Surreal image of sheep grazing on parasitic worms, symbolizing albendazole resistance.

Is Your Dewormer Really Working? Unveiling the Truth About Albendazole Resistance

Soraya Malik in Health & Wellness November 2025 • 4 min read.

"A Deep Dive into a Slow-Release Capsule's Fight Against Resistant Worms, and What It Means for Your Livestock"

Anthelmintic resistance is a growing global problem that significantly impacts livestock farming. Traditional methods of parasite control are becoming less effective, prompting the need for innovative solutions. Researchers and farmers alike are exploring novel compounds, combination treatments, advanced delivery systems, and even vaccinations to combat this challenge and ensure the profitability and sustainability of livestock operations.

One promising approach is the use of controlled-release capsules (CRCs) designed to extend the duration of anthelmintic drugs, potentially reducing treatment frequency and labor costs. However, questions remain about their effectiveness against resistant parasites and their impact on the development of further resistance.

This article delves into a study conducted in South Africa that investigated the efficacy of a slow-release albendazole capsule against Haemonchus contortus, a common gastrointestinal worm in sheep, with known resistance to multiple anthelmintics, including albendazole. We'll explore the study's findings, their implications for livestock management, and what they mean for the future of parasite control.

The Albendazole Resistance Crisis: Are We Losing the War Against Worms?

Surreal image of sheep grazing on parasitic worms, symbolizing albendazole resistance.

The study aimed to evaluate the effectiveness of a controlled-release albendazole capsule (CRC) in sheep infected with a resistant strain of Haemonchus contortus. This particular strain had previously demonstrated resistance to multiple anthelmintics, making it a significant challenge to control. The research was structured as a controlled field efficacy study, comparing the CRC treatment against both positive (single-dose albendazole) and negative (untreated) control groups. Researchers monitored faecal egg counts (FEC), FAMACHA® scores (anemia scoring), conception rates, and weight gains over a period of three and a half months.

The results of the study were surprising and concerning. The CRC treatment did not demonstrate any significant advantage in reducing faecal egg counts compared to the control groups. In fact, the use of the CRC was associated with decreased weight gain in the treated animals compared to the untreated controls. This finding raises questions about the potential negative impacts of CRC use in situations where anthelmintic resistance is already present.

Here’s a breakdown of the key findings:

No Advantage in Faecal Egg Count Reduction: CRCs did not outperform traditional albendazole treatments or no treatment at all in reducing worm egg counts.
Reduced Weight Gain: Sheep treated with CRCs actually gained less weight than those in the control group.
Limited Impact on Anemia: FAMACHA® scores, which indicate anemia levels due to worm infection, were similar across all groups.

These findings challenge the assumption that slow-release anthelmintics are a universally beneficial solution for parasite control, particularly in the face of existing resistance. The study highlights the complex interplay between drug efficacy, parasite resistance, and animal health, underscoring the need for a more nuanced approach to livestock management.

Moving Forward: Rethinking Parasite Control Strategies

The study's conclusion emphasizes the potential risks associated with using slow-release albendazole capsules in environments where severe anthelmintic resistance is prevalent. Instead of providing a solution, this approach could inadvertently worsen the problem by selectively promoting the survival and reproduction of resistant worms, without offering tangible benefits to the treated animals. A comprehensive and integrated approach is needed, including responsible drug use, FAMACHA scoring and strategic culling.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.4102/jsava.v84i1.1000, Alternate LINK

Title: The Efficacy Of A Slow-Release Albendazole Capsule Against ≪I≫Haemonchus Contortus≪/I≫ With Known Resistance To Albendazole

Subject: General Veterinary

Journal: Journal of the South African Veterinary Association

Publisher: AOSIS

Authors: Alan D. Fisher, Sybrand J. Van Sittert

Published: 2013-12-03

Everything You Need To Know

Why is anthelmintic resistance a growing problem in livestock farming?

Anthelmintic resistance is a growing concern in livestock farming because it reduces the effectiveness of traditional deworming methods. This resistance means that common drugs like albendazole may no longer kill the targeted parasites, leading to continued infection, reduced productivity, and economic losses for farmers. Innovative solutions are needed to combat this challenge and ensure the profitability and sustainability of livestock operations.

What is a controlled-release capsule (CRC), and how is it intended to work for deworming livestock?

A controlled-release capsule (CRC) is designed to release an anthelmintic drug, such as albendazole, slowly over an extended period. The idea behind a CRC is to prolong the drug's exposure to the parasite, potentially reducing the frequency of treatments and labor costs. However, the study indicates that CRCs might not be effective in areas with high anthelmintic resistance and could even have negative impacts, such as reduced weight gain in treated animals. More research is needed to fully understand their utility and risks.

What specific parasite was the focus of this study, and what were the main findings regarding the effectiveness of controlled-release albendazole capsules against it?

The study focused on Haemonchus contortus, a common gastrointestinal worm in sheep. This particular parasite strain had developed resistance to multiple anthelmintics, including albendazole. The findings indicated that controlled-release albendazole capsules (CRCs) did not effectively reduce faecal egg counts (FEC) in sheep infected with this resistant strain. Moreover, treated animals exhibited decreased weight gain compared to untreated controls, suggesting that CRCs may not be a viable solution for controlling resistant Haemonchus contortus.

What are FAMACHA® scores, and what did the study reveal about the impact of controlled-release albendazole capsules on these scores?

FAMACHA® scores are used to assess the level of anemia in livestock, which is often a result of Haemonchus contortus infections. In the study, FAMACHA® scores were similar across all groups (those treated with controlled-release albendazole capsules, those treated with single-dose albendazole, and the untreated control group). This suggests that the controlled-release albendazole capsules did not offer a significant advantage in reducing anemia caused by worm infections compared to traditional treatment or no treatment at all. Strategic FAMACHA scoring can still be useful as part of a comprehensive parasite control program by identifying animals in need of targeted treatment.

What are the implications of this study for future parasite control strategies in livestock, particularly concerning the use of controlled-release albendazole capsules?

The study suggests that using controlled-release albendazole capsules (CRCs) in environments with severe anthelmintic resistance may not be a beneficial strategy. Instead of solving the problem, CRCs might exacerbate it by selectively promoting the survival and reproduction of resistant worms, without providing tangible benefits to the treated animals. A comprehensive and integrated approach to parasite control is needed, including responsible drug use, strategic FAMACHA scoring, and selective culling of highly susceptible animals, as this will better mitigate the problem.