Barinas State Research Articles

DINÁMICA ESPACIAL DE LA MIGRACIÓN COLOMBIANA HACIA EL PIEDEMONTE BARINÉS

Venezuela is the second destination for Colombian migration. In this particular migratory dynamic, internal and external factors have both played a role. This migration pattern is characterized by the presence of Colombian citizens throughout Venezuelan territory, although not uniformly, as some areas are more attractive than others to the immigrants. Most of this immigrant population is located in the states bordering Colombia (Zulia and Tachira), as well as in the center-north region (Distrito Capital, Carabobo and Aragua). However, there is also a considerable proportion of Colombian immigrants in the state of Barinas (especially in the city of Socopo). This political-territorial entity has been an attractive space from the demographic standpoint, despite being on the periphery of the spatial organizational model in Venezuela. With these observations in mind, the spatial dynamics of the Colombian immigration to the foothills of the state of Barinas are analyzed, specifically with regards to the urban center Socopo, the shire town of the municipality of Antonio Jose de Sucre, based on the conclusions obtained by researching the Colombian population residing in the town, with the intention of interpreting its origins, the reasons that lead these people to establish themselves in this area and their routes of migration. In order to develop this research, a quantitative field methodology was adopted, with a bibliographical and documental basis, which took into account the life experiences of the immigrants themselves, as well as contributions from specialists in this subject area. The results showed that the on-going armed conflict in Colombia and the economic boom that swept Venezuela in the 1960s and 1970s, together with family ties, were the main drivers of Colombian immigration into Venezuela. Similarly, it can be deduced that the choice of Socopo as a destination had a relevant role in its condition of a functional knot in the foothills and the tip of the agricultural colonization of the Ticoporo forest reserve. Thus, the recently-constructed Llanos Highway (Troncal 5) became the backbone of this area, facilitating communications with this region. The inter-connections between external and internal factors resulted in a greater concentration of Colombian immigrants in the town of Socopo, compared to other urban centers in the state of Barinas.

Coupling soil water and shoot dynamics in three grass species: A spatial stochastic model on water competition in Neotropical savanna

Savannas are ecosystems known for their high environmental and economic value. They cover at least 20% of the global land surface and, in some cases, can act as a boundary between tropical rainforest and deserts. Water is an important determinant of savanna ecosystems. In this paper, we present a theoretical stochastic model of root competition for water, which couples, soil water availability, phenology, and root and shoot architecture applied to three Neotropical savanna grasses. Soil moisture was simulated using a daily balance, as proposed by Rodriguez-Iturbe et al. [Rodriguez-Iturbe, I., Porporato, A., Ridolfi, L., Isham, V., Cox, D.R., 1999. Probabilistic modelling of water balance at a point: the role of climate, soil and vegetation. Proc. R. Soc. London, Ser. A 455, 3789–3805.]. To simulate rainfall stochasticity, we used daily precipitation data from the airport weather station in the State of Barinas, Venezuela, for the period 1991–2007. Competition among neighbouring plants took into account the spatial distribution of the individuals. As a final step, the model allowed us to calculate the shoot dynamic of the species as a function of soil water availability. Using these data, we compared the behaviour of isolated plants, pairs and trios, and we found below-ground competition to be a fundamental component of global (shoot + root) competition. Finally, our model suggests various circumstances that allow poor competitor plants to coexist in competition for water with more successful competitors. Apparently, this is not only due to transpiration rates, but also to differences in shoot emergence and shoot growth.

RISK FACTORS FOR TRYPANOSOMA CRUZI HUMAN INFECTION IN BARINAS STATE, VENEZUELA

This study attempted to quantify the transmission of Trypanosoma cruzi in children less than 15 years of age in Barinas State, Venezuela and investigate risk factors for infection. Among 3,296 children, 4 (0.12%) were seropositive. The mother of one child also was also seropositive, which suggested that congenital transmission is a possible risk factor for Chagas disease in this area. Seroprevalence among the dwellers of 10 localities was 3.3%. Rhodnius prolixus was detected in 7 localities and in 8% of 125 dwellings. A multivariate logistic regression model showed that infection was associated with age, a dirt floor, and distance from houses to palm trees. The risk of infection is increased by the presence of adventitious sylvatic R. prolixus and transient or residual colonies. Insecticide spraying does not seem justified in this scenario, a finding that was also observed in other Latin American countries. New methods are therefore needed for Chagas disease control programs.

