W21 Protozoan microorganisms

Question 1

What is a parasite?

Answer 1

Parasite - living eukaryote organism, which takes its nourishment and other needs from a host. Depends on the host for nutrition.
e.g. protozoa/helminth/ectoparasites

Question 2

What are Endoparasites?

Answer 2

• Inside of the host’s body - Permanently
• Some anaerobes, some aerobes
  -Protozoa and helminths

Question 3

What are Ectoparasites?

Answer 3

• ON the outer surface of the host’s body – temporary or permanent
• Aerobes
• Some ectoparasites serve as vectors of pathogens
  -ticks, fleas, lice, and mites

Question 4

Endoparasites:
What are protozoa?

Answer 4

• Monocellular
• Pluricellular, Parasitic worms (usually visible)
• Mostly asexual reproduction (most by binary fission), and sexual reproduction
• Some are non-motile, those motile use either flagella or cilia

Question 5

Endoparasites:
What are Helminths:

Answer 5

• Pluricellular, Parasitic worms (usually visible)
• Sexual reproduction
• Move through muscular contractions

Question 6

What are some characteristics of protozoa?

Answer 6

• Ranging in size - 2-100 μM
• Require high moisture environments
• Diverse oxygen requirements
• All protozoa are chemoheterotrophs
  -preformed organic substances
  -Similar requirements of the mammalian cells
• Establish parasitic relationships with many hosts

Question 7

What are the 2 morphological forms/stages of of some protozoa? (for info)

Answer 7

1. Trophozoite
   * Motile, vegetative (active) form
   * Actively feed and multiply
   * Pathogenic form
2. Cyst
   * External, non-parasitic form
   * Possess a protective membrane or thickened wall
   (survival outside the host)
   * Means of transfer between hosts

Question 8

How are intestinal protozoa transmitted? (4)

Answer 8

Through the fecal-oral route
Such as by:
* Contaminated food
* Contaminated water
* Domestic pets
* Sewage/waste water
e.g. Inadequate sanitation and poor hygiene practices

Question 9

What are the Medically relevant protozoa? (4)
– motility classification

Answer 9

• Many protozoan infections can be inapparent/mild in normal individuals, yet life-threatening in immunosuppressed patients (e.g. AIDS).
• Many move to various sites within the body
• Classified by their motile form
• Amoebae - amoeboid movement (temporary extensions of the plasma membrane)
• Flagellates - use flagella
• Ciliates - use cilia
• Sporozoa - Non motile, spore-producing protozoa

Question 10

What are amebae?

Answer 10

• Move by extending pseudopods (Arm-like projection of the cell membrane)
• Engulf food with pseudopods and phagocytize
  -Entamoeba histolytica - feeds on red blood cells

Question 11

What are flagellates?
What do they include? (2) (different types)

Answer 11

• Possess one or more flagella for locomotion and sensation
• Intestinal and genito-urinary flagellates (e.g. Giardia and Trichomonas)
• Blood and tissue flagellates (Trypanosoma and Leishmania)

Question 12

Transmission of blood borne protozoa- Leishmania

Answer 12

• In humans, Leishmania spp. parasitise in mononuclear phagocytic cells (macrophages, monocytes)
• Leishmania protozoa are usually spread through the bite of infected sand flies

Question 13

What are the types of Leishmaniasis?

Answer 13

Leishmaniasis produces a spectrum of diseases
1. Cutaneous leishmaniasis - affects the skin (skin ulcers)
2. Mucosal leishmaniasis - affects the mucous membranes of the nose and mouth, causing sores and destroying tissues
3. Visceral leishmaniasis - affects the internal organs,particularly the bone marrow, lymph nodes, liver, and spleen

Question 14

What is Trichomoniasis? (for info)
What are some examples of STI’s?

