Clinical Pathology Resident Discovers New Virus in a Frog

While researching a rice field for her Ph.D. in her home state of Rio Grande do Sul in Brazil, Dr. Lina Crespo Bilhalva (she/her) caught and released a frog whose blood sample would contain a virus never before identified.

Now a clinical pathology resident in the Department of Comparative Pathobiology at Cummings School of Veterinary Medicine at Tufts University, Dr. Crespo submitted her findings as a poster presentation for the upcoming ACVP/ASVCP (American College of Veterinary Pathologists/American Society for Veterinary Clinical Pathology) Annual Meeting. The organizing committee accepted her poster and invited her to deliver an oral presentation of her work.

Her Ph.D. project built upon her research as a master’s degree student studying butter (or Creole) frogs (Leptodactylus luctator), a species endemic to South America. Dr. Crespo earned her D.V.M., M.S., and Ph.D. at the Federal University of Rio Grande do Sul in Brazil, and completed a portion of her Ph.D. research at Purdue University College of Veterinary Medicine.

While not endangered, the butter species of frog is one of three families of amphibians undergoing the fastest population decline, according to Dr. Crespo. “My project was to assess the health of animals living in a rice field with pesticides and another without. The presence of pesticides was the only difference between the sites. I collected blood and skin swabs from the frogs for blood analysis and parasite testing and then released them back into the wild.”

She collected samples over a year, and after finishing her fieldwork, she spent another two years completing her Ph.D. project.

In the blood sample of one of the frogs she tested, she found abnormalities in the red blood cells that she thought looked like viral inclusions. The frog was also anemic, an indication that the abnormality was making the frog sick. She conducted a molecular analysis at Purdue University.

“According to the sequencing results, we discovered that this virus is different from anything published in the literature,” says Dr. Crespo. “We still have to do the phylogenetic tree, but all indications are that it is similar to an iridovirus, in a category we call ‘erythrocytic virus.’ The changes in the blood count suggest that the frog is being adversely affected by something, possibly this virus.”

While still learning about this new virus, Dr. Crespo explains that if it behaves like similar viruses, it should only affect frogs, but that’s still unknown. Though many viruses in living organisms often don’t cause disease, the finding warrants further investigation.

“In this case, we are concerned that the virus has pathogenic potential based on the abnormalities we found in the infected animal's blood counts,” she says. “This case is interesting because we are discovering pathogens that can hurt wildlife, and some of them can even cause mass mortalities, such as the Ranavirus and the chytrid fungus. So, discovering a new virus could help to develop more effective conservation measures. Nothing prevents this virus from being transmitted to other species.”

This past summer, Dr. Crespo began her clinical pathology residency at Cummings School. She evaluates routine laboratory samples for pathology review and teaches fourth-year veterinary students during their clinical rotations. One of Dr. Crespo’s mentors in the program is Dr. Francisco Conrado, assistant professor in the Department of Comparative Pathobiology. He collaborated closely with Dr. Crespo on writing the manuscript and its submission to the ACVP/ASVCP conference.

On the significance of Dr. Crespo’s findings, he comments, “No one knows! And that's the beauty of it. While its impact is currently unknown, this discovery helps establish baseline health data for wild populations and allows us to investigate its potential to cause disease. This type of exploratory research is crucial for understanding amphibian health, population dynamics, and the broader ecosystem.”

Dr. Crespo will present her work, “A Novel Erythrocytic Iridovirus in a Butter Frog,” at the ACVP/ASVCP Annual Meeting next month in Seattle. The largest veterinary pathology conference in the country, the ACVP/ASVCP Annual Meeting brings together 20,000 veterinary clinical pathologists and biomedical professionals for workshops and presentations on topics ranging from liquid biopsy to forensic pathology to the latest research on emerging infectious disease, as well as mystery slide sessions on gastrointestinal pathology and neuropathology. Dr. Crespo will additionally present a mystery slide case on a dog from South America with a strain of microfilariae that was incredibly challenging to diagnose.

“We were thrilled to learn that Lina's research was accepted for an oral presentation rather than a poster!” says Dr. Conrado. “This exciting opportunity allows her to engage with a larger audience, answer questions directly, and share her new discovery more broadly. As a first-year resident, this platform is invaluable for developing her public speaking skills and establishing her presence in the field.”

The clinical pathology residency program restarted just last year. Another resident in the program, Dr. Rachel Whitman will also deliver a mystery slide case and present her research orally at the ACVP/ASVCP Annual Meeting next month.

“It's really exciting to have our clinical pathology residency program fully running again! This is the first time we've had traditional residents in my five years here, and I'm extremely proud of them. Both Lina and Rachel will be presenting at the Annual Meeting. Their success is a real testament to our residents and the strength of our program,” says Dr. Conrado.

Dr. Crespo is currently conducting the phylogenetic analysis of the virus and writing up her research paper.

“It's not unexpected to find new infectious agents in wildlife, especially with the new technologies available in molecular analysis,” says Dr. Crespo. “In order to carry out efficient conservation measures in the native fauna, we need to know the diseases that can affect these animals, how they spread, and what they mean for their health.”