ABSTRACT
The aims of this study were to characterise the ground-level larval habitats of the mosquito Culex quinquefasciatus, to determine the relationships between habitat characteristics and larval abundance and to examine seasonal larval-stage variations in Córdoba city. Every two weeks for two years, 15 larval habitats (natural and artificial water bodies, including shallow wells, drains, retention ponds, canals and ditches) were visited and sampled for larval mosquitoes. Data regarding the water depth, temperature and pH, permanence, the presence of aquatic vegetation and the density of collected mosquito larvae were recorded. Data on the average air temperatures and accumulated precipitation during the 15 days prior to each sampling date were also obtained. Cx. quinquefasciatus larvae were collected throughout the study period and were generally most abundant in the summer season. Generalised linear mixed models indicated the average air temperature and presence of dicotyledonous aquatic vegetation as variables that served as important predictors of larval densities. Additionally, permanent breeding sites supported high larval densities. In Córdoba city and possibly in other highly populated cities at the same latitude with the same environmental conditions, control programs should focus on permanent larval habitats with aquatic vegetation during the early spring, when the Cx. quinquefasciatus population begins to increase.
Subject(s)
Animals , Animal Distribution/physiology , Culex/growth & development , Ecosystem , Seasons , Magnoliopsida , Argentina , Aquatic Organisms/physiology , Larva , Meteorological Concepts , Mosquito Control/methods , Population Growth , Water/parasitologyABSTRACT
INTRODUCTION: The aim of the present study was to analyze the larvicidal activity of different crude extracts of Larrea cuneifolia and its most abundant lignan, nordihydroguaiaretic acid (NDGA), against Culex quinquefasciatus. METHODS: Chloroform, methanol, and aqueous extracts from L. cuneifolia and NDGA were tested against larvae of Cx. quinquefasciatus under laboratory conditions. RESULTS: The chloroform extract showed the highest larvicidal effect, with an estimated LC50 of 0.062 mg/ml. NDGA also demonstrated significant larvicidal activity with an estimated LC50 of 0.092 mg/ml. CONCLUSIONS: These results indicate that the chloroform extract of L. cuneifolia and NDGA are promising insecticides of botanical origin that could be useful for controlling Cx. quinquefasciatus.
Subject(s)
Animals , Culex/drug effects , Insect Vectors/drug effects , Insecticides/pharmacology , Larrea/chemistry , Masoprocol/pharmacology , Plant Extracts/pharmacology , Insecticides/isolation & purification , Larva/drug effects , Masoprocol/isolation & purificationABSTRACT
The presence of Aedes aegypti is reported beyond its current limit of distribution in Argentina, in the city of Neuquén, Neuquén Province. Ovitraps were placed to collect Ae. aegypti eggs between December 2009 and April 2010. The geographical distribution of Culex eduardoi, Psorophora ciliata and Ps. cingulata is extended with new records from two provinces.
Relata-se a presença de Aedes aegypti ao sul de seu limite atual de distribuição na Argentina, na cidade de Neuquén, província de Neuquén. Ovitrampas foram instaladas de dezembro/2009 a abril/2010. A distribuição geográfica de Culex eduardoi, Psorophora ciliata e Ps. cingulata aumenta, incluindo novos registros para duas províncias.
Se reporta la presencia de Aedes aegypti al sur de su límite actual de distribución en Argentina, en la ciudad de Neuquén, provincia de Neuquén. Huevos de esta especie fueron colectados mediante el uso de ovitrampas que fueron colocadas de diciembre/2009 a abril/2010. La distribución geográfica de Culex eduardoi, Psorophora ciliata y Ps. cingulata se amplía, incluyendo nuevos registros para dos provincias.
