Introduction to medically Important Parasites Flashcards
Parasitic disease where a vaccine is available:
Malaria, available for people in areas where malaria is endemic
Which country has the highest incidence of the roundworm strongyloides?
Australia
What are parasites?
Eukaryote pathogenic or commensal organisms
What is the problem with eukaryotic parasite diseases?
They are very similar to human cells so drugs can be toxic to humans as well
What are direct parasite life cycles?
Only one host in life cycle
What are indirect parasite life cycles?
Two or more hosts required
What are the types of parasite life cycles?
Direct
Indirect
They can undergo both sexual and asexual reproduction (usually in definitive host)
What are the types of hosts that parasites can live in?
Definitive/primary host
Reservoir host
Secondary/intermediate host
What are the modes of transmission of parasite infections?
Direct
Food/water borne
Via vector/intermediate host
What happens in the intermediate host?
Can be just mechanical transmission or several important life-cycle stages can take place here.
What is the efficacy of the RTS,S/AS01 (Mosquirix) vaccine?
26%
What is leishmanisation?
Inoculating live parasites in the buttock to prevent leishmaniasis disease
What are the types of disease causing parasites?
Single celled
Intracellular
Extracellular
What type of evolution was required for pathogenic parasites to form?
Co-evolution
What is the most common protozoan parasitic disease?
Trichomonas vaginalis (200 million cases detected worldwide)
What kind of condition does Trichomonas vaginalis cause?
An STD
What kind of pathogens are acanthamoeba and naegleria fowleri?
Protozoan parasites causing uncommon but deadly conditions.
What is the disease caused by naegleria fowleri called?
Primary amoebic encephalitis
What is the survival rate of naegleria fowleri infection?
No one has survived it (95% fatality even with treatment) Very rare with 340 cases recorded since the 1960s
What common parasites are water borne?
Giardisis (relatively benign)
Toxoplasmosis (also benign and present in a huge percentage of the population)
Amoebiasis
Blantidiasis
Cryptosporidiosis
What common parasites are caused by vector borne protozoan infections?
Malaria
Babesiosis
Leishmaniasis
Chagas disease caused by Trypanosoma cruzi
Sleeping sickness (trypanosoma brucei gambiensie/rhodesiense)
What measures must be taken with systemic helminth infections and why?
To use immunosuppression due to the immunogenic nature of helminth infections. Helminths are also eukaryotes which means drugs are toxic
How long do helminths stay in the body for?
They can survive for decades
What are the types of helminth infections?
Nematodes (round worms)
Platyhelminths (flat worms) - Cestodes (tapeworms) and trematodes are the disease causing subgroups.
Possible benefits to helminth infections:
Hygeine hypothysis. (infection with helminths at young age associated with protection from atopic illnesses like asthma and Irritable Bowl Disease)
What is caenorhabditis elegans?
A nematode that is possibly one of the most important nematodes for medicine due to its use in research.
How is caenorhabditis elegans used?
It is transparent and emits blue/green light.
What is the second largest phylum in the animal kingdom?
Nematodes (25000 species discovered and 1 million predicted to exist)
What parts of the body do helminths commonly cause infections in humans?
GI tract (eg hookworms)
Tissue or blood (eg Filarial worms)
What kind of nematode infections are most common?
GI infections
How many people have GI nematode infections?
3.5 billion people (450 million seriously ill)
125000 deaths per year and 39 million DALYs
Do GI tract infecting nematodes have intermediate hosts?
No they are direct parasites
What is the most common cause of GI nematode infections?
Ascaris lumbricoides (~3000 deaths/yr)
What GI nematodes cause infections in humans?
Ascaris lumbricoides
Hookworms
Trichuris trichura
Strongyloides stercolis
Enterobius vermicularis
What kind of infection does enterobius vermicularis cause in humans?
Commonly infects children globally and causes itch on buttocks
Which worm is expected to be eradicated next?
A tissue infecting nematode worm called guinea worm (Dracunulus medinesis)
in 1986 there were 3.6 million cases and in 2015 only 22 cases
What are the filarial worms that cause infection in people?
Lymphatic filiariasis
Trichinella spiralis (only intracellular helminth)
What are the types of tissue infecting nematodes?
Filarial worms such as lmyphatic filiariasis and trichinella spiralis
Guinea worm
Toxocara canis
What kind of infection does toxocara canis cause?
Worm often targets the eye
How do tapeworms attach to the gut?
Via scolex
What mode of reproduction do tapeworms use?
They are hermaphrodites and reproduce by sexual reproduction
What are tapeworm bodies composed of?
Segments or proglottids
What does the tissue tapeworm echinococcus multilocularis do?
It is a parasitic infection that acts very similarly to cancer
What common Intestinal tapeworm is obtained from consuming pork?
Taenia solium
What are the types of tapeworms?
Tissue and intestinal.
Intestinal tapeworms can also form cysts in tissues
What common Intestinal tapeworm is obtained from consuming beef?
Taenia saginata
Are flukes also haemaphrodites?
Yes with the exception of schistosomes which are dioecious
What are the types of blood flukes?
Schistosoma mansoni (gut)
Schistosoma haematobium (bladder)
Schistosoma japonica (gut)
These organisms can produce growth factors which is why some cancers can arise from these parasites (eg bladder cancer from schistosoma infection)
What are the types of tissue flukes?
Most infect liver and lungs.
Fasciola hepatica
Clonorchis (opisthorchis) sinensis
Opisthorcus viverrini
Paragonimus westermani
Why are helminth treatments so underdeveloped?
The diseases are more prevalent in the tropics and so drug companies cannot make profit making drugs for these diseases.
Helminths are eukaryotic so drugs are often toxic
What treatment is used for sleeping sickness?
Malarsoprol which is deadly in 8% of patients and contains ‘arsenic dissolved in antifreeze’ (this drug is used for stage 2 of the disease)
Eflornithine treats 1 of the 2 causes of the disease rater harmlessly.
What drugs are used for chagas disease?
Only 2 drugs available to treat chagas, in the 1990s Bayer decided that one of them was not profitable and withdrew it from production (Niturtimox)
The drugs only work in the first 2 - 4 weeks
What drug is used to treat leishmaniasis?
Pentavalent animony first used in 1930s and is the first choice drug for most cases
