s4 l1 Introduction to Parasitology

Nina Ian John “G” Rachel Mark Jocelle Edo Gienah Jho Kath Aynz Je Glad Nickie Ricobear Teacher Dadang Niňa Arlene Vivs Paul F. Rico F.Ren Mai Revs Mavis Jepay Yana Mayi Serge Hung Tope Ag Bien

S4 L1: INTRODUCTION TO PARASITOLOGY by Dra. Ma. Cielo Malijan MD, DPPS, FPSDBP

Ectoparasite: a parasite living outside the body of the host; presence inside the host is called an infestation

DEFINTION OF TERMS Parasitology - Area of biology concerned with the phenomenon of dependence of one living organism on another Medical Parasitology - Concerned primarily with the animal parasites of humans and their medical significance, as well as their importance in human communities Biological Relationship: 1. Symbiosis - Is the living together of unlike organisms; may also involve protection or other advantages to one or both partners Different forms of symbiosis: distinguished on whether or not the association is detrimental to one of the 2 partners - Commensalism - Mutualism - Parasitism 2. Commensalism - Is a symbiotic relationship in which 2 species live together and one species benefits from the relationship without harming or benefiting the other Ex. Entamoeba coli in the intestinal lumen is supplied with nourishment and is protected from harm, while it does not cause any damage to the tissues of its hosts. 3. Mutualism - Is a symbiosis in which 2 organisms mutually benefit from each other Ex. termites and the flagellates in their digestive system, which synthesize cellulose to aid in the breakdown of ingested wood 4. Parasitism - A symbiotic relationship where one organism, the parasite, lives in or another (the host), depending on the latter for its survival and usually at the expense of the host Ex. Entamoeba histolytica derives nutrition from the human host and causes amoebic dysentery Parasites - described according to their habitat or mode of development Types of Parasite: A. According to habitat Endoparasite: a parasite living inside the body of a host; presence in a host is called an infection

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Erratic: found in an organ which is not its usual habitat B. Other types: Obligate: need a host at some stage of their life cycle to complete their development and to propagate their species o Ex. tapeworms depend entirely upon their host for existence Facultative: may exist in a free-living state or may become parasitic when the need arises Accidental or incidental: establishes itself in a host where it does not ordinarily live Permanent: remains on or in the body of the host for its entire life cycle Temporary: lives on the host only for a short period Spurious: a free-living organism that passes through the digestive tract without infecting the host Host 

classified based on their life role in the life cycle of the parasite; the organism that harbors the parasite.

Types of Host:

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Definitive or final: one in which the parasite attains sexual maturity o Ex. Humans are the definitive host in taeniasis Intermediate: harbors the asexual or larval stage of the parasite o Pigs or cattles as intermediate hosts of Taenia spp. while snails are hosts of Schistosoma spp. Paratenic: parasite does not develop further to later stages. However, the parasite remains alive and is able to infect another susceptible host o Paragonimus metacercariae in raw wild boar meat can pass through the intestinal wall of humans and complete its development Reservoir: allow the parasite’s life cycle to continue and become additional sources of human infection o Pigs are reservoir of Balantidium coli o Cats of Brugia malayi

Humans are not always the final host. Man may be the most important host in the spread of the disease or an incidental host of parasites prevalent in other animals.

Vectors  responsible for transmitting the parasite from one host to another

Types of Vectors: Biologic: transmits the parasite only after the latter has completed its development within the host o Aedes sucks blood from a patient with filariasis; the parasite undergoes several stages of development from the first stage larva to 3rd stage larva before it is transmitted to another susceptible host  Mechanical or phoretic: transports the parasite o Flies and cockroaches that feed on fecal material may carry enteric organisms and transfer these on food Exposure and Infection Carrier: harbors a pathogen without manifesting any S/Sx Exposure: process of inoculating an infective agent Infection: connotes the establishment of the infecting agent in the host Incubation period (clinical incubation period): period between infection and evidence of symptoms Pre-patent period (biologic incubation period): period between infection or acquisition of the parasite and evidence or demonstration of infection Autoinfection: when an infected individual becomes his own direct source of infection Autoinfection – self is the source of infection o seen in the life cycle of E. vermicularis, Hymenolepsis nana and Strongyloides stercoralis o Ex. Enterobiasis:infective eggs end up in the hands by scratching the perianal areas where the gravid females lay their eggs Superinfection or Hyperinfection: when the already infected individual is further infected with the same species leading to massive infection o alteration in the normal life cycle of Strongyloides results in a large increase in worm burden  sever debilitation/death Sources of Infection  Contaminated soil and water: most common  Lack of sanitary toilet cause infection with Ascaris, hookworm  Water contaminated with cysts of amoebae or flagellates as well as cercaria of Schistosoma  Food: may contain the infective stage of the parasite  Arthropods: e.g. mosquitoes as vectors of malaria and filarial parasite  Other animals (wild or domesticated) may harbor the parasite e.g cats are direct sources of Toxoplasma infection  Other sources. Another person, his bedding and clothing, the immediate environment e.g asymptomatic carriers of Entamoeba histolytica working as food handlers Modes of Transmission  Mouth is the most likely portal of entry; o Most cestopods, trematodes and protozoans are food borne  Skin penetration: e.g hookworms and Strongyloides

