Fox Lungworm (C. vulpis)

CLASSIFICATION 

Kingdom: Animalia / Phylum: Nematehelmintha / Class: Nematoda / Order: Trichostrongyloidea / Family: Metastrongyloidea 

DESCRIPTION 

Crenosoma vulpis, also called the “fox lungworm” is a member of the lungworm (metastrongyle) family of parasites and affects dogs and foxes, and is found in many areas of the world, including the UK. Unlike its relative, Angiostrongylus vasorum, Crenosoma rarely causes fatal disease in dogs and is more often associated with mild to moderate respiratory signs. Cats are not affected by this parasite (though can be affected by their own species of lungworm).

IDENTIFICATION

Crenosoma vulpis (dogs) 
Adult Crenosoma vulpis worms live in the bronchioles, bronchi and trachea of infected dogs and foxes. Adult females grow to around 12-16 mm in length (male worms are shorter at around 4-8 mm in length). 

First stage larvae (L1) in the faeces are useful in diagnosis, and should be distinguished from other lungworm larvae. 

LIFE CYCLE

Adult Crenosoma worms live in the bronchioles, bronchi and trachea of infected dogs and foxes. Adult female worms release eggs, which hatch as first stage larvae (L1) in the bronchioles, where they cause irritation and inflammation. The larvae are coughed up and swallowed, and passed via the faeces, where they can infect slugs and snails in the environment. Further development of the larvae (to the third, L3, larval stage) occurs in the slug or snail. Dogs become infected by eating an infected mollusc; digestion of the mollusc releases the larvae, which penetrate the intestinal wall, undergo further development, and then migrate via the liver and venous circulation back to the bronchi, where they mature into adult worms. 

TRANSMISSION 

 Dogs become infected with C. vulpis by ingesting infected slugs or snails. It is worth remembering that these molluscs can be very small and it is not necessarily the case that the owner (or even dog!) is aware of ingestion; dogs that eat grass might inadvertently eat tiny molluscs attached to the blades, small slugs can fall into water bowls or be attached to a dog toy. As foxes can also become infected by this parasite, they can act as an environmental reservoir, i.e. infected foxes shedding larvae into the environment may pose a risk to dogs in that area. Increasing fox numbers could potentially put more dogs at risk. 

HEALTH RISKS 

Canine Diseases 
Disease in dogs is usually related to the respiratory system, and symptoms include coughing (which may be a dry rasp, or is sometimes productive), difficulty breathing, discharge from the nose and retching, among others. The disease can sometimes be mistaken with allergic respiratory disease as the presenting signs can be similar. Dogs may be lethargic with a reduced appetite. The bleeding abnormalities and neurological signs that can be a feature of infections with the related lungworm Angiostrongylus vasorum, are not a feature of Crenosoma infections, and, again unlike A. vasorum, C. vulpis infections are rarely fatal. 
 

Zoonotic Diseases 
Crenosoma vulpis is not considered a disease risk to people. 

DIAGNOSIS

Diagnosis usually involves demonstrating the presence of first stage larvae (L1) in the faeces of an infected dog, using the modified Baermann technique. Ideally faecal samples should be collected over three consecutive days, and analysed separately, as larvae may be missed if only a single sample is examined. C. vulpis larvae can be differentiated from other lungworm larvae by their morphological characteristics. 

MANAGEMENT 

Treatment 
Treatment involves administering an anthelmintic that is effective against this parasite, there is a licensed treatment available for C.vulpis in a spot-on preparation or a tablet. 

Prevention 
There is no licensed preventative medication available for C. vulpis. Some general measures that may be undertaken include: