Zoonotic nematodes Flashcards
Trichinella spp - species names
7 species:
T spiralis
T britovi
T nativa
T nelson
T murrelli
T pseudospiralis
T papuae
Trichinella spp - distribution
Worldwide
Trichinella spp - lifecycle
Parasite of meat eaters
Infective larvae [L1] in muscle tissue of infected carnivorous and omnivorous animals
When ingested - larvae emerge in duodenum
Females = 2-4mm // Males = 1-2mm
Adults bury into intestinal mucosa
Females produce L1 larvae - intestinal wall - lymphatics and blood - skeletal muscles = penetrate striated muscle cell - transform into a nurse cell containing coiled L1 larvae [cysts] - intracellular larvae
Cysts calcify but larvae remain dormant
Trichinella spp - source of infection
Domestic pigs and rats [humans dead-end host]
Trichinella spp - acute phase clinical features
Acute phase:
2-7 days = GI symptoms - diarrhea, N+V
7-21 days = acute inflammatory response to larval migration in striated muscle
-Fever, myalgia, oedema - typically of tongue and eyelids
May also present:
-Myocarditis 5-20%
-Pneumonitis
-Larvae in CNS
-Vasculitis
Trichinella spp - chronic phase clinical features
Chronic inflammatory cysts
Calcification - persistent impaired muscle strength
Trichinella spp - diagnosis
Clinical:
-Fever, muscle pain, swollen eyelids
Lab:
-Eosinophilia
-Serum creatinine kinase and LDH
-Serology = ELISA, western blot
Parasitological:
-Muscle biopsy squash from 4 weeks
Trichinella spp - treatment
Once encapsulated = very resistant to antihelminthics
Post-exposure prophylaxis = albendazole or mebendazole given within 6 days
Chronic stage = high daily doses of benzimidazoles for extended periods
Capillaria philipinensis - distribution
Most cases - Philippines, Thailand, Taiwan, Japan
mostly middle-aged men
Capillaria philipinensis - lifecycle
Normal definitive host = marine birds
Embryonated eggs eaten by fish
Infective larvae develop in fish
Ingestion of undercooked fish
Can cause internal autoinfection
Capillaria philipinensis - clinical
Symptoms - related to worm burden:
-Diarrhea, abdominal pain, weight loss, protein and electrolyte loss
Capillaria philipinensis - treatment
Mebendazole or albendazole
Toxocara spp - diseases
Toxocariasis
Visceral larva migrans
Ocular larva migrans
Toxocara spp - species
T canis
T cati
Toxocara spp - distribution
Worldwide
Toxocara spp - transmission
Ingestion of infective stages
Toxocara spp - lifecycle
Adult wormsn in intestine of puppies and young dogs
Immature eggs passed
Infective in 2-4 weeks [L2 stage]
In puppies <5 weeks = heart-lung cycle followed by GI
In adult dogs = arrest at L2 stage but can infect puppies in utero
In humans = L2 migrate in body and eventually die
Toxocara spp - clinical
Toxocariasis
Mild subclinical febrile illness
Visceral larva migrans:
-Migration of larvae through internal organs
-Mainly children <5 years
-Death of larvae provoke strong inflammatory response
-Non-specific symptoms
Ocular larva migrans:
-Older children and young adults
-Granuloma formation leading to unilateral visual loss, retinal fibrosis, retinal detachment
Toxocara spp - diagnosis
Clinical
Tissue biopsy
ELISA
Toxocara spp - treatment
Albendazole +/- steroids
Angiostrongylus cantonensis [rat lung worm] - disease
Eosinophilic meningitis
Angiostrongylus cantonensis [rat lung worm] - distribution
South Asia, China, Pacific, Australia
Angiostrongylus cantonensis [rat lung worm] - transmission
Undercook snails and slugs
Infected paratenic hosts - shrimps, prawns, mussels
Salads and other leafy vegetables containing small snail
Angiostrongylus cantonensis [rat lung worm] - lifecycle
Humans:
Larvae 2mm migrate to brain, lungs or eye - where they ultimately die
Rat [natural host]:
-Adult worms 2cm in pulmonary arteries of rats - produce eggs - develop into L1 larvae
-Migrate to pharynx - swallowed and passed faeces
-Penetrate or ingested by intermediate hosts [snail or slug]
-Eaten by rats = L3 migrate to subarachnoid space in brain
-Develop and return to venous system - pulmonary arteries
Angiostrongylus cantonensis [rat lung worm] - clinical
Can be benign and self-limiting - also fatal
Most common cause of eosinophilic meningitis:
-Severe HA, neck stiffness, clouded consciousness
Angiostrongylus cantonensis [rat lung worm] - diagnosis
Eosinophilia
Raised cell count CSF >25% eosinophilis
Angiostrongylus cantonensis [rat lung worm] - treatment
Antihelminthic = not recommended
Anasakidae - organisms
Anisakis simplex
Pseudoterranova decipiens
Anasakidae - transmission
Ingestion of infected raw fish or squid by humans - L3 persist
Anasakidae - clinical
Can penetrate bowel wall - leading to extra-inetstinal eosinophilic inflammatory mass
Severe epigastric or abdominal pain
N+V - often within hours of eating infected fish
Generally self-limiting
Can cause anaphylatic reactions in previously sensitised people
Anasakidae - diagnosis
Clinical - may be mistaken for PUD or appendicitis
Eosinophilia
Anasakidae - diagnosis
Unclear
Albendazole - some successful reports
Anasakidae - lifecycle
Adults in gut of marine mammals - seals, whales, dolphis
L2 ingested by crustaceans and mature
Infected crustaceans are eaten by fish and squid [paratenic hosts]
Gnathostoma spingerum [spiny headed worm] - Distribution
SE asia
Central and South America
Gnathostoma spingerum [spiny headed worm] - Lifecycle
Adults worms in stomach of carnivores
Eggs, hatch in water, L1 infects copepod [cyclops]
Eaten by fish or frog - develop to L3
If eaten by humans - migrate around body
Gnathostoma spingerum [spiny headed worm] - clinical
Non-specific symptoms lasting 2-3 weeks
Penetrates gut wall - epigastric pain
Marked eosinophilia
Larvae wanders through tissues [long lived, >10 years]
Gnathostoma spingerum [spiny headed worm] - disease forms
Visceral larva migrans
Cutaneous forms [most common] = painless migrating oedema
Eosinophilic meningitis
Gnathostoma spingerum [spiny headed worm] - diagnosis
Clinical = history of migrating subcutaneous swelling, eosinophilia
Serology = ELISA, western blot
Gnathostoma spingerum [spiny headed worm] - treatment
Prolonged albendazole or ivermectin
