Key Instruction Points
Treat all research animals as if they
may have zoonotic disease
Practice good personal hygiene for
prevention of disease
Work restrictions may be appropriate
for immunocompromized persons – physician review is advised
A veterinary college obtained seven Holstein calves
from two local dairies for a student laboratory. Thirty-five students worked with the
calves in a lab session before the instructor learned that all of the animals were
infected with Cryptosporidium. Subsequently, 8 of the students developed gastrointestinal
illness. Cryptosporidium oocysts were found in fecal samples of half of the students
tested. The affected students experienced fever, headache, nausea, diarrhea and
vomiting. Most of the students recovered quickly with no treatment although one had severe
diarrhea for two weeks and another required hospitalization for severe dehydration.
Cryptosporidium is a zoonotic, protozoan parasite
which is similar to coccidia. It is almost ubiquitous in young ruminants (e.g.
calves, kids, lambs). In people with a normal immune system it generally causes short-term
diarrhea. In people with immunocompromised immune systems (e.g. from AIDS or cancer
chemotherapy), it causes a prolonged, life- threatening disease. In 1993, when it
contaminated the Milwaukee, Wisconsin water supply it caused widespread disease.
There is no effective treatment known.
Practice good personal hygiene when working with
young animals, especially calves. Cryptosporidium persists in the environment and can be
spread by contaminated clothing. Infants and immunocompromised adults should not handle
animals who have diarrhea. It is strongly recommended that immunocompromised
persons should not work with calves, lambs, kids or deer fawns.
Key Instruction Points
- Treat all animals as if they may have zoonotic
disease
- Consider periodic testing of animal colonies,
regardless of source
In 1989, a 23 year old employee at a research institution was
hospitalized for viral meningitis. Her symptoms included fever, abdominal pain,
myalgia, malaise, fatigue, severe headaches, chest pain, difficult breathing, coughing,
vomiting, and hair loss. Her illness lasted 8 weeks and was determined to be caused
by viral meningitis (inflammation of the lining of the brain and spinal cord) caused by
lymphocytic choriomeningitis virus (LCM).
The patient worked at a research laboratory that develops drugs and
diagnostic tests using animals. Part of this effort involved use of a tumor
cell line that could not be maintained in tissue culture.The tumor cells had been
maintained for 20 years by injection into the cheek pouches of hamsters. (hamster
cheek pouches are immunologically protected. Tumors will grow there without
rejection.) For the past few years the tumor had been injected into "nude" mice.
(Nude mice, like AIDS patients, are deficient in T lymphocytes. They do not reject
transplanted tissues, even from other species.) A follow-up investigation revealed
that the tumor line had been infected with LCM virus since 1975. Almost 20% of the cell
lines maintained by the company were infected. Apparently, the switch to using nude mice
had increased the employee exposure. Employees who worked with nude mice were
tested; 26% had evidence of infection with LCM. Several other workers had recovered from
illnesses that were likely due to LCM. Changing bedding, changing water
bottles, and cleaning cages were the activities most associated with infection.
LCM is one of the few zoonotic diseases of concern in modern
rodent research facilities. Iit has been eliminated from commercial rodent breeding
colonies although it is found in wild mice. LCM can be introduced into research
facilities by wild mice, or by the introduction of infected tissues. Standard steps used
in well run programs reduce the risk of LCM. These include exclusion of wild
rodents, careful evaluation of animals and animal tissues from other than commercial
breeders, and implmenting testing programs within the facility.
Q Fever in
Medical School Personnel (top)
Key Instruction Points
- Special training and precautions are needed for
persons working with sheep
- Separate animal use areas from "people
areas"
- Work restrictions may be appropriate for
immunocompromized persons – physician review is advised
In 1980, an unusual illness was recognized among faculty, laboratory
personnel and staff of a medical school. The illness was characterized by high fever
(up to 105 degrees F), shaking chills and absence of respiratory signs. The disease was
determined to be Q fever which is caused by the organism Coxiella burnetii. The source of
the infection was found to be pregnant sheep which were being used for research. During
a six month period, clinical infections were confirmed in 65 people. Blood tests
revealed that a total of 137 people had been exposed. Of these, only 41 worked
directly with the sheep. The remainder of exposed people worked in areas where the sheep
had passed by or were exposed in other ways. As a result of this outbreak, all sheep
research was moved to a research farm.
Q-Fever is a rickettsial disease found in ruminants such as cattle,
sheep and goats (Rocky Mountain Spotted Fever is another rickettsial disease). Q-Fever is
so common in ruminants that it is difficult to find herds free of it. In cow's milk,
pasteurization kills the organism. While giving birth, infected animals shed high
numbers of organisms into the placenta and fetal fluids.
In a production-type sheep facility, with movement of animals in and
out of the flock, it is not practical to eliminate Q-fever from the flock.
The acute illness in people is treatable with
antibiotics,however it often goes unrecognized. Chronic, long-term complications include
infection of heart valves. People with pre-existing heart conditions are at increased risk
of chronic infection.
Sheep are a popular animal model for research in obstetrics.
For this reason they have been associated with outbreaks of human disease in medical
school settings. Infection control necessitates separating animal use areas
from "people" areas.
Personnel who work with sheep must receive instructions on
procedures to follow when working with them. Housing and research arrangements must
provide good separation from non-animal work. Personnel who who might be at risk of
chronic Q-fever complications must be alerted. Immunocomptormised persons or
those who have a history of heart disease (e.g. rheumatic fever, heart surgery) should
consult a physician about the advisability of working with sheep and other ruminants.
Key Instruction Points
- Physician review is advised prior to work with
animals, particularly for people with impaired defense mechanisms
A 26 year old woman underwent a spenectomy (spleen removal).
Two years later, while working as a dog groomer at a veterinary hospital she was bitten by
a dog. The wound was washed with surgical iodine solution and bandaged. Three days later,
the woman left work because had pain at the site of the bite and felt ill. Within 12 hours
she had two grand mal seizures and collapsed She was hospitalized and treated for
septicemia (blood infection) and kidney failure. She eventually recovered without
complications.
This patient became infected with a bacterium formerly called
"DF2", which is now classified as Capnocytophaga canimorsus. This bacterium is
commonly found in the mouths of normal dogs. It is probably a common contaminant of
dog bite wounds. Most people do not experience problems. However, the organism can cause a
serious, potentially fatal systemic infection in immunocompromised people.
Alcoholism and absence of a spleen have been associated with many cases. Even intensive
antibiotic therapy may not be able to control the infection in such cases. The rapid onset
of symptoms seen in this case is typical. Physicians should consider hospitalization for
observation of splenectomy patients following a dog bite. Persons who have had their
spleen removed should discuss the advisability of working with dogs or cats, with
their physician in any setting.
Revision Date: 12/16/2004
url: http://www2.umdnj.edu/eohssweb/aiha/accidents/animals.htm
