DOVER — They can’t afford to vaccinate or don’t think it matters.

Either way horse owners may suffer a precious loss of life or hefty veterinarian’s bill if ignoring the threat of West Nile Virus.

That’s according to the Office of the State Veterinarian, which on Tuesday announced Delaware’s fourth and fifth horses recently with WNV, both in Kent County.

A one-year-old Standardbred mare was euthanized on Oct. 15 due to WNV infection, and a 6-year-old Belgian mare was diagnosed, threated and recovering as of Oct. 18, the State Veterinarian said.

Neither had received a vaccination shot, which is typically administered in the neck area and protects the animal for at least a year.

In 2017, just two WNV cases in Delaware horses were confirmed.

State Veterinarian Dr. Heather Hirst suspects there may have been more cases this year that either weren’t reported or not recognized by their owners.

“There may be more brewing but we don’t get all those cases reported” she said. “Sometimes horses get sick and die without a veterinarian being involved.”

A wet spring brought an unprecedented number of mosquitoes to the area, and their bites caused WNV.

In the deadly case, “The horse received veterinary care for loss of control of limbs and buckling over in the front limbs which began on Oct. 11. Clinical signs progressed to inability to rise, muscle twitching, and stupor.”

Dr. Hirst described vaccination as “a very significant insurance if you consider the cost that comes if a veterinarian comes out to investigate and perhaps treat.

“We stress to owners the value of doing the right thing to save their animals’ lives and avoid a big vet bill.”

Even with vaccination, animals may still contract WNV. The clinical signs won’t be as severe, though, less treatment will be required and the chance of survival is greatly heightened, Dr. Hirst said.

The fatality rate in WNV-infected horses is roughly 30 percent and there’s no prescribed drug treatment once contracted.

WNV doesn’t not transfer from horse to horse or human. So far this year, eight cases have been detected in humans.

Every time a WNV case is confirmed, the State Veterinarian sends a group email to Delaware’s horse owners and veterinarians as a reminder.

“This is very significant to the Department of Agriculture, since one of our responsibilities is protecting the health of the state’s animal population,” Dr. Hirst said.

Mosquito bites can also trigger Eastern Equine Encephalitis, which is fatal in 70 to 90 percent of horse-involved cases. EEE vaccinations are also available.

A DOA news release said “Delaware’s Department of Natural Resources and Environmental Control’s Mosquito Control Section has seen an increase of WNV found in wild birds and sentinel chickens this year throughout the state.

“There have been a total of eight EEE-positive sentinel chickens and WNV has been detected in 66 sentinel chickens and 37 wild birds.”

Who to contact

• To report suspected cases of human West Nile Virus, call the DPH Office of Infectious Disease Epidemiology at 888-295-5196.

• Animal health questions should be directed to the Delaware Department of Agriculture at 800-282-8685 (Delaware only) or 698-4500. Ask for the Poultry and Animal Health Section.

• Questions about the state’s mosquito control program or mosquito biology should be directed to the Mosquito Control Section at 739-9917.

Staff writer Craig Anderson can be reached at 741-8296 or cande