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Coccidiosis in Beef Calves

B. Joe Dedrickson, DVM, Ph.D.
Alpharma Animal Health Division
Fort Lee, NJ 07024

Coccidiosis is one of the most economically important parasitic diseases of beef cattle, costing the cattle industry in the United States several hundred million dollars annually. Bovine coccidiosis is considered to be one of the top five most important diseases in the U.S. cattle industry.

Coccidiosis is a ‘Stress Induced’ parasitic disease associated with bloody diarrhea, poor growth and body condition and sometimes death. Clinical signs of coccidiosis occur most frequently in young animals, but may also occur in adult animals. Compared to clinical coccidiosis, inapparent or ‘Subclinical’ coccidiosis is more important and may account for over 95% of all the losses associated with coccidiosis.

All cattle in the United States are infected to some degree by coccidia. Coccidiosis is caused by an intracellular protozoan parasite that grows in the cells that line the intestines. Once calves reach 6 months of age, they have a 100 percent infection rate even though 5% or less show clinical signs. While 95% of all losses due to coccidiosis are subclinical.

Life Cycle of the Parasite

Coccidia oocyst (eggs) are ingested by susceptible animals when they consume contaminated feed or water, graze contaminated pasture or lick a dirty hair coat. The oocysts release sporozoites (larvae) that multiply asexually in the cells lining the wall of the small intestine and releasing thousands of merozoites (2^nd generation larvae). The merozoites then enter the large intestine and go through a sexual reproductive cycle to produce thousands of oocyst. These oocyst pass out with the manure to further contaminate soil, feed, water, bedding, etc. and begin the cycle again.

Each oocyst contains eight sporozoites. Each sporozoite enters multiple cells in the lining of the small intestine and destroys the cell as it forms a schizont (packet) of merozoites. When it ruptures, it releases more than 100,000 new merozoites and it has been estimated that ingestion of only 125 sporulated oocysts will subsequently cause damage to more than 6 billion intestinal cells. This interferes with digestion and absorption of nutrients. About 71% of the life cycle occurs in the small intestine. Rarely do you see any clinical signs during this time in the small intestine. When they go to the large intestine around day 16 and the oocyst breaks out of the cell following the sexual reproduction around day 18, it causes diarrhea and blood in the feces from the damaged gut lining. Oocysts can be detected in the manure around 21 days.

Oocysts passed in manure need moisture and mild temperatures to sporulate. High temperatures and dryness impede sporulation. They can survive freezing (down to about 18 degrees F) for a couple of months, but temperatures below minus 22 degrees F will usually kill them. In both cases the manure or straw pack may give them the protection to survive even the harshest environmental conditions.

The Disease

Coccidiosis can cause diarrhea and weight loss, as well as, immuno-suppression. This immuno-suppression can make calves more susceptible to other diseases. For instance, research at Ohio State University has shown that whenever coccidiosis and corona virus are both present, the diseases are much more severe than if alone. It is also common to see an increase in respiratory infections when coccidiosis is a problem. Coccidiosis costs cattle feeders more than $400 million annually in lost profits due to reduced feed efficiency, slower weight gain, and increased susceptibility to other diseases. This can set back calves’ growth by as much as two months. A 1990 feedlot study ranked coccidiosis as the third most important feedlot problem with respiratory/pneumonia problems being number one.

Symptoms

The rupture of cell lining the intestine during the coccidia’s multiplication results in diarrhea, especially bloody diarrhea. A mild fever may occur in early stages, but in most cases the temperature is normal or subnormal. The first sign of illness is usually the sudden onset of severe diarrhea, with watery feces containing blood or mucus. The blood may be dark and tarry, or appear as streaks or clots, or the feces may consist almost entirely of large fresh clots.

Calves’ rear ends, hind legs and tail bases are usually covered with loose feces. Watery manure containing blood or mucus can often be found on the ground. The loose, bloody manure contains millions of oocysts, which remain on the ground to infect other calves. In later stages of the disease, after the coccidia have quit multiplying, the feces firms up again.

A common sign of coccidiosis is calves straining excessively to pass a bowel movement. This is due to irritation of the large intestine and rectum. Calves may strain even after passing the watery feces or without passing anything. In severe cases, the rectum may prolapse from all the straining. If calves lose a large amount of blood, they’ll become anemic. Mucus membranes will be pale (gums will look white or blue instead of pink). And calves may be weak and uncoordinated. Most affected calves have a poor appetite. The disease runs its course in five to six days, but some animals take a long time to fully recover.

Disease Summary

Coccidiosis is a stress induced parasitic disease in which 5% or less of a cattlemen’s loss is due to clinical signs. The most common stressors are the things we must do to raise calves efficiently. Such as weaning, processing, putting in large groups, changing rations, shipping, with the most common stress being ‘Weather changes’. To manage coccidiosis we must focus on these common stress periods.

Management for Calves

Young calves are the most susceptible to coccidiosis. From birth to 6 months, the immune system is immature and coccidia do not stimulate good protection. They are especially vulnerable to coccidiosis if they are exposed to cow manure buildup during wet, warm weather in late winter or early spring.

Ranches with no winter grazing, where hay is fed from November through March, may provide ideal conditions for coccidiosis in calves if the cattle are grouped in feeding areas. Many cattle raisers use round bales and the cattle congregate around them.

To help prevent coccidiosis it is important to keep the cattle spread out on clean pasture, or keep changing the feeding area. By doing so the oocysts passed in manure are widely scattered over a larger area and calves don’t pick up enough to cause massive infection, but unfortunately, this alone will not prevent coccidiosis.

