Introduction to Parasitology. MDCN247 Virology and Parasitology

Transcription

1 Introduction to Parasitology MDCN247 Virology and Parasitology

2 Introduction to parasitology(3h) At the end of this introduction the student should be able to Defines parasite, host, vector, zoonozis Defines types of organism relatıonships Lists the classification of parasitic infections Defines cell structure of protozoon and helminths Defines the life cycles of parasites Modes of infection

3 Medical microbiology the study of the interactions between animals (primarily humans): With microorganisms Bacteria Viruses Fungi Parasites Prions

4 Medical microbiology the study of the interactions between animals (primarily humans): With microorganisms Bacteria Viruses Fungi Parasites Prions

5 Cell Eukartotes: -membrane bound nucleus -relatively large size -presence of membrane bound organelles (such as mitochondria) Prokaryotes: DNA is not physically separated from the cytoplasm

6 Eukaryotes and prokaryotes: Are organisms -with all the enzymes required for their replication and -biologic equipment necessary for the production of metabolic energy They are different from viruses which depend on host cells for these functions

7 Typical eucaryotic cell

8 The three phylogenetic lineages of cells (Domains according to comparative rrna sequences) Bacteria Archae Eukarya

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10 Medical Microbiology primary interest : diseases caused by these interactions Microorganisms play a critical role in human survival. The normal commensal population of microbes participates in the metabolism of food products provides essential growth factors protects against infections with highly virulent microorganisms stimulates the immune response In the absence of these organisms, life as we know it would be impossible

11 Commensal and Pathogenic Microbial Flora in Humans The microbial flora Microbiom in and on the human body: continual state of flux determined by a variety of factors! Age Diet Hormonal state Health personal hygiene

12 Commensal and Pathogenic Microbial Flora in Humans Human fetus lives in a protected, sterile environment Newborn human is exposed to microbes from the mother and the environment. The infant s skin is colonized first, followed by the oropharynx gastrointestinal tract and other mucosal surfaces. Throughout the life of a human being, this microbial population continues to change

13 Commensal and Pathogenic Microbial Flora in Humans Changes in health can drastically disrupt the delicate balance that is maintained among the heterogeneous organisms coexisting within us: hospitalization can lead to the replacement of normally avirulent organisms in the oropharynx with resistant gram-negative rods (e.g., Klebsiella, Pseudomonas) that can invade the lungs and cause pneumonia. the indigenous bacteria present in the intestines restrict the growth of Clostridium difficile in the gastrointestinal tract. In the presence of antibiotics, however, this indigenous flora is eliminated, and C. difficile is able to proliferate and produce diarrheal disease and colitis.

14 Exposure of an individual to an organism lead to one of three outcomes: (1) transiently colonize the person (2) permanently colonize the person, or (3) produce disease. It is important to understand the distinction between colonization and disease. (Note: Many people use the term infection inappropriately as a synonym for both terms.)

15 Exposure of an individual to an organism Organisms that colonize humans (whether for a short period, such as hours or days [transient], or permanently) do not interfere with normal body functions. In contrast, disease occurs when the interaction between microbe and human leads to a pathologic process characterized by damage to the human host.

16 Exposure of an individual to an organism Disease occurs when the interaction between microbe and human leads to a pathologic process characterized by damage to the human host. This process can result from microbial factors (e.g., damage to organs caused by the proliferation of the microbe or the production of toxins or cytotoxic enzymes) or the host s immune response to the organism : the pathology of severe acute respiratory syndrome [SARS] coronavirus infections

17 A few infections are caused by strict pathogens: organisms always associated with human disease Mycobacterium tuberculosis (tuberculosis) Neisseria gonorrhoeae (gonorrhea) Francisella tularensis (tularemia) Plasmodium spp. (malaria) Rabies virus (rabies)

18 Opportunistic pathogens Most human infections are caused by them Members of the patient s normal microbial flora : Staphylococcus aureus, Escherichia coli, Candida albicans Do not produce disease in their normal setting but establish disease when they are introduced into unprotected sites (e.g., blood, tissues). If a patient s immune system is defective, that patient is more susceptible to disease caused by opportunistic pathogens!!!!!

19 The microbial population that colonizes the human body is numerous and diverse. Our knowledge of the composition of this population is currently based on comprehensive culture methods However, it is estimated that only a small proportion of the microbes can be cultivated.

20 Human Microbiome Project (HMP) To better understand the microbial population, a large scale project has been initiated to characterize comprehensively the human microbiota analyze its role in human health and disease

21 Human Microbiome Project (HMP) The skin and all mucosal surfaces of the human body are currently being analyzed systematically by genomic techniques. The initial phase of this study was completed in 2012, and it is apparent that the human microbiome is complex, composed of many organisms not previously recognized, and undergoes dynamic changes in disease.

22 TYPES OF ORGANISM RELATIONSHIPS Normal Flora. Normal flora consists of microorganisms that are normally and consistently found in or on the body in the absence of disease. Symbiosis. This is the close association or living together of two organisms of different species; each party involved in this relationship is called a symbiont. Mutualism. This is a type of symbiosis in which both organisms (host and parasite) benefit from the association.

23 TYPES OF ORGANISM RELATIONSHIPS Commensalism. This is also a type of symbiosis, but in this case, the parasite (commensal) is benefited and the host is neither benefited nor harmed by the relationship Parasitism. Parasitism is an obligatory relationship in which one organism, the parasite, is metabolically dependent on another organism, the host. The host may be harmed by such a relationship.

