A way to combat malaria
Here’s an interesting article on microbial antagonism, and the malaria parasite. Malaria is a disease that affects hundreds of millions annually, leading to upwards of a million deaths each year mostly in sub-Saharan Africa. Despite the tremendous loss of life, it is a disease that little progress has been made in developing truly novel approaches for eradication. Even today, the best approach for elimination is not the development of a vaccine, but rather the wholesale drainage of wetlands. In fact, there is serious conjecture that rising sea levels and moderation of global temperatures will make much larger populations at risk for endemic malaria in temperate climates.
Malaria is a classic vector-borne disease, and transmission of the disease is dependent on mosquitoes biting an infected host, and transferring the pathogen to a susceptible host. The main approach for prevention then relies on mosquito control, and these measures have historically been successful in North America, however there are a number of locations such as central Asia and the Far East where malaria is making a resurgence.
Considering this dire outlook, novel approaches for combating the disease are essential. The Science Daily summary discusses a very recent report from Johns Hopkins University and published in the journal Science. Researchers characterized the microbial flora of the Anapholes mosquito that transmits malaria. Like humans, mosquitoes possess a complex set of organisms that inhabit their guts in the absence of disease. One such bacterium isolated from the mosquito is from genus Enterobacter, which belongs to the family of Enterobacteriaceae.
What makes this species of Enterobacter significant is that it is able to inhibit the growth of Plasmodium, after the parasite is taken up into the gut of a mosquito when it feeds. The bacterium appears to stimulate the insect’s immune system to produce free oxygen radicals, or forms of oxygen which are highly reactive with biological molecules. Oxygen radicals are used by cellular aspects of the immune response to kill pathogens. These free radicals are highly effective, and can inhibit the growth of Plasmodium up to 99 percent both in the test tube as well as in the mosquito.
This offers an interesting way to combat malaria. Transmission of the disease requires the vector (the mosquito) to transmit the etiologic agent (Plasmodium) from the infected host to the susceptible host. Control measures for malaria work to block the vector, which blocks transmission. Here, the ability of the vector to become infected by the etiologic agent is blocked, which in turn blocks the transmission to the susceptible host. A potential control measure now would be to spread Enterobacter throughout the mosquito population, rendering the vector resistant to infection by Plasmodium.
Of course, all rosy scenarios likely have drawbacks. The abstract of this article doesn’t give the specific strain of Enterobacter isolated from the mosquitoes, however this link describes the isolation of a pathogenic strain of Enterobacter sakazakii from stable flies, so it seems possible that spreading another species of Enterobacter could lead to increased foodborne diseases.