Although adult worms are only up to two centimeters in length, or less than about one inch, they can collectively weaken sheep by attaching to the lining of each animal’s abomasum.
The parasites feed on blood and can rapidly cause anemia, or lack of sufficient red blood cells to carry oxygen. It not only can affect the profitability of farmers by impacting the ability of their sheep to gain weight or grow wool, but it can also quickly lead to the death of their animals if left untreated, said Gellatly.
“Although the L3 infective stage does not tolerate the harsh winter conditions of Western Canada, we now know that the L4 stage can survive inside the host in a dormant state through a process called hypobiosis. These larvae resume development in the spring, contributing to reinfection even when environmental contamination appears minimal.”
Another pressing issue is the declining effectiveness of commonly used dewormers in Canada, such as ivermectin and benzimidazoles, said Gellatly. “Studies led by Dr. Gilleard’s team have identified the barber’s pole worm as the most prevalent gastrointestinal roundworm in Western Canada, and confirmed the presence of anthelmintic resistance to these treatments.”
The 57-day study was funded by Alberta’s Results Driven Agriculture Research (RDAR) agency, along with Alberta Lamb Producers and Ontario Sheep Farmers.
It was launched in 2023 and involved testing of Rideau Arcott sheep divided into four groups of 15 animals each: infected and dewormed, infected and non-dewormed, non-infected and dewormed, and non-infected and non-dewormed, said Gellatly. “Testing these groups was essential for identifying metabolomic changes in sheep before and after deworming.”
Producers must currently detect infected sheep using a visual test called the FAMACHA chart. The level of anemia is determined by comparing the colour of the mucous membranes inside of the lower eyelids, or conjunctiva, of the eyes of sheep to the chart.
Another way producers identify infected animals is by checking for signs such as soiled tails due to diarrhea, as well as “bottle jaw” – a soft swelling under the jaw caused by fluid buildup due to parasite infection. Producers may also confirm infection by sending fecal samples to a lab for fecal egg counts.
The problem is these tests work best on sheep that are already far down the road to being infected, said Gellatly. It is forcing producers to treat all of their sheep with anti-parasite medications such as ivermectin as a precautionary measure, she said.
It not only significantly adds to the expenses of farmers, but it also is increasingly causing the infections to become harder to treat, she said. “The worms are developing resistance to these medications due to overuse.”
In summary, this study marks a major advancement in combating parasitic infections in sheep by offering a practical, science-based approach to a growing global issue.
Through the identification of metabolite-based biomarkers, it has the potential for an early, accurate, and on-farm detection of Haemonchus contortus, paving the way for more targeted parasite control, reduced reliance on mass anthelmintic treatments, and enhanced animal welfare.
With further development, the proposed handheld diagnostic device could become a vital tool for producers, supporting the long-term sustainability and profitability of the sheep industry.