Rat Lungworm Disease: Risks to Pets and People
By Dr. Zubair Khalid, DVM, MS, PhD ·
Rat lungworm disease is an infection caused by a parasite that normally lives in rats and uses slugs and snails as intermediate hosts. Dogs and cats get it by eating an infected slug, snail, or the slime trail they leave behind. In pets, the parasite can travel to the brain and spinal cord and cause serious neurologic disease.
This article is educational and is not a substitute for veterinary diagnosis or treatment.
Quick Answer
- Rat lungworm disease in pets comes from eating raw slugs or snails that carry the parasite, not from contact with rats directly [1].
- The parasite is Angiostrongylus cantonensis, and rats are its natural host while slugs and snails carry the infective larvae [1].
- Infected pets may show neurologic signs such as weakness, wobbliness, tremors, or behavior changes, though early signs can be vague [2].
- Diagnosis is difficult and often relies on a veterinarian's suspicion plus specialized testing, since routine tests may not detect it [2].
- Prevention is mostly about controlling slugs and snails in your yard and stopping your pet from eating them.
What Is Rat Lungworm Disease in Pets?
Rat lungworm disease, also called neuroangiostrongyliasis, is a parasitic infection that affects the brain and nervous system [2]. The worm responsible is Angiostrongylus cantonensis, a nematode first described in rats in China in 1935 [1]. It belongs to a family of worms called metastrongyloid lungworms, which have indirect life cycles that require more than one host [3][1].
In its normal life cycle, the adult worms live in rats. Rats pass larvae in their feces, and those larvae are picked up by slugs or snails, where they develop into an infective stage [1]. When a rat eats an infected snail, the larvae migrate to the brain, mature, and then move back into the bloodstream to finish their life cycle in the lungs [1].
Dogs, cats, and people are accidental hosts. When they eat an infected slug or snail, the larvae still travel to the brain, but they cannot complete the life cycle and often die there [1]. That dead-end migration is what causes the inflammation and neurologic damage.
Signs of Rat Lungworm Disease Owners Notice
The signs can range from mild and self-resolving to severe and life-threatening [2]. That wide range makes this disease hard to spot early.
Early or vague signs
- Reduced appetite
- Lethargy or reluctance to move
- Mild wobbliness
- Sensitivity to touch or handling
Neurologic signs
- Weakness in the hind legs
- Tremors or muscle twitching
- Head tilt or circling
- Behavior changes, confusion, or unsteadiness
- Pain along the spine or neck
Respiratory signs
Lungworms in general cause coughing and difficulty breathing, and these signs can worsen if a bacterial or viral infection develops at the same time [3]. Cats with a common lungworm called Aelurostrongylus abstrusus may show chronic weight loss, cough, and wheezing, though many infected cats show no obvious signs at all [4]. Rat lungworm is different because it targets the nervous system more than the lungs, but respiratory signs can still appear.
Because early diagnosis improves the chance that treatment will work, tell your veterinarian right away if you saw your pet eat a slug or snail, even if your pet seems fine [2]. If your dog recently ate a slug or snail, see My Dog Ate a Slug or Snail: Should I Worry About Lungworm?.
Causes and Risk Factors
The single most important cause is eating an infected slug or snail [1]. A few details matter for risk.
| Risk factor | Why it matters |
|---|---|
| Eating raw slugs or snails | This is the main route of infection for pets [1] |
| Licking slime trails | Larvae can be present in snail and slug secretions |
| Access to gardens, compost, or damp yards | These are prime slug and snail habitat |
| Rats in or near the yard | Rats are the natural host and shed the parasite [5] |
| Living in warm, humid regions | The parasite is more common in tropical and subtropical areas [1] |
| Hunting or scavenging outdoors | Cats and dogs that catch prey face higher exposure |
Rats are the key reservoir. A study of urban rats in Sydney, Australia found that 29% were infected with A. cantonensis around public parks and residential areas, and older rats were more likely to be infected [5]. Rats in cities can carry this parasite along with many other zoonotic worms and protozoa [6][7]. That means a rat population near your home raises the odds that local slugs and snails are carrying infective larvae.
