Gerardo Rubén Cueto

Prevalence of infection with hantavirus in rodent populations of central Argentina

We studied hantavirus seroprevalence and virus variability in rodent populations in Diego Gaynor, northwest of Buenos Aires province, Argentina. Rodent samplings were conducted in railroads and cropfield borders in March and July 1999, September and December 2000, and March 2001. Antibody detection was performed by an enzyme link immunosorbent assay (ELISA), using the recombinant nucleoprotein of Andes (AND) virus as antigen. Tissue samples were taken from positive antibody individuals in order to confirm the presence of hantavirus genomic material and to identify virus genotypes. Akodon azarae was the most abundant species, followed by Oligoryzomys flavescens, while Calomys laucha and C. musculinus were rarely caught. We found a rate of seroprevalence of 9.3% for a total sample of 291 A. azarae and 13.5% for 37 O. flavescens. After molecular analyses of hantavirus, we confirmed the presence of hantavirus genomic material in 16 individuals with ELISA (+) results and two individuals with ELISA (-). Four amplimers for each species were sequenced and compared to the corresponding sequences of representative hantaviruses. We identified the AND Cent Lec from three O. flavescens, and the Pergamino virus from four A. azarae and from one O. flavescens. A. azarae males had higher seroprevalence than females, and heavier individuals showed higher seroprevalence than lighter ones. We did not find seroprevalence differences according to sex in O. flavescens, although this result may have been produced by the low sample size. The lowest seroprevalence was found in a period of high rodent density, when juveniles prevailed in the population. We found higher seroprevalences than those detected in previous studies for other localities of central Argentina where cases of hantavirus pulmonary syndrome (HPS) have been reported. The presence of AND Cent Lec virus in rodent populations of the study area, which is responsible of HPS cases in central Argentina, suggests that human populations are at risk of HPS disease, although there were not reported cases of this disease until today.

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.

Commensal Rodents in the City of Buenos Aires: A Temporal, Spatial, and Environmental Analysis at the Whole City Level

Commensal rodents are some of the main vertebrate pests in urban areas; however, knowledge about factors that favor them at large scales is scarce. We studied spatial and temporal variations in rodent infestation levels at the whole city scale using the complaints of rodent sightings and questionnaire surveys to city neighbors. Demographic, socio-economic, and environmental characteristics handled with a geographic information system were evaluated as possible indicators of rodent infestation. The number of rodent sightings was lower in months with low mean temperature with two months time lag and higher in areas with high number of meat and metal industries. Rodent infestation estimated by the questionnaire survey showed spatial autocorrelation defining large areas with similar infestation levels. It decreased when the apartment density increased, while increased when the proportion of area occupied by shantytowns, the density of meat industries, and the proportion of area occupied by moderate urban development increased. Rodent control programs at the whole city level would have better results if public health pest agencies and/or governments will focus the efforts on areas with more precarious conditions as well as the industrial areas in the cold season when have lower rodent abundances.

Effects of regional context and landscape composition on diversity and composition of small rodent assemblages in Argentinian temperate grasslands and wetlands

Abstract This study aims to describe landscape evolution in two contiguous ecoregions with different land use intensity, to assess changes in small mammal assemblages. Rodent remains in pellet samples from barn owls were used to estimate the attributes of rodent assemblages. Two major biomes were considered in this study, a mosaic of wetlands (Delta and Paraná Islands ecoregion) and a mosaic of grasslands and cultivated fields (Pampa ecoregion). Environmental characterization was based on the analysis of satellite images and weather data. Fourteen rodent species in 28 sampling sites were identified, totaling 7645 prey items. Linear combinations of variables that characterized the landscape explained 66.6% of variation in the composition of rodent assemblages. A positive linear relationship between rodent diversity and the number of different patches was found in the Pampa. Our results suggest that landscape disturbances caused by agricultural intensification favor the increase of generalist and competitively subordinated species. In turn, changes in rodent diversity at the Paraná Delta were negatively associated with the percentage of water-covered area and the number of patches. The hydrological regime of this ecoregion acts as a filter for species establishment, restricting the richness of the rodent assemblages.

