Community receives ivermectin for loiasis control.

Can a Simple Pill End a Neglected Tropical Disease?

Mira Elwood in Health & Wellness November 2025 • 4 min read.

"Ivermectin's surprising impact on loiasis and its implications for broader disease control."

Loiasis, caused by the parasitic worm Loa loa and transmitted by biting flies, threatens millions across West and Central Africa. Often overshadowed by better-known diseases, loiasis can lead to debilitating symptoms, including painful "Calabar swellings" and the unsettling migration of worms across the eye.

For years, communities in Loa loa-endemic regions have received annual doses of ivermectin, primarily to combat onchocerciasis (river blindness). Ivermectin is very effective for this purpose, but scientists and health officials have wondered if this widespread drug administration could also impact loiasis.

Now, a recent study published in PLOS Neglected Tropical Diseases sheds light on this question. Researchers investigated the effects of repeated ivermectin treatments on loiasis in Cameroon, revealing both promising benefits and persistent challenges for eliminating this neglected disease.

Ivermectin's Double Duty: What the Study Found

Community receives ivermectin for loiasis control.

The study, conducted across multiple community-directed treatment with ivermectin (CDTI) projects in Cameroon, compared loiasis infection rates in areas with and without ongoing ivermectin administration. The results revealed a significant trend:

In areas where ivermectin had been administered for several years, the prevalence and intensity of loiasis infection were noticeably lower compared to regions without such programs. Specifically, the number of individuals carrying Loa loa microfilariae (the larval stage of the worm) in their bloodstreams was reduced.

East Cameroon: In a non-CDTI district, loiasis prevalence was 29.3%. However, in a CDTI district with 10 rounds of ivermectin treatments, prevalence dropped to 16.0%.
Northwest Cameroon: After nine rounds of CDTI, loiasis prevalence decreased from 30.5% to 17.9%.
Southwest Cameroon: While the reduction wasn't statistically significant, likely due to already low pre-treatment levels, the trend still pointed towards a positive impact.

Importantly, the study also highlighted a crucial link between adherence to ivermectin treatment and infection rates. Individuals who consistently took ivermectin were significantly less likely to harbor microfilariae in their blood.

Remaining Hurdles and the Path Forward

While ivermectin shows promise in controlling loiasis, the study also underscores the challenges in achieving complete elimination. A significant portion of the population remains non-adherent to ivermectin treatment, potentially due to concerns about side effects – a major obstacle in achieving full disease control.

The researchers emphasize the need for alternative treatment strategies and improved adherence programs. This includes exploring therapies that target onchocerciasis without impacting Loa loa, and implementing “test and treat” strategies to identify and manage individuals at high risk of adverse reactions.

Ultimately, this research highlights the complex interplay between disease control efforts and the importance of understanding the multifaceted impact of interventions like mass drug administration. As the world strives to eliminate neglected tropical diseases, integrated approaches and community-centered solutions will be essential.

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This article is based on research published under:

DOI-LINK: 10.1371/journal.pntd.0006750, Alternate LINK

Title: Impact Of Repeated Annual Community Directed Treatment With Ivermectin On Loiasis Parasitological Indicators In Cameroon: Implications For Onchocerciasis And Lymphatic Filariasis Elimination In Areas Co-Endemic With Loa Loa In Africa

Subject: Infectious Diseases

Journal: PLOS Neglected Tropical Diseases

Publisher: Public Library of Science (PLoS)

Authors: Samuel Wanji, Winston Patrick Chounna Ndongmo, Fanny Fri Fombad, Jonas Arnaud Kengne-Ouafo, Abdel Jelil Njouendou, Yolande Flore Longang Tchounkeu, Benjamin Koudou, Moses Bockarie, Grace Fobi, Jean Baptiste Roungou, Peter A. Enyong

Published: 2018-09-18

Everything You Need To Know

What is loiasis?

Loiasis is a neglected tropical disease caused by the parasitic worm *Loa loa*. It is transmitted to humans through the bite of biting flies. The infection leads to symptoms such as painful "Calabar swellings" and the migration of worms across the eye. Understanding the life cycle of *Loa loa* and its mode of transmission is crucial for developing effective control strategies.

How does ivermectin help treat loiasis?

Ivermectin is a drug that has been found to be effective against both onchocerciasis and loiasis. It works by targeting the microfilariae, the larval stage of the *Loa loa* worm, in the bloodstream, reducing their numbers and, consequently, the disease's spread and severity. This dual-action capability makes ivermectin a valuable tool in regions where both diseases are prevalent.

What were the key findings of the study regarding ivermectin and loiasis?

The study revealed that the prevalence and intensity of *Loa loa* infection were noticeably lower in regions where ivermectin had been administered for several years through community-directed treatment with ivermectin (CDTI) programs. Specifically, the number of individuals carrying *Loa loa* microfilariae in their bloodstreams was significantly reduced, indicating ivermectin's effectiveness in controlling the disease.

What are CDTI programs and what is their significance in the context of this study?

CDTI refers to community-directed treatment with ivermectin programs. These programs involve the widespread administration of ivermectin within communities. The study highlighted a significant link between adherence to ivermectin treatment and infection rates. People who consistently took ivermectin were less likely to harbor *Loa loa* microfilariae. This underscores the importance of community participation and adherence in disease control efforts.

What are the main challenges in controlling loiasis, even with the use of ivermectin?

While ivermectin shows promise, achieving complete elimination of loiasis faces challenges. Non-adherence to ivermectin treatment remains a significant obstacle. Reasons for non-adherence may include concerns about side effects. To overcome this, it is important to address these concerns and improve the effectiveness of drug delivery programs. Further research and comprehensive strategies are needed to address these challenges and achieve the goal of loiasis elimination.