Flashcards in Tropical Angiostrongylus Deck (24):
What superfamily do Angiostrongylus spp. belong to?
Metastrongyloidea - bursate nematodes
Which species are important and where are they important?
A. cantonensis and costaricensis are important in warmer climates
A. vasorum is important worldwide.
What is A. cantonensis commonly known as?
The rat lungworm - as it resides in the pulmonary arteries of rats.
What are the hosts of A cantonensis?
Rat final host
Molluscan intermediate host
Humans & crustaceans can act as paratenic hosts
Where is A. cantonesis distributed?
Tropical/sub-tropical regions, S.E asia, australia, india, africa....
How can the female cantonensis worm be distinguished from the male worm and why is this?
Barber's pole appearance, blood and white uterus.
Describe the life cycle of A. cantonensis.
L3 larvae in molluscs ingested by rats. The L3 then migrates via the hepatic portal system to the lungs and circulation of the CNS. Moulting through L4 to L5 occurs within a few hours and the L5 migrates to the pulmonary artery via the cerebral vein where they mature to adults and mate. Thin shelled eggs get to the alveolar capilaries where they hatch into L1 larvae which enter the alveoli and are coughed up and swallowed. L1 are excreted in the faeces and will penetrate a mollusc to develop to L3 in 2 weeks. The PPP in the rat is 6 weeks
When is A. cantonensis at its highest?
In rainy weather
How can humans become infected with A.cantonensis?
Eating raw/undercooked molluscs or crabs/prawns.
Eating unwashed vegetables (as they may have slime containing L3)
What is the main pathology of A.cantonensis in rats and in humans?
Rats - heammorhages of alveolar capillaries
- granulomas, haemorrhages and abscesses in the brain
Humans - eosinophilic meningitis/meningo-encephalitis which is highly fatal
What clinical signs are noted in rats infected with A.cantonensis?
Ranges from asymptomatic light infections to incoordination, bloody nasal and ocular discharge and coughing and sneezing in heavy infections.
What are the clinical signs seen in humans infected with A.cantonensis and when do they occur?
1-3 weeks p.i. - stiff neck, headaches, visual disturbance, pins and needles (paraethesia), nausea, vomiting, fever, coma and death in severe cases (2-3%)
How is A. cantonensis visualised in rats?
Baerman technique - see L1 under microscope.
How is A. cantonensis diagnosed in humans?
Imaging and clinical examination (eye)
CSF - worms (rare)
What are the difficulties in treating human A. cantonensis infection?
Anthelimintic treatment killing worms could lead to an inflammatory response in the CNS.
Surgery or laser treatment can be used as well as supportive treatment e.g. lumbar puncture and anti inflammatories.
Outline the principles of control of A. cantonensis in humans.
Education so people properly wash and cook foods (salad, crustaceans and molluscs)
Vector control is not practical.
How does the epidemiology of A. costaricensis differ to that of A. cantonensis?
Rats AND humans can act as a FINAL host. Slugs and snails act as intermediate hosts.
Where does A. costaricensis occur?
Central (endemic) and south (sporadic) America
Outline the LC of A. costaricensis.
L3 migrate and moult through the lymphatics to the ileo-caecal arteries where they mature to adult worms. Eggs pass into the intestinal wall where they hatch. L1 larvae burrow through the intestinal wall into the lumen and pass out in the faeces. This takes 3-4 weeks.
What is the main definitive host of A. costaricensis.
The cotton rat
What is the pathology of A. costaricensis in rats and humans?
Adult worms cause haemorrhage (rats) and eosinophilic granuloma formation leading to mucosal thickening (humans). Large numbers of eggs in rats can cause a yellowing of the serosal surface.
What are the clinical signs of A. costaricensis in
a) Heavy infections can lead to vascular obstructions and infarcts of the gut wall and death.
b) Abdominal pain, annorexia, vomiting, diarrhoea and fever
How does diagnosis differ to that of A.cantonensis?
Can also PM rats and see the necrosis or adult worms in ileo-caecal arteries.
Humans - can palpate abdominal mass, biopsies would reveal eggs, larvae in blood vessels and tissue eosinophilia.