Lesson 82 - Vascular Diseases in LA & Vascular Parasites

What is the scientific name for heartworms?

Dirofilaria immitis

Where do adult heartworms live?

pulmonary arteries

How long do heartworms live in dogs?

5-7 years

How long do heartworms live in cats?

2-3 years

What type of life cycle do heartworms have?

indirect life cycle

What do heartworms require for part of their life cycle?

mosquito intermediate host

What is the life cycle of heartworms?

1. microfilaria (L1) circulate in the blood

2. mosquito acquire L1

3. L1 develops into L2 and L3 in the mosquito

4. mosquito bites another animal transmitting the L3 to them

5. L3 develops into L4 and adult in the host

How long does it take for L4 to become adult?

2-3 months

How long does it take for adult heartworm to become patent?

1. 3-4 months

3. 6-7 months post-infection

Which species has persistent microfilaria commonly?

dogs

Which species is aberrant migration of heartworms more common in?

cats

What locations can have aberrant migration of heartworms?

1. CNS

2. eyes

3. skin

What species usually have low heartworm burdens and transient or absent microfilaria?

cats

What is an atypical/accidental host for heartworms?

cats

What is the natural/definitive host for heartworms?

dogs

How long is the prepatent period in cats?

1. 7-8 months

2. often never patent

What is the key clinical pattern for heartworms in dogs?

1. chronic cardiopulmonary disease

2. cough

3. exercise intolerance

4. weight loss

What is the key clinical pattern for heartworms in cats?

1. respiratory disease

2. coughing

3. dyspnea

4. vomiting

What is the pathology driver for heartworms in dogs?

disease from adult worms in pulmonary arteries

What is the pathology driver for heartworms in cats?

disease from immature worms and intense inflammation

What species is sudden death associated with heartworms more common in?

cats

What changes are seen in the heart and lungs due to heartworms?

1. endarteritis

2. villous intimal proliferation

3. thickening and loss of elasticity of pulmonary arteries

4. pulmonary hypertension

5. right ventricular hypertrophy

6. progression to congestive heart failure and ascites

What determines the severity of the infection for heartworms?

1. duration; longer causes more vascular damage

2. number of adult worms

3. host immune response

What other parasites is important to consider with heartworms?

Wolbachia pipientis

What is the importance of Wolbachia pipientis?

endosymbiotic bacteria for heartworms that are an important drug target

How do we treat Wolbachia pipientis?

1. prior to adulticide

2. doxycycline for 4 weeks

Why do we treat the wolbachia before the heartworms?

if released during worm death can trigger strong inflammatory response which contribute to pulmonary pathology and thromboembolism

What signs can be seen in advanced cases of canine heartworm disease?

1. hemoptysis

2. ascites

3. hepatomegaly

4. jugular distension

5. sudden collapse from caval syndrome

What are the signs of caval syndrome in dogs?

1. hemoglobinemia

2. hemoglobinuria

3. weakness/collapse

A 5-year-old mixed-breed dog presents with sudden onset weakness, pale mucous membranes, and dark red-brown urine. On examination, the dog is tachycardic with a systolic murmur and signs of shock. Bloodwork reveals anemia and hemoglobinemia. An echocardiogram confirms a heavy burden of Dirofilaria immitis extending into the right atrium and vena cava. What is the most appropriate immediate treatment?

Perform surgical removal of heartworms via jugular venotomy

A 3-year-old dog presents for a routine exam and tests positive for Dirofilaria immitis. The dog is bright, active, and shows no clinical signs. Thoracic radiographs are unremarkable, and bloodwork is normal.

What stage of heartworm disease is most consistent with this presentation?

Mild (Class I)

A 6-year-old dog presents with a chronic cough and exercise intolerance. Physical exam reveals mild weight loss and occasional lung sounds. Thoracic radiographs show enlarged pulmonary arteries, but no signs of right-sided heart failure.

What is the most appropriate classification?

Moderate (Class II)

An 8-year-old dog presents with collapse, dyspnea, ascites, and pale mucous membranes. The dog is weak and has hemoglobinuria. Imaging confirms a heavy worm burden of Dirofilaria immitis obstructing the right heart and vena cava.

How should this case be classified?

