AEDES-TRISERIATUS AND LA CROSSE VIRUS - LACK OF INFECTION IN EGGS OF THE 1ST OVARIAN CYCLE FOLLOWING ORAL INFECTION OF FEMALES

La Crosse (LAC) virus filial infection rates were 0% for 279 1st ovarian cycle larvae, 43% for 380 2nd ovarian cycle larvae and 58% for 363 3rd ovarian cycle larvae from orally infected mosquitoes representing 14 Wisconsin [USA] populations of A. triseriatus [the vector]. LAC virus was not detected in 72 pools representing 2250 1st ovarian cycle larvae, while 35 pools and 16 pools each containing 30 2nd and 3rd ovarian cycle larvae, respectively, were all positive for LAC virus. Similar results were obtained when the extrinsic incubation period temperature was 25, 27 or 29.degree. C, or variable (17, 23 and 29.degree. C for 8 h each). LAC virus was not detected in 240 2nd ovarian cycle larvae in which the blood meal for the 1st ovarian cycle was non infectious. Infection was not detected in 337 1st ovarian cycle larvae from female mosquitoes that were injected intrathoracically with LAC virus concomitantly with receiving a non infectious bloodmeal. After an extrinsic incubation temperature of 25.degree. C, LAC virus was discovered in dissected mosquito ovarian tissue 7 days postfeeding on an infectious blood meal. The epidemiological implications of these findings are discussed.