[Efficacy of Fipronil in the control of the peridomiciliary cycle of Triatoma infestans in an area resistant to Deltamethrin]

This study tested the efficacy of liquid Fipronil (1.0%) against Triatoma infestans, administered by pouring on birds and mammals both in laboratory and field conditions. In the laboratory a chicken, dog, and goat were treated with Fipronil, after which deltamethrin-resistant stage III T. infestans nymphs were fed on them. The control group used same-stage nymphs reared in laboratory. During the field phase, Fipronil was used to treat 4 dogs, 1 cat, and 2 broody hens. Intradomiciliary infestation was treated using aerothermics. In laboratory, nymphal mortality was 100.0% after 7 days and 88.8% after 30 days. In the field, there was a 65.4% decrease in the triatomine density rate after 30 days.

[Occurrence of Panstrongylus lutzi, in peridomiciliary areas, State of Ceará, Brazil]

From January 2001 to October 2002 captures were made in domicile and peridomiciliary areas of 13 cities of region of Cariri, south of the State of Ceará. As results, the occurrence of P. lutzi in this area was noticed, for the first time, in three cities: the presence of one adult in chicken house in Altaneira, one adult flying, in Salitre and 18 nymphs in Varzea Alegre(13 in bricks pile and five in roofing tile pile). In Varzea Alegre city it was observed the colonization in the peridomicile.

Trypanocidal activity of chemical constituents from Lychnophora salicifolia Mart

The ethyl acetate extract from leaves plus inflorescences of L. salicifolia showed significant trypanocidal activity against trypomastigote forms of T. cruzi, which was due to the flavonoid quercetin-7,3',4'-trimethyl ether and the sesquiterpenoid lychnopholic acid. Despite the use of some species of Lychnophora in folk medicine for pain relief, crude extracts from L. salicifolia Mart. showed no antinociceptive activity in the mouse writhing test.

[Air temperature elevation as an alternative for the control of deltamethrin-resistant Triatoma infestans (Hemiptera, Reduviidae)]

This study explores the effects of artificial air temperature elevation on the embryonic, nymphal, and adult forms of deltamethrin-resistant Triatoma infestans. In the laboratory, complete offspring of T. infestans were exposed to increasing air temperatures to determine the viability of eggs and survival of nymphs and adults; in the field, the experiment was conducted in a poor rural dwelling previously identified as infested with the vector. The laboratory phase showed 100% non-viability of eggs and 100% mortality of nymphs and adults exposed to airtight temperatures from 45 degrees C to 55 degrees C, while the field phase succeeded in reproducing the heat's ovicidal effect and negative conversion of entomological assays in the experimental dwelling, as conducted over the course of 72 hours at 30, 60, and 90 days from the baseline evaluation. Artificial elevation of airtight temperature on dwellings proved to be an acceptable, harmless, and technically simple control method.

Re-infestation of houses by Triatoma dimidiata after intra-domicile insecticide application in the Yucatán peninsula, Mexico

In most countries, Chagas disease transmission control remains based on domestic insecticide application. We thus evaluated the efficacy of intra-domicile cyfluthrin spraying for the control of Triatoma dimidiata, the only Chagas disease vector in the Yucatán peninsula, Mexico, and monitored potential re-infestation every 15 days for up to 9 months. We found that there was a re-infestation of houses by adult bugs starting 4 months after insecticide application, possibly from sylvatic/peridomicile areas. This points out the need to take into account the potential dispersal of sylvatic/peridomestic adult bugs into the domiciles as well as continuity action for an effective vector control.

