L17 - Protozoan & Helminth Parasites Flashcards
What is parasitism and what is obligate vs facultative parasites?
Parasite benefits at the expense of the host
- obligate = require to spend at least part of their lifecycle in parasitic relationship
- facultative = free living and can complete life cycle without host
What are examples of obligate and facultative parasite and describe the lifecycle of each
Ascaris lumbricoides - lives in gut and lifecycle
Plasmodium falciparum - human and mosquito host
Facultative - naegleria fowleri - infected when jumping into warm water
In plasmodium falciparum which host is definitive and which is intermediate?
- sexual takes place in mosquito so its a definitive host
- humans = intermediate host bc asexual
Define the 4 different types of hosts:
Definitive, intermediate, incidental, paratenic
Definitive = where parasite reaches sexual maturity
Intermediate = host that is required for parasite development but where no sexual development takes place
Incidental = host that can be infected but does not play a role in the lifecycle
Paratenic = no development takes place but parasite remains alive and infective to another host
How does intermediate host become definitive host
intermediate night developer and get eaten by paratenic host and becomes definitive
What are helminths and how is it caused
Helminthss are parasitic worms and are caused by contaminated food
How do parasites enter a host
Through broken ski;, mouth or elsewhere
Vector, sexually transmitted, contaminated meat
Definition of helminths. What are the 3 taxonomicakky important groups?
Term used to refer to parasitic worms
Namatkdes (roundworms)
Cestodes (tapeworms)
Trematodes (flukes)
What are the characteristics of helminths
Highly complex parasites and infecti9ns
- infects orally through the skin or by vectors bite
- infect a range of different tissues and organs (often migrate)
- often long term chronic infections
- don’t proliferate in host (usually release eggs into faeces of urine)
What are intestinal helminth’s symptoms
Abdominal pain diarrhoea, malnutrition, protein deficiency, iron deficiency anaemia, growth reduction, neurological problems
What are the challenges of combating helminths infections
- good at evading and suppressing host immunity
- long lived - can live up to 10 years bc they dint wanna kill their host
- large size ( hard for immune system to kill)
- takes decades to develope immunity and protective memory
Characteristics of trichuris trichiura whipwirm roundworm
Intestinal nematode
Forms close associations with host intestinal epithelial cells
Life cycle of filarial worms
Larvae excreted and transmitted into black fly, matures in insect and insects into human, oathology causes lizard skin and human is the definitive host
Characteristics of taenia solium (tapeworm/cestode)
Egg released within stool which is eaten up by pigs. Parasite moves to pig muscles and is eaten by human (undercooked pork)
How does cysticercosis develop due to taenia solium?
Eggs develop into larvae in the guts penetrate intestinal wall and en cyst in muscle and CNS. symptoms can include brain and spinal cord pathologies (diszzinessm seizures epilepsy)
Characteristics of schistosoma spp. - trematode
One of the few helminths where pathology is caused in large numbers of people. Parasite lives in veins, eggs migrate to get out of host. Release in the water urine
What are the characteristics of schistosomiasis
Chronic infection can result in inflammatory reactions towards the eggs. Egg may get trapped in the liver causing fibrosis
Eggs that migrate to CNS may cause seusures paralysis or spinal cord inflammation
What are symptoms of female genital schistosomiasis
Damage to reproductive organs (vaginak dischagr, blood in ruined abdominal and pelvic pain)
Leads to infertility, ectopic pregnancy, genictal ulcers
What are the severe clinical outcomes of:
Trichuris trichiura
Onchocerca volvulus
Taenia solium
Rectal prolapse
Blindness
Epilepsy
