Implementation and Evaluation of an Integrated Program for Rodent Control in a Shantytown of Buenos Aires City, Argentina

The objective of this work was to evaluate the efficiency of an integrated program for the control of rodents in a shantytown of Buenos Aires City, Argentina. This program was developed in one year. During the preparation phase, an environmental survey of public spaces and dwellings was conducted in the test area to identify factors favoring the presence of rodents and to determine strategies and management measures to be implemented in the execution phase. Rodent abundance was monitored in the following four periods: (1) during the preparation phase, (2) during the execution phase, (3) immediately after the execution phase, and (4) 90 days after the end of the execution phase. According to the results of the preparation phase, we combined three different strategies to reduce rodent abundance in both dwellings and public spaces of the experimental area: rodenticide application, environmental sanitation in public spaces, and sanitary education. In this area the proportion of dwellings and public spaces with signs of rodent activity decreased significantly from the beginning of the trial to immediately after the end of the execution phase. There was a significant increase in rodent activity 90 days after the execution phase. This work reveals that although rodent infestation can be reduced in urban shantytowns, a long-term policy for sanitation improvement and sanitary education is required to keep rodent populations at safe levels for the community.     

Rodent control at different spatial scales on poultry farms in the province of Buenos Aires,Argentina

In poultry farms of central Argentina rodents cause economic losses by the consumption and contamination of chicken food, and also pose a serious sanitary risk as transmitters of several diseases to human and domestic animals, such as leptospirosis, salmonellosis, trichinosis, hantavirus pulmonary syndrome, hantavirus renal syndrome, and Argentine hemorrhagic fever. Because one of the problems in controlling rodents is recolonization from the surroundings, we wanted to assess the effect of control measures applied at different spatial scales on rodent abundance in farm sheds. The treatments applied were the following: anticoagulant application in farms and their surroundings (F + S), anticoagulant application only within farms (F), and standard management (C). Rodent abundance was assessed previous to treatments (t₀), at the moment of bait removal (t₁), and after 15 (t₂), 30 (t₃), and 60 days (t₄). Differences in rodent abundance between t₀ and t₁, t₂, t_3, and t₄ were compared among treatments by means of a Kruskal Wallis test. We only found significant differences among treatments between t₀ and t₂, where F and F + S treatments showed differences with respect to the C treatment. This result suggests that the effect of control measures was due to the control of the perimeter, and not of farther areas. Also, reproduction of remaining individuals may have contributed to the population recovery in sheds of experimental farms. We conclude that more effective control must include the perimeter of the farm, but the effect of control of more distant areas may depend on the characteristics of the particular farm, its surroundings, and the ecology of the species involved.     

Environmental degradation and opportunities for riparian rehabilitation in a highly urbanized watershed: the Matanza-Riachuelo in Buenos Aires,Argentina

Wetlands Ecology and Management - The growth of human societies worldwide has been associated with the degradation of natural resources; in particular, freshwater ecosystems are among the most...     

Quantitative aeropalynology in the atmosphere of Buenos Aires city, Argentina

For the first time, a volumetric study ofBuenos Aires city atmosphere was conductedusing a Lanzoni collector from March 1997through March 1998. Fifty-four pollen typeswere recorded of which 13 had a relativeconcentration of more than 1% of the yearlytotal. The lowest concentration of pollengrains was recorded in June, when Urticas,pp., Morus spp., and Myrtaceae were low.On the other hand, the highest concentration ofpollen grains was reached in September, with anincrease in Fraxinus spp. Theaeropalynological record may be divided intothree periods: *AP Dominant from July toOctober, *NAP Dominant from November toMarch, and *Residual Period from April toJune with low pollen concentrations.The greatest number of species was recorded inNovember, when 32 types were present, and thelowest number of species in June, when only 13pollen types were recorded. In June, the pollenconcentration was not dominated by any specieswhereas in September 85% of the pollen wasderived from one species of Fraxinus.Earlier studies on the aeropalynology of BuenosAires City were performed using Tauber andRotorod samplers. They were comparable to thisstudy, especially since the pollen peak wasreached in September, although the main pollenproducing species were different.     

