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Farm & Ranch

Bovine Papillomavirus (Cattle Warts)

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Bovine warts are the ire of cattle producers. These unsightly masses typically appear on the head, neck, and body of the animals. Although these masses are usually more of a cosmetic issue than a medical concern, they can cause problems for producers. Warts reduce the value of animals through loss in sales, reduced weight gain, and loss of milk production. The warts also create havoc with cattle exhibitors since cattle shows bar any animals with contagious conditions from entering the show ring.

Cattle warts are caused by the bovine papillomavirus (BPV) which is a member of the Papillomaviridae family. BPV is found throughout the world wherever cattle are present. Several different genotypes of BPV have been found. Most of the genotypes are species specific which means cattle warts are not contagious to other species like humans. A few exceptions have been found. For example, BPV can infect horses resulting in equine sarcoid tumors.

Transmission of the virus occurs when the virus enters the skin through some type of abrasion or wound. This can be accomplished through direct contact between animals. It can also be spread by contact with objects contaminated with the virus. Some research indicates the possibility of insect transmission.

While some cattle are infected with BPV and never display any clinical signs of the disease, those that do show clinical signs are usually found in cattle less than 2 years of age. BPV is associate with cutaneous papillomas or fibropapillomas. A papilloma is a lobulated benign tumor arising from the skin. A fibropapilloma is a papilloma containing a large amount of fibrous tissue. Typically, the warts have a cauliflower appearance or are round hairless raised areas on the skin. The skin tumors can be found all over the body. If warts are found in certain areas such as the prepuce, penis, vaginal area, or teats, problems with reproduction, milking, or bleeding may occur. Secondary bacterial infections can also be a problem in cattle with warts. Tumors associated with BPV involving the gastrointestinal tract have been found in cattle. The masses are found on the mouth, tongue, esophagus, and digestive tract. The tumors are normally benign unless the animal is immunocompromised. In other countries, BPV has been associated bladder cancer. These cattle typically consume large amounts of bracken fern, are immunocompromised, and are infected with BPV. Bracken fern is not typically eaten by cattle in the United States.

Following an immune response, most warts spontaneously regress in a few months. However, due to their unsightly nature, many cattle producers want to get rid of the warts as fast as possible. This has led to a variety of treatments. Practices such as feeding cattle the crushed pieces of the wart, pinching off the warts, and applying different types of topical treatments have been tried. Unfortunately, very few if any of the above-mentioned treatments have been scientifically studied, so recommendations are based on experience and opinions. Cattle producers should consult with their veterinarian for the best treatment options.

Prevention of warts requires producers to follow biosecurity protocols. Never introduce an animal with warts to the herd. If any animal in the herd develops warts, the animal should be isolated and returned to the herd only after the completely healed. Keep all areas of the ranch clean. Especially, sanitize areas where cattle have contact such as feed bunks, water troughs, and places where cattle might rub or scratch.

Commercial vaccines are available. Vaccine failure may occur if the strains of the virus in the vaccine do not match the strain causing the infection. To avoid this issue, cattle producers may want to have a vaccine developed by a laboratory with a specific strain. This can be accomplished with the help of a veterinarian.

Fortunately, if producers are patience, warts will spontaneously regress in time. If producers cannot wait, they should consult with their veterinarian for the best treatment options. For those producers that have problems with warts every year, a vaccine should be considered. If producers would like more information on bovine papillomavirus, they should consult with their veterinarian and/or Oklahoma State University Cooperative Extension County Agriculture Educator.

Read more in the July 2022 issue of Oklahoma Farm & Ranch magazine.

References

Bocaneti, Altamura, G., Corteggio, A., Velescu, E., Roperto, F., & Borzacchiello, G. (2016). Bovine Papillomavirus: New Insights into an Old Disease. Transboundary and Emerging Diseases, 63(1), 14–23.