Acute Trypanosoma cruzi infection: IL-12, IL-18, TNF, sTNFR and NO in T. rangeli-vaccinated mice

We have developed an experimental model of vaccination against the infection with the protozoa Trypanosoma cruzi, the agent of Chagas disease in Latin America. Vaccination was performed with Trypanosoma rangeli, a non-pathogenic protozoa sharing many antigens with T. cruzi. It strongly protected BALB/c mice, sharply reducing parasitaemia and mortality rate of the acute T. cruzi infection. The aim of the present work was to complete our previous study on the production of IFN-gamma and IL-10 in this vaccination model by investigating the production of IL-12p35 and p40, IL-18, TNF, TNF soluble receptors (sTNFR), and nitric oxide (NO), factors known to play a key role in the outcome of T. cruzi infection. We show that the protection obtained against the acute T. cruzi infection was surprisingly associated with reduced circulating levels of IL-18 and NO, whereas the release of IL-12p40 was enhanced in comparison to non-vaccinated infected animals. IL-12p35 remained undetectable in infected animals, vaccinated or not. The balance between sTNFR and TNF suggested a decrease of TNF bioactivity in vaccinated mice. These results show that the protection induced by the vaccination with T. rangeli against a challenging infection with T. cruzi is not associated with the strong type 1 immune response usually involved in the control of intracellular pathogens, particularly questioning the protective role of NO during the acute phase of T. cruzi infection.

Protective role of ETA endothelin receptors during the acute phase of Trypanosoma cruzi infection in rats

Chagas' disease, caused by Trypanosoma cruzi, has an acute phase characterized by blood-circulating trypomastigotes and amastigote proliferation in several cell types, especially muscle cells. In the chronic phase, around 70% of infected people are asymptomatic (latent form). The remainder develop chagasic cardiomyopathy and/or digestive syndromes. There is evidence for aggravation of the chronic cardiac pathology by endothelin-mediated vasoconstriction. Holtzman rats have proven to be a good model for Chagas' disease acute phase and latent chronic phase. Now, we investigate the effects of prolonged treatment with an endothelin ET(A) receptor antagonist, BSF 461314, during the acute phase on parasitemia, coronary flow, tissue parasitism and the inflammatory process. Using isolated heart in Langendorff's preparation, endothelial dysfunction was observed only in non-treated infected animals. Histoquantitative analyses carried out in heart and diaphragm showed higher tissue parasitism and/or inflammatory process in BSF 461314-treated animals. Our data indicate that endothelin ET(A) receptors contribute to the initial mechanisms of parasite control. Impairment of the endothelium-dependent vasodilatation favors hazardous effects. However, blocking endothelin ET(A) receptors can prevent the latter.

Trypanocidal properties of Mikania stipulacea and Mikania hoehnei isolated terpenoids

The in vitro trypanocidal properties of isolated terpenoids from Mikania stipulacea and Mikania hoehnei were investigated in Trypanosoma cruzi Y strain. Both compounds, the diterpene ent-9alpha-hydroxy-15beta-E-cinnamoyloxy-16-kauren-19-oic acid (1) and the sesquiterpene lactone 8beta-hydroxyzaluzanin D (2) were active.

Chagas seropositive donors in kidney transplantation

Among 239 kidney transplantations between September 1992 and September 1997, nine recipients' kidneys were obtained from Chagas seropositive donors. All of these patients were treated with benznidazole (5 mg/kg/d) for 14 days starting on day 0. None of them experienced acute Chagas disease or seroconversion even after 10 years follow-up. We concluded that, due to cadaver shortage, donors with positive serology for Chagas disease should not be excluded.

Use of a purified Trypanosoma cruzi antigen and CpG oligodeoxynucleotides for immunoprotection against a lethal challenge with trypomastigotes

The crucial role played by Ag163B6/cruzipain, the major cystein proteinase of Trypanosoma cruzi, in the process of parasite internalization into mammalian cells and IgG hydrolysis, signals this antigen as a potential target for raising a protective immune response against Chagas' disease. On the other hand, synthetic oligodeoxynucleotides containing CpG-motifs (CpG-ODN) are capable of driving immunity toward a Th1 bias. Considering the importance of Th1 mechanisms in resistance against this intracellular parasite, we analyzed the ability of Ag163B6/cruzipain plus CpG-ODN to induce immunoprotection against a lethal challenge with trypomastigotes. Mice were immunized with Ag163B6+CpG-ODN showing high specific antibody titers, mostly IgG2a. Spleen cells from these mice strongly proliferated and presented significant increase of IL-2 and IFN-gamma concentrations in their supernatant upon antigen stimulation. Trypomastigote challenge rendered elevated parasitemia and mortality in all control groups, meanwhile Ag163B6+CpG-ODN mice displayed the lowest level of blood parasites and 100% survival to acute infection. Besides, we demonstrated that other parasite antigens introduced into mice when challenged, and consequently never seen before by the immune system, also elicited a Th1 immune response. Taken together, these results plus others provide the basis for the design of a multicomponent anti-T. cruzi vaccine which may ultimately be used not only to protect humans at risk of infection, but also may alleviate or prevent the pathogenic responses characteristic of chronic Chagas' disease by reducing or perhaps eliminating tissue parasites from infected patients.

