7,773 bytes removed ,  18:07, 25 August 2010
no edit summary
Line 203: Line 203:  
==Links==
 
==Links==
 
==References==
 
==References==
  −
  −
  −
  −
  −
  −
  −
==Heart Worm==
  −
  −
(Cardiology)
  −
===Description===
  −
  −
*Life cycle of [[Dirofilaria immitis|''dirofilaria immitis'']]
  −
  −
*Dogs, cats, and ferrets can be affected
  −
  −
*Cats are more resistant to infection compared to dogs, but it only takes one or two worms to cause serious disease in cats.
  −
  −
*Caval Syndrome is the result of extremely heavy worm burdens and is rarely seen.
  −
  −
  −
'''Infection with heart worm can affect the following structures:'''
  −
  −
'''1. Pulmonary arteries
  −
'''
  −
  −
e.g. pulmonary thromboembolism of dead worms
  −
  −
  −
'''2. Pulmonary parenchyma'''
  −
  −
e.g. allergic pneumonitis
  −
  −
  −
'''3. Heart'''
  −
  −
e.g. pulmonary thromboembolism-->pulmonary hypertension-->increased right ventricular afterload-->right ventricular hypertrophy-->myocardial failure-->right heart failure
  −
  −
  −
'''4. Liver
  −
'''
  −
  −
e.g. hepatic congestion from heart failure
  −
  −
  −
'''5. Kidneys'''
  −
  −
e.g. antigen-antibody complexes lead to glomerulonephropathies
  −
  −
  −
===Distribution===
  −
  −
*Endemic in the United States (especially southeast); South America, Southeast Asia, Middle East, Australia, Japan, Southern Europe
  −
  −
*Warm weather conditions that support the mosquito population contribute to heart worm disease
  −
  −
  −
====Transmission====
  −
  −
*Several types of mosquitoes are the intermediate host to the nematode worm D. imitis
  −
  −
*Mosquitoes are infected with D. imitis when they bite an infected animal with circulating microfilaria (L1 stage)
  −
  −
  −
===Signalment===
  −
  −
Genetics & Breed Predisposition: Large Breeds; Male>Female; 4-8 years old on average; Untreated with prophylactics
  −
  −
Cats: Outdoor cats; Male>Female; 3-6 years old on average; Untreated with prophylactics
  −
  −
  −
===Diagnosis===
  −
  −
====History & Clinical Signs====
  −
  −
-Asymptomatic +/- (Acute Infections)
  −
  −
-Symptomatic +/- (Chronic Infection)
  −
  −
-Exercise Intolerance
  −
  −
-Haemoptysis
  −
  −
-Coughing
  −
  −
-Tachypnea
  −
  −
-Syncope
  −
  −
-Right Heart Failure +/-
  −
  −
-Vomiting (cats)
  −
  −
-CNS signs (cats)
  −
  −
-Collapse (cats)
  −
  −
-Sudden Death (cats)
  −
  −
====Physical Exam====
  −
  −
-Signs of right sided heart failure
  −
  −
-Crackles heard on auscultation
  −
  −
-Splitting of the S2 heart sound signifies pulmonary hypertension
  −
  −
  −
====Staging Heartworm Disease====
  −
  −
{| style="width:75%; height:200px" border="1"
  −
  −
!'''Class'''
  −
!'''Description'''
  −
  −
|-
  −
| Class 1
  −
| No physical or clinical signs
  −
|-
  −
|Class 2
  −
| Mild cough, Slight radiographic changes
  −
|-
  −
|Class 3
  −
|Cough, Exercise intolerance, Dyspnoea, Abnormal lung sounds, Enlarged pulmonary artery, Signs of right heart failure 
  −
  −
|-
  −
|Class 4
  −
| Caval Syndrome; Signs of right heart failure, Abnormal lung sounds, Abnormal heart sounds, Death
  −
  −
|-
  −
|}
  −
  −
  −
  −
====Laboratory Findings====
  −
  −
'''Lab Tests'''
  −
  −
'''Heartworm Antigen Testing''' (dogs, cats)
  −
  −
-ELISA test kits test antigens associated with female D. immitis infections
  −
  −
-False negatives with male only infections (common in cats)
  −
  −
  −
'''Direct Blood Smear''' (dogs)
  −
  −
-Detects microfilaria from a blood sample
  −
  −
-Only works if the infection is very severe
  −
  −
-Not used on cats because after 6-8 weeks of a heart worm infection the microfilaria disappear.
  −
  −
  −
'''Modified Knott's Test or Filter Tests''' (dogs)
  −
  −
-These centrifugal concentration techniques detect small amounts of microfilaria from a direct blood smear
  −
  −
- (+) test indicates microfilaria production by adults
  −
  −
-(-) test indicates either no infection or an occult infection (immune system destroys L1)
  −
  −
-If negative test results, follow up with antigen test to rule out occult infections
  −
  −
-Not used on cats because after 6-8 weeks of a heart worm infection the microfilaria disappear.
  −
  −
  −
'''Antibody Testing''' (dogs, cats)
  −
  −
-(+) test only indicates exposure to D. immitis
  −
  −
-(-) test rules out D. immitis infection (useful in cats)
  −
  −
  −
'''Laboratory findings'''
  −
  −
Biochemistry: increased liver enzymes, azotemia, proteinuria, hypoalbuminemia
