Parasitology Comprehensive Reviewer PDF

N. Villanueva 1  N. Villanueva TABLE OF CONTENTS Intro to Para 3 Dracunculus medinensis 65 PROTOZOANS...

N. Villanueva 1  N. Villanueva TABLE OF CONTENTS Intro to Para 3 Dracunculus medinensis 65 PROTOZOANS Filarial worms 66 Pathogenic ameba 7 PHYLUM PLATYHELMINTHES: CLASS TREMATODA Commensal ameba 9 Schistosoma spp. 72 Free-living ameba 12 Paragonimus westermani 77 Intestinal flagellates 15 Fasciolopsis buski 79 Urogenital flagellates 20 Echinostoma ilocanum 80 Ciliates 23 Heterophyid worms 81 Blastocystis hominis 24 Fasciola spp. 82 Malarial parasites 25 Clonorchis and Opisthorchis 84 Other protozoans 34 Dicrocoelium dendriticum 86 PHYLUM ASCHELMINTHES: CLASS NEMATODA Eurytrema pancreaticum 87 Ascaris lumbricoides 50 PHYLUM PLATYHELMINTHES: CLASS CESTODA Trichuris trichiura 52 Diphyllobothrium latum 92 Enterobius vermicularis 54 Taenia spp. 94 Hookworms 55 Hymenolepis spp. 97 Strongyloides stercoralis 58 Dipylidium caninum 99 Capillaria philippinensis 59 Raillietina garrisoni 100 Anisakiasis 61 Echinococcus spp. 101 Animal Ascarids 62 Multiceps multiceps 103 Parastrongylus cantonensis 62 Trichinella spiralis 64 Laboratory Diagnosis 105 2  N. Villanueva INTRO TO PARA: FUNDAMENTALS OF PARASITOLOGY o Ex: Cockroaches and flies Accidental Host that harbors a parasite that usually BIOLOGICAL RELATIONSHIPS Host does not infect it Ex: Man infected with Toxocara canis Biological relationships Paratenic Also known as Transfer Host o Symbiosis: relationship between 2 unlike organisms Host Harbors parasites that do not develop to o Symbiont/Symbiote: the members of the symbiotic further stages relationship Only transfers from one host to another o Examples of Symbiotic Relationships Widens parasite distribution and bridges ▪ Mutualism: both benefit (Ex: termites and flagellates) ecological gap between definitive and ▪ Commensalism: one benefits, one is not intermediate hosts affected/unharmed (Ex: Entamoeba coli in the intestinal Ex: Boars for Paragonimus westermani lumen) Dead-end Also known as Incidental Host ▪ Phoretic relationship: one that involves “Phoresis” Host Host that does not anymore allow the life Phoresis: means “to carry” cycle of the parasite to continue The organism is carried and nothing else happens Ex: Humans for Trichinella spiralis Phoront: organism being carried Reservoir Host other than the parasite’s usual hosts No physiologic interaction is involved between the Host that allows the life cycle to continue host and the phoront Animals that can continue the life cycle Ex: Cockroaches carrying Ascaris eggs even in absence of humans ▪ Parasitism: one benefits (parasite) and one is harmed Becomes additional sources of human (host) infection Examples Ex: Entamoeba histolytica in humans o Pigs for Balantidium coli Parasitology: an area of biology that deals with the o Field rats for Paragonimus westermani dependence of one organism on another o Beavers for Giardia lamblia o Study of parasites, its hosts, and their relationships o Cats for Brugia malayi Characteristics of parasitic diseases o Prevalence in developing countries and in lower socioeconomic population PARASITES o Low mortality and morbidity (not deadly per se, usually neglected, very few people die) Obligate Parasite that always requires a host to survive o Limited drug development Most parasites o No current vaccines Ex: Ascaris, Hookworms, Trichuris, HOSTS Tapeworms Facultative Has a free-living and parasitic Host: species which harbors the parasite phase o May show no harmful effects Free-living: phase found in the o May suffer from the pathogenic effects of the parasite environment When conditions are unfavorable, Hosts enters the parasitic phase Final Host Also known as Definitive Host Ex: Threadworms Harbors the mature form of the parasite Commensal Non-pathogenic Sexual reproduction and maturity takes Does not cause disease places in these hosts Ex: Entamoeba coli Common FH are man Parasites According to Habitat Intermediate Harbors immature/larval form of the Ectoparasite Parasite lives outside the host Host parasite Infestation: presence of an Asexual reproduction takes place ectoparasite in a host Ex: Lower animals, vegetation, insects, Ex: Ticks, Lice, Fleas sometimes humans (in Plasmodium Endoparasite Parasite lives inside the host infections) Infection: presence of an Vectors Responsible for transmission endoparasite in a host Biologic Vector: there is morphologic Most parasites change or transformation of parasite Erratic Parasite Parasite not living in its natural before transmission to another host habitat o Parasite is always inside Ex: Ascaris (when it is not in the small o Ex: Aedes, mosquitoes, Tsetse fly, ticks intestine) Mechanical/Phoretic Vector: no Accidental Also known as an Incidental morphologic change occurs Parasite Parasite o Parasite always outside 3  N. Villanueva Parasite that does not live in its usual Water Borne Drinking contaminated water host Giardia, Cryptosporidium Spurious Free-living organism that passes Vertical Congenital transmission Parasite through the GI tract without infecting Transmission Toxoplasma gondii the host Transmammary Drinking of breast milk Temporary Transient parasites Ancylostoma, Strongyloides Permanent Remains on host for its entire life Skin Penetration Exposure of skin to soil or water Parasites According to Egg Laying Capacity Hookworms, Strongyloides, Oviparous Lays immature eggs (eggs not yet Schistosoma embryonated, egg has no larva yet) Inhalation Of airborne eggs Ex: Ascaris, Trichuris Enterobius Ovoviviparous Lays mature eggs (embryonated, Intimate Contact Sexual contact larva present) Trichomonas vaginalis Ex: Schistosoma, Clonorchis Larviparous Larva-laying Ex: Trichinella LIFE CYCLES Parasites According to Sexes Monoecious Also known as Hermaphrodites Life cycles: how the parasite develops Both testes and ovaries found in one Can be direct or indirect parasite Direct: no intermediate host, only consists of a parasite and Ex: Flukes and Tapeworms a final host Dioecious Presence of separate sexes Indirect: has an intermediate host Female and male parasite o Migration of larval stages present in some parasites Ex: Nematodes (except o Ex: Plasmodium Strongyloides) Life cycle more complicated = lesser chances for parasite to Parthenogenetic Females capable of self-fertilization survive Ex: Strongyloides stercoralis EXPOSURE AND INFECTION PARASITE STAGES Disease Presence of signs and symptoms Pathogen Any organism that causes disease Stages for Helminthes Infection Not equal to disease Adult