Intro to Med Para

November 2, 2018 | Author: Pinay Yaun | Category: Parasitism, Public Health, Earth & Life Sciences, Biology, Wellness
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Subject: Microbiology Topic: Introduction to Medical Parasitology Lecturer: Victoria Basa-Dalay, MD, MSc Date of Lecture: June 28,2011

Transcriptionist: Pages: 17

Symbiosis (living together) From the Latin word: sym - living together bio - life An association between two different species of  organisms Primarily aim for obtaining food or shelter from one or both member of the relationship Has no overtones of benefit or harm Includes a wide diversity of associations Most Important Symbiotic Relationships: y Commensalism - one benefits from the association while the other is unharmed

Why study parasites? Parasites provide unique examples of biological phenomena not found in free-living organisms. Because of their medical importance Humans are hosts to many species of parasites. Many of these parasites are causative agents of  major public health problems of the world. Recent estimates of the number of people infected with parasites in the world are: a re: Ascaris 1.3 B Hookworms 1.3 B

   2    1    0    2      1    1    0    2    Y    S

Competes for available nutrients since it

absorbs sugars, proteins and fats from the food  Obstructs the gut by bolus of worms  Damages vital organs during erratic migration  Acsaris can penetrate any hole (ears, anus, mouth, common bile duct, appendix, etc)

SURVIVAL FACTORS OF PARASITES Parasites have successfully adapted to (all?) environmental niches in hosts Parasites best adapted are least pathogenic Not sensed by the body as foreign just like an antigen but they will reside inside the body just like a commensal initially and when they grow up they become a parasitic agent. Typically with long -term/chronic/intimate parasite-host relationships of Parasites

2. Means of transmission from infected to susceptible, new hosts 3. Ability to invade and successfully reside in new hosts 4. Ability to reproduce

Definition Host The bigger organism in which the parasite depends their survival Provides the nourishment and protection in a form of shelter whether inside or outside the body May transfer or harbor the organism temporarily or permanently Provide appropriate environment for growth and reproduction Maybe harmed, killed, not affected or they may even benefit in association with other organism ypes of Host


y y

Pig  uncooked or not properly cooked pork can cause Trichinellasis & Taeniasis (T richine richinell a and T aenia aenia) asmodium Man- Pl asmodium Crustaceans  cause Paragonimiasis (Paragonimus westemani )

In Malaria: - Intermediate Host  Man (harbors younger forms: tropozoite, schizont, young gametocyte) - Definitive Host  Mosquito (transform gametocyte to micro/macro gametocyte)

Ex: T richomonas richomonas vaginal is is can be acquired from toilet seats

II. Indirect Life cycle At least one (1) intermediate host is needed or a vector is required in transmitting the parasite from one host to another Eg. F ascio asciol opsis opsis Pl asmodium asmodium In Trematode: st 1 inetermediate Host: Snail nd 2 Intermediate: ascio l a and  - if water plant- F ascio aciol opsis opsis F acio - if fish  liver fluke, intestinal fluke

I. Portal of exit - opening where the parasite leaves the host She used  Ascaris l umbricoides umbricoides l ife ife cycl e as an exampl e: e: portal  of exit is through anus (feces) II. Diagnostic stage- stage that would help you confirm the diagnosis Presence of eggs in the feces -when the feces is lodged in the soil, the fertilized and unfertilized egg can be found (take note that before the disease could be transmitted to another host, an embryonated egg is needed) - unfertilized egg - could be diagnostic but could not be infective; will just die in the soil - fertilized egg - means it is rapidly differentiating; it can be infective if it develops to third stage larvae while inside the embyonated egg


Ex: Pl asmodium asmodium fal ciparum ciparum y y y

(2) Trophozoite (Infective & Diagnostic) Diagnostic)


Infective stage: Sporozoite Diagnostic Stage: Trophozoite Schizont Gametocytes found inside the mosquito: Gametes Ookinete

 Ascaris lumbricoides Life Cycle of  Ascaris

serves to transfer them to new hosts like in mosquitoes. Types of Parasites

According to Taxonomic Group 1. Protozoans 1.1. Phylum sarcomastigophora   reproduction: binary fission 1.1.1. Subphylum Mastigophora - moves by flagella Eg: Giardia, T rypanosoma, rypanosoma, Leishmania, richomonas T richomonas Please refer to Table 1 for ( Please characterization)

