Evidence of colonization of man-made ecotopes by Triatoma dimidiata (Latreille, 1811) in Costa Rica

Triatoma dimidiata adults have been frequently found, during the last five years, in a dog kennel and a chicken coop, in the back yard of a well-built house, 15 km from San José, the capital of Costa Rica. In the chicken coop nymphs were also found. Two of the 11 dogs from the kennel were serologically positive for Trypanosoma cruzi infection. The inhabitants of the house, three adults and two children, were negative. This type of colonization by the insect, which is attracted to lights, is becoming common in old and new settlements, with different degrees of success, a fact with epidemiological implications and great relevance in the control strategies that can be applied.     

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.     

Fertility, fecundity and gonadosomatic index of Poecilia reticulata (Pisces: Poeciliidae) in Heredia, Costa Rica

Between September and November of 1998, 1 432 females of Poecilia reticulata were collected in a pond in Santo Domingo, Heredia, Costa Rica. The average total length of females was 34.43 +/- 7.26 mm (range 17.80 and 51.50 mm) and the average total weight of 0.69 +/- 0.48 g (range 0.06 and 2.32 g). This species is a viviparous matrotrofic and the specimens were sexually mature. The total length-fertility relationship was F = 0.527e 0.1171Lt (r2 = 0.9404). The average fertility was 56.1 +/- 43.6 (eggs + embryos) (range 8.0 and 197.6). The total length-fecundity relationship was Fo = 0.695e(0.1076Lt (r2 = 0.9376). The average fecundity was of 49.0 +/- 36.0 (oocytes + ova) (range 7.0 and 179.0). The total length-gonadosomatic index relationship was IGS = 0.0014 e0.134 Lt (r2 = 0.8581). The average gonadosomatic index was 0.25 +/- 0.27% (range 0.02 and 1.31%).     

Tectonic survey of the Central Pacific coast of Costa Rica

Three fossil coral samples (Pocillopora elegans and Pocillopora damicornis) were collected from a beachrock in Puerto Escondido, central Pacific coast of Costa Rica. The age of the samples ranged from 1272+/-60 to 2010+/-60 years BP. They represent some of the few Holocene fossil corals known from the Pacific coast of the Americas. The uplift rate for the central Pacific coast of Costa Rica was calculated in 0.4 to 2.1 mm year(-1).     

Ecological control of Triatoma dimidiata (Latreille, 1811): five years after a Costa Rican pilot project

An ecological pilot project for the control of Triatoma dimidiata allowed a new evaluation four and five years after environmental modifications in the peridomestic areas of 20 households. It was verified that the two groups of houses, 10 case-houses and 10 control-houses, were free of insects after those periods of time. In the first group, the owners started a chicken coop in the backyard and a colony of bugs was found there without infesting the house. In the second group, the inhabitants of one house once again facilitated the conditions for the bugs to thrive in the same store room, reaffirming that man-made ecotopes facilitates colonization. This ecological control method was revealed to be reliable and sustainable and it is recommended to be applied to those situations where the vectors of Chagas disease can colonize houses and are frequent in wild ecotopes.     

A preliminary survey of the Chironomidae (Diptera) of Costa Rica,with emphasis on the lotic fauna

Extensive collections of Chironomidae were made in Costa Rica, Central America, during 1986 and 1987. Fifty-five genera and at least 148 species belonging to the subfamilies Podonominae, Tanypodinae, Orthocladiinae and Chironomidae were found. Chironominae and Orthocladiinae predominated. Only one species of Podonominae was collected. Tanypodinae was represented by many genera, but species richness was low.Cricotopus was the most widespread and diverse genus of Orthocladiinae. Among the Chironominae the generaPolypedilum, Pseudochironomus, Tanytarsus andRheotanytarsus showed high species richness. Several species were collected that could not be assigned to genus. A number of range extensions were recorded for taxa found in the Neotropical region for the first time and for Neotropical taxa recorded outside of South America for the first time. The Costa Rican chironomid fauna consists of cosmopolitan, holarctic and neotropical components. There is probably an endemic Central American chironomid fauna at the species level.     

Composition, growth and conditionindex for a population of Poecilia reticulata (Pisces: Poeciliidae), in a pond in Heredia, Costa Rica

A pond population of Poecilia reticulata was studied in Santo Domingo, Heredia, Costa Rica, between September and November of 1998. The sex ratio was 1:0.49 (males:females). The mean total length was 34.43 +/- 7.26 mm for females, 23.50 +/- 2.24 mm for males and 12.27 +/- 3.41 mm for juveniles. The mean total weight was 0.69 +/- 0.48 g for females: and 0.16 +/- 0.05 g for males and 0.026 +/- 0.027 g for juveniles. The total length-weight relationship for the total population was P= 6 x 10(-5) Lt 3.3272 (r2 = 0.9613). The condition index equation was K = 25.755 e(0.004Lt) (r2 = 0.8925) for females and K = 26.767 e(0.003Lt) (r2 = 0.907) for males. The mean condition index was 31.29 +/- 0.55% for females and 28.52 +/- 0.19% for males. Both sexes reached the sexual maturity when the males and females overcame the 20.00 mm and 23.5 mm of Lt respectively.     

