Infectious Aetiologies of Heart (lungworms & heartworms) Flashcards
what is Dirofilaria immitis
a nematode (roundworm) parasite
what is the final host of D. immitis
dog, wild dog, cat, ferret, sea lion (man accidental FH)
what is the intermediate host of D. immitis
mosquito
where is the site of infection in D. immitis
right ventricle, posterior vena cava, pulmonary artery
where is D. immitis distributed
USA, warm temperate zones (Europe), tropics
what is the life cycle of D. immitis
what is the pathogenesis of D. immitis in dogs (4)
depends on worm burden (low numbers can be little apparent ill effect, high numbers lots of problems)
pathology associated with adults in heart
impede blood flow –> chronic congested right-sided heart failure
- pulmonary embolism (adults blocking vessels, important if treat to kill adult worms)
- vena cava syndrome (fatal 24-48hrs)
- endocarditis in valves, pulmonary endarteritis (local inflammatory response)
- glomerulonephritis (deposition of immune complexes in kidney)
what are the clinical signs of D. immitis (4)
- cardiovascular dysfunction
- listless/gradual loss of condition
- exercise intolerance
- chronic soft cough
how is D. immitis diagnosed
- clinical signs and history
- radiographs, echocardiograph
- detection of mf in blood (wet film, stain dry blood film)
- detection of circulating antigen (ELISA)
how is D. immitis diagnosed using antigen tests
can detect a single female but not a male worm (antigen is secreted by adult worm)
start testing by 6-7 months of age (PPP ~6 months)
more sensitive than mf detection –> esp. if animal on prophylaxis
what are occult infections
adults but no mf
why is it recommended to do both mf test and antigen test
some dogs have occult infections while some dogs have mf but no Ag
what are factors affecting epidemiology of D. immitis in dogs
- density of dogs
- number of strays
- mf can be present for long periods
- poor immunity
- poor owner compliance for prophylaxis
what are the epidemiological factors that affect D. immitis in mosquitos (4)
- distribution + spread of susceptible vectors (environmental change/urban heat islands, intro/spread of new vector species, capacity for rapid population increases)
- short developmental period mf-L3, 10-14 days (temp dependent development –> stop developing if <14 degrees)
- some mosquitos can survive for months
- infection rates can vary 2-19% (but can be much higher in vinicity of infected dogs)
how is D. immitis controlled
prophylaxis is basis of control
tropics: treat all year round
temperate zones with mosquito season: treat 1 month before to at least 2 months after
recommended to treat year round –> better compliance
how is D. immitis prophylactically controlled
- macrocyclic lactones (ex. ivermectin/milbemycin - orally or selamectin/moxidectin topically) monthly
- kill L3 and L4 up to 6 weeks p.i - DEC (diethylcarbamazine) daily
prophylactic drugs don’t kill adult worms –> but MLs may have sterilizing effect on female worms
what can occur when treating D. immitis infected dogs
must check mf status of dog
ivermectin and DEC also kill mf –> if mf + can induce anaphylactic shock
ideally dogs should be mf - pre treatment
what does prophylaxis treatment target in D. immitis
L3/L4
how else can D. immitis be prevented
- keep animals indoors at peak mosquito biting times (dusk)
- insecticide collars
- attempt to reduce mosquito population
what are the principles of treating D. immitis infected dogs
- improve clinical condition
- eliminate all stages of worm
- minimize post-treatment complications
what is wolbachia and why is it significant in D. immitis
D. immitis harbours a bacterial endosymbiont wolbachia
killing wolbachia with doxycycline sterilizes female –> eventual death of adult worm
combo of IVM and doxycycline kills adults
what are the current treatment recommendations in D. immitis
combo treatment with ML and doxycycline prior to adulticidal therapy (moxy-doxy) –> ML clears Mf and prevents new infections, dox reduces pathology associated with dead adults, shrinks worm mass
followed by melarsomine (immiticide) to kill adult worms
what occurs in D. immitis infections in cats
not well adapted –> very pathogenic
adult worms live for shorter period compared to dog
mf transient in blood
what are the differences in dog and cat D. immitis infections
how is D. immitis treated in cats
pathology is assocaited with the inflammatory response to worms/worm death and not from biomass of adults (as in dogs)
if no clinical signs –> can allow spontaneous recovery with monitoring
melarsomine very toxic in cats
chemoprophylaxis using ML compounds
what is the host, IMH and site of infection in Angiostrongylus vasorum
host: dog, fox
IMH: molluscs
site: right ventricle, pulmonary artery
what is the life cycle of A. vasorum
what is the pathogensis of A. vasorum
chronic infection
pathology associated with adults in large vessels and eggs in pulmonary capillaries
chronic congestive cardiac failure
fibrosis in arteries
lung mottled, penetrating L1
bleeding
what are the clinical signs of A. vasorum
- early on –> asymptomatic
- later –> increased resp. rate/cough on exercise
- heavy worm burded –> symptoms in resting dogs (fainting, s.c hematoma)
- can be associated with brain and spinal cord hemorrhage
- sub-cutaneous hematomas
- parasite excretory/secretory products interfere with blood clotting (can be confused with warfarin poisoning)
how is A. vasorum diagnosed
- Baermann on fecal sample –> should sample on 3 days to ensure detection, L1 characteristic tail with small spine
- PCR
- AG test –> detects antigen in the blood stream