CTLA-4 Blockage Increases Resistance to Infection with the Intracellular ProtozoanTrypanosoma cruzi

Recent studies have revealed an important role for CTLA-4 as a negative regulator of T cell activation. In the present study, we evaluated the importance of CTLA-4 to the immune response against the intracellular protozoan, Trypanosoma cruzi, the causative agent of Chagas' disease. We observed that the expression of CTLA-4 in spleen cells from naive mice cultured in the presence of live trypomastigote forms of T. cruzi increases over time of exposure. Furthermore, spleen cells harvested from recently infected mice showed a significant increase in the expression of CTLA-4 when compared with spleen cells from noninfected mice. Blockage of CTLA-4 in vitro and/or in vivo did not restore the lymphoproliferative response decreased during the acute phase of infection, but it resulted in a significant increase of NO production in vivo and in vitro. Moreover, the production of IFN-gamma in response to parasite Ags was significantly increased in spleen cells from anti-CTLA-4-treated infected mice when compared with the production found in cells from IgG-treated infected mice. CTLA-4 blockade in vivo also resulted in increased resistance to infection with the Y and Colombian strains of T. cruzi. Taken together these results indicate that CTLA-4 engagement is implicated in the modulation of the immune response against T. cruzi by acting in the mechanisms that control IFN-gamma and NO production during the acute phase of the infection.

Pesquisa sistemática positiva e relação com conhecimento da população de assentamento e reassentamento de ocupação recente em área de Triatoma sordida (Hemiptera, Reduviidae) no Estado de São Paulo, Brasil

Procurou-se analisar a relação existente entre Unidade Domiciliar (UD) com triatomíneo e os conhecimentos sobre doença de Chagas entre os moradores destas UD's formadas recentemente em conglomerados denominados assentamento e reassentamento. Foram selecionadas duas localidades situadas nos municípios de Euclides da Cunha Paulista (assentamento) e Paulicéia (reassentamento) pertencentes à Região Administrativa de Saúde de Presidente Prudente, São Paulo, Brasil. A entrevista com os moradores das UD's abrangeu 319 indivíduos. Em relação aos conhecimentos a respeito do inseto, 100 pessoas conheciam o mesmo, sendo 76,0% moradora do reassentamento. Quando analisados os resultados da entrevista para os domicílios com pesquisa triatomínica positiva verificou-se que 93 pessoas (47,4%) estavam nestas moradias. Em 79,2% das casas em que se coletou triatomíneo (Triatoma sordida) há 26,8% dos indivíduos que apresentam conhecimento sobre doença/vetor, mas em 50,0% destas casas há pessoas que não sabem o que fazer caso encontrem este inseto no seu domicílio. Neste estudo não foi encontrada relação entre o sexo, a idade, a naturalidade e a adoção de práticas preventivas adequadas e o conhecimento sobre a doença/vetor na população entrevistada tanto no assentamento como no reassentamento.

