Magnetic resonance imaging findings of spinal intramedullary spirocercosis

Spirocerca lupi is a nematode infecting dogs in tropical and subtropical areas. Aberrant S. lupi migration to different body organs, including the spinal cord, has been documented. To date, the diagnosis of aberrant spinal cord migration was made at post-mortem examination or as an incidental finding, during spinal surgery. We describe two dogs with acute asymmetric paraparesis that were subsequently diagnosed with spinal cord spirocercosis. In magnetic resonance (MR) images of the spine, T2 hyperintense lesions were seen in the spinal cord of both dogs. The lesions appeared isointense on T1-weighted images and focal enhancement was detected after gadolinium administration. The MR imaging findings were compatible with focal inflammation, presumably along the parasite migration tract. Gross and microscopic pathologic findings confirmed the diagnosis of aberrant spinal intramedullary migration of S. lupi in one dog, and in the other dog, the clinical and imaging findings were supportive of this diagnosis.     

Spirocerca lupi isolated from gastric lesions in foxes (Vulpes vulpes) in Sicily (Italy)

Spirocerca lupi (Rudolphi 1809) is a cosmopolitan nematode of dogs and wild carnivores. In the past it has been reported in Italy, mainly in southern regions and in Sicily, where the parasite was observed in foxes in 2005. The parasite typically produces nodular masses in the oesophagus and thoracic aorta. During the 2003-2004 hunting season, the authors investigated a total of 55 foxes (Vulpes vulpes) hunted or killed by car accidents in the provinces of Palermo and Agrigento. All the foxes were subjected to necropsy and 6 (9.16%) had S. lupi nodules located exclusively in the gastric wall. The nature of the nodules was determined by opening them and detecting the nematodes inside, which were identified as S. lupi. Some of the nodules were characterized anatomopathologically and histopathologically. The formation of the parasitic nodule in the stomach only suggests a deviation from the route commonly followed by the nematode to reach the oesophagus, the elective anatomical site for completion of its lifecycle. This survey gives a contribution to the epidemiology of this parasite which is severely outdated in Italy and highlights some distinctive features of the life cycle and parasite migration.     

The efficacy of milbemycin oxime against pre-adult Spirocerca lupi in experimentally infected dogs

The aim of this investigation was to determine the efficacy of milbemycin oxime in preventing the oesophageal encapsulation of Spirocerca lupi, following the experimental infection of dogs. Two studies were conducted which involved a total of 21 purpose-bred Beagles. Each dog was infected with approximately 40, third stage infective S. lupi larvae. The larvae were dissected from scarabaeid beetles that had been collected from areas endemic for spirocercosis. In the first study, milbemycin oxime (minimum dose 0.5mg/kg body weight) was administered to seven dogs on day 30 post-infection. Seven other dogs served as untreated controls. In the second study, milbemycin oxime (also at a minimum dose of 0.5mg/kg body weight) was administered to four of seven infected dogs on day 28 post-infection. Treatment was repeated at 14- or 28-day intervals. All of the dogs, from both studies, were euthanized 168 or 169 days after infection. All S. lupi were recovered, and lesions in the thoracic aorta and oesophagus were described and quantified. A single treatment with milbemycin oxime was 79.8% effective in preventing the establishment of S. lupi in the oesophagus. This treatment significantly (p<0.05) reduced both the number of S. lupi within the oesophagus and the size of the oesophageal nodules. The efficacy of anthelmintic treatment was increased to 100% when repeat doses of milbemycin oxime were administered at 14- or 28-day intervals. These repeat treatments completely prevented the establishment of S. lupi within the oesophagus and thereby averted the development of oesophageal nodules. As expected, none of the treatment protocols reduced S. lupi related damage within the aorta because the administration of milbemycin oxime only began after the larvae had completed their first stage of migration.     

Nematode eggs observed in cytology of cerebrospinal fluid diagnostic for intramedullary Spirocerca lupi spinal cord migration

Spinal spirocercosis due to aberrant Spirocerca lupi nematode migration is an emerging etiology for acute myelitis in dogs in Israel, causing severe, mostly nonsymmetrical hind limb paresis or paralysis, and sometimes tetraparesis or tetraparalysis. So far, incidental identification of parasites during spinal surgery or at necropsy provides the only definite diagnosis, while antemortem diagnosis of this condition has been uncertain. Specifically, antemortem diagnosis is based on the typical clinical presentation of acute, progressive, asymmetrical hind limb paresis or paralysis, with moderate to severe eosinophilic to mixed cerebrospinal fluid (CSF) pleocytosis and increased CSF protein concentration. Exclusion of other differential diagnoses also requires using spinal cord imaging. In this novel report, we document a case of an intradural spinal spirocercosis in a dog, diagnosed antemortem, by detecting S lupi eggs in the CSF, and subsequent treatment, resulting in the resolution of the clinical signs.     