1.3. Phylum Microspora (according to Dr. Dalay, this phylum is not very important medically)  classified under the Fungi kingdom by recent studies using DNA techniques ( raSites2006/Microsporidiosis/ ml) -no locomotory organ; characterized by a polar tube or polar filament found in the spore used to infiltrate host cells -obligate, spore-forming, intracellular parasites; with alternating sexual and asexual reproduction ex: Microsporidia

y y

y y



products produce the episodic chills and fever that characterize the disease) some merozoites form into male/female gametocytes Sporogonic cycle occurs in the mosquito (@the mosquito serves as the definitive host) the mosquito takes a blood meal and ingests the gametocytes in the mosquitos midgut, the gametocytes develop into gametes and fertilize each other (flagellated microgametes fertilize the macrogametocyte), forming motile zygotes called ookinetes the ookinete penetrates the gut epithelial cells and develops into an oocyst the oocyst undergoes multiple rounds of asexual reproduction, forming

through the feces, or (b) a thin-walled oocyst, which would autoinfect the host 1.4. Phylum Ciliophora -locomotory organ = cilia -mostly includes a variety of free -living and symbiotic species -reproduce asexually by transverse binary fission ex. Bal antidium antidium co l  Please refer to Table 3 for characterization) ( Please 2. Helminths  worm  like like organism organism  multi cellular, metazoan (eukaryotic (eukaryotic organisms of kingdom animalia) (Please refer to Table 4 for classification summary)

Table 6 summarizes Nematodes of Medical Importance

Comparison of nematode eggs. Enterobius is

D-shaped; T richuris richuris is bipolar

2.2. Phylum Platyhelminthes (flatworms) 2.2.1. Class Trematoda -flattened, leaf -shaped or cylindrical worms (Schistosoma), unsegmented; hermaphroditic l ocanum ocanum example of a *Echinostoma i l 

Red - Redia (in snail) Certainly - Cercaria

(free-living in water/snail)

Met - Metacercaria (in 2nd intermediate host)

Approval  Adult Generalized schistosomal life cycle (blood


Life cycle of a typical Fluke VS (unlike Schistosoma, most trematodes are hermaphrotidic and infect through metacercaria ingestion)

Trematode Eggs

 Class Cestoda - leaf shape, ribbon-like,

elongated, flattened

- sex: hermaphrodite or monoecious

Order Anoplura : human lice

Phylum Arthropoda


Hemiptera: reduvild bug

 4 morphologic Characteristics


Diptera : housefly


Hymenoptera : ants, bees, wasps


Siphonaptera : fleas


Diptera: mosquites, flies

- segmented body parts: head, thorax and

abdomen -

3 to 4 pairs of jointed appendages covered by hard chitinous exoskeleton

Class Chilopoda

(eg. Centipedes)

bilaterally symmetrical body

 Medical significance of Arthropods to Man

Importance of studying Medical Parasitology  To know the different parasites affecting

As direct agents of disease:


Pl asmodium asmodium Useful

4. Snail Transmission -

parasitic infective stage develops in snail

sites: 372/images.html

intermediate host or second intermediate host after partial development in the snail e.g) Schistosoma spp .

And please download the powerpoint Ms. Christel Pao has posted on FB for the photos. We try to make every tranx earth friendly. 

5. Food/animal Transmission (food -born and animal born) -

infective stage of parasite develops in an animal whose flesh is an important item for man e.g) T aenia aenia so l ium ium

No testing has undertaken you that is not common to everyone. God is faithful, and He will not let you be tested beyond your streng th but with the testing He will also provide the way out so that you may be able to endure it. 1 Cor 10

1.1. Table 1. Characterization of representative species of Phylum Sarcomastigophora Subphylum Mastigophora Giardia l amb ambl ia ia

Disease caused

Mode of 

transmission Infective stage


Ingestion of  cysts from contaminated water and food Cysts

T rypanosoma rypanosoma cruzi 

Chagas disease; American trypanosomiasis

Bites of reduviid bug (T riatoma riatoma)

Metacyclic trypomastigote Epimastigote --this is accdg to docs ppt, but accdg to the figure below (which is also found in docs ppt), it should be the trypomastigote Skin, mucous membrane, blood Chagoma; Romana sign; megacolon; cardiomyopathy (most serious Cx)

T rypanosoma rypanosoma brucei 

Subphylum Sarcodina richomonas T richomonas vaginal is is

Entamoeba histol ytica ytica

Naegl eria eria fow l l eri  eri 

African trypanosomiasis; sleeping sickness


Amoebic dysentery/ colitis

Acute Amoebic Meningoencephalitis in Normal Hosts

Bites of infected tsetse fly (Gl ossina) ossina)

Direct sexual contact (T richomonas richomonas = only flagellate affecting the genitals)

ingestion of cysts from contaminated food or water

Penetration of the nasal mucosa to the brain

Metacyclic trypomastigote




Epimastigote --this is accdg to docs ppt, but accdg to the figure below (which is also found in docs ppt), it should be the trypomastigote


Body fluids; blood

Vagina and prostate


Somnolence; seizure; coma

Vaginal/ prostatic discharge and itchiness

anchovy sauce; flaskshaped ulcer

Clinical presentations like fatal meningitis (rapid onset)

Diagnostic stage

Cysts and trophozoites


Small intestine


Steatorheic diarrhea; dysentery

Diagnosis through

Fecalysis and enterotest (string test)

Blood smear; body fluids

Blood smear; body fluids; NNN media

Wet smear of  vaginal discharge


Trophozoites in CSF/ Brain tissue



Benznidazole or nifurtimox

Pentamidine isethionate and sudamin



Amphotericin B


cysts and trophozoites



Table 2. Characterization of representative species of Phylum Apicomplexa.

