Helminth Infections Flashcards
What are helminths?
Worms
What can helminths be divided into?
- Roundworms (nematodes)
- Flatworms (platyhelminths)
How can the helminth life cycle be generalised?
- Ova
- Larvae
- Adults which then produce ova
Which stage of the helminth life cycle is environmentally resistant?
Ova
How are ova able to infect humans?
Through ingestion of food contaminated by excrement, direct contant, or ingestion of contaminated meat
What might ova infection result in?
Inflammatory response
What is the migratory part of the helminth life cycle?
Larvae
What do larvae allow?
Helminths to travel around the human to the correct area
What do adult helminths produce?
Eggs
How long can helminths persist for?
Many years
What shape are round-worms in cross-section?
Circular
How can flatworms be further classified?
- Tapeworms
- Flukes
How do tapeworms and flukes differ?
Tapeworms are segmented, flukes are not
Give 4 types of helminths that can cause gut or tissue infections
- Ascaris
- Schistosomiasis
- Echinococcus
- Enterobius vermicularis
What kind of helminths are ascaris?
Roundworms
What do ascaris cause?
Intestinal infection in humans
How are ascaris ova passed?
In human faeces
How long can ascaris survive in human faeces?
Weeks
Where do ascaris ova hatch once ingested in contaminated foods?
In the gut
What happens to ascaris once hatched in the gut?
Its larvae migrate to the intestine, or can enter the lung or liver
What is the main pathology of ascaris?
Cause bowel obstruction
Can also cause anaemia
How can ascaris cause anaemia?
From when they take blood
How is ascaris diagnosed?
Stool sample containing the ova
What is schistosomiasis caused by?
Schistosoma
What kind of helminths are schistosomas?
Flukes
What do schistosomas cause?
Chronic infections in the hepatic, intestinal, and vesicle venous system
How is schistosoma transmitted?
Its ova are passed out of the intestines of infected humans in stool before its larvae infect snails. After development of the snail, the larvae penetrate human skin and travel to the mesenteric, vesical plexus etc., depending on the species
What happens once the schistosoma larvae are in their desired location?
The adult will lay her eggs
What does schistosomiasis cause?
- Fever
- Hepatospleenomegaly
- Skin rashes
- Dysentry
- Can affect lungs, bladder, or brain
How is schistosomiasis diagnosed?
Ova in a stool sample
What kind of helminths are echinococcus?
Tapeworms
What is the normal host for enchinococcus?
Dogs and sheep, but can infect humans as accidental hosts
How is enchinococcus transmitted?
The ova are passed in the animal faeces and ingested accidentally by the individual
What does enchinococcus cause?
Cysts to develop in the liver and lung, causing hydatid disease
What animals are enterobius vermicularis found in?
Only humans
Where do enterobius vermicularis live?
In the large intestine
How does enterobius vermicularis persist?
The females pass out of the anus at night to lay eggs on the perianal skin. The subsequent perianal itching will result in contamination of the fingers with the larvae, which can then cause spread to other individuals and ingested to develop in the intestine, starting a new life cycle
What can insects act as?
Vectors for some disease causing organisms
What is African sleeping sickness caused by
The Trypanosoma bruceigambiense
What kind of organism is the Trypanosoma bruceigrambiense?
A protozoa
What is African sleeping sickness transmitted by?
The tsetse fly
What happens once the Trypanosoma bruceigambiense enters the blood?
It causes an immune response
Why isn’t the immune reponse against Trypanosoma bruceigambiense effective?
The surface antigens are constantly changing
What does Trypanosoma bruceigambiense cause?
- Generalised lymphadenopathy
- Hypergammaglobulinaemia
What causes Chagas’ disease?
Trypanosoma cruzi
How is Chagas’ disease transmitted?
The reduviid bug
What does Chagas’ disease produce?
- Acute cutaneous oedema
- Intermittent fever
- Shock with significant mortality
What is scabies caused by?
The mite Sarcoptes scabei
What kind of organism is Sarcoptes scabei?
Parasite
What does Sarcoptes scabei do?
Burrows under the skin
What is responsible for the symptoms of scabies?
Both the eggs and the mites cause an allergic response
What does scabies produce?
- Itching
- Symmetrical inflammation of the body
