Dr. Thomas Unnasch receives $2.6M NIH grant to examine river blindness

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USF College of Public Health’s Dr. Thomas Unnasch, chair of the Department of Global Health and distinguished university health professor, has been awarded an R01 grant for more than $2.6 million from the NIH’s National Institute of Allergy and Infectious Diseases to combat onchocerciasis in Africa.

Onchocerciasis, commonly known as river blindness, is an eye and skin disease spread by the filarial parasite Onchocerca volvulus, a type of worm that migrates below the skin and the eyes.

According to the Centers for Disease Control and Prevention, river blindness is categorized as a neglected tropical disease—diseases that cause substantial illness for more than one billion people globally, especially among those living in poverty.

The disease spread by the black fly, Similium damnosum, living near trailing vegetation immersed among river banks, according to Dr. Benjamin Jacob, research assistant professor in Global Health and co-principle investigator of the grant.

Onchocerca volvulus larvae, the cause of onchocerciasis, or “river blindness.” Onchocerca volvulus is transmitted to a human host through the bite of Similium damnosum, or “black flies.” (Photo courtesy of CDC/Dr. Lee Moore)

Those infected may experience skin rashes, large nodules under the skin—usually indicating the presence of adult worms living below the skin and, eventually, blindness.

According to the World Health Organization, onchocerciases is found commonly in inter-tropical zones, with about 90 percent of cases occurring in Africa.

Adults infected by Onchocera volvulus may take ivermectrin to destroy the larvae living in the body, however there is no treatment for children under five, due to toxicity. The blindness may be asymptomatic with long-term blindness typically not first showing signs until the child reaches his or her adolescent years, according to Jacob.

An elderly man in Uganda shows Dr. Jacob the nodules on his body from black fly bites. (Photo courtesy of Dr. Jacob)

“To me, this disease has become personal,” Jacob said. “You see a five-year-old child wearing the same dress everyday who lives with seven other kids, all eating out of a common pot, living with no shoes. In this region of Uganda, malaria, yellow fever, and other vector-borne diseases and very prevalent. And now, the children are at risk for blindness, that just doesn’t make any sense to me. It seems so unfair.”

The grant will focus on a community-directed vector control program, ‘Slash and Clear,’ to compliment current mass drug administration efforts in afflicted African communities.

According to Unnasch and Jacob, while almost all onchocerciasis elimination programs rely exclusively on mass distribution of ivermectin, it will not be sufficient enough to eliminate it globally by 2020, a goal outlined by the London Declaration on Neglected Tropical Diseases.

Dr. Jacob met with villagers in Uganda as they went about their daily tasks along the river. Simply carrying out daily routines, according to Jacob, puts the villagers, especially children, at great risk for infection as the flies have inundated the area. (Photo courtesy of Dr. Jacob)

“We’re trying to get away from big numbers coming through the door by preventing it and stopping the contact between the vector and the human,” Jacob said.

According to Jacob, they plan to implement a larval control system for black flies, driven by geographic information system (GIS) and remote sensing.

“We’re employing ArcGIS cartographic software in a cyber-environment system to determine areas of productivity of immature Similium damnosum for the purposes of reduction of the vector population through removal of targeted habitats within a 5 kilometer buffer of multiple agro-villages through  northern Uganda in ArcGIS, it’s very exciting,” he said.

During a pretrial tests of the system, Jacob said they were able to bring down the fly presence remarkably.

According to Jacob, during intervention trials in Gonycogo, an agro-village riverine tributary ecosystem in northern Uganda, the mean daily collection during the last three days of the 31 day study was 32.66, representing an 89.10 percent reduction in biting density from the mean collection in the baseline collection of 292.4 adult black flies.

In contrast, Jacob said, the mean daily collection in the paired control village of Ayago/Nile about 15 kilometers from Gonycogo village was essentially unchanged from the baseline collection during the last three days of the study—352.7 baseline versus 348.6 at the end of the study.

Similar results were seen in the other village pair, Jacob said.

An 81.21 percent reduction in biting rate was observed in the intervention village (Adbuk), while the biting rate in the control village (Laminlato) at the end of the study was 98.11 percent of that seen in the baseline evaluation.

This method, according to Jacob is more environmentally friendly and cost effective, and also builds a sustainable larval control method for villagers in the future.

“Traditional larvae control has relied on tactics with insecticides,” Jacob said. “Spraying is just not sustainable in these villages.”

Jacob, who has been working in this field of research for more than 10 years now, said black fly habitats were more productive among breaks in the riverine pathway along the river.

Using ArcGIS, he will be able to quickly pinpoint where those discontinuous canopied, breeding grounds are across different agro-villages in northern Uganda.

“Within GIS, I can determine where discontinuity of canopy occurs, based on Chlorophyll A, a canopy pigment,” he said.

Dr. Benjamin Jacob (far right) examines black fly breeding grounds in Uganda. (Photo courtesy of Dr. Jacob)

Using this method of removal via ArcGIS technology builds sustainability at the village level, Jacob said, because it enlists the assistance of local villagers to remove breeding grounds for the black fly.

Villagers will contribute to the elimination of onchoceriasis through clearing the trailing vegetation habitats based on an interpolated Chl-a, something he said they hope to do across numerous villages in northern Uganda and eventually other areas throughout other endemic countries in Africa.

“They [the villagers] know they are doing something to help their family members,” Jacob said. “This is not a hand out, it’s a hand up.”

The first year of the project began Dec. 2016 and will conclude in Nov. 2021.

By the end of the grant, Jacob said he hopes to have eradicated the black fly that causes this debilitating disease in northern Uganda.

“When you see the travesty, it’s different, it becomes personal,” he said.  “This has energized me.”

 

Story by Anna Mayor, USF College of Public Health

 

 

 

 

 

 

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