The Pennsylvania State University, University Park,
FAX (814) 863-6140
VETERINARY SCIENCE INFORMATION
(Circling Disease or Listerellosis)
Listeriosis is a bacterial infection usually of the brain.
Listeriosis is common in ruminants, pigs, dogs, and cats, some wild
animals, and humans. Animals infected with Listeria can show
clinical signs of abortions or nervous system disorders.
Listeria moncytogenes is the specific bacterium known to cause
listeriosis. This bacterium can live almost anywhere--in soil,
manure piles, and grass. Listeria thrives in aerobic conditions
where the pH is 5.4 or higher. It doesn't do well in very acid
conditions. Therefore, the top layers of silage or improperly
preserved silage may harbor large numbers of organisms. The
increased use of trench silos has been correlated with increased
numbers of listeriosis cases among cattle. Because of this, it is
important to make sure that silage is tightly packed to ensure
proper fermentation. Wet bales of hay may also harbor the
OCCURRENCE: Healthy animals are not usually affected by Listeria.
Cattle with lowered resistance to disease on a high silage diet are
prime candidates for listeriosis. Sheep and goats are even more
susceptible to this disease. Up to 30 percent of a sheep flock may
be affected in an outbreak.
CLINICAL SIGNS: The first signs of the disease in cattle are
fever, depression, and loss of appetite. Although not seen in every
case, the most notable symptom gives this disease its nickname,
"Circling Disease." Cattle with listeriosis are often seen walking
in circles. Other, more subtle symptoms include uncoordinated
movements, leaning against objects, and progressive paralysis.
Death can occur within 2 to 3 days after the onset of symptoms, but
cattle can survive for up to 2 weeks with the disease.
Although the dam may not show signs of listeriosis, she may
abort. Cattle are most likely to abort during the last 2 months of
their pregnancy. For sheep and goats, abortions often take place at
12 weeks or later. Retained placentas may follow abortions in sheep
TREATMENT: Recognition of symptoms is important for successful
treatment. Most animals will recover if treated with a broad
spectrum antibiotic started early. Diseased cattle should be
separated from healthy cattle and placed on a prolonged therapy
program In flocks of valuable sheep, it may be advantageous to
treat the whole flock. Vaccines are not available in the U.S.
PUBLIC HEALTH CONCERNS: Listeria monocytogenes may affect humans
as well as animals. It primarily affects people whose immune or
disease-fighting system is not working properly. Groups of people
especially susceptible are the very young (e.g. newborns) and the
very old, as well as pregnant women. In these people, Listeria may
cause infant deaths, meningitis or spontaneous abortions.
Many people may be exposed to Listeria, but do not become ill.
Some of these people have been found to shed the bacteria in their
Prior to the 1980s, listeriosis in humans was relatively rare.
It was not reportable to public health officials until 1986.
Several outbreaks in the 1980s created more interest in this
disease. Outbreaks have been associated with a number of different
food items, such as cole slaw, soft cheese, shellfish, and milk.
The bacterium has been also identified in a number of
ready-to-eat foods. However, these products have yet to be
associated with illness. The USDA checks meat and poultry products
for Listeria, and for public protection, the FDA will recall any
food products contaminated with Listeria
Most human cases of Listeria occur in urban areas where there
is little contact with farm animals. However, farm workers should
take precautions when handling aborted fetuses and animals sick
with listeriosis. People who work with food-producing animals can
be exposed to Listeria from aborted fetuses or diseased animals.
Milk should be pasteurized before consumption. Meat from animals
showing signs of disease should not be eaten.
Issued in furtherance of Cooperative Extension Work, Acts of
Congress May 8 and June 30, 1914, in cooperation with the U.S.
Department of Agriculture and the Pennsylvania Legislature. L.F.
Hood, Director of Cooperative Extension, The Pennsylvania State
The Pennsylvania State University is committed to the policy that
all persons shall have equal access to programs, facilities,
admission, and employment without regard to personal
characteristics not related to ability, performance, or
qualifications as determined by University policy or by state or
federal authorities. The Pennsylvania State University does not
discriminate against any person because of age, ancestry, color,
disability or handicap, national origin, race, religious creed,
sex, sexual orientation, or veteran status. Direct all affirmative
action inquiries to the Affirmative Action Office, The Pennsylvania
State University, 201 Willard Building, University Park, PA 16802-
%f DATE_INCLUDED;OCTOBER, 1993
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