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Parasitology > Phylum Apicomplexa > Flashcards

Phylum Apicomplexa Flashcards

1
Q

What are the general features of protozoa?

A

Unicellular prokaryotic microorganisms
Most are motile
Contain resting stages (cysts / spores)
Asexual reproduction is usual, sexual reproduction also occurs
Can be intracellular or extracellular in blood, and organs

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2
Q

What are the general features of Phylum Apicomplexa?

A

Apical complexes within the invasive stages, use to gain access to the host
Resistant spores that can remain viable in environment for long times
Complex lifecycles that include both asexual and sexual reproduction

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3
Q

What are the features of Genus Eimeria?

A

Intracellular parasites within Digestive tract
Direct lifecycle
Merogony and gametogony occurs in the host cells, sporogony occurs in the environment
Sporulated oocysts contain 4 sporocysts each with 2 sporozoites.

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4
Q

What causes infection of the Caeca and hemorhagic faeces in chickens?

A

Poultry Emeriosis / Coccidiosis

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5
Q

What is the Emeria lifecycle?

A

Direct lifecycle
Infection of the host occurs by ingesting sporulated oocysts.

Merogony –> asexual development within the host

  • Sporozoites (within sporocysts) - banana shaped cells –> infective stage (has apical complex)
    Sporozoites develop to Trophozoites which have a nucleus.
  • Trophozoites develop to Schizonts which can move to sexual development or continue with asexual development and form into merozoites –> invade trophozoites.

Schizonts / merozoites will move into sexual reproduction within the host called Gametogony

  • Microgametocytes form into microgametes (male)
  • macrogametocytes form into macrogametes (females)

Microgametes and macrogametes undergp fecundation and form into a zygote.

The zygote forms into an unsporulated oocyst –> shed in environment.

Sporogony –> asexual development within the environment where the unsporylated oocyst forms into a sporulated oocyst containing 4 sporocysts and 2 sporozoites within each cyst.

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6
Q

What is the features of the Genus Eimeria oocysts?

A

Are essential for parasite survival in environment and host
Important for diagnosis
Oocyst wall –> most species is clear, colourless, transparent. Contains 2 layers which are very resistant in the environemnt

Unsporulated oocyst (exits from host) - are uninfective and contain one cell called sporont

Sporulated oocyst (infective stage) - Contain 4 sporocysts and 2 sporozoites in each. Infect the host

Require proper temp, humidity to develop.

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7
Q

How does the Genus Eimeria infect the host?

A

Ingestion of sporulated oocysts –> sporocysts are released within the gizzard, sporozoites are released by Bile, Trypsin and CO2

The sporozoites use the spical complex to invade the host cell (epithelial cells of SI)

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8
Q

What is the Merogoy developmental stage?

A

Asexual development:
Develops from –>

Trophozoite (invades host cells)
Immature schizont
Mature schizont –> cytoplasm divides and merozoites are formed
Merozoites –> break out of schizonts, invade other host cells. Continue asexual development

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9
Q

What is the gametogony developmental stage?

A

After so many axsexual developments, the merozoites invade other host cells and begin sexual development.

Merozoites will invade host cells, grow and form into either a Microgametocyte or Macrogametocyte. Give rise to many microgametes / macrogametes.

Undergo fecundation where they form into a zygote–> unsporulated oocyst (thin shell, one sporont).

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10
Q

What is the Sporogony developmental stage?

A

Sporozoites are formed within oocysts and they become infective
Takes place in the environment

Depends on Temperature
Humidity and Oxygen availability

Are infective in sporulated oocytes

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11
Q

Where is Eimeria tenella located?

A

Caeca - cause very bad pathology

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12
Q

Where is Eimeria necatrix located?

A

Asexual development occurs mid intestine of the host. Sexual development occurs in the caeca.

Merozoite migrate to caeca to start fevelopment –> oocyte shed in faeces

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13
Q

Where are the species of Eimeria that infect cattle located and give an example of the pathogenic speices?

A

Located in the small and large intestine

Have 13 species but the most pathogenic species in cattle is Eimeria zuernii and Eimeria bovis

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14
Q

Where are the species of Eimeria that infect sheep located and give an example of the pathogenic speices?

A

Located in the small and large intestine

Have 11 species but the most pathogenic is Eimeria ovinoidalis and Eimeria crandalis

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15
Q

Where are the species of Eimeria that infect rabbits located and give an example of the pathogenic speices?

