Field Evaluation of Indoor Thermal Fog and Ultra-Low Volume Applications For Control of Aedes aegypti in Thailand.

Efficacies of a handheld thermal fogger (Patriot™) and a backpack ultra-low volume (ULV) sprayer (Twister™) with combinations of 2 different adulticides (pyrethrin, deltamethrin) and an insect growth regulator (pyriproxyfen) were field-tested and compared for their impact on reducing indoor Aedes aegypti populations in Thailand. The effectiveness of the indoor space sprays was evaluated by sampling the natural Ae. aegypti population in houses and determining their physiological status, by monitoring mortality of sentinel caged mosquitoes (AFRIMS strain) and by assessing larval mortality in laboratory bioassays using water exposed to the spray. A total of 14,742 Ae. aegypti were collected from Biogents Sentinel traps in this study. The combination of ULD® BP-300 (3% pyrethrin) and NyGuard® (10% pyriproxyfen) sprayed either by the Patriot or Twister significantly reduced some Ae. aegypti populations up to 20 days postspray relative to the control clusters. The addition of pyriproxyfen to the adulticide extended how long household mosquito populations were suppressed. In 2 of the 4 products being compared, the Twister resulted in higher mortality of caged mosquitoes compared with the Patriot. However, neither machine was able to achieve high mortality among Ae. aegypti placed in hidden (protected) cages. The larval bioassay results demonstrated that the Twister ULV provided better adult emergence inhibition than the Patriot (thermal fogger), likely due to larger droplet size.

Evaluation of enemas for exposing Aedes aegypti to suspensions of dengue-2 virus.

To determine if enemas could be used to simulate oral exposure of Aedes aegypti to dengue-2 virus, we compared infection rates of mosquitoes administered an enema of a blood suspension containing dengue-2 virus to infection rates in mosquitoes that imbibed the same suspension from a drop of blood. In 1 of 4 experiments infection rates were significantly different. More importantly, during 2 of the 4 trials, 100% of the mosquitoes in the enema treatment group were infected. We speculate that the capillary tube used to administer the enemas abraded the hindgut of mosquitoes in the groups with 100% infection rates and, therefore, virus was inoculated directly into the mosquitoes' hemocoel. We conclude that the method we used for administering enemas cannot be used to simulate oral exposure of Ae. aegypti to dengue-2 virus.

Failure of immune sera to neutralize dengue-2 virus in intrathoracically inoculated Aedes aegypti.

Aedes aegypti became infected when inoculated with a mixture of dengue-2 virus and anti-dengue-2 antibodies, but not when they were exposed to the same mixture per os. This phenomenon merits more detailed investigation. Understanding why this difference in mosquito infection rate occurs may lead to improved dengue virus assays or provide insights into the nature of dengue virus-antibody interactions.

The effect of multiple host contacts on the infectivity of dengue-2 virus-infected Aedes aegypti.

This study was designed to determine if transmission rates for dengue-2 virus by Aedes aegypti are altered by mosquitos probing a host for blood or imbibing blood prior to attempting transmission. Aedes aegypti is known to contact multiple hosts during each egg-laying cycle and multiple host contacts might diminish the amount of virus in infected mosquito's salivary glands or ducts and render them functionally uninfective. Probing a host 5, 10, or 20 consecutive times did not significantly alter the infectivity of parenterally infected mosquitoes. However, orally infected Ae. aegypti that probed 20 times transmitted dengue viruses at a significantly higher rate than controls. Infectivity of orally infected Ae. aegypti was unaffected by blood feeding. Our data suggest that (1) dengue virus-infected Ae. aegypti remain infective regardless of their probing or engorging history, and (2) once Ae. aegypti become infective they are extremely efficient disseminators of dengue virus.

Blood-feeding behavior of dengue-2 virus-infected Aedes aegypti.

