Parasitology Flashcards
What is the definition of a parasite?
β A parasite is an organism that lives on or in a host organism and gets food from or at expense of the host
What are the three classes of parasite that can cause disease in humans?
β Protozoa
β Helminths
β Ectoparasites
What are protozoa?
β single celled, microscopic organisms that can be free-living of parasitic in nature
How can intestinal protozoa be transmitted?
β fecal-oral route
How can blood or tissue protozoa be transmitted?
β Arthropod vector
How are protozoa classified?
β The mode of movement
What are the 4 types of protozoa?
β Amoeba
β Flagellates
β Ciliates
β Sporozoa
What is an example of an amoeba?
β Entamoeba
What are two examples of a flagellate?
β Giardia
β Leishmania
What is an example of a ciliate?
β balantidium
What is a sporozoa and give an example?
β Organisms whose adult stage is not motile
β plasmodium and cryptosporidium
What does entamoeba histolytica cause?
β amoebic dysentery which presents with loss of epithelium
What does giardia lamblia cause?
β Diarrhoea
β Epithelial damage and blunting of microvilli
What does trichomonas vaginalis cause?
β Vaginal discharge
How is toxoplasma gondii transmitted?
β through cat feces
What can cryptosporidium cause?
β Epidemic diarrhoea
What type of infection is cryptosporidium and who does it affect?
β Opportunistic infection that arises in immunosuppressed people
What type of an infection is leishmania?
β Protozoal
What does leishmania cause?
β severe systemic illness and cutaneous disease
What disease does trypanosoma cruzi cause and where is it endemic to?
β Chagas disease
β South America
What disease does trypanosoma brucei cause?
β African sleeping sickness
What are helminths?
β Large multicellular organisms (worms) generally visible to the naked eye in their adult stages
What are the three main groups of helminths that are human parasites?
β Nematodes (roundworms)
β Trematodes (flukes)
β Cestodes (tapeworms)
What are 4 examples of soil transmitted helminths?
β Ascaris lumbricoides
β Trichuris trichuria
β hookworm
β enterobius vermicularis
What are the two important types of nematodes?
β Soil transmitted helminths
β Filarial parasites
What are 4 examples of filarial parasites (helminths)?
β Wuchereria bancrofti
β Loa loa
β Onchocerca volvulus
βDracunculus medinesis
What does Wuchereria bancrofti cause?
β Elephantiasis
What are two other important helminths other than the filarial parasites and soil transmitted helminths?
β Toxocara canis/cati
β trichinella spiralis
Give 4 examples of medically important trematodes?
β Schistosoma mansoni/haematobium/japonicum
β Clornochis sinensis
β Fasciola hepatica
β Paragonimus
What does paragonimus cause?
β TB like illness
What does clornochis sinensis cause?
β Cholangiocarcinoma
Give 3 examples of medically important cestodes?
β Taenia saginata
β Taenia solium
β Echinococcus granulosus
What can taenia solium cause?
β cysts in the brain
What can echinococcus granulosus cause?
β hydatid disease
What are ectoparasites?
β Blood sucking arthropods such as ticks,fleas, lice and mites that attach or burrow into the skin and remain there for relatively long periods of time (weeks to months)
What are 2 examples of mites?
β Scabies
β Trombiculid
What are two types of ticks?
β hard
β soft
What are three types of lice?
β Pediculus humanus capitis
β Pediculus humanus humanus
β Pthirus pubis
What are the two types of parasitic host?
β Intermediate
β Definitive
What is an intermediate host?
β a host in which larvae or asexual stages develop
What is a definitive host?
β a host in which the adult or sexual stage occurs
What are the two types of parasitic vectors?
β Mechanical
β Biological
What is a mechanical vector?
β When there is no development of the parasite in the vector
What is a biological vector?
β When some stages of the life cycle of the parasite occur in the vector
Describe the life cycle of schistosomiasis?
β you walk in water contaminated by human feces
β the eggs develop into miracidia which infect the intermediate hosts which are snails
β the snail becomes an amplifier and there is asexual reproduction in the cell called cercariae
β the cercariae infect the humans
β they develop into adults in the host
β the adults undergo sexual reproduction and the female releases eggs
Where are most parasitic infections from?
β Animals
What is DALY?
β Disease adjusted life years
Why is DALY a unit of measurement?
β Many infections are not fatal but they cause chronic illness
β DALY measures the amount of disability years
How can feco-oral route using parasites be eradicated without medication?
β Household sanitation
β Access to clean water
β personal hygiene behaviors
How can food route using parasites be eradicated without medication?
β Animal husbandry
β Surveillance
β Government control and regulation
Describe how Chagas disease occurs?
β Reduviidae bugs feed on the human and defecate
β when the bite is scratches you can scratch the feces into your skin
β the parasite enters and multiplies in nerve or muscle cells
β the cells rupture releasing thousands of trypomastigotes that can be taken up by the bug again
Where is Chagas disease endemic to?
β latin and south america
What is parasite is Chagas disease caused by?
β Trypanosoma Cruzi
What are the three phases of Chagas disease?
β Acute
β Chronic βindeterminateβ
β Chronic βdeterminateβ
What are the three characteristics of the acute phase of Chagas disease?
β incubation 1-2 weeks after bite
β upto months after transfusion
β trypanosoma in blood
What are the 5 characteristics of the chronic βindeterminateβ phase of Chagas disease?
β Lifelong infection β generally trypanosomes detectable but often positive for parasite DNA β seropositive β 60-70% of infected β normal ECG and X-rays
What are the 3 characteristics of the βdeterminateβ chronic phase of Chagas disease?
β seropositive
β 30-40% infected
β 10-30 years after infection
What % of people develop chronic Chagas after the acute disease?
β 5-10%
What are the symptoms of acute Chagas disease?
β Local swelling (romana) β nodule or chagoma β fever β anorexia β lymphadenopathy
When do the symptoms of acute Chagas disease occur within and how long do they last?
β 3 weeks
β symptoms last 8-10 weeks
What are the rare complications of acute Chagas disease?
β Hepatosplenomegaly
β Acute myocarditis
β Meningoencephalitis
β Fatality <5% of symptomatic
What are the cardiac effects of chronic Chagas disease?
β There is damage to the conduction system of the heart
β this causes arrhythmia
β damage to the heart muscle wall causing cardiomyopathy
β apical aneurysms can occur
βsudden death due to arrhythmia is common
What % of people with chronic Chagas disease are affected with digestive issues?
β 10-15%
What digestive organs are most affected in chronic Chagas?
β Esophagus
β rectum
β sigmoid colon
What are the complications of a megacolon during Chagas disease?
β Fecaloma β Obstruction β Sigmoid volvulus β Ulceration β perforation
What is the presentation of a megacolon?
β constipation
Describe the progression from acute Chagas to chronic?
β Acute illness occurs that is not symptomatic
β Parasites appear in the blood
β the immune response starts to control the parasite numbers and you go into the indeterminate phase
β after many years there is development of chronic Chagas disease
What is tissue damage in acute Chagas caused by?
β Tissue damage caused by the inflammatory response to parasite in nests of amastigotes in cardiac, skeletal and smooth muscle
How does parasite killing occur in acute Chagas?
β Parasite killing by antibodies
β activated innate immune response
β Th1 inflammatory cytokines
What is the immune response to Chagas in the indeterminate phase characterised by?
β IL-10 and IL-7
What is the type of immune response to Chagas in the chronic phase?
β Chronic inflammatory response to persistent parasites in muscle and nerve cells
