Coccidiosis - The Silent Thief
Source: Dairy Herd Management
 Although it infects virtually all cattle and can strike anywhere, coccidiosis is usually a disease of concentration, where the environment infects and reinfects. |
Consider the scope of what you're up against: If one single coccidia - the microscopic organism that causes a form of contagious scours - were the size a BB, one 28 day reproductive cycle would produce enough offspring to fill a pickup bed. If all those reproduced, one-month later they would cover a quarter section of land almost 250 feet deep.
That wild excess of Mother Nature means the organisms that cause coccidosis live almost everywhere on your dairy. They're almost impossible to eliminate, and they infect just about every bovine.
Once a vulnerable calf swallows that organism it faces a huge potential for damage: Ingesting only 50,000 of the estimated 50 million eggs a cow passes each summer in her manure can cause severe intestinal disease.
So, the seriousness of the disease is directly related to the number of coccidia the animal ingests: Light infection causes no clinical signs and results in gradual immunity build. Heavy infection can kill up to one in four young calves.
As a result, coccidiosis costs the U.S. cattle industry several hundred million dollars per year. In a 1990 study, veterinarians ranked coccidiosis the third most prevalent health problem of cattle, second only to pneumonia and IBR.
However, the real losses come not from scouring calves, but from the 95 to 98 percent of infections you never see. These silent, subclinical infections damage the absorptive surface of the intestine and weaken the immune system, leading to:
- Poorer feed efficiency
- Slow weight gain
- Weight loss
- Longer heifer development periods
- Increased susceptibility to other scours-causing bacteria
Those
costs can add up quickly: If coccidiosis slows the growth of a heifer
by two weeks at a typical development cost of $3 per day, it can add over
$40 to its cost, not including treatment and death loss.
Treatment of bovine coccidiosis is difficult and often disappointing, because once you see the clinical signs, the disease is so far along that the damage is done - severely affected calves may never regain productivity losses can be successfully prevented.
Although a number of treatments have been available for years to fight coccidiosis, simply trying to medicate your way out of the disease is bound to be disappointing. If you see a calf scouring from coccidiosis - particularly if it's reached the bloody stage - that usually means the coccidia have done enough damage to the calf's intestinal tract that even if it recovers, it my never make up the lost performance.
Coccidiosis is entirely preventable, but on-again, off-again medication without complete management only postpones the disease cycle. Controlling the disease from the moment the calf arrives with an approach that combines management with medication promises the most success.
As with all cases of scours, diagnosis by clinical signs alone is difficult. However, watches for these telltale signs that may signal a coccidiosis out-break:
- Feces matted around the tailhead. Manure from a coccidiosis-affected Animal will contain relatively higher amounts of mucus, so it tends to stick around the tailhead.
- Dull, rough hair coat. Infected animals appear sluggish and unthrifty. The coat of Holstein calves takes on a brown cast.
- Pot-bellied calves
- Blood in the feces. The blood can be dark and tarry or show up as Streaks and clots.· Watery diarrhea, coupled with continual, unproductive straining to pass Manure.
- Weight loss, dehydration and pneumonia.
The most reliable sign is age at onset. Because the coccidiosis lifecycle takes about three weeks, it almost never causes scours in very young calves. If calves are scouring before 18 days old, suspect something else, like cryptospordium.
Your veterinarian can make a microscopic examination of pooled fecal samples for presence of coccidia, or check the gut lining for damage.
Cows older than two years build up enough immunity that they almost never scour. However, they continue to shed the oocyts, which can last up to a year in the soil, inside buildings, on porous (wooden) surfaces, in the manure pack and in the haircoats of animals. If calves are raised in group pens with bedding or solid floors, assume you have coccidiosis. Calves raised in hutches are also at risk if they can have nose-to-nose contact, if the hutches aren't fully sanitized and dried between calves, or if hutches have wood surfaces.
Coccidia are tenacious. The shaded, damp and insulated environment dairy heifers are raised in is ideal for culturing coccidia - you can't depend on a hard freeze to kill them.
Yet under the right conditions, they are relatively easy to kill. Hot, dry conditions kill them quickly. Prolonged freezing can kill them, as well, although they are capable of overwintering.
Exposing coccidia to those conditions and breaking their spread helps control the disease. Sanitation must begin immediately at birth. Keep the dry cow environment clean. Clean heifer pens. Try to avoid wooden surfaces in pen construction. Clean calf hutches with a power sprayer between calves. Locate hutches far enough apart to prevent contact. Try to schedule the workday so you're moving from healthy to sick animals, old animals to young.
Raise feed and water troughs off the ground. Don't feed hay off the ground. Avoid poorly drained pastures. Drain dry-lots.
The 21-28 day lifecycle of the coccidia protozoan begins when the mature egg-carrying organism, the oocyst, is eaten by a cow from grass or from licking infected surface, another animal or its own hide. The oocyst ruptures inside the rumen, releasing sporozites. The cycle continues through several development states inside the intestinal wall where the organism infects the cells, reproduces and destroys the cells in the process, concluding when mature oocyts are excreted by the cow in feces. Outside,the oocysts sporulate in moist, oxygenated environments between 53 and 90 degrees F. and begin the cycle over again. Evolution has compensated the organism for its inability to move by giving it the ability to reproduce in droves. Each single sporulated oocyst can produce up to 20 million more new oocysts. Yet in only takes an estimated 50,000 swallowed oocysts to cause disease. The only way to affect the cycle is to destroy the oocyst outside the animal or prevent it from leaving the animal.
Coccidiosis shows a common pattern of outbreak. Constant, low-level exposure builds immunity in old cows. New calves with a little or no immunity enter that environment, get infected, get stressed, and break with scours.
The most common stressor that causes an outbreak is moving heifers from individual to group housing. However, it's not the only one: Weaning and any significant ration change also cause breaks. Try to ease stress by keeping heifers in-groups no larger than 10-15, and separate them from older cows, if possible.
Make sure calves get a good dose of quality colostrum immediately after birth. Re-evaluate your vaccination program, and deworm calves. Keeping the immune system strong and eliminating concurrent worm burdens allows calves to better withstand coccidiosis.
Dairies often adapt a strategy of continual medication against coccidiosis as a prevention. However, with an understanding of the disease's cycle and knowledge of your infection level, you can adopt a strategic prevention that targets medication to the weak links.
Targeting a product like CORID to the first weeks of a calf's life and during key times of high stress - at weaning, prior to parturition, and during a major ration changes - helps control the cycle of reinfection that's only masked by continual medicating.
CORID's flexible administration is also important during an outbreak because it can be given as a drench, in drinking water as well as in the feed. Calves are exposed to infection long before they can consume feed, and you can't always depend on feed-through product increases your treatment options. Also, as long as calves are feed, Amprovine is a good choice for treatment and prevention as well. Amprovine is available in a soluble solution for water treatment as well as in a feed formulation.
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