Ecology of Sand Flies (Diptera: Psychodidae: Phlebotominae) in the North of the State of Mato Grosso, Brazil

Peixoto de Azevedo is located in the north of State of Mato Grosso, where environmental alterations led to an outbreak of American cutaneous leishmaniasis in the 80s. The parasite from patients was characterized as Leishmania (V.) braziliensis. The aim of this study is to contribute to the sand fly ecology of Central-West Brazil. Captures were carried out monthly using CDC light traps. Twenty-six species of sand fly were characterized; among which Lutzomyia (Lutzomyia) spathotrichia, L. runoides and L. (Psychodopygus) llanosmartinsi were recorded in the State of Mato Grosso for the first time. L. (Nyssomyia) whitmani, L. (N.) antunesi, L. (L.) spathotrichia, L. (P.) c. carrerai, L. (P.) complexa, L. (P.) lainsoni and L. (N.) umbratilis constituted 92.4% of the local fauna, among which L. (N.) whitmani and L. (N.) antunesi, accounting for about 53% of the fauna at the stations of capture. On the vertical distribution of sand flies on the Beira-Rio Farm, L. (N.) whitmani and L. (N.) antunesi prevailed at ground level and in the canopy, respectively, whereas on the BR-080, L. (P.) llanosmartinsi was prevalent on the ground and L. (P.) c. carrerai, in the canopy. It is suggested that L. (N.) umbratilis is the local vector.

Chagas Disease in Dogs from Endemic Areas of Costa Rica

Dogs with the presumptive diagnosis of Chagas disease are commonly sent to our School of Veterinary Medicine by independent veterinarians. This prompted us to evaluate the prevalence of canine trypanosomiasis in some villages of the Central Valley of Costa Rica. A total of 54 dogs (21 males and 33 females) from five rural villages, with ages between 3 months and 10 years old, were bled and submitted to three serological tests: indirect immunofluorescence, indirect hemagglutination and ELISA. Among all animals, 15 (27.7%) revealed antibodies (6 pure bred and 9 mongrels) and in 3 of them the parasite was also demonstrated by xenodiagnosis. All positive animals except 1, and 9 negative animals (control group) were examined by X-rays and electrocardiography, revealing different degrees of cardiomegaly and ECG alteration, consistent with Chagas disease pathology in one dog (SA-11) of the infected ones. Examination of 50 inhabitants living in the houses where dogs and Triatoma dimidiata were found, yielded negative serological reactions. This was assumed to support the hypothesis that dogs are commonly infected by the oral route, a more effective means of infection compared with the vector transmission mechanism that occurs in humans.

Schistosomiasis mansoni in Bananal (State of São Paulo, Brazil): II. Intermediate hosts

We conducted monthly snail captures in Bananal, State of São Paulo, Brazil, between March 1998 and February 2001, to identify Schistosoma mansoni vectors, estimate seasonal population changes, and delimit foci. We also evaluated the impact of improvements in city water supply and basic sanitation facilities. We identified 28,651 vector specimens, 28,438 as Biomphalaria tenagophila, 49 of them (0.2%) infected with S. mansoni, and 213 as B. straminea, none of the latter infected. Vectors predominated in water bodies having some vegetation along their banks. Neither population density nor local vegetation could be linked to vector infection. We found the first infected snails in 1998 (from March to May). Further captures of infected snails ocurred, without exception, from July to December, when rainfall was least. Irrespective of season, overall temperature ranged from 16.5ºC to 21ºC; pH values, from 6.0 to 6.8. Neither factor was associated with snail population density. Frequent contact of people with the river result from wading across it, extracting sand from its bottom, fishing, washing animals, etc. Despite a marked reduction in contamination, cercaria shedding persists. Whatever the location along its urban course, contact with river Bananal, particularly of the unprotected skin, entails risks of infection.

Schistosomiasis mansoni in Bananal (State of São Paulo, Brazil): I. Efficiency of diagnostic and treatment procedures

Bananal is an important focus of Schistosoma mansoni in the State of São Paulo. Accordingly, programmed active search for human cases, annual coproscopic surveys and treatment of infected cases were started in 1998, aiming at producing a sharp prevalence rate drop by the year 2000. S. mansoni eggs were searched for in two Kato-Katz slides per patient. Cases were followed up according to the routine of the local Family Health Program. In 1998, 130 samples out of 3,860 showed S. mansoni eggs; in 1999, 105 out of 3,550, and in 2000, 64 out of 3,528. Prevalence rates were 3.4%, 2.9%, and 1.8%, and average egg-counts 59, 64, and 79 eggs per gram of feces respectively. Prevalence rates decreased steadily after treatment, but persistently positive cases showed no significant decrease in parasite burdens. Egg count variation depended on sex and age bracket. Persistent residual cases admittedly preclude the eradication of this infection by only searching for and treating carriers. In addition, resistance to therapy and low sensitivity of fecal examinations, can not be ignored. Moderate to heavy worm burdens, frequently associated with hepatomegaly elsewhere, produced no serious cases in Bananal.

Llorenç Tomàs i Costa : Els temps convulsos de la guerra de Successió i l'exili

Aproximació biogràfica al personatge de Llorenç Tomàs i Costa, canceller del Principat de Catalunya durant el govern de l'arxiduc Carles III (1705-1714)

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. The fact that no indication of infection with Chagas disease could be detected in the human occupants of the infested houses, vis a vis the high infection rate in dogs, is discussed.

Dispersal pattern of the sand fly Lutzomyia neivai (Diptera: Psychodidae) in a cutaneous leishmaniasis endemic rural area in Southeastern Brazil

The dispersal pattern of the sand fly Lutzomyia neivai was studied through mark-release-recapture experiments in an American cutaneous leishmaniasis endemic rural area in Southeastern Brazil. Over 6500 specimens were marked with fluorescent powder and released in forest edge and peridomicile habitats from August to November 1999, February and April 2000. Recapture attempts were made using Shannon and CDC traps up to eight successive nights after releases. A total of 493 (7.58%) specimens were recaptured. The number of recaptured males and females of L. neivai in CDC traps was not affected by the distance between the trap and the release points. Approximately 90% of males and females recaptured in CDC traps were caught up to 70 m from the release points. The maximum female flight range recorded was 128 m. The average flight range per day was less than 60 m for males and females. Of the flies released in forest edge, approximately 16% of the recaptured females were caught in Shannon traps in the peridomicile habitat. The results indicate that the movements of L. neivai are spatially focal and the possibility of dispersion from forest to peridomicile habitat may be an important way of contracting leishmaniasis in dwellings.

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.

Identification of sex pheromones of Lutzomyia longipalpis (Lutz & Neiva, 1912) populations from the state of São Paulo, Brazil

In Brazil, four populations of Lutzomyia longipalpis each producing different sex pheromones are recognised. It has been suggested that these chemotype populations represent true sibling species. In this study we present the results of an analysis, by coupled gas cromotography - mass spectrometry, of the pheromones of males L. longipalpis from two different municipalities of the state of São Paulo. Our study showed that L. longipalpis from these two municipalities produced different sex pheromones from each other. This coupled with the remarkable difference between the epidemiological situation in Araçatuba and Espírito Santo do Pinhal, suggests that the (S)-9-methylgermacrene-B and cembrene-1 populations may have different vectorial capacities.

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.

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.