Spirocerca spp

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Endoscopic view of granulomas associated with S. lupi[1]
Spirocerca lupi
Spirocerca lupi, egg
Spirocerca lupi, dense mass in the esophagus, positive-contrast barium study[1]

Spirocerca spp are a prevalent nematode parasite of dogs in tropical and subtropical countries[2], with up to 5% of urban dogs commonly infected during routine seroepidemiological surveys[3][4].

Spirocerca have a complex life cycle, involving an obligatory coprophagous beetles[5], an optional paratenic host (amphibians, reptiles, birds, and small mammals such as hedgehogs, mice, and rabbits)[6], and the definitive canid host.

A Gram-negative proteobacterial symbiont (Comamonas spp) which parasitizes Spirocerca lupi, is intimately involved in their lifecycle and has recently been targeted as a possible treatment method to target eradication of this parasite[7].

Dogs become infected by eating paratenic hosts. The nematode migrates from the intestines to the adventitia of the visceral arteries and aorta to finally reach the walls of the esophagus. Some go astray and encyst in ectopic sites including the thoracic organs, the gastrointestinal tract, the urinary system, and the subcutaneous tissues[8].

eproductive adults are found in cystic nodules that communicate with the lumen of the esophagus or stomach through fistula. Mature adults lay very small eggs are laid, and are passed in the dog's feces[9].

Species which are parasitic to dogs include:

  • Spirocerca lupi (esophageal worm)

Spirocerca lupi primarily causes esophageal dysphagia in dogs but can induce esophageal diverticula[10] and sarcoma formation in the distal luminal oesophagus in about 25% of cases[11]. Necrotizing sialometaplasia has also been commonly reported, as well as aortic aneurysm or rupture and secondary pulmonary osteoarthropathy and ankylosing spondylitis of the caudal thoracic vertebrae[12].

Affected dogs often present with dysphagia, weight loss, vomiting, hemoptysis and dyspnea associated with pleural effusion. Hemothorax is sometimes observed in severe cases.

Diagnosis is based on presenting clinical signs and finding Spirocera eggs in feces. However, dogs with neoplastic nodules shed significantly fewer eggs than dogs with non-neoplastic nodules and may be difficult to detect[13].

Supportive evidence for a diagnosis is based on thoracic barium radiographs and pneumoesophagography[14]. Definitive diagnosis requires serological testing and identification of parasite in biopsied material.

Treatment involves ivermectin-based drugs such as doramectin (0.2 - 0.5 mg/kg), given subcutaneously every second week for 4 - 6 treatments or daily oral dosing for 1 - 2 months[15].

Monthly milbemycin oxime may be effective as a prophylactic anthelmintic programme to protect puppies in endemic areas[16].

References

  1. 1.0 1.1 Protea Animal Clinic
  2. de Waal PJ et al (2012) High within-host genetic variation of the nematode Spirocerca lupi in a high-density urban dog population. Vet Parasitol 187(1-2):259-266
  3. Gholami I et al (2011) Seroepidemiological survey of helminthic parasites of stray dogs in Sari City, northern Iran. Pak J Biol Sci 14(2):133-137
  4. Cantó GJ et al (2011) The prevalence and abundance of helminth parasites in stray dogs from the city of Queretaro in central Mexico. J Helminthol 85(3):263-269
  5. DU Toit CA et al (2012) Role of dung beetle feeding mechanisms in limiting the suitability of species as hosts for the nematode Spirocerca lupi. Med Vet Entomol Jun 20
  6. Bourdeau P (1985) La spirocercose canine. Point Vét 94:693–698
  7. Gottlieb Y et al (2012) A novel bacterial symbiont in the nematode Spirocerca lupi. BMC Microbiol 12(1):133
  8. Mazaki-Tovi M et al (2002) Canine spirocercosis: clinical, diagnostic, pathologic, and epidemiologic characteristics. Vet Parasitol 107:235–250
  9. Bowman, SS (2009) Georgis' Parasitology for veterinarians. Saunders Elsevier. Missouri. pp:211
  10. Pence DB & Stone JE (1978) Visceral lesions in wild carnivores naturally infected with Spirocerca lupi. Vet Pathol 15(3):322-331
  11. Dvir Eet al (2012) Plasma IL-8 concentrations are increased in dogs with spirocercosis. Vet Parasitol 190(1-2):185-190
  12. Le Sueur C et al (2010) Efficacy of a combination of imidacloprid 10%/moxidectin 2.5% spot-on (Advocate® for dogs) in the prevention of canine spirocercosis (Spirocerca lupi). Parasitol Res 107(6):1463-1469
  13. Christie J et al (2011) The sensitivity of direct faecal examination, direct faecal flotation, modified centrifugal faecal flotation and centrifugal sedimentation/flotation in the diagnosis of canine spirocercosis. J S Afr Vet Assoc 82(2):71-75
  14. Kirberger RM et al (2012) Pneumoesophagography and the appearance of masses in the caudal portion of the esophagus in dogs with spirocercosis. J Am Vet Med Assoc 240(4):420-426
  15. Lobetti R et al (2012) Successful resolution of oesophageal spirocercosis in 20 dogs following daily treatment with oral doramectin. Vet J 193(1):277-278
  16. Kok DJ et al (2010) The use of milbemycin oxime in a prophylactic anthelmintic programme to protect puppies, raised in an endemic area, against infection with Spirocerca lupi. Vet Parasitol 174(3-4):277-284