Morphometric evidence for a possible role of Rhodnius prolixus from palm trees in house re-infestation in the State of Barinas (Venezuela)

The main vector of Chagas disease in Venezuela is Rhodnius prolixus. Specimens of Rhodnius sp., identified elsewhere as R. prolixus by molecular tools, were collected in Barinas State (Venezuela) before insecticide application, and compared by morphometric techniques with post-spraying, re-infesting insects after control. Geometric morphometry was applied, allowing separate analyses of shape and size. The idea of a single species sharing silvatic and domestic/peri-domestic ecotopes was supported, suggesting new evolutionary scenarios for the controversial R. prolixus origins. The same data allowed to understand the possible mechanisms of villages re-infestation after a control campaign, either recolonization by local recovery of survivors or re-infestation by external migrants. Both mechanisms were apparent. Although shape properties could distinguish very close subpopulations such as insects from houses and insects from peri-domestic shelters, they were unable to identify the insects from palm trees as a distinct subpopulation. This strongly suggested that human environment could receive immigrants from palm trees. The pattern of size variation supported the hypothesis of a one-way exchange from silvatic to human environments, but did not support the reverse movement. Thus, morphometric data indicated that a silvatic population of the local vector is probably responsible for re-infesting villages after insecticide application, and they also pointed to the existence of re-infestation by local recovery of survivors. According to this interpretation, new epidemiological scenarios must be considered to improve Chagas disease control in Venezuela.

Could the Chagas disease elimination programme in Venezuela be compromised by reinvasion of houses by sylvatic Rhodnius prolixus bug populations?

The Andean Pact Initiative (1997) committed Andean countries to eliminate vectorial transmission of Chagas disease by 2010 via widespread residual insecticide spraying. In Venezuela, this aim could be compromised by reinvasion of houses by palm tree populations of the major vector Rhodnius prolixus. To test this hypothesis, a multivariate logistic regression was undertaken of risk factors for triatomine infestation and colonization in 552 houses and 1068 peri-domestic outbuildings in Barinas State. After adjusting for other risk factors, including palm roofs, R. prolixus infestation and colonization of outbuildings (and, to some extent, houses) was significantly associated with proximity to high densities of Attalea butyracea palm trees. House infestation and/or colonization was also positively associated with bug density in peri-domestic outbuildings, the presence of pigsties and nests. Hence, R. prolixus populations in ineffectively sprayed outbuildings could also provide an important source of house re-infestations. The secondary vector Triatoma maculata was mainly found associated with the presence of hens nesting both indoors and outdoors.

Palinología e icnología en la determinación del contacto discordante Cretácico-Terciario en Venezuela suroccidental y su impacto en la exploración por hidrocarburos

Palynology and ichnology in the determination of Cretaceous-Tertiary unconformity contact in southwestern Venezuela and their impact in hidrocarbons exploration. Palynological results from the southwest of Venezuela are given. The material comes from two wells drilled in Barinas state. Integration of results from analyses of marine and terrestrial palynomorphs, and ichnofacies, allows to determine the Maastrichtian-middle Eocene unconformity in well #1 at 9901´5´´ by the presence of Foveotriletes margaritae (Van der Hammen) Germeraad, Hopping & Muller, peridinioid dinocysts and the Glossifungites ichnofacies. In well # 2, the unconformity was established by the presence of F. margaritae, Ariadnaesporites Potonie and Buttinia andreevi Boltenhagen at 10154´6´´.

