It’s a great day. The sun is shining, birds sing cheerfully, and you whistle in happy unison as you wander past your house’s little pond and tadpoles.
Hold on- your house doesn’t have a pond. Or tadpoles. You stop in your tracks and do a double take.
Upon closer inspection- the ‘pond’ is actually your dog’s water dish, glinting in the sunlight. As for those tadpoles?
Little. Black. Worms. Squiggling and squirming in the still, musty water. It’d be an evolutionary miracle if these ever turned into frogs at any point.
It gets you a bit panicky.
Why are there little black, squiggly worms in your dog’s water bowl? And will they be harmful to your pup if he lapped them up and swallowed them?
Turns out, those worms that you sometimes spot in stagnant bowls and buckets of water are the larvae of insects such as mosquitoes and flies.
Though they don’t look particularly benign in their wiggly, dark form, they are in reality harmless to any canine that might swallow them.
That doesn’t mean you should keep them there as companions for your pup though. While harmless in their current state, they will eventually grow up to become mosquitoes and flies in their adulthood.
Mosquitoes pose a health and disease risk to humans, and they can be even more dangerous for pets.
As you may already know, heartworms can be transmitted to dogs via mosquito bites. Heartworms will cause fatigue, lethargy, and heart damage to your best friend- which of course can be lethal.
That’s why it’s so important to replace your dog’s water dish with fresh, clean water frequently and to give it a good scrub and wash every few days. This will help to keep your dog’s drinking water safe, and the dog itself hydrated and healthy.
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Various different types of insects lay eggs in water, as it is an ideal environment for their larvae to grow and develop. Flies, mayflies and mosquitoes in particular prefer stagnant water to offload their young.
Fly and mosquito larvae look like small, hairy worms, with a noticeable head and a body segmented into ten parts. They live in the water for anywhere from four days to two weeks, feeding on any algae, fungi, plankton or other microorganisms.
While the larvae live and survive in water, they are unable to absorb oxygen from the water itself in the way that animals such as fish are able to.
That’s why you’ll often see them swimming around the surface of the body of water in an attempt to get rid of carbon dioxide, and to breathe in a fresh quantity of oxygen.
Flies and mosquitoes prefer to lay their eggs in still water for pure survivability reasons. After they become pregnant in their airborne phase, they return to bodies of water to lay their newly fertile eggs.
The eggs will be laid on the surface of the water where the water is more prone to movement and rising, which will flood the spawn and trigger them to hatch.
Though the larvae possess the ability to swim, they are not particularly strong swimmers and will not be able to fight against even a weak current. If a mosquito were to lay her eggs in a stream or river, the eggs and larvae would simply be washed downstream to their death.
That is why they explore and find the most ideal habitats to deploy their young, which invariably will involve still water.
Though they commonly infest environments like ponds and swamps, they are adaptable and will successfully deposit in buckets, basins, puddles and water bowls.
Different mosquito species have different tendencies as to where they like to reproduce. Some love transient waters such as ditches and forest pools, while others prefer salty swamps or small, stagnant pools.
If your dog’s water bowl has been sitting for a few days, unchanged and untouched, then it may start to grow algae or other microorganisms.
Combined with its still nature, it can prove to be the ideal location for a mosquito to place her eggs- hence the worms that gradually eventuate.
Most of the time, larvae and worms will develop due to the insects in your environment. Even the slightest bit of moisture, such as a pool of saliva, can be enough to draw in flies and mosquitoes.
However, it is also a rare possibility that the worms come directly from the main water supply, so if you have been diligently cleaning the bowl and exercising insect control, then it might be time to give your pipes a closer look.
Despite their slightly ominous appearance, mosquito larvae are completely harmless to a canine in their current form. They don’t sting or bite, and aren’t poisonous in any way. Their only defense is to squiggle around a bit, which in all fairness, is pretty useless.
If the larvae are swallowed by your dog while it drinks the water they reside in, they will simply be digested and dissolved by strong stomach acids- just like any other food that your pup might eat.
Dogs are omnivorous scavengers by nature and are tough, resilient creatures.
They frequently dine on things that they really shouldn’t, such as Thin Mints, petrolatum ointments, and orange chicken. While we fret over their wellbeing, they usually turn out ok- and none the wiser for it.
Unless your dog begins to show signs of stomach discomfort (which in the rare case that it occurs is more likely to have resulted from drinking stagnant water) such as diarrhea, vomiting, or a loss of appetite, you likely have nothing to worry about at all.
No. it isn’t possible for the larvae of mosquitoes to give your pup heartworms, even if it eats a large quantity of the wigglers.
The adult mosquito is the essential messenger when it comes to causing heartworm in dogs. Mosquitoes can carry infected heartworm larvae, which they then transfer to dogs when biting and feeding on them.
