Ask the Vet
Why Is This Older Cow Losing Weight?
READER: I have an older cow that has had severe diarrhea for several months. I have wormed her with Ivomec injectable, Cydectin Pour-On and Safe-Guard paste, and she still has diarrhea. She eats great but keeps losing weight. We don't have a vet close by, so I sent a sample to a lab to check for worms, and they didn't see anything. What could this be, and how can I treat it?
DR. McMILLAN: I think you need to find a way to get a veterinarian to examine her. Many diseases could be involved, but when an older cow has these signs, my first thought is Johne's disease (pronounced YO-neez).
Johne's disease is a chronic, progressive and incurable disease caused by Mycobacterium avium subspecies paratuberculosis (MAP), a bacterium related to those that cause tuberculosis and leprosy. In most cases, it progresses slowly. It is more common in dairy cattle than in beef cattle, but its incidence in beef cattle may be underreported, because many infected cows are probably culled for poor performance. That said, I have also diagnosed it in a 2-year-old Brangus bull.
The organism is shed in manure, colostrum and milk, and can survive for more than a year in some environments, especially moist areas contaminated with manure. MAP is spread primarily by fecal-oral transmission. Feces from infected animals contaminate pastures, water and teats. Young animals are much more susceptible to infection than older animals. Calves can also be infected in utero or through infected colostrum or milk. Nursing dirty, contaminated teats is an extremely common route of infection.
There is no treatment for Johne's disease. Management and sanitation are the keys to preventing infection. Eliminating muddy, manure-contaminated areas is essential to preventing this disease and many other problems. Calving on clean pasture will go a long way toward preventing Johne's and other diseases, such as calf scours.
Your veterinarian should test any animal with chronic, nonresponsive diarrhea. Testing is an important tool for identifying and removing infected animals, but false negatives can occur, especially early in the disease process. Knowing that you have Johne's on your farm is an important step toward controlling it.
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It may not be Johne's, but that is the first place I would start in your case.
READER: I recently saw Dectomax-CA1 in an animal health catalog. Is this different from or better than the original Dectomax?
DR. McMILLAN: Dectomax-CA1 injectable contains the same active ingredient and dose as the original Dectomax: 1% doramectin. CA is short for conditional approval. This is a pathway the Food and Drug Administration (FDA) uses to allow certain animal drugs to be marketed after demonstrating safety, manufacturing quality and a reasonable expectation of effectiveness while the company collects the data needed for full approval.
In the case of Dectomax-CA1, the CA1 label designates its use for the prevention and treatment of New World screwworm larval infestations in cattle and prevention of reinfestation for 21 days. Dectomax-CA1 and Dectomax contain the same active ingredient at the same dose, and all other label information is unchanged.
Exzolt Cattle-CA1, or fluralaner, is a conditionally approved product labeled for prevention and treatment of New World screwworm larval infestations and treatment and control of cattle fever ticks. Exzolt Cattle-CA1 is a prescription topical pour-on solution manufactured by Merck Animal Health and contains the same active ingredient used in the company's Bravecto line of small-animal products.
This is the first time a drug in this class, isoxazolines, has been conditionally approved for use in food animals, and it's the first new class of ectoparasiticides approved in many years. I am certain it will prove to be an extremely valuable tool in combating these two severe threats to our cattle industry and, in time, for the control of other external parasites. But, producers must be very respectful of its legal and proper use, or the FDA could rescind this conditional approval.
The FDA emphasized that this approval addresses an unmet need for treating cattle fever ticks, specifically, and must be used strictly according to the label.
According to Merck Animal Health, Exzolt Cattle-CA1 is indicated for the prevention and treatment of infestations caused by New World screwworm (Cochliomyia hominivorax) larvae, or myiasis, and treatment and control of cattle fever tick (Rhipicephalus microplus) in beef cattle 2 months of age and older, as well as replacement dairy heifers less than 20 months of age. It is not for use in lactating dairy cattle, dairy calves, veal calves or bulls at least 1 year old that are intended for breeding.
All producers, especially those along the Southern border, need to be on the lookout for New World screwworm and cattle fever ticks. If you suspect a problem, report it to your local veterinarian or to state or federal veterinary authorities.
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-- Please contact your veterinarian with questions pertaining to the health of your herd. Every operation is unique, and the information in this column does not pertain to all situations. This is not intended as medical advice but is purely for informational purposes.
-- These are only my thoughts and general guidelines. Please get with your veterinarian and together develop the best program for your herd.
-- Email Dr. Ken McMillan at vet@dtn.com
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