(PM3A) Parasitic Infection + Anti-Parasitic Drugs Flashcards
How does a parasite meet its nutritional needs?
Prolonged contact with another living organism
What is an example of a unicellular parasite?
Protozoa
What is an example of a multicellular parasite?
Helminths
What are the two classes of parasites?
(1) Endoparasites
(2) Ectoparasites
What are examples of endoparasites?
(1) Protozoa
(2) Helminths
What are examples of ectoparasites?
(1) Lice
(2) Leeches
(3) Scabies
(4) Fleas
What are the main anti-protozoal drugs?
(1) Anti-amoebics
(2) Anti-malarials
(1) What is the mechanism of action for pyrimethamine?
(2) What is pyrimethamine?
(1) Inhibits DHFR
(2) Anti-protozoal drug
(1) What is mechanism of action for sulphadiazine?
(2) What is sulphadiazine?
(1) Inhibits DHPS
(2) Anti-protozoal drug
What is the mechanism of action of doxycycline?
Inhibits protein synthesis in 30S ribosomes
What are the main anti-helminth drugs?
(1) Anti-nematodes
(2) Anti-cestodes
(3) Anti-trematodes
Name 3 common anti-helminth drugs: m p n
mebendazole
praziquantel
niclosamine
What is the mechanism of action of mebendazole?b ms gu
(1) Binds to beta-tubulin in intestinal cells of nematodes
(2) Prevents microtubule synthesis
(3) Leads to block of glucose uptake
What is the mechanism of action of praziquantel?ca mp
(1) Increases membrane permeability to Ca2+
(2) Leading to contraction of muscle and paralysis
What is the mechanism of action of niclosamine?
(1) Uncouples oxidative phosphorylation
(2) Prevents ATP synthesis
What are protozoa?
- Unicellular
- Eukaryotic organisms
- Can use insect/ water vectors
Give examples of protozoal infections.
(1) Malaria
(2) Intestinal infections - amoebic dystentery/ toxoplasmosis
How is a malaria infection diagnosed?
(1) Blood film microscopy
(2) Antigen-based rapid diagnostic tests (RDT)
What are the stages of malaria transmission?
(1) Mosquito bites + injects sporozoites
(2) Infects liver cells
(3) Development of a schizont.
(4) Schizont ruptures
(5) Releases merozoites -> Infect erythrocytes -> Immature trophyzoites
(6) Some immature trophozoites mature to develop more schizonts
(7) Some generate gametocytes - which are ingested by mosquitos
What is a schizont?
A protozoan cell which divides to form daughter cells
What are the symptoms of malaria?
- Fever/ chills/ sweats
- Headaches
- Nausea + vomiting
- Aches
- Malaiase
What can severe malaria cause?
- Cerebral malaria
- Organ damage
- Metabolic damage
How can malaria be prevented?
(1) Anti-malarial drugs
(2) Covering
(3) Mosquito nets
(4) Permethrin - insecticide
(5) Vaccine
What are the main malaria prophylaxis medications in the UK?
(1) Doxycycline
(2) Mefloquine
(3) Proguanil + atovaquone (Malarone)
What is 1st choice treatment for P. falciparum malaria?
(1) Clindamycin
(2) Proguanil + atovaquone (Malarone)
What is the 1st line treatment for malaria in pregnancy?
Quinine + clindamycin
What does malaria have widespread resistance to?
(1) Chloroquinine
(2) Anti-folates
What is amoebic dysentery?
Amoebiasis
Infection of amoeba
fecal oral transmission
Causes diarrhoea
What is the treatment for amoebic dystentery (amoebiasis)?m
Often self-limiting
Metronidazole - for acute invasive amoebiasis
When can a toxoplasmosis infection be life-threatening?
If immunocompromised
What is the treatment for toxoplasmosis?
Often self-limiting
Pyrimethamine + sulphadiazine
What is cryptosporidiosis?
Parasitic infection
Causes diarrhoea
How is cryptosporidiosis transmitted?pl fs
(1) Swimming pools/ lakes
(2) Contaminated foods + surfaces
What are the symptoms of cryptosporidiosis?
- Watery diarrhoea
- Dehydration
- Weight loss
- Stomach cramps/ pain
- Fever
- Nausea + vomiting
When is cryptosporidiosis life-threatening?
If immunocompromised
What is the treatment for cryptosporidiosis?n
Usually self-limiting and not treated
Nitazoxanide if required
What are helminths? How many types are there? What are they?