A

Locate in the small and Large intestine except for Eimeria stiedai that is within the bile ducts.

11 species

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16
Q

What are the general features of isospora?

A

Hosts - pigs, dogs, cats, humans, etc
Contain sporulated oocysts with 2 sporocysts and 4 sporozoites

Sporozoites invade the epithelial cells of the intestine but do not form into trophozoites –> divide by endodygeny many times before forming into multinucleate schizonts

Extraintestinal stages occur in the DH (canine and feline isospora species)

Some species contain PH

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17
Q

What genus of Apicomplexa has a sporulated oocyst that has 4 sporocysts and 2 sporozoites per cyst?

A

Genus Eimeria

18
Q

Define Endodygeny

A

Formation of 2 daughter organisms within the mother cell which is used up in the process

19
Q

What are the general features of Isospora suis?

A

Host - pigs
Located inside enterocytes of the SI
Infect pigs younger than 1 month
Infected animals shed unsporulated oocysts in environment.

Sporogony occurs –> need O2, temp and humidity –> forms sporulated oocyst with 2 sporocysts and 4 sporozoites. Infection occurs via ingestion of sporulated oocysts.

Asexual: Sporozoites excyst in SI –> invade enterocytes –> divide by endodyogeny and form into type 1 meronts and merozoites which give rise to type 2 meronts and merozoites.

Sexual: Type 2 meronts and merozoites form into microgametocytes or macrogametocytes (forms microgamets / macrogametes) –> undergo fecundation and form a zygote. Zygote forms into an unsporulated oocyst which is shed in the environment with faeces.

20
Q

What is the lifecycle of Isospora within dogs and cats?

A

Located in the SI and LI

Infected host spreads unsporulated oocysts in environment –> sporogeny occurs –> Infection of DH occurs via ingestion of sporulated oocyts or ingestion of PH / IH which contain cysts in their tissues

Sporozoites excyst in the SI and invade the epithelial cells –> some will penetrate the intestinal wall and invade the mesenteric lymph node, the liver, spleen, etc where they form cysts. Intestinal sporozoites divide into endodyogeny into type 2 merozoites. Eventually form multinucleated schizonts. Sexual stages develop –> micro and macrogametes –> fecundation –> oocysts –> shed in faeces.

OR can ingest paratenic hosts –> Mice and rats can be PH or IH. Contain cysts in tissues and then once ingested, lifecycle is the same as above.

21
Q

What are the main differences between Isospora in pigs and cats and dogs?

A

Isospora suis –> does not infect intestinal wall and move into lymph node forming cysts

Isospora suis does not contain PH

dogs and cat spp –> contain PH / IH = rats and mic. Contain lymphatic and organ cysts.

22
Q

What is the difference betweeen the sporulated oocysts in Isospora and Eimeria?

A

Isospora –> contain 2 sporocysts and 4 sporozoites within the sporulated oocyst

Eimeria contains 4 sporocysts and 2 sporozoites within the sporulated oocyst.

Both contain 8 sporozoites

23
Q

What are the main features of Toxoplasma gondii?

A

Spread all over the world
Affects 1/3 of the human population - causes abortions / severe pathology in many host species (including humans)
Causes severe pathology in immunocompromised people

Toxoplasmosis is a major concern for women infected for the first time during pregnancy –> the earlier the infection (first trimester) is the more severe pathology. Infection in last trimester will not cause as much pathology, but can cause issues later in life

DH - cats in SI –> will not show any clinical signs and pathology will be milk

IH - all warmblooded animals within any nucleated mammalian or avian cell (including cats). Not all species have the same severity of infection –> humans and primates are very severe as the disease is relatively new whereas cattle and horses are resistant

24
Q

What is the lifecycle of Toxoplasma gondii?

A

DH - cat
Infected cats shed in the environment unsporulated oocysts (contains sporont). Sporogony is complete in 1-5 days. Sporulated oocysts contain 2 sporocysts with 4 sporozoites

IH - any warmblooded animal
Sporulated oocysts are ingested in food / water. Sporozoites undergo endodyogeny and produce tachyzoites which spread throughout the body.

Tachyzoites invade and multiply by endodyogeny until cells burst –> tachyzoites released and enter other cells and continue multiplication. Parasitemia during pregnancy can result in tachyzoites infecting and multiplying in placenta = abortion

After time - tachyzoites will divide slowly and form into bradyzoites –> then into cysts. Influenced by host immune system and parasite factors.