Fungemia in hospitals of the City of Buenos Aires, Argentina

BackgroundThe incidence of fungi like pathogens in hospitals varies by regions.ObjectivesOur goal was not only to record the incidence and etiology of fungaemia, but also the change during the 4 years analysed, to determine the time of detection in automated blood culture and by lysis-centrifugation, and finally to assess the gender, age and underlying disease of the patients with fungaemia.MethodsAn observational multicentre study of fungaemia was conducted in hospitals in the Mycology Network of Buenos Aires.ResultsA total of 190,920 blood cultures were processed: 182,050 automated blood culture and 8,870 lysis-centrifugation. Fungi were recovered in 1,020 episodes. The overall incidence of fungaemia was 1.72/1,000 admissions; 683 episodes were due to Candida (68%), and 325 (32%) to other fungi: 214 Cryptococcus, 105 Histoplasma, 7 Rhodotorula, 5 Trichosporon, 2 Pichia, 2 Acremonium, one Saccharomyces and one Fusarium. The incidence of candidaemia was 1.15/1,000 admissions with a wide variation between centres (0.35 to 2.65). Most Candida isolates (97%) were detected in the first 2 days of incubation. Candida albicans was recovered in 43% of the episodes. In fungaemia other than candidaemia, the predominant fungi were Cryptococcus and Histoplasma capsulatum.ConclusionsThe incidence remained stable during the study period. Fungaemia by Candida were predominant. C. albicans was involved in less than a half of the episodes. The recovery of Cryptoccocus and H. capsulatum is strongly associated with HIV patients.     

Academic network for nature conservation in Tandilia System,Buenos Aires,Argentina

The Tandilia System, located in the Southern Pampa region of Argentina, contains areas with conservation value scattered throughout its agricultural landscape. Unfortunately, efforts for their conservation and sustainable management are scarce and isolated, which may be explained by the lack of articulation and linkage between the different social actors in the territory. Based on 123 surveys of academics working in this field, we analyzed research lines, management and outreach experiences, and the synergies and interactions between them. The most frequent research topics were related to biodiversity, terrestrial ecosystems, landscapes, anthropic pressures, and environmental management. Twenty-six environmental management experiences were reported in which the creation and/or planning of protected areas were the most frequent. The analysis of academic-social networks allowed us to explore the relationship between actors. A high degree of network modularity was identified, with strong links within the research groups, but few connections between them. In general terms, these connections depend on a few actors with a high degree of intermediation. Additionally, some professionals presented a high degree of betweenness, which is an important potential for the efficient coordination of conservation and management projects. Our results suggest the relevance of fostering greater interaction between professionals and research groups, as well as of promoting joint management activities concerning nature care in the Tandilia System.     

Parasitoid assemblages of soybean defoliator Lepidoptera in north-western Buenos Aires province, Argentina

1 The objective of this study was to examine the structure of parasitoid assemblages attacking soybean defoliator Lepidoptera in north-western Buenos Aires province, Argentina. 2 Through larvae sampling from 1992 to 1996, and laboratory data plus the known biology of the species recorded during the study, parasitoid species composition, richness, number of guilds per host species, and levels of parasitism, were determined. 3 Total species richness was 23, all species were primary endoparasitoids, and categorized as koinobionts. They belonged to Hymenoptera (11 species) and Diptera (12 species). Rachiplusia nu (Noctuidae) hosted the highest number of parasitoid species. 4 Four parasitoid guilds were recorded for R. nu (egg–prepupal endoparasitoid, early larval endoparasitoid, late larval endoparasitoid, and larval–pupal endoparasitoid); two for Spilosoma virginica (Arctiidae) (late larval endoparasitoid and larval–pupal endoparasitoid) and Colias lesbia (Pieridae) (early larval endoparasitoid and larval–pupal endoparasitoid); and one for Anticarsia gemmatalis (Noctuidae) and Loxostege biffidalis (Pyralidae) (early larval endoparasitoid). 5 Only four out of seven potential parasitoid guilds defined for Lepidoptera were recorded in a soybean agroecosystem located in north-western Buenos Aires province, suggesting that potential host niches were not totally utilized. 6 Soybean lepidopteran defoliators supported a mean species richness of 4.8 parasitoids, a result that is similar to that reported for exophytic hosts in the Neotropics. 7 Parasitoid assemblages from each host differed in species composition, richness, number of guilds, and levels of parasitism.     