Heartworm larvae are deposited into the bloodstream, where they move to the dog’s heart and surrounding vessels and begin to mature.
The parasites cause blood supply to become impaired as they clog a dog’s heart and blood vessels. This results in symptoms such as fatigue, difficulty breathing, exercise intolerance, and abnormal heart sounds.
Heartworms are a major health risk when it comes to canines, and need to be treated swiftly with inpatient care and specialized medication.
The recovery process is also particularly arduous, as dogs need to be prevented from moving around too much during treatment in order to allow proper rest to take place.
That’s why it’s so important to replace the water in bowls, and to clean the bowls themselves as frequently as you can.
Though the larvae themselves are harmless, given the opportunity they will grow into adult mosquitoes capable of causing heartworms and other diseases.
Ensuring that there is no stagnant water around your dog and home will prevent the risk of mosquito-borne illnesses.
However, there is no way for mosquito larvae themselves to carry heartworm larvae since they haven’t yet had the opportunity to pick up the parasites. So, you can rest easy if your dog accidentally drank stale water that had tiny black worms swimming around in it!
There’s no denying that it’s good practice to leave water out for your pup, all throughout the day.
However, as a responsible dog owner, you also want to ensure that the water is clean- without any potentially harmful contaminants, pollutants, or organisms that could hurt your best friend.
The best way to keep bacteria, bugs, and mosquito/fly larvae out of a dog’s water bowl is to make it as uninviting of an environment for them as possible.
You can do this easily by cleaning the bowl daily. Just give it a good scrub, and then replenish the bowl with pristine, fresh, tap water. As long as you keep changing the water, any existing worms will simply get dumped out onto the ground or down the drain.
If it’s been a while since you last gave the bowl a thorough wash, you may want to use hot water or dish soap to tackle any grime, algae or residue that may have formed. Magic erasers are also very effective- just don’t leave it around afterwards for your dog to eat!
However, do be careful when using chemicals as there are many household cleaning substances like detergents and bleach that can be very harmful to canines if ingested. Make sure to rinse off extensively afterwards if you do use stronger chemical solutions.
Here are a few additional tips that will help to keep your dog’s water bowl clean:
- Treat the surrounding area of the water bowl with pet-friendly insecticides. You will be able to find these in most hardware stores.
- Use a fountain bowl like this one from Ownpets. Fountain bowls circulate the water and keep it moving, making it hard for mosquitoes and flies to lay their eggs on the surface.
- You can add one teaspoon of apple cider vinegar to your dog’s water to discourage mosquitoes from laying eggs in it. Mosquitoes are naturally deterred by the scent of the vinegar, and it will also kill any existing larvae as well.
- Mosquito dunks can be placed in water bowls to kill larvae. The active ingredient is Bacillus thuringiensis israelensis (or BTI for short), which is lethal to the larvae of mosquitoes but non-toxic to dogs and other animals.
If you regularly clean the bowl and follow the tips above, you should have no issues at all keeping the container free from mosquito and fly larvae.
However, if you do keep finding new worms in the water even after you wash the dish daily, collect a few of the specimens and take them to your vet for identification.
There may be other reasons why worms keep appearing in or around your dog’s water bowl. It could be that the dog has parasites inside its body that are making their way out- especially if they are white worms.
If this is the case, your dog will need to be dewormed with medications to ensure that it stays in optimal shape and health.
If you see tiny, black, squiggly worms swimming around in your dog’s water bowl, they are most likely the larvae of insects such as flies or mosquitoes. Though they don’t look particularly friendly, they also don’t pose any immediate danger to your pup.
However, this doesn’t mean that you should keep them around indefinitely. Eventually, they will grow up to be adult mosquitoes that are quite capable of transmitting diseases to both you and your pet.
Therefore, it is very important to rid your environment of them as much and as quickly as possible.
Since mosquitoes are fond of stagnant, stale water that is commonly found in bowls and buckets, the most effective way to prevent larvae-laden water is simply to change the water as frequently as you can!
It’s also a good idea to thoroughly clean the bowl from time to time, either with hot water or dishwashing liquid.
Rinse it out thoroughly, put in a teaspoon of apple cider vinegar, and more likely than not the mosquitoes will have the good sense to find someplace else to lay their eggs.
Heather Abraham is an owner of two dogs, one cat, a leopard gecko, and a parrot (who her dad still cannot teach bad words to), and an avid blogger. From the time she was a young girl, she always felt a connection with pets. She brings her love of every type of pet to you, with information on animal nutrition, medication, toys, beds, and everything else in between. Along with newly-on-board veterinarian DVM editor Elena, she puts pups first while offering other various fun tidbits along the way.