Sporozoans

1. Sporozoans Phylum Apicomplexa Plasmodium, Gregarina

3. Apicomplexans • Heterotrophs: Parasites living in animal cells • Cell-piercing structure made of microtubules • Reproduce sexually and asexually in host cells • Only gametes have flagella • Example: Plasmodium (malaria)

4. Phylum Apicomplexa (Sporozoa) • No obvious means of locomotion • Some have flagellated gametes • Class Sporozoea (Sporozoans) • All are obligate parasites of animals • Gregarina in mealworms • Plasmodium causes malaria • Complicated life histories involving many hosts • Most form oocysts • Produce sporozoites following sexual reproduction • All life stages are haploid except for 2N zygote

5. Apicomplexa • Named for the apical complex • Aids in penetration of host cells • Covered by pellicle and two plasma membranes Plasmodium

6. Apicomplexa • Cause parasitic disease in humans • Malaria (Plasmodium) • Coccidian diseases including: • Cryptosporidiosis (Cryptosporidium parvum) • Cyclosporiasis (Cyclospora cayetanensis) • Isosporiasis (Isospora belli) • Toxoplasmosis (Toxoplasma gondii) • Diseases in livestock cause large scale economic losses • Eimeria, Babesia, Theileria

7. Apicomplexa • Outer covering • Thick, triple outer layer which is very flexible, but nearly impervious to biological, and even to most chemical, agents. • First is the plasma membrane • Next is inner, double membrane made up of flattened alveoli sutured together. • Finally, the whole business is reinforced with the cellular equivalent of rebar -- longitudinal bundles of microtubules running from the apical complex back towards the posterior end of the cell.  These are cross-linked in some fashion. 

8. Apical Complex • Set of secretory and cytoskeletal structures that enables the young parasite to enter a host cell. • Several components • Two apical or polar rings • A conoid - an open cone of spiral rod-like elements • Polar ring of dense granular material that connects the ends of the longitudinal cytoskeletal microtubules • Rhoptries and micronemes; these are modified secretory vesicles. • Possess apicoplast (plastid)

9. Apicoplast • Organelle derived from endosymbiosis in which the apicomplexan ancestor engulfed a unicellular alga. • Contains its own genome, a circular molecule of DNA which encodes • ~ 30 proteins • a full set of tRNAs plus some other RNAs • Sequencing of apicoplast DNA shows it is closely related to chloroplasts (Chlamydomonas) • Potential drug target – kill malaria with herbicides!

12. Apicomplexa • Apical Complex • Rhoptries (rhoptry = sing.) and micronemes • Special secretory organelles of the apical complex that produce a large number of proteins • Protein functions: • Part of the machinery that is used by these parasites both for invasion and to commandeer host functions. • Modulate key regulators of the immune response of the host. • Responsible for motility, adhesion to host cells, invasion of host cells and establishment of the parasitophorous vacuole inside the host cell.

17. Plasmodium (Malaria) • Plasmodium species cause malaria

20. Malaria • Malaria is a mosquito-borne disease caused by several members of the genus Plasmodium. • People with malaria often experience fever, chills, and flu-like illness. • Left untreated, they may develop severe complications and die. • Each year 350-500 million cases of malaria occur worldwide, and over one million people die, most of them young children in Africa south of the Sahara.

22. Mosquito = vector - transmits the malaria parasite Plasmodium vivax(a sporozoan) Malaria parasite in red blood cells Parasites breaking out of red blood cells

23. Malaria • Humans infected with malaria parasites can develop a wide range of symptoms. These vary from • asymptomatic infections (no apparent illness), • to the classic symptoms of malaria (fever, chills, sweating, headaches, muscle pains), • to severe complications (cerebral malaria, anemia, kidney failure) that can result in death. • The severity of the symptoms depends on several factors, • species of infecting Plasmodium • human's genetic background • any acquired immunity to the parasite.

24. Malaria • This sometimes fatal disease can be prevented and cured. • Bednets, insecticides, and antimalarial drugs are effective tools to fight malaria in areas where it is transmitted. • Travelers to a malaria-risk area should avoid mosquito bites and take a preventive antimalarial drug such as chloroquine.