Airborne pollen sampling in a wildlife reserve in the south of Buenos Aires province,Argentina

The objective of this project was to study the pollen spectrum of the Marahué Wildlife Reserve (Central Argentina), the quantity and quality of airborne pollen grains, and to evaluate the contribution of outside sources, to protect a natural habitat with xerophytic shrub vegetation (“monte”) (the term “monte” is used for the dominant xerophytic shrub vegetation in the “partido” of Villarino) approximately 90 km south of Bahía Blanca. Sampling was performed weekly throughout a whole calendar year (January–December, 2003) using a volumetric impact sampler. Observations of flowering in the field were performed at the same time as the aerial sampling. Herbarium specimens were collected to make pollen collections of the species found in the study area, for reference purposes. The most abundant pollen types were Poaceae (31.3% total annual pollen), Amaranthus/Chenopodiaceae (25.3%), Eucalyptus (5%), Brassicaceae (3.9%), and Plantago (3.9%). This study showed the dispersion dynamics of pollen grains from characteristic species of the “partido” (the province of Buenos Aires is divided into partidos which are roughly equivalent to counties) of Villarino, the exotic flora of the surrounding area, and the pollen types from outside the region.

Breeding biology of the White-rumped Swallow Tachycineta leucorrhoa in Buenos Aires Province, Argentina

We conducted a study of the breeding biology of the White-rumped Swallow Tachycineta leucorrhoa nesting in nestboxes in a flat, farming landscape in Buenos Aires Province, Argentina. White-rumped Swallow nesting attempts were detected from the end of September to mid December, with most clutches laid during October. Birds laid clutches of 4–6 eggs with a mode of five eggs; most broods hatched synchronously (58%), but hatching spread could last up to 4 days. Nestling growth curves adjust well to logistic functions, and at day 15 nestlings attain the asymptotic weight of 21.6 g. Clutch size in White-rumped Swallows declined significantly as the season progressed. In addition, late-season eggs were smaller and late-season nestlings had a shorter nestling period and lower weight at day 15, probably leaving the nest lighter than early-season nestlings. These data suggest that the Swallows would benefit greatly from laying early in the season, which would provide nestlings with better survival prospects. However, both major sources of nest mortality, interspecific competition for nest-sites and nestling mortality during bad weather, decreased through the season. White-rumped Swallows follow the pattern found for other southern species, as it has smaller clutch size, lower growth rate and remains longer at the nest than its Northern Hemisphere congener the Tree Swallow Tachycineta bicolor .     

Phytoplankton chlorophyte structure as related to ENSO events in a saline lowland river (Salado River,Buenos Aires,Argentina)

We analyzed the phytoplankton present in the lower sector of the Salado River (Buenos Aires, Argentina) for 10 years (1995–2005) and detected significant changes occurring in chlorophyte abundance and species richness during La Niña event (1998–1999), which period was analyzed throughout the entire basin (main stream and tributaries). We compared the physicochemical and biologic variables between two El Niño–La Niña–Southern Oscillation (ENSO) periods – El Niño (March 1997–January 1998) and La Niña (May 1998–May 1999) – to identify possible indicators of a relationship between climatic anomalies and chlorophyte performance. Chlorophyte density increased during the La Niña. Under normal or extreme hydrologic conditions, mobile (Chlamydomonas spp.) and nonmobile (Monoraphidium spp.) chlorophytes codominated. These species belonged to Reynolds's functional groups X1 and X2, those typical of nutrient‐enriched environments. Comparative analyses between El Niño and La Niña periods indicated significant differences in physicochemical (K⁺, dissolved polyphenols, particulate reactive phosphorus, alkalinity, pH) and biologic (species diversity and richness, phytoplankton and chlorophyte total densities) variables between the two periods at all basin sites. During the La Niña condition, species richness was greater owing to interconnected shallow lakes and drainage‐channel inputs, while the Shannon diversity index was lower because of the high abundance values of Monoraphidium minutum. A detailed analysis of the chlorophytes in the entire basin, indicated that changes in density and species dominance occurred on a regional scale although diverse chlorophyte assemblages were identified in the different sectors of the Salado River basin. After La Niña event, the entire basin had the potential to revert to the previous density values, showing the resilience to global environmental changes and the ability to reestablish the general conditions of stability.     

