John Beck: Mosquitoes can be harmful to your pets

May 26, 2010 at 12:26 a.m.

Q: After the recent downpours, the mosquitoes are out in full force. Are these bugs just a pest to my pets or are they actually doing harm? Do I need to do anything extra to protect my pets?

A: The mosquitoes seemed to show up overnight. Not only did they come out in force, they seem to be about the size of Dallas. Those biting bugs are bothering everyone right now. Besides making us very itchy and full of red bumps, these flying pests also carry disease.

Not only can they communicate illness in us, but they can also do so in pets. The most prevalent problem that we experience is the spread of heartworms. Heartworms are different from the normal worms you think of when someone says their dog has worms. That general term encompasses only intestinal worms like hookworms, roundworms, whipworms and tapeworms. These intestinal parasites set up shop in the intestines and cause problems like diarrhea, vomiting, etc.

Heartworms are a whole separate set of circumstances. These worms circulate in the infected animal's blood stream in the immature stage where they can be sucked up by feeding mosquitoes. Once the mosquito has sucked up infected blood, it can bite a new host and transfer the immature worms into the new host's bloodstream. This is where the once monthly heartworm preventative comes into play. If a dog or cat is on preventative and is bitten by an infected mosquito, the preventative will kill the immature stage of the heartworm. If the pet is not on a preventative when it is bitten by an infected mosquito, the immature worms will begin to mature into adults. During the maturation phase, the worms stop circulating in the blood stream and make the heart their new home. Once in the heart, they can cause muscle atrophy and the heart valves to work insufficiently. These adult/mature worms are then able to mate and make more immature heartworms to circulate in the bloodstream. A mosquito comes along and the cycle continues.

Keeping your pet on heartworm preventative is a must in south Texas. Even if your pet never, ever goes outside, they should still be on a preventative. One thing this huge mass of mosquitoes has shown us is that they can make their way inside our cars, homes and businesses without any problem.

There are also a couple of flea preventatives on the market that can help repel and kill mosquitoes. Like most flea preventatives, this product is applied topically, between the shoulder blades once monthly. It will repel fleas and mosquitoes for a full month. These products will help with the annoying biting that your pet endures every time a mosquito lands on it. Spraying your yard and house will also help cut down on the number of mosquitoes in the environment. Clearing extra brush and standing water will also help lower your infestation.

If you have any other questions or concerns, feel free to contact me or you local veterinarian.

Dr. John Beck has a veterinary practice at Hillcrest Animal Hospital in Victoria. Submit questions to Dr. Beck at



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