Parasitic Infections Flashcards
Define parasite.
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?
Protozoa -Unicellular - Eukaryotes (membrane bound nucleus) - Some have insect vectors - NO eosinophilia Metazoa -MULTIcellular - They are helminths/worms - Free living, intermediate hosts and vectors - Cause eosinophilia if they invade the blood
State the classes of organisms within the two groups of endoparasites.
Protozoa 1. Amoeba 2. Coccidia 3. Ciliates 4. Flagellates Metazoa 1. Roundworms 2. Flatworms 3. Flukes
Give two examples of amoeba.
Entamoeba histolytica
Entamoeba dispa
Give some examples of coccidia.
Plasmodium species
Toxoplasma
Cryptosporidium
Give an example of a ciliate.
Balantidium coli
Give some 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.
-humans are only reservoir
- cysts enter the small intestine and release active amoebic particles (trophozoites), which invade the epithelial cells, causing ulcers
- Infection can spread from the intestines to other organs e.g. liver, lungs and brain
Invasive amoebiasis may often cause amoebic liver abscesses
How many nuclei are there in mature cysts?
4
What are the treatment options for amoebiasis?
Nitroimidazole derivatives (kills trophozoites but not the cysts) Parmomycine or Diloxanide Furoatep
What are the five types of plasmodium that cause malaria?
Falciparum Malariae Vivax Ovale Knowlesi
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.
PAROXYSM (occurs every 4-8 hours) Fever Chills Headaches Vomiting Muscle pain
State some complications of malaria.
Severe anaemia (due to intravascular haemolysis) Cerebral malaria Liver failure Shock Pulmonary oedema Abnormally low blood sugar Kidney failure Swelling and rupturing of the spleen
What are the treatments for uncomplicated malaria?
Chloroquine (look at notes for the rest of the treatment options)
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
Blood transfusion
Organ transplantation
Transplacentally from mother to foetus
Which group of patients are particularly vulnerable to toxoplasma infection?
Immunocompromised
Pregnant
What can toxoplasma infections cause in these individuals?
CNS disease
Brain lesions
Pneumonitis
Retinochoroiditis
What does cryptosporidium cause?
DIARRHOEA (mainly in the immunocompromised I/e v common in HIV patients)
How is it 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 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?
DIARRHOEA
How is giardia transmitted?
Faeco-oral
What is the treatment for giardia?
Metronidazole
How is trichomonas transmitted?
Sexually transmitted
Where does trichomonas infection mainly tend to reside?
Urethra
What are the symptoms of trichomoniasis?
Dysuria
Vulval itching
Vaginal discharge
Offensive smelling urine
What effect does trichomonas infection have on HIV transmission?
It enhances HIV transmission
What is the treatment for trichomoniasis?
Metronidazole
Can adult worms multiply in man?
No
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.
Roundworms (nematodes)
- Ascaria
- Hookworms
- Filaria
- Strongyloides
Flatworms (cestodes)
5. Taenia (tapeworms)
Flukes (trematodes)
6. Schistosoma
Where do the adult ascaria worms live?
Small intestine
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?
1-2 years
Describe the symptoms of ascariasis.
Often asymptomatic
- 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?
Stool examination
Describe the passage of hookworm larvae across the body.
The same as ascaria
Where do adult hookworms live?
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 for whipworm?
Trichuras trichiura
Where do adult whipworms live and what is their life cycle?
live in Caecum and ascending colon
- eggs hatch in SI and release larvae to to mature in colon
- worms leave open wounds that causes inflammation of intestinal wall
What are the symptoms of whipworm infection?
Blood diarrhoea and anaemia (due to severe vitamin and iron loss)
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?
Brugia malayi
Wucheria bancrofti
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?
Blood smear
Antigen detection with immunochromatic test (ELISA)
What is a distinguishing feature of Loiasis?
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?
Chyrops fly
What are the three main types of flatworm for which humans arethe only definite host?
Taenia solium
Taenia asiatica
Taenia saginata
Describe the symptoms of flatworm infection.
Most people are asymptomatic
T. saginata often experience more symptoms ;
-Abdominal pain
-Weight loss
-Loss of appetite
-Upset stomach
T. solium causes cysicerosis- most common cause of acquired epilepsy in the world
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
What is the treatment for flatworm infections?
Praziquantel
What are the three main types of schistosoma?
Schistosoma mansoni
Schistosoma haematobium
Schistosoma japonicum
What is the intermediate host in schistosoma?
Freshwater snails
Where do the adult worms live in schistosomiasis?
Venule
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 Fever Chills Cough Muscle aches Most people have NO SYMPTOMS in early stages of infection
What is the treatment of schistosomiasis?
Praziquantel
Name some ectoparasites.
Sarcoptes scabiei – Scabies (causes rash)
Lice:
1. Pediculus humanis capitis (head louse)
2. Pediculus humanis corporis (body louse)
3. Pthirus pubis (crab louse)
How are ectoparasites transmitted?
Direct contact
Define infection
invasion by and growth of pathogenic micro-organisms
Define disease
a disordered or incorrectly functioning organ, part, structure or system of the body resulting from the effect of genetic or developmental errors, infection, nutritional deficiency…
What is the life cycle of ectoparasites?
- Eggs
- Nymphs
- Adults
What are the hosts of the Taenia tapeworm?
Humans are the only definitive hosts for
T. solium and T. asiatica – pig
T. saginata – beef
How long can the loa loa worm live for?
4-12 years
What are the four major forms of Leishmania ?
- Visceral leishmaniasis (Kala azar)
- Cutaneous leishmaniasis
- Diffuse cutaneous leishmaniasis
- Mucocutaneous leishmaniasis
What is Visceral leishmaniasis (Kala azar) and what are some symptoms?
- most severe form, fatal if left untreated. Characterised by; 1. irregular fever, 2. weight loss 3. swelling of liver and spleen 4. anaemia
What is Cutaneous leishmaniasis and what are some symptoms?
- skin lesions on exposed body parts, often self-healing. – Can create serious disability and scars.
- Immunity to reinfection
What is Diffuse cutaneous leishmaniasis and what are some symptoms?
- disseminated lesions,
- resembles leprosy difficult to treat,
- no spontaneous healing,
- frequent relapses
What is Mucocutaneous leishmaniasis and what are some symptoms?
- disfiguring,
- destroys mucous membranes
What are the two forms of the Leishmania parasite?
- promastigote- sand fly vector- move in direction of flagellum
- amastigote- within human/vertebrate host- not motile
