Vet's Perspective: Coccidiosis in cattle
Coccidiosis in cattle
Coccidiosis is an infection caused by the protozoan of the genus Eimeria and can cause significant health and economic problems in any variety of cattle types. All domestic species are susceptible to coccidian infections, although each protozoan is host specific to a particular type of animal family. There are at least thirteen species of coccidia affecting cattle in North America, but the two most pathogenic are Eimeria bovis and Eimeria zuernii.
The life cycle of Eimeria organisms is similar to that of other parasites. Oocysts, or eggs from the organism, are initially ingested through contaminated feed by unsuspecting animals. Fourteen days later, the organisms have matured in the animal’s small intestine. They then begin their journey through the cecum and large intestine and are excreted in feces. A new set of oocysts are then available to contaminate food lying near fecal debris.
Coccidia most often affect the epithelial cells lining the mucosa within the gut lining of a developing animal. Infection is acquired from contaminated feed, water, soiled environments, and even licking filthy hair coats.
Signs of illness may appear vague at first, but most often include: anorexia, rapid weight loss, and bloody diarrhea. Severe cases may have very watery diarrhea with strands of sloughed intestinal mucosa. Animals quickly become emaciated, dehydrated and very weak.
Calves and cattle up to the age of two years are most likely to be infected by coccidiosis. The disease is also most prevalent in animals living within close proximity of each other and those in wet, fecal-contaminated environments. Feedlot cattle living in highstress environments are also likely to be affected. Stressful events such as weather, transportation, ration changes, overcrowding and weaning are triggers for compromise to an otherwise healthy immune system.
Coccidiosis may demonstrate itself as “clinical,” meaning animals outwardly show signs of disease; and as “subclinical,” in which animals are infected but symptoms have not become drastic enough to show up in the production aspect. It is estimated that nearly 95 percent of animals with coccidiosis are actually a part of the subclinical disease segment.
Animals with subclinical disease demonstrate economic loss due to the malabsorption of nutrients and decreased weight gain. When infected animals have concurrent diseases, such as Coronavirus or Rotavirus, they are typically more difficult to treat and often suffer considerably more damage to the intestinal lining.
Animals affected by the Eimeria organism suffer from reduced feed consumption and thus decreased body weight and rates of gain, as well as diarrhea and generalized ill thrift in hair coat and body condition. Mortality due to severe diarrhea and dehydration may result in at least approximately 25 percent of affected cases. A temporary immunity period of three to four months may occur after infection and recovery, but animals are still susceptible when not presented with a continuous challenge.
Producers often have a hard time detecting if coccidiosis is present in a herd until the time is too late because the parasite’s life cycle is nearly complete by the time clinical signs are demonstrated. Oocysts are passed in feces by the time that signs of illness may already be present. Regular fecal analysis of individual or pooled samples is beneficial in detecting low and high number of oocysts in a herd. Diagnosis is made by finding oocysts in fecal flotations or using the McMaster’s technique. Veterinarians will also consider similar pathogens such as Salmonella, Bovine Viral Diarrhea, E. coli or other intestinal parasites.
If animals are treated early enough, a smooth recovery is much more likely.
Severity of disease depends upon the number of sporulated oocysts affecting an animal, as well as the host animal’s own general health. Good sanitation measures and proper animal husbandry are critical components of keeping illness at bay. Water and feed troughs should be kept clean and away from potential fecal contamination as much as possible. Maternity pens and housing for newborn calves are especially important to keep clean and dry at all times.
Treatment can be difficult as most anticoccidial drugs are effective only during early stages of the coccidia life cycle. Anticoccidial drugs should be administered at the earliest signs of disease in order to reduce illness severity and decrease potential for mortality. Antibiotics are prescribed for secondary bacterial infections of the intestinal tract, and fluids with electrolyte solutions are used to control dehydration.
Coccidiostats are essentially low doses of sulfonamides, Amprolium or other drugs that aid in preventing coccidian infections. These products may be used in daily or monthly treatments within food or water throughout the herd. Ionophores also have anticoccidial effects, as well as growth promoting properties.
For more information on coccidiosis prevention, contact your regular veterinarian for sanitation and treatment plans. By working together with a medical professional, producers can maximize economic gains. — Dr. Genevieve Grammer
[Dr. Genevieve Grammer is a mixed-species veterinarian practicing in eastern Colorado. Please direct correspondence to drgigi19@ gmail.com]