Agriculture Canada’s research centre in Lethbridge, Alta., is
developing a new test for detecting warbles in livestock.
The newly developed blood test traces a protein excreted by warbles as
they migrate through an animal.
Research is still at the laboratory stage, but it is hoped the blood
test can be made commercially available within the next few years, said
Doug Colwell, a parasitologist with Agriculture Canada.
Work is ongoing with an American company to develop a reasonably
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priced, easy-to-do test at chute side.
Testing livestock for warble grubs isn’t common because most producers
and feedlots use a broad spectrum internal parasite treatment. Organic
beef operations may find it a valuable tool, however, because it
reduces the amount of treatment required and prevents resistance.
It is known that range cattle can become seriously infected, causing a
drop in performance and suppressed immune systems in calves.
“They reduce the ability of the calf to respond to other diseases,”
Colwell said. “That has not been translated into a dollar value.”
Cattle infested with warble grubs can lose nearly a pound of weight per
day. Those with serious infestations exhibit a condition known as
gadding, where the animals run in a panicked state about the field
because the insects are so irritating.
Adult female flies do not sting. Instead they lay between 400 to 800
eggs on the legs and undersides of cattle starting in the middle of May.
“They don’t have any mouth parts,” Colwell said.
“They don’t sting and they don’t bite. They’re just flying egg
machines.”
Eggs hatch within two to seven days and crawl to the base of the hair
and burrow through the skin into the animal’s body. They head toward
the esophagus and spinal cord and eventually through connective
tissues. They excrete enzymes as they move through the body that break
down tissue, making it more digestible for the maggots.
Cattle grubs arrived in North America with the first European farmers
and their livestock.
The Lethbridge team has been working with Spanish veterinarians because
Western Europe, North Africa and China have widespread warble problems.
Alberta has maintained a warble control program since the 1970s under
the Agricultural Pest Act. Internal and external treatments are used in
fall and spring to stop the grubs before they cause serious damage.
