Lung Flukes in Dogs: A Parasite in the Lungs

Your dog has had a dry, deep cough for weeks now. Not the harsh honk of kennel cough something quieter, more persistent, easy to write off as “just a cough that won’t quit.” If your dog has ever gotten into raw crab or crayfish near a lake, pond, or coastal stretch, there’s a parasite worth ruling out: the lung fluke.

Key Takeaways

• Lung flukes are flatworm parasites that live in cysts inside a dog’s lungs, most commonly Paragonimus westermani and Paragonimus kellicotti.
• Dogs get infected by eating raw or undercooked crabs or crayfish carrying the parasite’s larval stage.
• The main sign is a chronic, deep, intermittent cough but many infected dogs show no obvious symptoms at all.
• Diagnosis relies on finding the parasite’s eggs in feces or coughed-up material, backed up by chest X-rays.
• Several deworming medications treat lung fluke infection effectively once it’s identified.

What Are Lung Flukes?

Lung flukes are parasitic flatworms trematodes that settle inside cysts, primarily in a dog’s lungs. The two species that matter most for dogs are Paragonimus kellicotti and Paragonimus westermani, and while the lungs are their preferred home, they’ve occasionally been found in other organs, and even the brain, since the adult flukes Paragonimus kellicotti and Paragonimus westermani usually live in cysts or bulla, primarily in the lungs of dogs, and they also have been found rarely in other organs or the brain.

Paragonimus westermani is the species with the widest reach across Asia, and it’s established in India specifically, alongside two related species that share its range, since Paragonimus westermani, the P. skrjabini complex, and P. heterotremus are distributed through India and Southeast Asia. This makes lung fluke infection a genuine, if uncommon, consideration for Indian pet parents particularly in eastern and northeastern regions where freshwater crab and crayfish consumption is more common, both by people and by dogs who scavenge near water bodies.

How Do Dogs Get Lung Flukes?

The lung fluke’s life cycle is genuinely unusual, and understanding it explains exactly how to prevent infection.

1. An infected dog coughs up fluke eggs, swallows them, or passes them in feces, since the eggs from the adult flukes pass through the cyst wall, are coughed up, swallowed, and passed in the feces.
2. The eggs hatch, and the emerging larvae find their way into freshwater snails the first intermediate host in the cycle, since the life cycle includes several snails as the first intermediate host.
3. Inside the snail, the parasite develops further, then moves on to infect crayfish or crabs, the second intermediate host, since crayfish or crabs act as the second intermediate host in the life cycle.
4. A dog becomes infected by eating raw or undercooked crayfish or crabs that are carrying the encysted parasite, since dogs become infected by eating raw crayfish or crabs that contain the encysted parasite.
5. Once eaten, the young flukes travel through the dog’s body and settle in the lungs, where they mature into adults, since the young flukes eventually migrate to the lungs where they become established.

In short: no raw crab or crayfish, no lung fluke infection. This is the single most important fact for prevention.

Symptoms of Lung Fluke Infection in Dogs

Here’s the tricky part many dogs carrying lung flukes show no signs at all. When symptoms do appear, they tend to build slowly and quietly.

• A chronic, deep, intermittent cough the hallmark sign, often mistaken for a lingering cold or mild kennel cough, since infected animals may have a chronic, deep, intermittent cough
• Gradual weakness and lethargy as the infection continues, since infected animals may eventually become weak and lethargic
• In many dogs, the infection simply goes unnoticed, with no visible symptoms at all, since many infections pass unnoticed

In more advanced cases, the cyst-like bullae the flukes form in the lung tissue can rupture, allowing air to leak into the chest cavity and causing a sudden lung collapse a rare but serious complication, since lung bullae may form, causing spontaneous pneumothorax.

Because the main sign a persistent cough overlaps with so many other, more common respiratory conditions, lung flukes are easy to miss unless your vet specifically considers a dog’s history around lakes, rivers, or raw seafood.

