Cryptosporidium in Veterinary Students
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.
Herpes B Virus From A Rhesus Macaque
Fatal Cercopithecine herpesvirus 1 (B Virus) Infection Following a Mucocutaneous Exposure and Interim Recommendations for Worker Protection, MMWR Weekly, December 18, 1998 / 47(49);1073-6,1083
Viral Meningitis in a Researcher
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. It 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 implementing testing programs within the facility.
Q Fever in a Medical School Personnel
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 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.
Septicemia Following a Dog Bite
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.