Diseases of Capybara

Disease control is an important part of wildlife management both in the wild and in captivity (Caughley and Sinclair 1994). Capybaras, Hydrochoerus hydrochaeris, carry a wide range of parasites and other diseases including hemoparasites and gut parasites (Mones and Martinez 1982), but appear to be largely resistant to their effects and show few signs of ill-health (Emilio A. Herrera, personal communication). In this chapter, I describe the diseases that affect capybaras in the wild and in captivity. The information presented here is based on a decade of experience in capybara breeding and husbandry, based initially at the “Modulo Experimental de Cria de Carpinchos,” located in the Experimental Station of the Parana Delta (Province of Buenos Aires, Argentina; Fig. 9.1), and later on commercial breeding farms, with additional information obtained from the literature.

A multiarray mapping method to minimize morbidity from thermocoagulation as treatment of refractory trigeminal neuralgia.

BACKGROUND Conventional percutaneous thermocoagulation of postgasserian fibers has shown high success rates, with significant residual morbidity. METHODS This communication summarizes conclusions of multiple publications on our computerized mapping method and technique, and presents new data on short- and long-term results on trigeminal pain, including an actuarial analysis, complications. RESULTS In TTN, 97.4% of 75 procedures produced initial pain relief without medication. In all, 84.7% of appropriate verbal responses were achieved by proper location of the needle at the chosen target, requiring an average of 1.45 tracts per procedure. Needle tip was located between 1 and 15 mm below the sellar floor in 97.0% of procedures and in an angle of 40 degrees to 80 degrees regarding the clivus profile projection in 99.1%. A 93% reduction of corneal analgesia and a 100% suppression of major dysesthesias and cranial nerve palsies were found. CONCLUSION We have shown a significant reduction of morbidity from percutaneous thermocoagulation of postgasserian fibers with similar short- and long-term results as those shown in 11 recently selected series. Strict adherence to all details of our new method and technique is essential. Future multiinstitutional studies are needed to confirm and enrich this small series.

Reducing unnecessary morbidity from percutaneous thermocoagulation in the treatment of trigeminal neuralgia—Part C: a starting point for a somatotopic map of the human gasserian ganglion

Abstract Objectives: An original method and technique has been designed to reduce the significant morbidity associated with techniques currently used for percutaneous thermocoagulation in the treatment of trigeminal neuralgia. The current report deals with the mathematical and biostatistical analysis of verbal responses gathered using such a method in an attempt, as a starting point, to establish the somatotopic organization of the human gasserian ganglion. Method: A correspondence analysis was used to validate verbal responses. These were ordered in three 34 × 34 matrices, according the initial sequence of 34 subsegments of the face, which was based on the operative experience of one of the authors. After using a filter for the consistency of responses, and a maximum threshold below 0.5 V, 967 responses from 99 patients were selected for analysis. The frequencies obtained from each subsegment were compared, using all the possible pairwise combinations of the subsegments of the face, and the sequences were ordered using the least contradictory criterion. Results: The incidence of each verbal response within each trigeminal division was analysed, resulting in a proposal of a sequence of 20 subsegments of the gasserian ganglion, listed from the depth to the surface. Discussion: From the strict clinical point of view, the somatotopic map of each individual is invariant and easily analysed over long time periods. Its precise knowledge is critical for inducing smaller, properly placed lesions, in order to avoid unnecessary morbidity from percutaneous thermocoagulation in the treatment of trigeminal neuralgia. The proposed sequence of the gasserian somatotopic organization will be hopefully a useful guide for those interested in trigeminal physiological organization as well as for the therapeutic exploration of gasserian trigeminal fibers.