The picture changes when ranchers begin feeding hay. Ranchers may have their cows and calves in a 500-acre pasture but use only a few acres as a feeding area. During a wet spring, ranchers have to reuse the same spots for putting out their round bales, square bales or range cubes. Thus feeding on highly contaminated ground. It gets to be like a feedlot area.

Cows are continually passing a few oocysts, which may stay dormant in the manure for a while if the weather is cold. Then it warms up, and oocysts in the built-up manure become infective. Calves, who lie on the manure and then lick themselves, or suck a dirty udder, are exposed to high levels of oocyst.

It is important to move the cowherd to new ground in the spring. Get the cattle away from the areas of concentrated manure. Sunlight and heat (dryness) tend to damage the oocysts and the contamination is reduced during the hot summer. During the wet times of year, keep cattle on clean ground.

October and November can be risky times also. Many pastures are pretty well gone by then, and ranches are starting to feed hay. It’s usually not cold yet and the oocysts again have suitable conditions to cause infection whenever manure accumulates.

A fall calving herd won’t have a long period of contamination because the dry summer has kept the manure from being so infective, and the wet season may be short before weather turns cold. But calves born in the fall may still develop coccidiosis when conditions are right. Calves are most susceptible. They are starting to eat hay (contaminated feed) and they have very little natural immunity.

Management for Older Calves and Weanlings

Coccidiosis can sometimes be a problem in weaning pens or in stockers on winter grazing, especially if pens are crowded, pasture overstocked or hay is being fed. Changing weather and stress of bad weather may hinder calves’ immune system. If ranches can hold those calves 45 to 60 days on an anticoccidial medication and carry them through the stress period of vaccinating, worming, implanting, second dose of vaccine, etc. they won’t see any clinical coccidiosis. Coccidiosis is very stress related, and ranches are most apt to see an outbreak when those calves are weaned and processed or experience changeable weather.

The first 30 days after weaning are very stressful, as evidenced by lower feed consumption. Dr. David D. Hutcheson, a professor at Texas A & M University’s Agricultural Extension Center at Amarillo, conducted feed consumption studies which showed that calves coming into feedlots only consume 0.5 percent to 1.5 percent of their body weight (dry matter intake) the first week, 1.5 percent to 2.5 percent the second week, and 2.5 percent to 3.5 percent in the next two weeks, taking almost four weeks to come up to full feed. This is the time they need maximum protection from coccidiosis with some type of medication treatment in the feed or water.

Treatment and Prevention

Coccidiosis as a disease may run its course and subside, without treatment. Symptoms usually disappear after the multiplication stage of the parasite has passed, by this time you’ve already taken a significant performance loss. Several medications are effective against coccidiosis if given early in the course of the disease, before symptoms appear.

However, by the time diagnosis can be made, the critical stage is past because the protozoa has gone through its life cycle and treatment is not effective. It is too late to halt the infection, but it is necessary to prevent later outbreaks. Supportive treatment may still be necessary to save calves, to prevent dehydration and to ward off possible secondary diseases that may result from weakened condition.

There is also misunderstanding about how to treat the disease. The clinical signs subside when the multiplication stage of the protozoa is past. Many treatments have been credited with causing "recovery" and are recommended without taking this factor into account. Medications commonly used for treatment have very little effect on the late stages of the coccidia. The only effective treatment for the already sick animal is supportive therapy (fluids) and antibiotics to ward off secondary infections.

The most effective coccidiosis program is preventive treatment before clinical signs appear, but unfortunately may producers don’t understand the labels on the four products that are available. They are; amprolium (Amprol or Corid), lasalocid (Bovatec), monensin (Rumensin) and decoquinate (Deccox). Many producers assume that ‘Prevention’ and ‘Control’ mean the same thing, but that is not the case. If a product has a control label, it will only reduce the severity of a coccidiosis out break. If a product has a prevention label, it will stop clinical signs from occurring. As you review the table below you will see that Amprolium and Decoquinate have a prevention label, lasalocid has only a control label and monensin has both a prevention and control label. What this means is lasalocid will not stop calves from breaking with clinical signs at the highest legal level of 1mg/kg of body weight or 45 mg per 100 lbs. You would have to feed a 500-lb. calf 225-mg per day, just to reduce the severity of an outbreak. If you used monensin on a 500-lb. calf, you would need a minimum of 270 mg per head per day to prevent any clinical signs from appearing. If you use less than that you will only control the severity of the coccidiosis outbreak, as with lasalocid. While amprolium and decoquinate will prevent coccidiosis outbreaks at their label dosage. If you understand the label you can very effectively prevent coccidiosis with the four products available. This is summarized in the chart below.

Anticoccidial Products

These products have varying levels of anticoccidial activity at their label doses. A good coccidiostat can break the life cycle of parasites so they can’t reproduce and spread infection, stopping them before they multiply and create massive gut damage.

Summary

Coccidiosis is a ‘Stress Induced’ parasitic disease that causes hundreds of millions of dollars in losses annually in the United States. 95% of all losses are due to subclinical disease, while only 5% of all loses are due to the clinical disease - ‘Bloody Diarrhea’. You can never eliminate coccidia from cattle; you can only manage its effect on your herd. There are four good anticoccidial products available on the market for cattle. None of them have any residual activity; therefore they are only working when you have them in the feed. Good coccidiosis management is ‘Continuous Prevention’ with good management procedures and a good anticoccidial-feeding program during periods of stress.

NEONATAL CALF DIARRHEA