Parasites and Viruses

Where are ectoparasites located?

What are ectoparasites?

• outside the body

• large complex multicellular organisms

Where are endoparasites located?

Inside the body

Are ectoparasites and endoparasites uni or multicellular organisms?

What do parasites require humans for?

• ecto = multicellular, endo = unicellular or multicellular

• rely on humans to get nutrients to survive and reproduce

How is head lice transferred amongst people?

Is it an ecto or endoparasite?

• transferred from head to head (doesn’t jump)

• ectoparasite

How long does it take for lice eggs to hatch?

What colour are the baby lice?

How long does it take for the lice to fully mature?

• 9 days

• white

• another 9-10 days until the females can lay more eggs

What symptoms does head lice cause?

• cause inflammation and irritation

Is scabies ecto or endoparasite?

What is scabies?

• ectoparasite

• when small mites burrow into the skin (near the surface), results in an itchy pimple-like rash

What are treatments for scabies?

• ivermectin, permethrin - often given to the entire household (not just person with symptoms)

• also decontamination of clothing and bedding

What are common ectoparasites?

• headlice, scabies mites, ticks, body lice, pubic lice, fleas

Can parasites act as vectors for other bacteria and viruses?

• yes e.g. ticks carry Lyme disease

Why is a mosquito considered a vector?

What measures can help to manage the spread of vectors?

• because they carry and transmit diseases (parasites, infections etc.)

• insect repellant

What diseases can mosquitos spread?

What diseases can ticks spread?

What diseases can fleas spread?

What disease can sandflies spread?

• malaria, dengue, yellow fever, zika, chikungunya or elephantiasis

• Lyme disease, typhus and encephalitis

• plague

• leishmaniasis

Why are parasitic worms hard to treat?

• because they grow so much

How do people get infected by roundworms?

• either acquired orally or through skin, transmitter via faeces

What is the lifecycle of a tapeworm?

What is a difference between intestinal and extraintestinal nematodes?

Where do extraintestinal larvae mature and sexually reproduce?

How do extraintestinal nematodes get transmitted to humans?

• extraintestinal are tiny when adult stage, while intestinal are massive (tapeworm)

• mature in specific tissues in the body after vector transmits into human, sexually produce microfilariae

• through vectors taking a blood meal

What is the life cycle in schistosomiasis (flukes - flatworms)?

• eggs are released via faeces/urine into water

• parasite taken up by snails

• snail releases larva (called cercaria) which penetrates skin 

• infects people coming into contact with infected water

What is a protozoan?

Are they extra or intracellular?

• single cell eukaryote than can asexually reproduce in large numbers inside human hose

• both - can live in blood or in cell tissue

What are examples of insect-borne protozoal infections?

• trypanosoma (also called sleeping sickness) - vector is tsetse fly

  • resides in blood then either CNS or heart

  • causes brain infection and neuronal damage (hence why sleeping sickness)

• leishmania - vector is sand fly

  • resides intracellularly in macrophages - evades immune system

  • causes skin sores, lysis of WBC

• plasmodium - vector is mosquito

  • causes malaria

Why is malaria so dangerous?

• untreated, results in chills fever and destruction of red blood cells (due to parasite growing in RBCs (intracellular protozoan infection))

What is the life cycle of malaria parasite?

1 human and 2 mosquitos for life cycle.

MOSQUITO 1

Sporozoite- the form that is injected from the mosquito. Thread-like. Reside in mosquito salivary gland

HUMAN

Rapidly move to the liver and form a cyst (dormant to erupt later) others go into liver cells and divide rapidly forming up to 1000 newly formed parasites. Burst open from hepatocytes. Merozoites are now ready to infect RBC. Hoover up nutrients, divide again, burst cell (causes anaemic). Release secretory granules, and processed haemoglobin. These cause fever.

HUMAN/MOSQUITO 2

Merozoites can reinfect RBC (cyclical amplification and outbreak of fever). These are then ingested in mosquito blood meal and the cycle continues

What are viruses?

What do they possess?

What do they need to reproduce?

• are organisms with active and dormant phases

• possess they’re own genetic info

• need ribosomes to reproduce (don’t have their own) - require a host

What is characteristic of virus structure?

• have genetic info encased in a capsule - is symmetrical

Can viral genomes have DNA and RNA?

• yes and can be double or single stranded, linear or circular.

How does viral replication work?

• attaches, then penetrates cell, synthesis of nucleic acid and protein

  • RNA viruses use reverse transcriptase (think HIV and other retroviruses_

• Assembly and packaging 

• Maturation

• Release

How do normal and diseased prions differ structurally?

• protein is faulty/changed, leading to the structure of it being misaligned

• normal prion has no beta sheets, while diseased prion has high beta sheet count

Why are prions so fatal?

• cause neurodegeneration

Do prions contain nucleic acid?

• no, are composed entirely of a modified (faulty) protein

What are examples of prion diseases?

• scrapie

• bovine spongiform encephalopathy

• cretuzfeld-Jakob disease

• kuru

• PrP cerebral amyloid angiopathy

What are differences in normal and diseased prions (more physiologically)?

• normal = monomeric and soluble, protease sensitive and neuroprotective - only made up of 3% beta sheets

• diseased = aggregated, insoluble, partially protease resistant, infectious and toxic (kills cells) - high beta sheet count

What is the Latin name for body lice?

• Pediculosis corporis

What is the Latin name for pubic lice?

• Phthisis Pubis

What is the Latin name for head lice?

• Pediculus Humanus Capitis

What is the Latin name for Scabies?

• Sarcoptes Scabei

What type of parasite is trichinella?

What is it present in?

• extraintestinal nematode (roundworm)

• present in infected meat and cysts in the muscle

What type of parasite is guinea worm?

What is the Latin name for it?

What does it affect?

• extraintestinal nematode (roundworm)

• Dracunculus

• affects the skin

What is the Latin name for tape worm?

• Taenia Solium

What are examples of waterborne protozoal infections?

• Giardia lamblia

• Entamoeba histolytica

• trichomonas

What does trypanosoma cause?

• sleeping sickness and can cause neuronal damage if protozoa infects the brain

• can also infect the heart (either infects brain or heart → depends on the species

What does Leishmania cause?

Where does Leishmania reside?

• causes skin sores

• resides in intracellular macrophages → evades detection

Where does plasmodium protozoal infection reside in the body?

What can this result in?

• in the RBCs

• eruption of RBC → due to malaria growing in it (can lead to death)

What is the most common and most dangerous species of Plasmodium?

• Plasmodium Falciparum

What species of plasmodium is most prevalent in South America?

• Plasmodium Malariae

What is the rarest species of Plasmodium?

• Plasmodium Vivax