Abigail Klein Leichman
January 2, 2013, Updated November 3, 2016

Dr. Shimon Harrus did not intend to find the world’s first vaccine against canine monocytic ehrlichiosis (CMT), a sometimes fatal tick-borne disease in dogs. Instead, he was attempting to determine how long ticks must be attached to a dog’s fur in order to transmit CMT.

“I was using bacteria I cultured in my lab, and all of a sudden I realized the two dogs in our experiment did not become sick, and the ticks I put on the dogs did not become infected,” Harrus tells ISRAEL21c. “Then we performed a big study and we realized something important was going on.”

The remarkable results of the experiments done by Harrus and his lab partner, Dr. Gad Baneth, over the past four or five years are outlined in a December 17, 2012 article in the journal Vaccine.

Harrus is dean of the Hebrew University of Jerusalem’s Koret School of Veterinary Medicine in Rehovot. Baneth is a professor of veterinary medicine at the school.

Harrus explains that CME is prevalent worldwide, and currently cannot be prevented aside from tick control. If dogs become infected, they must undergo a lengthy course of antibiotic treatment.

“The vaccine developed by Profs. Harrus and Baneth is the first vaccine to prove effective against this disease,” said Yaacov Michlin, CEO of Yissum, the university’s technology transfer company.

“The current lack of vaccine for CME, the growing awareness of the market and the growing market needs make this invention particularly attractive, and Yissum is currently looking for commercial partners for further development and commercialization purposes.”

The most common infectious disease in dogs

A bite from a brown dog tick passes Ehrlichia bacteria into the dog’s bloodstream. The disease may be acute or chronic. In the acute stage, several weeks after infection and lasting for up to a month, the dog will have fever and lowered peripheral blood-cell counts. Some dogs progress to the chronic phase, which can lead to low blood-cell counts, bone marrow suppression and bleeding, often resulting in death.

The potential vaccine was developed from Harrus and Baneth’s proprietary attenuated strain of Ehrlichia canis. They and their doctoral students assessed the formula on 12 dogs divided into three groups. Four dogs were inoculated (vaccinated) with the attenuated Ehrlichia strain twice, four dogs only once and the last group of four dogs served as the control group.

The vaccinated dogs showed no clinical signs of disease after the inoculation, suggesting that the novel vaccine is safe and does not induce adverse effects. When the dogs were later infected with a virulent Ehrlichia field strain, the control dogs all developed a severe disease, whereas only three of the eight vaccinated dogs presented mild transient fever and the rest remained healthy.

Harrus says funding is needed for continued research before the vaccine can be commercialized.

“We need to make sure it works against other strains, we need to learn the mechanism by comparing the attenuated strain against wild strains, and we have many other research questions.”

Now in his sixth year as head of the veterinary school, Harrus says his research is so important to him that he gave up most of his clinical work at the vet school’s affiliated animal hospital in order to remain active in the lab. His areas of interest are infectious and vector-borne diseases; how fleas and rodents carry and transmit disease to animals; and the Bartonella bacteria that cause diseases such as cat-scratch fever.

CME is one of the most common infectious diseases in canines, affecting not only pets but also foxes, wolves, jackals and other wild dogs. Canine vaccines are the fastest growing segment within the global veterinary vaccine market, which in 2011 grossed $4.23 billion. That number is expected to climb to $5.6 billion by 2015.


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