Subject(s)
Animals , Female , Male , Culicidae/classification , Argentina/epidemiology , Culicidae/physiology , Dengue/epidemiology , Larva/classification , Larva/physiologyABSTRACT
El objetivo del estudio fue determinar los horarios de máxima actividad de oviposición de Aedes aegypti en la ciudad de Orán (noroeste argentino). Se realizaron muestreos quincenales entre noviembre de 2006 y febrero de 2007 (primavera-verano). La ciudad fue dividida en tres zonas (norte, centro, sur), donde fueron seleccionadas al azar las viviendas para colocar dos ovitrampas en el exterior de las mismas. Las ovitrampas fueron reemplazadas cada cuatro horas, desde la mañana (8h) hasta el atardecer (20h). Se registró la mayor cantidad de huevos entre las 16 y 20 h (81 por ciento). Estos datos aportan al conocimiento del vector y, por lo tanto, de la posibilidad de control, pudiendo realizarse las fumigaciones en la franja horaria con mayor actividad de oviposición.
The study aimed to determinate the maximum daily peak of Aedes aegypti oviposition in the city of Oran, northwestern Argentina. Biweekly samplings were taken between November 2006 and February 2007 (spring-summer). The city was divided into three areas (north, center, and south) and households were randomly selected. Two ovitraps were placed outdoors in the selected houses. Ovitraps were replaced every four hours, from morning (8 a.m.) to late afternoon (8 p.m.). The largest number of eggs was recorded between 4 p.m. and 8 p.m. (81 percent). These findings enhance our understanding of the vector and thus its control such as spraying during the hours of peak oviposition activity.
O objetivo do estudo foi determinar os horários de máxima atividade de oviposição de Aedes aegypti na cidade de Orán (noroeste argentino). Foram realizadas coletas quinzenais, entre novembro de 2006 e fevereiro de 2007 (primavera-verão). A cidade foi dividida em três zonas (norte, centro, sul); foram escolhidos aleatoriamente dez domicílios em cada zona e duas ovitrampas foram instaladas no exterior de cada domicílio. As ovitrampas eram trocadas a cada quatro horas, cobrindo desde a manhã (8h) até a noite (20h). A maior quantidade de ovos (81 por cento) foi registrada entre as 16h e 20h. Esses dados aportam conhecimento do vetor e, portanto, a seu controle, como, por exemplo, realizar a fumegação na faixa horária de maior atividade de oviposição.
Subject(s)
Animals , Female , Aedes , Insect Vectors , Oviposition , Argentina , Dengue , Seasons , Time FactorsABSTRACT
To classify mosquito species based on common features of their habitats, samples were obtained fortnightly between June 2001-October 2003 in the subtropical province of Chaco, Argentina. Data on the type of larval habitat, nature of the habitat (artificial or natural), size, depth, location related to sunlight, distance to the neighbouring houses, type of substrate, organic material, vegetation and algae type and their presence were collected. Data on the permanence, temperature, pH, turbidity, colour, odour and movement of the larval habitat's water were also collected. From the cluster analysis, three groups of species associated by their degree of habitat similarity were obtained and are listed below. Group 1 consisted of Aedes aegypti. Group 2 consisted of Culex imitator, Culex davisi, Wyeomyia muehlensi and Toxorhynchites haemorrhoidalis separatus. Within group 3, two subgroups are distinguished: A (Psorophora ferox, Psorophora cyanescens, Psorophora varinervis, Psorophora confinnis, Psorophora cingulata, Ochlerotatus hastatus-oligopistus, Ochlerotatus serratus, Ochlerotatus scapularis, Culex intrincatus, Culex quinquefasciatus, Culex pilosus, Ochlerotatus albifasciatus, Culex bidens) and B (Culex maxi, Culex eduardoi, Culex chidesteri, Uranotaenia lowii, Uranotaenia pulcherrima, Anopheles neomaculipalpus, Anopheles triannulatus, Anopheles albitarsis, Uranotaenia apicalis, Mansonia humeralis and Aedeomyia squamipennis). Principal component analysis indicates that the size of the larval habitats and the presence of aquatic vegetation are the main characteristics that explain the variation among different species. In contrast, water permanence is second in importance. Water temperature, pH and the type of larval habitat are less important in explaining the clustering of species.
