Un brote de dermatitis producido por picaduras de Sclerodermus sp. (Hymenoptera, Bethylidae) en Costa Rica, América Central / An outbreak of dermatitis produced by the stings of Sclerodermus sp. (Hymenoptera, Bethylidae) in Costa Rica. Central America

Resumen:Se describe un brote de dermatitis producido por la picadura de una pequeña avispa áptera Sclerodermus sp. (Hymenoptera, Bethylidae), en un grupo de estudiantes de un colegio de San José, capital de Costa Rica. Se encontró también al escarabajo xilófago Calymmaderus pupatus (Coleoptera, Ptinidae), que sirve de huésped a la avispita, la cual necesita depositar sus huevos, como parasitoide, en las larvas del coleóptero para su reproducción. Casos autóctonos de esta dermatitis se conocen en los cinco continentes y esto contrasta con la ausencia de reportes procedentes de América Central.Los lugares en donde se observaron las lesiones, a veces numerosas en la misma persona, fueron: brazos, cuello, piernas, espalda, abdomen, pecho, cara y codos. El tipo de lesión se caracteriza por dolor y ardor en el momento de la picadura, seguido de una pápula eritematosa de tamaño variable, hasta un centímetro de diámetro e intenso prurito, con una duración de una a dos semanas. Se observaron cuadros urticariformes y angioedematosos e inclusive infecciones secundarias como consecuencia del rascado.El problema se atacó con una fumigación dirigida al coleóptero, con un insecticida capaz de penetrar la madera llena de galerías del escarabajo y sus larvas. Pocos días después de la fumigación, se encontraron numerosos ptínidos adultos muertos, así como gran cantidad de betílidos, en los muebles dañados por el escarabajo.

Abstract:This article describes an outbreak of dermatitis caused by stings from a small apterous wasp, Sclerodermus sp. (Hymenoptera: Bethylidae), among a group of students attending a school in San José, of Costa Rica. Also present was the xylophagous beetle, Calymmaderus pupatus (Coleoptera: Ptinidae), which serves as a host for this parasitic wasp and on which the wasp depends for its reproduction. The female wasps lay their eggs on the beetle larvae in the wood and the wasp larvae develop as parasitoids. Autochthonous cases of dermatitis caused by bethylid wasps are known from all other five continents but, as far as we are aware, this is the first report from Latin America, and the first report of Sclerodermus from Central America.The sites in which the lesions were located, sometimes numerous in the same person, were: arms, neck, legs, back, abdomen, breast, face and elbows. The type of lesionwas characterized by being painful, with a burning sensation, at the moment of the sting, followed by an erythematous papule lesion of variable size, up to one centimeter in diameter and with intense pruritus, lasting from one to two weeks. Urticariform lesions and angioedema were observed, as well as secondary infections consequence of the scratching of the lesions.The problem was solved by a fumigation directed against the coleoptera beetle, with an insecticide capable of penetrating the wood that was filled with tunnels made by the adult beetles and larvae. A few days after the fumigation numerous dead beetles and bethylid wasps were found in the furniture damaged by the beetles.

Influencia del sexo en la susceptibilidad de ratones Swiss a Trypanosoma cruzi / Sex influence on the susceptibility of Swiss mice to Trypanosoma cruzi

