Sick Dairy Calves: Coccidiosis and Cryptosporidiosis in Dairy Calves

Dealing with Coccidiosis and Cryptosporidiosis in Dairy Calves

Dairy calves and heifers are an important part of most dairy herds, since they will be the future cows.  Keeping baby calves healthy is a bigger challenge than keeping weaned and yearling heifers healthy; the older animals have usually developed more immunity to diseases and have fewer respiratory and digestive problems.

Diarrhea in calves is a common problem.  The diarrhea caused by the protozoan pathogens that cause coccidiosis and cryptosporidiosis are often the hardest to prevent or treat.  A farm may encounter significant incidence of disease during stressful events for the calves, or changes such as adjusting to new grouping or new diets, or after being transported to another location, such as a calf farm.  Transport is a stress, and the move can expose calves to new pathogens.

This disease is caused by a microscopic protozoan parasite–one of the most important causes of diarrhea in calves and young growing stock, resulting in slow growth and sometimes death.  Even though there are various types of this parasite that affect nearly every kind of mammal, coccidiosis has been studied in cattle more than in any other production animals except poultry.

Coccidiosis in cattle is caused by protozoa of the genus Eimeria.  More than 20 types of Eimeria have been identified in the feces of cattle worldwide but only four (E alabamensis, E auburnensis, E bovis, and E zuernii) are usually associated with clinical signs of disease in cattle.

The stress of this infection can hinder the animal’s immune system; these calves may become more susceptible to other diseases, especially respiratory disease, and the immune suppression may increase severity of the other disease.  Anything that hinders the immune system, including stress or corticosteroid injections, will allow the parasite to complete its life cycle more easily and produce additional oocysts.

After exposure, clinical signs and recovery, the animal will generally develop strong immunity.  Since these parasites are generally present in the environment (wherever there are cattle feces), there will be continued exposure during the animal’s life.  A few of these parasites will develop within that animal, stimulating immune response, enabling it to maintain immune resistance.

Immunity is only mounted against the specific Eimeria subspecies to which the animal is exposed; if a different type is encountered, the animal has no resistance and may develop coccidiosis again.  Adult animals typically shed a few oocysts now and then, which can infect calves.  There can be a rise in oocyst numbers during calving (a stress for the cow), which can contaminate the dairy’s calving areas.

Matt Akins (Associate Scientist and Extension Dairy Specialist at University of Wisconsin-Madison) says coccidiosis in dairy heifers often occurs during stressful events, especially if the heifer has not been previously exposed to the protozoa Eimeria bovis or Eimeria zurnii.  Coccidiosis is most often seen in calves and heifers from 1 month of age to 1 year of age; these protozoa can be prolific in facilities with poor manure removal, use of bedded packs (which are often just added onto and not completely removed), or inconsistent feeding of coccidiostat drugs to the calves.  Cases of coccidiosis in Britain increased after the mid-1990s, possibly due to the fact those dairies no longer routinely included coccidiostats in their calf feeds.

Adult animals always harbor a few of these protozoan parasites but have developed enough immunity that they rarely show any clinical signs.  Infection is always due to contaminated environments, particularly when conditions are moist.

Akins says the Eimeria lifecycle starts with the animal consuming the protozoa oocyst (egg). This can readily occur when calves ingest contaminated feed, bedding or water, lick themselves or other animals that have feces on their hair coat, or lick contaminated surroundings (walls, feeders, etc.).  The oocyst has a protective outer covering and can remain viable in moist, warm environments for several months to years.

After entering the digestive tract, the oocysts release infective sporozoites which penetrate the lining of the animal’s small intestine to replicate and form merozoites in the cells of the lining.  After a couple replication cycles in the small intestines, the merozoites sexually reproduce in the large intestine to form oocysts that can then be excreted in the feces and restart the life cycle.  In the process of breaking out of the intestinal lining, there is significant damage; the animal can’t readily absorb fluid and nutrients, resulting in diarrhea and dehydration, and often blood in the feces.

This cycle is continuously occurring, since the calves are ingesting oocysts daily, according to Akins.  The typical complete life cycle is 15 to 20 days so there is a delay of about 2 to 3 weeks from the time of first ingestion until you might see clinical signs.

Whether or not you see signs will depend on the parasite load.  Only a small percentage of cases actually show clinical signs (diarrhea, weakness, blood in the feces, etc.) because most cases are sub-clinical infections.  Even though you don’t see any signs, however, these infections can affect calves’ feed intake and growth.  Thus it is important to try to minimize parasite load, to reducing these negative impacts.