Mature form Establishment of an organism in one Larva Immature form host (with multiplication of organism) Stages include L1-L3 No destruction of tissue yet Egg/Ovum Nonmotile form Carrier Harbors the organism, but person Resistant stages Infective stage (for most parasites): stage shows no signs or symptoms that once ingested, infects the host Also like a reservoir Stages for Protozoans Incubation Period between infection and Trophozoite Motile/vegetative stage Period appearance of signs and symptoms Cyst Nonmotile In this period, there are no symptoms Usually the infective stage AKA: Clinical Incubation Period Pre-patent Period between infection and Period evidence/demonstration of infection TRANSMISSION Positive lab result Soil Transmitted HATS Can be ahead of incubation period, or Helminthes Hookworms (Necator americanus lesser (STH) and Ancylostoma duodenale) AKA: Biologic Incubation Period Ascardis lumbricoides Exposure process of inoculating an infective Trichuris trichiura agent Strongyloides stercoralis Autoinfection infected individual becomes his/her Vector Borne Mosquitoes and ticks (arthropods) own source of infection Plasmodium, Hemoflagellates, parasite does not need to go outside Filarial worms body to replicate/multiply Food Borne When you are fond of eating Capillaria, Strongyloides, Enterobius, different types of food Cryptosporidium, Hymenolepis nana Undercooked or raw food Superinfection Also known as Hyperinfection Fasciola, Opisthorchis, Clonorchis, Infected individual is further infected Echinostoma, Heterophes, Taenia with the same parasite Strongyloides 4  N. Villanueva EPIDEMIOLOGY o High carbohydrates favors development of some tapeworms Epidemiology: study of patterns, distribution, and occurrence Natural physical barriers of disease o Skin: provides surface protection against invasion from parasites Prevalence Number of patients infected at one point in o Mucous membranes: provide external barriers to parasite time entry Cumulative Percentage of individuals in a population Prevalence o Tight junctions: between epithelial cells, prevent passage infected with at least one parasite of small molecules Incidence Number of new cases o Low pH of vaginal secretions and gastric juices: present Measures risk of developing the disease a hostile environment to microorganisms Sporadic Few cases Chemical components of body fluids Endemic Ongoing local transmission in one area o Lipase content of breast milk (toxic to Giardia) Epidemic Outbreak o Lysozyme in tears and saliva (with the IgA content): able Sudden increase in number of cases to destroy microorganisms Pandemic Whole world Worldwide epidemic Physiologic function of the body Eradication Permanent reduction to zero of worldwide o Peristalsis: motion of the cilia in the digestive tract helps in incidence of an infection expelling parasites Once achieved, continued efforts to reduce o Coughing: enables expectoration of certain parasites infections no longer needed Immunity and immune response Elimination Reduction to zero of incidence of a o Causes parasite to develop parasite evasion mechanisms specified disease in an area o Parasites eventually become resistant to the immune Continued intervention is needed response Morbidity Number of cases o Absolute immunity rarely happens Mortality Number of deaths o Host can also recognize the invading parasite through its Intensity of Severity of the infection pathogen-associated molecular patterns Infection Ex: worm burden in Ascaris ▪ Can also recognize through toll-like receptors (recognize specific molecules that are nonnative to the body, activated by bacterial components) EFFECTS OF PARASITE TO HOST PARASITE EVASION MECHANISMS May infect humans, but do not cause disease (commensals) Can cause injury by release of metabolites/enzymes Resistance to immune response (Entamoeba histolytica) Immune suppression Can cause invasion and tissue destruction Antigenic variation Can deprive certain nutrients from hosts (Diphyllobothrium o Variant surface glycoproteins (VSGs) latum: deprives humans of Vitamin B12 or Cyanocobalamin) o Variant surface proteins (VSPs) Tissue damage (Ex: fatty degeneration, albuminous o Parasite changes its surface proteins or glycoproteins to degeneration, necrosis) avoid detection by the immune system Tissue changes o Ex: Giardia and Hemoflagellates o Hyperplasia: increase in number of cells Host mimicry o Hypertrophy: increase in size of cells o Parasite can copy certain proteins/antigens in the body o Metaplasia: change from one cell type to another o Echinococcus granulosus larva: mimics the P antigen in o Neoplasia: formation of tumors or neoplasms the P blood group Streamlining: inability of parasite to synthesize certain Intracellular sequestration cellular components, so they need the help of the host to o Parasites hide inside the cell obtain these components o Ex: Plasmodium, Babesia, Leishmania EFFECTS OF HOST TO PARASITE TAXONOMY Genetic makeup of host Kingdom Protista Phylum Sarcomastigophora o Duffy Blood Group Fy(a-b-): confers resistance to (Protozoans) o Subphylum Sarcodina: ameba Plasmodium vivax and Plasmodium knowlesi o Subphylum Mastigophora: o Sickle Cell Anemia: confers resistance to Plasmodium flagellates (atrial flagellates and falciparum hemoflagellates) Nutrition and diet Phylum Ciliophora: ciliates o High protein diet inhibits growth of protozoans Phylum Apicomplexa: Plasmodium o Low protein diet favors development and appearance of o Possesses apical complex used for symptoms and complications of amebiasis invasion of host o Class Sporozoa (form spores) 5  N. Villanueva ▪ Suborder Haemsporina Community is treated irrespective of ▪ Suborder Eimeria: age, sex, infection status, etc. Cryptosporidium Preventive Regular, systematic, large-scale Capable of causing chemotherapy intervention through administration of Coccidiosis in animals one or more drugs to selected Kingdom Fungi Phylum Microsporidia population groups Intracellular parasites Coverage Proportion of target population reached by the intervention Now classified as fungi in Mycology Efficacy Effect of a drug Spore forming Effectiveness Measure of the effect of a drug Possesses a polar tube (used to Drug Genetically transmitted loss of penetrate the host cell) resistance susceptibility to a drug Ex: Enterocytozoon and Encephalitozoon Kingdom Phylum Aschelminthes PREVENTION AND CONTROL Animalia o Class Nematoda (roundworms) Phylum Platyhelminthes (flat worms) Morbidity Avoidance of illness caused by o Class Trematoda (flukes) control infections ▪ Order