story to find out more.
Postdoctoral scientist Monica Santin (left
foreground) and technicians Kristin Cameron and Robert Palmer prepare PCR
samples to detect Cryptosporidium as zoologist Ron Fayer examines
banding patterns in agarose gels for positive specimens. Click the image
for more information about it.
Learning More about Cryptosporidium in Cattle
May 10, 2005
Parasites previously thought to be
Cryptosporidium parvum in post-weaned calves are actually different
species altogether--species that infect cattle but not humans, according to
Agricultural Research Service (ARS)
Trout and visiting scientist
Santin of the
Microbial Safety Laboratory in Beltsville, Md., found several types of
Cryptosporidium in their studies, including C. parvum, C. andersoni
and two unnamed genotypes.
In the studies, the scientists collected data from 15 dairy farms in seven
states to determine the prevalence of Cryptosporidium species in
pre-weaned and post-weaned calves. Fecal samples were analyzed to detect the
The prevalence of these Cryptosporidium species and genotypes
appeared to be age-related between pre-weaned and post-weaned calves. C.
parvum, the only Cryptosporidium species infectious to humans, made
up 85 percent of the Cryptosporidium infections in pre-weaned calves,
but only 1 percent of infections in post-weaned calves. It was formerly thought
that C. parvum was present in all calves.
According to Fayer, these findings demonstrate that earlier reports on the
presence and prevalence of C. parvum in post-weaned cattle, based solely
on Cryptosporidium oocyst morphology, must be reassessed using molecular
methods to validate species and genotype. Oocysts are the egglike, infectious
form of the parasite.
Testing for Cryptosporidium is normally based on finding the parasite
in fecal matter. These tests, however, prove the presence of
Cryptosporidium but don't distinguish between different species.
more about the research in the May 2005 issue of Agricultural
ARS is the U.S. Department of
Agriculture's chief in-house scientific research agency.