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Arthropods: vectors transmit parasites through bites o Agents of malaria, filarial, leishmania and trypanosomiasis Congenital transmission: Toxoplasma gondii trophozoites can cross the placenta Other ways o Inhalation of airborne eggs of Enterobius o Sexual intercourse as in the case of Trichomonasvaginalis

Nomenclature  Based on International Code of Zoological Nomenclature  Each phylum is subdivided into classes which are further subdivided into orders, families, genera and species o Further subdivisions of suborder, superfamily and subspecies are employed at times  Family names are formed by adding -ridaeto the stem of genus type  Names of the genera and species are italicized or underlined when written Life Cycle  May be simple or complicated  As the life cycle becomes more complicated, the lesser the chances are for the individual parasite to survive  Perpetuation of a species of parasite depends upon its ability to ensure transmission from one host to the next Epidemiologic measures  Cumulative prevalence: percentage of individuals in a population infected with at least one parasite  Intensity of infection o Number of worms per infected person o Also referred to as worm burden o Measured directly by counting expelled worms during treatment; indirectly by counting helminthes eggs excreted in feces expressed as eggs per anum (epg)  Morbidity: clinical consequences of infections that affect on individual’s well being Diagnosis  Demonstration of parasites (eggs, adults, larvae, cysts and triohozoites)  Detection of host immune response to the parasites o In light infections when parasites are still immature, immunoassays may become useful  Specimens for parasitic examination: stool, blood, urine, sputum, cerebrospinal fluid, tissue aspirate, tissue biopsies and orifice swabs  Microscopy: simple, informative; can establish rapid diagnosis; dependent on skill of microscopist (may ganito palang profession! Hahaha! I think microbiologist ito. ) o Limited by low density of parasites in specimens; may be affected by stage of the disease, biology of the parasite o Parasite concentration techniques require additional equipment, supplies and reagents Page 2 of 5

Parasite culture methods: require a clean bench and special culture media o Special staining procedures of fluorescent microscopy available for better visualization Molecular diagnosis: molecular or DNA-based methods o Address problems associated with microscopy and immunodiagnosis o DNA probes, detection of specific nucleic acid consequences Rapid diagnostic tests (RDTs) o Newer and more advances methods of immunodiagnosis o Easy to perform, faster results o

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Immunodiagnosis  Overcome problems related to microscopic examination  Detect antigen or antibodies in clinical specimens (Immunofluorescence Assay, ELISA, Indirect Hemagglutination Assay, RIA and dot blot)  Antibody detection tests o Useful in detecting exposure and etiology of outbreaks and in mapping foci of infection o Serve as alternatives when microscopic exam fails Cure rate:  Number (expressed as percentage) of previously positive subjects found to be egg-negative on examination of a stool or urine at a set time after deworming  Indicator used to measure reduction in prevalence of infection Egg reduction rate (ERR):  Percentage fall in egg counts after deworming  Indicator used to measure reduction in intensity of infection

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Includes safe disposal and hygienic management of human and animal excreta, refuse and waste water Involves the control of vectors, intermediate hosts and reservoirs of disease Provision of safe drinking water and food safety

Eradication versus Elimination Disease eradication: permanent reduction to zero of the worldwide incidence of infection caused by a specific agent, as a result of deliberate efforts  Continued measured no longer needed Disease elimination: reduction to zero of the incidence of a specific disease in a defined geographic area as a result of deliberate efforts  Continued intervention/surveillance still required Mechanisms by which parasites cause injury to the host 

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interference with the vital processes of the host through the enzyme systems- Most common o Secretory and excretory products of parasites allow them to metabolize nutrients from the host o Ex. E. histolytica trophozoites secrete cysteine proteinases digest cellular material and degrade epithelial basement membrane facilitating tissue invasion Invasion and destruction of host tissue o Ex. Plasmodium invades RBC and cause its rupture Deprivation of the host of essential nutrients and substances o Ex. heavy hookworm infestation causes Iron Deficiency Anemia (IDA)

