9 - Nematodes Flashcards
Why are nematodes successful parasites?
- adaptable biochemistry/physiology = survive a range of conditions
- survive under both aerobic and anaerobic conditions.
- have tough outer cuticle which means that they can survive harsh environments (including the host immune system)
In which stage of their life cycle are nematodes infective?
L3
What type of life cycle does ascaris have?
Direct life cycle
Give 5 reasons for the high prevalence of soil transmitted helminths (STH) infections?
- widespread distribution of nematodes
- resilience of eggs in harsh conditions
- high number of eggs produced per parasite
- poor socioeconomic conditions
- lack of education
What is the global distribution of ascaris infections?
It is at highest prevalence in tropical and subtropical areas, however it is found in most parts of South America, Africa and Asia
What are the three main ways that ascaris causes pathology?
- problems associated with the ingestion and migration of larvae
- problems associated with adult parasites in the intestine
- problems caused by adults ‘wandering’ outside of the intestine
How does ingestion and migration of larvae of ascaris cause pathology?
- migration can cause haemorrhages, which can lead to a fever, breathing difficulties and possibly severe haemorrhagic pneumonia
- parasite proteins can cause eosinophilla and allergic hypersensitivity reactions
What pathology is seen as a result of adult ascaris worms in the intestine?
- generalised digestive disorders, including abdominal discomfort and nausea
- malnutrition (in heavy infections)
- a large mass of worms can lead to intestinal obstruction
What pathology is seen as a result of adult ascaris worms ‘wandering’ outside of the intestine?
- a blocked bile duct which can lead to jaundice and issues with fat metabolism
- they can enter the appendix or break through the intestinal wall which can cause peritonitis
- they can enter the trachea and cause suffocation
- they may move up the intestinal tract where they can be vomited up or emerge through the nose
What types of tests can be carried out to determine wether a patient has an ascaris infection?
- Coprological (detection of eggs in faeces)
- serological (detection of antigens or antibodies)
- molecular (PCR detection of parasite DNA from eggs passed in faeces)
- image based diagnostics
What is the global distribution of lymphatic filariasis?
Mostly prevalent in central Africa, south east Asia and areas of South America
How is lymphatic filariasis transmitted?
Via mosquito vector
What are the clinical presentations of lymphatic filariasis?
- lymphoedema which results in swelling in the arms, legs, breasts and genitalia
- decreased ability to fight infection which can lead to harden and thickening of skin as a result of bacterial infections
- tropical pulmonary eosinophilia syndrome (which can cause a cough, shortness of breath and wheezing)
What are some consequences of the body deformities caused by lymphatic elephantiasis?
- social stigma and mental health pro
- loss of income-earning opportunities
- increased medical expenses
How is lymphatic filariasis prevented?
- avoiding mosquito bites (sleeping under mosquito nets, wearing long sleeves and trousers and using mosquito repellent on exposed skin)
- annual mass drug treatment of entire communities
