February 2010 Articles

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Reproductive Diseases Can Cost You

Reproductive Diseases Can Cost You Dr. Jeremy Powell, Assistant Professor and Veterinarian Sometimes we don’t realize the danger that is lurking around the next corner. Just when you get through the breeding season & you’ve got all the cows settled, it hits. A major abortion storm sweeps through that wipes out next year’s calf crop, & you’re left with the questions: What could have caused this? How can you get a diagnosis? What can you do to prevent this from occurring next year? There are many potential causes that lead to abortion or embryonic death in cattle, but the majority of the problems are typically due to a handful of pathogens. Leptospirosis is a disease that can affect several species, including cattle, sheep, pigs, dogs, horses, wildlife & man. This disease is caused by bacteria that are well suited for wet, moist environments. Cattle can be exposed from consuming contaminated stock ponds or by wildlife, rodents or infected domestic animals. Transmission can occur when the bacteria penetrate a mucous membrane (mouth, nose, conjunctiva, genital tract) or enter an open wound. Once an animal is infected, the organism circulates throughout the body & localizes in the kidneys, mammary glands & genital tract. Once the urogenital tract becomes infected, the bacteria can be shed in urine, uterine discharge, semen & aborted fetuses/placentas. This shedding allows other herd mates to become exposed & infected. Abortions due to Leptospirosis typically occur in the second or third trimester of gestation. Cows do not abort the fetus when they first contract the disease, & infected cows frequently exhibit no other signs of illness. If cows are affected very late in gestation, they may give birth to weak or poorly developed calves. Infectious Bovine Rhinotracheitis can lead to several forms of clinical disease. The IBR virus can cause symptoms from respiratory tract infections, ocular infections, abortions, genital infections & neurological infections to a generalized infection of newborn calves. Abortion from IBR typically occurs from four months of gestation up to term. Cows aborting due to an IBR infection may experience temporary infertility from vaginitis after the abortion has occurred. Unvaccinated herds are at the highest risk for IBR abortion problems. Bovine Viral Diarrhea virus can cause a wide variety of clinical syndromes in cattle, including infertility, respiratory disease (pneumonia), congenital abnormalities (eye defects, brain defects), abortion & stillbirths in calves. If a pregnant cow acquires a BVD infection, there are several possible outcomes depending on the stage of pregnancy when she is infected. A normal calf could be born to a cow that becomes infected during late gestation (> 180 days). However, an infection during early pregnancy (< 125 days) can result in more detrimental outcomes. During this time period, possible outcomes of an infection include early embryonic death, abortion, fetal mummification or a persistently infected calf. Fetuses exposed to BVD that are at 150 days or more of gestation could be born with congenital defects. These defects may lead to poor brain development, eye abnormalities, structural malformations & stunted growth. Calves born with congenital defects usually have difficulty standing & walking and may exhibit an early death due to a poor ability to nurse the dam. Vibriosis is caused by bacteria called Campylobacter. It typically causes infertility during the breeding season due to loss of early pregnancies. Clinical signs of this disease would include a high percentage of cows in the herd returning to heat during the breeding season. They may also show prolonged or irregular estrus periods. Then, when calving season occurs, many cows will be calving later in the season due to the repeated breeding caused by infection. Infrequently, cows may abort between four & eight months of Campylobacter infection. Trichomoniasis is a venereal disease of cattle caused by a protozoa organism, Tritrichomonas foetus. This disease causes very few outward signs of illness. Therefore, it can often be present in a herd for a considerable time before it is suspected and diagnosed. Infected cows will experience infertility and early embryonic death, causing the cow to return to heat and subsequently extending the breeding season. This, in turn, causes devastating losses due to poor calf crops and prolonged calving seasons. Trichomoniasis has few adverse effects in the bull, but the bull acts as the main source of transmission for the herd. In bulls, the organism lives on the tissue lining of the penis and prepucial sheath. Younger bulls less than 4 years of age tend to clear themselves of the infection, while those 4 years and older are often infected for life. Other Reproductive Diseases There are many other potential causes of abortion in cattle other than the diseases covered in this article. One that is worth mentioning is Brucellosis, also known as Bang’s disease. For some time, the U.S. had been classified free of Brucellosis. However, in light of the recent outbreak in Montana, the importance of preventing this disease has been re-established. Producers should strongly consider a preventative vaccine for their replacement heifers. Replacement heifers must be vaccinated by a veterinarian or state technician for Brucellosis between 4 and 12 months of age. Diagnosing the Problem Diagnosing the cause of abortion is somewhat trying, and results can be inconclusive greater than 50 percent of the time. When submitting tissues to a diagnostic laboratory, careful handling of the sample submission is essential. Always refrigerate samples as soon as possible to prevent further breakdown of tissue. When submitting samples, you should include the fetus, the placenta and a maternal blood sample. Some diseases that cause abortion in cattle can also infect humans, so always be cautious when handling aborted fetuses and tissue. If you do not plan to use the tissues for diagnostic purposes, always remember to dispose of them so that other animals in the herd do not become exposed from these contaminants. Preventing the Problem Although herd health needs may vary between operations, there are a few standard vaccines that should be included to prevent problems with reproductive diseases in your herd. Among these are a 5-way viral vaccine (IBR, BVD, PI-3, BRSV), a 5-way Leptospirosis vaccine and a Vibriosis vaccine. Since vaccination needs may vary, it is important to get your veterinarian’s input when selecting vaccines for your operation. For more information on reproductive diseases and other cattle diseases, contact your county Extension office.