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the wall of a mosquito midgut
Credit: Krijn Paaijmans
Researchers have found the environment can significantly influence whether or not Wolbachia bacteria will prevent mosquitoes from transmitting malaria.
“Bacteria in the genus Wolbachia represent a promising new tool for controlling malaria due to their demonstrated ability to block the development of the pathogen within Anopheles mosquitoes,” said study investigator Courtney Murdock, PhD, of Pennsylvania State University.
“However, much of the work on the Wolbachia-malaria interaction has been conducted under highly simplified laboratory conditions. In this study, we investigated the ability of Wolbachia to block transmission of malaria—Plasmodium—parasites across variable environmental conditions, which are more reflective of conditions in the field.”
Dr Murdock and her colleagues described this research in Nature Scientific Reports.
The researchers used the malaria parasite Plasmodium yoelii, which affects rodents, and the mosquito Anopheles stephensi as a model system to investigate whether Wolbachia would block the ability of the malaria parasite to infect the mosquitoes.
The team divided the mosquitoes into an uninfected control group and a group infected with Wolbachia. Next, they raised all groups of mosquitoes in incubators set to different experimental temperatures—68, 72, 75, 79, and 82 degrees Fahrenheit.
At 82 degrees, Wolbachia reduced the number of mosquitoes infected by malaria parasites, the number of malaria parasites within each mosquito, and the intensity of oocysts.
At 75 degrees, Wolbachia had no effect on the prevalence of malaria parasites but increased oocyst intensity. At 68 degrees, Wolbachia had no effect on the prevalence of parasites or the intensity of oocysts.
The researchers also identified a previously undiscovered effect of Wolbachia. Infection with the bacterium reduced the development of sporozoites across all temperatures. This suggests that Wolbachia and malaria parasites may compete for similar hosts.
“Typically, the more oocysts a mosquito has on its midgut, the more sporozoites it produces,” Dr Murdock said. “So, depending on the environmental temperature, Wolbachia either reduced, enhanced, or had no effect on the number of oocysts.”
“At 75 degrees Fahrenheit, Wolbachia-infected mosquitos had 3 times the numbers of oocysts relative to uninfected mosquitoes. Thus, we would predict these mosquitoes to produce more sporozoites. But instead, we see that this is not the case, and that is because Wolbachia infection significantly reduces the number of sporozoites produced per oocyst, regardless of the environmental temperature.”
“This effect counteracts the enhancement we see at 75 degrees Fahrenheit. How the influence of Wolbachia on parasite establishment and the production of sporozoites under different temperatures plays out to ultimately affect transmission remains to be determined.”
Dr Murdock and her colleagues plan to duplicate their experiment using a species of malaria parasite that affects humans to determine whether or not the temperature effects they observed occur in humans as well.
The team also intends to explore the effects of additional environmental variation—such as daily temperature fluctuation and differential access to food resources in the mosquito larval and adult environments—on the transmission-blocking ability of Wolbachia. 
the wall of a mosquito midgut
Credit: Krijn Paaijmans
Researchers have found the environment can significantly influence whether or not Wolbachia bacteria will prevent mosquitoes from transmitting malaria.
“Bacteria in the genus Wolbachia represent a promising new tool for controlling malaria due to their demonstrated ability to block the development of the pathogen within Anopheles mosquitoes,” said study investigator Courtney Murdock, PhD, of Pennsylvania State University.
“However, much of the work on the Wolbachia-malaria interaction has been conducted under highly simplified laboratory conditions. In this study, we investigated the ability of Wolbachia to block transmission of malaria—Plasmodium—parasites across variable environmental conditions, which are more reflective of conditions in the field.”
Dr Murdock and her colleagues described this research in Nature Scientific Reports.
The researchers used the malaria parasite Plasmodium yoelii, which affects rodents, and the mosquito Anopheles stephensi as a model system to investigate whether Wolbachia would block the ability of the malaria parasite to infect the mosquitoes.
The team divided the mosquitoes into an uninfected control group and a group infected with Wolbachia. Next, they raised all groups of mosquitoes in incubators set to different experimental temperatures—68, 72, 75, 79, and 82 degrees Fahrenheit.
At 82 degrees, Wolbachia reduced the number of mosquitoes infected by malaria parasites, the number of malaria parasites within each mosquito, and the intensity of oocysts.
