Date Published: June 28, 2011
Publisher: BioMed Central
Author(s): Hanne Gredal, Jakob L Willesen, Henrik E Jensen, Ole L Nielsen, Annemarie T Kristensen, Jørgen Koch, Rikke K Kirk, Susanne E Pors, Geoff C Skerritt, Mette Berendt.
Four dogs with acute neurological signs caused by haemorrhages in the central nervous system were diagnosed with Angiostrongylus vasorum infection as the underlying aetiology. Two dogs presented with brain lesions, one dog with spinal cord lesions and one with lesions in both the brain and spinal cord. Only one dog presented with concurrent signs of classical pulmonary angiostrongylosis (respiratory distress, cough), and only two dogs displayed overt clinical signs of haemorrhages. Results of coagulation assays were inconsistent. Neurological signs reflected the site of pathology and included seizures, various cranial nerve deficits, vestibular signs, proprioceptive deficits, ataxia and paraplegia. One dog died and three were euthanised due to lack of improvement despite medical treatment. This emphasises canine angiostrongylosis as a potential cause of fatal lesions of the central nervous system and the importance of including A. vasorum as a differential diagnosis in young dogs with acute neurological signs in Denmark.
Angiostrongylus vasorum, also known as the French heartworm, is an approximately 13-21 millimetre gastropod-borne nematode, recognised in endemic areas of Europe [1-8], North and South America [9-12] and Uganda [13,14]. In endemic areas, the parasite is a well-known cause of respiratory disease (canine pulmonary angiostrongylosis, CPA) especially in young dogs which, along with other canine species, e.g. the fox, act as the definitive hosts in the life cycle of the parasite [1,3,15]. The adult worms primarily inhabit the pulmonary arteries and right cardiac ventricle of the canine host, resulting in a verminous pneumonia with obliterative thrombotic endarteritis and fibrosis . The primary clinical signs are reported to be cough, exercise intolerance, dyspnoea and right sided heart failure, all of which are directly related to the respiratory system. However, non-specific clinical signs such as vomiting, diarrhoea or anorexia are also frequently reported . Furthermore, disorders of haemostasis resulting in severe haemorrhages have been identified as possible complications of the CPA complex [3,15]. The exact pathophysiological mechanisms remain unclear [3,15], but a chronic low grade disseminated intravascular coagulation (DIC) with associated consumption of both platelets and coagulation factors is most commonly suggested [17,18]. Immunemediated thrombocytopenia associated with A. vasorum infections has also been reported as a possible cause of bleedings . Prolongation of clotting times and decrease of coagulation factors, e.g. von Willebrand factor and factor V have been reported in both experimentally and naturally infected animals, although not consistently [17,20,21].
All cases were seen at the small animal hospital, University of Copenhagen, Denmark. A summary of the clinical data and blood results can be appreciated from Additional file 1: Table S1 and Additional file 2: Table S2.
CPA is a commonly diagnosed disease in endemic areas of Denmark and the UK, primarily presenting as respiratory disease [3,15]. The included cases of the present study all presented with neurological signs as the primary complaint, in each patient caused by one or more CNS haemorrhages resulting from haemostatic dysfunction associated with A. vasorum and/or evidence of aberrant larvae. This emphasises CPA as an important differential diagnosis in dogs presenting with neurological signs of unknown aetiology. Acute non-traumatic brain haemorrhages are only infrequently reported in dogs , and A. vasorum should therefore be highly suspected as the underlying cause of brain haemorrhages in endemic areas. As opposed to ischaemic stroke, which appear with greater frequency and which might present with similar neurological signs, CPA is most commonly seen in young dogs [3,15], whereas the mean age of dogs reported with ischaemic stroke is 8.4-8.9 years [31,32]. The mean age of dogs in the present study was 10 months (median; 17 months) which is in accordance with previous studies of dogs naturally infected with A. vasorum [3,15]. The present study furthermore confirms haemorrhages due to A. vasorum to be an important differential diagnosis to acute disc disease and fibrocartilaginous embolisation in dogs with acute spinal cord disease in endemic areas as previously reported [23,33].
This report of four dogs infected with A. vasorum documents the importance of A. vasorum infection as a differential diagnosis, particularly in young dogs with acute neurological signs of unknown aetiology in Denmark. The identification of A. vasorum as the underlying cause of a primary presentation of neurological disease is complicated by the fact that dogs may display neither visible clinical signs of haemostatic dysfunction nor the classical respiratory signs of CPA.
Written informed consent was obtained from the owners for publication of this case report.
The authors declare that they have no competing interests.
HG headed the study, coordinated the collection of data of the four cases and was the main responsible for drafting the manuscript. JLW contributed with substantial information on all cases as well as participating in the design of the study and writing of introduction and discussion. ATK contributed with ideas for the study design and substantial information on haemostatic dysfunction in dogs with A. vasorum. JK contributed with data on all cases. HEJ, OLN, RKK and SEP performed post mortem examinations and histopathological investigations of all cases and drafted this part of the manuscript. GCS helped to draft the manuscript and contributed with background information on Angiostrongylosis in the UK. MB conducted the overall study, contributed with data on cases 1-4 and helped to draft the manuscript.