T1-L4: Parasitology Flashcards
Give the 3 types of symbiosis.
Commensalism: an association in which the parasite only is deriving benefit without causing injury to the host.
Mutualism: an association in which both species benefit from the interaction.
Parasitism: an association in which the parasite derives benefit and the host gets nothing in return but always suffers some injury.
What are the 4 classification of hosts?
Definitive Host: an organism in which the parasite reaches the adult stage and reproduces sexually, if possible. This is the final host. In the majority of human parasitic infections, man is the definitive host.
Reservior Host: The reservoir of an infectious agent is the habitat in which the agent normally lives, grows, and multiplies. Reservoirs include humans, animals, and the environment. The reservoir may or may not be the source from which an agent is transferred to a host.
Intermediate Host: The host harbouring a parasite that primarily grows but not to the point of reaching (sexual) maturity. An intermediate host often acts as vector of parasite to reach its definitive host (where it will become mature).
Paratenic Host: Host where the parasite remains viable without further development
How can parasites broadly be classified?
Through there Phylum:
- Protozoa - for example Flagellates, Ameoboids, Sporozoans and Trypanosomes
- Helminths - such as flat worms and roundworms
- Anthropoid - such as ectoparasites and blood sucking anthropoids
Give the distribution, life cycle, clinical manifestations and treatment of Ascariasis.
(a) Distribution: Prevalent in areas if poor hygiene and affects more than a billion people world wide with a peak prevalence it age 3-8 year olds.
(b) Life cycle: It is a macro parasite, an intestinal nematode. It is passed on by ingesting into the mouth and passing into the faeces due to poor hygiene.
(c) Clinical Manifestations - shows lung migration and so symptoms of a dry cough, wheeze, dyspnoea, haemoptysis etc. In the intestine it can cause malnutrition, malabsorption and migration to the hepatobillary tree and pancreas.
(d) Treatment: Albendazol which prevents glucose absorption starving the worm. Control is via sanitation, education and targeted deworming.
What is the likely diagnosis of a patient who went swimming in a water near in Africa and came pack presenting with malnutrition, hepatic fibrous and renal failure?
What is the treatment?
Schistosomiasis. Treatment is Praziquantel.
What is the life cycle of Schistosomiasis?
Adult worms pair for life. They live for about 10 years. In the bowel form people defecate. The eggs hatch in water and into the snails. The snails can then go through our skin an infect us. The incubation period can be 14-84 days. You can be asymptomatic or symptomatic acute infection
Give common Schistosomiasis.
- S. haematobium
- S. mansoni
- S. intercallatum
- S. japonicum
- S. mekongi
Causes chronic disease resulting in bladder cancer and liver cirrhosis. Increase risk of malignancy also.
What is the name if the parasite that can auto infect?
Strongyloidiasis - It can auto-infect. They die off after 10 years. We can auto-infect ourselves. They can hatch in the GI tract and then re-infect so you can continue having many infections after many years after the initial infection. It is a hyper infection syndrome with mortality rates are up to 90%.
How can Strongyloidiasis be transmitted?
How can we control its spread?
Strongyloidiasis is transmitted through direct penetration of human skin by infective larvae when in contact with soil; walking barefoot is therefore a major risk factor for acquiring the infection. It can also be transmitted sexually.
Control:
- Wear shoes on soil - Avoid contact with faecal matter in sewage - Proper sewage disposal and faecal management
Give details of Hydatid Disease.
It is a microparasite - tapeworm. It is found all around the world where people farm sheep, it is caused by the Echinococcus species. Humans are an accidental host. It is transferred to humans through contaminated species of sheep, passed through dogs to humans. It goes to the liver, lungs and brain primarily but can go to other areas. Usually asymptomatic but when we have them they do continue to grow and cause problems when they get to a large size. They can occasionally rupture. Diagnosis is by serology, and histology. It is treated with Albendazole and praziquantel. Control is by hygiene.
What is the most common cause and most dangerous cause of malaria in the UK? Give other causes.
Plasmodium falciparum is the most common and dangerous cause of malaria. Othe causes include P. vivax, P. oval and P. malariae.
What is the name of the vector malaria is transmitted via?
Anopheles
Give clinical manifestations of malaria.
Causes problems by rupturing red cells, blocking capillaries and causes inflammatory reaction.
• Fever & Rigors (occurs with falciparum malaria every 48hrs or 72hrs with benign malaria)
• Cerebral malaria (confusion, headache, coma)
• Renal failure (black water fever)
• Hypoglycaemia
• Pulmonary oedema
• Circulatory collapse
• Anaemia, Bleeding and DIC
What is the treatment of Malaria?
Anti-malarial (artesunate) and supportive therapy - management of seizures, pulmonary oedema, acute renal failure and lactic acidosis. Exchange transfusion may be helpful in hyper parasitaemia. We do this rarely. We use artesunate now.
Non-Falciparum Malaria can be treated with chloroquine. If they cannot tolerate it give Primaquine.
What is the distribution of Cryptosporidiosis?
- Caused by Cryptosporidium parvum and hominis (micro-parasite, sporozoan)
- Causes diarrhoeal disease
- Human to human spread with animal reservoir (cattle, sheep, goats)
- Faecal-oral spread
- World wide distribution (esp. temperate and tropical)
- Sporadic cases can lead to outbreaks