How Vets Diagnose Lung Flukes

Diagnosis centres on finding physical evidence of the parasite rather than symptoms alone.

A diagnosis is based on identifying the characteristic eggs of the parasite in a dog’s feces or in material coughed up during an episode, since a diagnosis is based on finding the characteristic eggs in feces or coughed-up material. X-rays then help pinpoint exactly where in the lungs the flukes have settled, since the location of the flukes in the lungs is determined by x-rays. In some cases, vets go a step further and perform a transtracheal wash flushing and sampling fluid from the airway to detect larvae or eggs that fecal testing alone might miss, since additional diagnostic testing such as a transtracheal wash may be performed to detect larvae or eggs.

Treatment for Lung Flukes in Dogs

The good news: once identified, lung fluke infection responds well to treatment. Several deworming medications are effective against the parasite, and your vet will choose based on your dog’s overall health and the severity of infection, since several drugs provide effective treatment for lung fluke infections. Veterinary literature has documented positive outcomes with medications such as praziquantel and fenbendazole in treating this specific infection, underscoring that lung fluke disease, while unusual, is very manageable once caught.

In rare cases involving a ruptured bulla and lung collapse, more intensive treatment including hospitalisation and, occasionally, surgery on the affected lung lobe may be needed alongside deworming medication.

Praziquantel is one of the active ingredients vets commonly reach for against flukes and other flatworm parasites, and it’s found in several broad-spectrum dewormers available in India, including DRONTAL PLUS TASTY TABLET and MILBEMAX DOG TABLET. Your vet will confirm the right medication and dosage for your dog’s specific infection never self-medicate a suspected lung fluke case without a proper diagnosis first.

Preventing Lung Fluke Infection

Prevention comes down to one simple rule: never let your dog eat raw or undercooked freshwater crabs or crayfish. A few practical steps for Indian pet parents, especially those near lakes, rivers, or coastal areas:

• Keep dogs leashed or supervised near water bodies where they might scavenge crustaceans
• Never feed raw seafood of any kind, including as a “natural” treat
• If your dog develops a persistent, unexplained cough and has known access to freshwater crabs or crayfish, mention this history to your vet directly
• Routine deworming as recommended by your vet helps manage broader parasite risk, even though lung flukes specifically require raw crustacean exposure to take hold
• During recovery from any parasitic infection, a herbal immune-support supplement like IMMUNOL LIQUID can help support your dog’s overall immunity alongside the treatment your vet prescribes

Frequently Asked Questions

Can humans catch lung flukes from dogs?
Not directly from an infected dog. People get infected the same way dogs do by eating raw or undercooked crab or crayfish carrying the parasite. It’s the shared food source, not the dog, that poses the shared risk in a household.

Is lung fluke infection common in India?
It’s uncommon overall, but Paragonimus westermani and related species are established across parts of India and Southeast Asia, particularly wherever freshwater crab or crayfish are part of the local diet or environment. Dogs in these regions with access to raw crustaceans carry a real, if low, risk.

How long does a lung fluke infection take to show symptoms?
This varies widely, and many dogs never show obvious symptoms at all. When a cough does develop, it’s usually described as chronic and intermittent rather than sudden, meaning it can take weeks or longer to become noticeable.

Can lung flukes be fatal in dogs?
Most infections are manageable with deworming treatment. Serious complications, such as a ruptured lung cyst causing lung collapse, are rare but can become life-threatening if not treated. This is why any dog with a persistent unexplained cough and relevant exposure history should be checked promptly.

Do I need to worry about lung flukes if my dog never eats raw fish or seafood?
No. Since infection specifically requires eating raw or undercooked crab or crayfish carrying the encysted parasite, dogs that never have access to raw crustaceans are not at risk of lung fluke infection through this route.

References

1. Merck Veterinary Manual — Lung Flukes in Dogs
2. Merck Veterinary Manual — Lung Flukes in Dogs and Cats (Professional Content)