Reproductive Failure caused by Neospora Caninum

Posted on May 13, 2012 by

Neospora Caninum is a parasitic disease of cattle that causes reproductive failure, primarily abortion. The infection is caused by a small single-celled protozoan parasite – Neospora caninum. The parasite gets into the brain and nervous tissue of a developing fetal calf and causes it to abort. Those calves that survive the infection are often born abnormal.

This is a relatively new infection of cattle that was first recognized in 1988. It has been more of a problem in the western states, but has recently (1999 2005) been diagnosed here in Georgia. At one time, 42 percent of all cattle abortions in California were diagnosed as having been caused by Neospora Caninum. This has the potential to become a significant problem in the Georgia cattle industry.

Signs in Your Herd

The primary sign of a herd infection is abortion. This is especially true when a herd is infected for the first time. Clinical signs associated with neosporosis, other than abortion, have only been described in cattle younger than two months of age.

Abortion is the only clinical sign seen in infected cows above this age. Cows of any age may abort between three months and nine months of gestation, but the typical time is five to six months of pregnancy when they abort. A number of different things, however, may happen to infected fetuses: they may abort, be reabsorbed, turn into mummies, be stillborn, or they may be born alive but diseased. Occasionally, calves are born diseased but look normal and will be chronically infected so that they may abort as first calf heifers.

Affected calves may be underweight, unable to rise or may have no outward signs. Infected calves may have their eyes affected. They may have small or misshapen eyes. Calves that are born alive may show signs of infection that are related to the nervous system, including having seizures or their hind limbs may be held in rigid flexion or extension.

Transmission of the Disease

The transmission of this disease follows one of two routes. In the first route, a dog or potentially a coyote or fox is involved in transmission. An aborted fetus will have a large number of infective Neospora Caninum in its brain, nervous tissue and other tissues. If a dog consumes the fetus, it becomes infected and a carrier of the disease.

Dogs may have signs of infection, but most importantly to the cattle industry, they will pass the Neospora Caninum in their feces. If the dog passes feces in feed, forage or water, cattle can ingest this, and when pregnant this can lead to infection of the fetus and subsequent abortion. The cow herself is likely to resist infection.

The second route of infection is more direct. Neosporosis may be transmitted from an infected cow or heifer to the calf during pregnancy through the placenta. If the calf survives, it will be infected for life, which is known as congenital infection, and is likely to abort subsequent calves.

Diagnosis

Diagnosis of Neospora Caninum is made by examining aborted fetuses or affected newborn calves. The nervous tissue of infected fetuses is the best specimen to examine. Somewhere in the nervous system, usually the brain, you will find microscopic evidence of this disease.

To diagnose this disease you need to have your veterinarian submit the aborted fetus and/or serum from the cow to a diagnostic lab. A positive serum titer of the disease from a blood or serum sample is only a presumptive diagnosis as the cause of abortion, but certainly indicates the cow has been exposed. A negative blood test, however, does not completely rule out neosporosis as the cause of abortion, as even some infected cattle can harbor the organism without exhibiting an immune response.

Previous vaccination will produce a positive serum titer to the disease, and this could possibly be confused for signs of infection. In an unvaccinated cow, a positive titer is indicative of exposure in that cow, but not necessarily infection. Definitive diagnosis is made by direct visualization of the organism in affected tissue using a microscope and ruling out other potential causes of abortion such as noninfectious causes or infectious diseases like IBR, BVD, trichomonas, vibrio or leptosporosis.

Prevention

Prevention centers around biosecurity and vaccination. Killed vaccinations are available and may decrease the incidence of disease, but may not completely protect an individual cow given a high exposure to Neospora Caninum. Two vaccinations two to four weeks apart are necessary along with annual boostering.

Checking serum titers of new additions and heifers pre breeding for antibodies to Neospora Caninum and eradication of positive cattle may be a good idea. This practice, however, may not eliminate congenitally infected cows that are not actively producing antibodies from the herd. In a herd where Neospora Caninum status is unknown, testing serum titers of at least 10 percent of the herd may help identify whether or not Neospora Caninum is a problem. In a negative herd, vaccination can be limited to only incoming additions and replacement heifers.