Parasitic worms
3 types
(1) Cestodes
(2) Nematodes
(3) Trematodes
How are helminths transmitted?m cw f i
(1) Poorly cooked meat
(2) Contaminated water
(3) Faeces
(4) Insects - such as mosquito
Where are most species of helminth present?
Intestinal tract
What are subtypes of cestodes?
(1) Cestodaria - less common
(2) Eucestoda - more common
What is a scolex?
The head of a cestode
What are proglottids?
Body segment of a cestode
What are the common symptoms of a cestode infection?a ad d
(1) Upper abdominal discomfort
(2) Diarhhoea
(3) Loss of appetite
Often asymptomatic - Worm segments can sometimes be seen in stool
How is a cestode infection treated?
(1) Niclosamide
(2) Praziquantel
What is the cause of a threadworm infection?
Usually transmission of eggs
Faecal-oral
Eggs in faeces
How is a threadworm infection diagnosed?
(1) Seeing worms in perianal region
(2) Scotch tape test
- Sellotape around anus in morning
- Attaches worms & eggs to tape
How is a threadworm treated?
Mebendazole
Good hygiene
What is a threadworm?
Type of nematode
Type of helminth
Parasite
What is a hookworm?
Type of nematode
Type of helminth
Parasite
What are the symptoms of a hookworm infection?i d n i
(1) Iron-deficient anaemia
(2) Diarrhoea
(3) Nausea & vomiting
(4) Severe local irritation - from larvae in skin
What is the treatment for a hookworm infection?
(1) Cryotherapy
(2) Mebendazole - 100mg - BD - 3 days
How is a whipworm infection caused?
(1) Eggs hatch in the small intestine
(2) Eggs develop in the wall of the intestine
How length can a whipworm grow to?
50mm
2 inches
What are the symptoms of a whipworm infection?a bd
Light infestations - asymptomatic
Heavy infestations - bloody diarrhoea & iron-deficiency anaemia
How is a whipworm infection diagnosed?
Stool examination
Infestation is detectable in stool
What is the treatment for a whipworm infection?
Mebendazole - 100mg - BD - 3 days
What is another name for a roundworm?
Ascaricides
How many people worldwide are infected by roundworms?
1 billion
How long is a roundworm?
Up to 50cm long
What are the symptoms of a roundworm infection?a t p nd
(1) Often asymptomatic
(2) Peritonitis/ Inflammation/ Visceral damage
(3) Enlargement of liver/ spleen
(4) Toxicity
(5) Pneumonia
(6) Nutritional deficiency
What are complications of a roundworm infection?
(1) Obstructed bowel - by a bolus of worms
(2) Obstruction of bile duct
(3) Obstruction of pancreatic duct
What is the treatment for a roundworm infection?
(1) Mebendazole - 100mg - BD - 3 days
(2) Mebendazole - 500mg single dose
What are the general treatments for nematodes?
(1) Good hygiene
(2) Anti-helminthics
- Mebendazole 100mg
What are the different types of fluke?
(1) Blood flukes
(2) Tissue flukes
- Liver fluke
- Lung fluke
Praziquantel can be used to treat
tissue fluke
blood fluke
lung fluke
What is/ are another name(s) for a blood fluke infection?
(1) Schistosomiasis
(2) Bilharziasis
What is different about schistosomicides to other trematodes?
Male and female
Other trematodes are not
What are the symptoms of schistosomiasis (bilharziasis)?
(1) Transient dermatitis - swimmer’s itch
(2) Dermatitis - abdominal pain - bloody stool - periportal fibrosis - hepatosplenomegaly - CNS effects
What is peri-portal fibrosis?
(1) Chronic disease
(2) Late-stage complication of schistosomiasis
(3) Due to presence of eggs in portal venules
What is hepatosplenomegaly?
(1) Disorder of spleen and liver
(2) Swelling of organ beyond normal size
What is a portal venule?
A division of the hepatic portal vein
What is the treatment for schistosomiasis (bilharziasis)?
Praziquantel - 20mg/kg - BD/ TDS
What is scabies?
Contagious skin condition where mites burrow into the skin
What is/ are the treatment(s) for head lice? How does it/ they work?
Dimeticone lotion/ liquid
- Suffocates lice - physical treatment
Wet combing
- Mechanical removal
What is the treatment for scabies?
Permethrin 5% cream - (Topical)
Ivermectin (Oral)