The challenge model is also being used to evaluate an experimental vaccine for another strain of the malaria parasite, P. vivax, which is not as deadly as P. falciparum but, according to Paris, causes most of the cases of malaria in the U.S. military. P. vivax tends to “hibernate” in a person’s liver, causing the disease to recur or “relapse.” “Because of its biology,” Paris said, “P. vivax  presents the biggest hurdle for the elimination of malaria.” MMRP investigators today are among only a handful of scientists around the world developing an experimental P. vivax vaccine.

Mild to moderate malaria caused by P. falciparum and P. vivax is treated with oral drugs. When P. falciparum developed resistance to the classic agent chloroquine at the time of the Vietnam War, WRAIR was called on to urgently deliver a new malaria prevention drug to maintain combat readiness of deployed troops and cure those who needed treatment. WRAIR scientists invented and then co-developed a new drug named mefloquine as a chloroquine replacement. As with all drugs, resistance emerged to mefloquine over time and WRAIR physicians and scientists played an important role in the FDA approval of the next-generation malaria prophylaxis drug malarone in 2000. There are more cases in the United States of P. vivax than P. falciparum. WRAIR clinical scientists developed primaquine in the 1940s-1950s to treat the hidden P. vivax parasite in the liver, and it is still used today. WRAIR invented the potential primaquine replacement, tafenoquine, that is in advanced clinical testing today.

Severe malaria is treated with intravenous drugs. Quinine is used worldwide, whereas quinidine is the only agent approved for use in the United States, although it can cause cardiac damage. For these reasons, WRAIR researchers and others have for some time focused on artemisinins. Artemisinins were widely used more than 2,000 years ago in traditional Chinese medicine, and were redeveloped by the Chinese government to treat North Vietnamese soldiers during the Vietnam War – at about the same time WRAIR researchers were developing mefloquine for U.S. troops. In the 1980s, WRAIR scientists found sweet wormwood growing on the banks of the Potomac River, extracted artemisinins, and began studying them. One of the most promising compounds to be studied by the group, artesunate, is a semi-synthetic artemisinin derivative that is water soluble and deliverable intravenously (IV). A team of WRAIR researchers led by Dr. Qigui Li and Col. Peter J. Weina, M.D., recently published that patients with severe malaria who received IV artesunate were 35 percent less likely to die than those treated with quinine. WRAIR and U.S. Army Medical Materiel Development Activity (USAMMDA) have for a decade been engaged in an effort to replace quinidine with IV artesunate in the United States. In 2007, the FDA approved the use of IV artesunate as an investigational new drug to treat severe malaria in the United States, making the compounds available in the United States for the first time.

It is better to prevent malaria than to have to treat it. The three drugs used today as malaria prophylaxis are doxycycline, found to be effective in the 1980s by scientists working at the WRAIR laboratory in Thailand; malarone; and mefloquine. The leading candidate for a new prophylactic agent is the WRAIR drug tafenoquine, now being developed for prevention by the USAMMDA at the U.S. Army Medical Research and Materiel Command.

 

The Leishmania Diagnostics Laboratory

WRAIR is the only institution in the world focused on developing new drugs for the prevention of malaria in healthy adults – and it is home to the only certified laboratory in the United States specializing in another vector-borne parasitic disease: leishmaniasis.

WRAIR is the only institution in the world focused on developing new drugs for the prevention of malaria in healthy adults – and it is home to the only certified laboratory in the United States specializing in another vector-borne parasitic disease: leishmaniasis. Protozoans of the genus Leishmania, delivered by the bite of certain species of sand flies, attack hosts in two ways: The more common cutaneous form of leishmaniasis (CL) creates skin lesions that can be difficult to treat and may cause permanent scarring or damage a patient’s mucous membranes; in the potentially fatal visceral leishmaniasis (VL), the parasite migrates to the internal organs and bone marrow.