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Farm & Ranch

Acorn Toxicity

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Barry Whitworth, DVM

Area Food/Animal Quality and Health

Specialist for Eastern Oklahoma

With the prolonged drought, most pastures in Oklahoma are in poor condition. With the lack of available forage, animals may go in search of alternative foods. If oak trees are in the pastures, acorns may be a favorite meal for some livestock this fall. This may result in oak poisoning.

Oak (Quercus species) leaves, twigs, buds, and acorns may be toxic to some animals when consumed. Obviously, acorns can be a problem in the fall and green acorns can be more toxic than mature acorns. When acorns form only a small portion of the diet, there are usually no signs of problems. However, consumption of large quantities may result in toxicity. Tannins in the acorns cause the toxicity. The most common tissue damaged by the tannins are the digestive tract and kidneys. Cattle and sheep appear to be more susceptible to toxicity than goats. Other animals such as horses, rabbits, and chickens have succumbed to the toxicity of oak poisoning as well. Interestingly, some individual animals are more tolerable of the toxins and show no ill effects when consuming acorns.

Clinical signs of oak toxicity usually appear a few days after consumption of acorns. Initially, the animals are weak, listless, emaciated, and anorexic. This is followed by ventral edema (swelling of lower parts of the body such as legs, chest, ventral abdomen), urinating large amounts of urine, abdominal pain, and constipation. The animal may pass hard mucus covered fecal material which may change to black tarry or bloody feces as the disease progresses. If the animal is not treated, kidney failure is likely.

A tentative diagnosis of acorn poisoning may be based on clinical signs and access to acorns. Blood tests that indicate kidney disease is another clue to the condition. A necroscopy with examination of tissues for characteristic lesions of the disease is the standard to confirm a diagnosis of oak toxicity.

Treatment of oak toxicity starts with removing the animals from the area where the acorns are located. Those animals displaying signs of the disease should be given fluids to correct dehydration and electrolyte imbalances. Mineral oil and/or activated charcoal may be given to reduce toxin absorption. If animals survive the initial toxicity, they may recover, but it may take several weeks for kidney function to return to normal.

As always, prevention is better than treatment. Producers should be very careful allowing livestock to graze in areas where acorns are present. Livestock should be fed plenty of hay and feed this fall to avoid over consumption of acorns. For those producers who cannot avoid grazing areas with large numbers of oak trees, feeding a grain mixture with 10% to 20% of calcium hydroxide has been successful in preventing problems with acorn poisoning.

Two thousand twenty-two has not been the best year for livestock producers. The drought has produced poor pasture conditions as well as very little hay. On top of those problems, feed costs continue to increase. The last problem a producer needs is a large number of sick cows. For those that graze an area with a large number of oak trees, prevention may be worth the cost this year. At the very least keep a close watch of your animals this fall. Producers wanting more information about oak toxicity, should consult with their local veterinarian or visit with their Oklahoma State University Cooperative Extension County Agriculture Educator.

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Farm & Ranch

Fescue Foot

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Barry Whitworth, DVM

Area Food/Animal Quality and

Health Specialist for Eastern Oklahoma 

Since most of Oklahoma experienced drought conditions and with fall fast approaching, producers with fescue pastures should closely observe their livestock for any signs of fescue toxicity. According to Mike Trammel, Pottawatomie County Ag Educator and Muti-County Agronomist, fescue toxins (ergot alkaloids) tend to increase in Kentucky-31 tall fescue pastures in the fall. Some reports indicate more problems with fescue toxins following a summer drought and limited fall rains. All of this may put Oklahoma cattle at a greater risk of fescue toxicity.

One issue that cattle experience with fescue toxins is fescue foot. Fescue foot is thought to be caused by ergot alkaloids such as ergovaline. These alkaloids are produced by endophyte fungus (Epichloë coenophiala) which is in tall fescue. Ergovaline has been proven to be a vasoconstrictor which might be responsible for fescue foot and heat intolerance also known as summer slump in cattle. Other issues that may be seen with the ergot fescue toxins are reduced milk production and reproductive issues.

