When the bugs fight the drugs

Each summer DVM students from the Ontario Veterinary College at the University of Guelph delve into hands-on, practical experience at veterinary clinics across Ontario and additional locales during their Externship Veterinary Course. Funded by the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), students must complete an eight-week Externship Course between third and fourth year in a rural veterinary practice that works with food animals and/or equine, as well as companion animals.These Externship blog posts are an opportunity to tag along with students this summer. Here student veterinarian Stephanie looks at anthelmintic resistance in sheep. Check out all the student blogs here.

Veterinary medicine is a constantly evolving field, with new pharmaceutical products being released every year. Drugs can play an important role in preserving the health of individuals and populations as a whole. However, they need to be used in a responsible and appropriate manner. In recent years the issue of drug resistance has become a hot topic. We will explore this complex problem by looking at anthelmintic resistance in sheep.

Sheep kept on pasture can become infected with various types of roundworms that live in the gastrointestinal tract. These parasites can cause a decrease in production and be detrimental to the sheep’s health. One parasite in particular, haemonchus contortus, also known as the ‘barber pole worm’, is highly pathogenic to sheep. It attaches to the inner lining of the stomach and feeds on blood, leading to anemia, edema (bottle jaw) and even death. Therefore, most farmers choose to deworm their flock with anthelmintics. This should lead to healthier sheep and higher production numbers, right? Not always.

The issue is that these gastrointestinal nematodes can evolve over time and no longer be affected by the dewormer, leading to overwhelming worm burdens in sheep. In a recent study on 47 Ontario farms, it was found that most farms had resistance to Ivermectin and fenbendazole, 2 commonly used anthelmintics in sheep. To make matters even more interesting, haemonchus contortus, the barber pole worm, was the main parasite responsible for the resistance. The question becomes: do we treat with a new class of drug that has a different mechanism of action, or do we change our current treatment protocols? The answer: we do both and more!

The Ontario Veterinary College and the Ontario Ministry of Food and Agriculture have come up with the 5 star worm plan that focuses on selective treatments as well as minimizing drug use and pasture contamination.

The goal of programs like this one is to promote proper drug use, maximize animal health and mitigate long term problems like drug resistance, ultimately being of benefit to the industry as a whole. It is evident that long-term, sustainable control of parasites in sheep requires integration of multiple control methods.

Through this brief overview of resistance to anthelmintics in sheep, it is important to be aware that drug resistance is a real issue affecting individual animals, to whole industries, and everything in between. The development of guidelines for prudent drug use in both the human and animal world are key to managing resistance. It is our duty as students, veterinarians, readers, members of the general public to stay educated on the matter of drug resistance. After all, it is the choices we make today that will shape our world of tomorrow.

Dr. Henry Ceelen and I are using the FAMACHA score on a ewe; the system estimates the degree of anemia in sheep through use of a color guided chart that is compared to the mucous membranes around the eye. FAMACHA can be used as an aid to determine which ewes require treatment, acting as part of “star 3” in the 5 star approach. Open communication and education of the producer is imperial to ensure that all 5 stars of the worm plan are covered. We are glad to have helped this farmer on the ongoing, ever-changing road towards a healthy flock.

Follow OVC on Twitter, Facebook, and Instagram @OntVetCollege

Comments are closed for this blog post

Welcome to
Ontario Agriculture

Sign Up
or Sign In

Agriculture Headlines from Farms.com Canada East News - click on title for full story

CFIA Proposes Changes to Expand Interprovincial Meat Movement

Canada is proposing temporary regulatory changes to support interprovincial meat trade, improve food security, reduce costs for producers, and strengthen rural and remote communities.

American Lentil, Pea Acres Slide from March, Last Year

U.S. farmers planted fewer lentils and dry peas than they indicated in March, with both crops also posting declines from last year, according to the USDA’s June Acreage report released Tuesday. American lentil area was estimated at 747,000 acres, down 85,000 acres from March intentions of 832,000 acres and down 30% from 1.072 million in 2025. Area expected to be harvested was forecast at 701,000 acres, down from 949,000 last year. Montana, the largest lentil-producing state, accounted for most of the decline. Farmers planted 560,000 acres, below the March projection of 620,000 acres and down 270,000 acres from 2025. North Dakota acreage fell to 130,000 acres, compared with the March estimate of 155,000 acres and 185,000 acres last year. Washington acreage was unchanged at 57,000 acres. Dry pea plantings were estimated at 1.047 million acres, down from the March projection of 1.17 million and down 11% from last year. Harvested area was forecast at 1.001 million acres, compared wit

ICE Close: Canola Higher on Return from Canada Day Holiday

Canola futures finished slightly higher on Thursday as the market returned from the Canada Day holiday a day earlier. Modest gains in crude oil provided some support for vegetable oils and helped lift canola, while mixed movement in Chicago soybeans and soyoil kept the advance restrained. Crude oil settled marginally higher Thursday on short covering ahead of the U.S. holiday weekend. Trading was relatively cautious, however, as market participants adjusted positions ahead of another holiday interruption. U.S. markets will be closed Friday for the Independence Day holiday, reducing direction from Chicago until trading resumes next week. Prairie weather also remained a background influence, with excessive moisture in some areas supporting crop concerns, although generally favourable conditions elsewhere and Canada’s larger projected canola acreage limited the upside. November was up 41.20 at $736.50, and January added $1.50 to $745.40.

Manitoba Crops Holding Up Amid Wet Conditions

Manitoba crops remain in generally good condition, even as isolated thunderstorms brought hail, strong winds, intense rain to portions of the province this past week. According to Tuesday’s weekly crop report, weekly rainfall totals ranged from just 2 mm to more than 123 mm, with the heaviest amounts reported near San Clara, Roblin, Waskada, Minnedosa, Manitou and the southern Interlake. Parts of the Northwest have now received more than 150% of normal precipitation since May 1, while the Stonewall area is approaching 250% of normal. Even so, winter wheat and fall rye are flowering and showing strong yield potential, the report said, while spring cereals range from tillering to the flag-leaf stage. Canola development varies widely from the two-leaf stage to early flowering, and soybeans are mostly between the first and fourth trifoliate stages. Excess moisture remains the main concern, particularly in the Northwest, Interlake and low-lying parts of the Southwest. Standing water,

Fireworks, Flavor, and a 250th Birthday: How to Keep Cookout Favorites Food Safe All Holiday Weekend

In preparation for America’s 250th Anniversary on the Fourth of July, the U.S. Department of Agriculture’s (USDA) Food Safety and Inspection Service (FSIS) provides tips for practicing safe food handling when grilling and hosting outdoor gatherings. “The summer heat increases food safety risks, but simple steps can prevent foodborne illness from outdoor gatherings,” advises Under Secretary for Food Safety Dr. Mindy Brashears. “Keeping perishables in coolers or insulated containers, following a two-hour rule (or one hour when temperatures are above 90 F), and grilling meats to safe internal temperatures are easy ways to protect friends and family from harmful bacteria as we all celebrate America’s 250th birthday.” Here are some recommendations for safe outdoor food preparation and serving: Marinating Always marinate meat in the refrigerator, never on the counter or at room temperature. Marinade used on raw meat or poultry must be boiled for a few minutes to destroy any harmful bacte

More…

Badges | Report an Issue | Terms of Service