Digenea Information- Health education strategy o Class Cestoda (tapeworms) education- Aims to encourage people to adapt communication and maintain healthy life practices (IEC) TREATMENT Environmental Planning, organization, performance, management and monitoring of activities for Deworming Use of anthelminthic drugs in an medication or manipulation of individual or public health program environmental factors Cure rate Number of previously positive subjects Done to prevent or minimize vector or found to be egg negative intermediate host propagation Egg Reduction Percentage fall in egg counts after Also done to reduce contact between Rate deworming humans and infective agent Selective Individual-level deworming Environmental Intervention to reduce environmental Treatment Selection for treatment based on sanitation health risks presumptive grounds Includes safe disposal and hygienic Used in whole populations or defined management of human and animal risk groups excreta, refuse, and waste water Targeted Group-level deworming Sanitation Provision of access to adequate treatment Risk group to be treated may be facilities for safe disposal of human defined by age, sex, etc. excreta Universal Population-level deworming Treatment 6  N. Villanueva AMEBA, FLAGELLATES, & CILIATES PROTOZOANS Possess peripheral chromatin Nucleus is vesicular (looks like it has holes or spaces inside) Eukaryotic organisms (possesses nucleus and organelles) All are commensal except E. histolytica Varies in shape, size locomotion Reproduce asexually (binary fission) or asexually and STAGES OF DEVELOPMENT sexually (in Plasmodium species) Do not possess cell walls (only found in bacteria, plants, and Trophozoite: motile or vegetative stage fungi) o Seen in watery, loose, or mucus-filled stool Consist of nucleus and cytoplasm o Labile: breaks easily (especially in the absence of water) o Nucleus: genetic material o stains are added to visualize the nucleus ▪ Contains nucleolus or karyosome (RNA material) or ▪ buffered Methylene Blue (either Nair’s or Quensel’s) endosome Cyst: nonmotile stage o Cytoplasm: consists of 2 regions o Circular/round ▪ Endoplasm: for metabolism and nutrition o Resistant ▪ Ectoplasm: hyaline (clear) structure for protection o Infective stage for most ameba o Immature cyst: pre-cyst SARCODINA o Mature cyst: metacyst o Seen in formed stool (as stool is more formed, there are less Ameba trophozoites) Possesses pseudopodia used for locomotion o Stained with Lugol’s Iodine (I2) and D’Antoni’s Iodine Inhabits the large intestine except for E. gingivalis (inhabits ▪ Cannot be used for the trophozoite because iodine is toxic the mouth/oral cavity) PATHOGENIC AMEBA Life Cycle Ingestion of Cyst Cyst goes to stomach Excystation takes place pH should be alkaline or neutral (acidic pH does not favor formation of trophozoites) Multiplication of takes place in large intestine Trophozoites multiplication through binary fission usually produces 4 trophozoites from 1 cyst (but not for all organisms!) Trophozoites and whether trophozoites or cysts appear Cysts go to the depends on the type of stool (if formed stool or watery) Entamoeba histolytica MOT: ingestion of infective cyst Habitat: large intestine Only pathogenic amoeba Subphylum Sarcodina, superclass Rhizopoda, class Lobosea, order Amoebida, family Entamoebidae Cyst is resistant to gastric acidity and desiccation, can survive in a moist environment for several weeks Trophozoites multiply by binary fission Entamoeba species: spherical nucleus, distinct nuclear membrane lined with chromatin granules, small karyosome near center of nucleus Trophozoite Cyst Nucleus 1 nucleus (vesicular appearance) 4 nuclei (ideally) Karyosome Centrally located karyosome Small, centrally located karyosome Peripheral chromatin Fine, evenly distributed Fine, evenly distributed Appearance Clean-looking cytoplasm Thin wall, hyaline appearance, highly refractile Additional structures Finger-like appearance of pseudopodia Chromatoidal bar 7  N. Villanueva Hematophagus: presence of ingested RBCs Food reserve, energy stores (because the organism is invasive) Chemical composition: crystalline RNA Shape: sausage or cigar shaped *also has a glycogen vacuole Motility Unidirectional, progressive (moves from one point Nonmotile to another) Epidemiology Worldwide distribution More prevalent in tropics High risk groups: sexually active, MSMs, food handlers Non-pathogenic E. histolytica look-alikes o E. dispar o E. moshkovskii (also called Laredo strain) o E. Bangladeshi (all human isolates of this belongs to group ribodeme 2 o All morphologically the same with E. histolytica, but grows in room temp (E. histolytica grows at 37 degrees Celsius) o Can be differentiated through molecular techniques, isoenzyme analysis, zymodeme analysis, and checking the trophozoites for ingested RBCs Virulence Factors Molecules produced that add to their effectiveness and enable them to replicate and disseminate within a host Lectin (GaI, GaINAc Lectin) – for attachment Amebapores – holes on lining of large intestine Cysteine Proteinases – for tissue disruption and spread of infection (allows parasite to penetrate mucosa and adhere to underlying layer surrounding the tissues) Laboratory Diagnosis Ova and Parasite Examination of Stool o Minimum of three stool specimens collected on different days o Direct Fecal Smear ▪ Less sensitive because of the lower amount of stool (2 mg) ▪ Might give a negative result o Concentration Techniques ▪ FECT (Formalin ether concentration technique) ▪ Increase sensitivity of test, cyst can be recovered ▪ Merthiolate Iodine Formalin Concentration Test (MIFC) o Permanent Stained Smear ▪ Iron Hematoxylin (classic method) ▪ Trichrome Stain (what is used nowadays) ▪ Confirm presence of protozoan ▪ More detailed (you can see the chromatoidal bar) ▪ Saline and methylene blue: Entamoeba species will stain blue (differentiates them from WBCs) ▪ Saline and iodine: nucleus and karyosome observed (to differentiate from nonpathogenic amebae) o Charcot-Leyden crystals can be seen in the stool Culture o Boeck’s, Rice Egg Saline, Diamond, Balamuth’s Egg Yolk Infusion Serology (detection of antibodies) o ELISA (Enzyme-linked immunosorbent assay): uses antibodies and color change to identify a substance o IHA (Indirect hemagglutination): method for quantifying relative concentration of viruses, bacteria, or antibodies o Differentiation between E. histolytica and E. dispar o Counter immunoelectrophoresis (CIE), agar gel diffusion (AGD), indirect fluorescent antibody test (IFAT) Molecular