9. Heartworm disease. (symptoms, diagnosis, treatment and prevention) Flashcards

1
Q

Heart worm disease info?

A

Technically a pulmonary disease; Adult worms are in the pulmonary arteries → RS of the heart is only involved later

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2
Q

Parasitology of heartworm disease?

A

PARASITOLOGY

Dirofilaria immitis – Transferred by mosquitos

Definitive host & main reservoir: Dogs & wild canids (cats

occasionally infected)

HARD (Heartworm Associated Respiratory Disease): No

maturation, but migration of larvae within the lungs

Severity of infection is dependent on: No. of worms; How long they have been present; Body’s reaction to the infection; Exercise of the animal; Size of the animal

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3
Q

Pathogenesis of heart worm disease?

A

PATHOGENESIS

Live adult worms

→ Mechanical trauma; Immunosuppressive effect

→ Damage the intima of blood vessels → Vascular lesions

Dead adult worms

→ More severe vascular reactions → Lung pathology

→ Thrombi → Embolisation, inflammation & fibrosis

Inflammatory mediators from heart worm → Hypoxia →

Vasoconstriction → Bronchoconstriction → Parenchymal lung inflammation & mild non-cardiogenic oedema formation

Pulmonary artery disease → Interstitial fibrosis

Thromboembolism after treatment with adulticide medication

§ Worm accumulation → Tricuspid regurgitation

§ Long-term infection → Caval syndrome (see later) →

CHF

Other consequences: Liver damage; Cirrhosis; Glomerulonephritis

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4
Q

Clinical signs of heartworm disease?

A

CLINICAL SIGNS

Mild form: Ø CSx; Chronic cough

Moderate form: Cough; Exercise intolerance; Abnormal lung sound

Severe form: Cough; Epistaxis; Exercise intolerance; Dyspnoea;

Abnormal heart & lung sounds; Hepatomegaly; Syncope; Ascites

Caval syndrome

Adult worms are displaced from the pulmonary arteries to the right

side of the heart; Seen more so in small dogs

§ Sudden: Lethargy; Weakness; Haemoglobinuria

§ CSx associated with RS-CHF

§ Tricuspid cardiac murmur

Cat: Bronchitis; Asthma signs; Intermittent vomiting; Lethargy;

Cough; Dyspnoea

Death of adult worm → HARD & shock → Death

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5
Q

Diagnosis of heart worm disease?

A

DIAGNOSIS

Serologic (Antigen) testing: Recommended for routine screening

Note: This only detects adult female worms; May produce falsenegative results in cats

“Drip test”; Modified Knott test; PCR

Bloods: Eosinophilia; Basophilia; Neutrophilia; Monocytosis

Echocardiography:

§ RA/RV dilation

§ RV hypertrophy

§ Paradoxical septal motion

§ Small left heart

§ Pulmonary artery dilation

ECG: Usually normal

Radiology

Used to support diagnosis

§ Pulmonary hypertension

§ RV enlargement

§ Enlarged pulmonary arteries

Thromboembolism signs

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6
Q

X- ray signs?

A
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7
Q

Cat diagnosis?

A

Cat: History; CSx; Thoracic radiograph; Echocardiography;

Serology

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8
Q

Treatment of heartworm disease?

A

TREATMENT

Asymptomatic/Mild disease: Ø

Moderate-severe/Concurrent: Challenging to treat

Goals: Improve clinical condition of the animal; Eliminate all life stages of HW

Adult HW tx: Melarsomine

Microfilariae HW tx: Moxidectin; Imidaclopride (macrocyclic lactones)

High-risk dogs: Stabilise before Melarsomine treatment

Dogs with RS-HF: Furosemide; ACE-inhibitor; Inodilator

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9
Q

Treatment plan for dogs graph?

A
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10
Q

Prevention of heartworm disease?

A

Prevention

Testing for AGs & microfilariae must be done before any

prophylactic treatment

Preventative treatment with macrocyclic lactones: Ivermectin;

Moxidectin; Milbemycin

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11
Q

Prognosis of heartworm disease?

A

PROGNOSIS

Can be good → guarded, depending on severity

Caval syndrome: Poor → grave

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