Biological Sciences 318 - Parasitology Lab

Apicomplexa

Apicomplexa

Kingdom II Euprotista

Phylum Apicomplexa

Classes (& Genus): Gregarina (Monocystis), Coccidia (Eimeria, Sarcocystis, Toxoplasma, Haemogregarina), Haemosporidia (Plasmodium, Haemoproteus), Piroplasmea, Perkinsea

Protozoa

Apicomplexa Sarcomastigophora Ciliophora

Gregarina Coccidia Haemosporidia

Apical complex:

Polar rings (one or more) ConoidRhoptries (cell penetration and nutrient transport)Micronemes (attachment of parasite to host cell) Subpellicular microtubulesDense granules (containing proteins; released after invasion to function in calcium binding and formation of cysts)

• Diverse group• All are Parasitic - endoparasitic • Most have complex life cycles• Many have a spore stage• Exquisitely evolved interaction with their host• Associations range from avirulent to virulent pathogens• No obvious external organelles involved in locomotion • No cilia or flagella, except for gametes• Feeding: Osmotrophy, Phagotrophy (Micropore/Cytostome)• Asexual (Schizogony or Endopolyogeny) and sexual reproduction (Syngamy, Conjugation).• Include parasites with huge impact on human and animal health.

Apicomplexa

Life cycles: Asexual (Schizogony or Endopolyogeny) and sexual (Syngamy) development

Apicomplexa

4 general componentsSporogony: the product of a large number of sporozoites Merogony: production of merozoites Gamogony: formation of gametesSyngamy: fertilization of gametes to produce a zygote

The sporont, meront, and gamont multiply asexually by schizogony [Schizogony: multiple nuclear divisions and then plasmotomy]

• some elements of AC converted into holdfast organelles (attachment to host cell)

• Hosts: invertebrates primarily annelids (earthworm) and arthropods

• no schizogonic phase (trophozoite instead merogony)

• sporozoites form trophozoites in sperm mother cell of earthworm

Class Gregarina: Genus Monocystis

Life cycle: direct

Slide

1.Troph attached to cell

2.Syzygy (2 Trophs associate in cyst)

3.Gamogony

4.Syngamy

5.Sporogony

6.Gametocyst with Oocysts each with 8 Sporozoites

• Eimeria spp.• Intestinal coccidiosis • great economic importance in domestic animals• Every species of mammal has 2 to a dozen species of

Coccidia!

• Host: intracellular parasites (principally vertebrates)

• Life cycle: complex; include 3 sequential stages endogenous merogony, gamogony followed by sporogony (exogenous)

• Transmission: Ingestion of resistant Oocyst

• Pathology: Diarrhea (watery, bloody), sloughing of epithelium, cell death

Class CoccidiaIntestinal Coccidia

Eimeria, Isospora, Cyclospora, Cryptosporidium

Class CoccidiaIntestinal Coccidia

Eimeria, Isospora, Cyclospora, Cryptosporidium

Order Eimeriidae• Homoxenous (direct life cycle) • Merogony, gamogony and the formation of oocysts occurs within the same host. • Oocysts leave the host via the feces, and are unsporulated (undeveloped, non-infective). Exogenous Sporogony Sporulated oocysts of Eimeria contain 4 sporocysts, each with 2 sporozoites.

Eimeria stiedae is a parasite of rabbits development in the bile ducts of liverTransmission: ingestion of oocysts.Sporozoites break out, travel to bile ductPenetrate epithelial cells. Undergo schizogony forming a schizontSchizont produces merozoitesSome merozoites undergo gamogonySyngamyOocyst

Class CoccidiaIntestinal Coccidia

Eimeria, Isospora, Cyclospora, Cryptosporidium

Order EimeriidaeSlide: Liver tissue section infected with Eimeria stiedae. Trophozoites are round inclusions in the biliary epithelium. Macrogametocytes are large oval bodies with peripheral red-staining granules.Microgametocytes are few in number and more diffusely stained than macrogametocytes. Schizonts (contain 6-20 banana-shaped merozoites).