Keeping feed sources free of contamination is the key to controlling Neospora Caninum. Keeping feeders off the ground, using tarps to cover feeds, good fencing around feed storage areas and other measures can help prevent contamination by dogs, coyotes and foxes.

Conclusion

Overall, neosporosis has the potential to become a devastating disease for the cattle industry. Already, Neospora caninum has been found in several herds in Georgia and could potentially spread throughout the state. Fortunately, this disease can be managed in your herd through good biosecurity techniques and/or the use of strategic vaccination.

This article about reproductive failure caused by Neospora Caninum by Mel Pence DVM and co-authored by Elizabeth Cuttin, Derrich Phillips and Dodd Sledge, University of Georgia College of Veterinary Medicine, appeared in the April 2007 issue of Cattle Today.

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Fly Control in Cattle

Posted on May 12, 2012 by

Fly control can both add value and improve performance of cattle. Face flies and horn flies are an annual problem on beef cattle. The fly season starts in April and runs through September.

Flies reproduce rather rapidly, which makes them more difficult to control. Horn flies have a generation about every two weeks and face flies every eight to 10 days.

Horn flies are blood suckers that irritate cattle and interfere with feeding and resting. Face flies also annoy cattle, interfere with feeding, cause excessive eye secretions, and transmit pink eye, which results in reduced weight gain and milk production. USDA research reported that heavy infestation of flies resulted in cows losing about one-half pound of weight daily and a 20 percent reduction in milk production. The Tennessee beef industry annually loses millions of dollars due to these two pests.

“On-the-farm” demonstrations conducted in Tennessee in 2001 showed that backgrounded calves “tagged” with insecticide treated ear tags gained 2.34 pounds per day compared to 1.6 pounds in the control group (non-tagged). Over a 120-day period, this would produce an extra 88 pounds per animal. In cow-calf herds, calves from herds treated with various insecticide treated ear tags gained 2.84 pounds per day compared with 1.90 pounds per day for calves with no fly control. Over a 120-day period, this would total more than 100 pounds extra weight to market. The level of response to fly control will also be influenced by the level of infestation.

Considering the added weight gain due to fly control and the reduced value of feeder cattle that results from pinkeye infection, producers can easily see the economic advantages to controlling flies.

Plan fly control strategy early. Methods of fly control include spot-ons, pour-ons, dusts, dips, sprays, backrubbers, oral larvacides, boluses and ear tags. Consider what was done the past year or two when making plans for this year. Insecticide impregnated ear tags have been one of the most popular methods of fly control since they became available. There are three main groups of ear tags: those that are impregnated with an organophosphate, those with a synthetic pyrethroid and those with both. Use a tag which has either a phosphate or a pyrethroid but not both. Flies tend to become resistant to an insecticide that is used for several consecutive years. Therefore, alternating between the phosphates and pyrethroids each year is recommended.

Since most ear tags are effective for only about five months, researchers also recommend waiting until the first of May to place them on the ears of cattle. This is later than would normally be recommended for more conventional methods of fly control.

When winters are mild, flies may become a problem earlier than normal. You may need to use several sprays or a backrubber until ear tags are in place.

A combination of practices may be needed periodically during the fly season. If tags are used and flies begin to build up in the peak fly season, supplemental treatments such as a spray or pour-on may be necessary to bring them under control.

In summary, evaluate last year’s fly control program. If an ear tag was used, rotate to a tag with a chemical of a different family. Keep close watch on the fly population and use a supplemental control measure if necessary. Have a plan in mind.

This artciles about fly control by Bene Burgess & James B. Neel appeared in the June 2002 issue of Cattle Today.

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Colostrum Builds Immunity 2

Posted on May 11, 2012 by

Absorbing Antibodies •

There are several types of antibodies present in the cow’s colostrum. Their absorption rate and role in disease prevention varies depending on the class of antibody (IgG, IgM, IgA). Some are designed to be absorbed immediately and directly through the calf’s intestinal wall, where they enter his lymph system and bloodstream to be ready to fight disease organisms, while others stay in the gut and attack any pathogens found there-such as E. coli bacteria.

This is why it is important a calf nurse quickl -to be able to absorb the immunoglobulins that must go through the intestinal wall before it thickens and continue to have some colostrum during his next several nursings to keep the other type of antibodies in his gut to protect against scours bacteria he may ingest from the cow’s dirty teats or a dirty environment. The remaining antibodies in his mother’s dwindling supply of colostrum (as it becomes diluted with regular milk) can continue to be of benefit to him even though he can no longer absorb them through the gut lining.

The crucial antibodies he needs in his bloodstream are absorbed by a process called pinocytosis, which involves creation of a fluid pocket that aids in movement of antibodies through the wall of the intestine and into the lymph system. This works best when the calf is first born and his gut lining is thinnest, making it easier for the big molecules to slip through. The lining begins to thicken right after birth and the rate of pinocytosis decreases the older the calf gets. He gets maximum antibody absorption if he nurses within the first 15 to 30 minutes after birth.

Once he starts to nurse, the gut closure process is hastened even more. This is probably mother nature’s way to insure that nothing else will slip through the intestinal lining (such as bacteria or viruses) after he is up and around and sampling his new world. Thus it is important that he have a full feeding of colostrum very soon after birth and not just a small amount. If a calf is cold and weak and only able to nurse a little bit at first, or if you feed him just a small amount rather than a full feeding, this will speed up the closure of his gut lining and he may not be able to absorb any more antibodies by his next nursing. After his gut closes he will only get the benefit of antibodies that fight a few pathogens in the gut itself.

Antibodies in the calf’s bloodstream obtained via colostrum can help him fight off blood-borne infections caused by bacteria such as salmonella, pasteurella and streptococcus, but they cannot directly prevent gut infections such as those caused by E. coli. But high levels of certain antibodies in the blood can help reduce the severity of scours, and the antibodies that stay in the gut after the intestinal wall closes (from the colostrum ingested by the calf in subsequent nursings) can attack any scours-causing pathogens found there.

The number of colostral antibodies that fight scours organisms such as E. coli can be increased by vaccinating the cow ahead of calving, making sure the vaccine is given far enough ahead (at least two weeks) that she can develop the necessary antibodies, and not so far ahead (no more than 50 days) that her immunity level is dropping. Some types of scours can be prevented by giving the calf a commercially prepared concentrated antibody source or oral vaccine soon after birth (such as the oral viral vaccine against rotavirus and coronavirus, which works best if given within 4 to 6 hours of birth).

Heifers’ Calves • Calves that have an adequate amount of high-quality colostrum immediately after birth have a much better chance of fighting off the diseases they will encounter. Heifers’ calves are at greater risk than calves from older cows, however, since heifers’ colostrum does not contain as many antibodies and also has less variety of antibodies because young cows have been exposed to fewer infectious organisms in their short lives. Heifers may also have less volume of colostrum, due to less udder development than an older cow. And a heifer’s calf may not be able to absorb as many antibodies as he should since he may be slow to nurse if the birth was difficult. And the stress of a hard birth makes him less able to absorb antibodies efficiently; stress may affect his absorption even if you make sure he gets a large amount of colostrum.

Prevent Failure Of Passive Immunity •

The main reason calves get sick in the first few weeks of life is inadequate passive immunity, due to not enough antibodies absorbed immediately after birth. If you make sure calves nurse promptly, this problem can be greatly reduced. By the time a calf is four hours old he has lost 75 percent of his ability to absorb antibodies, and absorption rate decreases rapidly after that. Any calf that has not been able to nurse on its own in the first hour or two after birth should be assisted, or given colostrum by bottle, stomach tube or esophageal feeder. A calf needs to have about five percent of his body weight soon after birth (1.5 quarts for a 60-pound calf, 2 quarts for an 80-pound calf, 2.5 quarts for a 100-pound calf), and the same amount again about 6 hours later.

