Taxonomy and distribution of phlebotomine sandflies in Venezuela: II. The subgenus Trichopygomyia of the genus Lutzomyia (Diptera: Psychodidae)

Species of sandflies in the subgenuys Trichopygomyia of the genus Lutzomyia occurring in Venezuela are reviewd. A new species, Lutzomyia pinna n. sp. is described. A distribution map and a pictorial key for maleds are provided with remarks on the ecological data collected in Venezuela.

El rol de Cyrtograpsus angulatus (Crustacea; Brachyura) en los ciclos de vida de Microphallus szidati (Digenea; Microphallidae) y Falsifilicollis chasmagnathi (Acanthocephala; Filicollidae): algunos aspectos de su ecologia parasitaria

Basándose en el estudio de los helmintos larvales parásitos del cangrejo Cyrtograpsus angulatus Dana, 1851 (Microphallus szidati Martorelli, 1986 (Digenea; Microphallidae) y Falsifilicollis chasmagnathi Holcman-Spector et al., 1977 (Acathocephala; Fillicollidae) conjuntamente con el análisis de sus ciclos biológicos y el estudio de la prevalencia, intensidad y de los índices de asociación (comparados entre los hospedadores intermediarios y definitivos) se pudo concluir que: a) C. angulatus parece ser un excelente hospedador intermediario en los ciclos de vida de los helmintos estudiados; b) el tamaño de los cangrejos y la ocurrencia de amputaciones naturales en las hembras de mayor tamaño Spivak & Politis (en prensa) aparecen correlacionadas con la prevalencia; c) en los cangrejos estudiados la prevalencia para F. chasmagnathi fue mayor en los machos que en las hembras; d) la intensidad no apareció correlacionada con el tamño y el sexo de los hospedadores intermediarios; e) M. szidati y F. chasmagnathi estan fuertemente asociados en el hospedador intermediario; f) C. angulatus e Himantopus melanurus Vieilot, 1817 (Aves; Recurvirostridae) son citados como nuevos hospedadores, intermediario y denitivo respectivamente, para F. chasmagnathi; g) Chasmagnathus granulata Dana, 1851 es citado como un nuevo hospedador intermediario para M. szidati.

Estudos sobre a resistência ao jejum e aspectos nutricionais de Cavernicola lenti Barrett & Arias, 1985 (Hemiptera, Reduviidae, Triatominae)

In order to widen the present knowledge on the biology of this species, a study on the resistance to starvation was carried out among all nymphal stages and the adult stage (male and female). All evolutive stages were weighed on precision scale in three different nutritional situations: fed, non-fed and death registered after starvation. This procedure has allowed us to calculate the amount of blood taken in each stage and during the whole cycle, the average loss of weight during starvation and its relations with the initial weight. The insects were fed on mice and after eclosion or ecdisis they were isolated for observation of the starving period. Throuhout the whole experiment they were kept in a B. O. D./DOB incubator (28ºC and 90%R.U.). The resistance to starvation of the insects has grown from the first stage on (average of 15.5 days) to the fifth stage (average of 75.64 days); on the adult stage, the resistance period was equal to the third stage with an average of 41.76 for the males and 44.82 for the females. The amount of ingested blood was greater at the fifth stage worth 34.14 mg, corresponding to 2,04 times its initial weight. The average weight loss during the starvation was greater at the adult stage (23.95 mg), corresponding to 61.52% of the total weight.

Aspectos ecológicos de Simulium goeldii (Diptera: Simuliidae): relação entre substrato e densidade de larvas

The distribution of larvae of Simulium goeldii was studies in four streams in upland tropical forest near Manaus, Amazonas, Brazil. In each month 32 points were sampled, each with an area of 30 x 50 cm. The areas of all substrates available were measured at each point. The larvae of S. goeldii were collected and later counted for all substrate types where larvae of this species were found. The available substrates were classified into eight types: dry leaves, green leaves, branches, fruits, detritus, rocks and sand; anly the first four types had larvae present. The Kruskal-Wallis test and analysis of variance indicated that the larvae occupy these substrates differently; the Newman-Keuls identified the following differences in intensity of occupation of the susbstrates: branchs differ from roots, dry leaves and green leaves, and green leaves differ from roots and dry leaves. The highest density of larvae was observed on green leaves. However, because the most abundant substrates in the study area were roots and dry leaves, I suggest that the latter two substrates are the most important ones for the esteblishment of this population of S. goeldii.

