Parasites of The Cardiovascular system Flashcards
What is microfilaria?
Non-digestive roundworm (heartworm)
How long is the average male and femal microfilaria respectively?
- Males are 15cm
- Females are 25cm
How long do microfilariae live for in dogs and how long are the dogs patent for?
- They can live for up to 7.5 years
- dogs can be patent for 5 years
What is Wolbachia endosymbiont?
- intracellular bacterium found in many filarial worms
- can have a mutalistic or symbiotic relationship
- Harboured by all stages of Dirofilaria immitis
- Required for fertility, survival & development of D. immitis
- Role in pathogenesis unclear
What is the primary host of dirofilariae?
Domestic Dog
What is the pre-patent period of dirofilariae?
6 months
At what point in the dirofilariae lifecycle are they infectious to other dogs?
L3 stage
Name three mosquitos that are important intermediate hosts of dirofilariae?
- Aedimorphus vexans
- Culex pipens pipiens
- stegomyria albopicta
What does dirofilariae pathology depend on?
- Number of worms
- infection duration
- host immune response
- Host activity (more active host= more strain on heart= more suffering)
- Dog size (smaller dog= smaller vessels= increased illness)
- dead worms cause a more severe reaction than live worms
What do adult dirofilariae worms do once released into pulmonary arteries?
- trauma and release of antigens
- irritation of arteries and stimulation of immune system
- endothelial damage, tunica intima, proliferation, perivascular cuffing
- vessel narrowing/ occlusion, reduced vascular compliance
- pulmonary hypertension
What is the long term sequelae of dirofilariae in pulmonary arteries?
- pulmonary hypertension and inflammatory mediators
- increase in pulmonary vessel permeability
- periarterial oedema, lung inflammation
- irreversible interstitial fibrosis and scarring
What does worm death cause?
in terms of blockage
pulmonary thromboembolism
What is vena caval syndrome?
Worms found in the right side of the heart and vena cava
* causes tricuspid valve problems and blood flow obstruction
* right-sided heart failure
Flow of red blood cells through worms -> haemolysis and haemoglobinaemia
What may a lighter difilaria infection look like in a dog?
- Asymptomatic
- Causes sustained exercise
What may a heavier difilaria infection look like in a dog?
- Loss of condition and exercise intolerance
- Chronic cough, shortness of breath
- Oedema and ascites
What are the clinical signs of vena caval syndrome in dogs?
- Haemoglobinuria
- Jaundice
- Collapse
- May be fatal
Why is there a strong inflammatory response in cat heartworm?
Most immature worms in pulmonary arteries die
* migration of worms to the CNS and other body cavities can occur
What are the clinical signs of heartworm associated respiratory disease in cats?
- Occurs 3 months post-infection
- dyspnoea, coughing, wheezing
- no adult worms are present
What are the clinical signs chronic feline heartworm disease?
- over 7 months post-infection
- respiratory signs, vomiting, neurological signs, pulmonary hypertension and heart failure, sudden death
- adult worms in pulmonary artery and heart
How may you diagnose feline heartworm disease?
- Geographical location
- Clinical signs
- Thoracic radiography
- Echocardiography
- routine lab testing ( anaemia, eosinophillia, proteinuria)
What are some more specific tests you can use for diagnosing worms in cats?
- Antigen testing- detect proteins from the reproductive tract of adult females
- Microfilariae in blood testing
- Antibody tests
What drugs can you use to prevent/ control dirofilariae?
- Chemoprophylaxis uses anthelmintics
- Larvicidal and interrupts reproductions (only kills of larvae and not adults)
- You can treat monthly from 2-3 months of age
- but does require testing before treating an older dog
How can you use vector control to prevent dirofilariae?
Should use routine use of mosquito repellents and insecticides on pets (any product with a 4+ week persistence)
In what countries is there potential chemoprophylaxis resistance?
- Well accepted in the US
- No strong evidence of resistance in Europe
- Continued surveillance is needed