Most infected calves show no clinical signs. The animals appear healthy but pass a few oocysts in their feces.  Subclinical infection results in decreased growth that may not be regained. This is the most common effect, with no other clinical signs.  In subacute infections, the main sign is soft or loose feces, which will occur about 3 weeks (16–23 days) after infection for E bovis and E zuernii, but may appear only 3 to 4 days after infection with E alabamensis. The animals appear slightly dull with a poor hair coat and decreased growth rate.

When ingested parasite loads are high or the calves/heifers are under stress, clinical signs become more obvious—with reduced feed intake, diarrhea and weight loss.  Coccidiosis can severely affect growth when clinical signs occur.  By the time the animal is showing clinical signs, the protozoa have already completed their life cycle and the animal is excreting oocysts into the environment and perpetuating the problem.

Severe cases include lack of appetite, lethargy, diarrhea (possibly containing blood), signs of abdominal discomfort, and excessive straining with every bowel movement—sometimes to the point of prolapsing the rectum.  Growth rate is reduced, with poor feed conversion.  Severe cases usually involve dehydration, often with bloody diarrhea and sometimes anemia, muscle weakness, inability to get up, and death.  Occasionally a calf with coccidiosis will have convulsions and signs of central nervous system involvement. Chronic infections tend to result in poor growth, dull coat, and soiled hair.  Decreased weight gain can continue for at least the first grazing season.

Prevention involves trying to minimize parasite load in the environment– to prevent coccidiosis incidence and severity.  Akins recommends maintaining heifers in similar age groups (no older ones shedding oocytes into the environment to infect the younger ones), and cleaning all pens/feeders/waterers between moves.  In addition to maintaining a clean environment, most dairy operations use a coccidiostat (a drug like lasolocid, monensin, decoquinate, or amprolium that inhibits but does not kill the protozoa) in the feed mix to control the protozoa in the heifer’s digestive tract.

These coccidiostats minimize oocyst production and excretion into the environment.  Use of a coccidiostat enables the heifer to develop immunity to the protozoa while controlling the protozoal levels to minimize actual disease.  Coccidiostats work well in controlling incidence of clinical coccidiosis and maintaining heifer growth, but there can still be subclinical infection; producers need to be consistent with coccidiostat feeding to prevent clinical disease.

Proper feed mixing and administration are crucial to ensure proper dosage for controlling the protozoa.  An advantage of using certain coccidiostats (ionophores like lasolocid and monensin) are that these also act in the rumen to improve feed efficiency.

Akins says recent research at the University of Wisconsin-Madison Marshfield Agricultural Research Station explored the use of alternative feed additives to control coccidiosis in heifers that were transported from the Arlington research location–about a 3-hour transport.  “We used a novel egg-based antibody to interleukin-10 (IL-10) which may help maintain the heifer’s normal immune system.  The Eimeria protozoa is capable of ‘fooling’ the animal’s immune system by causing immune cells in the gut to produce IL-10, which is a communication signal to shut down the immune system,” he said.

“The antibody we fed is supposed to bind IL-10 in the digestive tract and allow the immune system to act normally.  Positive results were seen previously in some chicken and beef cattle studies.  However, we have not yet found positive results from feeding this antibody to dairy heifers, but will continue to evaluate this antibody as a possible coccidiosis prevention strategy.”

During this study, Akins and his colleagues found some other interesting results with the coccidiostat treatment group.  “Heifers fed a coccidiostat had lower fecal oocyst counts for the first 4 to 6 weeks of the trials, however after 6 weeks the heifers’ fecal counts were similar to the control and antibody treatments, likely due to them being moved into a bedded-pack barn.  The bedded-pack barn likely had a higher oocyst load as the pens were only divided by gates, and the bedding is groomed/mixed daily, thus spreading oocysts across pens,” he said.

The coccidiostat groups did have fewer clinical symptoms and treatments; the heifer’s immune system was able to adapt to lower protozoa levels over the first 4 weeks of the study.  This result shows the importance of facility cleanliness even if the animals are being fed a coccidiostat.