Aspectos da biologia do Aedes albopictus (Skuse, 1894) (Diptera: Culicidae), a nível de campo

After the Aedees albopictus has been discoved by Neves & Espinola (1987) at Minas Gerais state, we begun studying some biologic aspects, such as breeding places, host preference, times of feeding and the preferred places for blood feeding.

Fecundity, parity, and adult feeding relationships among Nyssorhynchus malaria vectors from Venezuela

Relative to their pre-engorgement weights, nulliparous Anopheles nuneztovari consumed significantly smaller blood meals than A. marajoara, A. triannulatus or A. aquasalis. When females were deprived of sugar before blood feeding, only one-quarter of A. nuneztovari, but more than two-thirds of A. marajoara, A. triannulatus and A. aquasalis matured eggs. Sugar feeding before blood, or two sucessive blood meals by sugar-deprived females, increased the proportion of nulliparous a. nuneztovari which developed eggs, but not significantly so. Nearly all individuals of nulliparous, sugar-fed A. marajoara, A. triannulatus and A. aquasalis matured eggs after one blood feeding. Among A. nuneztovari, A. marajoara and A. aquasalis that matured some eggs in the laboratory, there were no positive correlations between the number of eggs developed and relative vlood mealsize. However, blood meals larger than the mean size significantly increased the chance that A. nuneztovari would develop some eggs. Mean fecundities of gravid A. nuneztovari and A. marajoara reared in the laboratory were significantly lower than those of the same species captured at human bait in nature. Post-engorgement access to sugar by A. nuneztovari (captured at human bait) did not influence fecundity, but significantly enhanced survivorship and the proporticon of individuals which retained eggs. Release-recapture experiments revealed that relatively small blood meals are typical of A. nuneztovari only during the first gonotrophic cycle. We suggest that multiple blood feeding, seemingly necessary for most A. nuneztovari to develop a first clutch of eggs, may increase the probability of infection with Plasmodium vivax where this mosquito species is a primary vector.

Field evaluation of an exoantigen-containing Babesia vaccine in Venezuela

Bovine babesiosis is endemic in Venezuela, causing significant losses in highly susceptible imported cattle. Current immunoprphylatic methods include the less desirable use of live parasites. Inactivated vaccines derived from exoantigen-containing supernatant fluids of in vitro Babesia bovis and B. bigemina cultures have been developed and constitute a major improvement in vaccine safety, stability and ease of handling. Vaccination trials conducted under field conditions provide the final evaluation of a culture-derived B. bovis-B. bigemina vaccine. During a 5-year period, approximately 8,000 cattle were vaccinated and 16 clinical trials carried out in. 7 states of Venezuela Clinical, serologic and parasitologic data were collected monthly from 10% of the animals over a 2-year period. Data were also collected from a similar number of nonvaccinated control cattle. Analysis of results from these trials demonstrated a reduction in the incidence of clinical disease among vaccinated animals and complete protection against mortality among vaccinated and nonvaccinated cattle. Use of this inactivated vaccine offers the best combination od safety, potency and efficacy for thew immunoprophylatic control of bovine babesiosis.

New approaches for the control and eradication of schistosomiasis in Venezuela

Schistosomiasis in Americawith the exception of Brazil, behaves as a chronic mild disease with few clinical manifestations due to low parasite burden. These features restrict the clinical and parasitological diagnosis. The most commonly used stool examination method, Kato-Katz, becomes intensitive when the majority of individuals excrete less than 100 eggs/g of feces. In view that antigen-detecting techniques have not been able to reveal light infections, the antibody detecting assays remain as a very valuable diagnostic tool for epidemiological surveillance. The Venezuelan Schistosomiasis Research group (CECOICE) has designed a mass chemotherapy strategy based on sero-diagnosis. Since blood sampling is one of the important limitating factors for large seroepidemiological trials we developed a simple capillary technique that sucessfully overcomed most of the limitations of blood drawing. In this sense, ELISA seems to be the most adecuate test for epidemiological studies. Soluble egg Schistosoma mansoni antigen (SEA) has been largely used in Venezuela. The sensitivity ELISA-SEA in our hands is 90% moreover its specific reach 92% when populations from non-endemic areas but heavily infected with other intestinal parasites are analyzed. The Schistosomiasis Control Program is currently carrying out the surveillance of endemic areas using ELISA-SEA as the first screening method, followed by the Circumoval Precipitin test for validation assay. The results with these two serological techniques allowed us to defined the criteria of chemotherapy in populations of the endemic areas. On the search of better diagnostic technique, Alkaline Phosphatase Immunoenzyme Assay (APIA) is being evaluated in field surveys.