Class CoccidiaExtraintestinal Coccidia (tissue Coccidia)

Toxoplasma, Sarcocystis, Neospora

• Large group of organisms important to humans and animals• Isosporoid oocyst: 2 Sporocyst with each 4 Sporozoites

Two host life cycles obligate for Sarcocystis facultative for ToxoplasmaDefinitive Host (carnivore or omnivore)• adult forms• sexual reproduction• usually in intestinal tract

Intermediate Host (herbivore)• immature forms• asexual reproduction• usually extra intestinal (blood vessels, liver, muscle, brain)

• Sarcocystis spp.• Sarcocystosis

• Hosts Definitive: canids (intestinal tissue) Intermediate: domestic ox, sheep, ducks (somatic muscle) • Transmission Definitive: prey-predator (ingestion of flesh) Intermediate: Ingestion of Oocyst (intermediate host)

• Two host indirect life cycle • Pathology Definitive: not very pathogenic Intermediate: brain, muscle, and kidney tissues may be damaged by infection. Clinical signs: loss of appetite, fever, weight loss, anemia, and death in severe in infections.

Slide

Class CoccidiaExtraintestinal Coccidia (tissue Coccidia)

Toxoplasma, Sarcocystis, Neospora

• Toxoplasma gondii• Toxoplasmosis

• Hosts (low host specificity) Definitive: Felines (intestinal tissue) Intermediate: almost any mammal, bird (most nucleated cell types) • Transmission Definitive: prey-predator (ingestion of flesh) Intermediate: Ingestion of oocyst (cat feces) Ingestion of bradyzoites (raw meat) Congenital

• Two host indirect life cycle; intermediate host not mandatory! • Pathology In most humans infected with Toxoplasma, the disease is asymptomatic.  However, under some conditions, toxoplasmosis can cause serious pathology, including hepatitis, pneumonia, blindness, and severe neurological disorders. immuno-compromised individuals (AIDS) 

Class CoccidiaExtraintestinal Coccidia (tissue Coccidia)

Toxoplasma, Sarcocystis, Neospora

• Two host indirect life cycle; intermediate host not mandatory!

Extraintestinal phase (intermediate host)

Intestinal phase (definitive host)

Class CoccidiaExtraintestinal Coccidia (tissue Coccidia)

Toxoplasma, Sarcocystis, Neospora

Intestinal coccidia:

Eimeria, Isospora, Cryptosporidium

Genetically programmed number of asexual cycles- sexual reproduction-oocysts- exit with feces

Extra Intestinal coccidia:

Toxoplasma, Sarcocystis

Genetically programmed number of asexual cycles- sexual reproduction-oocysts- exit with feces some stages enter muscle or other tissues- transmitted via predation

• This group includes the most pathogenic parasites of man.

• Cosmopolitan disease in tropical and sub tropical regions of the world

• Most important vector-borne disease

• Romans called it “mala aria”- disease emanating from the swamps

• The causal agent only identified in 1897

•40% of the world population is at risk for contracting malaria.

•It occurs in over 90 countries.

•500 million new cases and 2-3 million deaths annually.

•Problems with vector resistance to insecticides, Plasmodium resistance to drugs, no vaccine have made malaria an excellent example of a re-emerging infectious disease.

Class HeamosporidiaGenus Plasmodium

Human malaria parasites belong to one of four species

Plasmodium vivax benign tertian malaria, vivax malaria

Plasmodium falciparum malignant tertian malaria, falciparum malaria

Plasmodium ovale tertian malaria, ovale malaria

Plasmodium malariae quartan malaria, malariae malaria

• Cosmopolitan disease in tropical and sub tropical regions of the world• It occurs in over 90 countries.• 500 million new cases and 2-3 million deaths annually.• Most deaths occur among young children in tropical Africa who are infected with P. falciparum..

Class HeamosporidiaGenus Plasmodium

Two host indirect life cycle (Vector required for completion)

Definitive Host: Mosquito; sexual cycle; Maturation of gametes, fertilization, Sporogony

Intermediate Host: Human; asexual cycle; Merogony, Gamogony

3 Cycles: Sporogonic cycle, Exo-erythrocytic cycle (liver cells), Erythrocytic cycle (RBC)

Class HeamosporidiaGenus Plasmodium

Life cycle

• Symptoms of malaria include fever and flu-like illness, including shaking chills, headache, muscle aches, and tiredness. Nausea, vomiting, and diarrhea may also occur.