Algunos estudios han reportado que los ratones hembras son más resistentes al trypanosoma cruzi que los machos. Para probar lo anterior, se realizo un estudio comparativo con cuatro cepas de T. cruzi de Costa Rica midiendo parámetros como niveles de parasitemia, porcentajes de mortalidad e histopatología, en un total de 240 ratones (160 para parasitemia y mortalidad y 80 para histopatología). Todas las cepas correspondieron al genotipo TcI. En todos los casos los ratones machos resultaron más susceptibles a la infección (P<0,001). Se observaron parasitemias hasta cinco veces más altas en los machos que, en general, mueren antes que las hembras. La cepa Oswaldo fue la que presentó una mayor mortalidad y niveles de parasitemia más altos. El tejido cardiaco fue el más afectado tanto en los ratones machos como en las hembras, con las cepas bolita y capitán el número de nidos en el miocardio fue significativamente mayor en los machos que en las hembras. Una vez concluido el análisis comparativo se eligió la cepa humana GA, para determinar su efecto en ratones machos y hembras castrados, al lado de ratones normales (150 ratones en total). Las hembras normales se mostraron como las más resistentes, con parasitemias menores que las castradas (P<0,001), y los machos normales como los más susceptibles, con parasitemias significativamente más altas (P<0,001) y supervivencias menores (P<0.01), que los ratones castrados. No se observó diferencia significativa en cuanto al número de nidos en los tejidos entre ratones normales y castrados. Se concluye que el sexo tiene influencia en la resistencia a la infección experimental por T. cruzi.

Some authors have reported that female mice are more resistant to Trypanosoma cruzi infections than male mice. In order to test this hypothesis we did a comparative study using four isolates of T. cruzi from Costa Rica in a total of 160 mice, and observed several parameters such as: parasitemia levels, percent mortality and histopathology. All isolates were identified as genotype TcI. Male mice were more susceptible to infection (P<0.001). Parasitemias reached levels up to five times higher in males and shorter survival periods were observed in males than in females. The Oswaldo isolate showed the highest parasitemias and mortality rates. The heart tissue was the most affected in both males and females. In two isolates the number of parasites in the heart was significantly higher in males than in females. In separate experiments, the human GA isolate was selected in order to observe its effect in castrated male and female mice. Non-castrated females were the most resistant, with lower parasitemias than castrated females, and non-castrated males were the most susceptible with higher parasitemias (P<0.001) and lower survival periods than castrated males (P<0.01). There was no significant difference in the number of parasites in tissues between normal and castrated mice. The final conclusion is that there is a marked sex influence in the susceptibility of mice to T. cruzi experimental infections.

Molecular characterization of Trypanosoma cruzi and infection rate of the vector Triatoma dimidiata in Costa Rica.

According to the genetic characterization by the analysis of the miniexon gene, strains of Trypanosoma cruzi can be classified into six discrete typing units (DTUs), and the DTU 1 into four distinct genotypes associated with different life cycles. While Chagas disease is endemic in Costa Rica, T. cruzi isolates from this region have never been genetically characterized. An analysis of 16 isolates from Costa Rica, based on miniexon gene analysis, showed the existence of two different haplotypes in the country, closely related to the Colombian haplotype group TcIa and to sequences from several Mexican isolates, with eight variable positions in the alignment and a variability of 2.6% between the compared sequences. No relationship between the habitat, vector or host, and the haplotypes was found, suggesting an active flow of T. cruzi in the country. The present study also reports a very high infection rate (47.3%, 26 out of 55 specimens) in a Costa Rican population of Triatoma dimidiata, the main vector of Chagas disease in this country. The distribution and abundance of the parasite and its main vector suggest a high risk of Chagas disease emergence in Costa Rica.

Life cycle of Triatoma ryckmani (Hemiptera: Reduviidae) in the laboratory, feeding patterns in nature and experimental infection with Trypanosoma cruzi.

A cohort initiated with 121 eggs, yielding 105 first instar nymphs (eclosion rate: 86.78%), allowed us to observe the entire life cycle of Triatoma ryckmani under laboratory conditions (24 degrees C and 62% relative humidity), by feeding them on anesthetized hamsters. It was possible to obtain 62 adults and the cycle from egg to adult took a mean of 359.69 days with a range of 176-529 days (mortality rate of nymphs: 40.95%). Mean life span of adults was of 81 days for females and 148 days for males. The developmental periods of 4th and 5th nymphs were longer than those of the other instars. This suggests that young siblings have a better chance of taking a hemolymph meal from older ones, in order to survive during fasting periods during prolonged absences of vertebrate hosts from natural ecotopes. The stomach contents of 37 insects showed blood from rodents (15 cases), lizards (7 cases), birds (6 cases) and insect hemolymph (7 cases). Out of 10 insects fed by xenodiagnosis on a Trypanosoma cruzi infected mouse, all but one became infected with the parasite.