The parasite is also spreading. It has been reported in new regions beyond its original range, and it has been recorded on islands south of Europe, including the Canary Islands and the Balearic Islands [1][8]. Climate and urbanization play a role in how rodent-borne parasites spread [7].
How Veterinarians Diagnose Rat Lungworm Disease
Diagnosis is one of the hardest parts of this disease. Early infection is usually difficult to confirm without knowing about exposure or finding the parasite's DNA or antibodies in cerebrospinal fluid, which requires a spinal tap and often hospitalization [2].
A newer approach looks for parasite DNA in a simple blood sample using PCR. In one study, blood samples from 58 animals (55 dogs and 3 cats) with suspected infection were tested this way as a less invasive alternative to spinal fluid collection [2]. This kind of testing is still developing, so availability varies by laboratory and region.
Your veterinarian will also consider other causes of neurologic signs, such as trauma, toxins, or other infections. Routine fecal testing may detect some lungworm larvae, and the Baermann technique is a standard method for finding first-stage larvae in feces [3]. However, rat lungworm larvae are not always easy to find this way.
Expect your veterinarian to ask detailed questions. Did your pet have access to a garden? Have you seen slugs or snails? Has your pet hunted or eaten anything outdoors? Those answers can be as useful as any test.
Treatment Options
There is no single standard treatment protocol for rat lungworm disease in pets, and treatment decisions are made case by case. Studies suggest that treatment works better in the early stages of infection than later, which is one reason early diagnosis matters so much [2].
Treatment usually involves a combination of approaches:
- Antiparasitic medication to target the worm
- Anti-inflammatory drugs, often corticosteroids, to reduce brain and spinal cord swelling
- Supportive care such as fluids, pain control, and nursing care
- Treatment of any secondary infections
Your veterinarian calculates every dose from your pet's weight, current health, and other medications. Never give a pet medication meant for another animal or a human.
For comparison, common feline lungworm (A. abstrusus) is treated with ivermectin at 0.4 mg/kg under the skin once and repeated in two weeks, or selamectin at 6 mg/kg applied topically once [4]. Those doses are specific to that parasite and that drug, and they are not a treatment plan for rat lungworm. Do not use them on your own.
If your pet has heartworm or another parasite, prevention and treatment plans can overlap. See Heartworm Prevention for Dogs and Cats: What Owners Need To Know.
Recovery, Outlook, and Long-Term Management
The outlook depends heavily on how early the infection is caught and how severe the neurologic damage is. Some animals recover fully, some have lasting neurologic deficits, and some do not survive. Because the range of outcomes is so wide, your veterinarian is the best person to give you a realistic picture for your pet [2].
Recovery often takes weeks to months. During that time, your pet may need:
- Repeat veterinary visits to track neurologic progress
- Physical therapy or assisted walking
- A quiet, safe space to prevent falls
- Careful monitoring for new or worsening signs
Long-term management focuses on preventing another exposure. If your pet has permanent neurologic changes, your veterinarian may recommend adjustments to your home, such as ramps, non-slip flooring, or restricted access to stairs.
Prevention: Keeping Slugs and Snails Away From Your Pet
Prevention is the most effective tool you have. The goal is simple: stop your pet from eating raw slugs, snails, or their slime.
In the yard and garden
- Remove slugs and snails by hand, wearing gloves, and dispose of them in sealed bags
- Clear leaf litter, boards, and debris where slugs hide
- Reduce standing water and fix leaky outdoor faucets
- Keep compost bins covered and away from pet areas
- Trim ground cover and keep grass short near doors
- Use slug barriers or traps that pets cannot reach
Around the house
- Check pet food bowls left outside for slugs or snails
- Rinse outdoor water bowls before refilling
- Inspect potted plants and garden produce for hitchhiking snails
- Wash your hands after gardening
For your pet
- Supervise outdoor time, especially in damp areas after rain
- Keep dogs leashed on walks if they scavenge
- Discourage hunting and eating prey
- Keep cats indoors or in a secure enclosure
- Store pet food indoors
About rats
Since rats are the source of the parasite, rodent control matters [5]. Seal gaps around your home, secure trash, and remove food sources. If you keep pet rats, learn how rodent-borne diseases can spread in Pet Rat Zoonotic Diseases: Risks and Prevention. Respiratory problems in pet rats are common for other reasons too, which you can read about in Pet Rat Respiratory Health and Tumors and Pet Rat Respiratory Disease: Mycoplasma and Other Pathogens.
