Day 6: Heartworm Flashcards
What is the name of heartworm
Dirofilaria immitis
What is the morphology of dirofilaria immitis
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
Who are the hosts of dirofilaria immitis
Domestic and wild canines
Wide range of mammals: cats
Ferrets
Sea lions
Muskrat
Otters
Humans
Other species are considered aberrant hosts
What is the route of infection of dirofilaria
From the bite of a mosquito carrying infective stage larvae (L3) in the mouthparts
What is the prepatent period of heartworm
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
What is a patent infection
Both sexes are present, females fertilized and produce larval offspring called microfilariae that circulate in the blood
What is an occult infection
Presence of adult worms in absence of circulating mf
True or False: The number of circulating mf is related to the number of adult worms or severity of disease
False
The number of circulating mf is NOT related to the number of adult worms or severity of disease
What is the epidemiology of dirofilaria immitis
Distribution of heartworm is worldwide
Lifecycle is shorter in warm climates
Transmission occurs year round in warm climates
What is Class I Dirofilaria immitis
Dogs are asymptomatic
What is Class II Dirofilaria immitis
Dogs exhibit cough or exercise intolerance
What is Class III (Cor Pulmonale) Dirofilaria immitis
Cough
Weight loss
Hemoptysis
Lethargy
Exercise intolerance
Dyspnea
Heart Failure
Large pulmonary artery
Pulmonary hypertension
What is allergic pneumonitis in dirofilaria immitis
Indistinguishable from Cor pulmonale, X-ray diagnosis, eosinophilia
What is Class IV in dirofilaria immitis (Caval syndomre/Liver Failure Syndrome)
Hemoglobinuria
Profound weakness
Anorexia
Worms must be removed surgically or dogs will die
What is the pathology of dirofilaria immitis
Adult worms found in the pulmonary arteries and right heart leading to:
Pulmonary endarteritis
Obstructive fibrosis
Pulmonary hypertension
How are dogs tested for Heartworm
Antigen tests detect adult antigens in blood for infected dogs
How are cats tested for heartworm
Antibody tests
Serologic tests for antibodies to adult worm antigens
How are mf detected
Detect L1 in blood of infected dogs
Knott’s test
Filter test
Absence of mf does not exclude heartworm disease
Ivermectin is a prevention for heartworm. What does it work against
Ivermectin is active against L3 larvae and mf (at high doses)
Active against adults with long term use
Milbemycin oxime is a preventative for heartworm. What does it work against
Active against L# and L4 larvae
Selemectin is a preventative. What does it work against?
Not affective in dogs as in cats due to licking behavior
Adulticide is a treatment. How does it work against heartworm
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
Which treatment drug kills circulating microfilariae L1
Ivermectin
Microfilaricide
Dose is safe for collies
What is the epidemiology of heartworm in cats
An emerging infection
Cats are naturally resistant but can develop patent infections
What are the clinical signs of heartworm in cats
Frequently nonspecific
Vomiting
Inappetence
Acute respiratory distress
Sudden death is not uncommon in infected cats
What is the treatment in infected cats
Arsenical treatment can result in death
Prenisilone treatment
How do you diagnose heartworm in cats
Circulating antibodies directed against dirofilaria L3 and L4 larvae
What prevention is used for cats
Heartgaurd
Interceptor
Selemectin