Molecular evidence of intraspecific variability in different habitat-related populations of Triatoma dimidiata (Hemiptera: Reduviidae) from Costa Rica.

Intraspecific genetic variation among Triatoma dimidiata (Hemiptera: Reduviidae) from seven Costa Rican populations and from different domestic, peridomestic, and sylvatic ecotopes were analyzed. The complete nucleotide sequence of the nuclear ribosomal DNA internal transcribed spacer (ITS-2) and partial sequences of the cytochrome B (Cyt b) gene and the large ribosomal subunit RNA (16S) of mitochondrial DNA (mtDNA) were analyzed and compared. All ITS-2 sequences analyzed were identical and correspond to the haplotype T.dim-H1, the most common haplotype in Central American populations. Sequences of mtDNA revealed a 10.17% of polymorphism in Cyt b and 2.39% in 16S, suggesting that the Cyt b fragment is a useful marker to describe the genetic structure of populations, even at habitat-related level. The analyses of the 18 new combined T. dimidiata haplotypes (Cytb/16S/ITS-2) showed that the two main geographical locations and populations studied are genetically structured showing different haplotype profiling. Only one combined haplotype was shared in the studied areas (Cytb.d/16S.a). Seven haplotypes exclusive for domestic/peridomestic populations, five for sylvatic, and six shared haplotypes for both habitat-related ecotopes are described. Although the relationship between the habitat and the haplotype profiling is less clear, there are different patterns of haplotype distribution in each geographic area between the two habitat-related ecotopes studied (domestic/peridomestic and sylvatic), some of them reflected in the phylogenetic relationships analyzed. The intraspecific variability detected may underlie the known plasticity of T. dimidiata, an important vector for Chagas disease transmission, suggesting that this species must be continuously monitored.

Life cycle of Triatoma ryckmani (Hemiptera: Reduviidae) in the laboratory, feeding patterns in nature and experimental infection with Trypanosoma cruzi

A cohort initiated with 121 eggs, yielding 105 first instar nymphs (eclosion rate: 86.78 percent), allowed us to observe the entire life cycle of Triatoma ryckmani under laboratory conditions (24ºC and 62 percent relative humidity), by feeding them on anesthetized hamsters. It was possible to obtain 62 adults and the cycle from egg to adult took a mean of 359.69 days with a range of 176-529 days (mortality rate of nymphs: 40.95 percent). Mean life span of adults was of 81 days for females and 148 days for males. The developmental periods of 4th and 5th nymphs were longer than those of the other instars. This suggests that young siblings have a better chance of taking a hemolymph meal from older ones, in order to survive during fasting periods during prolonged absences of vertebrate hosts from natural ecotopes. The stomach contents of 37 insects showed blood from rodents (15 cases), lizards (7 cases), birds (6 cases) and insect hemolymph (7 cases). Out of 10 insects fed by xenodiagnosis on a Trypanosoma cruzi infected mouse, all but one became infected with the parasite.

In vitro activity of thienyl-2-nitropropene compounds against Trypanosoma cruzi.

The in vitro activity of four 2-nitropropene derivatives, 1-(3-benzothienyl)-2-nitropropene (N1), 1-(3-thienyl)-2-nitropropene (N2), 1-(5-bromo-2-thienyl)-2-nitropropene (N3) and 1-(4-bromo-2-thienyl)-2-nitropropene (N4), were tested against cultures of the parasite Trypanosoma cruzi. Cytotoxicity studies were performed using Vero cells. The blood trypomastigotes, amastigotes and epimastigotes showed differential degrees of sensitivity towards the four tested compounds; the highest activity against the epimastigotes and blood tripomastigotes was exhibited by N1, followed by N3, N4 and finally N2. In contrast, whereas the compounds N1, N3 and N4 exerted similar magnitudes of activity against amastigotes, N2 was found to be a much less potent compound. According to our results, the compound N1 had the highest level of activity (IC50: 0.6 microM) against epimastigotes.

