Heart and Lung Worms in SA Flashcards
(25 cards)
Superfamily Filarioidae
Tissue dwelling
IMH are insect vectors
Primitive forms release eggs, more highly evolved (D. immitis) release live L1 or microfilariae (Mf)
Mf can show periodicity in blood
Dirofilaria immitis
Host- dog(natural), cat, ferret, sea lion, (man, doesn’t cause patient infection)
IMH- mosquito
Site- cardiovascular system (especially right ventricle, posterior vena cava, pulmonary artery)
Distribution- USA, warm temperate zones (Europe), tropics
Mosquitoes are present in UK that can transmit this, but only dogs that have tested positive have been imported
D. immitis pathogenesis
Depends on worm burden- low, no apparent ill effects; high, lots of problems
Associated with adults in heat and tends to lead to right sided heart failure
Pulmonary embolism bc adults blocking blood vessels
Vena cava syndrome-VC blocked and dog collapses suddenly
Endocarditis in valves, pulmonary endarteritis bc of local inflammatory response
Glomerulonephritis- deposition of immune complexes in kidney
D. immitis clinical signs
Cardiovascular dysfunction
Listless/gradual loss of condition
Exercise intolerance
Chronic soft cough
Diagnosis of D. immitis
Detection of mf in blood
Detection of circulating antigen (most common way to find)
Clinical signs and history
Ag tests can detect a single female (but not male)
More sensitive than Mf detection
Some dogs have occult infections where there are adults but no Mf
Start testing by 6 months of age
D. immitis epidemiology
Dog- Density of dogs Mf present for long periods Poor immunity Poor owner compliance
Mosquito-
Distribution of susceptible vectors
Capacity for rapid pop increase
Short developmental period
D. immitis control
Easier to control than treat
Temp- requires 24hr daily temp >18oC for ~1 month for the parasite to develop in the mosquito
Prophylaxis is the basis of control- year long in tropics, and 1 month before mosquito season and two months after in temperate
D. immitis prophylaxis
Marocyclic lactones (Ivremectin) monthly which kill L3 and L4 up to 6 weeks post infection DEC (diethylcarbamazine) daily
Prophylactic drugs do not kill adult worms, may have sterilizing effect on female worms though
Some evidence of treatment failures, possible resistance
In endemic areas pups should be on drugs at 6 weeks of age
If Mf positive dog is treated it can induce anaphylactic shock, especially if they have high Mf counts
D. immitis prevention
Keep animals in doors and peak mosquito biting times
Insecticide collars or spot-on
Attempt to reduce IMH population, but really hard
D. immitis treatment
Surgical removal or adult worms in specialized clinic
Treat with Melarsomine, but not licensed in UK
Treat to kill Mf
Experimental treatment- Many species of filarial worms harbor a bacterial endosymbiont (Wolbachia). Killing Wolbachia neg affects adult worms.
Combination of IVM and deoxycycline appear to kill adult immitis
D. immitis in cats
Not well adapted, but very pathogenic
Adult worms live for shorter period of time when compared to dog
Mf are transient
Treatment of D. immitis in cats
Pathology relates to inflammatory response to worms/worm death
If no clinical signs, can allow spontaneous recovery, with monitoring
Melarsomine is very toxic in cats
Superfamily Metastrongyloidea
Angiostrongylus vasorum
Aelurostrongylus abstrusus
Oslerus osleri
Indirect LC (except O. osleri) Clinically mild (except O. osleri) IMH- molluscs (except pig Metastrongylus)
Angiostrongylus vasorum
Host- dog, fox
IMH- molluscs
Site- Right ventricle
Small brown worms
Angiostrongylus vasorum pathogenesis
Chronic infection and pathology is associated with adults in large vessels and eggs in pulmonary capillaries
Chronic congestive heart failure
Fibrosis in arteries-pipe stem feel
Lung mottled from penetrating L1
Sub q bleeding
Angiostrongylus vasorum clinical signs
Early on its asymptomatic, but later theres increased respiratory rate/cough on exercise. With heavy worm burden, symptoms are seen in resting dog
Fainting
Sub q haematoma because the ES products interfere with blood clotting (can be confused with warfarin poisoning)
Can be associated with brain and spinal cord haemorrhage
Angiostrongylus vasorum diagnosis
Fecal sample
L1 characteristic tail with small spine
PCR
Ag test by Idexx
Angiostrongylus vasorum epidemiology
Found in UK and Europe, hotspots are SW UK, but distribution seems to be increasing
May be associated with warm damp winters and an increase in slugs
Aelurostrongylus abstrusus
Host- cat
IMH- molluscs with L3
Site- lung parenchyma and small bronchioles
Not very pathogenic, creates small granulomas in lung around worm and rarely larger lesions but granulomas soon resolve
Muscular hypertrophy/plasia
Aelurostrongylus abstrusus clinical signs
Mild
Chronic moist cough
Following handling, coughs and sneezes
Mild dysnopea (breathless)
Diagnosis via L1
Aelurostrongylus abstrusus epidemiology
Widespread because ubiquitous IMH
Wide range paratenic hosts
Uk prevalence >5%
Oslerus osleri
Host- dog or wild caniids
NO IMH bc direct LC
Site- nodules at trachieal bifurcation
Oslerus osleri clinical signs
Usually asymptomatic
+/- dry cough
Exercise intolerance, most obvious in working dogs
6-12 months old
Oslerus osleri diagnosis
History of chronic dry cough/exercise intolerance
L1 in sputum or feces (has distinctive S shaped tail)
Bronchoscopy- nodules contain L1