Disease caused

Mode of transmission

Infective stage Diagnostic stage Habitat Fx Diagnosis through Treatment

Pl asmodium asmodium spp.

C ryptosporidium ryptosporidium spp.


Malabsorption syndrome; cryptosporidiosis *note the spelling 


fever Bites of infected female anopheline mosquito Sporozoites Blood stages Blood Tertian and quartan periodicity Blood smear Chloroquine, quinine, quinghaosu

Drinking/contact with contaminated water Small, sporulated oocyst with 4 sporozoites Small intestine Cachexia and severe diarrhea

Fecalysis Nitazoxanide; fluid and electrolyte replacement

Table 3. Characterization of Bal antidium antidium col i, i, representative species of P. Ciliophora antidium col i  i  Bal antidium Balantidiasis (common among slaughter house Disease caused workers) Ingestion of contaminated water/food Mode of transmission Infective stage Cyst Diagnostic stage Cyst & Trophozoite Habitat Large intestine Fx Diarrhea Diagnosis through Fecalysis Treatment Tetracycline with metronidazole

Table 4. Classification of Helminths Sub kingdom Phylum


Genus  e xamples


Aschelminthes Round worms; possess a peculiar type of  body cavity called a pseudocoel


Ascaris (roundworm) Trichuris (whipworm) Ancylostoma (hookworm) Necator (hookworm) Enterobius (pinworm or threadworm) Strongyloides

Platyhelminthes Flat worms; dorsoventrally flattened, no body cavity and, if present, the alimentary canal is blind ending


Round worms; appear round in cross section, they have body cavities, a straight alimentary canal and an anus

Taenia (tapeworm)

Adult tapeworms are found in the intestine of their host They have a head (scolex) with sucking organs, a segmented body but no alimentary canal Each body segment is hermaphrodite

Trematodes Non-segmented, usually leaf -shaped, with two suckers but no distinct head They have an alimentary canal and are usually hermaphrodite and leaf shaped Schistosomes are the exception. They are thread-like, and have separate sexes

Table 5. Summary of the distinctive features of worms Cestodes (tapeworms) Trematodes (flukes) Shape Segmented plane Unsegmented plane Body cavity No No Body covering Tegument Tegument Sex Hermaphroditic Hermaphroditic, except schistosomes which are dioecious Attachment organs Sucker or bothridia, and Oral sucker and ventral sucker or rostellum with hooks acetabulum Example diseases Tape Tapewo worm rm infec infecti tion on Schi Schist stos osom omia iasi sis, s, swimm swimmer' er'ss itch itch in humans

Fasciolopsis (liver fluke) Schistosoma (not leaf shaped!)

Nematodes (roundworms)


Present Cuticle

Dioecious Lips, teeth, filariform extremities, and dentary plates Ascari Ascarias asis is,, drac dracun uncu culia liasi sis, s, eleph elephan anti tias asis is,, ente entero robi bias asis is (pin (pinwo worm rm), ), filariasis, hookworm, onchocerciasis, trichinosis, trichuriasis (whipworm)

Table 6. Nematodes of medical importance. Habitat Genera l ostoma, ll aria Small intestine  Ascaris,  Ancy l  ostoma, Necator, T richine richinell a, a, C api  api ll  aria Large intestine T richiuris, richiuris, Enterobius Skin/Tissue Onchocerca, Loa, Gnathostoma, T richine richinell a Blood and Lymphatic system W ucheria, ucheria, Brugia l us  Angiostrongy l  us CNS   stoma sp. (hookworm), representative species of Class Nematoda and W uchereria Table 7. Characterization of  Ancy l lostoma o uchereria bancrofti , a parasitic filarial nematode. l ostoma  Ancy l  W uchereria ostoma uchereria bancrofti  Disease caused Ancylostomiasis, Necatoriasis Lymphatic filariasis Skin penetration of filariform larvae bites of infected mosquitoes Mode of transmission Infective stage Filariform larvae Third stage larvae (L3) Diagnostic stage Ova Microfilariae Habitat Small intestine Lymphatic system; skin and glands Fx Elephantiasis Ground itch, iron deficiency anemia Diagnosis through Fecalysis Blood smear Treatment Mebendazole Mebendazole

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