Methods and Devices for Detection and Diagnosis of Malaria
Malaria is a debilitating, infectious disease characterized by chills, shaking and periodic bouts of intense fever. Each year, there are an estimated 400 million to 600 million cases of malaria and 2.7 million resulting deaths, worldwide. Malaria is found in many locations of the tropical world and in some locations of the subtropics. Each year, travelers who visit malarious countries return home and are hospitalized with malaria. Malaria was the number one cause of hospitalization among American troops deployed to Somalia; the number two cause among troops in Vietnam (after combat injury); and a leading cause among diplomats, missionaries and aid workers. Malaria transmission in the United States was largely eliminated during the mid-20th century; however, sporadic cases of locally acquired mosquito-transmitted malaria continue to occur. During August 2002, two northern Virginia teenagers were diagnosed with malaria, despite having no risk factors such as international travel. Malaria case numbers are increasing markedly in many third world countries for several reasons including the cessation of malaria vector control programs. Mosquitoes are the vectors – or intermediate carrier of the parasite that causes malaria. Vector controls are aimed at reducing the mosquito population and preventing their access to humans. However, financial obstacles limit the success of this effort in many developing countries. Insecticides are expensive and increasingly unsuccessful in killing mosquitoes that are developing resistances to the various chemicals. Antibiotics can be used as a preventative and a treatment. Unfortunately, drug resistance is becoming an alarming problem and contributes to uncontrollable outbreaks. Drug resistance is often connected with a legacy of foolishly overusing or under dosing antimalarial drugs. Expense is, again, an issue.
With continuous, affordable surveillance to promptly diagnose new cases and monitor tolerable, base line levels in people endemic to areas of high infection, it would be possible to administer appropriate treatment. Eventually, malaria could be eliminated. Researchers at The Johns Hopkins Applied Physics Laboratory (JHU/APL) and The Bloomberg School of Public Health have developed an in vitro method of detecting very low levels of the malaria-causing parasite, Plasmodium, in the blood. The researchers capitalize on the parasites requirement to use the only red blood cell proteins available, hemoglobin, to synthesize its own proteins. When hemoglobin is broken down, a byproduct called heme must be sequestered by Plasmodium inside the red blood cells. If the heme were permitted to float around, it would kill the parasite. Heme exhibits a distinct direct ultraviolet lasers desorption time-of-flight mass spectrometry (TOF-MS) signature and increases in the heme signal are directly proportional to levels of parasite infection. This very efficient tool for detecting levels of parasite infection is made more promising due to the advances in laser desorption TOF-MS which have enhanced the prospects for field-deployed, robust, automated and miniaturized detection systems. The Hopkins technique, within minutes, unambiguously detects as few as 10 parasites per micro liter of blood using a 50 micro liter sample. Current methods need 1 milliliter of blood; an hour and can only detect levels of infection on the order of 100 parasites per micro liter. Increases in the sensitivity by an order of magnitude are predicted with continued development. Our scientists further confirm tests for malaria detection by utilizing a computer controlled, digital microscope to generate electronic images of specific percentages of a blood smear. These images can be remotely or directly analyzed with an algorithm that detects parasites based on optical characteristics. Research is ongoing and funded.
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