Adrián Avendaño

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

ABSTRACT 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.

Ectoparasites of dogs in home environments on the Caribbean slope of Costa Rica

Reports on ectoparasites on dogs in Central America are scarce. The aim of this study was to identify flea, louse and tick species infesting dogs in home environments on the Caribbean slope of Costa Rica, and determine their frequency and coexistence. Ectoparasites were collected from dogs in 83 rural homes at five study sites. Specimens were identified and separated according to species. Fleas were the most common ectoparasite (G = 22,217, DF = 8, p = 0.004). Ctenocephalides felis and Pulex simulans were found in 83% and 55% of the homes with ectoparasites, respectively. Trichodectes canis (13%), Heterodoxus spiniger (10%), Rhipicephalus sanguineus (18%), Rhipicephalus (Boophilus) microplus (5%) and Amblyomma ovale (8%) were also present. More than one species was collected in most cases (66%), and the most common combination was C. felis and P. simulans (59% of homes with fleas). The high frequency of P. simulans emphasizes the need for adequate identification. This was the first study involving different ectoparasites of dogs in Costa Rica, as well as the first report of T. canis in this country. The relative frequency and coexistence of these ectoparasites in the home environment may have implications for animal and human health.

Cinética multiplicativa de clones de Crithidia fasciculata (Kinetoplastida: Trypanosomatidae) en un sistema de cultivo in vitro

* Centro de Investigacion en Enfermedades Tropicales (CIET), Departamento de Parasitologia, Facultad deMicrobiologia, Universidad de Costa Rica, San Jose, Costa Rica. E-mail: olgerc@cariari.ucr.ac.cr** Laboratorio de Investigacion. Universidad de Ciencias Medicas “Dr. Andres Vesalio Guzman”. San Jose, CostaRica.

Heterogeneidad en la metaciclogénesis in vitro de clones derivados de una cepa costarricense de Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae)

The in vitro metacyclogenesis was evaluated in three clones derived from the Costa Rican TC-4 strain of Trypanosoma cruzi as a criterion of biological heterogenity between clones and their parental strain. The clones were obtained from colonies that resulted from culturing the T. cruzi strain in 40% blood agar. These clones were named TC-4 α, TC-4 β, and TC-4 π and were maintained in diphasic 40% blood agar with 3,7% brain hearth infusion as the liquid phase. The metacyclogenesis was induced by incubating epimastigotes in triatomine artificial urine suplemented with proline (TAU + P) at a constant temperature (27oC). The progress in the metacyclogenesis was monitored daily and the ratio of metacyclic trypomastigotes/epimastigotes, the percent of trypomastigotes, and the concentration of metacyclic trypomastigotes (MT/mL) were determined. Variability was evaluated using ANOVA tests for repeated measures (α: 0,05). The indicators of metacylogenesis showed the highest values between 72 and 96 hours after the beginning of the experiment. In this interval there were significant statistical differences between some of the cellular systems (p < 0,05). These observations could suggest that the clonal composition of each strain of T. cruzi can determine the infectivity for the vertebrate host.