Lungworms are parasitic worms that can infect the lungs and associated blood vessels of animals. Slugs are common garden mollusks. Pet owners often wonder about the connection between these two organisms and the potential risk to their beloved companions. Certain lungworm species utilize slugs as a part of their complex life cycle, posing a health risk to pets.
Not All Slugs
Not every slug carries lungworm. Only specific lungworm species use slugs and snails as intermediate hosts to complete their life cycle. For instance, Angiostrongylus vasorum, known as French heartworm, primarily affects dogs, while Aelurostrongylus abstrusus affects cats.
Slugs and snails become infected when they ingest lungworm larvae passed in the feces of an infected animal, such as a dog or fox. The larvae then develop within the mollusk to an infective stage. A slug must ingest these larvae to become a carrier.
Life Cycle and Transmission
The lungworm life cycle begins with an infected animal. Adult lungworms reside in the lungs or associated blood vessels of the definitive host, such as a dog or cat, where they lay eggs. These eggs hatch into first-stage larvae, which are coughed up, swallowed, and passed into the environment through feces.
Slugs and snails, acting as intermediate hosts, ingest these larvae. Inside the mollusk, the larvae develop into the infective third stage. When a susceptible animal, like a dog or cat, ingests an infected slug or snail, or their slime trail containing larvae, the parasite completes its development within the new host. Other animals like frogs, lizards, rodents, or birds can also act as paratenic hosts, carrying infective larvae after eating infected slugs or snails, and transmitting the parasite if consumed by a pet.
Recognizing Lungworm Infection
Clinical signs of lungworm infection in pets can vary significantly and may be subtle, making diagnosis challenging. In dogs, symptoms of Angiostrongylus vasorum infection include coughing, difficulty breathing, reduced exercise tolerance, lethargy, and weight loss. More severe cases might present with poor blood clotting, leading to excessive bleeding, or neurological signs.
For cats infected with Aelurostrongylus abstrusus, symptoms are often milder, appearing as respiratory signs like coughing, wheezing, and dyspnea (difficulty breathing). Infected cats may also show nasal discharge, reduced appetite, and general lethargy. Since these symptoms can resemble other conditions, a veterinary consultation is important if a pet exhibits any of these signs.
Protecting Your Pets from Lungworm
Several practical measures can help reduce the risk of lungworm infection in pets. Prevent pets from eating slugs and snails, and discourage them from consuming other potential paratenic hosts like frogs. Regularly clean outdoor food and water bowls, as well as toys left outside, to eliminate larvae present in slug or snail slime trails.
Promptly picking up dog feces helps break the lungworm life cycle, preventing larvae from infecting slugs and snails in the environment. Consult a veterinarian for deworming protocols, as not all products are effective against lungworm, and some may require monthly application for prevention. While complete elimination of risk is difficult for pets that spend time outdoors, these preventative steps significantly lower their exposure to the parasite.