Subject(s)
Animals , Culicidae , Ecosystem , Argentina , Culicidae/physiology , Larva/physiology , Seasons , Tropical ClimateABSTRACT
BACKGROUND: Approximately 80 per cent of Argentine children have pediculosis, making it imperious to detect the defects in the prevention and control actions for this parasitosis. OBJECTIVES: To study the infestation level by P. h. capitis, its temporal variation, and the association between infestation and host characteristics. MATERIALS AND METHODS: A monthly census in children of 6-8 years old from 2 primary schools (state and private) was carried out, recording the parasite stages found, children characteristics (sex, colour and length of hair), and infestation level. Data were analysed by means of contingency tables, difference of proportions, quotient of chances, and rank correlation coefficient. The independence of variables was analysed by c' test. RESULTS: The prevalence and chances of becoming infested were higher at the state school, where also all infestation levels were recorded, which did not occur at the private institute. The frequency of children infested was significantly lower when they had short hair. The correlation among infestation degree and hair length (short-long) was only significant for boys. Pediculosis cases were recorded at the beginning of the school year in both educative institutions, which demonstrated that infestation was acquired not only at school but also at home. CONCLUSIONS: Pediculosis is a social problems and the whole community must participate in preventive and control actions, for which sanitary education is essential, and the myth that the school is the only place of contagion must be eradicated.
Subject(s)
Humans , Male , Female , Child , Lice Infestations , Pediculus , Scalp Dermatoses , Argentina , Prevalence , Risk Factors , Scalp Dermatoses , Seasons , Severity of Illness Index , Socioeconomic FactorsABSTRACT
Aedes albifasciatus is an important common mosquito in Central Argentina. Its a confirmed vector of the Western Equine Encephalitis and is responsible for loss of milk production in dairy cattle during peak populations. This paper reports the flight activity pattern of Ae. albifasciatus for different seasons, in the southern coast of the Mar Chiquita Lake (Central Argentina). Data were collected by sampling two sites between 1992 and 1993 with CDC traps and human-bait captures. Adult mosquito population density, estimated by CDC trapping and human-bait, were highly correlated. However, when compared to other species, the proportion of Ae. albifasciatus was higher in human-bait collections. Adult female populations were active only when temperature were higher than 6§C. Two daily biting peaks were observed (dusk and dawn) during the spring, summer and autumn, and only one peak during winter (around 15:00 pm). Adult abundance was significantly correlated (R²= 0.71; p<0.01) with temperature and illumination.
Subject(s)
Animals , Behavior, Animal , Culicidae , Disease Vectors , Encephalomyelitis, Equine , Lighting , TemperatureABSTRACT
Aedes albifasciatus is a flood water mosquito ocurring in the southern countries of South America. It is a competent vector of the Western Equine Encephalitis (WEE) and causes important losses on milk and beef production in central Argentina. Field work was carried out from December 1990 to March 1993, on a monthly basis during the dry season and biweekly during the rainy season. Larvae were collected using the 'dipping' technique and females with CDC traps baited with CO2. Field collected larvae were used to build laboratory cohorts, from which basic population parameters were estimated. Eggs survived up to six months on dry soil, although there was a linear decrease of viability with time. At 23§C, larval development time was around nine days, and all adults emerged within one week. The estimation of larval development in the laboratory seems to be very near the development on the field, as larvae have been collected on average eight days after a rainfall. Egg to adult survival was 83 por cento, with the highest mortality on fourth larval instar (6 por cento). In the laboratory studies, sex proportion among the adults was 1:1, females lived longer than males (median 13 and five days, respectively), and adult survival pattern showed a constant number of individuals dying per unit time. Field collected females layed an average of 84 eggs per batch, and completing up to five gonotrophic cycles, suggesting an estimated survival of up to 35-50 days.