Parasitic Infections Flashcards
What are the targets of anti-parasitic drugs
Target rapidly proliferating young growing cells
Nucleic acid synthesis
Protein synthesis
Metabolic pathways eg folate metabolism
Detoxification mechanisms
What do anti-helminthic drugs target
Target non-proliferating adult organisms
Neuromuscular coordination
Carbohydrate metabolism
Microtubular integrity (needed for egg laying and hatching etc)
How is malaria diagnosed
Rapid diagnostic test
Microscopy
Thin and thick blood film
1% of malaria cases become severe. What are the complications of this
Cerebral malaria
Acidosis (respiratory distress)
Severe anemia
Greater mortality from 1st two
With cerebral malaria sequestration may occur in multiple organs such as brain, heart, GI tract, lungs, spleen and skin
Classes of drugs used to treat malaria
Quininines ( blocks parasite from detoxifying heme which is toxic)
Anti-folates (stop folate acid synthesis)
Artemisinin compounds ( generation of reactive radical species that interact with heme toxic)
Heme —> hemazoin normal reaction
What parasitic species causes African trypanosomiasis (sleeping sickness)
Trypanosoma Brucei Rhodesiense
Trypansoma brucei gambiense
Caused by the blood sucking tsetse fly
The parasites are found in blood, lymph and spinal fluid
What occurs during the 1st and 2nd stage of infection with sleeping sickness
In the first stage parasite is found in the peripheral circulation = unspecific symptoms
2nd stage = crosses BBB and causes neurological disturbances that result in coma and death
What drugs are used to treat sleeping sickness
- benznidazole (formation of free radicals that damages the parasites
- nifurtimox = creation of oxygen radicals
South American trypanosomiasis (chagas’s disease is caused by which parasite
Trypansoma Cruzi which infect blood sucking triatomine insects and are present in their faeces which can also contaminate food
How is Chagas’ disease treated and what happens when its not treated
If not treated is lifelong infection which presents as amastigote nests in the heart or parasites in GI tract leading to mega colon
Benznidazole
Nifurtimox
Which parasites cause leishmaniases disease
Leishmania Donovani
L. Infantum
L. Major
L.Braziliensis
L. Mexicana
L. Ethiopica
Transmitted by the bite of an infected phlebotomine female sandfly
What types of leishmania is there
Asymptomatic
Cutaneous leishmaniasis
Visceral leishmaniasis
Mucosal leishmaniasis
Drugs currently used to treat leishmaniasis
Pentavalent antimony
Amphotericin B
Miltefosine
Toxoplasmosis
Caused by toxoplasma Gondii and is found worldwide
Continental toxoplasmosis —> abortion or hydrocephalus
Drugs used to treat toxoplasmosis
Anti-folates
Pyrimethamine
Sulfadiazine
What intestinal protozoans cause amoebiasis and giardiasis
Amoebiasis is caused by entamoeba histolytica
Is distributed around the world and maybe asymptomatic = luminal amebiasis
Giardiasis is caused by giardia lamblia
What are the clinical manifestations of invasive intestinal amebiasis?
Dysentery, colitis, appendicitis, toxic megacolon
What are the clinical manifestations of invasive extra intestinal amebiasis
Liver abscess, peritonitis, cutaneous and genital amebic lesions
Amoebiasis, giardiasis and trichomoniasis can be treated by ….
all parasitic infections
first two cause diarrhoea
Metronidazole
Tinidazole
= DNA damage +inhibition of DNA repair
Helminths can be classified in three groups
Tapeworms/ cestodes such as taenia
Flukes/Trematodes such as schistosoma
Round worms/nematodes such as ascaris, necator (hookworm), whip worm, onchocerca volvulus, dracunulus medinesis, filarial roundworms
All above infect by their eggs/larvae and adults do not replicate
Soil transmitted helminthiases such as ascaris, whipworm and hookworm are easily treatable by what….
Albendazole and mebendazole
These drugs result in loss of cytoplasmic microtubules
Disrupt motility and reputation and reduce uptake of glucose by parasites
Ascariasis: life cycle of a nematode
Larvae are ingested where they travel from intestine to portal circulation and then systemic to the lungs where they mature. Penetrate through alveolar walls and ascend upwards to the throat where they are swallowed into SI and develop into adult forms
Taeniasis is caused by which species of Cestode
Taenia solium
Taenia Saginata
Is usually asymptomatic but with severe infection causes diarrhoea and weight loss and pain
Treated with albendazole
Difference between taeniasis and larval cysticercosis
In taeniasis human ingests the larval cysts in contaminated pig meat whilst in the latter humans ingest eggs from contaminated human faeces. These eggs mature into larvae and migrate and form cysts in different parts of the body such as the brain where may cause seizures
What species of Trematode cause schistosomiasis and the host?
Schistosoma Mansoni
S. Hematobium
S. Japonicum
2nd most devastating parasitic disease
Host are freshwater snails
In chronic schistosomiasis where do the adult worms reside
In the blood vessels
Eggs can travel to the intestine and bladder
Symptoms associated with disease are caused by body’s reaction to the eggs —> inflammation
Which drug is used to treat schistosomiasis + MOA
Praziquantel
Causes severe spasms and paralysis of worms muscles
Lymphatic filariasis (elephantiasis) (nematode) and the drug that is used to treat this
Host?
Filarial roundworms that cause lymphoedema
Host is mosquitos that then infect humans
Adult worms have a long lifetime from 5-7 years and produce larvae.
Drug used to treat = diethylcarbamazine which is inhibitor of arachidonic acid metabolism and makes microfilariae more susceptible to attack by innate defences
Onchocerciasis (river blindness caused by a nematode)
What drug treats this condition and how it works
Transmitted through the bites of infected simulium black flies which breed in fast flowing rivers and streams
Chavrcteristed by blindness, nodules and skin rash and skin depigmentation
Drug= ivermectin activates glutamate gated Cl- ion channels that hyperpolarises muscles leading to paralysis
Echinococcosis (Hydatid disease) caused by a cestode
Adult worm only found in dogs
Eggs in faeces
In humans the larval cysts develop in different organs such as liver and lungs
Dracunculiasis (guinea worm disease) caused by a nematode
Caused by dracunculus medinensis
Migrates through the body’s subcutaneous tissues causing severe pain
Give examples of arthropods
Lice, scabies mites and fleas
Background information about scabies
Infestation of the skin by the human itch mite
Mite burrows itself into upper layer of skin where it lays its eggs
Symptoms = intense itching and pimple like rash
Spread through direct prolonged skin to skin contact
Worldwide disease