methods Rectal biopsy (ulcer, H&E stain used) Examination of Liver Aspirates Ultrasound, CT scan, MRI for early detection of ALA Treatment and Metronidazole: drug of choice for symptomatic cases prevention Other 5-nitroimidazole derivatives: tinidazole and secnidazole Diloxanide Furoate: for asymptomatic cases Iodoquinol: alternative drug 8  N. Villanueva COMMENSAL AMEBAE Entamoeba coli Transmitted via ingestion of infective cyst More common than other human amebae Trophozoite Cyst Nucleus 1 nucleus 8 nuclei Karyosome Eccentric Eccentric Peripheral chromatin Coarse, rough Coarse, rough Appearance Dirty-looking Larger than E. histolytica, cytoplasm (contains thick cystic wall bacteria, debris, yeast) Additional structures Blunt, wider appearance of pseudopodia Chromatoidal bar Broom stick/witch broom/ splinter Motility Multi-/non-directional, non-progressive Nonmotile Entamoeba hartmanni Small race of E. histolytica Trophozoite Cyst Nucleus 1 nucleus 1-2 nuclei only (mature cyst can have 1-4 nuclei) Karyosome Centrally located Centrally located Peripheral chromatin Fine, evenly distributed Fine, evenly distributed Additional structures Pseudopod Diffuse glycogen (similar to E. vacuole/mass (not histolytica) seen in permanent stain) Motility Sluggish movement, non-progressive Nonmotile Entamoeba polecki Ameba of pigs and monkeys Most common parasite in Papua New Guinea May resemble other Entamoeba species Zoonotic infection: can be passed from animals to humans Trophozoite Cyst Nucleus 1 nucleus 1 nucleus Karyosome Centrally located Large, centrally located Appearance Almost the same appearance as E. histolytica Almost the same appearance as E. histolytica Additional structures Similar to E. Chromatoidal bar histolytica Angular/pointed appearance Motility Unidirectional, progressive, sluggish Nonmotile Entamoeba chattoni Seen in apes and monkeys Use molecular techniques and isoenzyme analysis to differentiate from E. polecki Morphologically similar to E. polecki 9  N. Villanueva Endolimax nana Smallest intestinal amebae (as small as RBC, 6-8 um) Commensal Endolimax: vesicular nucleus with a relatively large, irregularly shaped karyosome Trophozoite Cyst Nucleus 1 nucleus 4 nuclei Karyosome Large, irregular Large, prominent, blot-like Peripheral chromatin None None (this is only found in Entamoebas!) Appearance Ingested bacteria, Oval, cross-eyed blunt and hyaline pseudopodia, food vacuoles are also present (which may contain bacteria) Motility Unidirectional, non-progressive, sluggish Nonmotile movement Iodamoeba butschlii ameba of swine (pigs) large, chromatin-rich karyosome surrounded by a layer of achromatic globules and anchored to the nuclear membrane by achromatic fibrils Trophozoite Cyst Nucleus 1 nucleus 1 nucleus Karyosome Large, eccentric Large, eccentric Peripheral chromatin None None Appearance “Basket of Oval, also has Flowers” basket of flowers appearance appearance (due to achromatic granules), triangular shaped Additional structures Glycogen vacuole (Iodine used to visualize this) Glycogen vacuole (Iodine used to visualize this) Motility Sluggish, non-progressive Nonmotile Entamoeba gingivalis NO CYST STAGE Ameba of oral cavity (gum line) Also found in tartar, gingival pockets of teeth, and tonsillar crypts (of unhealthy mouths, but may also be in healthy mouths) May also be seen in the genital tract Scavengers, eat debris Can also ingest RBCs (but it’s rare) Transmitted via direct-contact (kissing, sharing of personal items) First amoeba in man Can be seen in sputum sample (can go to the lungs) Also found in AIDS patients Found even in healthy people Non-pathogenic, but can be seen in patients with pyorrhea alveolaris (gum infections) Trophozoite Nucleus 1 nucleus Peripheral chromatin Fine, evenly distributed Additional structures Capable of ingesting WBCs Numerous, blunt pseudopodia Numerous food vacuoles that contain cellular debris (mostly leukocytes from the ingested WBCs) 10  N. Villanueva DISEASES OF AMEBAE FOUND IN HUMANS Entamoeba histolytica Disease manifestation Signs and Symptoms Asymptomatic Carrier State Excrete cysts (90% of cases) Intestinal Disease (10% of Incubation period: 1-4 weeks cases) Bloody diarrhea, dysentery (majority of cases), abdominal pain, flatulence, weight loss, chronic fatigue Release of enzymes to lyse mucosal lining Formation of flask-shaped ulcers by the trophozoites Excess mucus in stool Tenesmus: cramping rectal pain 10 bowel movements per day Clinical Forms: o Fulminating Colitis (inflammation of colon) ▪ Can lead to perforation and secondary bacterial peritonitis (most serious complications) o Amebic Appendicitis o Ameboma (granulomas, chronic inflammations, can be mistaken as carcinomas or cancer) Extra-intestinal Disease (usually Ectopic form of amebiasis affects the upper lobe of the Amebic Liver Abscess (ALA): liver aspirate (like anchovy sauce) where you can find liver because blood vessels are trophozoites connected to the small o Can lead to rupture into the pericardium, rupture into the pleura, super infection, and intestine) intraperitoneal rupture Cardinal signs: fever and right upper quadrant pain Tender liver (tender: painful when you touch or palpate) Hepatomegaly (abnormal enlargement of liver) Cutaneous Amebiasis (amebiasis cutis): rare, infection of skin and soft tissue Skin rupture Affects inguinal areas Can be transmitted sexually *amebiasis is characterized by low amount of WBCs in stool Can cause lung abscess (found in sputum) and brain abscess Secondary amebic meningoencephalitis (occurs in 1-2%) Renal involvement is rare Genital involvement o Caused by fistulae from ALA and colitis or primary infection through sexual transmission Amebiasis IS DIFFERENT from bacterial dysentery In amebiasis, there is mucus and blood in the stool There is no granulocytosis and no high fever There is also a fishy smell of the stool Laboratory Diagnosis for Commensal Amebae Stool examination FECT and iodine stain useful to differentiate the species E. gingivalis: swab between gums and teeth (examined for trophozoites) DFS Concentration techniques (FECT and zinc sulfate flotation) useful for recovering cysts *no treatment necessary for commensal amebae (they do not cause disease) 11  N. Villanueva FREE-LIVING PATHOGENIC AMEBAE Found inhabiting lakes, pools, tap water, air conditioning units, and heating units Parasites are facultative (with a free-living and parasitic phase) Life Cycle Person swims in Parasite enters via olfactory region contaminated Parasite can also enter through the skin water Parasite cannot