ABSTRACT Perennial ryegrass is one of the most important food sources in animal production. However, several pests affect this crop, and one of the primary control strategies is the symbiotic relationships between ryegrass endophyte fungi. This fungus produces alkaloids that exhibit toxic activity against arthropods. Furthermore, the effect of fungi may extend to higher trophic levels, including predators (spiders and/or insects), decreasing their abundance and diversity. Given the importance of spiders and insects as predators, whether the symbiotic interaction between perennial ryegrass and endophyte fungus reduces the abundance and diversity of predators pose an important question. To address this question, natural enemies in perennial ryegrass were collected and analyzed over a year, and the percentage of endophyte fungus was evaluated by the presence of hyphae from two ryegrass cultivars, Jumbo (E-) and Alto AR1 (E+). We observed an 80% endophyte infection rate for (E+) and 0% for (E-). Moreover, 222 individual spiders corresponding to 10 families were identified in both perennial ryegrasses, including 209 individuals for (E-) and 13 for (E+). The most abundant spider family was Lycosidae, representing 71.17% of the total spiders. In addition, 65 insects were collected, corresponding to 6 families, with Carabidae being the most abundant. Furthermore, the Simpson index indicated the dominance of the family Lycosidae. Overall, spider and insect abundance and diversity were reduced in (E+), suggesting a negative effect of the endophyte on predator populations.

OBJECTIVE: To confirm the occurrence of an outbreak of viral meningitis in 1996 in the province of Tucuman, Argentina, and to study the outbreak's epidemiological characteristics. METHODS: We analyzed information from the National Epidemiological Surveillance System of the Ministry of Health (MOH) of Argentina for 1994-1998 that had been provided by the MOH's Bureau of Epidemiology. We calculated incidence rates using population estimates for the years 1994-1998 developed by the National Statistics and Census Institute, based on the 1991 census. We studied frequencies with contingency tables, using the chi-square method with Yates' correction. Results were considered significant when P < 0.05. RESULTS: We confirmed the occurrence of an outbreak of 189 cases of viral meningitis between 11 February and 18 May 1996. The incidence of cases in Tucuman province increased between 1995 and 1996, from 0.5 to 19.3 cases per 100 000 person-years. That 1996 rate in Tucuman was significantly higher than what was seen in the rest of the country (2.8 cases per 100 000 person-years). Of the 189 cases, 142 of them (75.1%) occurred in children less than 9 years old. Out of 111 samples studied, 65 of them (58.6%) were enterovirus-positive. Through reverse transcription-nested polymerase chain reaction, enteroviruses were found in 66.3% (53/80) of the cases studied by this method, versus in only 29.6% (24/81) of the cases studied through viral isolation. In the 22 samples that were serotyped, echovirus type 4 was identified in 15 of them (68%): 5 by isolation, 3 by sequencing, and 7 by both methods. During the Tucuman outbreak, at least 56% of the cases were hospitalized. This viral meningitis outbreak shows the capacity of enteroviruses to spread and cause disease. CONCLUSIONS: The use of molecular methods makes it possible to rapidly diagnose the etiological virus and to better control an outbreak. Recognizing this outbreak in Tucuman sooner could have averted the majority of the hospitalizations and the indiscriminate use of antibiotics.

OBJETIVO: Confirmar la existencia de un brote de meningitis viral en 1996 en la provincia de Tucumán, Argentina, y estudiar sus características epidemiológicas. MÉTODOS: Se analizó información obtenida del Sistema Nacional de Vigilancia Epidemiológica (SINAVE) del Ministerio de Salud de Argentina para el período de 1994-1998, la cual fue provista por la Dirección de Epidemiología de dicho ministerio. Para el cálculo de incidencias se usaron estimaciones poblacionales para los años 1994-1998 realizadas por el Instituto Nacional de Estadística y Censos (INDEC) sobre la base del censo de 1991. El estudio de frecuencias se realizó mediante el análisis de tablas de contingencia de doble entrada, según el método de ji cuadrado con la corrección de Yates. Se consideró significativo el resultado cuando P < 0,05. RESULTADOS: Se confirmó la presencia de un brote de 189 casos entre el 11 de febrero y el 18 de mayo de 1996. La incidencia de casos en la provincia mostró un aumento entre 1995 y 1996 (de 0,5 a 19,3 casos por 100000 años-persona) y dicha incidencia fue significativamenrte mayor que la observada en el resto del país (19,3 frente a 2,8 casos por 100000 años-persona). El 75,1% de los casos ocurrió en niños menores de 9 años (142/189). Se detectó la presencia de Enterovirus (EV) en 65 de las 111 muestras estudiadas (58,6%). Mediante la reacción en cadena de la polimerasa (RCP) anidada con transcripción inversa se logró detectar EV en 66,3% (53/80) de los casos estudiados por este método, en comparación con solo 29,6% (24/81) de los estudiados mediante aislamiento viral. Se identificó echovirus tipo 4 en 15 (68%) en las 22 muestras tipificadas (5 por aislamiento, 3 por secuenciación y 7 por ambos métodos). Este brote demuestra la capacidad de los EV para diseminarse y producir enfermedad en la población. Durante el brote, por lo menos 56% de los casos fueron hospitalizados. CONCLUSIONES: El uso de métodos moleculares permitió el diagnóstico rápido del virus etiológico y posibilitó un mejor control del brote. El reconocimiento temprano de este podría haber evitado la mayoría de las hospitalizaciones y el uso indiscriminado de antibióticos.