The Many Faces Of BVD
Arlen Mills
Capital Region
Extension Veterinarian
LEBANON (Lebanon County) Bovine Virus Di
arrhea is a serious cattle disease, causing estimated
losses of up to $l5O million annually nationwide.
As the name tells us, the agent causing this disease is
a virus which has the ability to change as often as the
weather. The disease syndromes that we see today
with BVD are much more varied than the diarrhea,
now called “mucosal disease,” that was first recog
nized years ago. In addition, the virus can affect many
body systems in the infected cow or calf.
Most primary infections of cattle with the BVD
virus are mild, with perhaps a mild diarrhea, fever,
and inflammation of the eyes and nose. These animals
usually recover in four or five days and the symptoms
may not even be observed.
However, the BVD virus can cause a suppression of
the immune system, which may increase the severity
of diseases caused by other infections.
This immune suppression is a very significant
aspect of BVD infection, allowing other infections to
flourish.
Probably the most significant losses from BVD in
fections are due to infection of susceptible pregnant fe-
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males. The virus readily crosses the placenta into the
calf. While the cow’s immune system may rapidly
clear the infection from her own tissues, the fetus re
mains infected.
One of several sequelae may then develop. The fetus
may die resulting in resorption or abortion. Some of
these may remain in the uterus as a “mummy.”
A fetus which is infected before 125-150 days of ges
tation which does survive will be born infected if the
infection is with a type of BVD virus called “noncyto
pathic.”
This is the “persistently infected” or PI animal that
remains infected for life and continually sheds virus.
These animals are a real source of loss and frustra
tion to producers and veterinarians as they are con
stantly exposing the herd to the BVD virus-these
animals maintain the virus in our cattle population.
Some of these are poor-doing animals but just as
many will appear normal. Until recently with the
advent of some new testing methods, it was difficult to
identify these PI animals. We will discuss testing in
more detail later in this article.
A fetus infected 125-150 days after conception is ca
pable of mounting an immune response to the virus in
fection. However, BVD virus infection of developing
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