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Dirofilaria worms produce microfilariae, not eggs.
 
Dirofilaria worms produce microfilariae, not eggs.
   −
==Signalment==
  −
  −
==Diagnosis==
  −
===Clinical Signs===
  −
  −
===Diagnostic Imaging===
  −
  −
===Laboratory Tests===
  −
  −
===Pathology===
   
'''Microfilariae''':
 
'''Microfilariae''':
 
*in peripheral circualtion
 
*in peripheral circualtion
Line 52: Line 42:  
*this usually happens when a radio-opaque plaque is detected in the lung, and further investigation shows it to be caused by a trapped ''D. immitis'' larva.
 
*this usually happens when a radio-opaque plaque is detected in the lung, and further investigation shows it to be caused by a trapped ''D. immitis'' larva.
   −
=== Pathology ===
+
 
 +
 
 +
=== Feline Heartworm Disease===
 +
 
 +
 
 +
*A canine parasite - see under Dog Nematodes for life-cycle etc.
 +
*Cats are abnormal hosts, and so ''D. immitis'' is not very infective for cats.
 +
*Nevertheless, feline infection is common (up to 25%) in some heavily endemic areas.
 +
*But only small numbers of adult worms (1-3) establish.
 +
*The prepatent period is longer (approximately 8months) than in the dog.
 +
*Few, if any, microfilariae are produced (<20% of cases positive).
 +
*The life-span of the worm is shorter (2-3years).
 +
*However: one dead adult → acute pulmonary crisis (thromboembolism).
 +
*Lung pathology similar to dog, but little heart pathology.
 +
*Coughing starts 4-6months post-infection.
 +
*Antibody-detection ELISA used for diagnosis, but false positives occur (antigen ELISA cannot be used as antigen rarely expressed in cats).
 +
*There is no licensed adulticidal therapy, and treatment may be fatal for the cat as well as the worm.
 +
*Ivermectin or selamectin can be used for prevention.
 +
 
 +
==Signalment==
 +
 
 +
==Diagnosis==
 +
 
 +
'''Diagnosis''':
 +
*Physical examination:
 +
**signs of heart disease
 +
**lung involvement
 +
*Radiography:
 +
**enlargement of right heart, main pulmonary arteries; arteries in lung lobes with thickening and tortuosity; inflammation in surrounding tissues
 +
*ECG:
 +
**right axis deviation → deep S waves
 +
*Echocardiography:
 +
**if post caval syndrome suspected - right ventricular enlargement with worms in ventricle appearing as parallel lines.
 +
 
 +
'''Clinical pathology''':
 +
*needed alongside physical examination and other tests to determine treatment strategy and prognosis.
 +
 
 +
'''Parasite detection''':
 +
*methods for demonstrating microfilariae in blood:
 +
**wet blood smear (okay for quick look, but insensitive) = ''D. immitis'' not progressively motile
 +
**Knott's test = red blood cells lysed; stained sediment examined
 +
**micropore filter = blood forced through; microfilariae held on filter; stained and examined
 +
**antibody detection ELISA = not reliable in dogs, but it is the best for cats (although some false positives)
 +
**antigen detection ELISA (using specific antigen from adult female worm) = reliable positives from 5-7months post-infection in dogs; although occasional false negatives occur → '''not''' useful for cats
 +
*the immunochromatographic test (ICT) uses coloured gold colloidal particles tagged to monoclonal antibodies to visualise the presence of adult worm antigen - performance similar to antigen detection ELISA, but quicker and easier to do (but not as quantitative as some ELISAs are)
 +
*operator error can give false positives, therefore best to confirm result with another test.
 +
 
 +
===Clinical Signs===
 +
'''Clinical signs''':
 +
*often sudden onset severe lethargy and weakness, but:
 +
*signs variable, reflecting multiple system dysfunction - pulmonary circulation, heart, liver and kidneys:
 +
**lung damage (severe pulmonary hypertension; thromboembolism)
 +
**heart failure (right-sided congestive)
 +
*therefore, '''not''' pathognomonic
 +
*acute prepatent = coughing
 +
*chronic = exercise intolerance, sometimes with ascites
 +
*acute post caval syndrome = collapse (dyspnoea, pale mucous membranes or jaundice, haemoglobinuria)
 +
 
 +
===Diagnostic Imaging===
 +
 
 +
===Laboratory Tests===
 +
 
 +
===Pathology===
 
'''Worms produce''':
 
'''Worms produce''':
 
*substances that are:
 
*substances that are:
Line 94: Line 146:  
*this is accompanied by increased red blood cell fragility, haemolytic anaemia and haemolobinuria.
 
