User login
Photo by James Gathany
Mosquitoes carrying a greater number of malaria-causing parasites may be more likely to cause infection, according to a study published in PLOS Pathogens.
More than 100 years have passed since scientists first discovered that infectious mosquitoes inject malaria parasites when they bite people.
However, it hasn’t been clear whether injecting more parasites with each bite increases a person’s chances of infection or if all infectious bites are equally dangerous.
In the new study, researchers set out to determine whether the number of parasites found in the salivary glands of malaria-carrying mosquitos impacts disease transmission.
Via experiments in mice, the team determined that the more parasites present in a mosquito’s salivary glands, the more likely it was to be infectious and the faster an infection would develop.
“It is surprising that the relationship between parasite density and infectiousness has not been properly investigated before, but the studies are quite complex to carry out,” noted Andrew Blagborough, PhD, of Imperial College London in the UK.
For this study, he and his colleagues set up repeated cycles of infection so that groups of infected mosquitoes containing variable numbers of parasites repeatedly bit sedated mice, transmitting malaria to them under a range of transmission settings.
This allowed the researchers to track how many individual parasites different mosquitoes harbored, how many mice were infected as a result of exposure to them, and how long it took the mice to develop malaria.
The team also analyzed data from human volunteers who were exposed to bites from infectious mosquitoes.
Dissection of these mosquitoes revealed that infection was significantly more likely—and occurred sooner—after bites from mosquitoes with more than 1000 individual parasites in their salivary glands.
By conducting further studies with mice and human volunteers, the researchers were able to provide an explanation for why the malaria vaccine RTS,S is effective only some of the time and why any protection rapidly drops off after 3 years.
The vaccine was less effective when mice or humans were bitten by mosquitoes carrying a greater number of parasites. The researchers think this is because the vaccine can only kill a certain proportion of the parasites and is overwhelmed when the parasite population is too large.
“Vaccine development has come a long way, and this new insight should help future vaccine studies to be tested more rigorously,” said study author Thomas Churcher, PhD, of Imperial College London.
“However, in the end, it is unlikely that one magic bullet will eradicate malaria, and we should continue to seek and apply combinations of strategies for reducing the burden of this disease.” 
Photo by James Gathany
Mosquitoes carrying a greater number of malaria-causing parasites may be more likely to cause infection, according to a study published in PLOS Pathogens.
More than 100 years have passed since scientists first discovered that infectious mosquitoes inject malaria parasites when they bite people.
However, it hasn’t been clear whether injecting more parasites with each bite increases a person’s chances of infection or if all infectious bites are equally dangerous.
In the new study, researchers set out to determine whether the number of parasites found in the salivary glands of malaria-carrying mosquitos impacts disease transmission.
Via experiments in mice, the team determined that the more parasites present in a mosquito’s salivary glands, the more likely it was to be infectious and the faster an infection would develop.
“It is surprising that the relationship between parasite density and infectiousness has not been properly investigated before, but the studies are quite complex to carry out,” noted Andrew Blagborough, PhD, of Imperial College London in the UK.
For this study, he and his colleagues set up repeated cycles of infection so that groups of infected mosquitoes containing variable numbers of parasites repeatedly bit sedated mice, transmitting malaria to them under a range of transmission settings.
This allowed the researchers to track how many individual parasites different mosquitoes harbored, how many mice were infected as a result of exposure to them, and how long it took the mice to develop malaria.
The team also analyzed data from human volunteers who were exposed to bites from infectious mosquitoes.
Dissection of these mosquitoes revealed that infection was significantly more likely—and occurred sooner—after bites from mosquitoes with more than 1000 individual parasites in their salivary glands.
By conducting further studies with mice and human volunteers, the researchers were able to provide an explanation for why the malaria vaccine RTS,S is effective only some of the time and why any protection rapidly drops off after 3 years.
The vaccine was less effective when mice or humans were bitten by mosquitoes carrying a greater number of parasites. The researchers think this is because the vaccine can only kill a certain proportion of the parasites and is overwhelmed when the parasite population is too large.
“Vaccine development has come a long way, and this new insight should help future vaccine studies to be tested more rigorously,” said study author Thomas Churcher, PhD, of Imperial College London.
“However, in the end, it is unlikely that one magic bullet will eradicate malaria, and we should continue to seek and apply combinations of strategies for reducing the burden of this disease.”
Photo by James Gathany
Mosquitoes carrying a greater number of malaria-causing parasites may be more likely to cause infection, according to a study published in PLOS Pathogens.
More than 100 years have passed since scientists first discovered that infectious mosquitoes inject malaria parasites when they bite people.
However, it hasn’t been clear whether injecting more parasites with each bite increases a person’s chances of infection or if all infectious bites are equally dangerous.
In the new study, researchers set out to determine whether the number of parasites found in the salivary glands of malaria-carrying mosquitos impacts disease transmission.
Via experiments in mice, the team determined that the more parasites present in a mosquito’s salivary glands, the more likely it was to be infectious and the faster an infection would develop.
“It is surprising that the relationship between parasite density and infectiousness has not been properly investigated before, but the studies are quite complex to carry out,” noted Andrew Blagborough, PhD, of Imperial College London in the UK.
For this study, he and his colleagues set up repeated cycles of infection so that groups of infected mosquitoes containing variable numbers of parasites repeatedly bit sedated mice, transmitting malaria to them under a range of transmission settings.
This allowed the researchers to track how many individual parasites different mosquitoes harbored, how many mice were infected as a result of exposure to them, and how long it took the mice to develop malaria.
The team also analyzed data from human volunteers who were exposed to bites from infectious mosquitoes.
Dissection of these mosquitoes revealed that infection was significantly more likely—and occurred sooner—after bites from mosquitoes with more than 1000 individual parasites in their salivary glands.
By conducting further studies with mice and human volunteers, the researchers were able to provide an explanation for why the malaria vaccine RTS,S is effective only some of the time and why any protection rapidly drops off after 3 years.
The vaccine was less effective when mice or humans were bitten by mosquitoes carrying a greater number of parasites. The researchers think this is because the vaccine can only kill a certain proportion of the parasites and is overwhelmed when the parasite population is too large.
“Vaccine development has come a long way, and this new insight should help future vaccine studies to be tested more rigorously,” said study author Thomas Churcher, PhD, of Imperial College London.
“However, in the end, it is unlikely that one magic bullet will eradicate malaria, and we should continue to seek and apply combinations of strategies for reducing the burden of this disease.”