survive in salt water Infective stage: trophozoite Trophozoite goes Targets the CNS straight to the brain Brain tissue or CSF can be examined Naegleria fowleri Belongs to family Vahlkampfiidae Free-living ameboflagellate (has an ameba and flagellate form) Only Naegleria species that can infect humans Thermophilic: thrive best in hot springs and other warm aquatic environments Trophozoites replicate by promitosis Cyst found only in the environment Enters the body through the olfactory epithelium, respiratory tract, and the skin and sinuses Targets the brain tissue (trophozoite goes straight to the brain) Cyst: spherical and single-walled Trophozoite: 1 nucleus, large and dense karyosome, cytoplasm is granular and contains many vacuoles o Ameboid form: Limax-form (slug-like) o Ameboflagellate: 2 anterior flagella Trophozoites also characterized by blunt, lobose pseudopodia and directional motility Disease Manifestation Primary Amebic Meningoencephalitis (PAM) and Pathology o Inflammation of meninges in the brain o Can affect healthy people, fast progression o Very fatal o When you swim in contaminated pools, lakes, and rivers o Signs and symptoms: headache, fever, nausea, vomiting, nuchal rigidity, rhinitis, lethargy, olfactory problems, mental status changes, mental confusion, coma o Incubation period: 2-3 days or 1-2 weeks o Patients usually dead after 1 week o Brain has hemorrhaging (has lots of WBCs, especially neutrophils) o Usually diagnosed post-mortem o Few cases in the PH, usually in US Pathogenic determinant (virulence factor) o Presence of amebostomes (food cups) o Used to attach to the brain o Releases enzymes (phospholipases) to destroy brain tissue o Other pathogenic determinants include (produces a cytopathic effect on host tissues): ▪ Secretion of lytic enzymes ▪ Membrane pore-forming proteins ▪ Induction of apoptosis ▪ Direct feeding of the ameba Laboratory Diagnosis Wet mount examination of CSF (look for trophozoite) Smears stained with Wright’s or Giemsa Biopsy of tissue CSF Analysis o Nonspecific for N. fowleri 12  N. Villanueva o Decreased CSF glucose o Increased protein o High WBC (neutrophilic predominance) Culture (Bacteria Seeded Agar Culture), Modified Nelson’s Medium Molecular methods Treatment and Amphotericin B with Clotrimazole prevention New agents: Azithromycin, Voriconazole Most die before effective treatment o Symptoms of PAM indistinguishable from bacterial meningitis o Patients usually treated with antibiotics, which have no effect on Naegleria Avoid diving and swimming into warm and stagnant freshwater pools, water discharge, and unchlorinated pools Life Cycle Parasite enters through Goes to brain and affects CNS the nose Parasite enters through Causes blindness the eyes Parasite enters through Causes lesions on the skin (especially in AIDS ulcerations in the skin patients) Reproduce in the body Through mitosis Acanthamoeba spp. Family Acanthamoebidae Acanthamoeba castellani (most common); A. culbertsoni; A. hutchetti; A. polyphaga; A. rhysoides Free-living ameba Aquatic organism Found in a myriad of natural and artificial environments Can survive even in contact lens solutions Entry can occur through the eyes, nasal passages to the lower respiratory tract, or ulcerated or broken skin Possible reservoir hosts for medically important bacteria such as Legionella spp., mycobacteria and gram-negative bacilli such as E. coli Both trophozoite and cyst are its infective stages Trophozoites reproduce by binary fission Trophozoites o Eats gram negative bacteria, blue-green algae, or yeasts o Can adapt to feed on corneal epithelial cells and neurologic tissue ▪ through phagocytosis and secretion of lytic enzymes Trophozoite transforms to cyst when environmental conditions are unfavorable Trophozoite Cyst Nucleus Single large nucleus Single large nucleus Karyosome Centrally located, densely staining Large karyosome Additional structures characteristic “thorn-like” appendages (acanthapodia) Double-walled cyst o “Acantha”- spring o Outer wall: wrinkled o “Spring projections of the pseudopod” o Inner wall: polygonal o For locomotion o Evident on phase-contrast microscope Contractile vacuoles Large endosome Finely granulated cytoplasm Eats gram negative bacteria Can eat the host’s tissues 13  N. Villanueva Disease Manifestation Acanthamoeba Keratitis and Pathogenesis o Parasite enters through eyes o Acanthamoeba was first described in 1974 as an opportunistic ocular surface pathogen o Associated with use of improperly disinfected soft contact lenses o Symptoms: severe ocular pain, blurring vision, corneal ulceration with progressive corneal infiltration o Primary amebic infection or secondary bacterial infection may lead to hypopyon formation o May lead to scleritis and iritis, and vision loss o Can be mistaken for herpes keratitis (to differentiate, herpes has no ocular pain) Granulomatous Amebic Encephalitis (GAE) o Stamm in 1972- documented Acanthamoeba as causative agent of human GAE using indirect fluorescence microscopy o Disseminated disease in lungs and brain o Usually occurs in immunocompromised hosts (chronically ill and debilitated patients, those on immunosuppressive agents like chemotherapy and antirejection medications) o AIDS patients have the highest risk of acquiring this o Incubation period: 10 days o Chronic, slow in progression (long-standing) o Signs and symptoms: destruction of brain tissue, meningeal irritation, fever, malaise, anorexia, increased sleeping time, severe headache, mental status changes, epilepsy, and coma o Incubation period: approximately 10 days o Normally results in coma or death (has poor prognosis) Cutaneous Lesions o Presence of hard erythematous nodules or skin lesions o Common in AIDS patients o Parasite enters through skin Laboratory Diagnosis Granulomatous Amebic Encephalitis (GAE) o Usually diagnosed after death/ post-mortem o AIDS patients have the highest risk of acquiring this o Not as common as other infections of the CNS like Cryptococcus meningitis and toxoplasmosis o Can rarely be demonstrated in Cerebrospinal fluid Acanthamoeba Keratitis o Epithelial biopsy or corneal scrapings (stained with Calcofluor White, then viewed under the fluorescence microscope) o Caused by A. castellani; A. culbertsoni; A. hutchetti; A. polyphaga or A. rhysoides Culture: Cubertson’s Medium; Non-nutrient medium with Gram negative bacteria (usually Escherichia coli) Molecular methods Treatment Very fatal once cerebral manifestations appear Fluorocystine, Ketoconazole, Amphotercin B Acanthamoeba Keratitis o Early recognition