*this is accompanied by increased red blood cell fragility, haemolytic anaemia and haemolobinuria.
   −
'''Clinical signs''':
+
==Treatment==
*often sudden onset severe lethargy and weakness, but:
  −
*signs variable, reflecting multiple system dysfunction - pulmonary circulation, heart, liver and kidneys:
  −
**lung damage (severe pulmonary hypertension; thromboembolism)
  −
**heart failure (right-sided congestive)
  −
*therefore, '''not''' pathognomonic
  −
*acute prepatent = coughing
  −
*chronic = exercise intolerance, sometimes with ascites
  −
*acute post caval syndrome = collapse (dyspnoea, pale mucous membranes or jaundice, haemoglobinuria)
  −
 
  −
'''Diagnosis''':
  −
*Physical examination:
  −
**signs of heart disease
  −
**lung involvement
  −
*Radiography:
  −
**enlargement of right heart, main pulmonary arteries; arteries in lung lobes with thickening and tortuosity; inflammation in surrounding tissues
  −
*ECG:
  −
**right axis deviation → deep S waves
  −
*Echocardiography:
  −
**if post caval syndrome suspected - right ventricular enlargement with worms in ventricle appearing as parallel lines.
  −
 
  −
'''Clinical pathology''':
  −
*needed alongside physical examination and other tests to determine treatment strategy and prognosis.
  −
 
  −
'''Parasite detection''':
  −
*methods for demonstrating microfilariae in blood:
  −
**wet blood smear (okay for quick look, but insensitive) = ''D. immitis'' not progressively motile
  −
**Knott's test = red blood cells lysed; stained sediment examined
  −
**micropore filter = blood forced through; microfilariae held on filter; stained and examined
  −
**antibody detection ELISA = not reliable in dogs, but it is the best for cats (although some false positives)
  −
**antigen detection ELISA (using specific antigen from adult female worm) = reliable positives from 5-7months post-infection in dogs; although occasional false negatives occur → '''not''' useful for cats
  −
*the immunochromatographic test (ICT) uses coloured gold colloidal particles tagged to monoclonal antibodies to visualise the presence of adult worm antigen - performance similar to antigen detection ELISA, but quicker and easier to do (but not as quantitative as some ELISAs are)
  −
*operator error can give false positives, therefore best to confirm result with another test.
  −
 
   
'''Chemotherapy''':
 
'''Chemotherapy''':
 
*three treatment objectives needing different approaches:
 
*three treatment objectives needing different approaches:
Line 180: Line 199:     
6) Check for adults (ELISA) 4-6months after adulticide, and before start of each subsequent mosquito season.
 
6) Check for adults (ELISA) 4-6months after adulticide, and before start of each subsequent mosquito season.
 +
 +
==Prognosis==
 +
==Links==
 +
==References==
 +
 +
      −
==Cat==
  −
*A canine parasite - see under Dog Nematodes for life-cycle etc.
  −
*Cats are abnormal hosts, and so ''D. immitis'' is not very infective for cats.
  −
*Nevertheless, feline infection is common (up to 25%) in some heavily endemic areas.
  −
*But only small numbers of adult worms (1-3) establish.
  −
*The prepatent period is longer (approximately 8months) than in the dog.
  −
*Few, if any, microfilariae are produced (<20% of cases positive).
  −
*The life-span of the worm is shorter (2-3years).
  −
*However: one dead adult → acute pulmonary crisis (thromboembolism).
        −
=== Feline Heartworm Disease ===
  −
*Lung pathology similar to dog, but little heart pathology.
  −
*Coughing starts 4-6months post-infection.
  −
*Antibody-detection ELISA used for diagnosis, but false positives occur (antigen ELISA cannot be used as antigen rarely expressed in cats).
  −
*There is no licensed adulticidal therapy, and treatment may be fatal for the cat as well as the worm.
  −
*Ivermectin or selamectin can be used for prevention.
      
==Heart Worm==  
 
==Heart Worm==  
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