Successful resolution of oesophageal spirocercosis in 20 dogs following daily treatment with oral doramectin

Evaluation of a treatment protocol in dogs with intraspinal spirocercosis

OBJECTIVE

To evaluate the efficiency and safety of a doramectin-based treatment protocol in dogs affected by intraspinal spirocercosis (Spirocerca lupi).

ANIMALS

Client-owned dogs that were admitted to a veterinary hospital during 2021 to 2022 with acute onset of neurological signs and diagnosed with intraspinal spirocercosis. All dogs underwent complete neurological evaluation, CSF analysis, PCR confirmation of CNS S lupi infection, and follow-up evaluation of at least 6 months.

PROCEDURES

Upon diagnosis, dogs were treated with doramectin at a dose of 400 μg/kg, SC, q 24 h for 3 consecutive days, followed by the same dose once a week for 6 weeks. Prednisone was administered at a dose of 1 mg/kg, PO, q 24 h and tapered every 3 days. Antimicrobial clindamycin was administered at a dose of 12.5 mg/kg, PO, q 12 h for 7 days to reduce the risk of secondary spinal cord infection. Short- and long-term outcomes (1 week to 56 months) were recorded.

RESULTS

8 dogs fulfilled the inclusion criteria, 7 of which presented with neurological deficits and 1 with cervical pain. Initiation of treatment was associated with stopping the deterioration in 7 of 8 dogs. Seven dogs improved and 6 recovered ambulation. One dog was euthanized due to lack of improvement. Six of the recovered dogs were still ataxic on the last follow-up examination at 6 to 56 months. No adverse effects of the drug were noted.

CLINICAL RELEVANCE

Frequent administration of doramectin was found to be safe and effective in preventing neurological deterioration in dogs with intraspinal spirocercosis.

Evaluation of a spot-on imidacloprid-moxidectin formulation (Advocate®) for the treatment of naturally occurring esophageal spirocercosis in dogs: a double-blinded, placebo-controlled study

Background

Dogs are the definitive hosts of Spirocerca lupi. Spirocercosis is treated by prolonged avermectin administration by injection or daily oral doses. In this prospective, double-blinded, placebo-controlled, clinical trial, the efficacy of imidacloprid and moxidectin spot-on formulation (Advocate®) was compared to injectable doramectin (Dectomax®). Dogs diagnosed with benign esophageal spirocercosis were divided randomly into doramectin (400 μg/kg IM) or moxidectin and imidacloprid spot-on (2.5–6.25 mg/kg and 10–25 mg/kg, respectively) groups and treated weekly for 12 consecutive weeks. Dogs were followed for 20 weeks by physical examination, owners’ questionnaire, blood work, fecal floatation, PCR and endoscopy.

Results

All the doramectin group dogs (n = 10) completed the treatment and follow-up, and the disease had completely resolved in all by week 12. Of the Advocate® group (n = 10), four had complete resolution at week 12, four had partial resolution, one dog did not respond to treatment, and one dog was switched to the doramectin protocol on week 5 due to persistent severe clinical signs. PCR analysis was more sensitive in detecting S. lupi eggs compared to fecal floatation. Discrepancies were detected on 22 occasions, of which on 20 occasions, the PCR was positive while fecal floatation was negative, and only on two occasions the PCR results were negative while fecal flotation was positive.

Conclusions

The present results indicate that weekly Advocate® spot-on administration may be effective for treating benign esophageal spirocercosis, but is less effective than the currently used injectable doramectin therapy at the dose and duration used herein.

Evaluation of the efficacy of monthly oral administration of afoxolaner plus milbemycin oxime (NexGard Spectra(®), Merial) in the prevention of adult Spirocerca lupi establishment in experimentally infected dogs

The nematode Spirocerca lupi (Rudolphi, 1809) is widely distributed but mostly occurs sporadically with stable populations only in certain geographic areas. This helminth mainly infects dogs and wild canids. Primary pathology relates to migration of third stage larvae (L3) damaging the thoracic aorta and establishment of adults in nodules in the oesophagus. The objective of the present study was to evaluate the efficacy of milbemycin oxime in combination with afoxolaner (NexGard Spectra(®), Merial), administered monthly, in preventing establishment of adult worms after experimental infection. Two groups consisting of eight animals each were experimentally infected with 15 L3 on Days -28, -14 and -2, respectively (45 L3 per animal in total). Group 1 dogs served as untreated (negative) control, whereas animals in group 2 were treated with NexGard Spectra(®) at a minimum dose of 0.5mg/kg milbemycin oxime on Day 0 and from then onwards every 28 days up to Day 140 (six treatment occasions). Endoscopy was performed on Day 112 and for some animals also Day 140. Necropsy for worm recovery and nodule/lesion scoring was performed on Day 168. All eight animals in the control group (group 1) presented with 1-3 nodules and worm counts ranging from 9 to 41. Six animals in the NexGard Spectra(®) group presented with 1-4 nodules and worm counts ranging from 1 to 5. Significantly (p<0.05) fewer worms were collected from treated animals in the treated group (geometric mean 1.7) versus the negative control group (geometric mean 22.0) with 92.3% efficacy calculated. There was no significant (p>0.05) difference between groups with reference to number of nodules in the oesophagus. However, nodules in the control group were significantly (p<0.05) larger than those in the treated group. Number and size of lesions in the dorsal aorta did not differ statistically between groups 1 and 2. Because NexGard Spectra(®) was administered 28 days after onset of inoculation, migrating and developing L3 caused damage to the aorta wall of animals in the treated group. Milbemycin oxime (administered as NexGard Spectra(®)) demonstrated effectiveness in reducing infection with adult Spirocerca lupi worms in the oesophagus.