Spatial and temporal distribution of anopheline larvae in two malarious areas in Sucre State, Venezuela

The spatial and temporal distribution of anopheline larvae was studied in two coastal malarious areas of Sucre, State, Venezuela. Seven habitat types were sampled in the village of Guayana and eight species of Anopheles were collected. Anopheles aquasalis was the predominant species collected and was most abundant in the brackish marsh habitat (71 larvae per 100 samples). It was most abundant during the rainy season. At the second location, Santa F e, six habitat types were sampled and four anopheline species were collected. Habitats where An. aquasalis was most abundant were temporary freshwater ponds (34 larvae per 100 samples) and mangroves (10.5 larvae per 100 samples). At this location it was also most abundant in the rainy season. During the dry season it was collected in small numbers in river pools (1.3 larvae per 100 samples) along with large numbers of An. pseudopunctipennis (479 larvae per 100 samples). Larval control could be an important component of the malaria control program because major habitats could be defined and presence and abundance of larvae was limited to specific times of year.

Adult abundance, biting behavior and parity of Anopheles aquasalis, Curry 1932 in two malarious areas of Sucre State, Venezuela

The principal vector of malaria in eastern Venezuela, Anopheles aquasalis, is exophagic and exophilic. Control using indoor insecticide house sprays has failed to lower the number of malaria cases. Therefore, studies were initiated in two villages of the eastern coastal state of Sucre to better understand this vector's biology and develop a more integrated control program. An. aquasalis was found to have a crepuscular biting behavior with a major peak at dusk and a minor peak at dawn. Mosquitos were collected more outdoors than indoors. Forty-seven percent of the biting took place before people went to bed (22:30 hr) and 69% of the mosquitos biting during this time period bite outdoors. Outdoor biting could be the reason why indoor spraying alone did not lower malaria cases. Seasonal abundance was greater in the rainy season compared to the dry season. Seasonal parous rates were high (78.3%-100%) and similar indoors and outdoors and between dry and wet season in Santa F e. In Guayana, the seasonal parity was lower (34.6%-42.2%) than Santa F e with indoor parity slightly higher than outdoors. Malaria cases were higher in Santa F e, but adult mosquito density was much lower than in Guayana. This difference could have been due to higher parity in Santa F e compared to Guayana. The greater distance to the nearest breeding site and presence of alternative hosts in Guayana can not be discounted as factors which contributed to the difference in malaria transmission between locations. We concluded that knowledge on seasonal occurrence, biting activity, resting behavior and breeding site location can be used to design a new control strategy for this vector.

Diagnosis of malaria by acridine orange fluorescent microscopy in an endemic area of Venezuela

Fluorescent (acridine orange) microscopical examination of capillary centrifuged blood (quantitative buffy coat [QBC®] analysis) and Giemsa stained thick blood smears (GTS) were compared for diagnosis of malaria in blood specimens from adults living in malaria transmission areas of the States of Bolivar and Amazonas in southeastern and south Venezuela, respectively. Of a total of 198 GTS examined, 95 subjects (48%) showed parasitaemia. Among the 95 blood films with a positive GTS, 94 were judged positive by the QBC. However, positive QBC tubes were found in 29 out of 103 blood specimens with a negative GTS. Thus, relative to a GTS standard, the sensitivity and specificity of the QBC-test was 99.2% and 72%, respectively. Young trophozoites of Plasmodium vivax and P. falciparum could not be distinguished with certainty. It is confirmed that the QBC offers many advantages compared with the standard diagnosis of malaria parasites, specifically in the speed of staining and ease of interpretation. However, in places where P. falciparum and P. vivax occur, species and stage differentiation should be confirmed with the GTS.