Parasitic Infections

Question 1

What are the targets of anti-parasitic drugs

Answer 1

Target rapidly proliferating young growing cells

Nucleic acid synthesis
Protein synthesis
Metabolic pathways eg folate metabolism
Detoxification mechanisms

Question 2

What do anti-helminthic drugs target

Answer 2

Target non-proliferating adult organisms

Neuromuscular coordination
Carbohydrate metabolism
Microtubular integrity (needed for egg laying and hatching etc)

Question 3

How is malaria diagnosed

Answer 3

Rapid diagnostic test
Microscopy
Thin and thick blood film

Question 4

1% of malaria cases become severe. What are the complications of this

Answer 4

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

Question 5

Classes of drugs used to treat malaria

Answer 5

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

Question 6

What parasitic species causes African trypanosomiasis (sleeping sickness)

Answer 6

Trypanosoma Brucei Rhodesiense

Trypansoma brucei gambiense

Caused by the blood sucking tsetse fly

The parasites are found in blood, lymph and spinal fluid

Question 7

What occurs during the 1st and 2nd stage of infection with sleeping sickness

Answer 7

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

Question 8

What drugs are used to treat sleeping sickness

Answer 8

• benznidazole (formation of free radicals that damages the parasites
• nifurtimox = creation of oxygen radicals

Question 9

South American trypanosomiasis (chagas’s disease is caused by which parasite

Answer 9

Trypansoma Cruzi which infect blood sucking triatomine insects and are present in their faeces which can also contaminate food

Question 10

How is Chagas’ disease treated and what happens when its not treated

Answer 10

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

Question 11

Which parasites cause leishmaniases disease

Answer 11

Leishmania Donovani
L. Infantum
L. Major
L.Braziliensis
L. Mexicana
L. Ethiopica

Transmitted by the bite of an infected phlebotomine female sandfly

Question 12

What types of leishmania is there

Answer 12

Asymptomatic
Cutaneous leishmaniasis
Visceral leishmaniasis
Mucosal leishmaniasis

Question 13

Drugs currently used to treat leishmaniasis

Answer 13

Pentavalent antimony
Amphotericin B
Miltefosine

Question 14

Toxoplasmosis

Answer 14

Caused by toxoplasma Gondii and is found worldwide

Continental toxoplasmosis —> abortion or hydrocephalus

Question 15

Drugs used to treat toxoplasmosis

Answer 15

Anti-folates
Pyrimethamine
Sulfadiazine

Question 16

What intestinal protozoans cause amoebiasis and giardiasis

Answer 16

Amoebiasis is caused by entamoeba histolytica

Is distributed around the world and maybe asymptomatic = luminal amebiasis

Giardiasis is caused by giardia lamblia

Question 17

What are the clinical manifestations of invasive intestinal amebiasis?

Answer 17

Dysentery, colitis, appendicitis, toxic megacolon

Question 18

What are the clinical manifestations of invasive extra intestinal amebiasis

Answer 18

Liver abscess, peritonitis, cutaneous and genital amebic lesions

Question 19

Amoebiasis, giardiasis and trichomoniasis can be treated by ….

all parasitic infections
first two cause diarrhoea

Answer 19

Metronidazole

Tinidazole

= DNA damage +inhibition of DNA repair

Question 20

Helminths can be classified in three groups

Answer 20

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

Question 21

Soil transmitted helminthiases such as ascaris, whipworm and hookworm are easily treatable by what….

Answer 21

Albendazole and mebendazole

These drugs result in loss of cytoplasmic microtubules
Disrupt motility and reputation and reduce uptake of glucose by parasites

Question 22

Ascariasis: life cycle of a nematode

Answer 22

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

Question 23

Taeniasis is caused by which species of Cestode

Answer 23

Taenia solium
Taenia Saginata

Is usually asymptomatic but with severe infection causes diarrhoea and weight loss and pain

Treated with albendazole

Question 24

Difference between taeniasis and larval cysticercosis

Answer 24

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

Question 25

What species of Trematode cause schistosomiasis and the host?

Answer 25

Schistosoma Mansoni
S. Hematobium
S. Japonicum

2nd most devastating parasitic disease

Host are freshwater snails

Question 26

In chronic schistosomiasis where do the adult worms reside

Answer 26

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

Question 27

Which drug is used to treat schistosomiasis + MOA

Answer 27

Praziquantel

Causes severe spasms and paralysis of worms muscles

Question 28

Lymphatic filariasis (elephantiasis) (nematode) and the drug that is used to treat this
Host?

Answer 28

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

Question 29

Onchocerciasis (river blindness caused by a nematode)
What drug treats this condition and how it works

Answer 29

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

Question 30

Echinococcosis (Hydatid disease) caused by a cestode

Answer 30

Adult worm only found in dogs
Eggs in faeces

In humans the larval cysts develop in different organs such as liver and lungs

Question 31

Dracunculiasis (guinea worm disease) caused by a nematode

Answer 31

Caused by dracunculus medinensis
Migrates through the body’s subcutaneous tissues causing severe pain

Question 32

Give examples of arthropods

Answer 32

Lice, scabies mites and fleas

Question 33

Background information about scabies

Answer 33

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