Spirocercosis in dogs in Israel: A retrospective case-control study (2004-2009)

This case-control retrospective study (years 2004-2009) investigated the epidemiological, clinical, and diagnostic test findings of dogs with esophageal spirocercosis (ES) presented to the Hebrew University Veterinary Teaching Hospital (HUVTH) and coproscopy-positive dogs at the Kimron Veterinary Institute (KVI), Israel. It included 133 dogs with ES and 133 negative controls diagnosed at the hospital, and 343 dogs diagnosed at the KVI. The average incidence of ES at the HUVTH was 22.5/year, and the percentage of spirocercosis cases was stable at both institutions (HUVTH, 0.67-1.23%; KVI, 5-8%). Dogs aged > 5 years old had 100-fold likelihood to be infected compared to dogs aged ≤ 1 year of age (P < 0.001). Mean body weight (P = 0.0004), proportion of Retrievers (P = 0.002) and sporting breed dogs (P = 0.006) were higher, while proportion of toy breeds (P = 0.004) was lower in the ES group compared to the control group. The proportion of cases from Greater Tel-Aviv decreased (P = 0.002), while that of those from Judea and Jerusalem increased (P = 0.01) compared to the 1990 s. Spirocercosis occurred in 22 dogs despite past prophylactic avermectin treatment. Vomiting and regurgitation were the most common clinical signs of ES. Coproscopy was S. lupi-positive in 33/60 dogs (55.0%). The median number of esophageal nodules was two (range 1-8), with a median diameter of 3.5 cm (range 1.0-11.0). Malignant esophageal lesion transformation was confirmed in 29 dogs (22%). Despite preventive attempts, spirocercosis has spread in Israel over time, compared to previous findings, raising questions about the efficacy of the currently accepted prophylactic protocol is incompletely effective.

Spirocerca lupi infection in a dog from southern Italy: an "old fashioned" disease?

Canine spirocercosis caused by Spirocerca lupi is a life-threatening helminthic disease featured by severe clinical signs and potential development of oesophageal neoplasia. This infection is considered fairly frequent in Europe but almost unknown in Italy, from where only few reports have been published in local journals at the beginning of the XXI century. In the present study, an autochthonous case of canine spirocercosis in a 2-year-old dog from southern Italy is described. The animal was admitted to a private veterinary clinic in the municipality of Potenza (Basilicata region) due to persistent dyspnoea, vomiting, and regurgitation. At the abdominal ultrasound, a mass (1.3 × 2 cm) was observed and, thereafter, surgically removed from the apical part of the stomach. A female specimen of S. lupi was morphologically identified during the histological examination of the nodule and its eggs were detected in the faeces. In addition, the morphological identification was confirmed by molecular amplification and sequencing of partial cox2 gene sequence of S. lupi. Veterinarians should be aware of the potential risks derived from infection with this spirurid, which requires specific diagnostic and preventive measures.

Follow-up survey of the prevalence, diagnosis, clinical manifestations and treatment of Spirocerca lupi in South Africa

Spirocercosis is an important disease in South Africa. The object of this study was to determine if there had been a change in the prevalence, clinical manifestations and treatment of Spirocerca lupi over a 14-year period. A questionnaire was sent to 577 veterinary practices throughout South Africa in 2012. Of responders, 76% indicated that S. lupi occurred in their area, whilst 24% indicated that it did not; 84% considered S. lupi not to be a new phenomenon, whereas 16% considered it to be new. Monthly or seasonal distribution of the disease was not reported, and 76% of responders reported it to occur in no specific breed of dog, whereas 24% reported a breed risk, most considering large breeds to be at greater risk. No specific age or sex was identified as at higher risk. Common owner complaints were vomiting, weight loss, cough, or regurgitation. Reported clinical findings tended to mirror the clinical signs reported by owners. Most common diagnostic methods used were radiology, endoscopy, faecal flotation, and post mortem examination. Forty-four percent did not report seeing asymptomatic cases, 40% reported asymptomatic cases and 16% did not know. Associated complications were reported by 85% of responders, and included oesophageal neoplasia, hypertrophic osteopathy and acute haemothorax. Four different drugs were used as therapy: doramectin, ivermectin, milbemycin and Advocate®, with 9% of the responders using a combination of these four; 85% considered treatment to be effective and 15% ineffective. Treatment was considered more effective if the disease was diagnosed early and there were no complications. Two important conclusions were that more cases are being seen and that efficacy of therapy has increased, with a decrease in the mortality rate.