At 75 degrees, Wolbachia had no effect on the prevalence of malaria parasites but increased oocyst intensity. At 68 degrees, Wolbachia had no effect on the prevalence of parasites or the intensity of oocysts.
The researchers also identified a previously undiscovered effect of Wolbachia. Infection with the bacterium reduced the development of sporozoites across all temperatures. This suggests that Wolbachia and malaria parasites may compete for similar hosts.
“Typically, the more oocysts a mosquito has on its midgut, the more sporozoites it produces,” Dr Murdock said. “So, depending on the environmental temperature, Wolbachia either reduced, enhanced, or had no effect on the number of oocysts.”
“At 75 degrees Fahrenheit, Wolbachia-infected mosquitos had 3 times the numbers of oocysts relative to uninfected mosquitoes. Thus, we would predict these mosquitoes to produce more sporozoites. But instead, we see that this is not the case, and that is because Wolbachia infection significantly reduces the number of sporozoites produced per oocyst, regardless of the environmental temperature.”
“This effect counteracts the enhancement we see at 75 degrees Fahrenheit. How the influence of Wolbachia on parasite establishment and the production of sporozoites under different temperatures plays out to ultimately affect transmission remains to be determined.”
Dr Murdock and her colleagues plan to duplicate their experiment using a species of malaria parasite that affects humans to determine whether or not the temperature effects they observed occur in humans as well.
The team also intends to explore the effects of additional environmental variation—such as daily temperature fluctuation and differential access to food resources in the mosquito larval and adult environments—on the transmission-blocking ability of Wolbachia.
the wall of a mosquito midgut
Credit: Krijn Paaijmans
Researchers have found the environment can significantly influence whether or not Wolbachia bacteria will prevent mosquitoes from transmitting malaria.
“Bacteria in the genus Wolbachia represent a promising new tool for controlling malaria due to their demonstrated ability to block the development of the pathogen within Anopheles mosquitoes,” said study investigator Courtney Murdock, PhD, of Pennsylvania State University.
“However, much of the work on the Wolbachia-malaria interaction has been conducted under highly simplified laboratory conditions. In this study, we investigated the ability of Wolbachia to block transmission of malaria—Plasmodium—parasites across variable environmental conditions, which are more reflective of conditions in the field.”
Dr Murdock and her colleagues described this research in Nature Scientific Reports.
The researchers used the malaria parasite Plasmodium yoelii, which affects rodents, and the mosquito Anopheles stephensi as a model system to investigate whether Wolbachia would block the ability of the malaria parasite to infect the mosquitoes.
The team divided the mosquitoes into an uninfected control group and a group infected with Wolbachia. Next, they raised all groups of mosquitoes in incubators set to different experimental temperatures—68, 72, 75, 79, and 82 degrees Fahrenheit.
At 82 degrees, Wolbachia reduced the number of mosquitoes infected by malaria parasites, the number of malaria parasites within each mosquito, and the intensity of oocysts.
At 75 degrees, Wolbachia had no effect on the prevalence of malaria parasites but increased oocyst intensity. At 68 degrees, Wolbachia had no effect on the prevalence of parasites or the intensity of oocysts.
The researchers also identified a previously undiscovered effect of Wolbachia. Infection with the bacterium reduced the development of sporozoites across all temperatures. This suggests that Wolbachia and malaria parasites may compete for similar hosts.
“Typically, the more oocysts a mosquito has on its midgut, the more sporozoites it produces,” Dr Murdock said. “So, depending on the environmental temperature, Wolbachia either reduced, enhanced, or had no effect on the number of oocysts.”
“At 75 degrees Fahrenheit, Wolbachia-infected mosquitos had 3 times the numbers of oocysts relative to uninfected mosquitoes. Thus, we would predict these mosquitoes to produce more sporozoites. But instead, we see that this is not the case, and that is because Wolbachia infection significantly reduces the number of sporozoites produced per oocyst, regardless of the environmental temperature.”
“This effect counteracts the enhancement we see at 75 degrees Fahrenheit. How the influence of Wolbachia on parasite establishment and the production of sporozoites under different temperatures plays out to ultimately affect transmission remains to be determined.”
Dr Murdock and her colleagues plan to duplicate their experiment using a species of malaria parasite that affects humans to determine whether or not the temperature effects they observed occur in humans as well.
The team also intends to explore the effects of additional environmental variation—such as daily temperature fluctuation and differential access to food resources in the mosquito larval and adult environments—on the transmission-blocking ability of Wolbachia.