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Parasites Is Key to Risk Assessment
By Rosalie Bliss
May 10, 2002
The single-celled parasite Toxoplasma
gondii and its cousin, Neospora caninum, are responsible for
abortion and other health problems in livestock. Millions of infectious-stage
oocysts are excreted in the feces of infected animals on or near farmland. When
the hardy oocysts come into contact with farm feed, livestock can get infected.
The oocyst stages of the two protozoans are virtually indistinguishable. And
until recently, researchers didnt have the sensitive tests necessary to
diagnose or distinguish N. caninum infections from those caused by T.
Agricultural Research Service
scientists in the Parasite Biology,
Epidemiology and Systematics Laboratory in Beltsville, Md., have been
involved in developing both serological and genetic tests to help distinguish a
host of insidious look-alike parasites. The ability to make such distinctions
will help researchers define the distribution of single-celled parasites in
domestic and wild animals, as well as in people.
Cats are the reservoir of infection for T. gondii. Dogs are the
reservoir of infection for N. caninum. Infected dogs and cats excrete
the environmentally resistant oocysts in their feces.
ARS scientists are working to discern how many cyst-forming parasitic
species exist, how they are related to one another, and how to tell them apart.
To do that, they look at variations in genes by genotyping strains of parasites
taken from all classes of food animals. The research will lead to a better
understanding of the epidemiology of such parasites, which form cysts in the
muscles of domesticated animals, wildlife and primates. These include parasites
belonging to the genera Neospora, Hammondia, Besnoittia
Read more about defining risk from meatborne parasites in the
issue of Agricultural Research magazine.
ARS is the chief scientific research agency in the
U.S. Department of Agriculture.