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Interactions between a fungal entomopathogen and malaria parasites within a mosquito vector.

Heinig RL, Thomas MB - Malar. J. (2015)

Bottom Line: The study used two parasite species to examine possible effects of fungal infection at different parasite development stages.Similarly, for P. falciparum, there was no evidence that fungal infection affected sporozoite prevalence.These results suggest that the impact of fungus on malaria control potential is limited to the well-established effects on mosquito survival and transmission behaviour.

View Article: PubMed Central - PubMed

Affiliation: Merkle Laboratory, The Pennsylvania State University, University Park, PA, 16803, USA. yxh5118@psu.edu.

ABSTRACT

Background: Mosquitoes are becoming increasingly resistant to the chemical insecticides currently available for malaria vector control, spurring interest in alternative management tools. One promising technology is the use of fungal entomopathogens. Fungi have been shown to impact the potential for mosquitoes to transmit malaria by reducing mosquito longevity and altering behaviour associated with flight and host location. Additionally, fungi could impact the development of malaria parasites within the mosquito via competition for resources or effects on the mosquito immune system. This study evaluated whether co-infection or superinfection with the fungal entomopathogen Beauveria bassiana affected malaria infection progress in Anopheles stephensi mosquitoes.

Methods: The study used two parasite species to examine possible effects of fungal infection at different parasite development stages. First, the rodent malaria model Plasmodium yoelii was used to explore interactions at the oocyst stage. Plasmodium yoelii produces high oocyst densities in infected mosquitoes and thus was expected to maximize host immunological and resource demands. Second, fungal interactions with mature sporozoites were evaluated by infecting mosquitoes with the human malaria species Plasmodium falciparum, which is highly efficient at invading mosquito salivary glands.

Results: With P. yoelii, there was no evidence that fungal co-infection (on the same day as the blood meal) or superinfection (during a subsequent gonotrophic cycle after parasite infection) affected the proportion of mosquitoes with oocysts, the number of oocysts per infected mosquito or the number of sporozoites per oocyst. Similarly, for P. falciparum, there was no evidence that fungal infection affected sporozoite prevalence. Furthermore, there was no impact of infection with either malaria species on fungal virulence as measured by mosquito survival time.

Conclusions: These results suggest that the impact of fungus on malaria control potential is limited to the well-established effects on mosquito survival and transmission behaviour. Direct or indirect interactions between fungus and malaria parasites within mosquitoes appear to have little additional influence.

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Related in: MedlinePlus

Cumulative proportional survival of adult mosquitoes in thePlasmodium yoeliiexperiment.Anopheles stephensi mosquitoes were fed either on P. yoelii-infected or control mice (indicated by line type), then exposed to tiles sprayed with B. bassiana conidial suspensions or blank oil (indicated by marker) either the same day as the blood meal (d0) or three days later (d3, indicated by line colour). Each point represents the mean of five replicates (± standard error).
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Fig1: Cumulative proportional survival of adult mosquitoes in thePlasmodium yoeliiexperiment.Anopheles stephensi mosquitoes were fed either on P. yoelii-infected or control mice (indicated by line type), then exposed to tiles sprayed with B. bassiana conidial suspensions or blank oil (indicated by marker) either the same day as the blood meal (d0) or three days later (d3, indicated by line colour). Each point represents the mean of five replicates (± standard error).

Mentions: Mosquito mortality rate varied with treatment group (Figure 1) but was not significantly affected by P. yoelii malaria infection status (hazard ratio (HR) = 0.95, z = −0.77, p = 0.44). Fungal exposure significantly increased mortality rate (HR = 17.06, z = 21.11, p < 0.001); mosquitoes exposed to fungus had median survival times of eight to ten days relative to >25 days in the controls. There was also a significant interaction between fungal exposure and exposure day (HR = 0.64, z = −3.42, p = 0.001), such that, even after accounting for the delay in fungal infection, the mosquitoes exposed to fungus on day 3 had median survival times about one day longer than those exposed on the same day as the blood meal.Figure 1


Interactions between a fungal entomopathogen and malaria parasites within a mosquito vector.