Effects of the host on the Parasite Treatment  Selective: involves individual-level deworming with selection for treatment based on a diagnosis of infection Targeted: group-level deworming where the (risk) group to be treated (w/o prior diagnosis) may be defined by age, sex or social characteristics irrespective of infection status Universal: population-level deworming in which the community is treated irrespective of age, sex, infection status or other social characteristics Prevention and Control Aim: prevent or minimize vector or intermediate host propagation and reduce contact between humans and the infective agent Morbidity control: the avoidance of illness caused by infections Infection-education-communication (IEC): a health education strategy that aims to encourage people to adopt and maintain healthy life practices Environmental management: manipulation of environmental factors or their interaction with human beings Environmental sanitation: interventions to reduce environmental health risks

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Genetic make-up of the host o Influence the interaction with the parasite o Sickle-cell trait confers some protection from Falciparum malaria Nutritional status of the host o High protein diet not suitable for the development of intestinal protozoan Immune processes o Acquired immunity important in modifying severity of disease in endemic areas

Immunology of Parasitic Infection Host-Parasite Interactions Non-specific defenses:  Intact skin: hookworms synthesize a protein that aids in the penetration process  Acidic pH of vaginal secretion and gastric juice: T. vaginalis trophozoites unable to survive the acidic environment of the vagina Mucus secretions Page 3 of 5

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Envelope parasites (G. lamblia) affecting its mobility and reducing pathology on the host

Chemical components of body fluids  Lipase content of breastmilk: toxic to G.lamblia in vitro Immunology of Parasitic Infection Host’s cellular components on the skin and mucosal system of the GIT serve as protective mechanism for the host  Langerhans cells, dendritic cells, mast cells and re-circulating T lymphocytes on the skin (SALT)  Gut associated lymphoid tissues (GALT) Mounting of acquired specific responses against parasite antigen  Response: recognize self from non-self  Destroys the parasite Host immune response to parasitic infection  Well-defined genetic control  Parasite antigens are processed and presented to T helper lymphocytes (TH1 or TH2)  produce lymphokines bring out CMI response or antibody production  Antibodies involved: IgE, IgG, IgM and IgA  Most common response: eosinophilia and elevated serum IgE o Ex/ marked immunologic response in Angiostrongylus contonensis and T. canis o Bound IgE antibodies mediate expulsion of adult GI helminthes

Groups of parasites with medical and public health importance Parasitic infections Unicellular protozoan Multicellular metazoan Kingdom Protista Sarcomastigophora Ciliophora Apicomplexa Microspora Metazoan parasites Arthropods Helminthes o Annelids (leeches) o Nematodes o Flatworms  Cestodes  trematodes Protozoa All protozoa fall under K. Protista Structure present: Nucleus/nuclei, cytoplasm, outer limiting membrane, cellular elaborations (organelles), locomotory apparatus (cilia, flagella, pseudopodia) May require a wet environment for feeding, locomotion, osmoregulation and reproduction Form infective stages called cysts which are resistant to environmental changes compared to the vegetative stages called trophozoites

Parasite Evasion mechanisms 

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Immune suppression Reduce immune function of macrophages leading to defective antigen processing in Plasmodium infection Antigenic variation Surface protein variation seen in T. gambiense and G. lamblia infection Host mimicry Tegument of Schistosoma spp. adult can acquire antigenic molecules from the host Intracellular sequestration Trypanosoma and Leishmania proliferation in macrophages and escape the host immune response

Phylum P. Sarcomastigophora Subphylum Mastigophora Subphylum Sarcodina P. Ciliophora P. Apicomplexa

P. Microspora

Pseudopodia (foot-like extrusions) Cilia (hair-like projections) Apical complex at the anterior end consisting of polar rings, subpellicular tubules, conoid, micronemes Extrusion apparatus to insert infective material to the host cell

Classification of Protozoan parasites: Phylum Subphylum Sarcomastigophora

Mastigophora

Adverse effects of immune response to the host Intense or abnormal immune responses may result in pathological manifestations T. cruzi– massive damage not only to infected cells but also to surrounding nerve cells and myofibers Recurrent Plasmodium infection, immune complexes are associated with Hyperactive Malarious Splenomegaly (HMS) – patients suffer from persistent splenomegaly and anemia In P.malariae infection, these immune complexes are deposited in glomerular basement membrane  kidney failure and nephritic syndrome

Organelle of locomotion Flagella (whip-like structures)

