The temporal dynamics of Plasmodium density through the sporogonic cycle within Anopheles mosquitoes

Dawes, Emma J; Zhuang, Shijie; Sinden, Robert E.; Basáñez, María‐Gloria

doi:10.1016/j.trstmh.2009.03.009

Cited by 18 publications

(17 citation statements)

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“…In all the future studies we fixed gametocyte concentration at 0.3% and varied other components. A similar positive association between gametocyte density and mosquito infection has been reported in many previous published studies using murine and human malaria parasites (both lab adapted and field isolates) in different anopheline species (Carter and Graves, 1988; Da et al, 2015; Dawes et al, 2009; Drakeley et al, 1999; Poudel et al, 2008; Sinden et al, 2007). Apart from the actual number of gametocytes, maturity and sex ratios of the gametocytes and the presence of natural immune factors can also influence the outcome of infection in the mosquitoes.…”

Section: Discussionsupporting

confidence: 85%

Modulation of transmission success of Plasmodium falciparum gametocytes (sexual stages) in various species of Anopheles by erythrocytic asexual stage parasites

Kumar

2017

Acta Tropica

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During malaria infection, a small proportion of erythrocytic asexual stages undergo sexual differentiation. Male and female gametocytes ingested in the blood meal initiate the sexual development of malaria parasites in the mosquito midgut. During blood feeding on a host, a mosquito ingests, in addition to mature gametocytes, host immune factors present in the blood, as well as large excess of erythrocytic asexual stages. In the current study we addressed the impact of the presence of large excess of asexual stages, hitherto not known or even suspected to influence, on the infectivity of gametocytes in the mosquito. Asexual stages resulted in a dose-dependent inhibition of infectiousness of gametocytes, and some of this could be explained by the presumed effect of hemozoin and other unknown asexual-stage components on the mosquito immune system, affecting survival and maturation of parasites in the mosquito midgut. Interactions between asexual and sexual stages, maturity and ratio of male and female gametocytes, host immune factors and mosquito innate immune factors are some of the variables that determine the infectiousness of gametocytes in the mosquitoes and ultimately malaria transmission success. Understanding of determinants affecting malaria transmission will be critical to approaches directly targeting the transmission process for malaria elimination.

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Section: Discussionsupporting

confidence: 85%

Modulation of transmission success of Plasmodium falciparum gametocytes (sexual stages) in various species of Anopheles by erythrocytic asexual stage parasites

Kumar

2017

Acta Tropica

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“…This suggests that Plasmodium density has the potential of affecting the shape of the hazard function of infected Anopheles mosquitoes over their full life-span. Interestingly, no specific change in mortality rate was seen on day 12 or 14 when sporozoites were first found in the salivary glands of the sample of mosquitoes dissected from each of the groups [50]. …”

Section: Discussionmentioning

confidence: 99%

“…This paper reports the results of the survival analysis. A summary of the resulting dynamics of parasite stages and densities with time post-feeding has been presented elsewhere [50]. …”

Section: Methodsmentioning

confidence: 99%

Anopheles mortality is both age- and Plasmodium-density dependent: implications for malaria transmission

Dawes

Churcher

Zhuang

et al. 2009

Malar J

Self Cite

104

121

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BackgroundDaily mortality is an important determinant of a vector's ability to transmit pathogens. Original simplifying assumptions in malaria transmission models presume vector mortality is independent of age, infection status and parasite load. Previous studies illustrate conflicting evidence as to the importance of Plasmodium-induced vector mortality, but very few studies to date have considered the effect of infection density on mosquito survival.MethodsA series of three experiments were conducted, each consisting of four cages of 400-1,000 Anopheles stephensi mosquitoes fed on blood infected with different Plasmodium berghei ookinete densities per microlitre of blood. Twice daily the numbers of dead mosquitoes in each group were recorded, and on alternate days a sample of live mosquitoes from each group were dissected to determine parasite density in both midgut and salivary glands.ResultsSurvival analyses indicate that mosquito mortality is both age- and infection intensity-dependent. Mosquitoes experienced an initially high, partly feeding-associated, mortality rate, which declined to a minimum before increasing with mosquito age and parasite intake. As a result, the life expectancy of a mosquito is shown to be dependent on both insect age and the density of Plasmodium infection.ConclusionThese results contribute to understanding in greater detail the processes that influence sporogony in the mosquito, indicate the impact that parasite density could have on malaria transmission dynamics, and have implications for the design, development, and evaluation of transmission-blocking strategies.

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“…The ingestion of infected blood is also known to trigger a powerful immune response [40-42], which peaks 24-48 hours post feeding and is maintained throughout the infection albeit at a lower level [43,44]. That immune reaction burst coincides with a drastic reduction in the number of invading parasites [43,45]. Immune reactions also carry an energetic cost which is thought to reduce host fecundity through trade-offs between immunity and reproduction [46-48].…”

Section: Discussionmentioning

confidence: 99%

Hydric stress-dependent effects of Plasmodium falciparum infection on the survival of wild-caught Anopheles gambiae female mosquitoes

Aboagye-Antwi

Guindo

Traoré

et al. 2010

Malar J

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BackgroundWhether Plasmodium falciparum, the agent of human malaria responsible for over a million deaths per year, causes fitness costs in its mosquito vectors is a burning question that has not yet been adequately resolved. Understanding the evolutionary forces responsible for the maintenance of susceptibility and refractory alleles in natural mosquito populations is critical for understanding malaria transmission dynamics.MethodsIn natural mosquito populations, Plasmodium fitness costs may only be expressed in combination with other environmental stress factors hence this hypothesis was tested experimentally. Wild-caught blood-fed Anopheles gambiae s.s. females of the M and S molecular form from an area endemic for malaria in Mali, West Africa, were brought to the laboratory and submitted to a 7-day period of mild hydric stress or kept with water ad-libitum. At the end of this experiment all females were submitted to intense desiccation until death. The survival of all females throughout both stress episodes, as well as their body size and infection status was recorded. The importance of stress, body size and molecular form on infection prevalence and female survival was investigated using Logistic Regression and Proportional-Hazard analysis.ResultsFemales subjected to mild stress exhibited patterns of survival and prevalence of infection compatible with increased parasite-induced mortality compared to non-stressed females. Fitness costs seemed to be linked to ookinetes and early oocyst development but not the presence of sporozoites. In addition, when females were subjected to intense desiccation stress, those carrying oocysts exhibited drastically reduced survival but those carrying sporozoites were unaffected. No significant differences in prevalence of infection and infection-induced mortality were found between the M and S molecular forms of Anopheles gambiae.ConclusionsBecause these results suggest that infected mosquitoes may incur fitness costs under natural-like conditions, they are particularly relevant to vector control strategies aiming at boosting naturally occurring refractoriness or spreading natural or foreign genes for refractoriness using genetic drive systems in vector populations.

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The temporal dynamics of Plasmodium density through the sporogonic cycle within Anopheles mosquitoes

Cited by 18 publications

References 1 publication

Modulation of transmission success of Plasmodium falciparum gametocytes (sexual stages) in various species of Anopheles by erythrocytic asexual stage parasites

Modulation of transmission success of Plasmodium falciparum gametocytes (sexual stages) in various species of Anopheles by erythrocytic asexual stage parasites

Anopheles mortality is both age- and Plasmodium-density dependent: implications for malaria transmission

Hydric stress-dependent effects of Plasmodium falciparum infection on the survival of wild-caught Anopheles gambiae female mosquitoes

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