How to Treat Camallanus worm in Guppies?

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Guppies may experience a variety of disorders, sicknesses, and parasites during their lifetime. Identifying the nature of the condition will allow you to address it adequately before advancing too much.

Today we will discuss the Camallanus worm. What is this parasite, how will it affect guppies, and how can you counter it?

What is the Camallanus Worm?

The Camallanus worm is a small parasite that requires a host to grow. This parasitic organism is the most widespread among exotic fish and can infest the entire tank fast. This worm is problematic primarily because it’s difficult to discover its presence, especially in the early phases of the infection.

The Camallanus worm will attach itself to the victim’s digestive system, more precisely inside the digestive tract, where it will grow and reproduce. The worm will feed on the host’s blood, sucking in vital nutrients and depriving the victim of the much-needed vitamins and minerals.

There are no noticeable signs of infection in the beginning. Only when the parasite grows and multiply will you be able to observe the first symptoms. At that point, you need to seek treatment fast, otherwise, the fish will die.

How do Camallanus Worms Reproduce?

The Camallanus’s life cycle revolves around its victim’s physiology. In other words, this parasite needs a host to reproduce. Its reproductive cycle looks like this:

  • The female gives birth to first-phase larvae – These are tiny organisms that will infest the fish’s food, consisting of smaller fish or crustaceans. Since these are generally smaller creatures, the larvae will lay dormant, seeking for a larger host. You can’t really see the parasite with the naked eye, and the fish will be oblivious to its presence.
  • Changing hosts – The infected fish or crustaceans will be eaten by a larger fish which will awaken the worm. The parasite can easily withstand the host’s digestive fluids and will attach itself onto its digestive tract to begin the feeding process. The Camallanus worm will rely on the host’s nutrients to grow and develop completely unhinged. When it has grown large enough, it’s time for the third phase – sexual maturity.
  • Reproduction – Once the parasite grows to a sufficient size, it’s time to leave its hosts and seek for another one. The worm will infect the host and infest other small fish and crustaceans, closing the cycle and resetting the reproductive process. It’s at this point that you will observe the worm exiting the fish’s anus. This is when you know that the infestation is severe and that your guppy may be going through some rough times.

How Did Camallanus Get Into Your Tank?

There are 3 primary ways for the Camallanus worm to get into your tank and infest the guppy population:

  1. Infected fish – Purchasing your fish from regular fish shops will always come with significant risks. One of them is purchasing fish infested with the Camallanus worm or other life-threatening parasites. The fish will show no obvious signs of infestation if the parasite’s life cycle is just beginning. You will only notice signs of infestation later on when your guppy has already spent some time in the tank. By this point, you might have multiple infested fish.
  2. Live Food – The female worm will place most of its larvae in the substrate, where it can get mixed in the food residues. From there, they will eventually latch onto other guppies, soon infecting the whole population. It only takes one parasite to reach the tank, and the consequences can turn dark fast.
  3. Live Plants – The female worm may also deposit the first-stage larvae onto the live plants available in the aquarium. This will lead to an even faster infestation rate as plants like Java Moss, and Guppy Grass will spread throughout the tank fast.

Unfortunately, quarantining the infected fish doesn’t guarantee that you will eliminate the problem. Maybe the worm has already laid the first-stage larvae inside the tank. If you’ve noticed worms hanging from the guppy’s anus, that means that the infestation is already advanced.

At that point, it’s no longer enough to treat the infected fish. A more radical approach is necessary.

How to Get Rid of Camallanus?

As I’ve already mentioned, treating the infested fish won’t do any good in the grand scheme of things. To make sure that you’ve overcome the infestation, you need to cleanse the entire tank and sterilize the environment.