In vitro activity of thienyl-2-nitropropene compounds against Trypanosoma cruzi

The in vitro activity of four 2-nitropropene derivatives, 1-(3-benzothienyl)-2-nitropropene (N1), 1-(3-thienyl)-2-nitropropene (N2), 1-(5-bromo-2-thienyl)-2-nitropropene (N3) and 1-(4-bromo-2-thienyl)-2-nitropropene (N4), were tested against cultures of the parasite Trypanosoma cruzi. Cytotoxicity studies were performed using Vero cells. The blood trypomastigotes, amastigotes and epimastigotes showed differential degrees of sensitivity towards the four tested compounds; the highest activity against the epimastigotes and blood tripomastigotes was exhibited by N1, followed by N3, N4 and finally N2. In contrast, whereas the compounds N1, N3 and N4 exerted similar magnitudes of activity against amastigotes, N2 was found to be a much less potent compound. According to our results, the compound N1 had the highest level of activity (IC50: 0.6 ìM) against epimastigotes.

Trypanosoma rangeli genotypes association with Rhodnius prolixus and R. pallescens allopatric distribution in Central America.

Previous kDNA polymorphism-based reports have revealed the existence of two Trypanosoma rangeli genotypes (KP1+ and KP1-): SL and SSU rRNA gene polymorphism-based studies have revealed that five genotypes (A-E) are distributed throughout different Latin-American countries. Some evidence has shown that the genotypes' biogeographical distribution is associated with sympatric Rhodnius species. 12 T. rangeli isolates from humans and reservoirs from El Salvador, Guatemala, Honduras, Costa Rica and Panama were characterised by kDNA and mini-exon gene intergene spacer analysis and compared to 12 previously characterised isolates from humans and vectors from Colombia, Guatemala, Honduras and Venezuela. Central American isolates corresponded to genotypes called KP1(+) or lineage A and KP1(-) or lineage C. Such dimorphism was corroborated by randomly amplified polymorphic DNA (RAPD) in 22 selected isolates; a dendrogram was thus produced having two defined branches. One branch grouped KP1(-) or lineage C strains isolated from Rhodnius colombiensis (Colombia), humans (Panama), Procyon lotor and Choloepus hoffmanni (Costa Rica). The other group was formed by KP1(+) or lineage A strains isolated from Rhodnius prolixus (Colombia, Venezuela) and humans (El Salvador, Guatemala, Honduras). These results present evidence that both groups infect different mammals (humans, domestic and silvatic animals) having no association with any particular vertebrate species; however, T. rangeli KP1(+) or (A) strains have been isolated in Central America in areas where R. prolixus circulate (Honduras, El Salvador and Guatemala) and KP1(-) or (C) strains have been isolated in areas where Rhodnius pallescens is the main vector (Panama and Costa Rica) indicating a parasite-vector association. The same lineages circulate in Andean countries (Colombia, Venezuela, Ecuador and Peru), KP1+ being associated with members of the prolixus group (R. prolixus and Rhodnius robustus) and KP1- with members of the pallescens group (R. pallescens, R. colombiensis and Rhodnius ecuadoriensis).

Susceptibilidad de trypanosoma cruzi a diferentes venenos de serpientes de Costa Rica / Susceptibility of Trypanosoma cruzi to different Costa Rican snake venoms