The use of the Kohn chlorazol black fixative-stain in an intestinal parasite survey in rural Costa Rica

The Kohn one-solution chlorazol black (KCB) fixative-stain was used in the examination of stools from 162 children for intestinal parasites in rural, northern Costa Rica. Many more parasites were found by examining the stained smears than were seen on fresh smears. This was especially true of protozoan parasites. The advantages of the KCB technique are, as follows: (1) its simplicity; (2) the stability of the stain in solution and on slides; (3) the ability to use the stain with carbol-xylol in humid regions; and (4) the metachromatic qualities of the stain.     

Male and mosquito larvae survey at the Arenal-Tempisque irrigation project, Guanacaste, Costa Rica

A monitoring of male and larvae of mosquitoes was conducted during 1991-1994, at the Irrigation Project in Arenal-Tempisque, Guanacaste, Costa Rica. CDC CO2-baited traps were used to collect adults of mosquitoes and dips were used for immatures of culicids. A total of 1,480 larvae and 1,129 males of culicids were identified resulting in, Aedes with 6 species, Anopheles, Mansonia and Psorophora with 2 species, Culex with 21 species and Haemagogus, Limatus, Toxorhynchites and Uranotaenia with only one species each. The results indicate that, as occurred in other countries, irrigation projects must be under strict monitoring programs to prevent and control possible health problems in which mosquitoes act as vectors.     

A biogeochemical model for the Gulf of Nicoya, Costa Rica

In agreement with the Broecker and Penn two-boxes model, I generated a biogeochemical balance model for the Gulf of Nicoya (Guanacaste, Costa Rica) using two nutrient reservoirs: surface water and deep water. The mixing zone was located at a depth of 20 m. There is a balance between surface waters descending to the bottom and upwelling waters that carry nutrients and other chemical elements to the surface. The main source of nitrogen (nitrate), was the outlet of the Tempisque and Tárcoles rivers. The Gulf of Nicoya is a net source of Dissolved Inorganic Nitrogen (DIN) with an availability rate of 87 x 10(3) mol day(-1) in the dry season and 3044 x 10(3) mol day(-1)in the rainy season. Dissolved Inorganic Phosphate (DIP) was estimated in 27 mol day(-1) in the dry season and 207 mol day(-1) in the rainy season. The dynamics of these biolimited nutrients, in relation to runoff seasonal variations, fits the biological processes reported for the gulf, for example, for variations in primary productivity levels, and maturity and reproduction seasons for species with short and long life cycles.     

Lichens as air pollution indicators in the metropolitan area of San José, Costa Rica

Lichens were used as air pollution indicators in the metropolitan area of San José, Costa Rica. Transplants showed a positive correlation between the percentage of dead cells in the thallus and the ketone soluble substances deposited on it. Those parts of the city where pollution is greatest (industrial areas and heavy traffic) were also the ones where lichens suffered the most, and in some extreme cases the thallus died after 8 months of exposure. Besides this transplant experiment, the coverage of Parmelia lichens on the bark of several tree species was determined in some areas of the city. The results of these observations suggest that the city of San José has three different kinds of air environment in relation to lichen survival: normal, transitional and desertic, as reported for other cities of the world. The most frequent air pollutants in San José are: CO, CO2, C2H5OH, Cl2, HCl, H2S, H3PO4, H2CrO4, NO, NH3, NH4 Cl, SO2 and Zn.     

Seasonal profiles of Aedes aegypti (Diptera: Culicidae) larval habitats in an urban area of Costa Rica with a history of mosquito control

Dengue is the most important arboviral disease worldwide and the principal vector-borne disease in Costa Rica. Control of Aedes aegypti populations through source reduction is still considered the most effective way of prevention and control, although it has proven ineffective or unsustainable in many areas with a history of mosquito control. In this study, seasonal profiles and productivity of Aedes aegypti were analyzed in the city of Puntarenas, Costa Rica, where vector control has been practiced for more than ten years. Households contained more than 80% of larval habitats identified, although presence of habitats was more likely in other locations like lots and streets. In the wet season, habitats in the "other" category, like appliances, small manholes, and miscellaneous containers, were the most frequent habitats observed as well as the most common and productive habitats for Ae. aegypti. In the dry season, domestic animal drinking containers were very common, although concrete washtubs contained 79% of Ae. aegypti pupae collected. Individually, non-disposable habitats were as likely or more likely to contain mosquito larvae, and large containers were more likely to harbor mosquito larvae than the small ones only in the dry season. Considering various variables in the logistic regressions, predictors for Ae. aegypti in a habitat were habitat type (p < 0.001), setting (p = 0.043), and disposability (p = 0.022) in the wet season and habitat capacity in the dry season (p = 0.025). Overall, traditional Ae. aegypti larval indices and pupal indices in Puntarenas were high enough to allow viral transmission during the wet season. In spite of continued vector control, it has not been possible to reduce vector densities below threshold levels in Puntarenas, and the habitat profiles show that non-household locations, as well as non-disposable containers, should be targeted in addition to the standard control activities.     