Chronic emesis caused by a nematode-induced gastric nodule in a cat.

A spirurid nematode-induced gastric nodule was believed to be responsible for chronic gastric irritation and vomiting in a domestic short-hair cat. Clinical improvement was noticed following surgical removal of the parasitic nodule in the wall of the pylorus. Morphologic characteristics of the parasite were most consistent with Spirocerca lupi. Infection with Spirocerca lupi is most commonly reported in Canids, often resulting in chronic granulomatous disease of the distal portion of the esophagus. In some animals, the lesions transform into fibrosarcomas and osteogenic sarcomas.     

Evaluation of doramectin for the treatment of experimental canine spirocercosis

The nematode Spirocerca lupi is primarily a parasite of dogs, which causes typical lesions of esophageal nodular granulomas, aortic aneurysms and spondylitis. In order to evaluate the therapeutic effect of doramectin on experimental canine spirocercosis, seven beagle dogs experimentally infected with 40 infectious S. lupi larvae (L(3)) were treated with doramectin. Treatment was commenced following endoscopic visualization of esophageal granulomas, and typical S. lupi eggs were detected in the feces. The treatment protocol included six treatments of doramectin (400 microg/kg subcutaneously) at 2 weeks intervals, followed by monthly injections until the disappearance of the esophageal granulomas or the end of the study (768 days post-inoculation).Eggs could not be found on fecal examinations 3-10 days after the first or second doramectin treatment. In addition, a gradual decrease in size of granulomas was noticed in all seven dogs during the course of the study. Esophageal granulomas had completely resolved in six of the seven dogs between day 35 and day 544 post-initial doramectin treatment, by day 35 in one dog (after three treatments), by day 43 in two dogs (after four treatments), by day 98 in one dog (after seven treatments), by day 460 in one dog (after 18 treatments) and by day 544 in another dog (after 21 treatments). In one dog, remnants of S. lupi granulomas could still be seen 544 days post-initiation of treatment with doramectin. Multiple subcutaneous injections of doramectin (400 microg/kg) were shown to be effective and safe in the treatment of canine spirocercosis.     

Copromicroscopic and molecular assays for the detection of cancer-causing parasitic nematode Spirocerca lupi

Spirocerca lupi (Nematoda, Spirurida) is a life-threatening parasitic nematode of dogs that is presently emerging in several countries. Nonetheless, canine spirocercosis is neglected and underestimated, mainly due to diagnostic limitations inherent to clinico-pathologic, diagnostic imaging and laboratory methodologies. Given the significant benefit of improved diagnosis, the present work evaluated the reliability of a recently described copromicroscopic approach, the FLOTAC technique, as well as a PCR-based assay with that of traditional coproscopic techniques to diagnose S. lupi infection. Ninety-four faecal field samples were collected from two endemic areas (i.e. 29 and 65 from Kenya and Israel, respectively) and processed using different coproscopic examination techniques. In particular, set I (Kenyan samples) comprised the modified flotation with Sheather's sugar solution and merthiolate-iodine-formalin technique, while set II (Israeli samples) comprised a flotation technique with zinc sulphate solution, a modified sugar flotation procedure and the FLOTAC method. All samples were also subjected to a semi-nested PCR protocol specific for a region internal to the mitochondrial cytochrome c oxidase subunit 1 gene of S. lupi. The coproscopic examinations showed low sensitivity and high variability, demonstrating the unreliability of the conventional methods for detecting S. lupi eggs. Nonetheless, the FLOTAC technique scored the highest number of positives and significantly higher number of S. lupi eggs per microscopic field compared to the other coproscopic methods. Additionally, of the coproscopically negative samples, 9 (45%) Kenyan and 21 (38.2%) Israeli samples scored molecularly positive using the PCR-based approach. The potential implications and perspectives for canine spirocercosis of these coproscopic and molecular diagnostic methodologies evaluated herein are discussed.     

Spirocercosis-associated pyothorax in dogs

The records of five dogs diagnosed with spirocercosis-associated pyothorax were retrospectively reviewed. On admission, the most common clinical findings were weakness, anorexia, depression, dyspnoea and fever. All dogs had typical oesophageal Spirocerca lupi granulomas. Contrast thoracic radiography revealed contrast material leakage from the oesophagus into the pleural cavity in two dogs only. All dogs were medically treated with broad-spectrum antibiotics, repeated chest tube drainage and thoracic lavage, and four of the dogs were treated with doramectin. One dog was euthanased due to a concurrent non-related disease at the owners request while the remaining four survived. S. lupi infection should be included in the differential diagnoses of canine pyothorax in endemic areas. Conservative medical management of pyothorax with antihelmintic medication was shown to be effective in the treatment of S. lupi-associated pyothorax.     

Further observations on canine spirocercosis in Kenya.

The close association of the parasite Spirocerca lupi with oesophageal sarcomas suggests aetiological involvement of S lupi. Further investigations may yield results of significance with respect to comparative oncology. This paper records detailed observations made over an 11 year period, on the incidence and pathological variations of S lupi infections in Kenya.     

Mitochondrial cytochrome c oxidase subunit 1 (cox1) gene sequence of Spirocerca lupi (Nematoda, Spirurida): avenues for potential implications

Canine spirocercosis is a life-threatening parasitosis caused by Spirocerca lupi (Nematoda, Spirurida) that is presently emerging in several countries. This study characterised an informative region within the mitochondrial (mtDNA) gene encoding for the cytochrome c oxidase subunit 1 (cox1) of S. lupi by Polymerase Chain Reaction (PCR)-coupled sequencing. Specimens from five different countries in Europe, Asia and Africa were examined and two different sequence variants of cox1 (i.e. haplotypes) were determined, displaying nucleotidic variation at 6 of 689 positions. All of these positions were invariable among all the parasite individuals from Europe (haplotype 1) and among the African and Asian individuals (haplotype 2), but differed between Europe and Asia/Africa. The S. lupi cox1 sequences were consistent with those of other common Spirurida previously reported at both nucleotidic and phylogenetic levels. This study provides molecular information essential for identification of the nematode, irrespective of its life cycle stage. Crucial implications for the specific molecular diagnosis of clinical spirocercosis and investigation of the evolution, population genetics, ecology and epidemiology of S. lupi are discussed.     

Spirocerca lupi infection in the dog: a review

Spirocercosis is a disease occurring predominantly in Canidae, caused by the nematode Spirocerca lupi. Typical clinical signs are regurgitation, vomiting and dyspnoea. The life-cycle involves an intermediate (coprophagous beetle) and a variety of paratenic hosts. Larvae follow a specific migratory route, penetrating the gastric mucosa of the host, migrating along arteries, maturing in the thoracic aorta before eventually moving to the caudal oesophagus. Here the worm lives in nodules and passes larvated eggs which can be detected using zinc sulphate faecal flotation. Histologically, the mature oesophageal nodule is composed mostly of actively dividing fibroblasts. Spirocerca lupi-associated oesophageal sarcomas may occur and damage to the aorta results in aneurysms. A pathognomonic lesion for spirocercosis is spondylitis of the thoracic vertebrae. Primary radiological lesions include an oesophageal mass, usually in the terminal oesophagus, spondylitis, and undulation of the aortic border. Contrast radiography and computed tomography are helpful additional emerging modalities. Oesophageal endoscopy has a greater diagnostic sensitivity than radiography. Endoscopic biopsies are not sensitive for detecting neoplastic transformation. Doramectin is the current drug of choice, effectively killing adult worms and decreasing egg shedding. Early diagnosis of infection is still a challenge and to date no ideal regimen for prophylaxis has been published.     

Gastrointestinal nematodes in dogs from Debre Zeit, Ethiopia

The study was conducted during the period between January 2005 and June 2006 to determine the frequency of gastrointestinal (GI) nematode infections of dogs in and around Debre Zeit, using qualitative and quantitative coprological (N = 100) and postmortem examinations (N = 20). By coproscopy 51% dogs were positive for different types of nematodal eggs, out of which 23.5% were with mixed infections. On necropsy 95% animals were found positive for adult parasites, of which 31.6% were showing more than one species of adult nematodes. The coproscopical examination revealed 32% infection with Ancylostoma caninum followed by Toxocara canis (21%), Spirocerca lupi (7%) and Trichuris vulpis (3%), while postmortem examination showed 70, 45, 23.5 and 5% infection, respectively. The study further indicated significant difference (P < 0.05) in overall frequency of GI nematode infections among different age groups but no difference (P > 0.05) between sexes.     

IMAGING DIAGNOSIS—SPINAL CORD CHONDROSARCOMA ASSOCIATED WITH SPIROCERCOSIS IN A DOG

A 7‐year‐old neutered female Boerboel cross was examined for progressive left pelvic limb lameness. There was no left patellar reflex but the remaining pelvic limb reflexes were hyperreflexic. Radiographically, there was a poorly mineralized opacity occupying the intervertebral foramen at L4–L5. On computed tomography images there was a hyperattenuating intramedullary lesion at L4–L5 that continued caudally, lateralized to the left and became extramedullary, terminating at L5–L6. In addition, well marginated, hyperattenuating lesions were noted at two muscular sites. The dog underwent euthanasia and a caudal esophageal mass was found at post mortem examination. The tumors in the spinal cord, the esophagus, and the skeletal muscles were diagnosed histologically as low‐grade chondrosarcoma undergoing endochondral ossification. Spirocerca lupi‐induced esophageal chondrosarcoma was believed to be the primary site from which the other, presumably metastatic, lesions originated.     

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

The purpose of this study was to evaluate the effect of a daily oral dose of doramectin in dogs with spirocercosis. Twenty naturally infected dogs were treated with 0.5 mg/kg doramectin administered orally once daily for 42 days. In 13 of the dogs there was resolution of the nodules after 42 days. Nodules were eliminated in five of the remaining seven dogs following treatment for an additional 42 days. In the remaining two dogs, treatment continued for a further 42 days (total 126 days), resulting in complete resolution. No adverse events associated with treatment were observed. This study concluded that doramectin at 0.5 mg/kg once a day is effective in the elimination of Spirocerca lupi nodules in dogs.     

Treatment of esophageal spirocercosis with milbemycin oxime

Six medium sized mixed breed dogs treated with milbemycin oxime (11.5mg on days 0, 7 and 28 and then monthly) stopped shedding Spirocerca lupi ova after 3-44 days. There was no evidence of subsequent shedding in repeated tests (about 5/dog) carried out from 31 to 133 days after initiation of treatment. Esophageal nodules disappeared in all dogs within 95-186 days and radiographic signs resolved within 85-127 days in the five dogs that were studied. This preliminary data shows milbemycin oxime deserves further evaluation for the treatment of spirocercosis.     

High within-host genetic variation of the nematode Spirocerca lupi in a high-density urban dog population

The nematode worm Spirocerca lupi has a cosmopolitan distribution and can cause the death of its final canid host, typically dogs. While its life cycle, which involves a coprophagous beetle intermediate host, a number of non-obligatory vertebrate paratenic hosts and a canid final host, is well understood, surprisingly little is known about its transmission dynamics and population genetic structure. Here we sequenced cox1 to quantify genetic variation and the factors that limit gene flow in a 300 km(2) area in South Africa. Three quarters of the genetic variation, was explained by differences between worms from the same host, whereas a quarter of the variation was explained by differences between worms from different hosts. With the help of a newly derived model we conclude that while the offspring from different infrapopulations mixes fairly frequently in new hosts, the level of admixture is not enough to homogenize the parasite populations among dogs. Small infrapopulation sizes along with clumped transmission may also result in members of infrapopulations being closely related.     

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

The nematode Spirocerca lupi is a parasite of dogs with beetles of several species serving as intermediate hosts. The medical records of 50 dogs diagnosed with spirocercosis at the Hebrew University Veterinary Teaching Hospital (HUVTH) in Israel during 1991-1999 were retrospectively reviewed and compared to a control group (n=100). There was a seven-fold increase in the annual number of dogs diagnosed with spirocercosis during these years while the hospital caseload increased by 80%, indicating an emerging outbreak of this infection. Dogs from the greater Tel Aviv area were at the highest risk of being diagnosed with spirocercosis with 74% of the cases originating from this region compared to only 17% of the controls. The disease appeared to have a primarily urban pattern of distribution with a significantly higher percentage (P=0.025) of dogs from cities versus rural areas, as compared to the control group. Sixty-two percent of the cases were diagnosed during the colder months of December through April. The median age of infected dogs was 5 years, with dogs 1 year old or younger at the lowest risk of being diagnosed with spirocercosis. Large breeds were at a higher risk of infection in comparison to small breeds and the Labrador Retriever was significantly over represented (P=0.027) in the study group compared to the control population. The most common signs were vomiting or regurgitation (60%), pyrexia (24%), weakness (22%), respiratory abnormalities (20%), anorexia (18%), melena (18%) and paraparesis (14%). A caudal esophageal mass was identified by radiography in 53% of the dogs and spondylitis of the thoracic vertebrae in 33%. Fecal flotation was positive for S. lupi eggs in 80% of the dogs, and endoscopy was found to be the most sensitive diagnostic procedure and allowed diagnosis in 100% of the examined dogs. Fifty-three percent of the dogs were anemic and creatine kinase (CK) activities were elevated in 54%. Necropsy of 14 dogs revealed esophageal or gastric granulomas in 13 dogs, and an esophageal osteosarcoma in a single animal. Aortic aneurysms were found in six (43%) dogs. Out of 24, 15 dogs (63%) for which follow-up information was available died or were euthanized within 1 month of admission. The case-fatality rate decreased toward the end of the study period when improved therapy with avermectins became available.     

Survey of the incidence, diagnosis, clinical manifestations and treatment of Spirocerca lupi in South Africa

A questionnaire survey of 716 veterinary practices was undertaken to determine the incidence of Spirocerca lupi in dogs in South Africa. In total, 49% of the questionnaires were returned, indicating a possible incidence of 28%. Fewer than 4 cases per year were recorded by 82% of the respondents; 4-12 by 14%; 12-24 by 3%; and more than 48 by only 1%. No seasonal incidence was reported by 48% of the respondents. Large breeds were considered to be at greater risk by 43% of respondents. No specific age or sex was identified to be at higher risk. The most common complaints by owners and clinical findings were vomiting (46%), weight loss (27%), coughing (21%) or regurgitation (20%), although 14% of respondents reported no abnormal clinical findings. Diagnostic methods used were radiology (74%), endoscopy (27%), post mortem examination (34%) and faecal flotation (4%). Complications associated with S. lupi were reported by 76% of respondents, which included oesophageal neoplasia (41%), hypertrophic osteopathy (38%) and acute haemothorax (30%). Specific treatments were used by 58% of the respondents, whereas 42% of the respondents either used no treatment (72%) or recommended euthanasia (28%). Of the treatment group, 52% used ivermectin, 27% doramectin, 13% other deworming drugs (benzimidazoles, nitroscanate), and 8% used disophenol. Sixty-three percent of the respondents considered their treatment ineffective, whereas 31% considered it effective, and 6% were unsure. The overall mortality rate was high.     

Silicate renal calculi in Kenyan dogs

Renal calculi were detected in 124 (53%) of 241 native Kenyan dogs during a necropsy survey for Spirocerca lupi infection. Affected kidneys were grossly normal but histologically pyelitis was present in 33% of the dogs. Over 50% of the stones were bilateral. Most were small and yellowish, the largest one was 2.5 cm. One native dog had a cystic calculus that obstructed its bladder.
Chemical analysis of the calculi revealed only traces of magnesium and phosphate. Emission spectrum studies identified the calculi as magnesium calcium aluminum silicate.
Decreased water intake or increased insensitive water loss do not seem to be important causative factors. Silica levels in water and maize should be determined.     

Helminths in dogs from a peri-urban resource-limited community in Free State Province,South Africa

This study focused on the helminth parasites of dogs in the Bloemfontein area of the Free State Province of South Africa. Samples were collected from 63 stray dogs destined for euthanasia. Complete sets of samples, consisting of blood, faeces, adhesive tape swabs and organs (heart, lungs and complete gastro-intestinal tract) from each dog were examined for helminth parasites. Dipylidium caninum was the most common helminth, and was recovered from 44% of dogs, followed by Taenia spp. (33%), Toxascaris leonina (32%), Ancylostoma caninum (27%), Toxocara canis (21%), Ancylostoma braziliense (19%), Spirocerca lupi (13%) and Joyeuxiella sp. (5%). Although human infection with S. lupi and Joyeuxiella sp. are unlikely, all the other helminths reported in this study are zoonotic, and therefore pose a threat to community health in Bloemfontein.