Se evaluaron los efectos tóxicos de los venenos de cinco serpientes costarricenses en cuanto a su capacidad tripanocida contra dos cepas de trypanosoma cruzi y sus efectos en cuanto a los mecanismos de muerte celular. Los venenos de bothrops asper, bothriechis schlegelii, crotalus durissus durissus, atropoides nummifer y A. picadoi, mostraron actividad tripanocida contra las formas de epimastigoto, amastigoto y tripomastigoto. Los venenos de b. asper y de A. nummifer presentaron la más alta citotoxicidad para las células Vero. Los de b. asper y b. schlegelii presentaron la más alta actividad en los epimastigotos de la cepa CL, mientras que los venenos de b. asper y el de A. nummifer fueron más eficientes contra los epimastigotos de la cepa Jennifer. El veneno de b. schlegelii produce un efecto proliferativo en las células Vero; mientras que el de C. d. durissus produce el mismo efecto en los epimastigotos de la cepa CL, ambos a la concentración de 2,5 Ig/mL. Los valores de CI50 mostraron que se requieren menores cantidades contra los amastigotos en relación con los epimastigotos. Los venenos de b. asper y B. schlegelii presentan la más alta actividad contra los amastigotos de ambas cepas. Con los tripomastigotos sanguíneos de la cepa GA, los cinco venenos ocasionaron una disminución de la motilidad en los diferentes tiempos de exposición, pero el veneno de A. nummifer, en las concentraciones más bajas, mostró una actividad más marcada en comparación con los otros veneno. En cuanto a los efectos de los venenos, mediados por los grados de apoptosis, necrosis o proliferación celular, se observó que estos fenémenos se presentan y tienen relación con el tipo de veneno, su concentración y el tiempo de exposición.

The trypanocide effect of venoms from five Costa Rican species of snakes was evaluated against two strains of trypanosoma cruzi and their cellular toxic effects were likewise observed. The venoms of Bothrops asper, bothriechis schlegelii, crotalus durissus durissus, atropoide nummifer and A. picadoi showed evident trypanocide action against epimastigotes, amastigotes and trypomastigotes. The venoms of b. asper and b. schlegelii were shown to be the most active against the epimastigotes of the CL strain, whereas those of b. asper and A. nummifer were more effective against the epimastigotes of the Jennifer strain. The venoms of b. schlegelii and C.d. durissus, at the lowest concentrations of 2.5 Ig/mL, were able to trigger a proliferative effect on Vero cells and epimastigotes of the CL strain, respectively. The IC50 values showed that lower amounts of venoms are necessary in order to inhibit amastigotes as compared to epimastigotes. The venoms of b. asper and b. schlegelii exhibited the highest activity against amastigotes of both T. cruzi strains. All venoms were able to arrest motility of blood trypomastigotes of the GA strain at different times and the most active in this case was A. nummifer venom. The toxic effects of the venoms measured by the degree of apoptosis, necrosis and cell proliferation that they produced showed that all these events occur and are related to the type of venom, its concentration and exposure time.

A survey on Triatoma dimidiata in an urban area of the province of Heredia, Costa Rica

Triatoma dimidiata has been found in several cities and towns of those countries where the insect is a domestic or peridomestic pest. In Central America, urban infestations occur in the capitals of at least five countries. During 2001 and 2002 a survey was carried out in the county of San Rafael, Heredia province, located 15 km northwest of San José, capital of Costa Rica, in order to determine the degree of infestation by T. dimidiata in an entire city block. Six peridomestic colonies of the insect were detected in the backyards of eight households. The ecotopes occupied by the insects consisted of store rooms with old objects, wood piles or firewood, and chicken coops. A total of 1917 insects were found in the six foci, during two sampling periods, and a mean infection rate by Trypanosoma cruzi of 28.4% was found in 1718 insects examined. The largest colony found in one of the households yielded 872 insects that were thriving mainly at the expenses of two dogs. Opossums and adult insects were common visitors of the houses and it became evident that this marsupial is closely related to the peridomestic cycle of the Chagas disease agent. Lack of colonization of the insect inside the human dwellings is explained by the type of construction and good sanitary conditions of the houses, in contrast to the situation in most peridomiciliary areas. Stomach blood samples from the insects showed that the main hosts were, in order of decreasing frequency: rodents, dogs, fowl, humans, opossums, and cats.

Environmental management for the control of Triatoma dimidiata (Latreille, 1811), (Hemiptera: Reduviidae) in Costa Rica: a pilot project.

