MSD Animal Health Launches First Systemic Treatment for Poultry Red Mites; EXZOLT® Eliminates Infestations in European Poultry Houses

Novel Approach Improves Poultry Welfare by Reducing Stress on Chickens

MADISON, NJ, September 5, 2017 – MSD Animal Health (known as Merck Animal Health within the United States and Canada) today announced the launch of EXZOLT® (fluralaner), the first systemic treatment for poultry red mite infestations – a novel approach that virtually eliminates poultry red mites in production houses of any size or type, including free range. Conveniently administered via drinking water, EXZOLT also improves poultry welfare by reducing stress associated with other forms of treatment, and minimizes the exposure of workers and birds to chemical sprays.

“Poultry red mites are among the most threatening pests in Europe, contributing to increased stress levels, decreased weight gain and diminished egg quality and production in infested birds,” says Dr. Taylor Barbosa, DVM, PhD, ACPV, Head of Poultry, MSD Animal Health. “It is important to effectively treat poultry red mites as infestations not only affect the birds’ welfare, but also result in significant economic losses for poultry producers.”

Poultry red mites are a top five cause of economic loss in European layer and breeder operations and in many other countries, as infestations cause significant stress to poultry, decrease reproductive potential in males, egg production in females and weight gain in young birds.i  The total annual cost of poultry red mite infestations in the  European egg laying industry is estimated  to be €360 million, with more than 430 million hens in all production types – pullets, breeders and layer hens – suffering from infestations.

Poultry red mites are nocturnal feeders that hide during the day under manure, on roosts and in cracks and crevices in the chicken house, where they lay eggs, making them difficult to eliminate. Previously available treatment options are labor-intensive and/or have achieved limited success in eliminating or controlling infestations.  Mite infestations affect poultry workers as well, causing gamasoidosis, a skin condition characterized by rash and itching.

The safety of EXZOLT has been established through comprehensive clinical research studies. These studies demonstrated that EXZOLT virtually eliminates poultry red mites in production houses, and is safe for the birds and for human handling. No significant adverse events were reported.

“With a zero day withdrawal period, eggs from chickens treated with EXZOLT are safe to consume, making EXZOLT ideal for maintaining the health, performance and welfare of flocks while continuing to meet market demands and avoiding economic loss for producers,” adds Dr. Barbosa.


EXZOLT®, a first-of-its-kind product based on the fluralaner molecule for the treatment of poultry red mite infestations, works on the parasites’ nervous system and kills mites that have taken a blood meal, while remaining safe for the host animal. Chickens are treated during an infestation. This ensures that both adult mites and their eggs are killed.

Clinical data from three European dose-confirmation studies and an extensive nine-site field study showed EXZOLT provided virtual elimination of poultry red mite populations in all treated layer, breeder and/or pullet houses.

In these studies, the recommended EXZOLT dosage regimen (0.5 mg/kg body weight twice at a seven-day interval) achieved 99 percent mite-killing efficacy for at least 15 days, which spans two mite life cycles. EXZOLT starts working in mites within four hours after mites start to feed on treated chickens resulting in effective elimination of the mites.

About MSD Animal Health

For more than a century, MSD, a leading global biopharmaceutical company, has been inventing for life, bringing forward medicines and vaccines for many of the world’s most challenging diseases. MSD Animal Health, known as Merck Animal Health in the United States and Canada, is the global animal health business unit of MSD.Through its commitment to the Science of Healthier Animals™, MSD Animal Health offers veterinarians, farmers, pet owners and governments one of the widest range of veterinary pharmaceuticals, vaccines and health management solutions and services. MSD Animal Health is dedicated to preserving and improving the health, well-being and performance of animals. It invests extensively in dynamic and comprehensive R&D resources and a modern, global supply chain. MSD Animal Health is present in more than 50 countries, while its products are available in some 150 markets. For more information, visit or connect with us on LinkedIn.

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This news release of Merck & Co., Inc., Kenilworth, N.J., USA (the “company”) includes “forward-looking statements” within the meaning of the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995. These statements are based upon the current beliefs and expectations of the company’s management and are subject to significant risks and uncertainties. If underlying assumptions prove inaccurate or risks or uncertainties materialize, actual results may differ materially from those set forth in the forward-looking statements.

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The company undertakes no obligation to publicly update any forward-looking statement, whether as a result of new information, future events or otherwise. Additional factors that could cause results to differ materially from those described in the forward-looking statements can be found in the company’s 2016 Annual Report on Form 10-K and the company’s other filings with the Securities and Exchange Commission (SEC) available at the SEC’s Internet site (
i Mites of poultry. Merck Veterinary Manual. Retrieved from