with anti-amebic agents can preclude the need for extensive surgery o Clortrimazole combined with pentamidine, isethionate, and neosporin (accdg. To D’ Aversa) o Polyhexamethylene biguanide, propamidine, dibromopropamidine isethionate, neomycin, paramomycin, polymyxin B., ketoconazole, miconazole and itraconazole o Avoid tropical corticosteroids (retard the immune response) o Advanced forms require debridement o Deep lamellar keratectomy (procedure of choice) Granulomatous Amebic Encephalitis (GAE) o Combination of amphotericin B, pentamidine isethionate, sulfadiazine, flucytosine, fluconazole or itraconazole o Decompressive frontal lobectomy and treatment with amphotericin, cotrimoxazole, and rifampin (could work too) Prevention Exposure is unavoidable Sanitation (best way) Infection can be prevented by a robust immune system, except in immunocompromised areas like cornea Avoid rinsing of contact lens in tap water Prolonged heating and boiling kill amebic trophozoites and cyst forms Find disinfectants that are more resistant than chlorine 14  N. Villanueva Balamuthia mandrillaris Family Leptomyxidae New species causing amebic meningoencephalitis Also causes Granulomatous Amebic Encephalitis (GAE) Cysts have a characteristic wavy appearance Trophozoites are branching Almost the same appearance with Acanthamoeba Both cysts and trophozoites can be seen in the brain (when infected) Other free-living ameba that causes amebic encephalitis Sappinia diploidea Hartmanella vermiformis – considered now as opportunistic INTESTINAL FLAGELLATES All inhabit the large intestine, except Giardia lamblia (small intestine), Trichomonas vaginalis (urogenital), Trichomonas tenax (mouth) All undergo encystation, except Trichomonas species and Dientamoeba fragilis All are commensals except Giardia lamblia, Dientamoeba fragilis, Trichomonas vaginalis Flagella is attached to the blepharoplast found on the body of the parasite All undergo asexual reproduction through binary fission Life Cycle Ingestion of cyst Released in the small intestine Excystation takes place Reproduction Reproduce through binary fission takes place in the (longitudinal) small intestine Parasite passed in Either cyst or trophozoite the stool Depends on type of stool Giardia lamblia Also known as G. duodenalis and G. intestinalis Mode of transmission: ingestion of infective cysts (from fecally contaminated water or food) Zoonotic Habitat: small intestine (duodenum, jejunum, and upper ileum), only one in the small intestine, the rest of the intestinal flagellates are located in the large intestine Low infective dose (only need to ingest around 8-10 cysts to be infected, reason for outbreaks of diarrhea) Beavers: reservoir hosts Reproduce by binary fission, longitudinal Prefers alkaline pH (7.8-8.2), the more alkaline, the more it attaches Trophozoite Cyst Nuclei 2 nuclei (ovoidal) 4 nuclei Appearance Pear/pyriform shape, old man’s face with Refractile/clear cyst wall (hyaline), oval shaped eyeglasses Additional structures Axostyle Median/parabasal bodies (2) ▪ For support ▪ Energy structures 1 pair anterior flagella Axoneme (multiple axostyles) 2 pairs lateral flagella Deeply stained curved fibrils 1 pair conal/posterior flagella 2 Ventral sucking discs (virulence factor) 15  N. Villanueva *also has median/parabasal bodies (it has a clawhammer shape) Motility “Falling Leaf Motility” Nonmotile Disease Giardiasis Traveller’s Diarrhea (can also be caused by E. coli) Backpacker’s Diarrhea Beaver Fever Gay Bowel syndrome Incubation period: 1-4 weeks (average 9 days) Explosive Watery Diarrhea Abdominal pain Excessive flatulence If not treated promptly, will result in Chronic Diarrhea o Recurrence of loose (greasy, frothy) foul-smelling stools (odor of rotten eggs due to hydrogen sulfide) o Steatorrhea: abnormal quantities of fat in the stool o Electrolyte loss o Weight loss o Malaise o Low grade fever Pathology Alteration of mucosal lining o Ventral sucker (virulence factor) o Lectin (type of sugar that helps attach to small intestine) Leads to Villous Flattening and Crypt Hypertrophy o Malabsorption and maldigestion Presence of VSPs Can rearrange cytoskeleton in human colonic and duodenal monolayers Has the ability to disrupt cellular tight junctions and increase epithelial permeability Epidemiology Worldwide Common in children (day care centers), crowded places, mental institutions, travelers, and the people who clean the septic tank Increasing cases among MSMs (Gay Bowel Syndrome) Sewage and irrigation workers at risk Prevalent among humans: assemblage A&B Blood Type A: higher risk Laboratory Diagnosis Usual specimens: stool/feces Collect 3 specimens in the span of 10 days DFS (to find trophozoites and cyst) Concentration techniques (FECT) Stained smears (permanent) Entero-test o Usually done if you are negative in DFS o Beale’s String Test o Swallow a capsule (has string and yarn inside) o Loose end placed on face o Yarn will go to the duodenum (where the parasites are) o After 4 hours, pull the string o Prepare smear from the string and look for the parasite o String should be green Duodenal aspirates 16  N. Villanueva Serology Molecular methods Biopsy o Tissue from intestine o Check for flattening of villi Treatment and Drug of choice: metronidazole Prevention Alternative drugs: tinidazole, furazolidone, albendazole Wash hands Proper sanitation and hygiene Proper and sanitary disposal of human excreta (to prevent contamination of food and water supply) Chlorine cannot kill cysts o Use iodine to disinfect water Life Cycle Ingestion of Goes to the large intestine trophozoites Reproduction takes Replicates by binary fission place Trophozoites will be located in the lumen of the colon Parasite passed in the Only trophozoite stool Transmission can occur via helminth eggs (Ascaris and Enterobius) Dientamoeba fragilis Formerly classified as an ameba Now an ameboflagellate No cyst stage, infective stage is the trophozoite Habitat: colon/large intestine Mode of transmission: oral fecal (ingestion of trophozoites) Relative of Trichomonas Usually ingested with Enterobius and Ascaris ▪ acts as carriers of D. fragilis reproduction through binary fission high prevalence in developed countries with high sanitation standards (Israel, Holland, Germany, etc.) Trophozoite Nucleus 2 nuclei (hence Dientamoeba) Karyosome Rosette/rose-like Appearance sometimes not detected/seen ▪ fragilis – fragile ▪ its easily destroyed Additional structures May have ingested bacteria NO VISIBLE FLAGELLA ▪ Only called a flagellate because its structures are