Tissue cysts are formed in CNS, muscles and organs and can persist for the life of the host. Each cyst can contain thousands of bradyzoites –> can rupture occasionally and healthy hosts will kill the bradyzoites but in immunocompromised people –> the bradyzoites can multiply and infect other organs.

In DH - cats can get infected with bradyzoites, tachyzoites and oocysts. Bradyzoites are the most common route of infection. After ingestion of the tissue cysts –> the bradyzoites are released, penetrate epithelial cells of SI, divide asexually, then sexually and form oocysts. Oocysts are released in faeces.

With asexual development in the SI of DH with the bradyzoites –> can travel into the lamina propria of the SI and form into tachyzoites –> causes severe pathology. If this occurs –> will mature to bradyzoites first before encysting.

25
Q

Define tachyzoites and bradyzoites

A

Tachyzoites –> invade any nucleated cell and divide very quickly –> spread in blood

Bradyzoites divide very slowly and eventually form into cysts.

26
Q

What are the routes of infection for Toxoplasma gondii?

A

Ingestion of Sporulated oocysts –> only route of infection for herbivores

Ingestion of tissue cysts –> one way of infectionfor omnivores and carnivores

Tachyzoites infection –> transplacental (mother to foetus)

27
Q

What are the main features of Neospora caninum?

A

Closely related to Toxoplasma gondii

DH = dogs 
IH = Cattle and Dogs
Does not infect humans 
Transmitted transplacentally (major route of infection in cattle) --> causes abortion in dairy and beef cattle.
28
Q

What is the lifecycle of Neospora caninum?

A 
DH = Canids 
IH = canids, cattle

Infectious stages include = sporozoites, tachyzoites, bradyzoites (within cysts)

DH shed unsporulated oocysts in faeces (one sporont). Undergo sporogony and form into sporulated oocysts which contain 2 sporocysts and 4 sporozoites.

IH become infected after ingestion of sporulated oocysts . Sporozoites are released from oocysts –> tachyzoites develop in various cells which divide by endodyogeny. Eventually form into bradyzoites and form tissue cysts

Tissue cysts commonly found in neuronal tissues (brain, spinal cord, etc) and muscles. Contain a thick wall and have large numbers of bradyzoites

DH become infected after ingestion of cysts from the IH. Within DH –> bradyzoites are released from tissue cysts and divide asexually then sexually into micro and macrogametes –> form into unsporulated oocysts which are released in the faeces.

29
Q

What are the main features of Sarcocystis species?

A

Produces cysts within muscles –> Economic losses because of condemnation / downgrading of meat containing sarcocysts

DH = carnivores 
IH = omnivores and herbivores - form cysts within striated muscles (rarely in CNS or other tissues)

Obligatory predator-prey lifecycle (humans apart of both)

30
Q

What is the lifecycle for the sarcocystis species?

A

Lifecycle consists of merogony in the IH, gametogony and sporogony within the DH

DH get infected by the infection of SPOROCYSTS –> not sporulated oocysts (occurs in the DH and will shed the already infective stage into environment)

Within SI sporocysts excyst and first generation schizonts generate in endothelial cells of arterioles. Second generation of schizonts develop in endothelial cells of capillaries

Merozoites released from last generation of schizonts which invade striated muscle cells and initiate sarcocyst formation. The sarcocyst eventually becomes filled with bradyzoites and are the infective stage for DH. Some sarcocysts are macroscopic or microscopic

DH become infected by ingesting muscle tissue that contains mature sarcocysts. Bradyzoites are released from cysts into the SI which develop into macro and microgametes –> form an oocyst and sporogony (formation of sporozoites) takes place in the host cells and forms into sporulated oocysts. The oocyst wall is very thin and ruptures, releasing sporocysts into the lumen which are shed into the environment

Sporocysts are not infective for the DH in the environment

31
Q

What are the general features of Cryptosporidium?

A

Primary cause of diarrhoea in both humans and animals.
Worldwide distribution
Hosts = mammals, birds, reptiles, fish
Located in the GIT
Clinical signs more severe in immunocompromised hosts

Lifecycle takes place on the tips of intestinal epithelial cells

Zoonotic

38 different species recognised

32
Q

What is the Lifecycle of Cyrptosporidium?