Cutting edge: a potent adjuvant effect of ligand to receptor activator of NF-kappa B gene for inducing antigen-specific CD8+ T cell response by DNA and viral vector vaccination

The ligand to receptor activator of NF-kappaB (RANK-L)/RANK interaction has been implicated in CD40 ligand/CD40-independent T cell priming by dendritic cells. In this report, we show that the coadministration of the RANK-L gene with a Trypanosoma cruzi gene markedly enhances the induction of Trypanosoma Ag-specific CD8(+) T cells and improves the DNA vaccine efficacy. A similarly potent adjuvant effect of the RANK-L gene on the induction of Ag-specific CD8(+) T cells was also observed when recombinant influenza virus expressing murine malaria Ag was used as an immunogen. In contrast, the coadministration of the CD40L gene was not effective in these systems. Our results demonstrated, for the first time, the potent immunostimulatory effect of the RANK-L gene to improve the CD8(+) T cell-mediated immunity against infectious agents.

Selective in vitro effects of the farnesyl pyrophosphate synthase inhibitor risedronate on Trypanosoma cruzi

We present the results of the first detailed study of the molecular and cellular basis of the antiproliferative effects of the bisphosphonate risedronate (Ris) on Trypanosoma cruzi, the causative agent of Chagas' disease. Ris and related compounds, which block poly-isoprenoid biosynthesis at the level of farnesyl pyrophosphate synthase, are currently used for the treatment of bone resorption disorders, but also display selective activity against trypanosomatid and apicomplexan parasites. Ris induced a dose-dependent effect on growth of the extracellular epimastigote form of T. cruzi; complete growth arrest and cell lysis ensued at 150 microM. Growth inhibition was associated with depletion of the parasite's endogenous sterols, but complete growth arrest and loss of cell viability took place before full depletion of these compounds, suggesting that disappearance of other essential poly-isoprenoids is involved in its anti-parasitic action. Ris had a variety of effects on cellular ultrastructure, including mitochondrial swelling, disorganisation of other organelles, such as reservosomes and the kinetoplast, together with the appearance of autophagic vesicles and progressive vacuolization of the cytoplasm. Ris had selective antiproliferative effects against the clinically relevant amastigote form of T. cruzi, and at 100 microM, was able to prevent completely the development of T. cruzi infection of murine muscle heart or Vero cells, and to cure cultures which were already infected. Ris induced drastic ultrastructural alterations in the intracellular parasites and blocked amastigote to trypomastigote differentiation, with no biochemical or ultrastructural effects on the host cells, which fully recovered their normal structure and activity after treatment. Ris is, therefore, a promising lead compound for the development of new drugs against T. cruzi.

Phytomonas serpens, a tomato parasite, shares antigens withTrypanosoma cruzithat are recognized by human sera and induce protective immunity in mice

The immune cross-reactivity between Trypanosoma cruzi, the protozoan that causes Chagas' disease, and Phytomonas serpens, a trypanosomatid that infects tomatoes, was studied. Sera from patients with Chagas' disease presented a strong reactivity with P. serpens antigens by conventional serological assays such as indirect immunofluorescence (IIF) and direct agglutination test (DAT), confirmed after cross-absorption experiments. The results show that this protozoan is highly immunogenic and that rabbit and mouse hyperimmune serum raised against T. cruzi or P. serpens was able to recognize both T. cruzi and P. serpens antigens in immunofluorescence and agglutination assays. The antigenic cross-reactivity between T. cruzi and P. serpens was also demonstrated in vivo. BALB/c mice immunized by the intraperitoneal or oral route with P. serpens and later challenged with a lethal inoculum of T. cruzi blood forms showed a significant decrease in parasitemia and increase in survival compared to controls. A practical implication of these findings is that the ingestion by humans or animals of living plant trypanosomatids present in naturally infected edible fruits could potentially prime the immune response to T. cruzi antigens and interfere with the development of T. cruzi infection.