Treatment for coccidiosis with clinical signs (mainly diarrhea) should focus on controlling the protozoal infection and replacement of lost fluids and electrolytes.  Before treating the animals, however, it is important to work with your veterinarian to determine if the cause of signs is actually coccidiosis and not some other pathogen.  Diagnosis is usually done with a fecal test.  If oocysts are found in the feces, then an appropriate treatment strategy can be planned.  Keep in mind, however, that if the test is done early on in the disease, there may not be any oocysts being passed yet in the feces.

Amprolium is commonly used for treatment of calves and heifers with clinical signs, to quickly control the growth and reproduction of the protozoa in the animal’s digestive system.  Akins says amprolium mimics the B-vitamin thiamin when taken in by the protozoa, which causes a thiamin deficiency and energy deficit, ultimately killing the protozoa.

Treatment of the entire pen of calves is generally advised, even if only a few of the animals are showing clinical signs, because it is likely that the other animals are under stress from parasite loads or incubating an early infection.  The drug treatments are administered over a 5 day-period either by drench, or placing the drug in the water tank, or in the feed using a medicated pellet.  Use of fluid therapy (electrolytes) is also essential for the animals that have diarrhea, to reverse the dehydration. These animals can become severely dehydrated from coccidiosis.

The affect and success of treatment may be variable, depending on the extent of intestinal damage.  Because feed and water intake may be decreased, treatments for sick calves should be administered individually.  Always follow the label directions for treatment when using drugs for coccidiosis.

Diclazuril or toltrazuril administered to all affected calves and others in the group decreases oocyst production in the digestive tract. Some affected calves may still show clinical signs, but the oocyst counts decrease.

Sulfadimethoxine (as a drench or in the drinking water, at double dose for 1 day and then half that amount every 24 hours for 4 days) is often used. Sulfamethazine (sulfadimidine) is also used (in the drinking water or as a drench). Sulfaquinoxaline (in the drinking water–or by drench if a calf is not drinking sufficiently–for 3–5 days) is approved by the FDA for treating coccidiosis.  This drug seems to be particularly useful for weaned calves that develop bloody diarrhea after arrival at a feedlot.  Sulfonamide treatment via injection or IV may be necessary to control development of secondary bacterial enteritis or pneumonia, which may occur in calves that develop coccidiosis during cold weather.

Decoquinate given daily in the feed for 28 days can also treat coccidiosis in calves.  Amprolium in the drinking water, feed, or by drench, every 24 hours for 5 days is also used as a treatment course.  Drench is preferable when calves are sick and not eating or drinking, but use of amprolium in calves is controversial because it can cause thiamine deficiency and associated neurologic disease.  After treatment with amprolium, it is advisable to provide thiamine.

Besides use of coccidiostats, fluid therapy or blood transfusions may be needed in severe cases that show dehydration, dysentery, and anemia. Corticosteroids should not be given because they increase shedding of oocysts and may induce clinical disease in sub-clinically infected calves.

This is a common, often severe, gastrointestinal disease in young calves, typically 7–21 days old, or even quicker if a calf becomes infected soon after birth.  If a newborn calf encounters the parasite when trying to suckle on a dirty udder or any contaminated surface, it may break with diarrhea as early as 4 or 5 days of age.  This disease is caused by the protozoan Cryptosporidium parvum.  Clinical signs include yellow watery diarrhea, dehydration, and poor growth. Transmitted via the fecal-oral route, this parasite is highly resistant to standard disinfectants, requiring strict sanitation and supportive care (fluid and electrolytes) for treatment.

The protozoan parasite is transmitted via the fecal-oral route when the calf either ingests the oocysts in the feces or drinks contaminated water.  This disease is highly contagious and a calf can shed oocysts for up to a week after it recovers from diarrhea.

Life cycle for crypto is a little different than coccidiosis because the incubation time is shorter; the calves can get sick quicker.  Once ingested, the oocyst is activated by the pH and temperature in the calf’s abomasum; four sporozoites are released and travel to the small intestine of the calf, where the infection begins.  The parasite feeds on a cell in the intestinal wall, using nutrients that were intended for the calf’s intestinal cells.  This results in poor nutrient absorption, poor growth, and reduced feed efficiency for calves infected with the disease.

The parasite also reproduces in the intestinal lining, re-infecting the calf by infecting neighboring cells, and starting the reproductive cycle again.  Calves are thus infected in two ways: through ingestion of feces shed by infected calves, and through re-infection in their own lower gut by the parasite’s reproductive cycle.  When the oocysts are shed in the feces, they are enclosed in a thick shell, making them difficult to kill.