  −
  −
Haematology: eosinophilia, basophilia, thrombocytopenia, neutrophilia with left shift if the animal has a pulmonary thromboembolism, non-regenerative anaemia
  −
  −
  −
====Radiography====
  −
  −
-Enlarged right heart
  −
  −
-Dilation of main pulmonary artery
  −
  −
-Enlarged peripheral branches of pulmonary arteries (especially diaphragmatic lobes)
  −
  −
  −
====Electrocardiography (ECG)====
  −
  −
-Usually normal
  −
  −
-Right Ventricular Enlargement +/- (deep S waves)
  −
  −
-Right Atrial Enlargement +/- (tall P waves)
  −
  −
-Atrial arrhythmias +/-
  −
  −
  −
====Echocardiography====
  −
  −
-Right heart enlargement
  −
  −
-Dilation of the main pulmonary artery
  −
  −
-Visualization of D. immitis if the infection is severe
  −
  −
  −
===Treatment===
  −
  −
*Currently there are few treatment options for cats infected with heart worm except surgical removal in severe cases or the controversal use of thiacetarsamide.
  −
  −
*In dogs with allergic pneumonitis, give oral corticosteroids before starting heart worm treatment.
  −
  −
  −
====1. Adulticidal (kills worms slowly)====
  −
  −
e.g. melarsomine dihydrochloride, Thiacetarsamide
  −
  −
-Give two doses 24 hours apart or perform a graded-kill protocol (1 dose into epaxial muscles; repeat 1-3 months later; repeat 24 later)
  −
  −
-Rest animal for up to six weeks after treatment to avoid a thromboemolism (major treatment risk)
  −
  −
(If thromboembolism develops treat with: prednisolone, heparin, and oxygen)
  −
  −
-Perform an antigen test 3-6 months after treatment to ensure adult worms have been killed
  −
  −
  −
====2. Microfilaricidal (kills microfilaria)====
  −
  −
-Given about 4 weeks after adulticidal treatment
  −
  −
e.g. milbemycin, ivermectin
  −
  −
-Modified Knott's test should be performed 3 weeks after microfilaricide treatment.  If it is positive repeat microfilaricidal protocol.  If negative proceed to preventative treatment.
  −
  −
  −
====3. Prophylaxis====
  −
  −
-Test animals for heart worm before administering preventative treatment
  −
  −
-Give dogs a supply of monthly macrocyclic lactones
  −
  −
e.g. ivermectin, milbemycin, selamectin, moxidectin
  −
  −
-All year coverage is usually the best way to ensure owner compliance
  −
  −
  −
===Prognosis===
  −
  −
-Dependent on the stage at which heart worm has been diagnosed.
  −
  −
-Caval Syndrome has a 50% survival with surgical removal of the heart worms
  −
  −
  −
*Establish in '''heart''' and [[Lungs Circulatory - Pathology|pulmonary arteries]]
  −
*Larvae migrate through connective tissue
  −
*Immature adults move to caudal distal pulmonary arteries causing diffuse eosinophilic reaction in lung parenchyma, then migrate back to right ventricle
  −
*May cause [[Lungs Circulatory - Pathology#Embolism, thrombosis and infarction|pulmonary thromboembolism]]
  −
  −
==cat==
  −
  −
*As in dogs above
  −
*Not very infective in cats but one dead adult causes acute pulmonary crisis - [[Lungs Circulatory - Pathology#Embolism, thrombosis and infarction|thromboembolism]]
  −
== Nematodes of Dogs - CANINE HEARTWORM ==
  −
*''Dirofilaria immitis'' is one of the most important causes of morbidity and mortality in dogs in many regions of the world that have a warm, humid climate, including parts of southern Europe, USA and Australia.
  −
*The presenting signs are usually those of heart failure, but sudden collapse may occur in heavily infected dogs.
  −
*The endemic zone for canine heartworm disease is spreading as people increasingly travel with their pets.
  −
*Strains of ''D. immitis'' are adapting to cooler climates.
  −
*It is not endemic in the UK, but more infected dogs are likely to be imported now that the quarantine regulations have been relaxed.
  −
*It has a very long prepatent period, so clinical signs may not appear for many months after importation.
  −
*Although primarily a canine parasite, cats and ferrets can become infected.
  −
*Owners taking their pets into endemic regions require advice on how the disease can be prevented.
  −
'''In dog''':
  −
*larvae migrate through connective tissues and moult twice
  −
*immature adults (L5) are 1-5cm long → caudal distal pulmonary arteries in 4months → diffuse eosinophilic reaction in lung parenchyma, then migrate back towards right ventricle
  −
*start producing microfilariae 6-7months post-infection.
       
6,502

edits