order: Rhabditida Flashcards
(23 cards)
What class do Strongyloides species belong to?
Phasmidida
What order do Strongyloides species belong to?
Rhabditida
Name a Strongyloides species that infects pigs.
Strongyloides ransomi
Name a Strongyloides species that infects rabbits.
Strongyloides papillosus
What is the size range of Strongyloides species?
2-9 mm
Where do Strongyloides species typically locate in the definitive host?
Small intestine
What is a distinct morphological feature of Strongyloides species?
- Special shape of esophagus: long prebulbus and bulbus
- Hairy
- Free-living
What are the two routes of infection for Strongyloides species?
- Tracheal route (pulmo-tracheal)
- Somatic route
What happens during the tracheal route of Strongyloides infection?
Skin penetration (L3) - subcutis - lymphatic vessels - lympho-haematogenous transport to heart and lungs - pharynx - small intestine - adult females (day 6 in pigs, day 9 in ruminants)
Lactogenic infection of piglets in the context of Strongyloides?
Lactogenic infection of piglets can take place until 3rd litter, as not all hypobiotic larvae are activated at once
Describe the life cycle of Strongyloides.
Direct life cycle
1. L1 (rhabditiform) larva is shed in the feces of FH
Homogenic – typically happens in young animals, unfavourable conditions
- In environment some egg hatch and develop directly to infective L3 (filariform – infective stage)
- Larva re-infect host through skin or orally with pasture, food, water
Heterogenic – in favorable conditions, older, immune animals
- Larva L1 molts 4 times to free living adult worms
- They mate and female worms produce eggs
- Rhabditiform (non-infective – feeding form) hatch from the embryonated eggs, that molts 2 times to Filariform larva L3 (infective form – non-feeding)
- They can either complete development to adult males and females in the environment or infect a host through feed or skin.
2. Infection per os: larva L3 migrate directly to SI and mature there.
3. Infection per skin: The larva L3 migrate through blood to bronchi (not always), where they are coughed up and swallowed to the SI where they mature. Adult larva make egg in the intestinal mucosa.
- L1 hatch from the egg already in the intestine and autoinfection are possible. Autoinfection happens when L1 rhabditiform develop in the intestine to L3 filariform, which begin a migration from intestines to skin and then return to GIT.
OBS: Larvae produced don’t always follow the usual path to the lungs, but reach other organs, including the placenta, udders and milk. This way they can be directly transmitted to the suckling (lactogenic transmission) also transplacental is possible.
What is the initial larval stage of Strongyloides shed in feces?
L1 (rhabditiform) larva
What are the two types of cycles in Strongyloides life cycle?
- Homogenic
- Heterogenic
What is the infective stage of Strongyloides?
L3 (filariform)
How can L3 larvae infect a host?
- Through skin
- Orally with pasture, food, water
What is autoinfection in Strongyloides?
When L1 rhabditiform develop in the intestine to L3 filariform and migrate from intestines to skin, then return to GIT
What are common clinical signs in young animals infected with Strongyloides?
- Pulmonary symptoms
- Dermatologic symptoms
- Abdominal pain
- Distention
- Shock
- pulmonary and neurological symptoms in immunosupressed animals
What is a common treatment for Strongyloides infections?
- Ivermectin
- Doramectin
- Levamisole
- Thiabendazole
- Fenbendazole
What are some control methods for Strongyloides infections?
- Good hygiene
- Removal of feces
- Dry bedding
- Cleaning pens of animals
What diagnostic methods can be used for Strongyloides?
- Faecal flotation
- Larvoscopic method (Baermann technique)
Eggs of Strongyloides
- small
- oval, symmetrical
- 2 thin shells
- embryonated (L1)
- Light grey/transparent colour
Strongyloides routes:
1. Tracheal route (pulmo-tracheal):
Skin penetration (L3) - subcutis - lymphatic vessels - lympho-haematogenous transport to heart and lungs - pharynx - small intestine - adult females (day 6 in pigs, day 9 in ruminants)
2. Somatic route:
Larvae pass in bloodstream to the lungs - blood to organs (fat, mammary gland, striated muscles) - In body tissues, parasitic larvae (L3) can remain viable in hypobiotic state for long periods - “somatic larvae” becomes activated shortly before birth and migrate to mammary gland enabling colostral and lactogenic infection. Lactogenic infection of piglets can take place until 3rd litter, since not all hypobiotic larvae are activated at once. The excretion of larvae in milk is highest at the beginning of lactation. Duration is different in different species (horse the longest, sheep and pigs the shortest).
Strongyloides spp:
- Strongyloides ransomi – pig
- Strongyloides papillosus – Ru, rabbit
- Strongyloides westeri – horse, donkey
- Strongyloides stercoralis – dog, cat, man (zoonotic), monkey
- Strongyloides ratti – rats
- Strongyloides avium – birds (SI & caeca)