Prevention includes sanitizing pens between groups of calves to reduce pathogen loads but the proper disinfectants must be used.  This organism is resistant to chlorine and iodine-based disinfectant and can also survive in extreme cold and warm temperatures. Boiling water at temperatures of 160°F for three full minutes is required to destroy the oocysts. Hydrogen peroxide-based disinfectants can kill Crypto, and a 3% Hydrogen peroxide solution is safe to use around calves. Once all the soiled bedding in a calf pen is cleaned out, the pen can be sprayed with a 3% hydrogen peroxide solution.

You don’t want it to be any stronger than 3%; hydrogen peroxide at higher concentrations is more caustic and poses a risk to the people handling the solution. Protective gear should be warn when disinfecting facilities. A hydrogen peroxide solution should be rinsed from metal surfaces after 10 minutes because it is an oxidizer and can cause rust. Always allow the pen to dry before returning calves to that pen.

Crypto requires moisture to survive; it thrives in humid environments like calf barns. The easiest way to reduce parasite load in the environment is by frequently removing any soiled bedding from infected calf pens, and by cleaning bottles and buckets with very hot water followed by drying.  The protozoa is vulnerable to dying out.

Isolate sick calves away from healthy calves to prevent spread.  Feces from infected calves can quickly spread the organism to other calves.  Just one tablespoon of diarrhea from a calf with Cryptosporidium parvum is enough to infect dozens of other calves if they consume any of it.  Having an easy-to-clean area to house sick calves can help reduce the risk of disease transmission to other calves in the barn, regardless of the cause of diarrhea.

Treatment involves good supportive care to keep the calf warm and well hydrated—to enable the calf to fight off the disease.  Crypto is difficult to manage because there are no effective treatments.  Research in rats has suggested potential antiprotozoal activity against Cryptosporidium parvum using ivermectin at specific dosages, but ivermectin is not an approved treatment for cryptosporidiosis in cattle. The best strategy for calves with an active Crypto infection, much like any disease that causes diarrhea, is supportive care.

This involves providing rehydration solutions either by bottle (if the calf is not too dehydrated or gut-damaged to absorb oral fluids), subcutaneously, or intravenously.  Dairies should work with their herd veterinarian to develop a care plan to determine when these sick calves require rehydration solutions, and whether additional treatments are needed besides fluid and electrolytes.

Always remember that cryptosporidium parvum is zoonotic, meaning it is infectious to humans.  Anyone treating or working with sick calves should always wear gloves, wash hands after calf handling, even if wearing gloves, change and wash clothes it soiled by calf diarrhea, and wash hands before eating.  Young children, elderly people, and anyone with a compromised immune system may be especially vulnerable so you don’t want to bring this disease into a household.

A calf with diarrhea always needs access to clean drinking water because dehydration is the leading cause of death (with diarrhea from any cause). The dehydration status of a calf can be assessed in several ways, including a pinch test– pulling up a pinch of skin on the shoulders to assess for elasticity, to see how quickly or slowing it sinks back into place.  If it takes only one or two seconds for the tented skin to sink back down, the calf is only mildly dehydrated.  Say it takes three or four seconds the calf is moderately dehydrated.  If it takes six seconds or longer, the skin tissues are very short on fluid and the calf is severely dehydrated.

Another clue that a calf is dehydrated is lack fluid in the tissues around the eyes, making it look like the eyes are sunken into the head.  You can also feel the calf’s legs and ears for warmth.  If they are cold and the nose is dry and cold, these are indications of poor blood circulation due to dehydration.  You can also check the calf’s mucous membranes (such as mouth and gums) for dryness and color; a dehydrated calf will have dry or sticky mucous membranes and the gums will be pale or dark purple instead of pink.  Other clues are inability to suckle, dull attitude, and lack of response to human presence.

Mildly dehydrated calves need additional fluids, which can often be provided by oral electrolyte solutions because the calf can still absorb some fluid and nutrients in the intestine.  Moderately dehydrated may not want to suckle and appear slightly depressed.  They need fluid and electrolytes, but oral solutions via tube feeding may not be sufficient and they’ll need subcutaneous or intravenous fluids.  A severely dehydrated calf needs immediate IV fluids (and the proper electrolytes to correct metabolic acidosis) to survive.

These same principles regarding signs of dehydration and need for fluid therapy apply to any dehydrated calf, whether the cause is cryptosporidiosis, coccidiosis or some other cause of severe diarrhea.

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