with T. cruzi. Titers of s-VCAM-1 and s-P-selectin were increased in chronically infected patients. A positive association with disease severity in sera from patients with chronic disease was observed for the levels of s-P-selectin. In contrast, we found no association between clinical symptoms and levels of s-VCAM-1. Patients with chronic disease with severe cardiopathy also showed diminished levels of s-CD44 in comparison with healthy controls or patients with mild disease. The results are discussed in the context of pathology of Chagas' disease.

Probability of infection with Trypanosoma cruzi of the vector Triatoma infestans fed on infected humans and dogs in northwest Argentina

The probability that an uninfected Triatoma infestans would become infected with Trypanosoma cruzi after a single feed on people or dogs seropositive for T. cruzi was estimated in Amama, a rural village in northwest Argentina where transmission had resurged four years earlier. The prevalence of seropositivity for T. cruzi was 34.2% among 225 people tested, and 65.1% among 83 dogs tested. Parasitemia was detected by xenodiagnosis in 29.3% of 41 seropositive persons and in 85.3% of 34 seropositive dogs. Parasitemia decreased with age more sharply in seropositive people than in seropositive dogs. Seropositive humans infected 2.6% (95% confidence interval = 1.6%-3.6%) of 963 third or fourth instar nymphs fed once on them, whereas dogs infected 48.7% (44.7%-52.7%) of 610 nymphs. The probability of bug infection increased significantly with instar and was positively related to molting success. The infectivity to bugs of seropositive dogs was 12 times higher than that of seropositive children, and 100 times higher than that of seropositive adults. The weighted probability of infection of an uninfected bug fed randomly on any dog (0.3082) was about 50 times higher than that of bugs fed on any human (0.0062). Such differences in relative infectivity, combined with the relative host-feeding preference of domiciliary Triatoma infestans for dogs, reinforces the important role of domestic dogs as a risk factor for the domestic transmission of T. cruzi.

Hantavirus pulmonary syndrome in Argentina. Possibility of person to person transmission

In March 1995 the first case of a familiar outbreak of Hantavirus pulmonary syndrome (HPS) was notified in El Bolson, in the South of Argentina. Until December 15, 1996, a total of 77 cases of HPS had been notified with 48% mortality, distributed in three geographical areas of the country, South, North and Center. During 1996, of the 19 cases from El Bolsón, three were local physicians, one of whom -during the prodrome of her illness- travelled to Buenos Aires to be attended. In the hospital, two of the physicians who assisted her, developed HPS 27 and 28 days after the first contact. These data suggest for the first time the possibility of interhuman transmission of the Hantavirus responsible for the pulmonary syndrome.

Chronic experimental infection by Trypanosoma cruzi in Cebus apella monkeys

Twenty young male Cebus apella monkeys were infected with CA1 Trypanosoma cruzi strain and reinfected with CA1 or Tulahuen T. cruzi strains, with different doses and parasite source. Subpatent parasitemia was usually demonstrated in acute and chronic phases. Patent parasitemia was evident in one monkey in the acute phase and in four of them in the chronic phase after re-inoculations with high doses of CA1 strain. Serological conversion was observed in all monkeys; titers were low, regardless of the methods used to investigate anti-T. cruzi specific antibodies. Higher titers were induced only when re-inoculations were performed with the virulent Tulahuén strain or high doses of CA1 strain. Clinical, electrocardiographic and ajmaline test evaluations did not reveal changes between infected and control monkeys. Histopathologically, cardiac lesions were always characterized by focal or multifocal mononuclear infiltrates and/or isolated fibrosis, as seen during the acute and chronic phases; neither amastigote nests nor active inflammation and fibrogenic processes characteristic of human acute and chronic myocarditis respectively, were observed. These morphological aspects more closely resemble those found in the "indeterminate phase" and contrast with the more diffuse and progressive pattern of the human chagasic chronic myocarditis. All monkeys survived and no mortality was observed.

Standardization of serological tests for detecting anti-Trypanosoma cruzi antibodies in dogs

This paper reports on the standardization of four serological reactions currently used in human serodiagnosis for the detection of anti-Trypanosoma cruzi antibodies in naturally and experimentally infected dogs. Indirect immunofluorescence test (IFAT) and hemagglutination test (IHAT) were standardized, and complement fixation test (CFT) and direct agglutination test (DAT) were used for diagnostic confirmation. Four hundred and eighty one mongrel dogs that were studied by xenodiagnosis were used: (1) parasitemic dogs of two localities of endemic area (EA) of Santiago del Estero province in Argentina (n = 134); (2) non-parasitemic dogs of the same area (n = 285); (3) dogs experimentally infected with T. cruzi in the patent period (n = 6); (4) non-infected dogs (n = 56) which were born in the city of Buenos Aires (BA), one non-EA for Chagas' disease. For IFAT, parasitemic dogs EA showed 95% of reactive sera. Non parasitemic dogs EA showed 77% of non reactive sera. None sera from BA were reactive for dilutions higher than four. For IHAT, 84% of sera of parasitemic dogs EA showed serological reactivity and among non parasitemic dogs BA, 61% were non reactive, while the remainder showed at most titres of 1/16. The cut-off titres for IFAT and IHAT were 1/16 and 1/32 respectively, and for CFT and DAT 1/1 and 1/128 respectively. Sensitivity for IFAT, IHAT, CF and DAT were 95%, 84%, 97% and 95% respectively.

Isolation and characterization of a gene from Trypanosoma cruzi encoding a 46-kilodalton protein with homology to human and rat tyrosine aminotransferase

The complete sequence of a gene encoding a 46-kDa protein of Trypanosoma cruzi is presented. The first ATG complies with the consensus sequence for initiation of translation. A single band of 2 kb was highlighted by hybridizing a probe from the 46-kDa protein gene to a Northern filter containing total T. cruzi RNA. The gene is present in 50-80 copies per cell and most of them are contained in 2 tandem arrays on large T. cruzi chromosomes (> 2000 kb). A strong homology with rat and human tyrosine aminotransferase was detected. Homology with a Trypanosoma brucei retrotransposon was found in the nonsense strand of the intergenic region.

Result of a first step toward community-based surveillance of transmission of Chagas' disease with appropriate technology in rural areas

The objective of this work was to develop an effective methodology for the surveillance of Chagas' disease vectors in rural areas. It was based on the use of sensor boxes and portable mini-pumps to be integrated into the regular health promotion activities of the Primary Health Care (PHC) agents. The proposed methodology involves a continuous passive intradomiciliary detection of triatomines by sensor boxes that are monitored quarterly by PHC agents. Insecticidal treatment of the houses was performed immediately after the detection of triatomines. The more conventional method of vertical surveillance involves a direct entomologic evaluation conducted by trained professionals. The entire house is searched and there is a mandated treatment of the positive houses. The results of the followups obtained in the county of Rio Hondo in Santiago del Estero Province during a 36-month evaluation period immediately following attack phase application of insecticides were analyzed. The initial high domiciliary and peridomiciliary infestations decreased abruptly after the insecticidal treatment in both areas. When the performances of both types of surveillance were compared, the PHC agent method showed a lower percentage of houses reinfested, with fewer triatomines in the former, and a decrease in their rate of Trypanosoma cruzi infection. Evaluations of reinfestations using the man/hour method and the senor box method showed the same sensitivity. A higher sensitivity for detection of low densities of vector populations was achieved using the sensor boxes. The cost of PHC agent/sensor boxes surveillance was five times lower than the classic one. The proposed strategy for the continuous surveillance of Chagas' disease vectors has demonstrated effectiveness, allows community participation, and seems suitable for large scale application.

