Trials with portable screen rooms modified for use as animal-baited net traps for mosquito collection.

Trials in Larimer County, Colorado during July and August 1984, with recreational screen rooms modified as large animal-baited mosquito traps are described. The two units tested are free-standing, portable and require no external support. In all-night trials, 462.5 mosquitoes/trap night were captured with horse bait compared with 367/trap night with CDC light traps. In 2-hour evening comparisons, mosquitoes collected per trapping period totalled 416 for horse-bait traps, 132 for light traps, and 93 for human-bait traps. Animal-baited screen rooms offer an alternative to existing methods for mosquito surveillance.

Temperature-induced morphological change in Culex pipiens.

The effect of temperature on Culex pipiens pipiens, Cx. p. quinquefasciatus, and reciprocal hybrids of the two was investigated by monitoring the DV/D ratios of these stocks maintained at 15.6 degrees C and 23.9 degrees C over 10 generations. Little variation occurred in mean values of the parental subspecies at either temperature. At 23.9 degrees C, the mean ratios for both hybrid lines rose from an intermediate value to a level well above the accepted minimum for Cx. p. quinquefasciatus (0.4), and the proportion of individuals identifiable as that subspecies increased 16-fold. At 15.6 degrees C, hybrid mean DV/D ratios decreased to or below the pipiens maximum value (0.2), and the proportion of pipiens individuals increased 4 to 5 times. The need to monitor closely the status of Cx. pipiens hybrid colonies is evident.

Domestic triatomines (Reduviidae) and insect trypanosome infections in El Salvador, C.A.

Twenty-five Salvadoran communities have been surveyed to learn more about the distribution of Chagas' disease vectors and trypanosome parasites in that country. The results indicate that each of several factors--local variations in housing construction, insecticide applications, geographic elevation, and the vector species involved--can have a critical effect on transmission of the disease agent.

A comparison of individual dissection and mass separation for recovery of Onchocerca larvae from vector black flies.

The effectiveness of a mass separation technique, previously used for the extraction of larvae of lymphatic-dwelling filarial worms from batches of vector mosquitoes, was tested as a means of recovering infective-stage larvae of Onchocerca volvulus from Simulium ochraceum in Guatemala. Blood-engorged flies, collected from 10 infected human attractants, were maintained for 9 days to allow ingested microfilariae to develop to the infective stage. The numbers of Onchocerca larvae recovered after groups of these flies were crushed and washed into tissue culture fluid in Baermann funnels was compared with the numbers obtained by individual dissections of flies fed on the same subjects. The mass separation procedure gave a mean recovery rate of 0.03 larva/fly and detected larvae only in flies which had fed on those subjects with the highest microfilarial skin densities. Dissections yielded 0.50 larva/fly (a 16.7-fold increase) and detected larvae in flies collected from all test subjects. The explanation for the ineffectiveness of the mass separation technique may lie in the observed sluggishness of infective-stage Onchocerca larvae and a consequent inability to free themselves from the fly fragments in the Baermann funnel.