An ecological control method, using environmental management operations, based on biological and behavioral characteristics of Triatoma dimidiata (Latreille, 1811), was implemented as a pilot project in an area of Costa Rica where the bug is prevalent. The sample was represented by 20 houses with peridomestic colonies (two also had indoor infestation), divided in two equivalent groups of 10 each. In one group we intervened the houses, i.e. all objects or materials that were serving as artificial ecotopes for the bugs were removed, and the second group was used as control houses. After a year of periodic follow up, it became evident that in those houses with a modified environment the number of insects had decreased notoriously even after the first visits and this was more evident after a period of 12.5 to 13.5 months in which no insects were detected in eight of the houses. It also became clear that in this group of houses, recolonization by wild bugs from the surrounding areas, became more difficult, probably due to the absence of protection from bug predators. In the control houses, with the exception of three in which the inhabitants decided to intervene on their own, and another house with a peculiar situation, the insect populations remained the same or even showed a tendency to increase, as confirmed at the end of the experiment. We believe that the method is feasible, low costing and non contaminating. It could be used successfully in other places where T. dimidiata is common and also in countries where other species colonize peridomestic areas of homes. Environmental management of this kind should seek the participation of the members of the communities, in order to make it a more permanent control measure.

[Gallstone ileus and cholecystoduodenal fistula. Case report]. / Ileo biliar y fístula colecistoduodenal. Informe de un caso.

OBJECTIVE: We report on a patient with gallstone ileus and cholecystoduodenal fistula at the Hospital de Especialidades, Centro Medico Nacional Siglo XXI (IMSS) Mexico City, Mexico. CLINICAL CASE: A 54-year-old male patient was admitted to the hospital with a diagnosis of acute cholecystitis. He had undergone an appendectomy at 34 years of age. There was no history of biliary disease. He was afebrile, with moderate abdominal distention and right upper quadrant pain, Murphy (+). His white blood cell count was 8,900/mm(3) with 40% bands. His liver function tests, amylase and lipase, were all within normal limits. Ultrasound revealed edema and thickening of the gallbladder wall with calculi. He underwent exploratory surgery, which provided the following findings: sclerotrophic gallbladder with intense surrounding inflammation. We therefore decided to perform a cholecystostomy. Two days postoperatively the patient presented abdominal distention and vomiting as well as the presence of intestinal material through the cholecystostomy catheter. Plain abdominal film showed the bowel to be dilated and an aberrantly located gallstone. Cholecystography was performed and showed a cholecystoduodenal fistula. Computed tomography was carried out and disclosed the bowel to be slightly dilated and with an intraluminal gallstone. A laparotomy with enterolithotomy was performed. Sized of the gallstone found was approximately 3 cm. Presently the patient is asymptomatic.

Environmental management for the control of Triatoma dimidiata (Latreille, 1811), (Hemiptera: Reduviidae) in Costa Rica: a pilot project

An ecological control method, using environmental management operations, based on biological and behavioral characteristics of Triatoma dimidiata (Latreille, 1811), was implemented as a pilot project in an area of Costa Rica where the bug is prevalent. The sample was represented by 20 houses with peridomestic colonies (two also had indoor infestation), divided in two equivalent groups of 10 each. In one group we intervened the houses, i.e. all objects or materials that were serving as artificial ecotopes for the bugs were removed, and the second group was used as control houses. After a year of periodic follow up, it became evident that in those houses with a modified environment the number of insects had decreased notoriously even after the first visits and this was more evident after a period of 12.5 to 13.5 months in which no insects were detected in eight of the houses. It also became clear that in this group of houses, recolonization by wild bugs from the surrounding areas, became more difficult, probably due to the absence of protection from bug predators. In the control houses, with the exception of three in which the inhabitants decided to intervene on their own, and another house with a peculiar situation, the insect populations remained the same or even showed a tendency to increase, as confirmed at the end of the experiment. We believe that the method is feasible, low costing and non contaminating. It could be used successfully in other places where T. dimidiata is common and also in countries where other species colonize peridomestic areas of homes. Environmental management of this kind should seek the participation of the members of the communities, in order to make it a more permanent control measure.

