Inside Texas Tech: Preventing One of the World's Deadliest Parasites

Aug 10, 2017

Dr. Afzal Siddiqui has toiled for more than two decades searching for a way to eliminate a devastating parasitic disease. Schistosomiasis has infected an estimated 200 million people in 78 countries. It’s found in many sub-Sarahan Africa countries and in Brazil and China. The Bill & Melinda Gates Foundation recently gave the internal medicine researcher a second grant, allowing him to continue his work on a vaccine for the disease. This grant, awarded last month, is for about $2.4 million dollars.

Siddiqui hopes to begin clinical trials on the vaccine in humans next year. He says it’s usually about five years after human clinical trials are completed before the vaccine is available for distribution. His initial Schistosomiasis grant from the Gates Foundation, in 2014 for about $3.1 million dollars, was the first ever for the health sciences center.

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Though not contagious, Schistosomiasis kills about two hundred thousand people a year. Malaria, the world’s deadliest parasitic disease, kills about a million. Siddiqui received a patent on the vaccine in 2015 and hopes to deliver it to those infected for $1 or less per dose.

Siddiqui said, “This is a pretty important disease it impacts mostly children and young adults because the way they get infected is that the parasite, the infection stage of the parasite is in water, where they have the snail. So those age groups from three to twelve year they have more contact with water and they get infected. And the parasite can live for decades”

The vaccine will prevent infections and treat existing ones. When infected, patients develop distended bellies due to the accumulation of the parasite’s eggs inside their bodies. They suffer fatigue and various gastrointestinal issues, including diarrhea. This recent grant allows Siddiqui and his colleagues to test the vaccine to ensure it remains stable over a period of time under specific conditions.

The first human trials will be in the US on people not infected to test for adverse effects. The next phase will be done in an African country on those infected. Because there is more than one strain of the parasite, Siddiqui worked to ensure the vaccine would be effective against all Schistosomiasis varieties.  

“Two major ones, they cause the disease of the liver and intestine and the third causes a urinary bladder disease which can lead to cancer also," he explained. "Some of them are distributed in different geographic areas and some of them overlap in Africa. So if you develop a vaccine against one parasite it’s not going to work because you have other parasites that will harm. So we spent many many years coming up with a vaccine that will protect against all major species of the parasite.” 

Siddiqui’s vaccine doesn’t target the parasite directly. Instead, it works by inhibiting the parasite’s ability to fend off the host’s immune system response.  The vaccine’s importance has increased because medicine that’s been used to treat Schistosomiasis for more than 40 years has grown resistant and is losing its effectiveness. That drug can help with infections but isn’t able to prevent re-infection.

The patent was important in order to keep the vaccine inexpensive. And out of the hands of those seeking to make a profit. According to Doug Golenbock with the Bill & Melinda Gates Foundation, "A vaccine for Schistosomiasis was thought to be unlikely but these results are exciting as they suggest feasibility - it could prove to be a transformational tool in our fight against this important neglected disease."