Parasitology
Spirocerca lupi in dogs: prophylactic effect of doramectin

https://doi.org/10.1016/S0034-5288(03)00115-2Get rights and content

Abstract

Spirocerca lupi is primarily a parasite of dogs, which typically causes oesophageal nodules, aortic aneurysms, and spondylitis. This study investigated the efficacy of doramectin as a prophylactic agent for canine spirocercosis. Five beagle dogs were injected subcutaneously with doramectin (400 μg/kg on 3 occasions 30 days apart q30d), while 5 other beagle dogs served as untreated controls. All dogs were inoculated with 40 infectious S. lupi larvae (L3) one month after the last doramectin treatment. All control dogs and 4/5 treated dogs became infected. Two control dogs died of ruptured aortic aneurysms, while no deaths occurred in treated dogs. Oesophageal nodules appeared 40–103 day later in treated as compared to control dogs, and eggs appeared in the faeces 49–106 day later in treated as compared to control dogs. The mean faecal egg count on day 223 in the treatment group was reduced by 99.77%. All control dogs had thoracic radiographic changes during the study, while only 2/5 study dogs showed radiographic changes. This study shows that although doramectin did not entirely prevent canine spirocercosis it reduced the clinical signs associated with infection and delayed and reduced egg output.

Introduction

The nematode Spirocerca lupi is primarily a parasite of dogs, although other animals, particularly carnivores may be affected. It has a worldwide distribution, but is most prevalent in warm climates (Bailey, 1972). The pathogenesis of spirocercosis results from the migration and continued tissue presence of infective larvae and adults. Oesophageal nodular masses and granulomas, aortic scars and aneurysms are the most frequent lesions, and are considered pathognomonic. Spondylitis and spondylosis of the caudal thoracic vertebrae (T6–T12) are also typical lesions (Fox et al., 1988; Soulsby, 1986; Urquhart et al., 1996).

Oesophageal lesions often interfere with swallowing and cause persistent regurgitation and/or vomiting (Bailey, 1972; Chhabra, 1973; Fox et al., 1988). Sudden death may be caused by aortic aneurysm rupture (Ivoghli, 1977; Ndiritu, 1976). A definite diagnosis of spirocercosis is made by detecting the characteristic eggs in the faeces (Markovics and Medinski, 1996; Soulsby, 1986). Oesophageal nodules or granulomas may be demonstrated by radiography and oesophagoscopy (Berry, 2000; Fox et al., 1988).

Several anthelminthics are suggested for the treatment of canine spirocercosis with variable efficacies. Diethylcarbamazine at a dose of 20–500 mg/kg was determined to be beneficial in temporarily suppressing faecal egg shedding, but did not affect adult worms (Seneviranta et al., 1966). Until recently, disophenol was the only anthelminthic proven effective against of S. lupi adults, but was not effective against larvae (Darne and Webb, 1964; Seneviranta et al., 1966). Disophenol is no longer commercially available. Recently, doramectin was found to be effective in the treatment of 7 naturally infected dogs with spirocercosis. Three doses (200 μg/kg SC q14d) were effective in eliminating oesophageal lesions in 5 dogs. A higher oral daily dose (500 μg/kg) for 6 additional weeks resulted in complete resolution of oesophageal lesions in the remaining 2 dogs (Berry, 2000).

A recent study indicated an emerging outbreak of spirocercosis in Israel and despite increased awareness, disease prevalence and geographic distribution has been increasing (Mazaki-Tovi et al., 2002). Theoretically, disease incidence can be reduced by disposal of infected dogs faeces, control of coprophagus beetles and paratenic hosts and by preventing healthy dogs from eating beetles and uncooked viscera. However, due to the ubiquity of the intermediate and paratenic hosts in endemic regions, disease control is difficult (Soulsby, 1986). No prophylactic treatment for canine spirocercosis has been suggested to date. This study investigated the efficacy of doramectin as a prophylactic treatment for canine spirocercosis.

Section snippets

Animals

Ten beagle dogs (6 males, 4 females), aged 6–10 years participated in this study. All dogs were considered to be healthy based on physical examination, complete blood count, serum biochemistry and faecal flotations. Dogs were randomly allocated to 2 groups of 5 dogs. Each dog in the study group (dogs A–E) was injected subcutaneously with doramectin (Dectomax, Pfizer, 400 μg/kg, 3 times at 30 days intervals). The 5 other dogs (F–J) served as untreated controls. The two groups were housed in

Experimental infection

Nine of 10 dogs became infected during the study period. Infection was deemed positive in 7 dogs (4 study dogs (A–D), and 3 control dogs (F–H)) by observing oesophageal nodules upon endoscopy and typical eggs in faecal flotation. Two control dogs (I, J) died suddenly on days 33 and 54 PI, respectively. Infection was confirmed in these dogs on post mortem examination. There were no mortalities in the study group. One study dog (E) did not become infected during the study course, and continued to

Discussion

This study examined the efficacy of doramectin in the prevention of canine spirocerosis. Prophylactic efficacy was evaluated by following the appearance, number and size of oesophageal nodules, the number of S. lupi eggs shed in the faeces, and the onset and nature of typical radiographic findings.

The use of doramectin in dogs has been investigated in several studies, and it was found to be with no sides effects, and reduced infection in puppies born to bitches infected with Ancylostoma caninum

References (21)

  • M. Mazaki-Tovi et al.

    Canine spirocercosis: clinical, diagnostic, pathologic, and epidemiologic characteristics

    Veterinary Parasitology

    (2002)
  • W.S. Bailey

    Spirocerca lupi: a continuing inquiry

    Journal of Parasitology

    (1972)
  • W.L. Berry

    Spirocerca lupi esophageal granulomas in 7 dogs: resolution after treatment with doramectin

    Journal of Veterinary Internal Medicine

    (2000)
  • R.C. Chhabra

    Symptoms and pathogenesis of spirocercosis in dogs

    Indian Veterinary Journal

    (1973)
  • A. Darne et al.

    The treatment of ancylostomiasis and of spirocercosis in dogs by the new compound, 2,6-diiodo-4-nitrophenol

    Veterinary Record

    (1964)
  • E. Dvir et al.

    Radiographic and computed tomographic and clinical presentation of spirocercosis in the dog

    Veterinary Radiology and Ultrasound

    (2001)
  • C. Epe et al.

    A study on the prevention of prenatal and galactogenic Toxocara canis infections in pups by treatment of infected bitches with ivermectin or doramectin

    Applied Parasitology

    (1996)
  • S.M. Fox et al.

    Spirocercosis in dogs

    Compendium of Continuing Education for the Practicing Veterinarian

    (1988)
  • B. Ivoghli

    Fatal aortic aneurysm and rupture caused by Spirocerca lupi in a dog

    Journal of the American Veterinary Medical Association

    (1977)
  • A. Markovics et al.

    Improved diagnosis of low intensity Spiroceraca lupi infection by the sugar flotation method

    Journal of Veterinary Diagnostic Investigation

    (1996)
There are more references available in the full text version of this article.

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