Parasitic infections Flashcards
Infection
Invasion by and growth of pathogenic microorganisms within the body
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
Parasite
Organism living in or on the host and dependent on it for nutrition=causing damage
Endoparasites
- Protozoa: amoeba, coccidiae, ciliated, flagellates
- Metazoa: roundworms, flatworms, flukes
Ectoparasites
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Protozoa
ENDOPARASITE
- single celled organisms
- eukaryotes (genomw within nucleus, complex organelles in cytoplasm)
- pathogenesis (mechanism of disease) varied
- some have insect vectors (eg: malaria)
- no eosinophilia
Metazoa
ENDOPARASITE
- multicellular organisms
- free living, intermediate hosts and vectors
- some just inhabit gut (geohelminths), others invade tissues
- eosinophilia (if they invade blood)
Types of protozoa
- Amoebae
- Coccidia
- Ciliates
- Flagellates
Amoebae
Forms:
- entamoeba histolytica
- entamoeba dispar
Coccidia
-Coccidial infection in humans are mostly zoonoses
Lab diagnosis of amebiasis
WET MOUNT
Symptoms of malaria
- fever
- headache
- chills
- vomiting
- muscle pain
- paroxysm (cycle in 4-8 hours)
Complications of malaria
- severe anaemia (RBC destruction)
- cerebral malaria (swelling of brain, seizures, coma)
- liver failure
- shock
- pulmonary oedema
- abnormally low blood sugar
- kidney failure
- swelling and rupture of spleen
Uncomplicated malaria treatment
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Severe malaria treatment
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Diagnosis of malaria
- blood film (Giemsa stained)
- commercially available antigen detection tests (rapid but more expensive and less sensitive)
Toxoplasma gondii
Routes of infection:
- undercooked meat of animals harbouring tissue cysts
- consuming food or water contaminated with cat faeces
- contaminated environmental samples
- blood transfusion
- organ transplantation
- transplacentally from mother to foetus
Major forms of leishmaniases
- visceral leismaniasis
- cutaneous leishmaniasis
- diffuse cutaneous leishmaniasis
- mucocutaneous leishmaniasis
Visceral leishmaniasis
BLACK FEVER (Kala Azar)
- most severe form=affects internal organs
- fatal if left untreated
- characterised by irregular fever, weight loss, liver/spleen swelling and anaemia
Cutaneous leishmaniasis
- skin lesions on exposed body parts
- often self-healing
- can create serious disability and scars
- immunity to reinfection
Diffuse cutaneous leishmaniasis
- disseminated lesions
- resembles leprosy difficult to treat
- no spontaneous healing
- frequent relapses
Mucocutaneous leishmaniasis
- disfiguring
- destroys mucous membranes
Epidemiology of amoebae
- Entamoeba histolytica infects ~10% of world population
- third most common cause of death of parasitic infections (after schistosomiasis and malaria)
- common in south and central America, west and south-east Asia=rare in temperate climates
- ~90% infections are asymptomatic=remaining 10% produce spectrum of disease varying from dysentry to amoebic liver abscess
- incubation period may be as short as 7 days
- tissue invasion mostly during first 4 months of infection
Amoebae (Entamoeba histolytica) life cycle
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Organisms and associated disease of Coccidia
- Plasmodium species= malaria
- Toxoplasma= toxoplasmosis
- Cryptosporidium= diarrhoea
Malaria life cycle
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Malaria epidemiology
-in 2013, there were ~198 million cases of malaria, causing estimated 584,000 deaths, mostly among African children
Cryptosporidiosis symptoms
- diarrhoea
- fever
- nausea and vomiting
-common in HIV positive patients presenting with diarrhoea
Cryptosporidiosis diagnosis
Stool examination
Cryptosporidiosis treatment
Fluid rehydration
Ciliates infection symptoms
- asymptomatic
- immunocompromised patients may experience more severe signs and symptoms
- persistent diarrhoea
- dysentry
- abdominal pain
- weight loss
- nausea and vomiting
-if left untreated, perforation of the colon can occur
Ciliates infection diagnosis
Stool examination
Giardiasis
- commonest, globally distributedm water-borne protozoal infection
- flagellated trophozooites attach by suckers to surface of duodenal or jejunal mucosa
- ovoid cysts=able to survive standard chlorination procedures so filtration required to exclude from drinking water
Symptoms=DIARRHOEA
Leishmania parasite life cycle
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Forms of leishmania
- promastigote
- amastigote
Leishmania promastigotes
- form of Leishmania within sand fly vector
- move in direction of flagellum
- can be cultured
Leishmania amastigotes
- form of Leishmania within human or other vertebrate host’s cells (resorbed flagellum)
- no longer motile
Sand fly biology
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Distribution of Leishmaniasis
- 98 countries
- ~2 million new cases per year
- more than 350 million people at risk
- more than 20 Leishmania species
- more than 30 sandfly species
Leishmaniasis and HIV co-infections
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