Interacciones entre sitio, plaga y una enfermedad del fuste en una plantación de Populus deltoides cv. Catfish-2 en el bajo delta del Río Paraná (Argentina)

El objetivo del trabajo fue estudiar la relacion entre la calidad de sitio de plantacion de alamos con los danos causados por el «Taladro de los Forestales» (Platypus mutatus Chapuis) y la relacion con una enfermedad del fuste (cancrosis). El estudio se llevo a cabo en 2 ha de una plantacion de Populus deltoides cv Catfish-2, uno de los clones de alamos mas plantados en el Delta Bonaerense. La plantacion de 12 anos de edad estaba ubicada en el Bajo Delta del Rio Parana (Argentina). Nosotros detectamos una relacion directa entre la calidad del sitio, la presencia de la plaga y de cancros en el fuste. Los alamos de mayor diametro y altura presentaron un mayor ataque por taladro y una mayor cantidad de orificios activos y rajaduras a la altura de las galerias producidas por Platypus mutatus Chapuis, mientras que los alamos de menor crecimiento fueron los mas infectados por cancros en sus fustes. El porcentaje de plantas afectadas por taladro e infectadas por cancrosis fue significativamente mayor en el sitio mas productivo y mas alto del terreno (albardon endicado). En cambio, los sitios bajos (banados endicados) mostraron menores valores de crecimiento y productividad de alamos, menor cantidad de orificios activos, menor porcentaje de plantas quebradas por el viento a la altura de las galerias generadas por taladros y menor numero de plantas con cancros en el fuste.

Partial genetic characterization of Seoul hantavirus in rats from Buenos Aires City, Argentina, and generation of a Seoul recombinant nucleoprotein antigen

Hemorrhagic fever with renal syndrome (HFRS) is a severe infectious disease characterized by fever, hemorrhage, renal impairment, and thrombocytopenia. At least seven hantaviruses cause HFRS: Hantaan, Seoul (SEOV) (distributed worldwide), Dobrava/Belgrade, Saaremaa, Amur, Thailand and Puumala. To investigate the epidemiology of HFRS and virus transmission in Argentina, we constructed a prokaryotic plasmid encoding the SEOV rNP, of 430 amino acids. After expression, the rNP was tested as an antigen for use in an enzyme-linked immunosorbent assay for infection diagnosis. To determine the current level of virus transmission in wild brown rats or Norway rats (Rattus norvegicus) captured in Buenos Aires City, Argentina, we tested tissues from rats that were determined to be serologically positive for the SEOV, and the viral genome were detected by RT-PCR using specific primers for two fragments of M segment-encoding Gn and Gc proteins. The viral genome was detected in 11 of 21 seropositive rats (52.4%) captured in two parklands. Sequence analysis of a 333-nt region of the Gc-encoding M segment revealed 97% and 96% identity with strains of SEOV from Baltimore and Brazil, respectively. Our genetic data confirm a very low diversity among SEOV virus strains.

Caracterización genética parcial del hantavirus Seoul en ratas provenientes de Buenos Aires, Argentina, y generación de un antígeno a partir de la nucleoproteína recombinante del virus Seoul

Hemorrhagic fever with renal syndrome (HFRS) is a severe infectious disease characterized by fever, hemorrhage, renal impairment, and thrombocytopenia. At least seven hantaviruses cause HFRS: Hantaan, Seoul (SEOV) (distributed worldwide), Dobrava/Belgrade, Saaremaa, Amur, Thailand and Puumala. To investigate the epidemiology of HFRS and virus transmission in Argentina, we constructed a prokaryotic plasmid encoding the SEOV rNP, of 430 amino acids. After expression, the rNP was tested as an antigen for use in an enzyme-linked immunosorbent assay for infection diagnosis. To determine the current level of virus transmission in wild brown rats or Norway rats (Rattus norvegicus) captured in Buenos Aires City, Argentina, we tested tissues from rats that were determined to be serologically positive for the SEOV, and the viral genome were detected by RT-PCR using specific primers for two fragments of M segment-encoding Gn and Gc proteins. The viral genome was detected in 11 of 21 seropositive rats (52.4%) captured in two parklands. Sequence analysis of a 333-nt region of the Gc-encoding M segment revealed 97% and 96% identity with strains of SEOV from Baltimore and Brazil, respectively. Our genetic data confirm a very low diversity among SEOV virus strains.