Limitations and When to Contact a Veterinarian
No article can diagnose your pet. Individual cases need a veterinarian who can examine your pet, ask about exposure, and run the right tests.
Contact your veterinarian the same day if:
- You saw your pet eat a slug or snail
- Your pet is wobbling, weak, or unsteady
- Your pet has tremors, a head tilt, or behavior changes
- Your pet is sensitive to touch along the back or neck
Go to an emergency clinic now if:
- Your pet cannot stand or walk
- Your pet has seizures
- Your pet is struggling to breathe
- Your pet is unresponsive or severely disoriented
Schedule a routine visit if:
- You have slugs or snails in your yard and want a prevention plan
- Your pet has a mild cough that is not improving
- You want to discuss parasite prevention for an outdoor pet
Frequently Asked Questions
Can my dog get rat lungworm from another dog?
No. Rat lungworm is not spread directly between dogs or between dogs and cats. Pets get infected by eating infected slugs or snails, which are the intermediate hosts [1]. Rats are the natural host that keeps the parasite in the environment [5].
Is rat lungworm the same as regular lungworm?
No. Rat lungworm is caused by Angiostrongylus cantonensis and mainly affects the brain and spinal cord [2]. Common lungworms like Aelurostrongylus abstrusus in cats live in the lungs and cause coughing, wheezing, and weight loss [4]. They are different parasites with different treatment plans.
Can my pet get rat lungworm from drinking water?
It is not well established that drinking water is a common route of infection. The main route is eating an infected slug or snail [1]. To be safe, rinse outdoor water bowls that may have had snails in them.
How long after eating a slug would my pet show signs?
The timeline is not well established in veterinary research and can vary widely. Some animals show vague signs early, while others develop neurologic signs later [2]. If you know your pet ate a slug or snail, do not wait for signs. Call your veterinarian right away.
Can people get rat lungworm from their pets?
People do not get rat lungworm from contact with an infected dog or cat. Human infection happens the same way it does in pets, by eating infected slugs or snails or contaminated produce [1]. Wash your hands after gardening and rinse raw produce well.
Related Articles
- My Dog Ate a Slug or Snail: Should I Worry About Lungworm?
- Heartworm Prevention for Dogs and Cats: What Owners Need To Know
- Lungworm in Dogs: Angiostrongylus and Oslerus Diagnosis Guide
- Are Dog Worms Contagious to Other Pets and People?
- Cat Skin Parasites, Fungus, and Worms: What to Know
- Zoonotic Risk: Can Humans Get Parasites from Pets? A Veterinary Public Health Perspective
- Zoonotic Parasites in Dogs: Intestinal Worms and Human Health Risks
References
- Biology, systematics, life cycle, and distribution of Angiostrongylus cantonensis, the cause of rat lungworm disease. Hawai'i journal of medicine & public health : a journal of Asia Pacific Medicine & Public Health, 2013.
- Detection of rat lungworm (Angiostrongylus cantonensis) infection by real-time PCR from the peripheral blood of animals: a preliminary study. Parasitology research, 2024.
- Lungworm Infection in Animals - Respiratory System. Merck Veterinary Manual.
- Lung Nematodes in Small Animals - Respiratory System. Merck Veterinary Manual.
- Older urban rats are infected with the zoonotic nematode Angiostrongylus cantonensis. Current research in parasitology & vector-borne diseases, 2024.
- Parasite Fauna and Coinfections in Urban Rats Naturally Infected by the Zoonotic Parasite Angiostrongylus cantonensis. Pathogens (Basel, Switzerland), 2023.
- Rodent-Borne Parasites and Human Disease: A Growing Public Health Concern. Animals : an open access journal from MDPI, 2025.
- Angiostrongylosis in Animals and Humans in Europe. Pathogens (Basel, Switzerland), 2021.