25. Malaria • Antimalarial drugs taken for prophylaxis by travelers can delay the appearance of malaria symptoms by weeks or months, long after the traveler has left the malaria-endemic area. • This can happen particularly with P. vivax and P. ovale, both of which can produce dormant liver stage parasites. • Liver stages may reactivate and cause disease months after the infective mosquito bite.

27. Anopheles mosquito vector

30. Malaria • The incubation period in most cases varies from 7 to 30 days. • The shorter periods are observed most frequently with P. falciparum and the longer ones with P. malariae. • The classical (but rarely observed) malaria attack lasts 6-10 hours. It consists of: • a cold stage (sensation of cold, shivering) • a hot stage (fever, headaches, vomiting; seizures in young children) • and finally a sweating stage (sweats, return to normal temperature, tiredness) • Classically (but infrequently observed) the attacks occur every second day with (P. falciparum, P. vivax, and P. ovale) and every third day with (P. malariae).

31. Malaria • Each attack starts with shaking chills, usually at mid-day between 11 a.m. to 12 noon, and this lasts from 15 minutes to 1 hour (the cold stage), followed by high grade fever, even reaching above 41oC, which lasts 2 to 6 hours (the hot stage). • The cycle corresponds to the toxins released during rupture of the schizont-infected red cells and release of large numbers of merozoites. • These toxins reset the hypothalamus gland’s temperature set point – chills help raise body temp to this new point. • The hot stage is followed by profuse sweating and the fever gradually subsides over 2-4 hours.

32. Toxoplasmosis Toxoplasma gondii Kinetoplastida

33. Toxoplasmosis • Parasite causes eye and brain damage in a baby, if untreated. • Acute infection in older children and adults may be without symptoms, cause flu like illness or enlarged lymph glands. • Latent parasite occurs very commonly in people infecting approximately a third to a half of all humans. • Can cause active disease if a person becomes immune compromised • Brain damage and death

34. Toxoplasma gondii • Clinical Features: • Generally an asymptomatic or mild self-limiting infection.  • Immunodeficient patients • Brain lesions, death • Pneumonitis • Pregnant women/infant • Miscarriage; still births • Cerebral palsey; seisures • Mental retardation • Eye infections; impaired vision • Enlarged liver and spleen

35. Gregarines • Apicomplexan (Sporozoan) parasites of insects. • Recall observations of these parasites in intestine of meal-worm larvae (Tenebriomolitor beetles). Gregarina polymorpha

36. Gregarines • Host consumes a sporozoite or sporocyst containing them • Sporozoite attaches to host intestinal epithelium with structure called epimerite • Transforms into feeding stage called trophozoite • Sexual stage begins when two trophozoites (gamonts) of opposite sex associate in syzyge • Produces a walled gametocyst which is expelled with the feces. • Within cyst the two gamonts divide to form many gametes which fertilize within the cyst to form a zygote called a sporocyst which undergo meiosis to form 1n sporozoites

38. Gregarina oosysts Gregarina in syzyge

39. Cryptosporidium • Causes Cryptosporidiosis • Obligate intracellular parasite • Causes diarrhea • Affects humans, cattle, sheep, dogs • No effective drug treatment for cryptosporidiosis • Antibiotics are contraindicated; supportive care only

40. Cryptosporidium • Major outbreaks in Milwaukee in 1993 and 1996 • Cause was failure in one of the water treatment pumping stations • Sewage backed up into drinking water • No required testing for Crypto under EPA stds. • Major cities now test for Crypto regularly

41. Cryptosporidium can be a problem in municipal water supplies. Cryptosporidium affects humans, dogs, and cattle

45. Ciliates Subphylum Ciliophora

47. Functional groupings of ciliates • Holotrich- uniform ciliation • Heterotrich- possess membranes &/or cirri • Peritrich- cilia only around the cytostome • Colonial-living in colonies • Suctorian- a clade of Ciliophora possessing hollow feeding tentacles

48. An assortment of freshwater ciliates- biodiversity! This figure shows 167 species- about 9500 species are known

49. Ciliophora (ciliates) • A major clade within the Alveolates. • Synapomorphies of ciliates include: • Ciliated pellicle and associated kinetodesmata • Dimorphic nuclei • conjugation • Primarily holotrophic- few parasitic. • Many can form cyst stage (resting stage).