Sarcodina Ciliophora Apicomplexa

Microspora

Species Chilomastix mesnili, Dientamoeba fragilis, Giardia lamblia, Trichomonas hominis, T.lenax, T.vaginalis, Leishmania braziliensis, L.donovani, L.tropica, Trypanosoma brucei complex, T.cruzi Acanthamoeba castellani, Endolimaz nana, Entamoeba coli, E. histolytica, Iodamoeba Balantidium coli Babesia spp., Cryptosporidium hominis, Isospora, Cyclospora catenensis, Plasmodium spp, Toxoplasma gondii Vittaforma cornea, Pleistophora spp., B. vesicularum

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Nematoda Intestinal Extra-intestinal

Ascaris, Capillaria, Enterobius, Hookworm, Strongyloides, Trichuris Angiostrongylus, filaria, Trichinella

Cestoidea Cyclophyllidea

Diphyllidium, Echinococcus, Hymenolepis, Taenia

Pseudophyllidea

Diphyllobpthrium,

Intermediate hosts (IH)

Trematoda Arthropods Arachnida

Mites, scorpions, spiders, ticks

Chilopida

Centipedes

Crustacea

Copepods, crabs

Diplopoda

Millipedes

Insecta

Flies, fleas, beetle, lice, wasp, bugs, mosquitoes

Pentastomida

Tongue worms

Nematodes Elongated, cylindrical with bilateral symmetry and a complex digestive tract Provided with separate sexes; some may be parthenogenetic With sensory organs in the anterior (amphids) and posterior ends (phasmids) o Those with phasmids are called phasmids nematodes o Those phasmids are aphasmids nematodes 3 phasmids worms of medical importance: Trichuris, Trichinella and Capillaria Cestodes: tapeworms Platyhelminths Dorsoventrally flattened with bilateral symmetry Segmented, ribbon-like appearance Adult tapeworms are hermaphroditic o Provided with a scolex (main attachement to the host) neck region, from it will start segmentation or strobilization o Infection with adult tapeworms is through the consumption of infected intermediate hosts; Some are infected with the larval stage of T. solium called cystecercosis and of Echinococcus spp. called hydatid cyst 2 orders with medical importance: Pseudophyllides and Cyclophyllidea Criteria Scolex Genital pores

Recovery of both eggs and

Pseudophyllidean tapeworms Spatulate scolex with sucking grooves called bothria Present but has uterine pore which allows release of eggs from gravid uterus

Segments are generally found

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Cyclophyllidea tapeworms Globular with muscular suckers

segments Eggs

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Present but without uterine pore instead undergo the process of apolysis whereby gravid segments are detached from the main body and eggs are eventually released Both eggs and segments are recovered

Operculated and immature; requires aquatic development of the embryos called coracidium Requires 2 IH: in the 1st IH eggs encyst as procercoid, in the 2nd IH as pleocercoid larvae This is best represented by Diphyllobothrium which causes adult infection and Spirometra which causes larval infection in man

from patients Eggs are nonoperculated and are passed out readily containing the hexacanth embryo Only 1 IH but different species produce diff types of encysted larvae in the IH Ex. Taenia produce cysticercus type Hymenolepsis, Diphyllidium and Raillientina produce the cysticercoids type

Trematodes or Flukes Leaf-Like and unsegmented Adults have an oral sucker and a ventral sucker called acetabulum All are hermaphroditic; require two intermediate hosts While the first IH is always as snail the second IH vary from fish to crustacean to another snail or to fresh water plants Generally, grouped based on their habitat o Adult Schistosomes are found in the mesenteric veinsblood flukes o Adult Paragominus found in the lung parenchyma o Flukes that inhabit the liver and bile passages: Fascioloa, Clonorchis and Opisthorchis o Flukes that inhabit the intestines: Fasciolopsis, Echinostoma and Heterophids Arthropods Bilaterally symmetrical organisms with segmented jointed appendages Chitinous exoskeleton covers the body Includes insects, mites, ticks, spiders, scorpions, centripedes, millipedes and crustacean -------------------------------------END OF TRANS-------------------------------------Fun Facts about the human body:  The average duration of a single blink of the human eye is 0.3 seconds.  "Mageiricophobia" is the intense fear of having to cook (hmmm.. may kilala ba kayong ganito? Hahaha )  A 3-week-old embryo is no larger than a sesame seed. A 1-month-old fetus’s body is no heavier than an envelope and a sheet of paper. Its hand is no larger than a teardrop.  There are more than 100 different viruses that cause the common cold (kung magaling ka, pangalanan mo nga sila lahat!)  There are ten human body parts that are only three letters long: eye, hip, arm, leg, ear, toe, jaw, rib, lip, and gum (amazing!)  The average human heart beats about 100,000 times every 24 hours. In a 72-year lifetime, the heart beats more than 2.5 billion times. (mas mabilis pag umiibig! hahaha!)

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