TEST 2 Intro to Parasitology Flashcards
Define Endoparasites
classified into intestinal, atrial or they may inhabit body tissues causing serious health problems.
Define Ectoparasites
Arthropods that either cause diseases, or act as vectors transmitting other parasites.
Define Definitive host (DH)
Harbours the adult or sexually mature stages of the parasite (or in whom sexual reproduction occurs).
Define Intermediate Host (IH)
harbours larval or sexually immature stages of the parasite (or in whom asexual reproduction occurs)
Define Reservoir host (RH)
Harbours the same species and same stages of the parasite as man. It maintains the life cycle of the parasite in nature and is therefore, a reservoir source of infection for man.
Define Paratenic or Transport Host
Whom the parasite does not undergo any development but remains alive and infective to another host. Paratenic hosts bridge gap between the intermediate and definitive hosts.
Define Vector
an arthropod that transmits parasites from one host to another, e.g. female sand fly transmits Leishmania parasites.
Define peroral
Transmission by food or water contamination (e.g., roundworm, amoebae)
Define Percutaneous
Skin Penetration
Define Transmissive
Transmission by Insect vectors
Define Transplacental
From Pregnant woman to fetus
Define Sexual intercourse
Sexual transmitted
Define airborn
Inhalation of contaminated dust or air ( pinworm)
Define Helminthic parasites
- Multicellular organisms
- Parasitic worms such as flukes, tapeworms, and roundworms.
- Trematodes (flat worms)
- Cestodes (segmented ribbon worms)
- Cylindrical worms (Nematodes)
Define Protozoan parasites (unicellular organisms).
- Flagellates, amebas, ciliates, and sporozoa.
What is the severe form of scabies?
Scabies Crustosa, aka Norwegian Scabies
Define Monoxenous
direct - Having only one host in the life-cycle
Define Heteroxenous
indirect - Parasites that have more than one host in their life cycles.
How are parasites diagnosed?
- Imaging and Endoscopy, Clinical picture and geographic location.
- Direct microscopy of specimens (stool, urine, blood, CSF, and tissue).
- Antigen /Antibody detection assays
Leishmaniasis basics
- Protozoan
- Spread by Sand flies (Phlebotomus)
- Two forms
- Cutaneous leishmaniasis
- Visceral leishmaniasis
- Exist in two vital stages:
- promastigote: has flagella
- Infective stage.
- amastigote: no flagella
- promastigote: has flagella
Clinical Symptoms of Cutaneous leishmaniasis
- Low RBC count
- Skin sores within weeks or months of bite.
- Red papule (1st symptom) appears within 2 weeks-2 months of bite.
- Untreated may develop into the mucocutaneous form in up to 80% of cases.
- Spread to the nasal and oral mucosa may become apparent concomitant with the primary lesion or years after it has healed.
Clinical Symptoms of Visceral leishmaniasis
- Incubation period: Several weeks to a year
- Can be rapidly fatal, slow and debilitating or asymptomatic.
- Aka, Kala-azar (“black fever” in Hindi), dumdum fever.
- Caused by
- L. donovani
- L. infantum
Diagnosis of Leishmaniasis:
- Detection of either the amastigotes in clinical specimens or promastigotes in culture.
- VL:
- Splenic puncture
- Lymph node aspirates
- Liver biopsy
- sternal aspirates
- Iliac crest bone marrow
- Detection of leishmanial DNA or RNA
Define Trypanosomiasis:
Diseases in vertebrates caused by parasitic protozoan trypanosomes of the genus Trypanosoma.
Common name of American trypanosomiasis?
Chagas disease
What is the causative organism of Chagas disease
Trypanosoma cruzi
Chagas Disease transmission
- Bite from infected triatomine bug (“Kissing bug”)
-
Blood transfusions and organ transplants
- Second most common mechanism of transmission.
-
Transmission through birth
- Less frequent.
Clinical symptoms of Chagas?
- Romana’s Sign: Unilateral swelling of the eyelids.
-
Acute stage: local skin nodule “chagoma”
- Usually asymptomatic
-
Indeterminate Stage:
- 8-10 weeks no symptoms.
-
Chronic Stage:
- Dementia, Cardiomyopathy, altered heart rate or rhythm, sometimes dilation of the digestive tract, weight loss.
Diagnosis of Chagas
- “Buffy coat” after centrifugation of heparinized blood.
- T. rangeli looks very similar to T. cruzi in smears.
- “Xeno-diagnosis” allowing uninfected, lab-bred kissing bugs to feed on patient and later examining the contents of the bug for the parasite.
- Serologic Tests:
- indirect hemagglutination or immunofluorescence
- ELISA test
Treatment of Chagas
- No effective treatment
- Benznidazole and Nifurtinox: current drugs of choice to kill extracellular parasites.
- Hospital may be needed to treat symptoms
Prevention of Chagas
- Avoid sleeping in poorly constructed thatch, mud housing
- Use insecticides
- Be aware of the risk of contracting Chagas disease through blood transfusion.
What is the common name of Schistosomiasis?
Bilharzia
What are the three causative species of Schistosomiasis?
S. mansoni, S. haematobium, and S. japonicum
Pathology of Schistosomiasis?
- Migration phase (from penetration to egg production)
- Toxic reactions and pulmonary congestion; fever.
- Lasts 4-10 weeks
- Move from lungs to final tissue.
- Acute Phase (begins at egg production)
- 2 months - several years.
- Chronic Phase:
- Chronic bloody diarrhea, with mild abdominal pain and lethargy.
- Hepatomegaly
- Granuloma forms around eggs that become trapped in the walls of the intestine and urinary bladder.
Treatment of Schistosomiasis?
- No reliable prophylactic regimen is available, other than the observance of proper sanitation.
- Avoidance of cercariae-infested waters, and prevention of water contamination by human excreta.
