Local Vector Populations Research Articles

Co-adaptation between cassava mosaic geminiviruses and their local vector populations

Four cassava mosaic geminivirus (CMG) isolates; African cassava mosaic virus from Namulonge, Uganda (ACMV-[Nam]), East African cassava mosaic virus from Mtwara, Tanzania (EACMV-[Mtw]), EACMV-Uganda from Namulonge (EACMV-UG[Nam]) and Indian cassava mosaic virus from Trivandrum, India (ICMV-[Tri]) were compared for their ability to be transmitted by four colonies of cassava whitefly, Bemisia tabaci (Gennadius), collected from Namulonge (NAM), Mtwara (MTW), Kumasi (KUM) and Trivandrum (TRI). With 20 adult whiteflies per test plant, the CMGs from Africa were transmitted by all three of the African B. tabaci populations to 60–79% of the target plants. Indian cassava B. tabaci transmitted ICMV-[Tri] to 89% of the target plants. In contrast, Indian cassava B. tabaci transmitted EACMV-[Mtw] and Tanzanian cassava B. tabaci transmitted ICMV-[Tri] less than a tenth as often, even when using 50 adults per plant and with increased acquisition and inoculation access periods. The complete coat protein genes of the CMGs had sequences typical of their source viruses, the major differences occurring between those originating from India and Africa. Symptom severity of the CMGs was quantified precisely by both visual assessment and image analysis techniques. EACMV-[Mtw] and ACMV-[Nam] were the most and least damaging isolates with 15.4 and 10.0% of the leaf area diseased, respectively. In these tests the transmission frequency was not linked to symptom severity in the source plants. These data support the hypothesis that virus-vector co-adaptation exists in the cassava mosaic disease (CMD) pathosystem and the results are discussed in relation to CMD epidemiology.

Etiology of the acrodermatitis chronica atrophicans lesion in Lyme disease.

Spirochete diversity in acrodermatitis chronica atrophicans lesions in a closely defined central European site was compared to that in the local vector population, in human erythema migrans lesions, and in cerebrospinal fluid by amplifying and sequencing a segment of the gene of outer surface protein A directly from sampled tissues. Borrelia garinii, Borrelia afzelii, and Borrelia burgdorferi acutely infect human skin and invade internal tissues. Only B. afzelii, however, is associated with acrodermatitis chronica atrophicans lesions, persisting chronically where the skin has atrophied.

Morphologic Variants of Anopheles Albimanus and Susceptibility to Plasmodium Vivax and P. Falciparum

Three morphologically different, true-breeding phenotypes have been isolated from a strain of Anopheles albimanus from Lake Apastepeque, El Salvador. Studies with coindigenous strains of Plasmodium vivax and P. falciparum show that these phenotypes differ significantly in their susceptibility to malaria parasites. This difference is apparent both in the number of mosquitoes that become infected and the level of infection obtained. Variations in malaria susceptibility are markedly greater with P. vivax than with P. falciparum. The significance of genetic variants within a local vector population with respect to the epidemiology of malaria is discussed.