Heart & Lung Worms In Dogs & Cats

Front 1

What are the shared characteristics of species within the FILARIOIDEA superfamily?

Back 1

- Tissue dwelling

- Intermediate hosts (IMH) - insect vectors

- Primitive forms release eggs

- More highly evolved release live L1 or microfilariae (Mf)

- Mf show periodicity in the blood - may have to take several blood tests to get accurate detection

Front 2

What are the hosts for dirofilaria immitis (heartworm)?

Back 2

Dogs

Cats

Ferrets

Sea lions

(man)

Front 3

What is the intermediate host (IMH) for dirofilaria immitis?

Back 3

MOSQUITO

Front 4

What is the predilection site for dirofilaria immitis?

Back 4

CARDIOVASCULAR SYSTEM

- Adult worms may inhabit the right ventricle, posterior vena cava, & pulmonary artery

Front 5

What is the normal distribution of dirofilarial immitis?

Back 5

USA, warm temperate zones (Europe), tropics

Front 6

Describe the life cycle of the dirofilaria immitis.

Back 6

- Infective microfilaria (L1) released into blood

- Mf ingested by mosquito, where L1 moults to L3 within 10-14 days

- L3 are then transmitted by feeding mosquito to host

- L3-L4 adults develop in subcutaneous tissue

- Juvenile adults migrate to heart, where they becoming fully-formed, reproducing adults that release Mf into the blood & perpetuate the cycle.

Front 7

What is the post-partent period for dirofilaria immitis?

Back 7

6 months = sexually mature & releasing L1 eggs into blood

Front 8

Pathogenesis of dirofilaria immitis?

Back 8

* Dependent on worm burden; low numbers may show no clinical signs*

- Chronic congested right-sided heart failure; associated with adult worms in heart

- Pulmonary embolism = adults blocking vessels

- Vena cava syndrome = worms in vessels cause collapse

- Endocarditis in valves & pulmonary endarteritis (local inflammatory response)

- Glomerulonephritis = deposition of immune complexes in kidney

Front 9

What are the clinical signs of dirofilaria immitis?

Back 9

1. Cardiovascular dysfunction

2. Gradual loss of condition

3. Exercise intolerance

4. Chronic soft cough

Front 10

Diagnosis of dirofilaria immitis?

Back 10

1. Detection of microfilaria in blood, via:

- Wet film

- Stain dry blood film

2. Circulating antigen test (SNAP test) = detect mature females (start testing at 6-7 months = PPP); more sensitive than Mf detection, but best to use both Ag & Mf tests because ~7% dogs have Mf, but no Ag.

3. Observation of clinical signs & history

Front 11

A dog must be at least _____ months old to be antigen tested. Why is it best to use both Mf & Ag testing when diagnosing dirofilaria immitis?

Back 11

6-7 months = because PPP ~6 months

Both tests used because although antigen tests are typically more sensitive then Mf tests, sometimes dogs can have Mf, but no Ag yet.

Front 12

What are the factors effecting epidemiology of dirofilaria immitis?

Back 12

1. The Dog (host)

- Density

- Mf present for long periods

- Poor immunity

- Poor owner compliance

2. Mosquito

- Distribution of susceptible vectors

- Short developmental period Mf-L3

Front 13

Control of dirofilaria immitis?

Back 13

Much easier to control then to treat!

- Parasite/vector control

- Prophylaxis (year round in tropics, during mosquito season in temperate zones)

Front 14

Describe prophylactic use for dirofilaria immitis.

Back 14

FIRST, check Mf status of dog because if Mf+, treatment could induce anaphylactic shock.

MACROCYCLIC LACTONES used monthly

(e.g. Ivermectin, milbemycin, selamectin)

- Don't kill adult worms once migrated to the heart.

- Induce sterilizing effects on female worms..

Front 15

In endemic areas, puppies should be on prophylaxis by _______ of age.

Back 15

8 weeks!

Front 16

What are other preventative measures for dirofilaria immitis, aside from prophylaxis treatments?

Back 16

- Keeping animals indoors at peak mosquito biting times (dusk)

- Insecticide collars/spot-on

- Attempt to reduce mosquito population (difficult)

Front 17

Treatments for dirofilaria immitis?

Back 17

1. Surgical removal of adult worms in specialized clinics.

2. Intravenous Melarsomine (arsenic compound) treatment = kills Mf

3. Doxycycline - kills bacterial endosymbiont, Wolbachia

* IVM & Doxy often given as combo therapy

* Beware killing off the adult worms in animals with large amount because they could clog the heart.

Front 18

Many species of filarial worm harbor a bacterial endosymbiont - ________________.

Back 18

WOLBACHIA

* Killing with doxycycline results in eventual death of adult worms.

* Combo therapy of IVM & doxycycline appear to kill adult dirofilaria immitis.

