11. heartworm

Question 1

general characteristics of Dirofilaria immitis

Answer 1

pulmonary arteries and right ventricle of dogs

12-20 cm male
25-30 cm female

males- spirally coiled posterior end

give birth to microfilariae instead of eggs

heartworm

Question 2

D. immitis infect

Answer 2

pulomary arteries and right ventricle of dogs (wild canids and ferrets)

cats but not as common

heartworm

Question 3

life cycle of Dirofilaria immitis

Answer 3

indirect

IH (mosquitoes) ingest microfilariae

grow to L3 in IH

IH bite DH(dogs) and transfer to host.

Grow to adult in the heart and pulmonary arteries

adults make microfilariae that circulat in the blood

PPP 5-6 months

heart worm

Question 4

PPP of D. immitis

Answer 4

5-6 months

heartworm

Question 5

clinical signs of Dirofilaria immitis

Answer 5

PPP 5 months no clinical signs

obstruction of vessels, heart chambers and valves by adult worms

endarteritis, obstructive fibrosis, pulomonary hypertension, right sided heart failure

exercise intolerance, coughing, weight loss

caval syndrome

heartworm

Question 6

High worm numbers of heartworm appear to nearly occlude smaller arteries, potentially leading to —

Answer 6

physical obstruction and decreased blood flow

D. immitis

Question 7

histo of D. immitis

Answer 7

increased villous proliferation on the
endothelium of the pulmonary arteries

Grossly causes the surface of the vessels to apperar as though it is covered with a lawn of villi

Activation and attraction of leukocytes and platelets

heart worm

Question 8

dead heart worm cause

Answer 8

short life span

will die and get stuck in distal vasculature, causing thrombosis, blood flow obstruction, strong inflammatory response

Question 9

symptoms of heart worm

Answer 9

exercise intolerance
arrhythmias
cough
dyspnea
weight loss
congestive heart failure
caval syndrome

Question 10

caval syndrome

Answer 10

associated with large number of adult worms in pulmonary arteries

interfere with function of the tricuspid valve- hemolytic anemia and right sided heart failure

weak pulse, tachycardia, sudden collapse, hemoglobinemia and hemoglobinuria, disseminated intravascular coagulopathy, and murmur caused by tricuspid regurgitation auscultated best on right side of thorax

caused by D. immitis- heart worm

Question 11

abnormal migration of heart worm to —

Answer 11

eyes
skin
CNS
peritoneal cavity and vasculature

Question 12

4 stages of heart worm

Answer 12

Question 13

clinical signs of heartworm in cats

Answer 13

usually few worms- not good hosts
asymptomatic
severe- HARD- heartworm associated respiratory disease- Persistent tachypnea, intermittent coughing, and increased respiratory effort

GI and neuro symtpoms sometimes
sudden death without warning

usually only male or female infection

Question 14

HARD in cats is caused by

Answer 14

heartworm

Heartworm-Associated Respiratory Disease
Persistent tachypnea, intermittent coughing, and increased respiratory effort

can cause sudden death

usually only male or female infection

Question 15

severity of heart worm is based on

Answer 15

number of adult worms
duration of infection (PPP-6 months)
individual host response

Question 16

diagnosis of heartworm in cats

Answer 16

very difficult- PPP very long

antigen test- SNAP- only used for adult female Ag!

microfilariae testing- modified knotts and blood smear looking for babies

xray (reverse D shape)
echo

Question 17

heartworm diagnosis in cats

Answer 17

microfilariae testing- modified knotts

antigen and antibody test- can lead to false negative cause test only test for female

cats can have infections with only male adults!

Question 18

D. immitis microfilariae vs Acanthocheilonema reconditum

Answer 18

heartworm- tapered head, straight tail

A.R- subQ infection- blunt head, variable (hooked or curved) tail

Question 19

what microfilariae

Answer 19

D. immitis

tapered head and straight tail

heart worm

Question 20

what microfilariae

Answer 20

Acanthocheilonema reconditum

blunt head, hooked or curved tail

SQ

smaller then heartworm

Question 21

positive antigen test and negative microfilariae test for heart worm

Answer 21

“Occult” or Amicrofilaremic Infection

antigen test for female worms, baby worms only form after 6 months

maybe too early for babies or an infection with only female so no babies are made

babies might be killed by monthly preventives

Question 22

antigen negative test and microfilariae positive

Answer 22

weird result- do not think D. immitis (could be D. repens or D. striata)

low worm burden
babies before antigenemia is very rare

presence of antigen antibody complexes that block antigen-

can maybe use ICD immune complex dissociation to open antigen up