West Nile Virus is an infection carried by mosquitoes. This year has seen worst outbreaks in over a decade affecting parts of the US.
Dogs can be infected by West Nile Virus but these infections are rare. Also the infected animals usually have milder symptoms then humans – the typical presentation is lethargy and weakness which generally passes within a few days. There is no vaccine for dogs or cats.
The best form of prevention is reducing the incidence of mosquito bites. This applies to humans as well as animals and is of relevance to other mosquito-borne diseases. So if you are not from the US but live in the area where other mosquito-born diseases are present (heart worm, dengue fever, etc.) read on:
Stay inside early morning and late afternoon if possible – these are the times when mosquitoes are most active.
Secure windows and doors with good mosquito nets. In malaria-prone areas this has been proven to be the most effective anti-mosquito strategy.
Remove all bodies of stale water. This step is very important. Mosquitoes need stagnant water to breed. This could mean a pool as small as a puddle. Drain all pools of water and upturn any water retaining vessels. If the pool can not be drained – a small amount of kerosene can provide a protective film to prevent mosquitoes breeding (be careful with this step – respect local laws of your area).
Use suitable mosquito repellents. You can get pet-approved repellents. They do work and provide an insurance policy if other steps fail. But read the label carefully (some of those are registered for dogs but very toxic for cats!) and don’t rely on repellents alone – they are not fail proof. Make sure you implement the other steps too.