During the recent Global BVDZero Web Congress, Auburn University veterinarian Dan Givens outlined the variety of reproductive pathogens cow-calf producers face, along with bovine viral diarrhea virus (BVDV). The event, hosted by Boehringer Ingelheim, involved more than 300 veterinarians from 10 countries gathered at various locations. The U.S. assembly took place in Dallas just prior to the Academy of Veterinary Consultants Spring Conference.
The global event featured presentations from three prominent experts in Bovine Viral Diarrhea (BVD). These were:
· Dr. Julia Ridpath, recently retired after studying BVDV and related pestiviruses at the USDA’s National Animal Disease Center (NADC) in Ames, Iowa.
· Dr. George Caldow, Veterinary Manager, SAC Consulting Veterinary Services, a division of Scotland’s Rural College.
· Dr. Dan Givens, Professor and Associate Dean for Academic Affairs, Auburn University College of Veterinary Medicine.
This installment summarizes Dr. Givens’ presentation, titled “The impact and control of bovine reproductive pathogens.”
Givens described how reproductive diseases often can affect herds and damage profitability, sometimes without ranchers recognizing they have a problem. Unless they see late-term abortions, declines in calving rates often remain undiagnosed. Even when a cow aborts a fetus and the rancher collects samples the causative agent is identified less than half of the time. Early embryonic losses or fetal deaths are more common, and while a wide variety of infectious and non-infectious factors can cause these losses, reproductive pathogens often play a role. Some are zoonotic, Givens says, and most can be controlled through diagnosis, biosecurity, vaccination and treatments. Givens focused on eight reproductive pathogens.
Campylobacter fetus subspecies venerealis, or vibriosis: This is a bacterial disease with venereal transmission. It leads to infertility, embryonic and early fetal loss. Vaccines are available and effective in most cases, and the disease has been eradicated in some areas.
Histophilus somni: These Gram-negative, rod-shaped bacteria often occur as part of the normal flora in the cattle biome. In large concentrations, the bacterial can be pathogenic, and while it most often is associated with respiratory disease in feedyard cattle, it also can be associated with infertility in beef cows.
Brucella abortus: This Gram-negative intracellular bacteria causes brucellosis in cattle and also is zoonotic, with the human form often referred to as undulant fever. In cattle, brucellosis typically causes abortions during the second trimester of gestation. The national eradication program has mostly eliminated the disease from U.S. herds, although wildlife populations, such as bison in the Yellowstone region, can serve as reservoirs for the pathogen and pass it back to cattle herds.
Lepospirosis: Leptospirosis in cattle is generally caused by one of two types of the Leptospira hardjo bacteria -- Leptospira hardjo-bovis or Leptospira hardjo-prajitno. These bacteria infect the kidney and genital tract of cattle and are associated with abortions at all stages of gestation including early embryonic death. More than half of the abortions associated with leptospirosis occur during the third trimester. Vaccines are available and can be effective, but cross-protection against different Leptospira serovars appears to be limited.
Neospora caninum: This is a coccidian parasite transmitted through oral ingestion of oocysts shed in canine feces. The parasite can pass from the dam to the fetus, and causes significant incidence of abortions in cattle in some regions. Without effective vaccines, the best control strategy is to minimize exposure of cattle, feedstuffs and water to domestic or wild canines.
Tritrichomonas foetus: This pear-shaped flagellate protozoan causes trichomoniasis, a venereal disease of cattle characterized by early fetal death and infertility, resulting in open cows and extended calving intervals. Control strategies should include biosecurity, testing, culling and vaccination. Testing focuses on bulls, and as there is no cure, infected bulls must be culled. Givens says trichomoniasis vaccination is not intended to control the pathogen, but to improve reproductive rates and reduce the economic impact of the pathogen in infected herds.
Bovine herpesvirus 1: This viral pathogen is associated with infectious bovine rhinotracheitis (IBR) in cattle. It is transmitted through nasal and oral fluids and semen, and has a wide range of presentations including respiratory and reproductive disease. Latent infections occur with recrudescence when animals become stressed. Eradication is possible, Givens says, and vaccination plays a key role. Modified-live vaccines (MLV) can provide a faster response and longer duration, and can be safely administered to pregnant cows if the cows were previously vaccinated prior to breeding. Killed vaccines are safe to use in pregnant cows regardless of previous vaccination history.
Bovine viral diarrhea virus: BVDV causes some late-term abortions, but embryonic loss and low fertility are more economically significant impacts in cow-calf operations. Effective control strategies include biosecurity, diagnosis (especially detection of persistently infected (PI) cattle) and vaccination.
For more on the biology of BVDV and control strategies, read Part 1 of this series, which summarizes Dr. Ridpath’s presentation.
Also read Part 2, which focuses on Dr Caldow’s presentation titled “Herd level diagnostic approaches for BVDV.”
The archived presentations now are available for on-demand viewing on the BVDZero website. Once on the site, click on “Register Here” for a quick registration that will provide access to the presentations.