The Rural Voice, 1993-02, Page 16Diagnostics
Diseases humans cart catch from animals
by Dr. Gaylan Josephson
Veterinary Laboratory Services
Iluron Park
Last month we introduced the top-
ic of zoonotic diseases. This month
we would like to elaborate on a speci-
fic zoonotic disease, commenting on
both the disease in animals and its ef-
fect in humans and illustrating it with
a case that the diagnostic laboratory
was involved with.
The disease is Q fever,
and it is caused by a
parasite, Coxiella burnetti,
that must live within a cell
to exist. It was first
diagnosed in humans in
Australia in 1937, and was
called Q fever, the Q
standing for "query",
because the investigators
had so many unanswered
questions about the disease.
The organism causes abortion in
sheep and goats, as well as the birth
of full-term, weak Iambs and kids.
Other animals that are naturally
infected include cattle, swine, cats
and rodents but the disease is not as
severe in these species. Although
abortion rates in goat and sheep
flocks arc usually low (the number of
animals aborting is small), abortion
storms can occur in previously
uninfected flocks, resulting in heavy
losses. On examination, significant
findings arc not found in aborted
fetuses. However, lesions in the
placenta (afterbirth) arc pronounced
and consist of a thickened, leathery
placenta with a copious amount of
creamy exudate (discharge) on the
surface between the cotyledons.
Large numbers of the organism are
present in this discharge and in other
body discharges such as milk and
urine. These discharges can i.ifect
other animals in the flock, or even
humans who are exposed.
Coxiella burnetti organisms arc
very hardy, surviving for long
periods of time in the environment.
They are also very infectious, with a
single inhaled organism capable of
causing disease. Potential sources of
infection include contaminated wool,
zoo animals, farm pets, soiled
laundry, livestock trucks, livestock at
fairs and inhalation of contaminated
airborne dust particles from an
infected premise.
Clinical signs in humans are often
vague and suggest a flu-like condi-
tion. Most people complain of a
sudden onset of a fever, vomiting
and/or diarrhoea, headaches and a
non-productive cough — symptoms
that are really not too diagnostic. As
well, the liver is often
enlarged and the person
may be jaundiced.
The incubation period
depends on the infective
dose but is usually two to
three weeks. Deaths rarely
occur in humans, but
occasionally are seen
following localization of
the organism in the heart or
heart valves. The acute
disease usually lasts for only one to
two weeks, but the symptoms may
persist for a much longer time. Since
signs of infection may be mild and
the symptoms so vague, diagnosis is
difficult. Determining the presence
of antibodies in the blood of suspect
individuals is by far the most accurate
method.
In the winter/spring of 1991-92, an
outbreak of Q fever occurred in per-
sons who had visited an agricultural
fair and had been exposed (either at
that time or later) to goats who had
delivered stillborn or premature kids.
The infection occurred through the
inhalation of organisms that had been
aerosolized.
Threc goat herds were prdsent at
the fair and two of these herds were
implicated in the outbreak. Blood
samples were taken from animals in
all three herds, and results suggest
that a majority of the animals tested
had recent or past exposure to
Coxiella burnetti. Of the six persons
diagnosed as having Q fever, one had
been exposed to goats which were
kidding during the fair. The other
five persons were exposed to the two
infected goat herds after they had
returned home. In both cases, the
female goats gave birth to dead or
weakened kids. In addition to these
documented cases, further cases of Q
fever no doubt occurred in other
Stri
sanit
tation
prog
esse
ram
ntial
12 THE RURAL VOICE
persons and in goat herds, that could
subsequently be linked to the fair.
This case history demonstrates the
ease in which a person can become
infected with Coxiella burnetti from
infected animals, and serves as a
good example of a zoonotic condi-
tion. Only the strictest sanitation
program and reducing exposure of
persons to the infected animals could
have helped eliminate the human
disease.0
Ref. An outbreak of Q fever in the
Niagara Region. Gallant M et al.
Public Health Epidemiology Report
Ontario, Ministry of Health. Vol 3,
No 19, Nov 6, 1992.
We have tried to keep our topics timely
and informative. However, we would
welcome any suggestions from readers
for future topics. We would also invite
interested persons to tour the facilities
at the Diagnostics Laboratory at
Huron Park. We would ask that you
make prior arrangements by phoning
228-6691, Ext. 276.
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