TBL 12 Helminths and Protozoa Flashcards
There are 2 main types of parasites that we look at in detail.
Protozoa: Unicellular
Metazoa: Multicellular (e.g. worms)
Protozoa and metazoa are (eukaryotes/prokaryotes).
Eukaryotes - genome encased within nucleus with complex organelles in cytoplasm
Protozoa (causes/does not cause) eosinophilia (increase in non-blood tissue eosinophils), whereas metazoa (causes/does not cause) eosinophilia.
protozoa - no eosinophilia
metazoa - causes eosinophilia
_______ host is the host in which parasite undergoes sexual reproduction.
Definitive
_______ host is one which harbours the larval stages of the parasite or an asexual cycle of development
Intermediate
_______ host is one in which a parasite cannot complete its life cycle. (unsuitable)
Aberrant
________ host is a host in which the parasite is not commonly found, but still suitable for its development.
Accidental
A _______ is a living carrier which transports a pathogenic organism from an infected to a non-infected host.
vector
Compare between infection and disease.
Infection refers to the invasion and multiplication of pathogenic microorganisms within or on the body and does not necessarily mean disease.
Disease is illness characterised by specific signs and symptoms and damage to the host.
________ is the presence of microorganisms in or on the body without causing damage to the host.
Commensals
4 types of protozoa that are clinically important:
- Amoeba
- Apicomplexa
- Flagellates
- Ciliates
2 main pathogenic amoeba are:
- E. histolytica
2. Naegleria fowleri
Infective form of amoebas are _________.
infective cysts
(After ingestion of mature cysts, the encysted parasite passes through the gut and excystation takes place in the small intestine, releasing trophozoids.
Naegleria fowleri is a free-living _______ found mostly in warm water, and is a rare cause of disease primary amoebic meningo-encephalitis (PAM).
It enters through the _______ when host comes into contact with contaminated water, and proceeds to invade the ____ and cause brain damage.
amoeba
enters through the nasal cavity, invades the CNS
There are 3 main types of apicomplexans (protozoa/metazoa).
Protozoa
- Plasmodium spp
- Toxoplasma
- Cryptosporidium
Toxoplasma is a ________ protozoa that causes toxoplasmosis, and is transmitted via ________.
It is particularly serious in immunocompromised individuals, and may pose serious danger for the foetus in pregnancies due to its ability to cause ___________.
Toxoplasma
- Apicomplexan protozoa
- Transmitted through the faeces of cats
- Ability to cause trans-placental infections
Cryptosporidium is a _________ protozoa that causes _____ and is ________ (mode of transmission).
Cryptosporidium
- Apicomplexan protozoa
- Causes diarrhoea
- Water-borne (i.e. infectious oocysts are excreted by cattle, contaminating surface water.)
There are 4 species of Plasmodium which are true human parasites.
- P. ovale
- P. malariae
- P. falciparum
- P. vivax
- P. ovale
- P. malariae
Life cycle of Plasmodium in humans:
- A female infected ________ mosquito (vector) transmits Plasmodium _________ into the human host, which infects the human _______ cells.
- In the liver, the ______ mature into ________ and release ________ into RBCs.
- The merozoites undergo (asexual/sexual) reproduction to produce trophozoites.
- Trophozoites have 2 fates.
- Anopheles mosquito transmits Plasmodium sporozoites which infects human liver cells.
- In the liver, the sporozoites mature into schizonts and release merozoites into the RBCs.
- Merozoites undergo ASEXUAL reproduction to produce trophozoites.
- Trophozoites have 2 fates:
A. Mature into schizonts and produce more merozoites to infect more RBCs.
B. Develop into gametocytes
Life cycle of Plasmodium in Anopheles mosquito:
- In the ___, the male and female gametocytes fuse to form a zygote.
- ______ is formed from the development of the zygote, and it crosses the gut to reach the ________.
- _________ then get released to infect the human liver cells upon the blood meal.
- In the gut, gametocytes fuse to form a zygote.
- Oocyst is formed from the development of the zygote, and it crosses the gut into the salivary glands.
- Sporozoites get released from oocyst to infect the human liver cells during the next blood meal.
In malaria,
_______ infect human liver cells.
_______ infect human RBCs.
Sporozoites infect human liver cells.
Merozoites infect human RBCs.
In malaria,
sexual reproduction occurs in ________, whereas asexual reproduction occurs in _________.
sexual reproduction - Anopheles mosquito gut
asexual reproduction - human RBCs
What differentiates the gametocytes in P. falciparum from the other plasmodium malaria?
P. falciparum has typical crescent-shaped gametocytes (elongated); whereas others usually have round-shaped gametocytes instead.
*Multiple rings in RBCs is also characteristic of P. falciparum.
Severe malarial anaemia (SMA) may be due to the destruction of parasitized and non-parasitized RBCs.
What are some other clinical features of malaria?
Splenomegaly (destruction of RBCs), thrombocytopenia (i.e. low levels of platelets)
There are 2 main types of blood Flagellates (Protozoa/Metazoa).
Flagellates - Protozoa
Blood flagellates (i.e. infect the blood):
- Leishmaniae
- Trpanosomes
There are two Trypanosoma (________ protozoa) species.
blood flagellates protozoa
- African Trypanosoma
- American (new world) Trypanosoma species
___________ causes African sleeping sickness, which is transmitted by a ________.
African Trypanosoma; transmitted by Tsetse fly
