In September in the Southeastern U.S., a two-year-old Angus heifer died the previous night. She had a three-week history of poor appetite, unthriftiness, and diarrhea.

Several other younger cows in this herd also look unthrifty and have diarrhea. The cattle are vaccinated yearly and dewormed twice a year with pour-on moxidectin.

Necropsy reveals that the abomasum is edematous and covered in small umbilicated nodules, 1-2 mm in diameter (cobblestone appearance).

What is the most correct action to take next?