Miguel Atilio Risso

Mycotoxin T-2 and aflatoxin B1 asimmunosuppressors in mice chronically infected with Toxoplasma gondii

The aim of this study was to determine whether repeated ingestion of mycotoxin T-2 (T2) or aflatoxin B1 (AFL) at low doses could contribute to the activation of toxoplasmosis in experimentally infected mice. Mice were divided into two groups: Control (C) and Infected (I). The cyst-forming Beverley strain of Toxoplasma gondii was used to produce the infection one month before treatment with mycotoxins. Mycotoxins were given intragastrically for a 50-day period. The average weight gain was reduced in the groups treated with mycotoxins. Mice developed specific IgG to T. gondii. Histopathological studies showed severe encephalitis in all groups infected. The number of unruptured and ruptured cysts was established and the severity of the lesions was evaluated, the groups treated with mycotoxins being the most severely affected. Immunohistochemical studies of the brain showed free antigen in tissues surrounding ruptured cysts. It is suggested that low and repeated doses of mycotoxins, necessary to produce a subclinical intoxication, precipitate Toxoplasma cyst rupture and consequently the activation of chronic toxoplasmosis.

Comparison between two methods for diagnosis of trichinellosis: trichinoscopy and artificial digestion

Two direct methods for the diagnosis of trichinellosis were compared: trichinoscopy and artificial digestion. Muscles from 17 wistar rats, orally infected with 500 Trichinella spiralis encysted larvae were examined. From each of the following muscles: diaphragm, tongue, masseters, intercostals, triceps brachialis and cuadriceps femoralis, 648,440 larvae from 1 g samples were recovered. The linear correlation between trichinoscopy and artificial digestion was very high and significant (r = 0.94, p < 0.0001), showing that both methods for the detection of muscular larvae did not differ significantly. In both methods, significant differences were found in the distribution of larvae per gramme of muscle.

COMPARACION DE TECNICAS PARASITOLOGICAS PARA EL EXAMEN DE HECES DE PERRO

Se evaluaron comparativamente las siguientes tecnicas para el examen parasitologico de heces de perro: la tecnica de Sheater modificada (flotacion por la solucion de azucar), la de sulfato de zinc (flotacion por la solucion de esta sal) y la de Ritchie modificada, denominada tambien de formol-eter (sedimentacion con solucion salina formolada y extraccion de grasas por eter). Se detectaron parasitos en 25 de 40 muestras de materia fecal de perros que se examinaron por las tres tecnicas. No hubo diferencias entre las tecnicas de Sheater y sulfato de zinc en la cantidad de detecciones logradas (37 y 38 respectivamente) pero el valor correspondiente a la de formol-eter (16) fue significativamente menor. Las cantidades de huevos de Toxocara canis y Trichuris vulpis (213 y 334 respectivamente) detectadas por Sheater en materia fecal en fresco, fueron significativamente mayores que las correspondientes a sulfato de zinc (44 y 13 respectiva mente). Utilizando materia fecal con formol con huevos de T. vulpis, los resultados fueron similares (Sheater: 61 vs sulfato de zinc: 0). Las cantidades de quistes de Giardia detectadas por formol-eter en materia fecal en fresco y con formol, fueron significativamente mayores que las detectadas por sulfato de zinc (87 y 19 vs 36 y 3, respectivamente). En 180 muestras examinadas la cantidad de detecciones de quistes Giardia sp efectuadas por medio de formol-eter fue significativamente mayor que por Sheater (15 vs 1, respectivamente). La tecnica de Sheater fue mas eficiente que la de sulfato de zinc en la deteccion de huevos de nematodes y la de formol-eter mas eficiente para la deteccion de quistes de Giardia sp. De acuerdo a los resultados obtenidos se recomienda que, salvo indicaciones especiales cada muestra que requiera examen parasitologico sea procesada por las tecnicas de Sheater y de formol-eter

Fibrinonecrotic enteritis of piglets in a commercial farm: a postmortem study of the prevalence and the role of lesion associated agents Isospora suis and Clostridium perfringens

The objectives were to determine the prevalence of fibrinonecrotic enteritis (FNE) on a farrow-to-finish farm of 1,000 sows, to categorize the pathological changes, and to to investigate the lesion associated agents Isospora suis and Clostridium perfringens. Causes of preweaning mortality (PWM) were classified into 8 categories including FNE. Obtained data were evaluated for statistical significance by adjusted Chi-square analysis. Samples of FNE were taken for complementary studies including a PCR technique for genotyping toxin genes of Clostridium perfringens from gut samples fixed in 10% neutral formalin. From 3,153 piglets examined, less than 1% was classified as FNE. FNE prevalence increased progressively from the first to the third week, the last differing statistically from the others. Eighty percent of gut samples with FNE lesions were positive to Isospora suis, when examined by PCR from 9 severe FNE lesions detected 7 positive samples only for a toxin gene, characteristic of C. perfringens type-A.

Assessing the performance of macroinvertebrate metrics in the Challhuaco-Ñireco System (Northern Patagonia, Argentina)

Seven sites were examined in the Challhuaco-Nireco system, located in the reserve of the Nahuel Huapi National Park, however part of the catchment is urbanized, being San Carlos de Bariloche (150,000 inhabitants) placed in the lower part of the basin. Physico-chemical variables were measured and benthic macroinvertebrates were collected during three consecutive years at seven sites from the headwater to the river outlet. Sites near the source of the river were characterised by Plecoptera, Ephemeroptera, Trichoptera and Diptera, whereas sites close to the river mouth were dominated by Diptera, Oligochaeta and Mollusca. Regarding functional feeding groups, collector-gatherers were dominant at all sites and this pattern was consistent among years. Ordination Analysis (RDA) revealed that species assemblages distribution responded to the climatic and topographic gradient (temperature and elevation), but also were associated with variables related to human impact (conductivity, nitrate and phosphate contents). Species assemblages at headwaters were mostly represented by sensitive insects, whereas tolerant taxa such as Tubificidae, Lumbriculidae, Chironomidae and crustacean Aegla sp. were dominant at urbanised sites. Regarding macroinvertebrate metrics employed, total richness, EPT taxa, Shannon diversity index and Biotic Monitoring Patagonian Stream index resulted fairly consistent and evidenced different levels of disturbances at the stream, meaning that this measures are suitable for evaluation of the status of Patagonian mountain streams.

Feline immunodeficiency virus infection: a comparative study of different diagnostic techniques

This study evaluated an indirect immunofluorescence assay (IFA) to detect feline immunodeficiency virus infection (FIV) antibody in a comprehensive epidemiological survey of FIV in Argentina. IFA modified in our laboratory, was compared with two other immunoassays, western blot (WB) and a sandwich immunochromatographic commercial kit (SI), and also with a direct polymerase chain reaction (PCR) method that detects proviral DNA. IFA showed to be a test with high sensitivity and specificity, and could be useful as a diagnostic tool in epidemiological studies. The presence of a low percentage of results with non-specific reactivity in the IFA could be resolved with further testing or use of an alternative method.