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Coccidiosis still a threat to be monitored

Animal Health with Roy Lewis: Important to control internal and external parasites

While calves can be given a preventative treatment against coccidiosis, cows can be given a coccidiostat such as rumensin or monensin in the feed before calving to reduce shedding of the infective eggs onto the ground.

Coccidiosis and internal parasitism are two clinical syndromes I thought we had rid from the cattle sector. But although they just about disappeared, they are on the comeback trail. It is important to know why along with new strategies to keep them at bay.

Clinical signs, diagnosis and treatment must be periodically reviewed. Direct communication among yourself as rancher/farmer, a nutritionist and a veterinarian are sometimes necessary to realize the maximum benefits your cattle get from preventing either or both of these disease syndromes from slowly creeping into your herd.

A certain generation will remember the signs of a coccidiosis outbreak. One form of the disease involved bloody diarrhea associated with severe irritation and straining, often seen in young (usually one-month-old plus) calves or weaned calves in the backgrounding lot.

Weather changes or other stressors such as processing could produce another form known as ‘nervous coccidiosis.’ Along with bloody diarrhea, other nervous system signs included staggering, convulsing with the head thrown back to animals going down.

These symptoms might be barely distinguishable from other health issues such as polioencephalomalacia, ITEME, lead poisoning some mycotoxins or even vitamin A deficiency.

The coccidiosis outbreaks were usually sporadic but often involved several calves. Anything which inhibits the immune system such as dexamethasone used for aborting heifers to a high worm (parasite) count can suppress the immune system resulting in an increase in coccidiosis, including the nervous form. Canada and the United States are two of the few countries where this type of coccidiosis is reported.

Management and treatment options can help to prevent the disease. Controlling coccidiosis involves controlling manure disposal on cropped land as well as preventing runoff from pooling up on calving fields. The parasites are often shed and thrive in feces.

While calves can be given a preventative treatment against coccidiosis, cows can be given a coccidiostat such as rumensin or monensin in the feed before calving to reduce shedding of the infective oocysts (eggs) onto the ground.

Other treatment products such as deccox may be given in creep feed for young calves or put in total mixed rations in a feedlot or backgrounding operation. There is a treatment product called toltrazuril (baycox) that is also specifically a coccidiosis treatment product. Prevention or treatment will help to increase weight gains and reduce the risk of clinical cases, which often become poor doers. Straining from coccidiosis may even cause prolapsed rectums which must be dealt with and repaired.

Worms on the increase

Some studies have shown that certain preventive treatments are becoming less effective against internal parasites. The macrocyclic family (ivermectin type) of dewormers is becoming less effective against internal worms and most recently (within the last two years) is also becoming less effective against external lice (sucking and biting).

We have seen increasing numbers of internal worms in cattle herds even though prior good management and treatment procedures were being followed.

An increase in internal worms causes the immune system to kick into overdrive as it works overtime to try and get the parasites to stop laying eggs. This takes a lot of energy and can weaken a different part of the immune system, allowing coccidia to flourish.

Since Health Canada’s Veterinary Drug Directorate considers coccidiostats a category four antimicrobial, my worry was they might be pulled from antibiotic-free programs or the European HF or other hormone-free programs. Most of these programs allow these coccidiostats and should be included in any feeding program, in my opinion. They have been proven to be an economical, effective way of keeping coccidiosis in check along with all the health and growth and feed efficiency benefits associated with them.

Fortunately, if in doubt, both disease syndromes can be diagnosed with fecal flotations where both oocysts and worm eggs can be identified in the same fecal sample. Likewise, after treatment, a single sample can be checked again to hopefully show a substantial decrease in parasite numbers. If testing is done too early, the fecals may not reveal any oocysts because the cycle has not been completed yet. Veterinarians may need to start treatment based on clinical signs and go with their gut instincts rather than lab results.

In deworming trials, Merck Animal Health did over the last several years show that deworming with a different anthelmintic such as Safeguard did dramatically reduce the coccidia load. As the worm pressure is reduced, it allows the cattle’s immune system to substantially reduce the coccidia. The coccidiostats can still be used and have proven to be very effective and economic over the years.

About the author


Roy Lewis is an Alberta-based veterinarian specializing in large-animal practice. He is also a part-time technical services vet for Merck Animal Health.



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