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.Īll malaria-affected regions will have a mix of mosquitoes carrying different parasite amounts. The vaccine was less effective when mice or humans were bitten by mosquitoes carrying a greater number of parasites. Vaccine development has come a long way, and this new insight should help future vaccine studies to be tested more rigorously. Vaccine developmentīy conducting further studies with mice and human volunteers, the team were also able to explain why the malaria vaccine RTS,S is effective only around 50 percent of the time, and why any protection rapidly drops off after three years. This allowed them to track how many individual parasites different mosquitoes harboured, how many mice were infected as a result of exposure to them, and how long it took the mice to develop malaria. The team 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. “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.” We have shown that the concept of relying on the number of bites alone to predict malarial burden is flawed, and has probably hampered the successful use of control measures and the development of effective vaccines. Study co-author Dr Andrew Blagborough, from the Department of Life Sciences at Imperial, said: “These findings could have significant implications for public health. In studies in mice, the researchers determined that the more parasites present in a mosquito’s salivary glands, the more likely it was to be infectious, and also the faster any infection would develop. Some mosquitoes can be ‘hyperinfected’, making them particularly likely to pass on the disease. Now, in a study funded by the PATH Malaria Vaccine Initiative and the Medical Research Council, published in the journal PLoS Pathogens, researchers have determined that the number of parasites each individual mosquito carries influences whether a person will develop malaria. Previous studies using needle-injected parasites have suggested this may not be the case, but there have been no comprehensive studies using biting mosquitoes, which more accurately reflect real-world scenarios. However, this does not take into account how infectious each of those bites may be – each bite is considered equally infectious. To determine the intensity of malaria transmission, researchers and international organisations like the World Health Organisation currently rely on a measure called the entomological inoculation rate (EIR): the average number of potentially infectious mosquito bites per person per year. Not every infectious mosquito bite will result in malaria. The parasites then travel to the liver, where they mature and multiply for 8-30 days before spreading throughout the bloodstream and causing the symptoms of malaria. We have shown that the concept of relying on the number of bites alone to predict malarial burden is flawed. These findings could have significant implications for public health.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |