Angiostrongylus vasorum – more than a simple worm

If you don‘t think you‘re seeing cases of Angiostrongylus then they‘re seeing you! Angiostrongylus appears to be on the increase and so unless we start screening patients keeping a broad level of clinical suspicion then cases will be missed and treated inappropriately.

The IDEXX Angio Detect™ tests are a quick and convenient way of reaching a diagnosis. There is no problem with getting 9 negative results on patients so long as you pick up the 10th!

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Dave Tymms, Woodcroft Veterinary Group Ltd

6 cases you might have interpreted differently

Patient: A 2-year-old Dalmatian dog was presented with a history of respiratory distress and weight loss over the previous month and of unsuccessful therapy with ceftriaxone 50 mg/kg IM once a day for 2 weeks.

Findings: On admission the dog showed a mild dehydration and a severe dyspnoea. Haematology and blood biochemistry were within normal limits. Radiographic imaging of the thorax showed an interstitial pattern with no vascular lesions. Nodules of 2 – 7 mm of diameter in both lungs were visible at the pulmonary ultrasound examination (Fig. a). The cytological analysis

Patient: A 4-year-old, male Hanoverian Hound was presented in severe respiratory distress with acute onset of dyspnoea.

Findings: Haematological exam revealed a mild normocytic, nor- mochromic, nonregenerative anaemia in association with marked leucocytosis, marked absolute monocytosis, neu- trophilia and left shift. Platelet and eosinophil concentra-tions were within the reference limits. Given the severe clinical picture and the haematologic abnormalities of the dog, an infectious process, such as a bacterial pneumonia, or a lung injury were first suspected. Radiographic evaluation of the thorax showed a marked generalized unstructured interstitial pattern. No sign of pulmonary hypertension could be detected, while lung ultrasonography showed the presence of small scattered focal lesions in the pulmonary parenchyma and signs of hepatization of left caudal lung lobe.

What would have been your diagnosis?Six cases demonstrating the different clinical signs Angiostrongylus can cause

CASE 11

of the nodules revealed the presence of macrophages, some of them showing erythrophagocytosis, and inflam-matory cells (Fig. b).

Diagnosis: Overall, these findings were considered compatible with a pulmonary malignant disseminated neoplasia. A routine copromicroscopic examination (i.e. flotation and Baermann’s test) showed the presence of several larvae of A. vasorum.

Treatment: The dog was treated with three doses of a spot-on solution containing imidacloprid 10%/moxidectin 2.5 % (Advocate®, Bayer Animal Health) 15 days apart. In fact, after the first anthelmintic treatment the clinical status of the dog im- proved quickly, despite few A. vasorum L1s being shed in the faeces. Therefore, the dog received two further ad- ministrations of moxidectin.

Outcome: Forty-five days from the first treatment, the faeces were negative for A. vasorum, coughing and dyspnoea were absent, no nodular lesion could be revealed upon lung ultrasonographic examination and the thoracic radio- graphs were markedly improved.

Diagnosis: Diagnostic imaging lesions were suspect for a lungworm infection and specific tests for A. vasorum were performed. Evaluation of a direct fresh fecal smear revealed nume- rous nematode larvae morphologically compatible with A. vasorum. The infection was further confirmed by a positive antigenic test (IDEXX Angio Detect™).

Treatment: After diagnosis the dog was immediately treated with a spot-on solution containing imidacloprid 10 %/moxidectin 2.5 % (Advocate®, Bayer Animal Health) in association with glucocorticoids and specific support therapy.

Outcome: The dog died six hours after therapy administration in a severely dyspneic state with profuse hemoptysis. Baer-mann’s test confirmed A. vasorum infection the day after.

Fig. bFig. a

CASE 21

Patient: A 6 month-old female Akita Inu was referred with a history of inappetence and chronic haemorrhages.

Findings: Clinical examination revealed several foci of conjunctival haemorrhages, skin ecchymoses and petechiae, with no other clinical abnormality.Therefore, the top differential was anticoagulant roden- ticide poisoning. Nonetheless, this suspicion was immediately discarded after tests revealed normal values for prothrombin time (PT) and activated partial thromboplastin time (aPTT). A complete blood count revealed a mild normocytic, hypochromic, non-regenerative anaemia in association with moderate absolute monocytosis, moderate absolute eosinophilia and a severe thrombocytopenia, which was identified as the cause of the primary haemostatic disorder of this patient. Radiographic examination of the thorax revealed a generalized unstructured interstitial to alveolar pattern compatible with lung haemorrhage or acute respiratory distress syndrome, which was considered the most probable differential due to the haemostatic disturbance of the dog. No evidence of cardiomegaly was detected

radiographically. Therefore, an inherited, infective or immune-mediated cause of thrombocytopenia was suspected. Nonetheless, no predisposition for low platelet concentration is recognized in the Akita Inu breed and specific tests for common infective or parasitic causes of thrombocytopenia (i.e. Ehrlichia canis, Anaplasma platys, Anaplasma phagocytophilum, Babesia spp.) were negative.

Diagnosis: The dog was then tested for A. vasorum, despite no re-cords of this parasite existing in the region. The dog tested positive with the IDEXX Angio Detect™ Test and this finding was confirmed by a positive Baermann test for A. vasorum. The dog was also positive at an antiplatelet antibody test.

Treatment: The dog was treated with fenbendazole 50 mg/kg sid for two weeks and tested negative by Baermann’s test two weeks after the end of the therapy. Suggested immuno-suppressive approach was declined by the owner.

CASE 41

Patient: Staffordshire Bull Terrier „Jimmy“ suffered a traumatic fracture of his upper right 4th premolar (carnassial) tooth, necessitating extraction. However, the tooth socket persistently haemorrhaged and he became anaemic (PCV 12%) and lethargic (nb: no respiratory signs).

Diagnosis: He was diagnosed with Angiostrongylus vasorum infection via the IDEXX Angio Detect™ test.

CASE 32

Treatment: He required two units of fresh frozen plasma to replace clotting factors and stop the bleeding and a unit of packed red blood cells to treat the anaemia as well as treatment with Advocate® topically and a 10 day course of fenbendazole orally.

Outcome: He went on to make a full recovery!

Patient: A 9-month-old male bulldog was presented to a veterinary hospital with a history of sudden weakness, inappetance, blood in the faeces, and mild signs of respiratory disease, especially cough.

Findings: Clinical examination was unremarkable except for a slightly increased respiratory rate and occasional abdo- minal breathing when the dog was in distress. The owners reported the presence of rodenticide baits nearby the house where the dog lived. Given the young age of the dog blood biochemistry showed a moderate increase in urea and total bilirubin suggestive of chronic haemorrhage. Haematology examination revealed regenerative normocytic normo- chromic moderate anaemia with a decrease in the platelet count, confirmed by blood smear, and moderate leuko- cytosis with absolute neutrophilia and monocytosis. Coagulation profile revealed a moderate increase of the prothrombin time and a marked decrease of fibrinogen concentration. Rx examination showed a diffuse alveolar- interstitial pattern of the lung parenchyma.Given the history and clinical findings a rodenticide in- toxication with secondary pulmonary haemorrhage was considered the main differential diagnosis. The dog was treated with antibiotics, anti-inflammatory drugs and vitamin K, but despite an initial clinical improvement, respiratory signs and weakness recurred in a few days.

Patient: A 7-month-old female cross breed was presented with a history of anxiety, vocalizations, laboured breathing of one day duration and an acute onset of paraplegia.

Findings: Clinical examination revealed several neurologic deficits at the posterior limbs. Given the young age of the dog, the differential diagnoses included discospondylitis, myelitis or a compressive cause, with the former as the most likely diagnosis. Blood biochemistry and PT were in normal ranges and aPTT was slightly higher than the upper reference limits. Computed tomography (CT) of the vertebral column revealed an endocanalar hyperattenuating enhancing material with multifocal extra-dural distribution in the thoraco-lumbar tract compressing the spinal cord. Moreover a diffuse interstitial lung pattern with enlarged and tortuous pulmonary arteries was seen.

Diagnosis: Despite first clinical suspects, diagnostic imaging findings made the clinician suspicious of A.vasorum infection as the cause of the lung lesion and pulmonary hypertension, therefore a rapid antigenic test (IDEXX Angio Detect™) for A.vasorum was performed giving a positive result. The

CASE 63

CASE 51 endocanalar multifocal material seen in CT images was

interpreted as haemorrhages or granulomatous lesions caused by larval dissemination of the lungworm. The in-fection was further confirmed positive by Baermann’s test.

Treatment: The dog was treated with fenbendazole 50 mg/kg sid for two weeks and tested negative for Baermann’s test two weeks after the end of the therapy.

Outcome: After the specific antiparasitic and support therapy, the dog showed a dramatic clinical improvement.

Diagnosis: The recurrence of clinical symptoms after specific therapy of rodenticide intoxication made the practitioners consider a different diagnosis. The young age of the dog, imaging findings and thrombocytopenia made the clinician suspi- cious of A. vasorum infection. The infection was confirmed by the identification of L1 larvae of A. vasorum in a fresh fecal smear and further confirmed by a positive Baermann test.

Treatment: The dog was treated with a spot-on solution containing imidacloprid 10 %/moxidectin 2.5 % (Advocate®, Bayer Animal Health) in association with glucocorticoids. The treatment was repeated after 2 weeks. The dog tested negative for the Baermann test three weeks after the first administration of the therapy. A negative antigen test (IDEXX Angio Detect™) at 8 weeks after the first adminis- tration of the therapy confirmed the efficacy of the treat- ment.

Outcome: After the specific antiparasitic therapy, the clinical picture of the dog improved dramatically and respiratory signs disappeared within a few weeks.

CT transverse image of the thoracic spine. A endocanalar space-occupying hyperattenuating material (arrow) is seen and compressing the spinal cord.

· Respiratory/cardiovascular symptoms: dyspnoea, pulmonary hypertension, coughing, exercise intolerance, heart failure

· Bleeding disorders: haemorrhage (e.g. non healing wounds, increased post-surgery bleeding, red sclera, subcutaneous haematoma/ecchymosis, haemoabdomen, haemarthrosis, haematuria, epistaxis), anaemia, melaena

· Neurological symptoms: e.g. hind leg lameness, lameness, stiff gait, imbalance

· Other: lethargy, anorexia, weight loss, vomiting, diarrhoea

Clinical signs that can be caused by Angiostrongylus vasorum:

Don´t lose time! Unlike other lungworm infections, canine Angiostrongylosis can be fatal and should be treated like an emergency. In endemic areas, you should consider testing for subclinical angiostrongylosis before surgery.

- Pet-side blood test with reliable results within 15 min – directly in your clinic- No faecal sample collection required- High sensitivity and specificity – more sensitive and less expensive than PCR,

comparable to the Baermann-method, plus faster and easier - In endemic areas, pre-surgery testing can be useful- Can be used for treatment monitoring- Storage at room temperature and long shelf life

- Exclusively at IDEXX

· Angiostrongylus vasorum is spreading with reported cases on the rise in many parts of [country xy/Europe].

· Bleeding disorders, lameness, neurologic symptoms, exercise intolerance, dyspnea - the various clinical signs are often non-specific and not associated with Angiostrongylus; therefore, it might be missing on the differential list.

· Canine Angiostrongylosis is a serious disease with fatal consequences in severe cases.

· Diagnosing and treatment can easily be done directly in your clinic!

The IDEXX Angio Detect™ Test

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Clinical Guidance on Angiostrongylosis

1 Cases used by courtesy of Angela Di Cesare, Donato Traversa, Simone Manzocchi, Silvana Meloni, Eleonora Grillotti, Edoardo Auriemma, Fabrizio Pampurini, Cecilia Garofani, Fabrizio Ibba and Luigi Venco; Elusive Angiostrongylus vasorum infections, Parasites & Vectors (2015) 8:438

2 Case used by courtesy of David Tymms, Woodcroft Veterinary Group Ltd3 Case used by courtesy of S. Manzocchi, Clinica Città di Pavia, Italy.

Dog with suspected anglostronglyosis

The symptoms are numerous, varied and non-specific. They include:· Cough and other respiratory signs· Lethargy, exercise tolerance, 'under the weather‘· Prolonged or excessive bleeding

Angostronglyosis may remain subclinical for months to years and should be considered before surgery.

Test with the IDEXX Angio Detect™ Test

Positive Negative

Antigen detected indicating current infected with A. vasorum

· Initiate treatment for angiostrongylosis; e.g., imidacloprid and moxidectin (Bayer Advocate®); two doses, 30 days apart for clearance of the parasite.

· Avoid surgery until the dog is free of the parasite.· Reinfection is possible and likely in dogs with a

propensity to eat slugs and snails. Discuss ongoing prevention with the pet owner.

· Other dogs in the same household are at particular risk of infection.

· Discuss ongoing prevention of A. vasorum with the pet owner.

· If the dog was coughing, consider Crenosoma vulpis and submit a faecal sample for the Baermann technique.

· For lethargy, exercise intolerance, consider cardiac and other respiratory causes.

· For prolonged or excessive bleeding, consider rodenticide intoxication, platelet concentration and function, inherited coagulopathies and others.

Antigen not detected; current infection with A. vasorum highly unlikely