Development and survival of immature Aedes albopictus and Aedes triseriatus (Diptera: Culicidae) in the laboratory: effects of density, food, and competition on response to temperature.

Effects of food, density, and heterospecific interactions on temperature-dependent development of Aedes albopictus (Skuse) and Aedes triseriatus (Say) larvae and pupae were described using a degree-day model. Under all conditions, the predicted number of degree-days (DD(T0)) to complete larval development was less, and the threshold temperature (T0) for initiation of larval development was higher for Ae. albopictus than for Ae. triseriatus. The DD(T0) for both species was food and density dependent. However, the per capita food ration appeared to exert a greater influence on the developmental times of Ae. triseriatus immatures, whereas for Ae. albopictus effects of density were not completely eliminated by an increase in the per capita food ration. The presence of heterospecific larvae did not prolong the DD(T0) of either species. At the low food ration, DD(T0) for both species were significantly greater under conspecific conditions. The DD(T0) for Ae. triseriatus increased directly as the proportion of conspecific larvae increased. However, when a higher per capita food ration was provided, conspecific effects on DD(T0) were mitigated. For Ae. albopictus, estimated DD(T0) values for larvae reared in pure culture were significantly higher than when heterospecific larvae were present, regardless of the per capita amount of food provided. Survivorship of immatures was density and food-dependent for both species. Ae. albopictus exhibited higher immature survivorship under all conditions relative to Ae. triseriatus. For both species, survival probabilities were lowest under conditions of high density and low food. Addition of food improved survival for both species. The presence of heterospecific larvae exerted a differential effect on the survivorship response of Ae. albopictus immatures to temperature. Lowest probability of survival for Ae. albopictus was occurred at low temperature when the proportion of heterospecific larvae in containers was the highest. In contrast, at high temperatures, survivorship of immatures improved, but was lowest for pure species cultures. For Ae. triseriatus, survivorship of immatures was consistently lower for pure species cultures regardless of the temperature. Standing crop production of adults of both species was primarily food rather that density-dependent. Under field conditions, Ae. triseriatus were predicted to initiate development sooner and exhibit faster population growth early in the season than Ae. albopictus. However, because of the shorter DD(T0), Ae. albopictus population growth was predicted to surpass that of Ae. triseriatus populations later in the season. Based on optimal DD(T0) values from laboratory experiments, spring emergence dates of Ae. triseriatus females in western North Carolina for 1989 and 1990 were predicted from accumulated degree-days calculated from local air temperature records. Predicted emergence dates were congruent with results of a previous survey for the same locality, indicating that accumulated degree-days can be used to accurately predict the seasonal occurrence of Ae. triseriatus. The utility of the degree-day approach in predicting the phenology of Ae. albopictus remains to be established.

Mosquito fauna in water-holding containers with emphasis on dengue vectors (Diptera: Culicidae) in Chungho, Taipei County, Taiwan.

A survey was conducted to characterize the mosquito fauna in water-holding containers in residential and open areas with emphasis on Aedes albopictus Skuse, and to determine the prevalence of mosquito-positive containers to obtain background information for a source reduction program. Seven container-inhabiting mosquito species were collected in residential areas, including Ae. albopictus, Culex quinquefasciatus Say, C. pallidothorax Theobald, C. neomimulus Lien, C. bicornutus Theobald, C. fuscanus Wiedemann, and Tripteroides aranoides Theobald. Ae. albopictus was the most abundant species and was collected in 18.49% of the containers examined. Other mosquito species were found in 0.02-0.16% of the total numbers of water containers checked. Of the positive water containers, 97.33% contained Ae. albopictus larvae. Sixteen species were collected in open areas away from residential sites. Ae. albopictus was most abundant and was present in 24.50% of the total number of containers examined. C. bicornutus, C. quinquefasciatus, and C. pallidothorax were present in 2.17, 1.48, and 1.08%, respectively. Ae. albopictus larvae were found in 74.78% of the mosquito-positive water containers. The mean Breteau index (+/- SE) in 1997 (17.22 +/- 1.59 mosquito-positive containers per 100 premises) per village in residential areas was not significantly higher than the index in 1996 (16.86 +/- 1.33). The frequency of occurrence of Ae. albopictus in different containers is presented. A greater preference for containers in outdoor habitats was found. The ratio of the total number of containers indoors and outdoors per premises was 1.15:1.00, whereas the ratio of mosquito-positive containers indoors and outdoors was 1.00:1.83. Most indoor breeding containers (86.11%) in residential areas were used for planting purposes and for recreation (12.50%). The number of breeding containers in residential areas that were classified as trash increased from 0.35% indoor to 39.03% outdoor, whereas the number used for planting reduced to 34.95%. Most breeding containers (63.02%) in open areas were trash; natural containers (11.86%) were the 2nd most common breeding site followed by temporarily unused (8.84%), watering (6.98%), and planting containers (5.81%).

[The density and larval habitats of dengue vectors in Chungho city].

A survey was conducted to understand larval habitats and density of dengue vectors in Chungho city during the period of August 12 to September 13, 1996. Most villages (41 in the total of 93) were found to have the density figures of three for Aedes albopictus Skuse. The second common density figures were found at 2nd and 4th levels. The most common breeding containers found were less than 5 cm in water depth and less than 100 cm2 in water area. The number of breeding containers reduced when the water depth and size increased. The common breeding containers in villages were flower vases (30%) and water buckets (18%). In the mountains, water buckets (34%) and kitchen tools (11%) were common. In parks, water buckets (29%) and tires (15%) were commonly found. In cemeteries, the common breeding containers were flower vases (57%) and earthenware pots (17%). The average (2.05 containers per man-hour) of positive water containers in the mountains was significantly higher than that in parks (0.62). However, the average in cemeteries (1.29) was not significantly different from those collected in mountains and parks.

Inhibition effect of shengma-gegen-tang on measles virus in Vero cells and human peripheral blood mononuclear cells.

Shengma-Gegen-Tang has long been used against measles virus in human peripheral blood mononuclear cells (PBMC) as well as in Vero cells. One hundred micrograms/ml Shengma-Gegen-Tang in PBMC displays significant anti-measles activity, whereas the same concentration in Vero cells does not. After eight days of infection, the release of virus is significantly suppressed by Shengma-Gegen-Tang in the case of PBMC. In addition, Shengma-Gegen-Tang has a selective stimulation to the secretion of cytokine TNF-alpha in PBMC. Time kinetic analysis indicated that the stimulation of secretion was rapid and could be detected only 2 hrs following the treatment of the PBMC. It rose to an optimal level in 8-12 hrs. These findings suggest that the magnification of anti-measles virus activity of this agent is lymphocyte dependent and may well be mediated by TNF-alpha.