Front 19

Dirofilaria immitis is not well adapted in cats.

True or False?

Back 19

TRUE - Only 5-15% prevalence of that in dogs

- Very pathogenic

- Adult worms live for shorter period (2-3 years) compared to dogs

- Mf transient (short-lived)

Front 20

Compare dog and cat infection with dirofilaria immitis:

Back 20

In cats:

- Reduced susceptibility

- Adult worms live shorter lives (2-3 years)

- Usually <6 adults (30+ in dogs)

- Transient Mf (persistent in dogs)

- Lungs most affected (Heart & lungs in dogs)

- Complex diagnosis that tests for Ab

- No approved treatment for adults

Front 21

If no clinical signs present with dirofilaria immitis in cats, you can allow spontaneous recovery, with monitoring.

True or False?

Back 21

TRUE

Front 22

What are the shared general characteristics of the METASTRONGYLE superfamily?

Back 22

1. Indirect life cycles

2. Clinically mild/asymptomatic

3. IMH = mollusks

Exceptions:

- Metastrongylus (pig) = earthworm IMH

- Oslerus osleri = direct life cycle, increased pathogenicity

Front 23

Hosts for angiostrongylus vasorum ("french heartworm")?

Back 23

DOG & FOX

Front 24

IMH for angiostrongylus vasorum?

Back 24

MOLLUSKS

Front 25

Predilection site for angiostrongylus vasorum?

Back 25

Right ventricle & Pulmonary artery

Front 26

What is the PPP for angiostrongylus vasorum?

Back 26

~7 weeks

Front 27

Pathogenesis of angiostrongylus vasorum?

Back 27

- Chronic infection

- Adults in large vessels & eggs in pulmonary capillaries

- Chronic congestive cardiac failure

- Fibrosis in arteries; "Pipe stem" feeling

- Lung mottled, penetrating L1

- Bleeding

Front 28

A radiograph of a dog thorax may be used to determine angiostrongylus vasorum infection.

True or False?

Back 28

TRUE - Fluffy, ill-defined opacities in lungs indicate infection.

Front 29

Clinical signs of Angiostrongylus vasorum?

Back 29

Early on:

- Asymptomatic

Later:

- Increased RR & coughing when exercised

- Symptoms in resting dog with heavy worm burden

- Sub cut haematomas

- Can be associated with brain or spinal cord haemorrhage

Front 30

Angiostrongylus vasorum can be confused with __________ poisoning.

Back 30

WARFARIN

- Parasite excretory/secretory products interfere with blood clotting, resulting in haematomas.

Front 31

Diagnosis of angiostrongylus vasorum?

Back 31

1. Fecal samples - L1 characteristic tail w/ small spine

2. PCR - detects parasite DNA

3. Ag test (IDEX)

Front 32

Distribution of angiostrongylus vasorum?

Back 32

Found in UK & Europe

- Hotspots in SW of UK & increasing/moving North

Front 33

Treatment of angiostrongylus vasorum?

Back 33

- Fenbendazole (Panacur)

- Plasma transfusion

Front 34

Host for aelurostrongylus abstrusus? Life cycle?

Back 34

CAT

Indirect

- IMH: Mollusks (eaten by cats)

- Predilection site: Lung parenchyma & sm bronchioles

Front 35

Pathogenesis of aelurostrongylus abstrusus?

Back 35

Not very pathogenic.

- Small granulomas contain worms in lung, which soon resolve if treated

- Rarely, large lesions

- Muscular hypertrophy/plasia

Front 36

Clinical signs of aelurostrongylus abstrusus?

Back 36

Mild

- Chronic moist cough

- Coughs/sneezes following handling

- Mild dysnopea (breathlessness)

Front 37

Diagnosis of aelurostrongylus abstrusus?

Back 37

L1 eggs in feces

Front 38

Epidemiology of aelurostrongylus abstrusus?

Back 38

>5% UK Prevalence

- Widespread IMH

- Wide range of paratenic hosts.

Front 39

Host of oslerus osleri? Life cycle?

Back 39

Dogs & wild caniids

Direct - No IMH

Infection via ingestion of L1s

Front 40

Predilection site of oslerus osleri?

Back 40

Nodules at tracheal bifurcation

Front 41

Clinical signs of oslerus osleri?

Back 41

Usually asymptomatic

* +/- dry cough

* Exercise intolerance

* Most prevalent in younger dogs (6-12 months)

Front 42

Diagnosis of oslerus osleri?

Back 42

- History of chronic dry cough/exercise intolerance

- L1s in sputum or feces (distinct swirled, snail-like appearance in sputum)

- Bronchoscopy - nodules & L1

- L1 has distinctive "s" shaped tail

Front 43

Epidemiology of oslerus osleri?

Back 43

6% prevalence in UK

- Nursing bitch passes to pups

- L1 immediately infective