Familial breast cancer in Costa Rica: an initial approach

Cancer is a worldwide problem because of its high rates of incidence and associated mortality. By 2000, more than 6.2 million people died from this illness worldwide. Among all types of cancer, breast cancer is one of the most studied. Each year, one million new cases are diagnosed around the world. We can classify breast cancer into two main kinds: sporadic cases and those which are a product of inherited genetic alterations. Approximately 5-10% of breast cancer cases are the result of inherited mutations, or alterations in breast cancer susceptibility genes, BRCA1 and BRCA2. Like other countries, Costa Rica possesses high rates of incidence and mortality for breast cancer. According to the "Registro Nacional de Tumores" (National Office of Tumor Records), in 2000 breast cancer had the highest rate of incidence and in 2002 it had the highest rate of mortality in comparison to other types of cancer. For this reason and the generalized lack of knowledge in the field we conducted an epidemiological research on breast cancer patients from Hospital San Juan de Dios, San José, Costa Rica, to find families with a history of breast cancer, and to determine the occurrence of familial cases within the population studied. So far, we have found 23 families, within which we discovered very informative cases that have rendered the identification of a pattern of inheritance. These findings allow us to announce that in Costa Rica there are several cases of inherited breast cancer and that we need more research is needed to improve the prevention, control, and treatment of this disease.     

Comparison of intervention strategies for control of Triatoma dimidiata in Nicaragua

The effectiveness of three operational strategies for the control of Triatoma dimidiata was compared by a field trial in the Department of Madriz, Nicaragua. One strategy involved full pretrial evaluation, followed by spraying of all houses irrespective of whether or not they had been found to be infested. The second strategy minimised the pretrial evaluation by considering the locality infested as soon as one house was found to be positive, followed by spraying all houses. The third strategy involved full pretrial evaluation, followed by spraying only those houses found to be positive. Evaluation after twelve months indicated that all three strategies were similarly effective, since all sprayed houses remained free of infestation. However, comparative estimates of the unit intervention costs indicated that strategies 1 and 2 were substantially less efficient than the third strategy of spraying only positive houses.     

The number of families of Triatoma dimidiata in a Guatemalan house

Triatoma dimidiata is an important vector of Chagas disease in Guatemala. To help understand the biology and population dynamics of the insect, we estimated the number of full sibling families living in one house. Forty one families with an average size of 2.17 individuals were detected using random amplification of polymorphic DNA-polymerase chain reaction genetic markers. This result suggests high levels of migration of the vector, polyandry, and a significant capability for spreading the disease.     

The bathymetry of Coco's Island, Costa Rica

The bathymetry of Coco's Island (UNESCO Natural and Cultural World Patrimony), located approximately 500 km from the Pacific coast of Costa Rica, is not well known. It has a high marine biodiversity and also represents a meeting site for many species traveling throughout the Pacific Ocean. The insular shelf is irregular in extension and also in bathymetric features. The northeast limit is defined by the 109.8-128.1 m contours (60-70 fathoms) while the 183 m contour (100 fathoms) practically defines the rest of the island, from which the depth gradient is steep. The maximum extension is to the northeast with a longitude of 13 km. In this context the present limits of the marine park (5 km), are insufficient to protect the whole insular shelf. Current regulation should be modified to prevent fishing activities less than 15 km from the Island.     

Eco-Bio-Social Determinants for House Infestation by Non-domiciliated Triatoma dimidiata in the Yucatan Peninsula,Mexico

Background

Chagas disease is a vector-borne disease of major importance in the Americas. Disease prevention is mostly limited to vector control. Integrated interventions targeting ecological, biological and social determinants of vector-borne diseases are increasingly used for improved control.

Methodology/principal findings

We investigated key factors associated with transient house infestation by T. dimidiata in rural villages in Yucatan, Mexico, using a mixed modeling approach based on initial null-hypothesis testing followed by multimodel inference and averaging on data from 308 houses from three villages. We found that the presence of dogs, chickens and potential refuges, such as rock piles, in the peridomicile as well as the proximity of houses to vegetation at the periphery of the village and to public light sources are major risk factors for infestation. These factors explain most of the intra-village variations in infestation.

Conclusions/significance

These results underline a process of infestation distinct from that of domiciliated triatomines and may be used for risk stratification of houses for both vector surveillance and control. Combined integrated vector interventions, informed by an Ecohealth perspective, should aim at targeting several of these factors to effectively reduce infestation and provide sustainable vector control.