CArdiology Flashcards
Where in the USA is dirofilariasis predominantly found? Which geographic location particularly?
The southeast and mississipi river valley region
Outline the main lifecycle stages of dirofilariasis in the dog include timings.
At what stage can signs of HWD be seen?
- Adults live in the pulmonary artery where they can release microfilaraise into the circulation.
- Mf moult through L1 to L3 in the mosquito over 8 - 17 days. This is dependent on Wolbachia and temperature.
- In the dog the L3 larvae go to L4 then S5 in the SQT, adipose or skeletal muscle.
- S5 enter the circulation before setting up as adults
3 & 4 takes around 6 - 7 months.
HWD can be seen 2 - 3 months post infection when the S5 larvae enter the circulation. (so prior to ability to detect infection)
At what time of day and season are heartworm Mf released?
During the evening hours and summer months
Which lung lobes are most affected by heartworm proliferation? What is the histologic main mechanism of heartworm disease?
Myointimal proliferatoin of the vasculature is the histologic change. The caudal lung lobes seem to be most affected.
What are the main mechanisms contributing to development of PHT in canine heartworm disease.
- Release of vasoactive substances by heartworms
- Production of ET-1 by the vasculature
- Platelet activation
- Hypoxia
What are the main pathophysiologic consequences of canine HWD?
Vascular - resulting in PHT
PTE (often in response to worm death)
Glomerulonephritis (due to immune complex deposition)
Abherrent migration through other tissues
Eosinophilic lung disease
How can Mf from D. immitis be distinguished from D. reconditum?
- Number
- Motion
- Shape
- Length
What is the diagnostic approach to the detection of heartworm?
- Perform antigen test
- If positive then perform modified Knott test to look for Mf
a) If negagative then start a preventative, doxyclycline and melarsomine after 2 months
b) If positive then do as above but also clear microfilaraie prior to melarsomine - If negative then either this is a true negative but if clinical suspicion remains high then serum should be heat-treated.
What are the main radiographic features of canine HWD?
- Prominance of the main pulmonary artery
- RV hypertrophy
- Large pulmonary artery and tortous or pruned pulmonary artery
Which heartworm preventative is licenced for microfilarae?
Imidacloprid and moxidectin
What stage of the HW lifecycle is heart worm prevention most targeted at?
Mostly targets L3 - L4 moulting
Outline the adulticidal protocol for canine heart worm infection
What is caval syndrome?
A syndrome of cardiogenic shock resulting from heavy heartworm burden. Features:
1. Haemoglobinuria is the pathognomonic feature
2. Haeolytic anaemia
3. Cardiac arrythmias
What is the treatment of choice for heart-worm associated caval syndrome?
Removal of the worms from the pulmonary artery surgically.
What is the main difference between canine and feline heartworm consequences?
Feline heartworm infections are unccomon. Although they can get the more classical HWD like dogs this occurs uncommonly. Usually they get HARD which is characterised by the abscence of female worms.