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Veterinarians Can and Should Aid Physicians with Difficult Diagnoses

October 26, 2009

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The saying, "When you hear hoofbeats, think horses, not zebras," is a reminder to physicians that common symptoms usually mean common disease rather than an exotic diagnosis. 

Sometimes when you hear hoofbeats, you should think zebras. So says Carol Glaser, DVM/MPVM (UC Davis, 1985), MD, of the California Department of Health.

Glaser spoke to a group of roughly 75 veterinary students and faculty of the school October 26 to remind them why "joining forces" in a One Health approach is more important than ever. Her presentation provided  ample evidence of the contributions of veterinary expertise when diagnosing unusual illnesses.   


Glaser's career encompasses training and experience in veterinary medicine, human medicine and public health, with a stop at UC San Francisco for clinical training in pediatrics and infectious diseases of children. This combination of training and experience, including an internship in parasitology with the Centers for Disease Control and Prevention, led to positions with California's Department of Public Health. She now leads the department's Encephalitis and Special Investigations Section of the Division of Communicable Disease Control. She is also a faculty member at the UC San Francisco School of Medicine and is pursuing her interests in translational research in the area of zoonotic diseases.


Glaser receives a variety of calls from public health officers and physicians to help them identify or rule out infectious diseases caused by animals. She probes the patient's history--digging deeper into the details of animal exposures may make the difference between full recovery from rat bite fever and a potentially fatal disease. Glaser outlined several clinical "case vignettes" to illustrate why One Health initiatives of the veterinary and medical professions are more important than ever--and why clinicians should be alert to the possibility of unusual infections that can be transmitted from animals to humans even when symptoms indicate more common problems. She also raised awareness in her audience about the need for more sensitive diagnostic tests for so-called orphan diseases that may otherwise go unrecognized until patients are very ill.


A diagnosis of rat bite fever in a child showed the need to probe for detailed information about pets in the home--including a pet rat that a family failed to note in a patient's history. This case also highlighted the fact that many cases go unreported because early antibiotic treatment may knock out the infection before it has been identified. A special blood test was required to diagnose and treat the illness in a patient allergic to penicillin.

While the first case example began with no known animal exposure, Glaser's next example involved so many animals that doctors were at first unable to pin down which exposure could have been responsible for the patient's illness. Rabies was suspected due to the patient's exposure to many animals, including family pets and wildlife. In this case of encephalopathy, Glaser  turned up a diagnosis of bartonellosis, or cat-scratch fever, in a rural teenager. While most cases involving Bartonella are self-limiting, several atypical forms exist, and specialized testing was required to pin it down in this patient.

Other cases on which Glaser has been consulted involve concerns about rabies, a major concern of public health officials, but in two more instances the culprit was a different problem.

"I'm always seeing zebras," Glaser stated several times during the lecture, referring to the quote above. She described a hunch that she followed after consulting on an atypical case of hydrocephaly in a prematurely born infant. Glaser also placed a spotlight on the need for more complete diagnostic tests as some tests are just not sensitive enough to identify a pathogen at certain stages of infection or with some atypical disease symptoms. She ordered a TORCH screen, a test that identifies several types of infection in infants, and then followed up with a specialized test that detected toxoplasmosis in a sick infant. The child's twin, who had shown no symptoms at the time, also turned out to be positive for toxoplasmosis, likely contracted while their mother was pregnant. Toxoplasmosis treatment in that case took about one year to complete.

One case of a woman with cirrhosis of the liver who had died in the hospital pointed out the need to expand understanding of "immune-compromised" to include people with diabetes, liver disease or kidney ailments as well cancer or HIV. The woman had also presented some symptoms of rabies, including severe anxiety, so the team followed up. A patient history that included a feral cat bite and further testing revealed pasteurella as the cause of infection. Often a localized soft-tissue infection, the pasteurella in this immune-compromised patient had turned deadly. "One Health is more important than ever, given the increased spectrum of immune-compromised hosts," she said.

Another patient involved different symptoms and treatments over the course of some weeks as the medical team tried to narrow down the diagnosis. Glaser suspected a tick-borne disease, and an atttending physician suggested tularemia. Though tests for both erlichiosis and tularemia initially showed negative results, as the child got better, a new PCR test detected the pathogen for tularemia. Teamwork and the right test method led to the correct diagnosis and successful treatment.


To strengthen the One Health links between physicians and veterinarians, Glaser suggested that veterinarians, who possess more complete training and more updated animal disease information than physicians, engage in their clients' family discussions of disease risks from pets and other animal exposures.

Glaser said that even an informal conversation between a veterinarian and a physician would provide guidance to families. She challenged veterinarians to volunteer to call the family doctor when concerns arise about zoonoses because physicians sometimes simply do not have time to ask their patients about their pets and the risks they may pose.

Physicians and veterinarians alike need to keep an open mind about the possibility of a rarer illness in their patients, Glaser concluded. "Zoonoses, though infrequent, are not always easy to recognize and can be devastating."  

For more information about One Health issues, please attend the 2009-2010 School of Veterinary Medicine One Health Lecture Series. This series of free talks features faculty and guest speakers covering a broad range of the intertwined issues of animal, human and environmental health and is sponsored by the Calvin Schwabe One Health Project.