Flashcards in Parasitic Infections Deck (82)
An organism living in or on a host and dependent on the host for nutrition – causing damage
What is the difference between an endoparasite and an ectoparasite?
Endoparasite – exist INSIDE the host
Ectoparasite – exist on the host
What are the two groups of endoparasites and what are the features of organisms within these two groups?
State the classes of organisms within the two groups of endoparasites.
Give some examples of amoeba.
Give some examples of coccidia.
Give an example of a ciliate.
Give some examples of flagellates.
What is the main difference between the two types of amoeba?
Entamoeba histolytica can cause invasive amoebiasis
Entamoeba dispar is a normal commensal of the GI tract
What is amoeba infection caused by?
Ingestion of mature cysts in food or water contaminated by faeces
Describe how E. histolytica infection causes disease.
The cysts enter the small intestine and release active amoebic particles (trophozoites), which invade the epithelial cells of the large intestines, causing flask-shaped ulcers
Infection can spread from the intestines to other organs
Invasive amoebiasis may often cause amoebic liver abscesses
How many nuclei are there in mature cysts?
What are the treatment options for amoebiasis?
Nitroimidazole derivatives (kills trophozoites but not the cysts)
Parmomycine or Diloxanide Furoate
What are the five types of plasmodium that cause malaria?
What are the two types of host for plasmodium?
Female anopheles mosquito
What are the two stages of malaria in humans?
Describe the symptoms of malaria.
PAROXYSMAL (occurs every 4-8 hours)
State some complications of malaria.
Severe anaemia (due to intravascular haemolysis)
Abnormally low blood sugar
Swelling and rupturing of the spleen
What are the treatments for uncomplicated malaria?
What is the treatment for severe malaria?
Artemisinin-based combination therapy
How is malaria diagnosed?
Blood film (+ Giemsa stain)
What are the routes of infection of toxoplasma gondii?
Eating undercooked meat of animals harbouring tissue cysts
Consuming food or water contaminated with cat faeces
Transplacentally from mother to foetus
Which group of patients are particularly vulnerable to toxoplasma infection?
Immunocompromised and in pregnancy - the fetus
What can toxoplasma infections cause in immunocomprimised individuals?
What does cryptosporidium cause?
DIARRHOEA (mainly in the immunocompromised)
How is it treated?
How are most diarrhoeal protozoal diseases diagnosed?
What are the reservoirs of balantidium coli?
What are the effects of balantidium coli infection in immunocompromised patients?
If left untreated can cause perforation of the colon
How can drinking water be cleared of ovoid giardia lamblia cysts?
Ovoid cysts can survive standard chlorination procedures
What is the main symptom of giardiasis?
How is giardia transmitted?
What are the acute symptoms of giardiasis?
Greasy stools that tend to float
Stomach or abdominal cramps
What is the treatment for giardia?
Metronidazole - doesn't kill cysts only the trophozoites
How is trichomonas transmitted?
Where does trichomonas infection mainly tend to reside?
What are the symptoms of trichomoniasis?
Up to 50% aysmptomatic
Offensive smelling urine
What effect does trichomonas infection have on HIV transmission?
It enhances HIV transmission
What is the treatment for trichomoniasis?
Can adult worms multiply in man?
In which subset of the population is there a significant burden of worms?
School-aged children – this has a massive impact on their development
What are the three groups of Helminths(metazoa)? Give some examples of each.
Where do the adult ascaria worms live?
Describe the passage of ascaria larvae once they hatch in the small intestine.
Infective eggs are swallowed
The larvae hatch in the small intestine and invade the intestinal mucosa
They are carried via the portal and systemic circulation to the lungs
The larvae mature further in the lungs, penetrate the alveolar walls, ascend the bronchial tree and are swallowed
When they reach the small intestine, they mature into adult worms
How long can adult ascaria live?
Describe the symptoms of ascariasis.
Infections with a large number of worms can cause abdominal pain or intestinal obstruction
Malnourishment (because of worms feeding on contents of small intestine)
Loeffler’s pneumonia – penetration of larvae into lungs leads to pools of blood and epithelial cells clogging the airspaces in the lungs (resulting bacterial infections can be fatal)
What is the treatment for ascariasis?
Albendazole or Mebendazole
How are most helminth infections diagnosed?
Describe the passage of hookworm larvae across the body.
The same as ascaria
Where do adult hookworms live?
Attached by their buccal capsules to the villi of the small intestine
What is a key feature of hookworm infection and what is this caused by?
Iron deficiency anaemia – caused by localised bleeding in the small intestine
What is the treatment for hookworm infection?
Albendazole or Mebendazole
What is the biological name whipworm?
Where do adult whipworms live?
Caecum and ascending colon
What are the symptoms of whipworm infection?
Blood diarrhoea and anaemia (due to severe vitamin and iron loss)
Inflammation of intestinal wall
Can develop rectal prolapse
What is the treatment for whipworm infections?
Albendazole or Mebendazole
What is a potential therapeutic use of whipworms?
Helminth therapy for allergies and autoimmune diseases
What are the two forms of filaria?
Describe the location of microfilariae in the blood.
They are found in the peripheral blood at night
They are found in the deep veins during the day
How is lymphatic filariasis diagnosed?
Antigen detection with immunochromatic test (ELISA)
What is a distinguishing feature of Loiasis?
Female worms can get into the eye and cross under the conjunctiva so you see something wriggling in your vision
What is the insect vector in Loiasis?
What are the three main types of flatworm for which humans are the only definite host?
Describe the symptoms of flatworm infection.
Most people are asymptomatic
Loss of appetite
NOTE: people with T. saginata infection tend to have more symptoms
How is flatworm infection diagnosed?
Stool examination – tapeworm segments are found in the stool or identification of eggs in the stool
What important condition does Taenia solium cause?
Cysticercosis - commonest acquired cause of epilepsy worldwide
What is the treatment for flatworm infections?
What are the three main types of schistosoma?
What is the intermediate host in schistosoma?
Where do the adult worms live in schistosomiasis?
Where do the eggs progressively move to?
Small intestine (mansoni and japonicum)
Bladder and ureters (haematobium)
Describe the symptoms of schistosomiasis.
Possible rash or itchy skin
Most people have NO SYMPTOMS in early stages of infection
What is the treatment of schistosomiasis?
Name some ectoparasites.
Sarcoptes scabiei – Scabies (causes rash)
Pediculus humanis capitis (head louse)
Pediculus humanis corporis (body louse)
Pthirus pubis (crab louse)
How are ectoparasites transmitted?
What are the features of protozoa?
Eukaryotes (membrane bound nucleus)
Some have insect vectors
What are the features of metazoa?
They are helminths/worms
Free living, intermediate hosts and vectors
Cause eosinophilia if they invade the blood
Cycles involve insects vectors and intermediate hosts
For most - few zoonoses
What are the reservoirs of E. histolytica?
Humans are the only reservoir
What are the complications of Trichomoniasis
Detrimental outcome on pregnancy and is associated with preterm delivery and low birth weight
Organism living in or on the host and dependent on it for nutrition - causing damage
How do you get infected by a fluke cercaria?
Patient has to be in infected water so cercaria can penetrate the skin