The equine vaccine for West Nile virus is not foolproof.

An infected Cass County horse that was euthanized at the end of July appeared to have been adequately vaccinated, state veterinarian Dr. Larry Schuler said Wednesday.

Vaccines are never considered 100 percent effective, he said.

“You do have some vaccine breaks.”

The virus is spread to humans and horses via mosquitoes. There is no vaccine for humans and the inoculation for horses has yet to be fully approved by the USDA.

Regardless of not having full USDA certification, the vaccine has proven itself effective and worthy of full approval, said John Tuttle, manager of professional services for the vaccine’s manufacturing company, Ft. Dodge Animal Health of Overland Park, Kan.

It was released last year under emergency conditions, he said. There was only a 2 percent rate of failure last year, he said.

The Cass County horse had received both shots required for full protection. However, the horse was infected before the vaccine had time to take full effect, said David Calderwood, veterinarian at Casselton Veterinary Service.

It takes four weeks after the second shot to become fully protected, he said. After the first rounds of inoculations, immunity increases and only one shot per year is required, he said.

Even though horses are still at risk immediately after the first series of shots, horse owners should not hesitate to get their horses vaccinated now, he said.

“Horse owners have to know the disease is here to stay,” he said.

“It’s too much of risk not to get vaccinated.”

The vaccine should be fully approved by the USDA by the end of the summer, Tuttle said.

Meanwhile, horses in North Dakota are being infected at a faster rate than those in surrounding states such as Minnesota and South Dakota, Schuler said. While the official count of infected horses in North Dakota remains at 15, the North Dakota State University Diagnostic Lab will release the results of 48 tests today.

“There’s getting to be quite a few” cases, Schuler said. There are a large number of samples coming in not only from the eastern parts of the state but from all over. “We will probably see an escalation until we get a frost to reduce the mosquito count.”

Minnesota counties are also seeing more cases, most from the eastern part of the state, said Mike Schommer, spokesman for the Minnesota Board of Animal Health.

Ten horses in Minnesota have been infected with the virus, two from Clay County, Schommer said. Twenty-two Minnesota birds have been confirmed as being infected, he said.

After the two birds in Fargo were confirmed as being infected Tuesday, Fargo Cass Public Health was inundated with phone calls from citizens, half reporting dead birds and half with West Nile virus questions, said Brady Scribner, environmental health practitioner with Fargo Cass Public Health.

Fargo Cass Public Health has sent 37 birds to be tested at a lab in Wisconsin, including 12 Wednesday, Scribner said. It takes two to three weeks to get results back, he said. Public Health is still collecting birds that have died within 48 hours of being found, Scribner said.

Readers can reach Forum reporter Lisa Schneider at (701) 241-5529