During the hot summer months, both large and small animals can suffer unwanted attention from fleas, ticks, biting flies and mosquitoes. Besides the annoyance, pain and itching they cause, they can also transmit disease to your animal. There are many things you can do to help avoid this. 
The flies that cause problems with animals are not the typical house flies, but species such as black flies, deer flies, and horse flies. In many cases, the flies (and mosquitoes, too) prefer to “strike” the sensitive and fairly thin skin of the animal’s ears. This has led to the common term “fly strike” as a means of describing the problem. Fly strike is uncomfortable for the animal and can be seen as seen as crusty and/or oozing lesions along the ear flaps: as the ears are continually wounded, more flies are attracted and bite. 
Be particularly careful with older, long-haired pets who may not be very active when outside. Areas of the body prone to moisture and soiling — especially the rear end — attracts flies that can lay their eggs in that area and soon we have another problem: fly larvae (maggots). If you notice this problem, bring your pet to your veterinarian as soon as possible to avoid serious systemic illness.
In horses, biting flies can cause decreased performance and certain mosquitoes can transmit disease such as West Nile Virus (WNV) and Eastern/Western Equine Encephalitis Viruses (EEE/WEE). Also, they are annoying and painful to your horse, just as they are to you. Help reduce the mosquito population by removing standing water (where mosquitoes breed) and completely empty the stock tank periodically to rid it of any mosquito larvae. Another idea is to add fish that eat mosquito larvae to water sources.  Keep horses stalled during peak mosquito feeding times of dusk and dawn and use horse-approved insect repellents on them. 
Many horse owners will attach insect-proof face masks to their horses to help prevent clusters of flies gathering around their eyes. Since wild birds are the source of WNV infection to mosquitoes, discourage them from roosting in the horse barn/stables. It is important to also talk with your veterinarian about vaccination for the viral diseases and safe products for your horses. 
In dogs and cats mosquitoes can transmit potentially fatal heartworm disease. In addition, cats in particular can be extremely sensitive to mosquito bites around their ears and face, leading to scabs, swelling and itching. To help prevent fly strike and mosquito bites, try not to leave your pets outside all day long during hot summer days.  Eliminate standing water to help reduce the mosquito population. 
While there are many products available to repel flies and mosquitoes, it is extremely important that you talk to your veterinarian before applying an over-the-counter insect repellent: many of them contain ingredients that are toxic to dogs and cats. In addition, don’t assume that if the product is OK to use on dogs that you can use it on cats. There are many over-the-counter and dog-only products that can kill your cat. A monthly heartworm preventative (either a topical or a pill) can help prevent heartworm disease in your dog and cat, and some topical products now repel mosquitoes.  
By now, most pet owners know that fleas and ticks are everywhere. They are not just itchy and annoying to your pets: they can transmit life-threatening diseases to dogs and cats. There are collars, topicals and even pills you can use to prevent them. Talk to your veterinarian, who knows your pet, about which is best for it.
All of our livestock and companion animals are prone to attack by fleas, ticks, mosquitos and biting flies. For prevention, keep animals in at pests’ peak feeding times, do what you can to help eliminate standing water and talk to your veterinarian about preventatives and repellents for your animals’ protection. And remember, never use a product meant for one species (including humans) on another without first discussing it with your veterinarian. For more information on biting insects and disease in our animals, visit vtvets.org/.