5. Parasitic Infections Flashcards
Define infection and disease
- Infection – invasion by and growth of pathogenic microorganisms.
- Disease – a disordered or incorrectly functioning organ, part, structure or system of the body resulting from the effect of genetic or developmental errors, infection, poisons, nutritional deficiency or imbalance, toxicity, or unfavourable environmental factors; illness; sickness; ailment.
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 – single-celled organisms.
- Eukaryotic organisms – genome is within a nucleus/membrane bound nucleus, complex organelles.
- Causes of pathogenesis varies.
- Some have insect vectors.
- NO eosinophilia.
Metazoa – multi-cellular organisms:
- Free living, have intermediate hosts and vectors.
- Some just inhabit the gut (geo-helminths) whilst other invade tissues.
- Cause eosinophilia if they invade the blood.
State the classes of organisms within the two groups of endoparasites.
Protozoa – amoeba, coccidia, ciliate, flagellates.
Metazoa – roundworms, flatworms, flukes.
What are the forms of amoebae?
How does infection occur?
What is their epidemiology?
Forms:
- - Entamoeba histolytica – infects 10% of the world’s population – pathogenic in 10% of cases.
- - Entamoeba dispar – normal commensal of the GI tract.
Infection occurs by: ingestion of mature cysts in food or water, or on hands
Epidemiology:
- 3rd most common cause of death – after schistosomiasis and malaria.
- 90% of infections are asymptomatic.
- Incubation period is as short as 7 days; tissue invasion occurs during first 4 months of infectio
What is the life cycle and symptoms of amoebae?
How is it diagnosed and treated?
Life cycle and symptoms:
- Humans are the only reservoir.
- Cysts enter the small intestine and release parasites that invade epithelial cells and cause ulcers.
- Infection spreads via the venous system.
Diagnosis:
- -Wet mount – microscopy of cysts.
Treatment:
- Nitroimidazole derivatives, parmomycine or diloxanide furoate
What are the coccidia organisms and their associated diseases?
- Plasmodium species – malaria.
- Toxoplasma – toxoplasmosis – mild disease in immunocompromised – major for pregnancy!
- Cryptosporidium – diarrhoea (mild in immunocompetent, can be serious in immunosuppressed individuals)
What are the facts related to plasmodium species?
What are the symptoms, treatments and diagnosis of malaria?
Plasmodium species – malaria.
Facts:
- o 2 hosts include humans and female anopheles’ mosquito.
- o 2 stages in humans – liver and blood stages.
Symptoms
- – fever, headache, chills, emesis, myalgia.
- complications – severe anaemia, cerebral malaria.
Treatments – different treatments for severe and uncomplicated malaria.
Diagnosis – blood film and antigen detection tests.
What is toxoplasmosis caused by?
Toxoplasma – toxoplasmosis – mild disease in immunocompromised – major for pregnancy!
Toxoplasmosis gondii.
Caused by – infected food (warm-blooded animals with cysts or cat faeces contamination), blood transfusion, organ transplantation, trans-placentally to foetus.
What are the symptoms, diagnosis, and treatment of diarrhea caused by cryptosporidium?
Cryptosporidium – diarrhoea.
Symptoms – diarrhoea, fever, nausea, emesis. Very common in HIV patients.
Diagnosis – stool examination.
Treatment – fluid rehydration.
Give an example of ciliates and its associated disease
What are its reservoir hosts, symptoms, and diagnosis?
Organisms – Balantidum coli → balantidiasis.
Reservoir hosts – pigs, rodents, primates (infects people worldwide).
Symptoms:
- Most asymptomatic.
- Immunocompromised people – persistent diarrhoea, dysentery, abdominal pain, weight loss, nausea, emesis; all leading to perforation of the colon.
Diagnosis – stool examination.
Give examples of flagellates and their associated disease
What are its symptoms, diagnosis and treatment?
Organism – Giardia
Causes: giardia lamblia causes giardiasis.
Symptoms – diarrhoea.
Organism – Trichomonas:
- Transmitted sexually.
Symptoms:
- Females – 10-50% asymptomatic – vaginal discharge, vulval itching, dysuria.
- Males – 15-50% asymptomatic – discharge and/or dysuria.
- - May enhance HIV risk and is very bad for pregnant women.
Diagnosis and treatment – microscopy and metronidazole.
Organism – Leishmania – sand fly vector, 4 main types of Leishmania.
What are the classes of organisms within metazoa/helminths?
Give examples of each.
- Roundworms/Nematodes – Ascaris, hookworm, filaria, strongyloides.
- Flatworms/Cestodes – Taenia (tapeworms).
- Flukes/Trematodes – Schistosoma.
What is the lifecycle, symptoms, diagnosis, and treatment of ascariasis?
Ascariasis (roundworm/nematodes)
Life cycle:
- Live in the small intestine and eggs are passed with faeces.
- After infective eggs are swallowed, larvae hatch and invade the intestinal mucosa. They are carried via the portal and then systemic circulation to the lungs.
- The larvae mature in the lungs, penetrates the alveolar walls, ascends and is then swallowed.
- When they reach the small intestine, they develop into adults (live for 1-2 years).
Symptoms
- – often asymptomatic but can cause abdominal pain or intestinal obstruction.
- Adults feed on SI contents à malnourishment.
- Penetration of lungs can cause Loeffler’s pneumonia – pools of blood clog the lungs.
Diagnosis – stool examination.
Treatment – albendazole or mebendazole.
