FDA Working with Stakeholders to Maintain Effectiveness of Livestock and Horse Dewormers
December 6, 2018
The U.S. Food and Drug Administration
announced today that it has requested that animal drug companies
voluntarily revise the labels of drugs intended to treat certain
internal parasites in livestock and horses to add information about
antiparasitic resistance. This move comes as a result of the agency’s
work with veterinary parasitology experts and the animal health
community to find ways to maintain the effectiveness of these drugs. The
requested labeling changes are for approved antiparasitic animal drug
products only, and do not relate to antimicrobial drug products or
antimicrobial resistance.
The requested labeling changes
specifically affect anthelmintics for livestock (cattle, sheep, goats,
poultry, and swine) and horses. Anthelmintics, often called dewormers,
are animal drugs that treat helminths. Helminth refers to several groups
of internal parasites, often called worms, that have some similarities.
Tapeworms and roundworms are common types of helminths. Helminths are
becoming increasingly resistant to drugs that were generally effective
against them in the past. In these situations, after an animal is
treated with a dewormer, the susceptible worms die and the resistant
worms survive to pass on resistance genes to their offspring.
Although
antiparasitic resistance in livestock and horses does not directly
affect human health in the U.S., it is a growing animal health threat in
this country. Heavy worm infections can cause diarrhea, weight loss,
anemia (decreased level of red blood cells), and death. Antiparasitic
resistance is particularly concerning in grazing species (cattle, sheep,
goats, and horses), but is also a problem in swine and poultry.
The new labeling information emphasizes these important points:
- Any use of a dewormer can result in the development of antiparasitic resistance.
- Proper dosing is critical to the safe and effective use of a dewormer.
- End-users
should work with their veterinarian to monitor herds and flocks to
determine the extent of antiparasitic resistance on a particular farm.
- Dewormers should be used as only one part of an overall internal parasite control program.
The
FDA also reminds veterinarians, livestock producers, and animal owners
about antiparasitic resistance and the importance of developing an
overall parasite control program to slow resistance to dewormers.
Veterinarians, livestock producers, and animal owners may not be aware
of the threat of antiparasitic resistance or ways to slow it down. The
new labeling information will help them better understand the proper use
of dewormers and ways to monitor and slow down the development of
antiparasitic resistance at the farm level.
The new labeling
information does not replace the need to work with a veterinarian to
determine appropriate parasite management strategies for individual
animals or herds or flocks. Rather, the new language focuses on how to
properly incorporate dewormers into an overall parasite control program
and how to slow down the development of antiparasitic resistance.
Slowing the development of resistance extends the effectiveness of
dewormers and better protects animal health in the long term.
Because
grazing animals are continually exposed to worm eggs on the pasture,
they can have repeated parasite infections. Although most swine and
poultry in the U.S. are not raised on pasture, the number of these
animals being pasture-raised is growing. This increases their chances of
being repeatedly exposed to worms which may then become resistant to
dewormers. The FDA is aware that management practices and production
schemes for swine and poultry differ from those in grazing species, and
the new labeling information will reflect these differences.
The
FDA is requesting that drug companies add information about
antiparasitic resistance to both over-the-counter (OTC) and prescription
dewormers. Some approved dewormers for livestock and horses are
prescription only, but most are OTC. For a product to be approved as
OTC, the label must have adequate directions for use that are written in
such a way that a non-veterinarian can use the drug safely and
effectively. Including information about resistance on the label of OTC
dewormers is important for communicating adequate directions for use to
non-veterinarians. More detailed information about the proper use of OTC
dewormers and ways to monitor resistance will help livestock producers
and animal owners use these products safely and effectively.
The
FDA is requesting that drug companies include this information on the
labels of their currently marketed FDA-approved dewormers for livestock
and horses within the next 12 months, and on labels for any new dewormer
that FDA approves for use in these animals.
