West Nile Virus in Dogs

West Nile virus is a highly infectious disease transmitted primarily by mosquitoes that feed on infected birds. West Nile virus is closely related to the Zika virus and the virus that causes yellow fever. This virus was first discovered in 1937 but didn't make its way to the US until the late 1990s. West Nile virus gets its name from the region in Uganda where scientists first found it.

Many species of birds and mammals — including humans, cats, horses, and, of course, dogs — are susceptible to this virus. However, experts do not believe that dogs (or any other mammal) have the ability to spread West Nile virus to others.

While most cases of West Nile virus in canines are mild, the disease does have the potential to cause life-threatening swelling of the brain. Dogs suspected of having West Nile virus should be seen by a vet immediately.

Some dogs are asymptomatic carriers of West Nile virus, but others may display a range of symptoms. Here's what to look for in symptomatic cases of West Nile virus in dogs:

• Lethargy
• Lack of appetite
• Problems with mobility
  
• Pronounced weakness
• Convulsions
• Muscle spasms
• Fever
• Staggering
• Blindness
• Excessive salivation
• Stomach upset
• Head tilt
  
• Abnormal or irregular heartbeat
• Immune-mediated thrombocytopenia
• Anemia

There are two main ways dogs can contract West Nile virus. As mentioned above, bites from an infected mosquito are the primary way this virus spreads to canines. Eating an infected bird may also cause dogs to contract the virus, although experts note this mode of transmission has yet to be confirmed.

Dogs who live in areas with large mosquito populations are at higher risk for this disease, not just due to mosquito bites but also from contact with infected birds. Experts say birds are the disease's natural host, and the virus can quickly pass through bird populations via mosquito bites in infested areas. 

When dogs come into the clinic exhibiting signs of West Nile virus, vets will often perform a battery of tests to rule out other neurological conditions. There are several antibody tests for West Nile virus in canines, though vets might not order them right away since infection is still uncommon in America.

To test for West Nile Virus antibodies, the vet will take a sample of the dog’s plasma or serum and perform one of the following tests:

• Plaque-reduction neutralization assay
• Microplate serum (virus) neutralization assay
• IgM or IgG ELISA test

Vets will also ask the pet parent a series of questions about what transpired in the days leading up to their symptoms. The vet may ask if the dog spends a lot of time outdoors or has recently eaten any wildlife. These questions can help the vet determine the mode of transmission.

Since West Nile virus is a virus, there is little vets can do for it aside from letting it run its course. If the dog's symptoms are relatively mild, the vet may instruct the parents to monitor the dog at home and bring them back in if their symptoms worsen. Depending on the severity of the dog's infection, it may take several weeks to a few months for symptoms to resolve.

Otherwise healthy pets usually recover on their own, but dogs with more severe cases may need fluid therapy and medication to minimize side effects. Examples of supportive medications include:

• Anti-epileptic drugs (to control seizures)
• Steroids (to manage thrombocytopenia)
• Antibiotics (to prevent secondary infections)
• Anti-diarrheal medications and stomach protectants (to combat gastrointestinal symptoms) 
• IV fluids (to prevent dehydration)

Because the symptoms of West Nile virus differ from dog to dog, the exact combination of drugs vets use can vary considerably. Depending on their symptoms, dogs may need to continue supportive medications for a few days to a few weeks.

During the recovery period, dogs need quality nutrition and plenty of water to keep their strength up and prevent dehydration. Vets may recommend that pet parents put their dogs on crate rest, especially if West Nile virus affects their coordination.

Dogs recuperating from West Nile virus should regularly visit the vet for blood tests and thorough check-ups to ensure they don't develop anemia or immune-mediated thrombocytopenia.

Complete recovery from West Nile virus is common, though it can take up to a year for dogs to feel like themselves again. Experts say animals who recover are unlikely to catch the virus again due to acquired immunity. Sadly, when West Nile virus crosses the blood-brain barrier, the neurological effects can prove fatal for some dogs. 

West Nile virus can be expensive to treat. If you suspect your dog is at risk of developing the West Nile virus, start searching for pet insurance today. Wag!'s pet insurance comparison tool lets pet parents compare insurance plans from leading companies like PetPlan and Embrace. Find the "pawfect" plan for your pet in just a few clicks!