Caval syndrome (Class IV)

A 7-year-old dog presents with chronic cough, marked exercise intolerance, weight loss, and intermittent dyspnea. On physical exam, the dog has abnormal lung sounds, a thin body condition, and mild ascites. Thoracic radiographs reveal enlarged, tortuous pulmonary arteries and evidence of right-sided heart enlargement. Bloodwork shows mild anemia.

The dog tests positive for Dirofilaria immitis.

What is the most appropriate classification of this dog's heartworm disease?

Severe (Class III)

What are the stages for feline heartworms?

1. stage 1 acute inflammation from immature worms reaching lungs

2. stage 2 severe inflammation from death of worms

3. stage 3 chronic lung remodeling and respiratory disease

What stages of feline heartworms could have sudden death?

stage 2 and 3

What are the diagnostic methods for heartworm in dogs?

1. antigen testing (ELISA)

2. microfilaria tests

3. imaging

4. CBC and chemistry

What do we know about antigen testing for heartworm in dogs?

1. detects adult female uterine antigen

2. false-negatives can occur

3. highly sensitive and specific in dogs

4. positive as early as 6 months post infection

What can cause false negatives with antigen testing?

1. low worm burden

2. male-only infections

What do we know about microfilaria tests in dogs?

1. modified Knott's or wet mount

2. some dogs and almost all cats are a-microfilaremic

3. confirms patent infections

4. must differentiate between Acanthocheilonema reconditum

5. important for assessing transmission risk

What test confirms patent infections of heartworms in dogs?

microfilaria tests

What is Acanthocheilonema reconditum?

1. non-pathogenic filaria that resembles heartworm

2. smaller, curved

3. blunt head and hooked tail

4. progressive motility

What do we know about imaging for heartworms in dogs?

1. thoracic rads can show enlarged tortuous pulmonary arteries and right heart

2. echocardiography can allow for direct visualization of worms

What can we see on CBC and chem for heartworms?

1. eosinophilia

2. mild anemia

3. maybe elevated liver enzymes

How do we diagnose heartworms in cats?

1. antigen tests have low sensitivity

2. antibody tests indicate exposure

3. radiographs show enlarged right caudal pulmonary artery

4. echo allows for direct visualization of worms when present

Which test is helpful in cats but not dogs for heartworms?

antibody test

How do we prevent heartworm infections?

macrocyclic lactones

How do macrocyclic lactones prevent heartworms?

kill L3/L4 larvae acquired in the previous month

What is important vascular parasite in horses?

large strongyle: Strongulus vulgaris

What is the most pathogenic equine nematode?

Strongulus vulgaris

What type of life cycle does Strongulus vulgaris have?

direct life cycle

What is the life cycle of Strongulus vulgaris?

1. eggs passed in feces

2. L1-L3 develops on pasture

3. horse ingests L3 larvae

4. L3 penetrate intestinal wall and migrate

5. develop to L4 and L5 in main arteries then return to colon as adults

How does Strongulus vulgaris migrate?

using arteries to the cranial mesenteric artery and its major branches

How long is the prepatent period for Strongulus vulgaris?

6-7 months

What is the most pathogenic part of a Strongulus vulgaris infection?

migration of the larvae

What is the pathology and clinical signs with Strongulus vulgaris?

1. endarteritis and thrombosis can cause aneurysm

2. thromboembolism can cause ischemia and intestinal infarction

3. colic and ileus and possible intestinal rupture

How do we diagnose Strongulus vulgaris?

1. fecal egg count

2. serology for antibodies

3. ultrasonography

4. clinical signs and history mainly

What is difficult with fecal egg counts for Strongulus vulgaris?

1. cannot differentiate from other strongyles

2. pre-patent period there will be no eggs

What can we see on ultrasound for diagnosing Strongulus vulgaris?

thickened cranial mesenteric artery and altered blood flow

How do we treat Strongulus vulgaris?

1. adults: all available antihelmintics

2. larvae: ivermectin/moxidectin

3. exploratory laparotomy with possible intestinal resection

What is cor pulmonale?

alteration in the structure and function of the right ventricle caused by a primary respiratory disorder

What is cor pulmonale most commonly caused by?

chronic obstructive pulmonary disease

What horse diseases could lead to cor pulmonale?

1. primary pneumonia

2. lungworm

3. equine asthma

What farm animal diseases could lead to cor pulmonale?

