US poultry producers have a new, FDA-approved weapon in the fight against Northern fowl mite (NFM) with Exzolt™ (fluralaner oral solution), a pioneering treatment from Merck Animal Health.
Available in Europe and other markets for several years, the approval of Exzolt in the US marks the first FDA-approved pharmaceutical for treatment of NFM (Ornithonyssus sylviarum), a significant pest for US producers that impacts hen welfare and production.
“These parasites are responsible for a range of issues, including anemia, reduced egg quality and weight loss, which can impact animal welfare and the profitability of laying hen operations,” said Alison De Leon, VMD, a project leader within Merck Animal Health’s Global Pharmaceutical Development group.
“Getting approval and bringing Exzolt to US producers, who’ve previously relied on non-FDA approved alternatives like dusts and sprays to manage mite infestations, is very exciting.”
Practical and targeted treatment
Exzolt, known generically as fluralaner oral solution, is administered through birds’ drinking water. Treatment involves two doses, administered 7 days apart, aligning with the mite life cycle to ensure effective control.
This method of administration eliminates the need for labor-intensive application treatments like dusting or spraying, which can be difficult to apply evenly across large flocks.
“The convenience of drinking water treatment minimizes stress for the birds, which is important for their welfare,” De Leon added.
Fast-acting results
Producers can expect to see significant reductions in mite populations once Exzolt has been administered. Merck’s clinical trials showed that the product is highly effective, reducing NFM counts by more than 99% within the first 2 days of treatment.
“We saw dramatic reductions in mite numbers, with counts remaining at or near zero through day 28,” De Leon said. This not only demonstrates the product’s efficacy, but also its lasting impact.
To ensure the product’s long-term efficacy, De Leon said it was critical that producers follow the treatment schedule closely.
“The two doses, spaced 7 days apart, are necessary to cover the full life cycle of the mite. Skipping the second dose could compromise the treatment’s success, leading to the possibility of reinfestation as the mites’ eggs hatch and mature,” she explained.
Though no resistance has been observed, De Leon said that following the recommended dosage and schedule is crucial to prevent the potential for resistance.
“We haven’t seen resistance yet, but it’s always a theoretical concern with ectoparasites,” she said. “Producers who deviate from the recommended dosage or treatment schedule could inadvertently create conditions that promote resistance.”
Merck’s technical support team is available to guide producers on the correct use of the product, ensuring proper administration through drinking water systems and preventing under-dosing. As a prescription-only product, De Leon said producers should consult with their veterinarian and seek guidance from Merck’s technical staff, especially during first-time use.
Exzolt is prepared by diluting the concentrate according to the flock’s water consumption and administering it over 6 to 24 hours. Producers are advised to pre-calculate daily water intake and flush the water system after dosing to ensure uniform delivery throughout the house.
“Definitely, when you’re adopting this product, work with one of our technical staff to make sure everyone understands how it’s to be administered,” De Leon advised. “The label walks users through it, but it’s helpful to get some added guidance to be sure everything is delivered properly.”
De Leon confirmed that there are no seasonal restrictions on when Exzolt can be used – the product can be applied whenever a NFM infestation is diagnosed. However, she emphasized that producers should always consult their veterinarians for specific advice on how to use Exzolt based on their flock’s needs.
Robust clinical data
Merck’s rigorous clinical trials played a crucial role in securing FDA approval for Exzolt. Four studies were conducted in the US, including dose confirmation and field trials designed to reflect a variety of flock types and regional conditions.
The studies involved two smaller trials with 128 birds each, and two larger field trials each with 800 birds. In all trials, mite populations dropped rapidly and remained low throughout the 28-day observation period.
“To achieve FDA approval, we had to provide substantial evidence from multiple studies, including safety trials. This data confirmed that Exzolt does not affect the safety of poultry meat or eggs,” De Leon explained.
The product’s safety profile is further supported by the zero-day egg withdrawal period, ensuring no delay in egg production following treatment. In the US, there is an 11-day slaughter withdrawal period.
A timely solution for NFM
After successfully navigating the complex logistics of label finalization, manufacturing and importation, Exzolt is now available to US poultry producers.
As the US layer industry continues to evolve, particularly under pressure from welfare requirements and the reduction of insecticide options, Exzolt’s introduction provides a timely and scientifically backed solution for mite control.
“As the first FDA-approved tool producers have had for Northern fowl mite, it’s a big step forward,” De Leon said.
With growing consumer demand for sustainable poultry farming and stringent welfare standards, Exzolt offers US poultry producers a much-needed approach to control NFM effectively and conveniently.
“This is about improving bird comfort, supporting production and giving producers a new tool that’s both effective and convenient,” she added. “We’re excited to finally bring it to the US market.”
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