Para Flashcards
What is a parasite?
→parasite is an organism that lives on or in a host organism and gets its food from or at the expense of its host
What are the three main classes of parasite?
→Protozoa
→Helminths
→Ectoparasites
What are protozoa?
→microscopic, single-celled organisms that can be free- living
How are protozoa living in the intestine transmitted?
→ can be transmitted by the faecal-oral route
How are protozoa living in blood transmitted?
→transmitted by an arthropod vector
How are protozoa classified?
→by mode of movement
What are 4 types of protozoa?
→Amoeba, e.g. Entamoeba
→Flagellates, e.g. Giardia, Leishmania
→Ciliates e.g. Balantidium
→Sporozoa – organisms whose adult stage is not motile
e.g. Plasmodium, Cryptosporidium
Name some medically important protozoa infections
→Entamoeba histolytica- amoebic dysentery- forms ulcers in the large intestines
→Trichomonas vaginalis- STD
→Malaria (Plasmodium spp.)
What are helminths?
→large, multicellular organisms (worms)
→visible to the naked eye in their adult stages
When can helminths not multiply?
→adult form
What are the three groups of helminths?
→Nematodes (roundworms)
→Trematodes (flukes)
→Cestodes (tapeworms)
What are the three types of medically important nematodes?
→Soil-transmitted helminths
→Filarial parasites
→Others
Give an example of soil transmitted nematode
→Hookworm spp.- small intestines
What is the difference between Taenia saginata and Taenia solium?
→Taenia solium is shorter than saginata
Where can Taenia solium larvae migrate to?
→brain
What are ectoparasites?
→Blood-sucking arthropods such as ticks, fleas, lice, and mites
How long do ectoparasites remain in the skin?
→weeks to months
What are the 4 types of ectoparasites?
→mites
→ticks
→lice
→flies
What are the 2 types of hosts of parasites?
→Intermediate – host in which larval or asexual stages develop eg shictoma uses snail
Definitive – host in which adult or sexual stage occurs
What are the types of vectors?
→Mechanical when no development of parasite in vector
→Biological when some stages of life cycle occur
What is a primary determinant of distributions of parasite infections in the humans?
→Relative wealth
What are other determinants of parasite infections?
→Government resources and level of human development/per capita income
→Education
→Country-level and regional control programmes
→Availability of cheap and efficacious treatments
→Construction and building regulations (eg Chagas)
→Urban vs. rural residence
→Environmental sanitation
Describe the life cycle of Trypansoma cruzi(Chagas)
→triatomine bug takes a blood meal
→metacyle trypomastigotes penetrate various cells at bite wound
→amastigotes multiply by binary fission
→intracellular amastigotes transform into trypomastigotes
→they burst out of cells and enter blood stream
→epimastigotes in midgut multiply
Where is Chagas endemic to?
→South America
What are the phases of disease?
→acute
→intermediate chronic
→determinate chronic
Describe the acute phase of Chagas disease
→Incubation 1-2 wks after bite
→Up to months after transfusion
→Trypanosomes in blood
Describe the intermediate phase of Chagas
→Lifelong infection
→trypanosomes not detectable but often positive for parasite DNA
→Seropositive
→60-70%
→Normal ECG and X rays
Describe the determinate phase of chronic disease
→Seropositive
Describe the symptoms of acute Chagas
→Local swelling (Romaña)
→Nodule or chagoma
→Fever
→Anorexia
→Lymphadenopathy
How long do symptoms last in Chagas?
→8-10 wks
What are rare effects of Chagas?
→Hepatopsplenomegaly
→Acute myocarditis
→Meningoencephalitis
→fatal
What is Chagas effect on the heart?
→damage to Purkinje fibres
→thin heart muscles
→aneurysms of the muscle
What parts of the digestive tract does chronic commonly Chagas affect?
→Esophagus,
→rectum,
→sigmoid
→colon
What is the main presentation for chronic Chagas affect on the colon?
→megacolon
→constipation
What are the complications of a megacolon?
→Faecaloma
→Obstruction
→Sigmoid volvulus
→Ulceration
→Perforation
Describe acute immune response to Chagas pathogenesis
→Tissue damage caused by inflammatory response
→Parasite killing by antibodies
→Th1 pro- inflammatory cytokines
Describe immediate immune response to Chagas pathogenesis
→characterized by IL-10 and IL-17
Describe chronic immune response to Chagas pathogenesis
→Predominance of Th1 cytokines and CD8+ T cells
→Autoimmune mechanisms
What is the difference between Old World and New World cutaneous leishmaniasis?
→Old World- Mediterranean/Middle East
→New world- Central and South America
Describe the life cycle of leismaniasis
→sandfly bites skin
→promastigote engulfed by histocyte
→binary fission
→amastigotes in histocytes infect other cells
→amastigotes released and taken up by sandfly
What is the vector of leismaniasis?
→sandfly
→feed on chicken
What are the clinical features of cutaneous leishmaniasis?
→purple colouring
→plaques
→ulcer
What can happen in the most serious cases of leishmaniasis?
→uncontrolled proliferation of parasites on skin
Describe chronic leishmaniasis pathogenesis
→Mucocutaneous disease associated with strong but inadequate inflammatory response to parasites that have metastasized to mucosa
→Diffuse cutaneous leishmaniasis associated with uncontrolled parasite replication.
→Recividans – recurrence of lesions at old ulcer site
→alteration in immune reponse
Describe latent leishmaniasis pathogenesis
→characterized by balance of Th1 and anti-inflammatory responses
→use of steroids
Describe acute leishmaniasis pathogenesis
→Parasite killing by Th1 pro-inflammatory responses
→Tissue damage caused by inflammatory response