A

Are intracellular but extra-cytoplasmic (inside the cell but outside the cytoplasm)

Sporozoites and merozoites are bound to the epithelial cells and become enveloped by the host cell membrane

Parasite forms an attachment / feeder organelle –> from schizont

Oocysts contain 4 sporozoites –> no sporocysts. Two types –> thick shelled (80%) passed in faeces of host, thin shelled (20%) and cause autoinfection

Similar lifecycle to Eimeria
Infection of host is via ingestion of oocysts –> undergo merogony (asexual - sporozoites –> trophozoites –> type 1 meronts / merozoites –.> type 2 meronts / merozoites –> gametocytes).
Then undergo gametogony (gametocytes –> gamonts –> fecundation –> zygotes —> oocysts)
Then sporogony occurs within the host –> thick shelled (80%) shed in faeces, thin shelled (20%) causing autoinfection

33
Q

What species are within the Order Piroplasmida?

A

Babesia sp
Theileria sp

Called piroplasma due to pear shaped stages

34
Q

What are the general features of Babesia?

A

Parasites located in RBC
IH = ticks
Located in tropical / subtropical regions
Distribution is identical to where the ticks are located
Significance for human health

Stages in Vertebrate host

  • Trophozoite
  • Merozoite (pear shaped)
  • Gametocytes

Undergo merogony –> asexual multiplication via binary fission that takes place in RBC of DH.

Stages in Tick -
Gametogony –> sexual multiplication that takes place in GIT of ticks
Sporogony –> Asexual multiplication that takes place in the tissues of ticks

35
Q

What is the lifecycle of Babesia?

A 
IH = Ticks 
DH = mammals

Ticks attach to host –> use saliva to infect the host with sporozoite. (ALL STAGES of tick can transmit babesia)

Sporozoite invades RBC, divide by binary fission (merogony) and form into merozoite which breaks the RBC and invade other RBC –> some merozoites will form into gametocytes and will not develop further. Will wait until ingested by ticks.

Will remain like this until host dies or develops an immune response.

Only female ticks can become infected with gametocytes. Ingest both gametocytes and merozoites (merozoites will be digested)

Gametocytes will undergo gametogony and form into gametes, divide into zygote–> ookinet and then form into sporokinet within digestive tube cells where they divide.

Sporokinets reach the ovaries where they develop in the next generation (eggs, larvae, nymph, adults). Within the next gen, the sporokinets locate in the salivary glands where they form into sporozoites and travel through the saliva into the DH

Infection can occur in larvae, nymph or adults

36
Q

What is the development of ticks within the Babesia lifecycle?

A

Sporokinets within the female adult tick, reach and infect the tissues –> including the ovaries (transovarian transmission).

Sporokinets infect ovaries –> move into eggs –> are within the next generation, larvae –> nymph –> adults

37
Q

What Babesia species are within cattle and dogs?

A

B. bovis (in Aus - Cattle)
B. bigemina (in Aus - Cattle)
B canis vogeli ( in Aus - Dogs)
B. gibsoni (in Aus - Dogs)

38
Q

What are the differences of Babesia to Theileria?

A

Theileria reproduce in lymphocytes (mergony) and RBC
Babesia reproduce just within RBC

In ticks –> Theileria are transmitted trans-stadially and they do not have transovarian transmission

In ticks –> Babesia are transmitted via transovarian.

39
Q

What are the general features of Theileria spp.

A

Pathogenic to ruminants
Cause high economic loss and mortality in tropical and subtropical Africa.
Develop in lymphocytes and RBC
Transmitted by Ticks

40
Q

What species of Theileria are located in Aus?

A

T. orientalis

41
Q

What is the lifecycle of Theileria?

A

Development in Mammalian host:
Ticks inject host with saliva containing sporozoites.
Sporozoites enter the mononuclear leukocytes (lymphocytes), T cells, B cells, monocytes and macrophages.
Sporozoites feed on the cell cytoplasm and grow –> develop into schizont / meront –> they stimuate the division of the infected cells and schizonts also divide and infect the daughter cells.

Soon the infected lymphocytes will outnumber the healthy lymphocytes.

Merozoites will be produced inside schizonts. Merozoites are released when the lymphocytes degenerate where they actively penetrate the RBC

Within the RBC –> the parasites exist as slender comma-shaped forms or spherical / ovid forms

Development in the Tick:
Larvae and nymphs (not adults) ingest Theileria infected RBC when feeding

After tick molts sporokinetes will penetrate the cells of the salivary glands, multiply and form sporozoites.

Nymph and adult ticks will inject the sporozoites into the host with saliva.
Have Transstadial transmission - vector remains in tick from one lifestage to the next.

DH will become infected with the ticks that inject sporozoites with saliva

Parasitology (20 decks)

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