similar to what flagellates have Pseudopodia (angular appearance) Pseudopodia produces non-progressive movement 17  N. Villanueva Symptoms of infection Gastroenteritis Diarrhea Abdominal pain Anorexia (loss of appetite) Nausea Vomiting Fatigue Weight loss Laboratory Diagnosis Multiple fixed and stained fresh stool samples Purged stool specimens Prompt fixation with polyvinyl alcohol or Schaudinn’s fixative Treatment Iodoquinol Other drugs: tetracycline and metronidazole Life Cycle Ingestion of cysts Parasite goes to the colon/large intestine and develops and reproduces Parasite is passed Cysts usually contaminates food, water, in the feces hands of people, and other fomites Chilomastix mesnili Commensal parasite of the colon/large intestine (cecal region) Infective stage: cyst (ingestion) Excystation happens in the small intestine ▪ Trophozoites then go to the large intestine Worldwide distribution No treatment indicated Prevention and control measures: improved sanitation and personal hygiene Trophozoite Cyst Nucleus 1 nucleus, with prominent karyosome 1 nucleus Appearance Pyriform, pear-shaped, curved posture, twisted jaw American lemon appearance appearance Nipple-shaped cyst 7-10 um in size Additional structures 3 anterior flagella Hyaline knob (protruding structure) 1 flagella near cytostome (mouth of the parasite) Cytostomal fibril (shepherd’s crook appearance) 18  N. Villanueva Spiral groove Cytostomal fibril (shepherd’s crook) Motility Boring/Rotary/Corkscrew, Spiral forward Nonmotile Enteromonas hominis Commensal Almost the same life cycle as Chilomastix Mode of transmission: ingestion of cysts o Contamination of water, food, or hands/fomites with infective cysts Trophozoite Cyst Nucleus 1 nucleus 2 or 4 nuclei (located at ends of the cyst) Appearance Oval-shaped Oval-shaped 3 anterior flagella 1 posterior flagella Motility Jerky motility Nonmotile Retortamonas intestinalis Commensal Mode of transmission: ingestion of cysts Same life cycle as E. hominis o Contamination of water, food, or hands/fomites with infective cysts Trophozoite Cyst Nucleus 1 nucleus 1 nucleus Appearance 1 anterior and 1 posterior Pear-shaped or slightly flagella lemon-shaped Cytostomal fibril o Bird’s beak Cytostome: cleft-like appearance Motility Jerky motility Nonmotile 19  N. Villanueva UROGENITAL FLAGELLATES Trichomonas vaginalis Pathogenic and largest (among the three species) Causes Trichomoniasis (STD, affects both males and females) Habitat: Urogenital Area (females: vagina, males: urethra and prostate) Mode of transmission: intimate contact, infant delivery (during delivery only, not vertical transmission and not transmitted via the placenta), contaminated towels and underwear No cyst stage Reproduces by longitudinal binary fission Most prevalent nonviral sexually transmitted infection Trophozoite Nucleus 1 nucleus Appearance Pyriform, Pear-shaped Additional structures 4 anterior flagella 1 flagella embedded in the undulating membrane Axostyle Cytostome Undulating membrane o Found on the lateral portion o Wave-like structure o For motility o Length is crucial for identification o ½ of body length o Attached to body of parasite via costa ▪ Rib-like structure ▪ Distinct for this parasite Siderophil granules o Also known as paraxostylar granules o Iron-rich o Near axostyle o No distinct function (only for identification) Vacuole with bacteria Motility Jerky tumbling motility Disease Manifestation Incubation period: 4-28 days Proliferating colonies cause degeneration and desquamation of vaginal epithelium (followed by leukocytic inflammation of the tissue layer) Females: mostly symptomatic (70%) o Vaginal pruritus (vaginal itching), with a burning sensation o Mucopurulent discharge: frothy, yellow, or green ▪ Mucopurulent discharge is the emission or secretion of fluid containing mucus and pus (muco- pertaining to mucus and purulent pertaining to pus) from the eye, nose, cervix, vagina or other part of the body due to infection and inflammation o Dysuria (painful urination) o Lower abdominal pain o Atypical pelvic inflammatory disease ▪ Can lead to sterility o Strawberry cervix: inflamed cervix ▪ Red dots can be seen (hemorrhages) o Secondary bacterial infection of the urogenital tract o When acute condition changes to the chronic stage, secretion loses purulent appearance due to decreases in trichomonads and leukocytes, increase in epithelial cells, and establishment of a mixed bacterial flora o Trichomonads associated with postpartum endometritis Males: mostly asymptomatic o Few symptomatic males show non-gonococcal urethritis, epididymitis, prostatitis o When not treated: can lead to sterility Infants: can get neonatal pneumonia 20  N. Villanueva o From infected moms Pathology Uses adhesins to bind to vaginal epithelial cells o Attachment to body surface o Adhesins have enzymes that promote tissue disruption Immune evasion o Presence of VSPs o Surface coating with host proteins o Shedding of parasite proteins Secretion of cysteine proteinases Cell detaching factor – cytopathic effect Alkaline pH (of the vagina promotes infection) Epidemiology STD infection Found worldwide Humans: only natural host Increased susceptibility to HIV o Because of inflammation o Also because they are sexually active (high-risk individuals) Symbiotic relationship with Mycoplasma hominis o Bacteria that causes STDs Prevalence higher among women of child-bearing age Laboratory Diagnosis Wet Mounts of vaginal and urethral discharge (can also use urine samples) o To check motility o Low sensitivity Stained smears (Giemsa or Pap’s) Culture: Diamond modified medium, Feinberg Whittington, Cysteine Peptone Liver Maltose, Simplified Trypticase Serum Semen Culture o Gold standard, takes 2-5 days o Best results seen with combination of urethral swabs and urine sediment Antigen detection Serology Molecular methods PCR (detects more cases with men than women) InPouch™ TV: allows specimen to be inoculated into a sealed pouch with culture media Treatment and Metronidazole prevention Tinidazole Have a monogamous relationship Abstinence Be faithful to your partner Pentatrichomonas hominis Commensal Formerly known as Trichomonas hominis Penta: has 5 flagella Habitat: colon Trophozoites found in contaminated food, water, or hands/fomites Trophozoite Nucleus 1 nucleus Additional structures 4 anterior flagella 1 posterior flagella Conical cytostome 21  N. Villanueva Axostyle No peripheral chromatin Undulating membrane o Full body length Motility Jerky motility Trichomonas tenax Commensal Habitat: mouth (tartar of teeth, cavities