Livestock Management RANCHING
B
BVD Causes Multiple Losses to the Cow Herd There are often no physical signs of infection ex-
OVINE VIRAL DIARRHEA (BVD) IS AN IMPORTANT DISEASE for all cattle producers to manage.
BVD was fi rst described in 1946 as a severe and often
fatal disease in dairy cattle. Early researchers named this disorder ‘mucosal disease’, and many people still call the severe digestive form of BVD by this name. We know this disease can affect other organs,
as well as • Cause problems in the digestive tract • Be implicated as a respiratory agent • Cause birth defects • Reduce immuno-suppressive function — weak- ening the animal’s immune system and lessen- ing its ability to fi ght other infectious diseases
• Affect all ages of cattle • Be found in every segment of beef production BVD is easily transmitted among animals via nasal
contact with cow udders or drinkers. Unlike infectious bovine rhinotracheitis (IBR) — which can be spread by nasal contact through drinkers throughout the entire herd in a matter of 3 to 4 days — BVD spreads much more slowly over many weeks, wandering through the herd.
70 The Cattleman October 2014
cept for those of other invading agents causing watery eyes, nasal discharge, anorexia, fever and sometimes dehydration with depression. Diarrhea and ulcers of nasal and oral mucosa are other symptoms sometimes accompanying the sickness. The major health risk to the animal from BVD is the secondary opportunist infections occurring because of the suppressed or non- functional immune system. On the ranch, animals that are persistently in-
fected with BVD are feared. These are known as BVD-PI cattle. An animal becomes persistently infected with BVD if • It is from a dam that is persistently infected • If it is from a dam exposed to BVD from day 45 to day 125 of the pregnancy
A cow or heifer exposed to BVD during this critical
period becomes viremic. The BVD virus circulates in her blood, allowing the virus to fl ow through the fetal calf’s blood. Since the calf’s immune system is in its development stage from day 45 to day 125 of gestation, the calf’s immune system will recognize this virus as a part of itself; not as foreign.
thecattlemanmagazine.com
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