• Malaria may cause anemia and jaundice (yellow coloring of the skin and eyes) because of the loss of red blood cells. Infection with one type of malaria, P. falciparum, if not promptly treated, may cause kidney failure, seizures, mental confusion, coma, and death.

• For most people, symptoms begin 10 days to 4 weeks after infection, although a person may feel ill as early as 8 days or up to 1 year later.

• Two kinds of malaria, P. vivax and P. ovale, can create problems later: some parasites can rest in the liver for several months to 40 years after a person is bitten by an infected mosquito, and can cause disease.

Class HeamosporidiaGenus Plasmodium

Malaria

Slide: Blood smear of Plasmodium vivax: Plasmodium vivax can be recognized by its variable ring stage. Schizonts contain about 16 merozoites and the infected cell is enlarged and contains Schuffner’s dots. The disease caused by this Plasmodium is mild and known as benign tertian malaria (fever paroxysms typically every 48 hours)

Class HeamosporidiaGenus Plasmodium

Schizont with Schuffer’s dots

Schizont

Ring stage

Slide: Blood smear of Plasmodium falciparum: has a very neat ring stage trophozoite. Multiply infected cells are common. Schizonts are rare in the peripheral blood. Gametocytes are crescent shaped. The disease caused by this organism is severe and known as malignant tertian malaria (fever paroxysms every 48 hours). It is this species that kills the vast majority of humans that die of malaria.

Class HeamosporidiaGenus Plasmodium

Ring stage

Schizont

Macrogametocyte

Slide: Human malaria in liver tissue:Hemozoin (digested hemoglobin) deposited in the cells of the spleen in a human infected with malaria.   Slide: Sporozoite human malaria 

Class HeamosporidiaGenus Plasmodium

Genus: Haemoproteus Parasites of birdsSimilar life cycles to Plasmodium (but: no asexual stages in circulating blood cells; they remain in the tissues).The gamonts remain in the erythrocytes. . Slide: Haemoproteus columbiae gametocytes. This preparation is a blood smear collected from birds. Note that bird erythrocytes are nucleated. You will find Haemoproteus gametocytes in the cytoplasm of the red blood cells.    

 Genus: Haemogregarina are parasites of the blood of frogs, lizards and turtles, and are transmitted by leeches or mites. Related species occur in fish.  Slide: Haemogregarines gametocytes in frog blood.

Genus Haemoproteus & Haemogregarina

Haemogregarina sp.

Eimeria sp.Monocystis sp.

Plasmodium sp.

Learning Objectives1. Phylum Apicomplexa- General characteristics- Apical complex!!- 4 general components of Apicomplexan development2. Class Gregarina – Monocystis spp.- Visual Id – common cysts, oocysts, sporozoite- Trophozoite stages feeding on sperm- There is no schizogonic phase- Host + tissue infected3. Class Coccidia – Eimeria stiedae- Host, tissues infected, transmission- Life cycle- Visual id trophozoite, macrogametocyte, microgametocyte, liver/bile ducts4. Class Coccidia – Genus Sarcocystis- Host, tissues, life cycle, transmission- Visual id5. Class Coccidia – Genus Toxoplasma- Life cycle, transmission, hosts, tissues infected- Intestinal vs. extraintestinal phase (where they occur, in what species…)- Pathogenecity- Visual id - tachyzoites6. Class Haemosporidia – Genus Plasmodium- Life cycle – what is definitive host- Transmission,- Visual id different stages and how they fit in life cycle- Pathology vivax and falciparum- Hemozoin in liver tissue7. Genus Haemoproteus- Visual id gametocytes- Life cycle, host , transmission, etc.8. Genus Haemogregarina- Visual id, host, transmission

VocabularyApical complexSchizogonySyngamySporogonyMerogonyGamogonyOocystSporozoiteMeront/TrophozoiteMerozoiteMicrogametocyteMacrogametocyteZygoteBradyzoiteSarcocystTachyzoiteExoerythrocytic cycleErythrocytic cycleSporogonic cycleRing-form trophozoiteOokineteSchuffner’s dotsHemozoin