Infectious Disease

Ivermectin stops the spread of river blindness and could stop the West Nile virus from spreading

November 24, 2021

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Eigege and Holcomb do not report any relevant financial information.

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While not recommended for treating COVID-19, ivermectin has shown the potential to stop the spread of some infectious diseases, according to several studies presented at the American Society of Tropical Medicine and Hygiene’s annual meeting.

One study looked at the use of ivermectin to stop the spread and transmission of West Nile virus.

Kahansim B. et al.  Abstract 0432. Presented at: Annual Meeting of the American Society of Tropical Medicine & Hygiene;  17.-21.  November 2021;  virtual.

Kahansim B. et al. Abstract 0432. Presented at: Annual Meeting of the American Society of Tropical Medicine & Hygiene; 17.-21. November 2021; virtual.

“This study was developed as an investigation of a novel strategy to combat the West Nile virus”, Karen Holcomb, PhD, a recent graduate from the University of California, Davis, told Healio.

She noted that West Nile virus is still the leading cause of mosquito-borne diseases in the US and that current mosquito control strategies are unfortunately limited to reduce virus transmission.

“Ivermectin’s mosquito-killing properties, which work differently than currently used insecticides, and its well-documented history of safe use in mammals and birds make ivermectin a promising alternative control strategy,” said Holcomb.

Treat birds to kill mosquitoes

Holcomb and colleagues hypothesized that treating birds that are frequently fed by mosquitoes could reduce West Nile virus transmission by killing mosquitoes before they have another blood meal, thus preventing future infections. Ivermectin is deadly to mosquitoes but not to birds.

To evaluate the effectiveness and feasibility of this strategy, Holcomb and colleagues first placed 48 chickens in four treated and four untreated control flocks in backyard stalls across Davis, California, and administered ivermectin to the treated flocks daily between July and September 2019 in the study they monitored Serum ivermectin levels and tested all chickens for antibodies to West Nile virus.

Overall, the study showed that West Nile virus seroconversions were reduced in treated herds compared to untreated herds, suggesting a decreased transmission intensity in treated pens. Holcomb said subsequent modeling suggested that the use of ivermectin-treated bird feeders could reduce the bite of West Nile virus infected mosquitoes within a neighborhood by more than 60%. The results also showed that treating birds that are frequently fed by mosquitoes resulted in the greatest reductions, regardless of the species’ ability to transmit West Nile virus to feeding mosquitoes, she said.

“Ivermectin treatment of backyard birds with special birdseed is still under development and has the potential to significantly reduce local transmission of the West Nile virus in the future,” said Holcomb. “Large reductions require high spatial coverage of a neighborhood with ivermectin-treated bird feeders and a high mosquito death rate after biting a bird that has self-treated on a treated bird feeder.”

Eliminate river blindness

Additional data presented at the meeting indicated that mass treatment with ivermectin eliminated the transmission of river blindness in two states in Nigeria.

According to the study, the states of Plateau and Nasarawa were named as the first Nigerian countries to interrupt transmission and stop mass administration of drugs for onchocerciasis or river blindness after 8 to 26 years of mass administration with ivermectin. Researchers performed a 3-year post-treatment entomological assessment during the 2019-2020 transmission season, which is required to explain the elimination of transmission.

For the evaluation, the researchers collected and tested black flies for the presence of the L3 infection state of Onchocerca volvulus using O-150-PCR.

The evaluation resulted in 93 pools in the state of Nasarawa, consisting of 7,925 flies found and zero positive pools (95% CI, 0% -0.024%). Similar results were observed in Plateau State, where 89 pools out of 7,368 flies resulted in 0 positive pools (95% CI, 0% -0.026%).

According to the study, the results meet the WHO’s 2016 entomological criteria for eliminating the transmission infectivity threshold of less than 0.05%.

“It’s been 25 years of hard work by community volunteers to distribute the drug, and a particularly strong commitment from the Nigerian Federal Ministry of Health, the ongoing Ivermectin donation from Merck, and many donors and partners.” Abel Own, a program director for the Carter Center in Nigeria said in a press release. “But we hope this success can accelerate elimination efforts elsewhere in Nigeria and across Africa.”

References:

Kahansim B. et al. Abstract 0432. Presented at: Annual Meeting of the American Society of Tropical Medicine & Hygiene; 17.-21. November 2021; virtual.

Nguyen C. et al. Abstract 1351. Presented at: American Society of Tropical Medicine & Hygiene Annual Meeting; 17.-21. November 2021; virtual.

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American Society for Tropical Medicine and Hygiene (ASTMH)

American Society for Tropical Medicine and Hygiene (ASTMH)

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