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Research Program
With the discovery of the intestinal parasite, Cryptosporidium parvum
in diarrheic calves, lambs and veterinary students, in the late 70’s
my research program in cryptosporidial disease was launched. The
decade of the 80’s was dedicated to research on characterization,
diagnosis, treatment and prevention of the disease. The biggest
contributions came in educating human and veterinary medical
diagnosticians in the diagnostic methods, and in putting the disease
in perspective. The photograph below depicts a simple diagnostic tool,
the acid-fast stain of a fecal smear with the very red,
cryptosporidial oocysts. Below that is a collection of oocysts
isolated using the fecal flotation tool; we were first to demonstrate
these oocysts using this common laboratory tool.
Acid fast stained fecal smear showing 6 micron diameter Crypto
oocysts.
Spherical oocysts of Cryptosporidium parvum, fecal flotation in
sugar solution.
In terms of
perspective, we were able to show that almost every calf in the world
contracted the cryptosporidial infection in the second week of life,
but that for a calf that was otherwise healthy, well-fed and
unstressed, the disease was no more than a minor inconvenience. In
many presentations and publications, I’ve helped to put into
perspective the significance of cryptosporidiosis on human and animal
health.
In the mid-80’s,
I discovered a cause of subpar performance in feeder cattle,
Cryptosporidium muris infection of the stomach lining of cattle,
often a life-long infection. My subsequent national survey showed that
C. muris, of cattle, now renamed Cryptosporidium andersoni,
was ubiquitous among beef and dairy cattle populations.
Histologic section of cow stomach with the many little dots
Cryptosporidium andersoni. In three glands. Acid production (and
thus protein digestion) is retarded.
The practical
significance of the parasitism of adult dairy cows was illuminated
when we showed the affected cows were producing 13% less milk than the
normal cows in a commercial dairy herd. Up to 30% of the replacement
heifers were parasitized transiently at any one time and we
hypothesize that during this time their performance, in terms of
weight gains, is subpar.
A mini-project
on Johne’s Disease of cattle, just completed, showed that among
slaughtered, non-fed beef (cull cows) at the local Armour plant, 4% of
beef and 8% of dairy cows had the chronic, debilitating, intestinal
infection by Mycobacterium paratuberculosis (Johne’s Disease).
Our laboratory was officially certified as capable of doing the
difficult culture work on this organism, through this project.
Current research
is aimed at searching for additional causes of calf diarrhea and
death. The program focuses on placing sentinel bull calves in
calf-rearing situations where there is a consistent incidence of calf
diarrhea among the replacement heifers. Once the bull calves have been
sufficiently exposed, they are brought to the Caine Center for
intensive study. Colleagues at the Washington Animal Diseases
Diagnostic Laboratories and at the Ohio State University are assisting
in the search for new agents in disease outbreaks where known agents
are absent or otherwise do not account for the entirety of the disease
manifestation. These colleagues are using new research tools to look
for various viruses and protozoan organisms.
Practical
“research” at the Caine Center consists of investigations of disease
outbreaks in the livestock community and the development of new tools
and methods to aid those investigations. For example students are
taught to efficiently perform necropsies in order to make diagnoses
post mortem. Developed at Caine, quick brain removal (in as little as
3 minutes) from a cow results in quality brain specimens for any
diagnostic need.With this innovative, practical approach, a quick
cross cut of the skull reveals the brain.
Brain parts
suitable for any diagnostic analytical procedure are quickly "spooned"
out and evaluated in a variety of ways to arrive at a diagnosis.
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