The prevalence of naturally acquired multiple infections of Wuchereria bancrofti and human malarias in anophelines

Abstract

SUMMARYMalaria and filaria infection rates were determined for anopheline mosquitoes collected whilst biting and resting in village houses in Papua New Guinea. The number of anophelines infected with both parasites was greater than expected from the infection rates of each parasite and this difference was significant in resting collections. The excess of multiply infected mosquitoes is probably a result of a vector population composed of individuals with differing numbers of opportunities to become infected. Malaria-positive Anopheles punctulatus from resting catches had a significantly greater number of Stage 3 Wuchereria bancrofti larvae than malaria-negative mosquitoes. However, multiply infected mosquitoes appear to suffer greater mortality than non-infected or singly infected mosquitoes when the filarial worm reaches the third stage. Any potential increase in transmission resulting from multiple infections is thereby offset by a greater mortality rate in these mosquitoes.

Mixed-Species Plasmodium Infections of Anopheles (Diptera: Culicidae)

“…The 2 complete sets of Thai figures (Rosenberg et al 1990a, b) apply to the 1st and 2nd yr of a village study; in each year the prevalence of mixed-species infections in mosquitoes fit the hypothesis of the statistical independence of the species, whereas that in humans was less than half the expected value. The 3rd Thai figure (Gingrich et al 1990; for mosquitoes only) applies to the following 2 yr in the same village; the observed mixed-species prevalence in mosquitoes again fit the product of the singles species prevalences.The entomological studies conducted by Burkot et al (1990Burkot et al ( , 1992 et al 1986). In Buksak, for 1986 and 1986-1987 the observed prevalence of mixed-species infections in resting catches (6 and 9% of positives, respectively) far exceeded expected values, whereas the observed prevalence in 1987 resting catches and 1986-1987 biting catches (1 and 8% of positives, respectively) fit expected values.…”

Can mosquitoes help to unravel the community structure of Plasmodium species?

“…Parasite species spend the majority of their lifecycles within the human host and, thus, have greater opportunity to interact within humans than within mosquitoes. However, as clearly parameterized in the classic Ross-Macdonald model of malaria [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] (Box 1), the distribution of vector-borne parasites depends on vector-vertebrate and vectorparasite interactions, in addition to interactions within vertebrates. Given that vector-based (as opposed to therapy-based) interventions represent the mainstay of prevention strategies, it seems essential to consider initially species differences that relate to vectorial parameters and, thus, the consequences of vector-based interventions for species distribution.…”

“…There is conflicting evidence concerning the effect of infection on m [11,12] and a [13][14][15]. Although there is some suggestion that Plasmodium-microfilaria co-infections increase m, reduce T [16] and affect parasite development [17], no studies to date have addressed the impact of mixed Plasmodium species infections on these mosquito parameters.…”

“…Indirect approaches based on comparisons of mixed-species infection rates in sympatric human and mosquito populations have revealed conflicting results but were based on limited datasets [40,41]. There is a need for laboratory studies to determine the sporogonic consequences of mixed Plasmodium species infections, especially because co-infection with microfilaria and Plasmodium has been shown to increase mosquito mortality rates and reduce parasite development [16,17]. In addition to the important effects that mixed infections might have on one another during the relatively long period of sporogonic development, the Ross-Macdonald model indicates another parameter of importance: the proportion of bloodmeals from infected humans that gives rise to an infected mosquito (c) (Box 1).…”

Molecular-Based Assay for Simultaneous Detection of Four Plasmodium spp. and Wuchereria bancrofti Infections

“…2 Malaria and bancroftian filariasis are co-endemic in many tropical and sub-tropical regions, such as Southeast Asia, including the western Pacific, Africa, and Central and South America, and are transmitted by a number of common vector species. 3,4 Thus, co-infections with malaria and bancroftian parasites in humans [5][6][7] and mosquitoes 7,8 are found in these regions.…”