By Blake Jackson
In October 2024, a New York dairy farm with 750 cows faced a flea infestation in its young calves. Seventy calves, all fed a milk diet, were housed in individual hutches on gravel with chopped hay bedding.
The affected calves, as young as 2 weeks old, displayed signs of pruritis and alopecia. Fleas collected from a 3-month-old Jersey calf were confirmed as Ctenocephalides felis (cat fleas) by the Animal Health Diagnostic Center (AHDC).
To treat the infestation, affected calves were given Ultraboss (5% permethrin and 5% piperonyl butoxide), an insecticide used to kill lice and flies in cattle, though no flea-specific treatments are approved for cattle in the U.S. Permethrin is known to kill fleas, but its effectiveness is debated. Blood counts and chemistry panels from nine affected calves came back normal.
A follow-up visit by AHDC veterinarians one week later revealed that the flea issue persisted. Approximately 40 fleas were collected from the Jersey calf, which had received two treatments with Ultraboss (the most recent just 8 days earlier).
Another 30 fleas were found on a neighboring Holstein heifer and a few more on younger calves. The persistence of the infestation despite treatment suggests minimal residual effectiveness of permethrin and ongoing reinfestation from the farm’s premises.
The farm has around 30 barn cats, some of which spend time near the calf hutches, potentially contributing to the flea problem. However, no feral cats were sampled during the farm visit.
The farm planned to continue weekly Ultraboss treatments for five weeks, though they did not plan to treat the cats or the environment for fleas.
It is important to note that permethrin is toxic to cats, and a pyrethroid product with an Insect Growth Regulator (methoprene) should be used for premises treatment.
Flea infestations in dairy cattle are rare in the U.S., but their occurrence is serious, as seen in a 1993 Kansas case, which resulted in calf deaths and severe anemia.
Photo Credit: istock-simplycreativephotography
Categories: New York, Livestock, Dairy Cattle