Postepizootic Persistence of Venezuelan Equine Encephalitis Virus, Venezuela

Five years after the apparent end of the major 1995 Venezuelan equine encephalitis (VEE) epizootic/epidemic, focal outbreaks of equine encephalitis occurred in Carabobo and Barinas States of western Venezuela. Virus isolates from horses in each location were nearly identical in sequence to 1995 isolates, which suggests natural persistence of subtype IC VEE virus (VEEV) strains in a genetically stable mode. Serologic evidence indicated that additional outbreaks occurred in Barinas State in 2003. Field studies identified known Culex (Melanoconion) spp. vectors and reservoir hosts of enzootic VEEV but a dearth of typical epidemic vectors. Cattle serosurveys indicated the recent circulation of enzootic VEEV strains, and possibly of epizootic strains. Persistence of VEEV subtype IC strains and infection of horses at the end of the rainy season suggest the possibility of an alternative, cryptic transmission cycle involving survival through the dry season of infected vectors or persistently infected vertebrates.

Predominance of lineage I among Trypanosoma cruzi isolates from Venezuelan patients with different clinical profiles of acute Chagas’ disease

Trypanosoma cruzi isolates from 23 acute chagasic patients from localities of Western Venezuela (state of Barinas) where Chagas' disease is endemic were typed using ribosomal and mini-exon gene markers. Results showed that isolates of the two major phylogenetic lineages, T. cruzi I and T. cruzi II, were isolated from these patients. Six isolates (26%) were typed as T. cruzi II and 17 (74%) as belonging to T. cruzi lineage I. Analysis of random amplified polymorphic DNA (RAPD) patterns confirmed these two groups of isolates, but did not disclose significant genetic intra-lineage polymorphism. Patients infected by both T. cruzi I or T. cruzi II showed different clinical profiles presenting highly variable signs and symptoms of acute phase of Chagas' disease ranging from totally asymptomatic to severe heart failure. The predominance of T. cruzi I human isolates in Venezuela allied to the higher prevalence of severe symptoms of Chagas' disease (heart failure) in patients infected by this lineage do not corroborate an innocuousness of T. cruzi I infection to humans. To our knowledge, this is the first study describing predominance of T. cruzi lineage I in a large number of acute chagasic patients with distinct and well-characterized clinical profiles.

Notes on the Amazonian genus Hyogonia China (Hemiptera: Cicadellidae: Proconiini) with a description of a new species

Oncometopia batesi Distant, described from northern Brazil (State unknown), is transferred to the genus Hyogonia China. Hyogonia brasiliana sp. nov. is described from Northern Brazil, Pará State, the easternmost record of the genus. The new species is easily distinguished from all other Hyogonia species by the following combination of characters: (1) pronotum without distinct transverse contrasting band; (2) pygofer with short processes that do not attain its apex; (3) both pairs of aedeagal atrial processes divergent and short, never longer than aedeagal shaft; and (4) aedeagal caudal pair of atrial processes with bases close to each other, appearing as a single bifurcated robust process. Hyogonia batesi and H. brasiliana, together with an unidentified female from Acre State, represent the first authentic records of the genus Hyogonia from Brazil. Previous records of H. reticulata (Melichar) and H. youngi Emmrich and Lauterer from Brazil are erroneous as their recorded locality ‘Cumbase’ is most probably located in Peru (San Martín Department). Other new records from countries and major federal divisions are noted as follows: the genus Hyogonia (unidentified species) from Barinas State (Venezuela); H. batesi from Ecuador (Orellana Province); H. reticulata from Amazonas and Junín Departments (Peru); and H. youngi from Ecuador (Napo Province). A key to the known species of Hyogonia is provided.

First Report of Frog Skin Disease in Cassava (Manihot esculenta) in Venezuela.

