As you prepare for County Fair and show season, it is important to be sure that your animals are healthy before and after the show. Knowing some signs of common diseases can be extremely helpful to keeping your whole herd healthy.
Warts are caused by a contagious bovine virus (papillomavirus). Four types of the virus are known to produce warts in cattle. Two of the viral types cause most of the warts found on the head and neck of cattle. All are described as “hardy” – meaning the virus will survive out in the environment for weeks or even months if it is protected by pieces of skin, a shed wart, or bits of tissue on a halter. Because of the infectious nature of the wart virus, animals with warts are disqualified from shows and exhibitions. A veterinarian pre-fair visit showing an indication of warts should mean that the animal does not even get on the truck to go to the event. The papillomavirus is widely distributed in cattle throughout the world.
Calves are most susceptible to warts and very few cases are ever seen in cattle over 2 years of age. Occasionally, warts may be found on the teats of lactating dairy cows. Cattle are the main source of the virus, meaning that in most cases, cows get it from other infected cows. However, it should be noted that halters, ropes, tattoo instruments, teat cup liners, or clippers can all serve as a potential source of infection spreading the virus from one animal to others. Calves are often unintentionally infected by tattoo or ear tagging equipment, halters, or dirty clippers. For that reason, it is important to clean clippers, tattoo and ear tag guns between cattle! Commercial vaccines are available, and if used as directed, they may help prevent warts in cattle not previously infected in a herd with warts.
Bovine Viral Diarrhea -BVD is most common in young cattle between the ages of 6 and 24 months. BVD is caused by the bovine viral diarrhea virus (BVDV), which is a member of the pestivirus genus. This virus is fairly widespread and common. In fact, it is found in all parts of the US and most of the world. Signs of acute cases of BVD are fever, depression, decreased milk production, lack of appetite, rapid respiration, excessive nasal secretion, excessive tearing, and of course diarrhea. Chronic and severe cases can develop into a mucosal disease which is fatal. This disease is economically important because it causes a reduction in milk production and fertility and the loss of young stock.
The BVD virus can be transmitted through the placenta from the dam to a fetus as well as through contact with feces of infected animals and by some insect vectors like flies. In pregnant cattle, when the virus crosses the placenta, the result depends on the stage of fetal development and the strain of the virus and can result in the development of a persistently infected (PI) calf. A persistently infected animal can appear normal but shed the virus and wreak havoc on reproductive performance in a herd. Infection of the dam may result in reduced conception rate, embryonic resorption, abortion, retarded fetal growth, congenital malformations of the eye and central nervous system, fetal mummification, premature birth, stillbirth, and birth of weak calves. Since the BVD virus is not the only potential cause of diarrhea in cattle, it is best to contact your veterinarian to rule out other causes and prescribe proper treatment.
Control of this disease is based on sound management practices including good bio-security, eliminating persistently infected (PI) cattle from the herd, and vaccination. Because this virus is shed in manure, it is imperative that when visiting neighboring farms, one should practice good bio-security and wear plastic booties or rubber boots which can be disinfected between barns. Vaccination of incoming as well as on-farm replacement cattle for BVD should be done before co-mingling with the rest of the herd. Embryo donors and recipients should be tested for persistent infection. Replacement calves should also be tested and under quarantine for 2–4 weeks. Because the BVD virus is shed in semen, breeding bulls should be tested for persistent infection. Artificial insemination should be done only with semen obtained from bulls free of persistent infection.
Infectious Bovine Rhinotracheitis (IBR) is a highly contagious, infectious disease that is caused by Bovine Herpesvirus-1 (BHV-1.) This virus can persist in animals for years and remain inactive until the animal is placed under stress. Bovine Herpesvirus-1 infections are widespread in the cattle population and are capable of attacking many different tissues in the animal leading to a variety of clinical disease types:
- Respiratory– infectious bovine rhinotracheitis (IBR) is the most common form found in feedlot cattle. The viral infection alone is not life-threatening but predisposes the animal to secondary bacterial pneumonia, which may result in death. Eye infections or conjunctivitis are also common with this type of infection.
