Eucoleus aerophilus

Synopsis

CAPC Recommends:

• Eggs with anastomosing ridges on the outer shell and bipolar plugs are found in the feces and sputum of infected animals.
• Earthworms may serve as paratenic hosts.
• Bronchial capillarids may be considered with respiratory infections not responding to antibiotics and can be verified by recovering of eggs by flotation.

Species

Canine

Feline

• Eucoleus aerophilus (syn.Capillaria aerophila)– feline and canine bronchial capillarid.
• Eucoleus aerophila is primarily a parasite of the respiratory tract of the fox; it has also been reported from the dog, cat, raccoon dog, hedgehog, wolf, lynx, and mustelids in North America, South America, and Europe.

Overview of the Life Cycle

• The life cycle is direct. Eggs are in the sputum or feces and embryonate in 30 to 50 days. Larvae from ingested eggs hatch in the small intestine, penetrate the mucosa, and migrate by the bloodstream to the lungs. This takes 7 to 10 days. Larvae penetrate the alveoli, migrate up the air passages as they develop, and reach maturity about 40 days after infection. Adult worms inhabit the epithelium of the bronchioles, bronchi, and trachea where their thin bodies are threaded through the epithelial surface.

Stages

• Adults are long and thin and threaded through the mucosa. Males are 1.5 to 2.5 cm long and females 2 to 4 cm long. The male has two caudal lobes and a single spicule with a spiny sheath. The vulva of the female is near the posterior end of the esophagus.
• Eggs are brown, oval, and 60 µm long by 30 µm wide with anastomosing ridges on the outer shell and asymmetrical, bipolar plugs.
• Eggs contain a single cell when passed.
• The larval stages are usually not observed.

Disease

• Light infections are usually inapparent.
• Young animals are the most susceptible.
• Severe infections are characterized by a cough, nasal discharge, dyspnea, anorexia, and debilitation caused by tracheitis, bronchitis, and sometimes pneumonia.

Prevalence

• Not uncommon in either dogs or cats in North America, South America and Europe.
• One study found 0.4% of 6458 canine fecal samples in the US were positive for Eucoleus spp. (Blagburn et al., 1996).
• A study in Germany found 69.4% of foxes sampled were infected with E. aerophilus (Shug et al., 2018).
• May be more prevalent in hunting dogs with access to foxes.

Host Associations – Transmission between Hosts

• This is a parasite of foxes, dogs, and cats. Some think that foxes serve as the reservoir for infections in domestic animals.
• Transmission is fecal-oral; no known intermediate hosts have been documented.
• Earthworms have been suggested to be a paratenic host.

Prepatent Period – Environmental Factors

• About 40 days.
• Eggs may remain viable in the environment for over a year.

Site of Infection – Pathogenesis

• Infections in cats have been reported as subclinical to chronic bronchitis including bronchovesicular sounds, sneezing, wheezing and dry cough.
• Large numbers of worms can cause bronchopneumonia and respiratory failure can occur.
• The adult worms live threaded through the mucosa of the trachea, bronchi, and bronchioles.
• Tracheobronchitis, pulmonary edema, and hemorrhage, and sometimes pneumonia, may be seen at necropsy.

Diagnosis

• Diagnosis is made by identification of the eggs in the sputum or feces.
• The eggs in the feces must be differentiated from those of Trichuris spp. (which are larger and have a smooth shell), Eucoleus boehmi(that contain a partially developed embryo when passed and tiny pits on the outer shell surface), and Personema plica and Pearsonema felis cati that can be in feces contaminated with urine.

Treatment

• Ivermectin or benzimidazoles have been used.
• One study showed efficacy using imidacloprid 10%/moxidectin 1% topical in cats. In this study, eggs were no longer seen in feces 7 days post-treatment and clinical signs resolved in 9 of 11 cats within 11 days post-treatment (Di Cesare et al., 2017).

Control and Prevention

• Routine preventatives are probably not protective.

Public Health Considerations

• There have been very rare reports of human infection with this parasite from Russia and Morocco.

Selected References

• Bowman DD, Hendrix CM, Lindsay DS, Barr SC. Feline clinical parasitology. Ames: Iowa State University, Blackwell Science Company. 2002.
• Blagburn BL, Lindsay DS, Vaughn JL, Rippey NS, Wright JC, Lynn RC, Kelch WJ, Ritchie GC, Hepler DI. Prevalence of canine parasites based on fecal flotation. Compend Contin Educ Pract Vet. 1996; 18:483-509.
• Cervone M, Messina N, Perruci S. Nasal capillariosis due to Eucoleus boehmi in two naturally infected dogs. Revue Vétérinaire Clinique. 2017; 52: 41-45.
• Conboy G. Helminth parasites of the canine and feline respiratory tract. Vet Clin Small Anim. 2009; 39: 1109-1126.
• Di Cesare A, Veronesi F, Capelli G, Deuster K, Schaper R, Basano FS, Nazzari R, Paoletti B, Traversa D. Evaluation of the efficacy and safety of an imidacloprid 10%/moxidectin 1% spot-on formulation (Advocate®, Advantage®Multi) in cats naturally infected with Capillaria aerophila.Parasitol. Res. 2017; 116: S55-S64.
• Levine ND. Capillariins and related nematodes. In: Nematodes parasites of domestic animals and of man. 2nd Edition. Minneapolis: Burgess; 1980. p. 428–44.
• Shug K, Krämer F, Schaper R, Hirzmann J, Failing K, Hermosilla C, Taubert A. Prevalence survey on lungworm (Angiostrongylus vasorum, Crenosoma vulpis, Eucoleus aerophilus) infections of wild red foxes (Vulpus vulpes) in central Germany. Parasites and Vectors. 2018; 11:85.