Clinical signs of fescue foot appear within a few days of cattle being turned on to tall fescue pastures or it may take weeks if toxins in the pasture are low. Producers will initially observe cattle with arched back, rough hair coats, and sore feet. These symptoms are more noticeable early in the morning and with cold weather. This is followed by reddening and swelling in the area between the dewclaws and hooves. The lameness usually becomes more severe with time. If no action is taken, gangrene will result in loss of tissues distal to the coronary band and declaws. If the weather remains mild, other signs such as increase respiration rate, increase heart rate, and higher body temperature are more common.

Other causes of lameness in cattle must be differentiated from fescue foot. One simple method that will help differentiate fescue foot from footrot is to check the temperature of the foot. If the foot is cold, this is an indication that the problem is more likely fescue foot.

Since there is not a specific treatment for fescue foot, the condition must be managed. Cattle need to be observed daily for any signs of lameness or stiffness during the first few weeks on fescue pastures. This should be done early in the morning before cattle walk off the stiffness. Producers should pay close attention during cold weather, especially when rain, snow, or ice are present. Any animal showing clinical signs of fescue foot should be removed from the pasture and placed in a clean environment. The animal should be fed a ration with no fescue toxins.  

The best but most costly solution to reduce fescue toxicity is to renovate old pastures with new endophyte friendly varieties. If this option is not possible, producers might try interseeding fescue pastures with clovers or other grasses. This should dilute fescue toxins. Nitrogen fertilization may increase ergot alkaloids, so producers should avoid fertilizing fescue pastures with high amounts of nitrogen. Researchers have demonstrated that feeding a supplement while grazing fescue pastures reduces clinical symptoms. Some studies indicate a difference in susceptibility to fescue toxicity in some cattle. Selecting cattle based on genetic tolerance of fescue toxins is an option. (For more information go to www.agbotanica.com/t-snip.aspx)

With large areas in Oklahoma covered with Kentucky-31 fescue pastures, fescue foot as well as other fescue toxicities are not going away any time soon. Livestock producers will need to watch their livestock closely for any signs of fescue toxicity and manage their pastures to keep toxins as low as possible. If producers would like more information on fescue foot, they should consult their veterinarian and/or visit their local Oklahoma State University Cooperative County Extension Agriculture Educator.  

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Farm & Ranch

Dropping Like Flies-Prussic Acid in Cattle

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As the year progresses many producers look to move cattle to alternative pasture. Unfortunately, certain weather conditions, including drought or freezing, can set up some plants in the sorghum family, including Johnson grass, to become toxic. Even after limited grazing, deaths may be seen due to the ingestion of prussic acid, also known as hydrocyanic acid or cyanide. A classic call to the veterinarian is, “My cattle are dropping like flies.”

Prussic acid toxin is created when the harmless hydrocyanic glycosides in plants are stressed and breakdown. Once the hydrocyanic glycosides in the plants are damaged through actions like cattle chewing or a swather and crimper, they quickly convert to prussic acid.  Following ingestion, the prussic acid is released in the rumen and rapidly absorbed into the blood stream. 

Once in the circulatory system, the toxin prevents cells from taking up oxygen. The blood therefore becomes saturated with oxygen leading to blood that appears bright cherry red. The clinical signs most often seen include excitement, muscle tremors, increased respiration rate, excess salivation, staggering, convulsions, and collapse. Asphyxiation at the cellular level is the cause of death due to deprivation of oxygen. 

When producers encounter animals displaying clinical signs of prussic acid toxicity, they should immediately remove all the animals that appear normal to a new pasture and contact their veterinarian.  The veterinarian will treat the sick animals with two drugs (sodium nitrite and sodium thiosulfate) that can reverse the toxicity. Treatment must be initiated quickly but can prove difficult due to the rapid progression of the toxin.

The drugs used to treat prussic acid toxicity can be difficult to obtain. It is advisable to contact your veterinarian before grazing potential toxic plants to make sure that your veterinarian will have availability to respond and the necessary drugs on hand to treat the cattle if a problem arises.

Read more in the August 2022 issue of Oklahoma Farm & Ranch.

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