Answer 14

• Lower genital tract infections
• Caused by infection of Trichomonas vaginalis
• Common sexually transmitted disease (STD)

Other STDs examples:
- Chlamydia, Gonorrhoea (bacteria)
- Genital herpes, AIDS (viruses, i.e. HSV and HIV)
* Various human papilloma virus infections

Question 15

What are Cilliates?

Answer 15

• Complex protozoa that move by cilia (hair-like organelles) distributed in rows or patches
• Only known human pathogen is Balantidium coli – causing in severe intestinal infection – dysentery in some cases
• Unusually, they have two different types of nuclei
   Transmitted through infected pigs
   Also oral-fecal transmission

Question 16

What are sporozoa?

Answer 16

• Do not have any locomotory extensions
• Complex life cycles
   Alternating sexual and asexual reproduction, also involving spores
   Usually, they have more than one host (definitive and intermediate hosts)
• Intracellular parasites
   Cryptosporidium - diarrheal disease cryptosporidiosis
   Cyclospora - intestinal illness
   Toxoplasma – usually mild flu-like illnesses (humans are the intermediate host, cats
  are the definitive hosts). In pregnancy, Toxoplasmosis can cause miscarriages.
   Plasmodium species - Malaria

Question 17

What are plasmodium?
How are they transmitted? (3)

Answer 17

• Agent responsible for malaria – the major and most deadly protozoa-causing
  disease
• Obligate intracellular parasite – sporozoan
• 4 species responsible – P. malariae, P. vivax, P. falciparum and P. ovale
• P. falciparum causes the most severe disease and is the most common

Transmission
* Spread to humans by the bite of female mosquitoes of the genus Anopheles
* Blood transfusions
* Mother to fetus

Question 18

What is malaria?

Answer 18

• Around 250 million new cases and
  1 – 2.5 million deaths each year
• Endemic (disease constantly present at
  a constant level) in tropics – subtropic
  countries with a temperate climate
• Serious complications may occur
   cerebral malaria
   severe anaemia
• Acute febrile illness
   Symptoms after 10-14 days from mosquito’s bite

Question 19

How is malaria controlled?

Answer 19

• One vaccine (RTS,S) available showing modest efficacy, preventing about 30% of severe malaria cases
• Drugs to prevent malaria (prophylaxis, reducing the risk of malaria of 90%) before travel into an endemic area until 4 weeks after leaving the area
   Atovaquone plus proguanil – started 1-2 days before the travel
   Doxycycline (Vibramycin-D) – started 1-2 days before the travel
   Mefloquine (Lariam) – started 2-3 week before the travel
   Chloroquine and proguanil – started 1 week before the travel
• Personal protection against bites (Insect repellents, covering clothes, nets)
   50% Diethyltoluamide (DEET),
• Environmental mosquito control (destruction of larvae by environmental management)Control of malaria

Question 20

Antiprotozoal drugs

Answer 20

• Protozoal diseases are no longer confined to specific
  geographic locales
• Unicellular eukaryotes, less easily treated than bacterial infections
• The mechanism of drug action for most antiprotozoan drugs is not completely elucidated
• Many of the antiprotozoal drugs cause serious toxic effects in the host (e.g. Mefloquine)
• Most antiprotozoal agents have not proven to be safe for pregnant patients.

Question 21

What are some principles of microorganisms identification
(methods)

Answer 21

1. Microscopic examination to identify the morphology of microbes in specimens,
2. Study of the growth and biochemical characteristics of isolated microorganisms (pure cultures for bacteria and fungal cells, virus cultivation, specific biochemical tests based on the properties of the microbe)
3. Immunologic tests that detect antibodies or microbial antigens/proteins (e.g. ELISA
   tests, Later Flow Tests)
    To detect the presence of a microbial protein/antigen in a sample using antibodies directed against the protein (highly specific) linked to enzymes, or vice versa
4. Molecular methods (detecting the specific genome of a certain microorganism)
    Polymerase Chain Reaction (PCR) based techniques allow amplification of a known gene of interest (based on unique sequence of nucleotide)
    nucleic acid sequencing