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worms in dogs water bowl

Why Are There Worms in My Dog’s Water Bowl?

Finding worms anywhere can be alarming and gross, but especially so when they turn up in your dog’s water bowl. Here’s what kind of worms they likely are and what to do about them.

Have you ever left your dog’s water out for a few days without changing it, then found it to suddenly be mysteriously teeming with life? In the same way that it would be distressing to see little worms wriggling around your own cup of water, worms in your dog’s water bowl can be a nauseating, unwelcome find. 

Thankfully, in many cases these worms do not pose a great health risk to your pup. Sometimes, these worms may simply serve as an indicator that your dog’s water bowl needs to be cleaned more often or moved to a different location. That said, if you notice your dog acting strangely after drinking from a worm-ridden water bowl, it may be a good idea to check in with the veterinarian. 

So, why are there worms in my dog’s water bowl?

Although there is a chance that the worms found in your dog’s water bowl came from your dog, it is much more likely that the pests are there as a result of the water in the bowl being unchanged or from the bowl itself being dirty.

Standing water is an enticing environment for certain insects looking for places to lay eggs, as well as a breeding ground for bacteria, algae, and other unwanted critters and substances. For this reason, it is important to regularly clean your dog’s water bowl and provide fresh water. 

Black Worms in Dog’s Water Bowl

Mosquitoes may be the culprit if you’ve found black worms in your dog’s water bowl: In their larval stage, mosquitos live in water and look like stringy black or dark brown worms. It is worth noting, though, that they appear darker when present in a lighter-colored dish—such as a white plastic or stainless-steel bowl—than when seen in a darker-colored dish, which can make them appear gray or taupe. 

When these larvae become pupae, they take on a more curled-up form. In both stages, though, these developing mosquitoes are fairly small and may look like dark, stringy worms in the water. 

Larval mosquitoes do not drink blood to live; as such, they do not pose the same sort of risk to humans and pets as adult mosquitoes. If your dog drank water infested with mosquito larvae, the bacteria in the standing water containing the mosquito larvae would pose a greater risk to the dog’s health than the bugs. 

On the other hand, adult mosquitoes can pose a huge risk to the health of both dogs and humans, including through the transmission of heartworm. To become a carrier of heartworm, an adult mosquito needs to consume a heartworm-infected animal’s blood. The infected mosquito may then pass the heartworm to the next animal it bites. 

Adult mosquitoes are most likely to be found in locations that were hospitable to their early development. Thus, it is not a good idea to allow developing mosquitoes to proliferate in your dog’s water bowl. 

black worms in dogs water bowl
Mosquito larvae

White Worms in Dog’s Water Bowl

Another worm that might be found in a dog’s water bowl—though less common than mosquito larvae—is the horsehair worm, also called the Gordian worm. These worms are parasitic, feeding on arthropods such as crustaceans, cockroaches, and grasshoppers. 

Horsehair worms mate in water, and their offspring are eaten by arthropods. Once eaten, the larvae sustain themselves by eating the host from the inside. When the worm has matured and is near a water source, it leaves the host. 

If you find a horsehair worm in your dog’s bowl, it is likely that its host insect is also in or near the bowl. These worms may be white, but they may also be brown or black; if they are long and stringy and a dead insect is nearby, it is likely that the worm is a horsehair worm.

There have been some cases of horsehair worms being expelled from human beings, cats, and dogs. However, the worms were not acting as parasites of these mammals—instead, it was likely that the hosts the worms were feeding on were eaten, then the worms tried to escape their hosts.

In those cases, the worms were vomited or expelled via feces. If your dog happened to eat a horsehair worm found in its water bowl, this would be the likely result. However, if you knew your dog ate a horsehair worm and it did not reappear quickly, you might want to have your dog checked by their vet. 

Other Water Hazards

In addition to mosquito larvae and horsehair worms, other critters and insects could end up in your dog’s water bowl. The likelihood of that occurring would depend on where the bowl was placed, how long the water had been left in the bowl, and whether there had been rain or another weather event that affected the water.

