L8- Parasitology Flashcards
What does symbiosis mean?
- Living together
- Relationship between 2 or more organisms
- Usually long term
What is mutualism?
- Type of relationship between organisms where two organisms of a different species work together and both benefit
- Oxpecker (food obtained) and rihinocerous (pest control)
What is commenalism?
- Type of relationship where one organisms benefits from the other without harming it
- Cattle egret and livestock
What is parasitism?
• Symbiotic relationship where one organism (the parasite) lives on/in another organism (host) and causes it some harm
What is an ectoparasite?
Live on the surface of hosts e.g lice, tick
What is an endoparasite?
Live within the body of the host e.g plasmodium
What is a permanent (obligate) parasite?
Can not live without its host e.g plasmodium, trypanosoma
What is a facultative parasite?
Able to survive without the host if alternative food source becomes available e.g candida albicans
What is a pathogenic parasite?
Causes disease in the host
What is a non-pathogenic paraside?
Mostly harmless, obtains food and protection from the host without causing harm e.g entamoeba coli
What is an opportunistic parasite?
Causes mild disease in immunologically healthy individuals but cause severe disease in immunodeficient hosts e.g candida albicans, toxoplasma gondii
What is a definitive host?
Host for the adult stage of a parasite or the most developed or sexually mature form e.g mosquitoes for malaria
What is an intermediate host?
Host for sexually immature larval stage of a parasite (no fertilisation takes place) e.g pig for taenia solium
What is an animal reservoir host?
Acts as sources of infection to definitive host e.g monkeys
What is an accidental host?
Life cycles cannot be completed. Not the target host.e.g the eggs of a fish parasite accidentally swallowed by a human
What is a paratenic host?
No development of the parasite until it reaches the definitive host e.gfish host harbours diphyllobothrium latuss until eventually eaten by humans or other final hosts
What is a vector?
Usually arthropds or other living carriers which transmit a disease
What is zoonosis?
Diseases from vertebrate animals to humans
What are endemics, pandemics and epidemics?
- Epidemic- rapid spreading of a disease
- Endemic- disease regularly found among particular people or area
- Pandemic- world wide spread of disease (new)
What are the two types of human parasites?
- Protozoa e.g plasmodium, toxoplasma gondii
* Metazoa (helminths)- platyhelminths (flatworms) and nematodes
What is plasmodium?
- Protozoa parasite that causes malaria
- Spreads via infected female Anopheles mosquito bites
- Facultative ectoparasites
What types of plasmodium cause malaria in humans?
- Plasmodium falciparum (most common in africa)
- Plasmodium vivax (less severe, more widespread)
- Plasmodium malariae (persists in blood without symptoms)
- Plasmodium ovale
What is the life cycle of plasmodium?
- Exoerythrocytic- Liver of human, schizogony
- Erythrocytic- RBC of human ruptures and releases merozoites
- Sporogenic in female anopheles mosquito after biting infected human
What are clinical features of malaria?
- Malaise and headache
- Vomiting
- Anaemia
- Fever, chills, sweats
How is malaria treated?
- Chemotherapy
* Chemoprophylaxis
What is the host immune response to malaria?
- Develops after long exposure and is not sterile
- Strain and species specific because IgG directed against PfEMP1 which is variant
- Adults in endemic areas have antibodies to all PfEMP1 variants
- If adult moves out of endemic area, immune response declines and they are susceptible again
What is trypanosoma?
- Genus of parasitic protozoa causing African trypanosmiasis (sleeping sickness)
- Vector is tsetse fly
- Caused by T. brucei brucie (not in humans), T. brucei rhodensienses (East Africa) and T. brucie gambiense (West Africa)
What are symptoms of sleeping sickness?
- Fever, rash, swelling of face and hands
- Headache
- Swollen lymph nodes
- Weight loss, progressive confusion, daytime sleepiness with night time sleep disturbances
- Coma and death (untreated)