Heinig RL, Thomas MB - Malar. J. (2015)

Cumulative proportional survival of adult mosquitoes in thePlasmodium yoeliiexperiment.Anopheles stephensi mosquitoes were fed either on P. yoelii-infected or control mice (indicated by line type), then exposed to tiles sprayed with B. bassiana conidial suspensions or blank oil (indicated by marker) either the same day as the blood meal (d0) or three days later (d3, indicated by line colour). Each point represents the mean of five replicates (± standard error).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4318179&req=5

Fig1: Cumulative proportional survival of adult mosquitoes in thePlasmodium yoeliiexperiment.Anopheles stephensi mosquitoes were fed either on P. yoelii-infected or control mice (indicated by line type), then exposed to tiles sprayed with B. bassiana conidial suspensions or blank oil (indicated by marker) either the same day as the blood meal (d0) or three days later (d3, indicated by line colour). Each point represents the mean of five replicates (± standard error).
Mentions: Mosquito mortality rate varied with treatment group (Figure 1) but was not significantly affected by P. yoelii malaria infection status (hazard ratio (HR) = 0.95, z = −0.77, p = 0.44). Fungal exposure significantly increased mortality rate (HR = 17.06, z = 21.11, p < 0.001); mosquitoes exposed to fungus had median survival times of eight to ten days relative to >25 days in the controls. There was also a significant interaction between fungal exposure and exposure day (HR = 0.64, z = −3.42, p = 0.001), such that, even after accounting for the delay in fungal infection, the mosquitoes exposed to fungus on day 3 had median survival times about one day longer than those exposed on the same day as the blood meal.Figure 1

Bottom Line: The study used two parasite species to examine possible effects of fungal infection at different parasite development stages.Similarly, for P. falciparum, there was no evidence that fungal infection affected sporozoite prevalence.These results suggest that the impact of fungus on malaria control potential is limited to the well-established effects on mosquito survival and transmission behaviour.

View Article: PubMed Central - PubMed

Affiliation: Merkle Laboratory, The Pennsylvania State University, University Park, PA, 16803, USA. yxh5118@psu.edu.

ABSTRACT

Background: Mosquitoes are becoming increasingly resistant to the chemical insecticides currently available for malaria vector control, spurring interest in alternative management tools. One promising technology is the use of fungal entomopathogens. Fungi have been shown to impact the potential for mosquitoes to transmit malaria by reducing mosquito longevity and altering behaviour associated with flight and host location. Additionally, fungi could impact the development of malaria parasites within the mosquito via competition for resources or effects on the mosquito immune system. This study evaluated whether co-infection or superinfection with the fungal entomopathogen Beauveria bassiana affected malaria infection progress in Anopheles stephensi mosquitoes.

Methods: The study used two parasite species to examine possible effects of fungal infection at different parasite development stages. First, the rodent malaria model Plasmodium yoelii was used to explore interactions at the oocyst stage. Plasmodium yoelii produces high oocyst densities in infected mosquitoes and thus was expected to maximize host immunological and resource demands. Second, fungal interactions with mature sporozoites were evaluated by infecting mosquitoes with the human malaria species Plasmodium falciparum, which is highly efficient at invading mosquito salivary glands.

Results: With P. yoelii, there was no evidence that fungal co-infection (on the same day as the blood meal) or superinfection (during a subsequent gonotrophic cycle after parasite infection) affected the proportion of mosquitoes with oocysts, the number of oocysts per infected mosquito or the number of sporozoites per oocyst. Similarly, for P. falciparum, there was no evidence that fungal infection affected sporozoite prevalence. Furthermore, there was no impact of infection with either malaria species on fungal virulence as measured by mosquito survival time.

Conclusions: These results suggest that the impact of fungus on malaria control potential is limited to the well-established effects on mosquito survival and transmission behaviour. Direct or indirect interactions between fungus and malaria parasites within mosquitoes appear to have little additional influence.

Show MeSH
Related in: MedlinePlus