1. high altitude

2. lungworm

3. pneumonia

4. congenital cardiac disease

5. endocarditis

6. toxins

7. hardware disease

What ruminant is cor pulmonale more common in?

bovine

What is a secondary form of heart disease?

cor pulmonale

What triggers high mountain disease?

low oxygen levels at high altitude cause pulmonary arterioles to constrict

What is the vascular response in high mountain disease?

chronic constriction leads to remodeling (thickening) resulting in sustained, severe pulmonary hypertension

What is the heart effect in high mountain disease?

right ventricle has to work harder so it can hypertrophy and eventually fail

What results from the right side of the heart failing with high mountain disease?

fluid leaks from blood vessels resulting in edema in the brisket, abdominal cavity, and neck

What animal is high mountain disease more common in?

bovine

What puts cows at risk for high mountain disease?

1. >5000 ft altitude

2. sudden altitude change

3. calves

4. pregnant animals

Why are calves at more risk for high mountain disease?

hearts are not strong enough to pump against the increased pulmonary pressure

What are predisposing factors for high mountain disease?

1. genetics and breed: angus

2. respiratory diseases

3. locoweed (Oxytropis spp.)

What are the clinical signs specific to high mountain disease?

1. ventral and intermandibular edema

2. jugular vein distention and pulsation

3. ascites/abdominal swelling

4. exophthalmia

What are the disqualifications at necropsy for high mountain disease?

1. hardware disease

2. myocarditis

3. congenital heart defects

How do we treat high mountain disease?

1. send to lower altitude

2. treat primary lung disease

3. furosemide

4. digoxin

5. sildenafil

What is the initial treatment for high mountain disease?

send to lower altitude

How do we prevent high mountain disease?

1. genetic selection

2. prevent locoweed ingestion

3. reduce incidence of pulmonary diseases

What typically causes vasculitis?

immune-mediated inflammation

What can cause vasculitis in horses?

1. strangles

2. Corynebacterium pseudotuberculosis

3. influenza

4. vaccinations

What are the clinical signs of purpura hemorrhagica?

1. edema of legs, head, and ventral abdomen

2. petechiae or ecchymoses

3. fever, lethargy, anorexia, colic

4. potential laminitis

5. skin sloughing

6. muscle necrosis or internal organ damage

How do we diagnose purpura hemorrhagica?

1. history of recent infection/vaccination

2. clinical signs

3. blood work

4. skin biopsy

What do we see on bloodwork with purpura hemorrhagica?

1. high fibrinogen

2. neutrophilia

3. high muscle enzymes

How do we biopsy skin for purpura hemorrhagica?

1. prior to steroid treatment

2. early lesions

3. interpret alongside other results

What is the hallmark feature for purpura hemorrhagica?

leukocytoclastic vasculitis

How do we treat purpura hemorrhagica?

1. steroids

2. antibiotics

3. supportive care

What is the prognosis for purpura hemorrhagica?

guarded

What can cause vasculitis in pig?

1. erysipelas

2. strep suis

3. ASF

4. CSF

5. salmonella, actinobacillus septicemia

6. porcine circovirus 2

How does PCVAD spread?

1. oro-nasal secretions

2. also semen, milk/colostrum, in-utero transmission

3. carriers in the herd

4. stress triggers

What is important to know about PCVAD in regards to biosecurity?

resistant in the environment

What can PCV2 lead to?

immunosuppression leading to secondary infections

When are clinical signs of PMWS seen?

6-14 weeks of age

What are the clinical signs for PMWS?

1. sudden and severe signs for 18-24 months

2. wasting/weight loss

3. failure to thrive

4. breathing difficulties and jaundice sometimes

5. some pigs found dead

What is the mortality rate for PMWS?

1. >10% for weaning to grower stage

2. sometimes >30-40%

When are PDNS signs seen?

12-14 weeks of age

What infection often occurs after PMWS?

PDNS

What are the clinical signs for PDNS?

1. starts abruptly

2. sporadic incidents

3. sometimes prolonged outbreak 18-24 months

4. wasting/weight loss

5. failure to thrive

6. acute joint pain and purple skin blotches

What is the mortality rate of PDNS?

1. 0-14% in grower/finisher stages

2. acute and severe infections >60-80%

What are the post-mortem findings for PDNS?

enlarged, pale kidneys with petechial hemorrhages