There are many bugs your dog could eat that would not cause them any serious harm. However, if you notice that your dog ate a bug and is subsequently experiencing signs of poisoning, vomiting, or diarrhea, it may be a good idea to take them to the vet or contact a poison helpline, such as the ASPCA Animal Poison Control Center

An additional hazard dogs may encounter in dirty water bowls is harmful bacteria. While these would not necessarily be as obvious as worms writhing around in a bowl, they can pose even more of a health hazard to dogs. 

Some bacteria that could be found in a dog’s water bowl include E. coli, Giardia, Leptospira, Coccidia, and Legionella. If your dog drinks water that contains these harmful bacteria, they may experience symptoms such as weight loss, vomiting, diarrhea, or shortness of breath. 

As in the scenario of a dog experiencing negative side effects after eating an insect, you should have your dog checked by a vet if they begin to exhibit alarming symptoms after drinking stagnant water. 

Algae and fungi also have the potential to build up in a dog’s water bowl. These are more likely to grow in a bowl that has not been cleaned for a while and has stagnant water, though it is also possible that these could begin to grow in a dirty bowl filled with fresh water. 

While most of the hazards listed have been most likely to appear in an outdoor environment, an unchanged indoor water dish can also become a breeding ground for bacteria, as well as a trap for dust and hair, neither of which are great for your dog to consume. If you would not want it in your glass of water, make sure your dog does not have to deal with it in their bowl. 

How to Prevent Worms and Other Health Hazards in a Dog’s Water Bowl

Regularly cleaning and refreshing the water in your dog’s water bowl is the best way to keep your pup safe from bacteria, insects, and harmful algae and fungi. If you have not cleaned your dog’s water bowl for a while, you might need to perform a deep clean in order to scrub off old saliva and bacteria.

If you have a dishwashing machine and your dog’s bowl is dishwasher-safe, you might consider running it through the dishwasher. If your machine has a sanitize function, it should be safe to include the bowl with your “human” dishes; however, it is also fine to run a “pet-stuff only” load. 

If you do not have a dishwasher or if you want to avoid using it for your dog’s dishes, you could clean out the bowl by hand with a sponge and a mild dishwashing detergent; just be careful to only use the sponge for pet bowls, and make sure to disinfect the sink after you clean the bowl.

If you already regularly clean your dog’s water bowl and provide fresh water daily and still find worms and other nuisances in the bowl, you may want to consider moving the bowl to a different location. For instance, if the bowl is placed near grass outside, it may need to be moved further away from vegetation to decrease the likelihood of insects also using it as a water source. 

Final Thoughts

Although finding worms in your dog’s water bowl can be a gross experience, these do not generally pose a great health risk to your pup. However, if you find worms or other unwanted substances in your dog’s water bowl, you might want to consider treating it as a sign that a bowl cleaning is overdue. If your dog has an alarming reaction to drinking dirty water, take them to the vet. 

Frequently Asked Questions

Q: Is There a Type of Water Bowl That Can Prevent Worms and Other Hazards?

A: While worms are more of an environmental hazard than a hazard brought about by a water bowl’s material, bacteria may be more likely to be harbored in water bowls made of certain materials. 

Although plastic bowls are often dishwasher-safe and come in decorative, fun colors, they also can more easily become cracked, leading to a higher likelihood of bacteria appearing. Some dogs may also have skin sensitivities to plastic. 

Like plastic bowls, ceramic bowls and dishes can be very pretty and may also be dishwasher-safe. However, these dishes are more breakable than plastic dishes. They may also develop imperceptible cracks that can cause bacteria build up, making them less ideal, especially in outdoor environments. 

As far as dog bowls go, stainless steel bowls may not be the most aesthetically pleasing—even so, they are less likely to harbor bacteria than the other types of bowls. Care should be taken to regularly clean them, though, so that they do not develop rust or staining.

So, while some bowls may be better bacteria deterrents than others, the best thing a dog owner can do to address their dog’s hydration needs is to regularly provide fresh drinking water in a clean bowl. 

Chelsea Dickan

Chelsea Dickan

Chelsea Dickan is a long-time advocate for animals, especially those that bark or meow. When she isn't writing, she enjoys reading and watching scary movies in which the dog doesn't die.