Distribution and ecological aspects of Rhodnius pallescens in Costa Rica and Nicaragua and their epidemiological implications.

In light of the Central American Initiative for the control of Chagas disease, efforts were made on the part of Costa Rican and Nicaraguan teams, working separately, to determine the present status of Rhodnius pallescens in areas close to the common border of the two countries, where the insect has appeared within the last few years. The opportunity was also used to establish whether R. prolixus, a vector present in some areas of Nicaragua, has been introduced in recent years into Costa Rica with Nicaraguan immigrants. It became evident that wild adults of R. pallescens are common visitors to houses in different towns of a wide area characterized as a humid, warm lowland, on both sides of the frontier. Up to the present, this bug has been able to colonize a small proportion of human dwellings only on the Nicaraguan side. There was strong evidence that the visitation of the adult bug to houses is related to the attraction of this species to electric lights. There were no indications of the presence of R. prolixus either in Nicaragua or in Costa Rica in this area of the Caribbean basin. Triatoma dimidiata, a widespread domestic species in both countries, was totally absent in the explored areas of Costa Rica but occasionally occurs on the Nicaraguan side. Serological surveys in children of both areas showed that transmission of Chagas disease takes place in a rather small degree in Costa Rica and more commonly in Nicaragua, indicating that R. pallescens could be a potential threat as a vector in this particular region.

Distribution and ecological aspects of Rhodnius pallescens in Costa Rica and Nicaragua and their epidemiological implications

In light of the Central American Initiative for the control of Chagas disease, efforts were made on the part of Costa Rican and Nicaraguan teams, working separately, to determine the present status of Rhodnius pallescens in areas close to the common border of the two countries, where the insect has appeared within the last few years. The opportunity was also used to establish whether R. prolixus, a vector present in some areas of Nicaragua, has been introduced in recent years into Costa Rica with Nicaraguan immigrants. It became evident that wild adults of R. pallescens are common visitors to houses in different towns of a wide area characterized as a humid, warm lowland, on both sides of the frontier. Up to the present, this bug has been able to colonize a small proportion of human dwellings only on the Nicaraguan side. There was strong evidence that the visitation of the adult bug to houses is related to the attraction of this species to electric lights. There were no indications of the presence of R. prolixus either in Nicaragua or in Costa Rica in this area of the Caribbean basin. Triatoma dimidiata, a widespread domestic species in both countries, was totally absent in the explored areas of Costa Rica but occasionally occurs on the Nicaraguan side. Serological surveys in children of both areas showed that transmission of Chagas disease takes place in a rather small degree in Costa Rica and more commonly in Nicaragua, indicating that R. pallescens could be a potential threat as a vector in this particular region.

The finding of Rhodnius pallescens Barber, 1932 (Reduviidae: Triatominae) in palm trees (Attalea butyracea ) in north Costa Rica

A total of 167 nymphs and adults of Rhodnius pallescens was collected from the basal parts of dead fronds of two palm trees (Attalea butyracea ) in the town of Los Chiles, province of Alajuela, Costa Rica, close to the Nicaraguan border. Previous records of this species in the same habitat come from Panama and Colombia. A group of 32 insects examined for Trypanosoma cruzi revealed that all were infected. By examining their hemolymph, none of 24 of the insects was found infected with T. rangeli. Balb/c mice inoculated with the T. cruzi strain from infected insects showed a typical acute myocarditis reaction with numerous groups of parasites among the heart bers at autopsy. The geographical distribution of R. pallescens as well as its possible presence in other Central American countries and in Mexico where it is still unknown, coinciding with the distribution of the same species of palm tree, is discussed. Likewise, the potential of R. pallescens in becoming adapted to domestic environments is analyzed in light of recent information, and the epidemiological implications of the phenomenon are also discussed.