AfreeAfrica Health Science


Science saves lives. Latest health discoveries from the World of Science
 


New Ways to Control Malaria

The emergence of drug-resistant malaria parasites and insecticide-resistant mosquito vectors necessitates the development of new methods to combat malaria. In their Perspective, Hemingway and Craig explore transmission-blocking therapies that aim to prevent transmission of the reproductive stages of the malaria parasite from the insect vector to the human host when the mosquito takes its next blood meal. As part of this endeavor, they discuss new work by Osta et al. that identifies three mosquito genes affecting the sexual development of the malaria parasite in the mosquito gut.


Natural Immunization Against Malaria: Causal Prophylaxis with Antibiotics


Malaria remains the most prevalent vector-borne infectious disease and has the highest rates of fatality. Current antimalarial drug strategies cure malaria or prevent infections but lack a sustained public health impact because they fail to expedite the acquisition of protective immunity. We show that antibiotic administration during transmission of the parasite Plasmodium berghei results in swift acquisition of long-lived, life cycle–specific protection against reinfection with live sporozoites in mice. Antibiotic treatment specifically inhibits the biogenesis and inheritance of the apicoplast in Plasmodium liver stages, resulting in continued liver-stage maturation but subsequent failure to establish blood-stage infection. Exponential expansion of these attenuated liver-stage merozoites from a single sporozoite induces potent immune protection against malaria. If confirmed in residents of malaria-endemic areas, periodic prophylaxis with safe and affordable antibiotics may offer a powerful shortcut toward a needle-free surrogate malaria immunization strategy.


Malaria Mosquito 3 times more eager for smelly socks than non infected mosquitoes


To the malaria-carrying mosquito Anopheles gambiae (pictured), the stench of human feet is like the smell of a fresh-baked pie. A team of entomologists set out to see if the bugs were even more drawn to the odor when infected with the malaria parasite. Lead researcher and entomologist Renate Smallegange collected the smell using her own feet—with a nylon stocking that she wore for about 20 hours. She and her colleagues then exposed the stocking to caged mosquitoes, allowing them to land on it and poke it with their proboscises in a vain attempt to feed. It turned out that malaria-infected mosquitoes are about three times more likely to be attracted to the smell of human feet than their uninfected counterparts, the researchers report today in PLOS ONE. But the stink of human body odor comes from a soup of many chemicals, making it hard to tell just which odor the mosquitoes love. So the team plans to attach tiny electrodes to mosquito antennae, which they use to smell, and test them against individual body chemicals. They hope their findings will help scientists build better traps in the wild that will draw only infected mosquitoes.


Development of Transgenic Fungi That Kill Human Malaria Parasites in Mosquitoes

Metarhizium anisopliae infects mosquitoes through the cuticle and proliferates in the hemolymph. To allow M. anisopliae to combat malaria in mosquitoes with advanced malaria infections, we produced recombinant strains expressing molecules that target sporozoites as they travel through the hemolymph to the salivary glands. Eleven days after a Plasmodium-infected blood meal, mosquitoes were treated with M. anisopliaeexpressing salivary gland and midgut peptide 1 (SM1), which blocks attachment of sporozoites to salivary glands; a single-chain antibody that agglutinates sporozoites; or scorpine, which is an antimicrobial toxin. These reduced sporozoite counts by 71%, 85%, and 90%, respectively. M. anisopliae expressing scorpine and an [SM1]8:scorpine fusion protein reduced sporozoite counts by 98%, suggesting that Metarhizium-mediated inhibition of Plasmodium development could be a powerful weapon for combating malaria.



Diarrhea (MSD) 8 1/2 times more deadly, 4 pathogens(factors) causes it, one of them a parasite seen in HIV positive patients 


Every year, 800,000 children under age 5 living in the developing world die from a disease that's usually considered a mere annoyance in the West—diarrhea. But until now, there's been very little reliable data on the microbes behind all this mortality, as well as their precise effects on children's health around the world. In order to fill in these knowledge gaps, a team of scientists spent 3 years studying diarrheal diseases at seven sites in south Asia and Africa. The results were sobering: children with moderate-to-severe diarrhea (MSD) were 8.5 times more likely to die within 60 days than children not suffering from MSD, the researchers report today in The Lancet. What's more, children who survived their bout with MSD showed signs of stunted growth that could impair their future development. On a microbial level, the team was surprised to discover that a majority of childhood MDS cases were caused by only four pathogens: rotavirus (pictured), the parasite Cryptosporidium, a strain of the Escherichia coli bacteria known as ST-ETEC, and the bacteria Shigella. The fact that rotavirus tops the list is actually good news, since efforts are already underway to vaccinate at-risk children against the virus. But the appearance of the Cryptosporidium is more troubling—scientists had no idea the parasite, which is usually seen in HIV-positive patients, was causing so many cases of childhood MSD. They hope this new study will fast-track much needed research about how to protect against this under-studied bug


High Coverage of ART Associated with Decline in Risk of HIV Acquisition in Rural KwaZulu-Natal, South Africa



The landmark HIV Prevention Trials Network (HPTN) 052 trial in HIV-discordant couples demonstrated unequivocally that treatment with AntiretRoviral Therapy (ART) substantially lowers the probability of HIVtransmission to the HIV-uninfected partner. However, it has been vigorously debated whether substantial population-level reductions in the rate of new HIV infections could be achieved in "real-world" sub-SaharanAfrican settings where stable, cohabiting couples are often not the norm and where considerable operational challenges exist to the successful and sustainable delivery of treatment and care to large numbers of patients. We used data from one of Africa's largest population-based prospective cohort studies (in rural KwaZulu-Natal, South Africa) to follow up a total of 16,667 individuals who were HIV-uninfected at baseline, observing individual HIV seroconversions over the period 2004 to 2011. Holding other key HIV risk factors constant, individual HIV acquisition risk declined significantly with increasing ART coverage in the surrounding local community. For example, an HIV-uninfected individual living in a community with high ART coverage (30 to 40% of all HIV-infected individuals on ART) was 38% less likely to acquire HIV than someone living in a community where ART coverage was low (<10% of all HIV-infected individuals on ART).

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