Efficacy of pyrethroid insecticides against domestic and peridomestic populations of Triatoma pallidipennis and Triatoma barberi (Reduviidae:Triatominae) vectors of Chagas' disease in Mexico

A single village control trial for Triatoma pallidipennis and T. barberi was conducted using three synthetic pyrethroids (bifenthrin, cyfluthrin, and deltamethrin), evaluated as residual treatments in separate sectors, with complete coverage indoors and in peridomiciliary areas. Spray intervention was preceded by a preintervention entomological evaluation and household survey, followed by four postintervention evaluations at 1, 3, 6, and 12 mo of > 96% of houses. Overall preintervention adjusted infestation index was 38%, 17% of which represented intradomicile infestation. Dose verification using high-performance liquid chromatography (HPLC) demonstrated correct spray doses for all but deltamethrin treatments. There was between a 6- and 13-fold decrease in intradomicile live bug infestation for cyfluthrin- and bifenthrin-treated areas, resulting at 1 mo in 0 and 0.6% infestation, respectively. Intradomicile infestation recovered somewhat, terminating at 20 and 50% of preintervention levels at 12 mo, respectively, while peridomicile infestation recovered preintervention levels within 3-6 mo. Households with persistent live peridomiciliary infestation had 1.9 times the risk of having a persistent intradomiciliary infestation, while 80% of peridomicile infestations for both triatomine species were in houses not having a previous infestation. New or reinfestation of households did not occur consistent with a sylvan source, and unconstructed lots were not a significant source of bugs. Houses with persistent peridomicile infestation did represent a significant risk for surrounding uninfested houses by cluster analysis (P < 0.05). Along with the increased prevalence of T. cruzi infection after intervention, the data indicate that a sylvan reservoir source, probably peridomicile small rodent nests, represent the major risk factor for persistent and new infestations.

Pyrethroid-impregnated curtains for Chagas' disease control in Venezuela

The use of insecticide treated materials for the control of Chagas' disease transmission is potentially a cost-effective and sustainable option where vectors are sylvatic. A study was undertaken in two rural Chagas' disease endemic communities (96 households) of Trujillo State, Venezuela. After a baseline study (including a short questionnaire survey, assessment of housing conditions, vector behaviour and preferences in vector protection), 37 households were chosen at random for protection by impregnated or non-impregnated curtains. During the 30-day entomological study vector collection of triatomine bugs were conducted in the early morning. The protective efficacy of curtains was determined by the number of vectors found dead or alive in control and experimental houses. It was found that house infestation of Chagas' disease vectors was high (60% of houses) in spite of good-quality houses due to a re-housing programme. The vectors were sylvatic (mainly Rhodnius robustus) and entered the houses at night. More than half the population (52%) preferred curtains to bednets for Chagas' disease protection. Users of pyrethroid-impregnated curtains were well protected as no living triatomines were found in bedrooms of houses with impregnated curtains compared to houses with non-impregnated curtains where an average of 4/7 vectors were found alive in bedrooms. In houses with impregnated curtains 21/30 triatomines died within 72 h; the triatomines which survived were found exclusively in rooms where no impregnated curtains had been placed. In houses with non-impregnated curtains 20% (6/30) of vectors died, probably due to rough handling. It is concluded that pyrethroid-impregnated curtains represent an important option for the reduction or even elimination of man-vector contact and thus of Chagas' disease transmission in areas where species of small triatomine bugs such as Rhodnius prolixus and R. robustus are the main vectors.

[Chagas Disease Control Program in the State of São Paulo: persistence of high triatomine infestation rates in some localities during the 1990s]

The purpose of our investigation was to analyze the persistence, in the State of São Paulo, of domiciliary units highly infested with Chagas disease triatomine vectors. Comprehensive epidemiologic information collected from 1990 to 1999 in the State of S o Paulo was retrieved from database files. Consistently high infestation rates were found in 43 localities distributed among 21 municipalities in the Ara atuba region. Captures produced predominantly peridomiciliary Triatoma sordida specimens, mostly adult females and fifth-instar nymphs, 94.6% of which containing ingesta negative for human blood. The houses, mostly inhabited (87.4%), were located near the residual woodland savanna in 64.3% of the localities. Poultry coops were found in association with 97.6% of all domiciliary units. Interestingly, in all the houses with persistent infestation, the inhabitants paid no evident attention to hygiene Lack of timely infestation control associated with the biological characteristics of the reduviid species involved, along with the conditions prevailing around the dwellings, favor the repeated invasion and consequent maintenance of colonization by triatomines.