Active Immunity •

Calves lose their temporary immunities (the protection gained from antibodies via colostrum) by seven or eight weeks of age, or even earlier. So at that time their own immune system must take over.

The time it takes for a calf’s immune system to gear up so it can ward off invaders will vary, depending partly on how strong his passive immunity was. If he had a high level of antibodies from his dam’s colostrum, which effectively neutralized any invading organisms, his own defenses are not stimulated to develop until that protection begins to wear off.

The antibodies gained through colostrum can also interfere with effectiveness of vaccinations. If a calf is vaccinated young, while he still has high levels of maternal antibodies in his blood, his own immune system will not bother to respond to the antigens in the vaccine because they are being neutralized by the maternal antibodies. A vaccination given to a calf when he is only two or three weeks old will not give him any protection, since it will not stimulate immunity. Most vaccines should be given at eight weeks of age or older, and repeated with a booster shot two to six weeks later to make sure the calf’s immune system will be able to respond.

This article about immunity building through colostrum by Heather Thomas Smith appeared in the March 2002 issue of Cattle Today.

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Colostrum Builds Immunity 1

Posted on May 10, 2012 by

Illness occurs when an animal’s body is overwhelmed by infection. A healthy animal with strong immunities is less likely to become sick than an animal with poor immunity. Immunity refers to the body’s ability to fight off bacteria or viruses, and this ability is developed in a complex process in which the body creates specific weapons for fighting specific invaders.

Antibodies •

When a virus or bacteria enters the body, it starts invading tissues and causing damage by multiplying and creating toxic products. This damage stimulates the body to create an antibody (a serum protein called an immunoglogulin) to react with the invading agent and neutralize it. The antibodies are carried throughout the body in the bloodstream. The main role of one type of lymphocyte (white blood cell) is to produce antibodies?the proteins that can neutralize certain infectious agents.

If an animal already has antibodies against a specific disease organism, then any time that particular organism invades the body again an army of white blood cells (with their antibodies) converge on the site to kill the invader. Exposure to one strain of an organism may result in immunity to that specific strain, but not to other strains of the same organism. Antibody immunity depends on the level of exposure, and stresses on the animal and its current health. A severe outbreak of disease in a herd may eventually break down a healthy animal’s immunities, and will overwhelm a stressed animal’s defenses even sooner.

Vaccination can stimulate production of antibodies, since the vaccine serves as the antigen (like an invading pathogen). The body builds protective antibodies to fight the “invader.” Then when the animal comes into contact later with the actual infectious agent, the antibody is present in the bloodstream and able to inactivate the pathogen. If enough antibodies are present to inactivate all the agents that invade the body, the animal will not get sick, and the invasion stimulates rapid production of more antibodies for future protection.

A cow in a natural environment may not become exposed to very many disease-causing organisms, but today most cattle are confined some parts of the year (in corrals, small pens or pastures that have been very contaminated by heavy cattle use) and comes in close contact with other cattle-with much more chance of disease spread. But with vaccination and natural exposure to various pathogens, the cow develops many antibodies and strong immunities. And during the last part of pregnancy she puts these antibodies into the colostrum she produces, so that her calf can have some instant immunities right after he has his first nursing.

The antibodies in colostrum are very important to the new born calf because he has very little disease resistance of his own. The fetus can begin to produce antibodies against certain pathogens at various stages of development (for instance a fetus can start to make antibodies to BVD and IBR as early as 90 days into gestation, and against leptospirosis bacteria after 180 days), since some of these invaders can pass through the placental barrier from the mother’s bloodstream if she becomes infected. This is why a fetus can become infected with BVD or other diseases or die from lepto or Bangs and be aborted. Certain infections in the cow can kill the fetus or cause it to be born diseased, or cause it to start making some antibodies of its own.

