Studies: Ivermectin may stop spread of river blindness, West Nile virus

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The drug ivermectin, which has gained attention during the COVID-19 pandemic because of early hopes it could help combat the coronavirus, was shown in a new studies to help curb spread of river blindness, a disease spread by blackflies. Photo by U.S. Department of Agriculture/Wikipedia

Mass treatment with ivermectin, a drug that has become controversial during the COVID-19 pandemic, eliminates river blindness transmission and can reduce spread of West Nile virus, according to findings presented Thursday during the annual meeting of the American Society of Tropical Medicine and Hygiene.

The drug has effectively stopped the spread of river blindness in two states in Nigeria, Plateau and Nasarawa, the first Nigerian states to achieve this distinction in a country that has the world’s most cases of the disease, the researchers said.

The two states have a combined population of more than 5 million, they said.

“Nigeria is where the fight to eliminate river blindness will be won or lost,” presenter Dr. Abel Eigege said in a press release.

“We are hoping this success can accelerate elimination efforts elsewhere in Nigeria and throughout Africa,” said Eigege, a program director for the Carter Center in Nigeria.

River blindness, or onchocerciasis, is caused by tiny parasitic worms transmitted by infective bites from blackflies that breed in rapidly flowing rivers, according to the American Society of Tropical Medicine and Hygiene.

In humans, the worm’s embryonic larvae routinely produce eye lesions that can cause blindness, the society says.

The condition is found widely in Africa, and there are isolated pockets of disease in Brazil, Venezuela and Yemen, it says.

In a separate presentation, the Carter Center’s Dr. Emmanuel Emukah reported that there is also evidence that disease transmission has been “interrupted” in Nigeria’s Delta State, thanks in part to the use of ivermectin.

Interruption is a critical first step towards achieving elimination since it allows ivermectin treatments to be stopped, he said.

Four other Nigerian states may soon reach the interruption stage, according to Emukah.

One reason the campaigns have been embraced by people in local communities is that ivermectin has additional benefits in treating other afflictions they routinely suffer, including intestinal worms, scabies and lice, Eigege said.

Meanwhile, in a separate study at the annual meeting of the American Society of Tropical Medicine and Hygiene, researchers at the University of California, Davis and Colorado State University found that adding ivermectin to backyard bird feeders may reduce transmission of West Nile Virus.

West Nile Virus is transmitted to humans by mosquitoes, but birds serve as key amplifiers of the virus in nature, keeping it circulating in local mosquito populations.

“Widespread” use of ivermectin in backyard birdfeeders, however, reduced neighborhood transmission of the virus, the most common mosquito-borne disease in the United States, by up to 60%, co-author Karen Holcomb said in a press release.

“A low dose of ivermectin is harmless for birds, but it gets in their blood and can be lethal for mosquitoes that feed on them,” said Holcomb, a researcher at the University of California, Davis School of Veterinary Medicine.

The approach could help prevent or control local outbreaks like the one that led to more than 800 confirmed and probable cases in Arizona earlier this year and killed 67 people, she said.

Currently, no drugs cure West Nile virus infection or vaccines for humans to prevent the disease, which emerged across the country in 1999 and is now found in every state except Alaska and Hawaii.

Although the Food and Drug Administration ruled that ivermectin is safe and effective for the treatment of these conditions in humans, the agency has warned against using it for COVID-19.

Interest in using ivermectin for COVID-19 could divert supplies needed for proven uses, such as fighting river blindness, or for developing novel applications, including in malaria and West Nile Virus, according to Brian Foy, a professor of veterinary medicine at Colorado State University.

He already has experienced difficulty finding enough ivermectin for his work, he said.

“I understand that at the beginning of the pandemic, when we had nothing, it was valid to at least consider a drug like ivermectin because there was some evidence of general anti-viral properties,” Foy, who has been conducting research with the drug for 20 years, said in a press release.

“But we have vaccines and a growing number of proven treatments, yet the demand for ivermectin, which has no demonstrated benefit so far to treat COVID-19, seems to be growing,” he said.

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