Wild bees (Hymenoptera: Apoidea) in an urban botanical garden in Buenos Aires,Argentina

We assessed bee diversity and abundance in a botanical garden in the city of Buenos Aires during two consecutive spring–summer periods. Every 15 days, we collected by hand-netting bee specimens seen foraging on flowers during five-minute censuses at every entomophilous herbaceous plant. A total of 66 bee species (Hymenoptera: Apoidea) were recorded. Richness and abundance of native, generalist, and above-ground nesting (cavities) species were higher than that of exotic, specialist, and below-ground (soil) nesting ones, respectively. Social bees were more abundant, while the richness of solitary species was higher than that of social bees. Cleptoparasitic species were represented by a high number of species, even though only a few individuals were captured. Our results suggest that the studied area is an important bee reservoir within the city.     

Tire-breeding mosquitoes of public health importance along an urbanisation gradient in Buenos Aires, Argentina

Used vehicle tires are a source of mosquito vectors and a means of their introduction and expansion. With the aim of assessing the effects of urbanisation on the main mosquito vectors in temperate Argentina, the infestation levels of Aedes aegypti (L.) and Culex pipiens L. were studied in used tires from highly urbanised cities to low-urbanised small towns in Buenos Aires. Immatures of both species accounted for 96% of the 9,722 individuals collected; the total individuals collected represented seven species. The percentage of water-filled tires containing mosquitoes [container index (CI)] was 33% and the percentage of infested sites [site index (SI)] was 65.2%. These indexes decreased significantly from low to high urbanisation levels for both mosquito species. The relative abundance (RA) of Ae. aegypti immatures was slightly higher toward large cities, but showed no difference for Cx. pipiens. The CI of shaded tires was significantly higher than the CI of exposed tires for both mosquito species. There was no difference in RA values between shaded and sunlit tires. The CI and the SI were highest during the summer across the urbanisation levels, except for Cx. pipiens, which continued to increase during the autumn in small towns. Results related to urbanisation gradient, sunlit exposure and seasonality are discussed.     

Seasonal fluctuation of the Oomycetes in a polluted environment: Santigo River and affluents (Buenos Aires, Argentina).

Oomycetes are ubiquitous filamentous water molds. They occur as saprotrophs on bits of substrata of both plant and animal origin, principally in fresh water. This paper results from an integral research on the Oomycetous flora of Santiago River and several associated shallow streams (Buenos Aires, Argentina). Information is provided concerning this polluted habitat and seasonal distribution of the zoosporic fungi. The principal physico-chemical characteristics of the aquatic environmental samples are described: temperature, pH, dissolved oxygen, nitrate concentration, sulphate concentration, phosphate concentration and heavy metals.     

Seasonal pattern of abundance of Aedes aegypti (Diptera: Culicidae) in Buenos Aires City, Argentina