Frogskin disease (FSD) is a disease of clonally propagated cassava (Manihot esculenta Crantz) and has been reported to reduce cassava yields significantly in South America (1). FSD is caused by an uncharacterized virus that is restricted to South America. The evidence indicates FSD is transmitted by stem cuttings and graft (3). However, little information is available on its distribution and incidence in Venezuela. Eighty-seven samples with virus-like symptoms were collected with the help of technical staff and producers in cassava-producing states: Amazonas (1 sample), Aragua (7 samples), Barinas (35 samples), Cojedes (8 samples), Monagas (19 samples), and Portuguesa (17 samples). In these states, the average daytime temperature was 26°C, but the average was higher (>28°C) during the dry season. Samples were collected during the rainy season because high temperatures and dry field conditions appeared to suppress symptom expression, while cooler conditions tended to favor symptom development (2). Roots of sampled cassava plants were examined for the presence of FSD. A single 70- to 80-cm-long stem cutting was taken from each plant and subdivided into four pieces. Two pieces were used as rootstocks in graft-inoculation tests with Secundina scions for FSD detection, and two pieces were potted in sterilized soil to be used in other tests. All potted and grafted plants were kept in the Vegetable Virology Laboratory of the Faculty of Agronomy (Universidad Central de Venezuela), at an average temperature of 24°C and 80% relative humidity. FSD-infected plants were identified by mosaic symptoms on Secundina scions and the presence of 80-nm spherical viral particles. Most FSD-infected cultivars expressed only root symptoms. However, in the case of Secundina cvs. MCOL 22 and MCOL 113, foliar symptoms were also detected (1). FSD was found in a simple infection in one cassava sample from Aragua State (14.3% incidence, 1 of 7 samples) and in four cassava samples from Barinas State (11.4% incidence, 4 of 35 samples) associated with Cassava virus X (detected by double-antibody sandwich enzyme-linked immunosorbent assay). To our knowledge, this is the first report of FSD detection in Venezuela.

Prehispanic Causeways and Regional Politics in the Llanos of Barinas, Venezuela

In this article we discuss the Prehispanic earthen causeways (calzadas) that traverse the llanos (humid savannas) of Barinas state, Venezuela. A salient question is why the calzadas in this area connect some archaeological sites but not others. Some scholars have proposed that the calzadas were constructed primarily as an adaptive response to seasonal flooding. We assess this proposition by examining Late Gaván phase (A. D. 550-1000) data from along the Río Canaguá and find a lack of positive association between sites that experience seasonal inundations and linkage to the calzada network. Instead, we conclude that the configuration of Late Gaván calzadas is better explained by a series of economic, military, and religious factors, all related to the political dynamics of chiefdom organization on the regional level.

Cardiac involvement is a constant finding in acute Chagas' disease: a clinical, parasitological and histopathological study

During the last 8 years 58 acute cases of Chagas' disease were studied. Patients from an endemic area of the state of Barinas, Venezuela, showed fever (98%) and circulating forms of T. cruzi (100%), and were treated with oral benznidazole. The recorded mortality was 8.6%. Acute myocarditis was constantly found either in myocardial biopsies or at necropsy, even in patients without any other sign of cardiac compromise (36%), which was detected by chest X-ray in 58%, by 2D echocardiography in 52%, by resting ECG in 41% and by clinical findings in 27.5% of the patients. Cardiomegaly was due to pericardial effusion rather than ventricular dilatation in most instances. Treatment eliminated parasitemia but negativized serology in only 20% of patients. It also appeared to have little influence on the ongoing myocarditic process, emphasizing the need for better therapeutic schedules, able to avoid or control the early appearance of immunologic mechanisms and microcirculatory damage involved in the future development of chronic chagasic myocarditis.

Drained Fields at La Tigra, Venezuelan Llanos: A Regional Perspective

This paper discusses drained-field studies in Venezuela, beginning with the first investigations two decades ago that focused on field systems themselves and proceeding to recent research by the authors that examined the drained fields of La Tigra as part of a regional-scale project in the state of Barinas. The La Tigra fields are dated to the Late Gaván phase (A.D. 550-1000), a time of extensive habitation in the region. An analysis of excavated pollen samples from the drained fields and a nearby village site has revealed that whereas maize was the predominant plant, there was notable intersite variability in the secondary cultigens. The paper also considers whether population pressure could have prompted the construction of the La Tigra fields. A comparison of archaeological population estimates to estimates of potential population under varying assumptions of productive capacity yields no indication of demographic pressures. We suggest that drained-field construction in this case was motivated primarily by political-economic considerations, part of a strategy whereby the regional elite sought to stimulate and mobilize the production of surplus by village farmers.