The LMVR insectaries are one of the strengths of the LMVR's research program and a major resource for the NIH and the malaria and leishmaniasis research communities in general. Dr. Tovi Lehmann serves as Facility Head for insectary operations. He is assisted by two experienced technicians and four young, enthusiastic high school/junior college students. The LMVR has significantly increased work on the sandfly vectors of leishmaniasis. The LMVR insectaries maintain five species of Anopheles, some of which are subdivided into genetically selected lines and mutant strains. In addition the facility maintains Aedes aegypti, Ae. albopictus, and Culex quinquefasciatus. On occasions the insectary rears Toxoryhncites amboinensis to support research by the NIAID laboratory working on dengue and West Nile vaccines. Two genera including four species of sandflies are reared in the LMVR. In addition the insectaries maintain Ixodes, Dermacentor and Amblyomma ticks. On occasion, the insectary has supported colonies of Cimex and Rhodnius. The Insectary Team also maintains a colony of chickens. Chickens are regularly infected with the avian malaria Plasmodium gallinaceum;this parasite has been used at the NIH for over 50 years and has proven to be a particularly useful model system for research on this important parasite. Chickens are also used as a source of regular blood meals for mosquito colony maintenance. In addition to supporting mosquito research in the International Studies Section, there are significant projects requiring mosquitoes in the Mosquito Immunity and Vector Competence Unit of Dr. Barillas-Mury, and the Vector Biology Section of Dr. Ribeiro. The Malaria Genetics Section under Dr. Wellems is involved in conducting a genetic cross between drug sensitive and drug resistant strains of Plasmodium vivax. The genetic recombination of these parasites must take place in the gut of a mosquito vector and the resulting sporozoites carrying either of the two parental genotypes or the recombination genotype are used to initiate infection in a monkey host. In the past the LMVR insectaries have supported such genetic crosses using various parasite genotypes in P. falciparum and chimpanzees and Aotus monkeys. The cloned parasites derived from such crosses have proven exceptionally valuable in the Laboratory's studies of drug resistance in malaria. The Laboratory of Malaria Immunology and Vaccinology uses the LMVR vector containment facility for infecting mosquitoes with P. falciparum and testing the efficacy of various antibodies in the quest for a transmission blocking vaccine. The LMIV has recently initiated studies with transgenic parasites and is testing drugs against the relapsing forms (hypnozoites) of the malaria parasite. Such studies require the use of sporozoite-initiated infections in a monkey model. Mosquitoes for these studies are reared and maintained in the LMVR insectaries. Research on the development of vaccines for leishmaniasis has focused primarily on antigens derived from sandfly saliva. The life cycle of the parasite requiring the sandfly vector is conducted in the secure LMVR insectary. The sandfly colony closely supports and collaborates with the sandfly/leishmaniasis programs in the LPD and at the WRAIR facility at Forest Glen. A. The Sections research projects in Mali focus on a number of important features of vector biology. 1. Contribution of aestivating mosquitoes to the expansion of vector populations at the beginning of the rainy season.These studies, based in Mali have demonstrated that female mosquitoes can survive a harsh dry season and be present at the start of the rainy season to initiate the populations that are eventually responsible for seasonal malaria transmission. We are also examining the role of migration from permanent breeding areas into more arid habitats at the beginning of the rains. 2. Longevity-reproduction relationship of An. gambiae. We have shown that mated females show reduced lower survival as compared to virgin females. 3. Physiological and behavioral changes that underlie aestivating mosquitoes. To understand the mechanisms facilitating aestivation and to distinguish between aestivating and non-aestivating mosquitoes during the dry season, we are measuring metabolism, flight activity, body size, egg development and oviposition, nutritional reserves and cuticular hydrocarbons. 4. Hidden shelters of mosquitoes during the dry season in the Sahel. In Mali, we have found that dry season mosquitoes usually cluster in houses near the periphery of villages. During the wet season, mosquitoes do not shelter in houses, but outside in a variety of sites such as burrows, tree holes and termite mounds. 5. Changes in the capacity of mosquitoes to transmit malaria during the dry season. Field collected mosquitoes are being subjected to genotypic analysis and ELISA determination of infection to determine presence of malaria infection during the dry season. 6. Mating biology of An. gambiae and its role in reproductive isolation and speciation. We have shown that monotypic mating swarms act as a pre-zygotic barrier to hybridization among the various forms of An. gambiae. 7. The application of computer tracking and 3D night photography of mating swarms to describe the mating behavior of An. gambiae in Mali. In cooperation with scientists in the Department of Aerospace Engineering at the University of Maryland, we are studying the swarming behavior of An. gambiae and the ability for mate selection in the complex swarm arragement. B. Research in the LMVR insectaries in Rockville 1. The genetics and physiology of An. stephensi to P. gallinaceum. We have shown that the largest component of vector susceptibility is related to the vector itself. Environmental factors play a role, but the parasite contributed little to variability. 2. The fitness """"""""cost of resistance of An. stephensi to P. gallinaceum.We are examining the """"""""cost"""""""" of malaria infection to the mosquito host on such factors as larval growth rate, larval development success, body size, egg batch size, male mating potential and longevity. 3. Comparisons of metabolic rate and body size in dry and wet season populations. In Mali, the metabolism of wild caught mosquitoes was measured over a year. The seasonal effects on flight activity, body size, temperature, molecular form, sex and gonotrophic status to metabolism are being analyzed. 4. Correlations between cuticular hydrocarbons and nutritional reserves in wet and dry season An. gambiae. We are determining the density of cuticular hydrocarbons in wet and drty season mosquitoes to determine their role in dry season survival. 5 The evolution of resistance and tolerance of Aedes albopictus mosquitoes to the dog heartworm, Dirofilaria immitis. Ae. albopictus was introduced into the United States less than 50 years ago. Spreading from its introduction in Texas thought most of the Eastern US, the species has become a major urban pest and recently a major vector of dog heartworm.The """"""""immune"""""""" responses of the mosquito vector to the filarial parasite are being measured. 6.The selection of Primaquine resistance in the 8A strain strain of P. gallinaceum and the isolation and characterization of a new isolate of P. gallinaceum from Thailand. Primaquine, an 8-amino quinoline drug, is the primary drug used for the radical cure of relapsing malarias such as P. vivax. We are usding the chicken malaria model to select for resistance to the drug in an attempt to describe the genetic basis of drug resistance. The new isolate from Thailand, the first in over 75 years, should give us a strain with greater genetic diversity to facilitate selection.
Showing the most recent 10 out of 19 publications