But this fetal immunity doesn’t do the calf much good when he is born. This is because the immunity of the fetus decreases at the time of birth. For a few weeks before calving and for a short while afterward, the calf’s immune system is hindered by the high cortisol levels present in both the cow and calf-part of the hormone activity that helps stimulate birth. Cortisone interferes with the activities of the immune system-one reason to never keep an animal on steroid-type drugs for more than just a few days.

Passive Immunity •

For about 10 to 14 days after birth, a calf cannot begin to build any immune responses against infectious agents. This is why young calves are very vulnerable to diseases such as scours and pneumonia. But mother nature has this loophole covered.

To help protect calves during this precarious period, the antibodies needed are provided in the cow’s first milk, to give the calf a temporary or passive immunity against the many challenges he will soon face.

Passive immunity can be obtained from some source outside the body, such as with use of antiserum, or ingestion and absorption of colostrum. Antibodies in a cow’s bloodstream are unable to cross the placental barrier because these molecules are too large. A calf can receive the antibodies from his dam only from drinking her colostrum. During the last three weeks of pregnancy she accumulates antibodies from her bloodstream into her mammary glands; a well-fed, healthy cow produces an abundant amount of colostrum and therefore a large volume of antibodies. You can maximize her colostrul antibodies by making sure she is not too thin (undernourished cows produce less total colostrum), and that her vaccinations are up to date so she will have produced a high level of antibodies against those specific diseases.

At the time she gives birth, the concentration of antibodies in her milk reaches its highest peak, then drops rapidly. It is important that the calf nurse as soon as possible after birth to get full benefit from her antibodies.

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Calf Scouring and Diarrhea 2

Posted on May 9, 2012 by

Infectious Agents Play a Major Role

2. Bacterial Scours – Caused by Bacterial Infection

A. Escherichia coli (Colibacillosis).

Escherichia coli (E. coli) has received a huge amount of coverage in the press as a health concern for humans and it has also been incriminated as a major cause of calf scours. Many different kinds of E. coli have been identified; some cause scours while others do not. E. coli is always present in the intestinal tract and is usually the agent that causes a secondary infection following viral agents or other intestinal irritants. E. coli scours is characterized by diarrhea and progressive dehydration. Death may occur in a few hours before diarrhea develops. The color and consistency of the feces are of little value in making a diagnosis of any type of diarrhea. The course varies from 2 to 4 days, and severity depends on age of the calf scours starts and on the particular type of E. coli. Diagnosis depends on an accurate history, clinical signs, and culture of internal organs for bacteria and typing of the organism. Control of E. coli scours can be difficult in a severe herd outbreak. All calves should receive colostrum as soon after birth as possible. This helps the calf resist E. coli infection. Early isolation and treatment of calf scours helps to prevent new cases. There are new E. coli cow vaccines now on the market which is administered to the cow 6 weeks and 3 weeks prior to calving. The new E. coli vaccine is also available in combination with the rota- and coronavirus vaccine. This vaccination builds high antibody levels in the colostrum, but the calf must get colostrum in the first few hours of life for the vaccine to be effective.

B. Salmonella.

There are more than 1000 types of salmonella, all of which are potential disease producers. Salmonella produces a potent endotoxin or poison, within its own cells. Animals may be more severely depressed following treatment with antibiotics as treatment causes the salmonella organisms to release the endotoxin, producing shock. Therefore, treatment should be designed to combat endotoxic shock. Calves are usually affected at 6 days of age or older. This age corresponds very closely to the age of the coronavirus infection. The source of salmonella infection in a herd can be from other cattle, birds, cats, rodents, the water supply, or even a human carrier. Clinical signs associated with salmonella infection include diarrhea, blood in the feces, depression, and elevated temperature. The disease is more severe in young or debilitated calves.

