For the most part, it seems harmless if a dog or cat eats a bug. However, there are a few dangers lurking when it comes to dogs and cats eating bugs. It's definitely a behavior you should try to deter your pets from doing.
Stings and Bites
Many bugs such as bees, wasps, and hornets can and will sting a dog or cat. If your pet is trying to catch a stinging bug, it's likely they will be stung. Most bee stings in dogs and cats occur on the face, or even worse, in the mouth.
This is dangerous because some pets can be severely allergic to bee stings and can go into anaphylactic shock. This is a medical emergency and veterinary care should be administered immediately. For information on what to do if your dog is stung by a bee, check out this post.
There are also biting bugs, like spiders, that pose a threat to dogs and cats. The two most dangerous venomous spiders that come to mind are black widows and the brown recluse. Both of these spiders have a harmful and potentially fatal bite. Fortunately, they are usually hidden well and may not be easy for pets to spot. Spider bites also need medical attention from a veterinarian.
Bugs That Are Toxic
Some types of bugs are toxic when ingested and can cause stomach upset. Most toxic bugs cause GI inflammation or possibly oral lesions. The types of toxic bugs you should watch out for include caterpillars, ladybugs, and stinkbugs. Generally speaking, the more colorful a bug is the more likely it is to be toxic.
Many caterpillars are brightly colored to warn predators that they don't taste good. Of course, our dogs and cats may not have gotten that memo.
As if eating bugs wasn't gross enough already, your dog and cat can become infected with parasites from eating bugs. Two of the more common parasites that I've personally seen dogs and cats infected with are Tapeworm and Physaloptera.
Tapeworm is a very common parasite for dogs and cats. Luckily, it's not too serious or life-threatening. Dogs and cats become infected with tapeworm by ingesting a flea that is carrying the parasite. That's one reason why it's important to use flea prevention on your pets.
Tapeworms are large enough that you can visibly see their segments in your pets' stool or around their anus. They look like white grains of rice. Treatment is easy and there are over-the-counter options available for getting rid of tapeworms.
A less common parasite is Physaloptera, also known as a "stomach worm infection". Dogs and cats can both become infected with Physaloptera from eating cockraoches, grubs, beetles, crickets, or other bugs who eat feces.
Physaloptera can infect your dog or cat with just one worm or multiple worms that live in your pets' stomach. Your pet may not exhibit any signs, but the most common symptom is chronic or acute vomiting.
In one particular case of Physaloptera that I can remember, a patient was sent to a specialist for chronic vomiting. After an endoscopic exploration of the dog's stomach (a gastroscopy), a single Physaloptera worm was discovered.
Harmful insecticides are often used to kill bugs. There's no telling which bugs may have toxic insecticides on them, and which ones don't. That's why it's best to NOT let your dog or cat eat bugs. You don't want them getting sick from eating bug poison. If you have a dog or cat that likes to bugs in your home, you should probably refrain from using poisonous insecticides and try a more natural bug-killing approach.
If you have a cat who is indoors only, they may be at less risk of ingesting a bug who's been sprayed with an insecticide. Still, there is some risk since bugs come from outside most of the time.
Does your pet like to eat bugs? Stay safe and keep your dogs and cats away from bugs!