At this point, you need to:

  • Remove shrimp, snails, and smaller fish from the tank – If you have several aquatic species coexisting with your guppies, consider removing them from the tank temporarily. We include here guppy fry, snails, and shrimp, among others, which can be more sensitive to medication.
  • Rely on high-profile medication for the best results – Anti-worm medication is highly effective at combating a variety of parasites, Camallanus included.
  • Clean and disinfect all of the tank’s components – The worm’s eggs and larvae may have spread throughout the tank. Thorough cleaning and disinfection are necessary to eliminate all traces of the parasite.
  • Repeat the treatment 2 weeks later – You can never tell if the treatment has been 100% successful in removing all parasites with only one session. I recommend repeating the treatment 2 weeks later to ensure there’s no trace left of the worm.

Regarding which medication to use during the treatment, here are some of the 2 best options available:

  1. The Sera Med Professional Nematol– This product is for EU and UK fish keepers-only and it’s completely safe for animals and human users. It is primarily designed for professional use, but it’s also effective in for private use. You can use the Sera Med Professional to counter several worms and parasites, including the Camallanus, the Milling Headworms, and numerous other nematodes. Read the label to figure out how to use it properly.
  2. Fritz Expel-P– This is intended for US users only, and it’s the perfect choice if you’re looking for something effective and safe for all aquarium inhabitants. The medication will boost the fish’s immune response, allowing them to recover and heal faster. You can use the product against a variety of parasites, including Roundworms, Hookworms, Flatworms, and, last but not least, Camallanus.

Can Camallanus Spread To Other Fish?

Yes, Camallanus can and will spread to other fish, just not directly. The Camallanus worm is an internal parasite that will spread to other fish via its life cycle. The worm will exit the host and lay its first-stage larvae in the surrounding environment. 

These will eventually infest the other fish, soon to overtake the entire fish population. Containing the spread is difficult in its first phases since the infested fish will show no signs of infestation. This is why treating the entire aquarium is necessary to eliminate all traces of the parasite, including larvae and eggs.

Will Camallanus Worms Kill Your Guppies?

Yes, it can happen, although it’s not as common as you might think. After all, the Camallanus worm, like any other internal parasite, will create a symbiotic relationship with the host. The worm will consume some of the host’s incoming nutrients, which means that the worm cannot infest and live in a dead organism.

There’s nothing in it for the worm if the host dies; its whole purpose is to extend this symbiotic relationship as long as possible. However, death can occur if the parasite grows too large and the fish no longer receives vital nutrients as a result.

This is why it’s important to detect the infestation as soon as possible and treat it immediately. The good thing is that once you’ve cleaned the tank of any parasites, it’s unlikely that the Camallanus worm will return.

The risks are even lower if you’re performing regular tank maintenance and water changes.

Are Camallanus Worms Dangerous to Humans?

Fortunately, no, the Camallanus worm won’t infect humans. That isn’t to say that you can be reckless when cleaning the tank. Fish tuberculosis can pass onto humans, and you don’t want to deal with that.

Always clean yourself thoroughly after cleaning the tank and coming into contact with the water or the fish directly.

Should You Euthanize Guppies Infested With Camallanus?

The answer depends on the magnitude of the infestation. If you spot the issue in its early phases, you can probably contain it pretty fast. Some worm-specific medications can be pretty effective against the Camallanus worm, including the 2 I’ve already mentioned in this article.

However, if the medication doesn’t work or the infestation has already taken over the entire guppy population, euthanasia may be the only option left. Nobody wants to kill an entire guppy population, but there may be nothing else you could do.

This is why prevention and early treatment are ideal when it comes to contagious disorders and parasitic infestations. These can wipe out an entire fish population in advanced stages.


It’s not uncommon to for your guppies to experience parasites and various diseases occasionally. The Camallanus worm isn’t particularly dangerous if you can detect its presence in time and resort to adequate treatment.

Try to follow my guidelines with regard to detection, treatment, and what products to use. If nothing works, euthanasia is your last resort.

Just use an ounce of prevention, and you won’t have to consider the latter.

Updated: December 9, 2021
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