C. Enterotoxemia.

Enterotoxemia can be highly fatal to young calves. It is caused by toxins produced by Clostridium perfringens organisms. There are 6 types of Clostridium perfringens that can produce toxins, of which types B, C, and D appear to be the most important in calves. The disease has a sudden onset. Affected calves become listless, display uneasiness, and strain or kick at their abdomen. Bloody diarrhea may or may not occur. It is usually associated with a change in weather, a change in feed of the cows, or management practices that cause the calf to not nurse for a longer period of time than usual. The hungry calf may over-consume milk which establishes a media in the gut that is conducive to the growth and production of toxins by the clostridial organisms. In many cases, calves may die without clinical signs being observed. This disease is best controlled by vaccinating the cows with Clostridium perfringens toxoid 60 and 30 days before calving. A single booster dose of toxoid should be given annually thereafter before calving. If this problem is diagnosed in calves from nonimmunized cows, antitoxin can be given to the calf. Administration of antitoxin and oral antibiotics is the only treatment that is effective.

3. Other Causes of Scours

A. Coccidiosis.

Coccidiosis is caused by one-celled parasites that invade the intestinal tract of animals. There are many species of coccidia. Two, Eimeria zurnii and Eimeria bovis, are usually associated with clinical infections in cattle. Coccidiosis has been observed in calves 3 weeks of age and older, usually following stress, poor sanitation, overcrowding or sudden changes of feed. It often occurs in calves 7 to 14 days after they are moved from the calving lots onto pasture. Clinical coccidiosis is generally diagnosed by finding significant numbers of parasites in the feces. A typical sign of coccidiosis in young calves is diarrhea with fecal material smeared over the rump as far around as the tail will reach. This may or may not contain blood. Death may occur during the acute period or later from secondary complications. Sulfonamides have been the treatment of choice for coccidiosis for many years. If treatment is given before signs appear, the disease can largely be prevented. Amprolium has been cleared for use in calves as a preventative. This should be supplied at the rate of 5 mg/kg of body weight for a period of 21 days to cover the time period during which this disease is anticipated. Good feeding practices, management, and sanitation are the control methods of choice.

Nutritional Scours

Under range conditions, a calf adapts a pattern of nursing that fills his needs. Nutritional calf scours can be caused by anything that disrupts this normal habit. A storm, strong wind, or the cow going onto new grass disrupts the normal nursing pattern. When the hungry calf does get an opportunity to nurse, the cow’s udder may contain more milk than normal and the calf may overeat resulting in nutritional calf scours. Erratic nursing patterns may also be conducive to enterotoxemia. Nutritional calf scours is usually white scours caused by undigested milk passing through the intestinal tract. This type of calf scours usually presents little problem in treatment. If the affected calves are still active and alert, no treatment is required. If the calf becomes depressed or fails to nurse, it should be treated. Oral antibiotics can be used as a treatment.

Treatment of Calf Scours

Treatment for calf scours is very similar regardless of the cause. It should be directed toward correcting the dehydration, and electrolyte loss. Antibiotic treatment can be given simultaneously with the treatment for dehydration. Dehydration can be overcome with simple fluids given by mouth early in the course of the disease. If dehydration is allowed to continue, intravenous fluid treatment becomes necessary. The clinical signs of dehydration first occur when the fluid loss reaches 5 to 6 percent of the body weight. Ten percent loss of fluid results in depression, sunken eyes, dry skin, and the calf will probably be unable to stand. A 15 percent loss of fluids usually results in death. Oral fluids used early in the scouring process have been quite successful. Consult your veterinarian for electrolytes to be given orally. There are dry electrolyte powders available that can be mixed with water for oral administration.

Conclusions

It is apparent that many factors can create a scouring situation in young cattle. The one factor that we observe, however, is that in almost every situation, prevention is linked to the appropriate intake of colostrums by the calf within a few hours of birth. It is important that calving conditions are good and that the producer observes newly born calves to insure that they are up and suckling as soon as possible. Additionally, a good herd health program is extremely important to prevent a potential onset.

This articles about calf scours and calf diarrhea by Dr. Steve Blezinger, a nutritional and management consultant, appeared in the March 2001 issue of Cattle Today 

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