of carious teeth, necrotic mucosal cells in gingival margins) Mode of transmission: direct contact (kissing) or use of contaminated glass or dishes (sharing of utensils) Generally harmless o Though there are reports of respiratory infections and thoracic abscesses in cancer and other immunocompromised patients or in patients with other lung diseases o Pulmonary trichomoniasis reported among those with underlying chronic pulmonary disease o Parasite probably unable to cause disease on its own o Presence of bacteria most probably allows it to proliferate profusely Smallest among the species Resistant to changes in temperature Will survive for several hours in drinking water Diagnosis through swabbing tartar between teeth, gingival margin, or tonsillar crypts Treatment: metronidazole Trophozoite Nucleus 1 nucleus Appearance Pyriform Additional structures 4 anterior flagella 1 posterior flagella Axostyle Cytostome Undulating membrane o 2/3 body length Motility Jerky motility 22  N. Villanueva CILIATES Balantidium coli Largest protozoan infecting man Hosts: man (pigs usually reservoir hosts, zoonotic) Mode of transmission: ingestion of cysts Habitat: colon (cecum) Risk factors: close contact with pigs (in pig feces) Cysts found in fecally contaminated food or water Only ciliate known to cause human disease Trophozoite Cyst Nucleus 2 nuclei 2 nuclei (micronucleus and macronucleus), unlike in Micronucleus: For sexual reproduction amebae, encystation does not result in an increase of o lies in concavity of macronucleus nuclei Macronucleus: Kidney-shaped o for asexual reproduction and vegetative function Mucocysts o Extrusive organelles o Located beneath cell membrane Appearance Ellipsoid, tapered in anterior portion Spherical/Ellipsoidal (oval) Additional Cytostome (can be found by observing the Cyst wall structures tapered portion, since the anterior portion is o Double-walled tapered) o Refractile (shiny) o Oral apparatus Cilia is enclosed within the cyst wall o Through which it acquires food Cytopyge (anus) o Through which it excretes waste Contractile vacuoles: for osmoregulation Food vacuoles Cilia Motility Thrown-ball motility Nonmotile Disease Incubation period: 4-5 days Manifestation Causes Balantidiasis or Balantidial Dysentery o Bloody Diarrhea o Flask-shaped ulcers (wider and rounded) o Extraintestinal spread may occur Virulence factor: hyaluronidase o Lytic enzyme that causes ulceration Presence of Salmonella has been shown to aggravate Balantidiasis (by invading ulcers caused by the protozoan) Three clinical manifestations o Asymptomatic ▪ Do not present diarrhea ▪ Serve as parasite reservoir o Acute Cases (Fulminant Balantidiasis) ▪ Diarrhea with bloody and mucoid stools ▪ Often associated with immunocompromised and malnourished states o Chronic Cases ▪ Diarrhea may alternate with constipation ▪ Accompanied with abdominal pain, cramping, anemia, and cachexia Can spread to extraintestinal sites o Mesenteric nodes o Appendix o Liver o Genitourinary sites o Pleura 23  N. Villanueva o Lungs Complications include intestinal perforation and acute appendicitis Laboratory Direct examination or concentration techniques Diagnosis o Sedimentation or floatation o Feces with trophozoites and cysts Biopsy specimens (from lesions obtained through sigmoidoscopy) Bronchoalveolar washings (in case of pulmonary infection) Epidemiology Prevalence (0.02% to 1%) Uncommon among humans Common in institutionalized patients (in overcrowded institutions) Areas with poor sanitation People at risk: those in close contact with pigs or pig feces Warm and humid climates in tropical and subtropical countries can contribute to cyst survival Treatment and Metronidazole, Iodoquinol Tetracycline prevention Avoid using pig feces as fertilizer BLASTOCYSTIS HOMINIS Currently a commensal of the GI tract Blastocystis hominis Classified member of Stramenopiles Suggested new class: Class Blastocystea Previously classified as a yeast in Schizosaccharomyces Also previously associated with Blastomyces MOT: ingestion of thick walled cysts Life cycle still not fully understood Morphologic Forms Classic Vacuolated Form (Central-Body Form): most predominant o Large central vacuole pushes the cytoplasm to the periphery Granular forms: multinucleated Multivacuolar Avacuolar Ameboid form: exhibit active extension and retraction of pseudopodia o Nuclear chromatin exhibits peripheral clumping o Intermediate stage between vacuolar and precystic form Cyst: has a thick, osmophilic, and electron dense cystic wall Disease Manifestation Blastocytosis Pathology is still in question and controversial Diarrhea, nausea, anorexia May also be associated with irritable bowel syndrome Epidemiology Occurs worldwide Zoonotic Most common subtype infecting man is subtype 3 Lab Diagnosis DFS FECT Molecular methods Stains Culture: Boeck and Drborhlav Treatment Still controversial Usually use metronidazole 24  N. Villanueva MALARIAL PARASITES Intracellular protozoans o schizogony in the RBCs Phylum Apicomplexa, Class Sporozoa, Suborder o not a true relapse Haemosporina Erythrocytic cycle Undergoes alternating sexual (sporogony) and asexual Merozoites from start of erythrocytic schizogony stages (schizogony) in its life cycle liver infect merozoites develop into an immature RBCS trophozoite form Vector borne (Female Anopheles minimus flavirostris) o ring-form Intermediate host: MAN o red chromatin dot and ring of Habitat: Liver and RBCs of humans cytoplasm (scant amount) stained Infective stage to mosquito: gametocytes bluish with Giemsa Infective stage to man: sporozoites o large chromatin mass present and a MOT: Mosquito bite, blood transfusion, congenital prominent ameboid cytoplasm (spread throughout erythrocyte) ring form develops into a developing trophozoite developing trophozoite develops into a mature trophozoite mature merozoites enclosed in another schizont schizont formed when the large chromatin mass has divided into two or more masses of chromatin with small amounts of cytoplasm o clumps of pigment accumulate in middle of mature schizont Bursting of merozoites released schizont infects other RBCs Gametogony after many cycles, gametocytes are produced factors that trigger this are not completely understood macrogametocyte: female Exo-erythrocytic cycle Can also be called pre-erythrocytic cycle microgametocyte: male Mosquito bites human, injects sporozoites gametocyte characterized by a large chromatin mass with a blue cytoplasm Sporozoites now in blood stream with pigment o must reach liver within 30-40 minutes (cannot stay long