The Life Cycle and Spread of Angiostrongylus Vasorum

Angiostrongylus vasorum, also known as French heartworm, is a parasitic nematode that affects dogs worldwide.

This parasite has a complex life cycle that involves multiple hosts, including snails, slugs, and rodents.

The life cycle begins with the ingestion of infected snail or slug tissue by a rodent, which then serves as an intermediate host.

The parasite then develops into an adult worm in the rodent's lungs.

Adult worms mate and produce microfilariae, which are ingested by snails or slugs.

The microfilariae develop into infective third-stage larvae within the snail or slug, which can then infect a new host.

Snails and slugs are essential for the transmission of Angiostrongylus vasorum to dogs, as they can carry the infective larvae.

Dogs become infected through the ingestion of infected snail or slug tissue, often while exploring outdoors or eating contaminated prey.

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Angiostrongylus vasorum has a multi-host, multi-stage, indirect life cycle. This means it involves multiple hosts and stages, making it a complex process.

Dogs are the definitive hosts, while gastropod molluscs (slugs and snails) are the intermediate hosts. Wild canids, such as red foxes, act as reservoirs. Dogs can become infected by accidentally or intentionally ingesting third-stage larvae from intermediate hosts or from slime trails and paratenic hosts like frogs.

The type of habitat is a significant factor in determining the opportunities for dogs to encounter gastropods. Complex vegetated areas attract gastropods due to better food sources, moisture retention, and ease of movement.

Gastropods are more likely to be found in vegetated environments, and high-risk species are common in the evening and when humidity is high. Climate change is expected to alter gastropod community dynamics and A. vasorum transmission, particularly affecting species like the "Spanish slug".

Here's a breakdown of the life cycle stages:

The pre-patent period is about 6-10 weeks, and adult worms can live for 2 years.

The life cycle of Angiostrongylus vasorum is a complex process that involves multiple hosts and stages. Dogs become infected by accidentally or intentionally ingesting third-stage larvae from gastropod intermediate hosts, such as slugs and snails, or from paratenic hosts like frogs.

The type of habitat is a major factor in determining the opportunities for dogs to encounter gastropods. Dogs are more likely to encounter gastropods in complex vegetated areas with better food sources, moisture retention, and ease of movement.

Gastropods are active in these environments, especially larger slugs in autumn, posing a higher risk to dogs. Smaller slugs, on the other hand, are active year-round.

Dogs are less likely to encounter gastropods on hard surfaces. High-risk gastropod species are especially common in the evening and when humidity is high.

A vasorum prevalence in gastropods can vary geographically within the UK, influenced by timing and environmental factors. This can impact the transmission dynamics of the parasite.

Here's a breakdown of the life cycle:

The French heartworm, also known as Angiostrongylus vasorum, is a parasite that affects foxes and other canids.

Angiostrongylus vasorum can also find its way into dogs, which are not its natural hosts.

Angiostrongylus vasorum has a complex life cycle, and understanding its hosts is key to grasping how it spreads. The natural intermediate hosts are land slugs, land snails, and freshwater snails, with the Arion ater being a natural host.

These hosts play a crucial role in the parasite's life cycle, allowing it to complete its development before infecting its next host. The natural definitive hosts are domestic dogs and various other carnivores, including red foxes, pampas foxes, hoary foxes, and wolves.

Some of the natural definitive hosts include:

Natural paratenic hosts, which don't allow the parasite to complete its development but can still transmit it, include frogs, lizards, mice, and rats.

Disease due to Ang. vasorum is an inflammatory reaction with the subsequent involvement of the surrounding lung tissue, which may be accompanied by interstitial pneumonia, emphysema, thromboarteritis, coagulopathis, anemia, melena, hemoptysis, and congestive right heart failure.

Dogs infected with Ang. vasorum may show no clinical signs at all. Others may experience mild to severe clinical signs, and in some cases, death.

Exercise intolerance, coughing, and dyspnea are common symptoms in dogs infected with Ang. vasorum. These symptoms can progress to right heart failure in advanced cases, characterized by ascites.

Compromised haemostasis can also occur in dogs infected with Ang. vasorum. In rare cases, neurological signs may be observed due to larval migrans in the central nervous system.

The following symptoms can be associated with Ang. vasorum infection:

Prevention and control are crucial when it comes to Angiostrongylus vasorum. Preventing dogs from feeding outdoors, walking in damp environments, and keeping dog toys indoors can minimize exposure to the parasite.

Regular cleaning of outdoor water dishes is also essential. Promptly removing dog faeces is a must, as it can help reduce environmental contamination.

Dogs at high risk of exposure, such as snail or slug eaters, or those living in endemic areas, should receive monthly preventive treatment. This can include anthelmintic treatments containing moxidectin or milbemycin oxime.

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In endemic areas, monthly application of anthelmintic treatments can prevent angiostrongylosis and patent infection with Angiostrongylus vasorum. This is especially important for dogs that are at high risk of exposure.

Here are some preventive measures you can take:

In uncertain areas, testing prior to surgery, in suspected cases, and annual testing of young dogs can help determine endemic status and inform risk-based advice.