Crenosoma vulpis

Synopsis

CAPC Recommends:

• Canine crenosomiasis may mimic allergic respiratory reactions and may be misdiagnosed.
• The most effective way to diagnose Crenosoma vulpis is collection of first stage larvae in feces using a Baermann technique.
• The intermediate host is a mollusk and foxes are a natural definitive host.

Species

Canine

Crenosoma vulpis – fox bronchial worm.

Crenosoma vulpis is a parasite of foxes that occasionally makes its way into dogs. They live in the bronchi where they cause mild catarrhal inflammation but no nodule formation.

Overview of the Life Cycle

Females live in the bronchi and produce larvae that are carried to the intestine by the tracheal route. These larvae enter snails where they develop to the infective third stage. Dogs become infected when they eat the infected snail; the prepatent period is 19 days.

Stages

• Adult males are 3.5 to 8 mm long and the females are 12 to 16 mm long. The anterior end of the body is through into 18 to 26 cuticular folds that encircle the body and give the worms their crenated appearance. The female is ovoviviparous.
• The first-stage larvae shed in the feces are about 200 μm long with the oral ends bluntly conical and the tips of the tails tapering smoothly to the end without any kink, undulation, or spine. The esophagus is about one-third of the total body length.

Disease

• In dogs, clinical disease is seldom more than a persistent cough.
• Third stage larvae can cause pneumonia and adults in the lung can cause bronchitis and bronchiolitis.
• Endoscopic evaluation of 10 naturally infected dogs demonstrated mucosal erythema, purulent exudate, irregular mucosal surface and bronchial hemorrhage (Unterer et al., 2002).
• Clinical crenosomiasis is often misdiagnosed and can mimic allergic respiratory disease.

Prevalence

• Widely distributed around the world in fox populations and in dogs that share the same environment.

Host Associations – Transmission between Hosts

• This is a parasite of foxes and dogs.
• Transmission requires the ingestion of an intermediate host, mollusks.
• Mice have been experimentally shown to serve as paratenic hosts.

Prepatent Period – Environmental Factors

• The prepatent period is 19 days.

Site of Infection – Pathogenesis

• The adult worms live in the lumen of the bronchi where they may cause mild inflammation.

Diagnosis

• Diagnosis is made by finding the characteristic larvae with a conical head and pointed tail in the feces or by finding the worms in the bronchi at necropsy.
• Larvae can be collected best from feces by Baermann technique.

Treatment

• Fenbendazole 50mg/kg daily for 3 days has been shown effective in treating a naturally infected dog (Peterson et al., 1993).
• In experimentally infected dogs, Conboy et al (2013) demonstrated that a single oral dose of milbemycin oxime (5mg/kg) and praziquantel (5mg/kg) was 98.7% effective in treating C. vulpis.Very few adult worms (1-2) were recovered from 4/8 infected dogs and larval counts in feces decreased.
• A single topical application of 10% imidacloprid and 2.5% moxidectin was effective in clearing adult worms in 9/9 experimentally infected dogs, and 1 week post-treatment larvae were no longer detected in feces (Conboy et al., 2009).

Control and Prevention

• Routine preventatives are probably not protective.
• Prevent access to the intermediate host.

Public Health Considerations

• No human health hazard appears to be associated with Crenosoma vulpis.

Selected References

• Bowman DD. Georgis’ Parasitology for Veterinarians. 10ed. Elsevier. 2014.
• Conboy G, Hare J, Charles S, Settje T, Heine J. Efficacy of a single topical application of Advantage Multi® (=Advocate®) topical solution (10% imidocloprid + 2.5% moxidectin) in the treatment of dogs experimentally infected with Crenosoma vulpis.Parasitol Res. 2009; 105:S49-S54.
• Conboy G, Bourque A, Miller L, Seewald W, Schenker R. Efficacy of Milbemax (milbemycin oxime + praziquantel) in the treatment of dogs experimentally infected with Crenosoma vulpis. Vet Par. 2013; 198:319-324.
• Peterson EN, Barr SC, Gould WJ, Beck KA, Bowman DD. Use of fenbendazole for treatment of Crenosoma vulpis infection in a dog. JAVMA. 1993; 202:1483-1484.
• Stockdale PHG and Hulland TJ. The pathogenesis, route of migration, and development of Crenosoma vulpis in the dog. Path. Vet. 1970; 7:28-42.
• Unterer S, Deplazes P, Arnold P, Flückiger M, Reusch CE, Glaus TM. Spontaneous Crenosoma vulpis infection in 10 dogs: laboratory, radiographic and endoscopic findings. Schweiz Arch Tierheilkd. 2002; 144:174-179.