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| | ===Pathology=== | | ===Pathology=== |
| − | '''Worms produce''': | + | [[Image:dirofilariasis.jpg|right|thumb|125px|<small><center>'''Dirofilariasis'''. Courtesy of T. Scase</center></small>]] |
| − | *substances that are:
| + | [[Image:dirofilariasis 2.jpg|right|thumb|125px|<small><center>'''Dirofilariasis'''. Courtesy of T. Scase</center></small>]] |
| − | **antigenic
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| − | **immunomodulatory
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| − | **pharmacologically active.
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| − | '''Lesions are''':
| + | On post-mortem examination, the right side of the heart is found to be enlarged. There is proliferation of the pulmonary arterial myointima, as well as pulmonary thromboembolism and haemorrhage. If right-sided congestive heart failure was present in life, the hepatomegaly and hepatic congestion will be seen. |
| − | *'''not''' confined to the location of the worms
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| − | *also caused by shear stress of high blood flow.
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| − | | |
| − | '''Severity''':
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| − | *not associated with the number of worms
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| − | *exacerbated by exercise (i.e. by high blood flow rate)
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| − | *sedentary dogs often asymptomatic - symptoms most commonly associated with racing greyhounds.
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| − | | |
| − | '''Acute prepatent disease''':
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| − | *immature adult worms in caudal distal pulmonary arteries
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| − | *leads to intense diffuse eosinophilic reaction, which in turn leads to coughing.
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| − | | |
| − | '''Chronic disease''':
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| − | *mature worms in right heart and pulmonary arteries
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| − | *endothelial swelling and sloughing
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| − | *increased permeability → inflammation → periarteritis
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| − | *platelets/white blood cells activated → thrombosis
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| − | *proliferation of smooth muscle, thickening of media:
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| − | | |
| − | → impairment of blood flow
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| − | | |
| − | → pulmonary hypertension
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| − | | |
| − | → right ventricular strain
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| − | | |
| − | → right ventricular hypertrophy and right-sided heart failure
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| − | *insufficient blood pumped through pulmonary capillary bed → insufficient preload for left ventricle.
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| − | | |
| − | '''Post Caval Syndrome (Dirofilarial haemoglobinuria)''':
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| − | *can be acute or chronic
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| − | *heavy heartworm infestation:
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| − | **entangled clumps of worms → impaired closure of tricuspid valve → post-caval stagnation → hepatic congestion and hepatic failure
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| − | *this is accompanied by increased red blood cell fragility, haemolytic anaemia and haemolobinuria.
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| | ==Treatment== | | ==Treatment== |