In Buenos Aires, the most crowded city of Argentina, there is a potential risk of dengue virus transmission by the mosquito Aedes aegypti during late summer. The temporal patterns of oviposition activity and abundance of breeding sites of this vector were studied in two cemeteries of the city. Between September 1998 and August 1999, we examined 142 ovitraps weekly and a total of 18,010 water-filled containers. Both study areas showed remarkable differences in the percentages of positive ovitraps (19% vs 8%) and breeding sites (18% vs 1%), but similar temporal abundance patterns. The percentage of breeding sites was higher in summer and autumn than in spring and winter, and the percentage of positive ovitraps was higher in summer than in the other three seasons. Immatures were recorded from the first week of October to the second week of July, and oviposition activity from the third week of October until the end of April. In both cemeteries and with both methodologies the highest infestation levels were registered in March (ovitraps: 41.8% and 20.6%, breeding sites: 39.2% and 3.4%). These highest abundances took place after several months with mean temperatures above 20 degrees C and accumulated rainfalls above 150 mm. A sharp decline in oviposition activity was observed when monthly mean temperature decreased to 16.5 degrees C, and no eggs were found below 14.8 degrees C. Seasonal fluctuation of Ae. aegypti abundances in mid-latitudes like Buenos Aires would allow reduction of the egg mosquito population through the elimination of containers during the coldest months, which are free of adults.     

Odonata Diversity and Synanthropy in Urban Areas: A Case Study in Avellaneda City,Buenos Aires,Argentina

The increase of human population, especially in urban areas, correlates with an alarming destruction of green spaces. Therefore, understanding the mechanisms by which urbanization processes affect biodiversity is crucial in integrating the environment in a proper urban planning. The main urban center of Argentina is known as the Greater Buenos Aires (GBA), and it includes the autonomous city of Buenos Aires and 24 surrounding districts. Avellaneda, one of the districts of the GBA, is an important urban and industrial center with green areas and low level of urbanization on the coastal area of the Río de la Plata. This paper provides the first Odonata inventory for Avellaneda, determines the species’ level of synanthropy with the Nuorteva index, and assess the Odonata species replacement along a latitudinal gradient on the occidental margin of the Río de la Plata.     

Applying Health Risk Analysis to Assess the Chemical Quality of Water for Recreational Bathing: The Case of Tres Arroyos Creek,Buenos Aires,Argentina

The aim of the study is to assess the probabilistic non-cancer and cancer risks by recreational bathing in Tres Arroyos creeks (southeastern Buenos Aires Province, Argentina). In these waters, hazardous substances (heavy metals, pesticides) have been detected, possibly related to agricultural activities. To assess such risk, USEPA models in aggregated (exposure through accidental oral water intake and dermal contact simultaneously) and cumulative approaches (combined exposure to more than one substance) were applied, performed for bathers of 5, 10, 15, and 20 years old. The results show that chronic bathing in these waters is not harmful at the concentrations and the exposure scenarios considered. Arsenic was the riskiest substance for both non-cancer and cancer effects, affecting mainly the youngest age group, and the accidental water intake during bathing was the most relevant pathway of exposure. On the other hand, the study highlights the key role of the frequency and duration of the bath event. We discuss the results in light of a previous paper of our authorship concluding that the health risk assessment is a valid alternative to analyze recreational water quality, which, unfortunately, is unused by water management agencies in Argentina.     

Sexual dimorphism in schoolchildren of the Villa IAPI neighborhood (Quilmes,Buenos Aires,Argentina)

Villa IAPI is a poor neighborhood of about 5,000 inhabitants in the overpopulated conurbano bonaerense at the outskirts of the city of Buenos Aires. Most of the adult male residents are construction workers; the rest are temporary workers, underemployed, or unemployed. The inhabitants of Villa IAPI suffer the effects of many adverse socio-economic conditions, including poor nutrition, deficient sanitation, and inadequate medical care. Seven anthropometric variables were measured on 765 children from 6 to 14 years old to test for the presence of an altered pattern of sexual dimorphism. It was found that there were practically no sex differences in standing height and upper-arm muscle circumference. In some age groups, there was a weak but significant sexual dimorphism in body weight and sitting height. The greatest and most persistent dimorphism was found in head circumference, and in triceps and subscapular skinfolds. In all except two age groups, head circumference in males was significantly greater than in females. The other dimorphic variables (body weight, sitting height, and triceps and subscapular skinfolds) showed the opposite relationship. Essentially, females showed increments in subcutaneous fat, while reduced growth in muscle and bone was evident in males. The hypothesis of “better female canalization” can explain the altered dimorphic pattern found in the malnourished Villa IAPI population. © 1993 Wiley-Liss, Inc.