Chagas disease in north-west Argentina: infected dogs as a risk factor for the domestic transmission of Trypanosoma cruzi

The association between household seroreactivity to Trypanosoma cruzi in dogs and children and T. cruzi infection rates in domestic Triatoma infestans was investigated in 1988-1989 in the rural community of Amamá, north-west Argentina, where house spraying with residual pyrethroids was carried out in 1985. Three years after spraying, a greater reduction of the average T. cruzi prevalence rate in dogs (from 83% to 40%) than in children (from 48% to 30%) was accompanied by a substantial decrease in vector infection rates from 51%-63% to 21%. At a household level, in homes with or without seroreactive children, the percentage of infected T. infestans was 4.5-4.7 times higher when seroreactive dogs were present (27.1%-34.8%) than when they were not (5.8%-7.7%; stratified relative risk [RR] = 4.58). The contribution of seroreactive children to bug infection rates was not significant (RR = 1.29). The combined effect of both seroreactive dogs and seroreactive children fitted equally well with additive or multiplicative transmission models. Bug infection rates showed an increasing trend with the number of seroreactive dogs and an inverse association with the age of the youngest seroreactive dog. Our study supports the hypothesis of a causal association between the presence and number of infected dogs and increased levels of T. cruzi transmission to domestic T. infestans.

The status of transmission of Trypanosoma cruzi in an endemic area of Argentina prior to control attempts, 1985

A field survey of transmission of Trypanosoma cruzi was carried out in an area which had never been sprayed with insecticide. A population census, mapping and house classification, examination of insects in houses, and a human serological survey were performed. The entomological examination showed that 97% of the houses (433/445) were infested by Triatoma infestans and that 31% of the bugs examined were infected with T. cruzi. The level of infection, as well as the number of insects captured, had no apparent relationship with the type of house. Trypanosoma cruzi was found in 30% of the human population, and in 10% of children up to four years old. The rates of infection were significantly lower for inhabitants, especially children, living in 'urban' houses. The prevalence rate for the children did not correlate with the number of insects collected in the houses. The improvement of houses, outside the framework of an integrated control programme, had no obvious impact on the level of transmission. Nevertheless, the replacement of the original houses by houses with plastered walls and roofs of metal or cement resulted in a decrease in the prevalence of infection in children younger than four years of age. The community showed little confidence in sanitary precautions against Chagas' disease prior to the start of the survey.

Trypanosoma cruzi: T-cell-dependent mechanisms of resistance during chronic infection

Effector mechanisms of resistance exerted by T cells from BALB/c mice chronically infected with Trypanosoma cruzi, Tulahuén strain, were studied. Spleen cells from chronically infected mice (Chro-SC) prestimulated with heat-killed trypomastigotes (HKT) and/or IL-2 destroyed PHA-labeled p-815 mastocytoma cells, HKT-pulsed macrophages, and normal peritoneal macrophages. However, HKT-stimulated Chro-SC did not affect the infectivity of free bloodstream forms of the parasite. Upon HKT stimulation, Chro-SC or their culture supernatant activated peritoneal macrophages for the destruction of intracellular amastigotes. The effect was abolished after Thy 1.2+ cell depletion. The addition of Cyclosporin A (CyA), which blocks T-cell activation, during HKT-stimulation of Chro-SC, diminished their ability to activate the trypanocidal activity of macrophages. CyA also inhibited the production of both macrophage-activating factors and interferon-gamma by HKT-stimulated Chro-SC. CyA administration to recipients of nylon-wool nonadherent spleen cells from chronically infected mice inhibited their adoptively acquired resistance against T. cruzi, suggesting that the conferred resistance depended on the effect of specifically activated cells. When administered during the chronic stage of the infection, CyA abrogated the antigen-specific delayed type hypersensitivity response but increased the levels of anti-T. cruzi IgG antibodies. Neither parasitemia, tissular parasitism in myocardium or skeletal muscle, nor mortality were detected after CyA treatment, suggesting the presence of a CyA nonsensitive mechanism(s) in the control of T. cruzi during the chronic phase of the infection.