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Module 10 > Infectious Aetiologies of Heart (lungworms & heartworms) > Flashcards

Infectious Aetiologies of Heart (lungworms & heartworms) Flashcards

1
Q

what is Dirofilaria immitis

A

a nematode (roundworm) parasite

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2
Q

what is the final host of D. immitis

A

dog, wild dog, cat, ferret, sea lion (man accidental FH)

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3
Q

what is the intermediate host of D. immitis

A

mosquito

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4
Q

where is the site of infection in D. immitis

A

right ventricle, posterior vena cava, pulmonary artery

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5
Q

where is D. immitis distributed

A

USA, warm temperate zones (Europe), tropics

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6
Q

what is the life cycle of D. immitis

A
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7
Q

what is the pathogenesis of D. immitis in dogs (4)

A

depends on worm burden (low numbers can be little apparent ill effect, high numbers lots of problems)

pathology associated with adults in heart

impede blood flow –> chronic congested right-sided heart failure

  1. pulmonary embolism (adults blocking vessels, important if treat to kill adult worms)
  2. vena cava syndrome (fatal 24-48hrs)
  3. endocarditis in valves, pulmonary endarteritis (local inflammatory response)
  4. glomerulonephritis (deposition of immune complexes in kidney)
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8
Q

what are the clinical signs of D. immitis (4)

A
  1. cardiovascular dysfunction
  2. listless/gradual loss of condition
  3. exercise intolerance
  4. chronic soft cough
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9
Q

how is D. immitis diagnosed

A
  1. clinical signs and history
  2. radiographs, echocardiograph
  3. detection of mf in blood (wet film, stain dry blood film)
  4. detection of circulating antigen (ELISA)
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10
Q

how is D. immitis diagnosed using antigen tests

A

can detect a single female but not a male worm (antigen is secreted by adult worm)

start testing by 6-7 months of age (PPP ~6 months)

more sensitive than mf detection –> esp. if animal on prophylaxis

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11
Q

what are occult infections

A

adults but no mf

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12
Q

why is it recommended to do both mf test and antigen test

A

some dogs have occult infections while some dogs have mf but no Ag

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13
Q

what are factors affecting epidemiology of D. immitis in dogs

A
  1. density of dogs
  2. number of strays
  3. mf can be present for long periods
  4. poor immunity
  5. poor owner compliance for prophylaxis
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14
Q

what are the epidemiological factors that affect D. immitis in mosquitos (4)

A
  1. distribution + spread of susceptible vectors (environmental change/urban heat islands, intro/spread of new vector species, capacity for rapid population increases)
  2. short developmental period mf-L3, 10-14 days (temp dependent development –> stop developing if <14 degrees)
  3. some mosquitos can survive for months
  4. infection rates can vary 2-19% (but can be much higher in vinicity of infected dogs)
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15
Q

how is D. immitis controlled

A

prophylaxis is basis of control

tropics: treat all year round

temperate zones with mosquito season: treat 1 month before to at least 2 months after

recommended to treat year round –> better compliance

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16
Q

how is D. immitis prophylactically controlled

A
  1. macrocyclic lactones (ex. ivermectin/milbemycin - orally or selamectin/moxidectin topically) monthly
    - kill L3 and L4 up to 6 weeks p.i
  2. DEC (diethylcarbamazine) daily

prophylactic drugs don’t kill adult worms –> but MLs may have sterilizing effect on female worms

17
Q

what can occur when treating D. immitis infected dogs

A

must check mf status of dog

ivermectin and DEC also kill mf –> if mf + can induce anaphylactic shock

ideally dogs should be mf - pre treatment

18
Q

what does prophylaxis treatment target in D. immitis

A

L3/L4

19
Q

how else can D. immitis be prevented

A
  1. keep animals indoors at peak mosquito biting times (dusk)
  2. insecticide collars
  3. attempt to reduce mosquito population
20
Q

what are the principles of treating D. immitis infected dogs

A
  1. improve clinical condition
  2. eliminate all stages of worm
  3. minimize post-treatment complications
21
Q

what is wolbachia and why is it significant in D. immitis

A

D. immitis harbours a bacterial endosymbiont wolbachia

killing wolbachia with doxycycline sterilizes female –> eventual death of adult worm

combo of IVM and doxycycline kills adults

22
Q

what are the current treatment recommendations in D. immitis

A

combo treatment with ML and doxycycline prior to adulticidal therapy (moxy-doxy) –> ML clears Mf and prevents new infections, dox reduces pathology associated with dead adults, shrinks worm mass

followed by melarsomine (immiticide) to kill adult worms

23
Q

what occurs in D. immitis infections in cats

A

not well adapted –> very pathogenic

adult worms live for shorter period compared to dog

mf transient in blood

24
Q

what are the differences in dog and cat D. immitis infections

A
25
Q

how is D. immitis treated in cats

A

pathology is assocaited with the inflammatory response to worms/worm death and not from biomass of adults (as in dogs)

if no clinical signs –> can allow spontaneous recovery with monitoring

melarsomine very toxic in cats

chemoprophylaxis using ML compounds

26
Q

what is the host, IMH and site of infection in Angiostrongylus vasorum

A

host: dog, fox

IMH: molluscs

site: right ventricle, pulmonary artery

27
Q

what is the life cycle of A. vasorum

A
28
Q

what is the pathogensis of A. vasorum

A

chronic infection

pathology associated with adults in large vessels and eggs in pulmonary capillaries

chronic congestive cardiac failure

fibrosis in arteries

lung mottled, penetrating L1

bleeding

29
Q

what are the clinical signs of A. vasorum

A
  1. early on –> asymptomatic
  2. later –> increased resp. rate/cough on exercise
  3. heavy worm burded –> symptoms in resting dogs (fainting, s.c hematoma)
  4. can be associated with brain and spinal cord hemorrhage
  5. sub-cutaneous hematomas
  6. parasite excretory/secretory products interfere with blood clotting (can be confused with warfarin poisoning)
30
Q

how is A. vasorum diagnosed

A
  1. Baermann on fecal sample –> should sample on 3 days to ensure detection, L1 characteristic tail with small spine
  2. PCR
  3. AG test –> detects antigen in the blood stream

Module 10 (27 decks)

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