Day 6: Heartworm

Question 1

What is the name of heartworm

Answer 1

Dirofilaria immitis

Question 2

What is the morphology of dirofilaria immitis

Answer 2

Filarid nematode
Females are longer and bigger than males
Males have a curly tail
Primarily found in arteries and frequently in the right side of the heart

Question 3

Who are the hosts of dirofilaria immitis

Answer 3

Domestic and wild canines
Wide range of mammals: cats
Ferrets
Sea lions
Muskrat
Otters
Humans
Other species are considered aberrant hosts

Question 4

What is the route of infection of dirofilaria

Answer 4

From the bite of a mosquito carrying infective stage larvae (L3) in the mouthparts

Question 5

What is the prepatent period of heartworm

Answer 5

6 months from the time the L3 is injected into the skin by the mosquito until the female worms in the dog’s heart shed L1s

Question 6

What is a patent infection

Answer 6

Both sexes are present, females fertilized and produce larval offspring called microfilariae that circulate in the blood

Question 7

What is an occult infection

Answer 7

Presence of adult worms in absence of circulating mf

Question 8

True or False: The number of circulating mf is related to the number of adult worms or severity of disease

Answer 8

False
The number of circulating mf is NOT related to the number of adult worms or severity of disease

Question 9

What is the epidemiology of dirofilaria immitis

Answer 9

Distribution of heartworm is worldwide
Lifecycle is shorter in warm climates
Transmission occurs year round in warm climates

Question 10

What is Class I Dirofilaria immitis

Answer 10

Dogs are asymptomatic

Question 11

What is Class II Dirofilaria immitis

Answer 11

Dogs exhibit cough or exercise intolerance

Question 12

What is Class III (Cor Pulmonale) Dirofilaria immitis

Answer 12

Cough
Weight loss
Hemoptysis
Lethargy
Exercise intolerance
Dyspnea
Heart Failure
Large pulmonary artery
Pulmonary hypertension

Question 13

What is allergic pneumonitis in dirofilaria immitis

Answer 13

Indistinguishable from Cor pulmonale, X-ray diagnosis, eosinophilia

Question 14

What is Class IV in dirofilaria immitis (Caval syndomre/Liver Failure Syndrome)

Answer 14

Hemoglobinuria
Profound weakness
Anorexia
Worms must be removed surgically or dogs will die

Question 15

What is the pathology of dirofilaria immitis

Answer 15

Adult worms found in the pulmonary arteries and right heart leading to:
Pulmonary endarteritis
Obstructive fibrosis
Pulmonary hypertension

Question 16

How are dogs tested for Heartworm

Answer 16

Antigen tests detect adult antigens in blood for infected dogs

Question 17

How are cats tested for heartworm

Answer 17

Antibody tests
Serologic tests for antibodies to adult worm antigens

Question 18

How are mf detected

Answer 18

Detect L1 in blood of infected dogs
Knott’s test
Filter test
Absence of mf does not exclude heartworm disease

Question 19

Ivermectin is a prevention for heartworm. What does it work against

Answer 19

Ivermectin is active against L3 larvae and mf (at high doses)
Active against adults with long term use

Question 20

Milbemycin oxime is a preventative for heartworm. What does it work against

Answer 20

Active against L# and L4 larvae

Question 21

Selemectin is a preventative. What does it work against?

Answer 21

Not affective in dogs as in cats due to licking behavior

Question 22

Adulticide is a treatment. How does it work against heartworm

Answer 22

Kills dirofilaria immitis adults
Immiticide (melarsome dihydrochloride) is the arsenal compound for killing the adult worm in dogs
Only given in epaxial muscles in dogs
Melarsomine dihydrochloride is very toxic in the cat

Question 23

Which treatment drug kills circulating microfilariae L1

Answer 23

Ivermectin
Microfilaricide
Dose is safe for collies

Question 24

What is the epidemiology of heartworm in cats

Answer 24

An emerging infection
Cats are naturally resistant but can develop patent infections

Question 25

What are the clinical signs of heartworm in cats

Answer 25

Frequently nonspecific
Vomiting
Inappetence
Acute respiratory distress
Sudden death is not uncommon in infected cats

Question 26

What is the treatment in infected cats

Answer 26

Arsenical treatment can result in death
Prenisilone treatment

Question 27

How do you diagnose heartworm in cats

Answer 27

Circulating antibodies directed against dirofilaria L3 and L4 larvae

Question 28

What prevention is used for cats

Answer 28

Heartgaurd
Interceptor
Selemectin