This study was designed to determine if infection of Aedes aegypti with dengue-2 virus affects the ability of the mosquito to efficiently locate and imbibe blood from an uninfected host. Previous studies suggest that some parasites manipulate their arthropod host to increase the probability of transmission by interfering with blood-feeding efficiency. We found no evidence that dengue-2 virus infection by intrathoracic inoculation impaired the blood-feeding efficiency of Ae. aegypti. We speculate that natural selection has not favored the evolution of dengue viruses that increase vector probing time because uninfected Ae. aegypti take multiple blood meals during each gonotrophic cycle and further increases in vector probing would not significantly increase virus fitness.

Posttransfusion purpura due to an alloantibody reactive with glycoprotein Ia/IIa (anti-HPA-5b).

A 38-year-old woman (JT) was diagnosed with posttransfusion purpura and significant posthysterectomy vaginal bleeding 9 days after the transfusion of 2 U of packed red blood cells. Analysis of JT's serum by a monoclonal antibody-antigen capture enzyme-linked immunosorbent assay method showed the presence of anti-HPA-5b (anti-Bra) antibodies directed against an epitope on platelet glycoprotein (GP) la of the GPIa/IIa complex. The patient's serum immunoprecipitated two proteins from 125I-labeled HPA-5b positive platelets that migrated under both nonreducing and reducing conditions on sodium dodecyl sulfate polyacrylamide gels at molecular weights characteristic of GPIa (150 Kd and 165 Kd, respectively) and GPIIa (120 Kd and 145 Kd, respectively). These bands were not precipitated when 125I-labeled HPA-5b negative platelets were used. Platelet typings performed on JT and her three children showed that the patient was HPA-5b negative and one of her children was HPA-5b positive. Platelets obtained from one of the donors who provided blood for the inciting transfusion also typed as HPA-5b positive. These findings demonstrate that posttransfusion purpura may be induced by antibodies directed against an alloantigenic epitope, namely HPA-5b (Bra), located on GPIa/IIa. Moreover, clinically significant bleeding can be associated with antibody reactions directed against this GP complex.

Vancomycin-dependent antibodies associated with thrombocytopenia and refractoriness to platelet transfusion in patients with leukemia.

Two patients with leukemia experienced profound thrombocytopenia and refractoriness to platelet transfusion during vancomycin treatment. In one patient, withdrawal of drug and administration of platelet transfusions restored platelet counts to near normal levels (approximately 100 x 10(9)/L), however, subsequent challenge with vancomycin due to recurring infection again precipitated severe thrombocytopenia (platelets less than 10 x 10(9)/L) and life-threatening hemorrhagic symptoms. Potent vancomycin-dependent antiplatelet antibodies were detected in the serum of both patients during the refractory period using staphylococcal protein A rosette formation. Employing a monoclonal antibody-antigen capture enzyme-linked immunosorbent assay (ELISA), the patients were found to have vancomycin-dependent IgG antibodies that bound specifically to platelet glycoproteins (GP) IIb and/or IIIa. One of these antibodies failed to react with platelets deficient in GPIIb/IIIa obtained from an individual with Glanzmann's thrombasthenia. These findings provide the first major evidence for drug-dependent antibodies in association with severe thrombocytopenia and refractoriness to platelet transfusion in alloimmunized leukemia patients and, further, provide the first demonstration of vancomycin-dependent antibodies reactive with platelets.

Eikenella corrodens in human mouth flora.

The incidence of Eikenella corrodens in the human mouth was studied in 229 individuals. Six (2.6%) had positive cultures. The incidence of positive cultures for the saliva group was 0.6% and for the tooth-scraping group it was 8.2%. When 11 isolates were tested against 33 antimicrobials by disc-agar diffusion, 82% were susceptible to penicillin, cephalothin, and cefoperazone. Susceptibility to the remaining second- and third-generation cephalosporins studied was 100%. We suggest that the use of a second- or third-generation cephalosporin only is appropriate empiric therapy for human bite injuries.