Clinical presentation
A. vasorum infection has been associated with a range of clinical signs, some of which can be severe and life-threatening. Three main body systems can be affected: cardiorespiratory, coagulation and neurological. Signs may occur alone or in combination in a clinical case. Some dogs( frequently older dogs) may be infected but asymptomatic or have very vague, subtle clinical signs [ 6 ].
Cardiorespiratory signs
These are reported in approximately 45 – 60 % of cases and include:
• Cough
• Dyspnoea
• Tachypnoea
• Haemoptysis
• Syncope
• Pulmonary hypertension
Coagulopathic signs
• Bruising, petechiae, ecchymoses
• Subcutaneous haematoma
• Prolonged wound bleeding
• Haemoabdomen or other intracavitary blood loss
• Epistaxis
• Conjunctival haemorrhage
• Wound / incision bleeding following trauma / surgery
Initial hypotheses suggested that A. vasorum induced a disseminated intravascular coagulopathy-like syndrome, as many affected cases showed prolonged prothrombin time( PT) and / or activated partial thromboplastin time( APTT), along with mild to moderate thrombocytopenia and elevated levels of circulating D-dimers and fibrin degradation products [ 7 ]. However, research has since focused on clarifying the mechanisms underlying haemorrhage associated with A. vasorum, and it is now evident that other pathological processes are involved.
Techniques such as thromboelastography and rotational thromboelastometry have been used to characterise the coagulation profiles of dogs naturally infected with A. vasorum [ 8 ]. Thromboelastography is a rapid, wholeblood diagnostic test that measures how quickly and strongly the blood clots, assessing the entire clotting process( haemostasis) from start to finish, unlike previous standard tests( such as PT and APTT). Current understanding indicates that canine angiostrongylosis can disrupt haemostasis at multiple stages of the coagulation cascade, resulting in defects in primary and secondary haemostasis as well as disturbances of the fibrinolytic system, often referred to as tertiary haemostasis.
Neurological signs
Neurological signs are less frequently reported, with a review of previous studies reporting a 4 – 16 % occurrence [ 6 ]. Examples of clinical signs that may be seen are listed below; these signs may occur due to bleeding within the neurological system or, in rare cases, due to aberrant parasite migration:
• Paralysis / paresis
• Seizure activity
• Behavioural change, demeanour change
• Ataxia
• Circling
• Cranial nerve deficits
Other more diverse presentations are also described in the veterinary literature, demonstrating the variety of pathological effects A. vasorum can have in its hosts.
Other non-specific clinical signs
• Vomiting / diarrhoea
• Lethargy
• Inappetence
• Anorexia
Examples of unusual clinical signs
• Ocular signs such as larvae or adults in the anterior chamber
• Polyuria / polydipsia( PUPD)
• Gastric dilatation
• Exsanguination due to a ruptured femoral artery( in an experimentally infected dog)
• Hepatitis
• Dermatitis secondary to larva migrans
This lack of consistency in clinical presentation, and the vast array of diseases potentially responsible for similar clinical signs, can act as a barrier to diagnosis in veterinary practice.
Laboratory findings
A. vasorum infection is commonly associated with an eosinophilia( found in ~ 30 – 50 % of reported cases) and hyperglobulinaemia( found in up to ~ 75 % of reported cases) on routine blood testing [ 7 ]. Anaemia has been reported in approximately a third of all cases. It is usually regenerative in nature and is usually accounted for by blood loss. Hypercalcaemia has also been reported and is thought to be secondary to granuloma formation [ 9 ].
It is relatively common to see changes on thoracic radiography; most often an alveolar infiltrate is
22 Veterinary Nursing Journal