Lecture 3A - Parasites and Viruses Flashcards
What forms can parasites adopt?
ectoparasits e.g. fleas, head lice
endoparasites - worms
singe cell - protozoa e.g. plasmodium species
viruses
What are endoparasites?
large multicellular parasites like worms
can invade and multiply inside the body and take up residence in tissue spaces
What are protozoa?
single celled organisms, which can spend part of their life cycle reproducing inside cells
What do viruses and prions need to reproduce?
the assistance of the intracellular metabolic machinery of the host organism
Cysticercosis?
1000 hospitilsations/year
Taenia solium tapeworm
makes it’s home in human tissue such as brain and muscles
Where are larval cysts of taenia solium found?
in uncooked pork
Chagas disease?
300,00 infections
leads to long term digestive, cardiac and neurological complications if not treated
What causes chagas disease?
trypanosoma cruzi (T.cruzi)
Trichomoniasis?
STD (3.7 million infected)
only 30% have symptoms of itching and burning with urination
What causes trichomoniasis?
protozoan - trichomonas vaginalis
Toxocara?
caused by larvae of roundworm found in guts of dogs and cats
can cause eye disease/blindness especially in children
What causes toxocara?
Toxocara canis or T. cati
50 million have antibodies
Toxoplasma gondii?
protozoan
from cat faeces
causes swollen lymph nodes, muscle aches and eye complications - can become chronic if not treated
What are ectoparasites?
live on the surface of a host but need some product from(nutrient or genetic material) in order to survive (often a blood meal)
What can ectoparasites do when taking a blood meal?
inject viruses, protozoans and bacteria along with some form of anti-coagulant into the human subject
Where do endoparasites live?
inside the body
Examples of ectoparasites?
head lice
ticks (vectors for chagas disease, lyme disease)
mites
fleas
Headlice?
pediculus humanus capitis
wingless insects very common in school children aged 4-11
How is head lice transferred?
by head to head contact
How do head lice attach to the host?
the female cements pinhead sized eggs to hairs near to the root where the scalp keeps them warm
How long does it take head lice to hatch?
around 9 days (white nit stage), but they initially remain attached to the hair, later they begin feeding
How do head lice feed?
by biting the scalp and drawing blood
in another 9-10 days they are fully mature and the females are able to lay more eggs
How can head lice be treated?
by combing (0.2-0.2mm comb) or lotions
Body lice?
pediculosis corpis
Pubic lice?
phthirus pubis
Where do body/pubic lice live?
they live and feed on specific skin regions
What are mites?
arachnids
Sarcoptes scabei?
mite that causes scabies - female burrows into the skin and lays eggs
Dermatophagoides pteronyssinus?
dust mite
lives off dead skin and causes dermatitis and asthma
Ticks?
also arachnids
live on the skin and feed off blood
What do ticks act as?
vectors for many serious illnesses in humans and animals
Fleas?
wingless insects with an extraordinary ability to jump
eggs may hatch in carpets for more than a week before the flea hatches and jumps onto the skin of the host for a blood meal
What can lice transmit?
typhus
can be transmitted in clothing or reside there between baths
What can ticks transmit?
chagas disease and lyme disease
Size of fleas?
1.5 to 3mm long, but can jump vertically 18cm and horizontally 33cm