- Reproductive– infectious pustular vulvovaginitis (IPV) in breeding cows causes genital lesions and abortions. Genital infections in bulls (infectious pustular balanoposthitis) can cause lesions or pustules on the penis. Transmission can occur in the absence of visible lesions and through artificial insemination with semen from infected bulls. Some cattle with BHV-1 infections show no signs, but they serve as a source of infection for other susceptible animals.
- Central Nervous System– when the virus infects the Central Nervous System it causes encephalomyelitis and generalized systemic infections. The virus is shed in secretions from the eye, nose, and reproductive organs.
The incubation period for the respiratory and reproductive form is generally 2–6 days. Signs include high fever, anorexia, coughing, excessive salivation, nasal discharge, conjunctivitis, and tearing. Abortions may occur with respiratory disease and may be seen up to 100 days after infection. Abortions generally occur during the second half of pregnancy, but early embryonic death is also possible.
In reproductive infections, the first signs are frequent urination, elevation of the tailhead, and a mild vaginal discharge. The vulva is swollen, then ulcers may be present on the surface. If secondary bacterial infections do not occur, animals can recover in 10–14 days. With bacterial infection, there may be inflammation of the uterus and infertility, with vaginal discharge for several weeks. In bulls, lesions occur on the penis and prepuce.
BHV-1 infection can be severe in young calves and cause a generalized disease. Eye and nasal discharges, respiratory distress, diarrhea, incoordination, and eventually convulsions and death may occur in a short period after generalized viral infection. Because of the large number of tissues the virus can affect, there is no definitive clinical diagnosis. Laboratory confirmation is necessary in order to identify infection by measuring antibodies in serum, plasma, or milk.
As with other viral diseases, there is no direct treatment for the infection. Antibiotic treatment of secondary bacterial infections may be necessary. Immunization generally provides adequate protection against clinical disease. Breeding and replacement heifers and bulls should be immunized when 6–8 months of age, before breeding, and yearly thereafter. Feeder calves should be immunized 2–3 weeks before entry into the feedlot. The best way to control IBR is to vaccinate before a disease outbreak occurs and quarantine all new arrivals and observe them for 30 days.
Rabies is an acute, progressive viral encephalomyelitis (swelling of the brain and brain tissues) that principally affects carnivores (meat eating mammals) and bats. The disease is fatal once signs appear. Rabies is found throughout the world, but a few countries claim to be free of the disease because of successful elimination programs or their island status. While it is not a common viral infection in cattle, they, like all mammals, are susceptible to this deadly disease, so it is imperative that cattle owners know the signs of the disease and how to protect their cattle against it.
Rabies is caused by lyssaviruses. In North America, the virus responsible for the spread of rabies occurs primarily in Red and Arctic foxes in Canada and Alaska; raccoons along the eastern seaboard from Maine to Florida; and gray foxes in the southwest, including Arizona, Colorado, and Texas. Most human cases of rabies in the USA in the past decade have been caused by bat rabies virus variants (yes, bats are mammals).
Transmission of the virus from carrier to host almost always occurs through saliva into tissues, usually by the bite of a rabid animal. Although much less likely, virus from saliva, salivary glands, or brain tissue can cause infection by entering the body through fresh wounds or mucous membranes.
The incubation period for the disease can be variable. Once infected, the virus travels through the peripheral nerves to the spinal cord and the brain. After reaching the brain, the virus travels to the salivary glands. Clinical signs of rabies are rarely definitive. Rabid animals of all species usually exhibit signs of Central Nervous System problems. The most reliable signs are rapid behavioral changes and unexplained progressive paralysis. Behavioral changes may include sudden anorexia, nervousness, irritability, and extreme excitability. Cattle with rabies can be dangerous, attacking and pursuing people and other animals. Lactation stops abruptly in dairy cattle. A common sign is a characteristic abnormal bellowing, which may continue intermittently until shortly before death. Suspect animals should be euthanized, and the head removed for laboratory analysis to confirm rabies.
Rabies vaccination is recommended for all mammals coming into contact with the public. Because of their curious nature, a cow may easily be bitten by a rabid animal wandering into the pasture. Vaccination frequency for most animals is every 3 years, after an initial series of two vaccines 1 year apart. A few vaccines are available for use in horses, cattle, and sheep. Rabies has the highest fatality rate of any infectious disease.
By Carol K. Ward, County 4-H Agent, Rutgers Cooperative Extension