Parasitic Infections Flashcards
Define parasite.
An organism living in or on a host + 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?
Protozoa
Unicellular Eukaryotes (membrane bound nucleus)
Some have insect vectors
NO eosinophilia
Metazoa AKA Helminths/worms
MULTIcellular
Free living, intermediate hosts + vectors
Cause eosinophilia if they invade the blood
State the classes of organisms within the two groups of endoparasites.
Protozoa: Amoeba, Coccidia, Ciliates + Flagellates
Metazoa: Roundworms, Flatworms + Flukes
Give 2 examples of amoeba.
Entamoeba histolytica
Entamoeba dispar
Give 3 examples of coccidia.
Plasmodium species
Toxoplasma
Cryptosporidium
Give an example of a ciliate.
Balantidium coli
Give 4 examples of flagellates.
Trypanosoma
Trichomonas
Giardia
Leishmania
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. What symptoms result from infection?
Cysts enter the small intestine + 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
Result: asymptomatic, diarrhoea, amoebic liver abscess
What are the treatment options for amoebiasis?
Nitroimidazole derivatives (kills trophozoites, not cysts) Parmomycine or Diloxanide Furoate
Give 2 examples of plasmodium that cause malaria
Falciparum
Malariae
What are the two types of host for plasmodium?
Human
Female anopheles mosquito
What are the two stages of malaria in humans?
Liver
Blood
Describe the symptoms of malaria.
PAROXYSMAL (cycle 4-8 hours) Fever Chills Headaches Vomiting Muscle pain
State 2 serious complications of malaria.
Severe anaemia (due to intravascular haemolysis) Cerebral malaria
What is the treatment for uncomplicated malaria?
What is the treatment for severe malaria?
Chloroquine
Severe: Artemisinin-based combination therapy
What are the 4 routes of infection of toxoplasma gondii?
Eating undercooked meat of animals harbouring tissue cysts
Consuming food or water contaminated with cat faeces
Blood transfusion + Organ transplantation
Transplacentally from mother to foetus
Which group of patients are particularly vulnerable to toxoplasma infection? What can toxoplasma infections cause in these individuals?
Immunocompromised Fever, headache, swollen lymph nodes CNS disease Brain lesions Pneumonitis
What does cryptosporidium cause?
DIARRHOEA (mainly in the immunocompromised)
Fever
Nausea + vomiting
How is cryptosporidium treated?
Fluid rehydration
How are most diarrhoeal protozoal diseases diagnosed?
Stool examination
What are the reservoirs of balantidium coli?
Primates
Rodents
Pigs
What are the 5 effects of balantidium coli infection in immunocompromised patients?
Persistent DIARRHOEA Dysentery Abdominal pain Vomiting Nausea
How can drinking water be cleared of ovoid giardia lamblia cysts?
Filtration
Ovoid cysts can survive standard chlorination procedures
What is the main symptom of giardiasis? What are the acute symptoms of giardiasis?
DIARRHOEA Greasy stools Abdominal cramps Nausea/vomiting Dehydration
How is giardia transmitted?
Faeco-oral
How is trichomonas transmitted? Where does trichomonas infection mainly tend to reside?
Sexually transmitted
Urethra
What are the symptoms of trichomoniasis?
Dysuria
Vulval itching
Vaginal discharge
Offensive smelling urine
What are the potential complications of trichomoniasis infections?
Detrimental outcome on pregnancy, association with preterm delivery + LBW.
Enhances HIV transmission
Can adult worms multiply in man?
No
In which subset of the population is there a significant burden of worms?
School-aged children – has a massive impact on their development
What are the three groups of Helminths? Give some examples of each.
Roundworms: Ascaria, Hookworms, Filaria + Strongyloides
Flatworms: Taenia (tapeworms)
Flukes: Schistosoma
Where do the adult ascaria worms live? How long can adult ascaria live?
Small intestine
1-2 years
Describe the symptoms of ascariasis.
Often asymptomatic
Many worms = abdominal pain
Malnourishment (as worms feed on contents of small intestine)
Loeffler’s pneumonia: penetration of larvae into lungs leads to pools of blood + epithelial cells clogging the airspaces
How are most helminth infections diagnosed?
Stool examination
Where do adult hookworms live?
Small intestine
What is a key feature of hookworm infection and what is this caused by? What other symptoms may present?
Iron deficiency anaemia: caused by localised bleeding in the small intestine
GI + respiratory symptoms
What is the biological name whipworm? Where do adult whipworms live?
Trichuras trichiura
Caecum + ascending colon
What are the symptoms of whipworm infection?
Bloody diarrhoea + anaemia (due to severe vitamin + iron loss)
What is a potential therapeutic use of whipworms?
Helminth therapy for allergies + AI diseases
What are the two forms of lymphatic filaria? What do both cause?
Brugia malayi
Wucheria bancrofti
Obstruction of lymphatics
Describe the location of microfilariae in the blood. How is filariasis diagnosed?
Peripheral blood at night
Deep veins during the day
Blood smear
Which disease caused by filaria presents with worms in the eye?
Loiasis
What is the insect vector in Loiasis?
Chyrops fly
What are the three main types of flatworm for which humans are the only definite host? Which tends to cause more symptoms?
Taenia solium
Taenia asiatica
Taenia saginata (more symptoms)
Describe the symptoms of flatworm infection.
Most are asymptomatic
Abdominal pain
Weight loss + Loss of appetite
Upset stomach
How is flatworm infection diagnosed?
Stool examination – presence of tapeworm segments/ eggs
What important condition does Taenia solium cause? What can this lead to?
Cysticercosis
Acquired epilepsy
What are the three main types of schistosoma?
Schistosoma mansoni
Schistosoma haematobium
Schistosoma japonicum
Describe 5 symptoms of schistosomiasis.
Rash or itchy skin Fever Chills Cough Muscle aches Most are asymptomatic in early stages of infection
Name 4 ectoparasites.
Sarcoptes scabiei – Scabies (causes rash)
Pediculus humanis capitis (head louse)
Pediculus humanis corporis (body louse)
Pthirus pubis (crab louse)
How are ectoparasites transmitted?
Direct contact
Define infection
invasion by + growth of pathogenic microorganisms within the body
Define disease
disordered functioning of the body resulting from the effect of genetics, infections, poisons etc