24 Parasitology

25 Introduction Parasitic Classification Structure Replication

26 Parasites interrelationships among parasitic organisms their epidemiology transmission of disease the specific disease processes involved the possibilities for prevention and control of maladies

27 Worldwide disease burden Malaria >500 million infected people, annual death 2-3 million Ascariasis 1.3 billion infected annual death

28 Case History An 18-year-old villager girl reported to the emergency department with a history of recurrent vomiting and abdominal pain of one day duration. The patient gave history of loss of appetite and nausea of the same duration put on NPO, I.V.-fluids On the next day, the nasogastric tube got blocked and was subsequently removed. On removal, the head end of a tapeworm which was retrieved through the nose:

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30 The patient got instant relief of her symptoms. Microbiological examination confirmed it to be a 6.3 meter long Taenia saginata strobila with immature, mature and gravid proglottids. The patient was given a single dose of praziquantel: 15 mg/kg body weight. Parasitological controls (two series of three fecal samples each), performed two months later, were negative for Taenia eggs.

31 Taenia saginata, the beef tape worm a parasite (cestode) of both cattle and humans, which can only reproduce in humans. T. saginata occurs where cattle is raised, human feces is improperly disposed off, meat inspection programs are poor, and where meat is eaten without proper cooking. Approximately 50 million people worldwide are infected by T saginata or T solium.

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33 Taenia genus Two species from the genus are common parasites of man: Taenia solium (the pork tapeworm) Taenia saginata (the beef tapeworm). Improperly disposed human feces, poor meat inspection programs, and eating of improperly cooked meat are well known risk factors for the transmission of the disease. Rarely, the worm may be present in the stomach leading to potentially infective oro-gastric secretions of these patients. Contamination with these secretions may lead to infection to the caregivers making it an unusual but important route of transmission of taeniasis, particularly in the highly endemic areas.

34 Some basic parasite terminology Ectoparasites: Ectoparasites are true parasites in that they depend on the host for habitat and nutrition but they live on and not in theirs hosts. While less invasive some ectoparasites can nonetheless cause serious disease. Endoparasites: These parasites live in the bodies and tissues of their hosts, some even live within the cells that make up their hosts. Malaria :the red bloods cells of the circulatory system Tape worm: lives in the intestine.

35 Some basic parasite terminology Infection: Infectious diseases are caused by transmissible organisms biological agents (in the case of viruses and prions). In its narrower definition infection implies that the biological agents multiplies within the host. In the case of malaria : -the mosquito injects parasites -within two weeks multiply into many millions. This multiplication is essential to the development of disease.

36 Infestation: Some parasites do not multiply within the host: This situation is referred to as infestation: This is true for most worms. A person who swallows three tape worm larvae will not develop more than three tape worms. The severity of disease in infestations therefore is often highly dependent of the infectious (or infestious) dose. Infection is often used more generally to describe both phenomena.

37 Obligate/facultative parasitism Obligate Parasitism: complete dependence of the parasite on the host The vast majority of parasites that cause human disease are obligate parasites Facultative parasites: Can switch between a parasitic and a free-living lifestyle. This is often triggered by ecological factors (e.g. the availability of hosts or nutrition)

38 Parasitology eukaryotic organisms: mainly protozoa helminths some arthropods annelids molluscs.

39 Medical parasitology 200 or so species of helminth worms about 80 species of protozoa that infect humans.

40 Ancient History The Ebers papyrus, written about 1600 BC, contains references to the presence of parasitic worms in man. The laws of the Mosaic code prohibiting the consumption of meat from unclean animals indicate that the early Israelites had knowledge about parasitic infections. There is also evidence of parasitic recognition among the Roman, Greek, Persian, and Phoenician scientists. Chinese doctors were aware of parasites as early as 300 BC.

41 Modern History The liver fluke Fasciola hepatica was discovered by Jehan de Brie in 1379 from sheep. Anton Van Leewenhoek ( ) described the morphology of the protozoan Giardia lamblia from his own stool. In 1880, Laveran demonstrated the intracellular parasites of malaria.

42 Misconceptions Many people believed that lice protected children from disease and leeches were used extensively for blood letting as a cure. For a time, intestinal parasites were thought to help incleaning the tract of excess food and waste Until recently, the Chinese believed that powdered Ascaris was helpful for medicinal treatment of impotency. In France, the heads of tapeworms(scolices) were once used as weight control measures.

43 Present Ideology Modern medicine: recognized the pathogenic effects of parasites searching for drugs useful in the treatment of parasitic infections Prevention is the best method to attack the problem of parasites.

44 Life cycles Definitive host: This is the host in which the parasite reproduces sexually. Intermediate host: One or several successive hosts in which the parasite might increase its number by asexual multiplication. Vector: Hosts that actively transmit the parasite to the next host as opposed to just being by that next host. Mosquito which injects malaria parasites with it salvia into humans during a blood meal.

45 Life cycles Transport (or paratenic) hosts: No parasite development or multiplication occurs The parasite just hitches a ride on the food chain: The larva of the fish tape worm can move in this way from smaller fish to bigger fish and yet bigger fish awaiting the definitive mammal host to eat a fish.

46 Life cycles Reservoir host: Some parasites can infect a variety of mammals in addition to humans. Biologically these hosts are equal to humans meaning that they occupy the same position in the life cycle and are not up or downstream. These hosts (often wild or domestic animals living İn proximity to humans) present a reservoir out of which humans can be re-infected even if the disease has been cleared from all humans in the area. The presence or absence of a reservoir is obviously a very important consideration for programs aimed at controlling or eradicating a disease. while a dead end for the parasite this can still cause disease. We will highlight some examples of such disease when we discuss human infection with cat and dog parasites.

47 Disease Terminology Prepatency: The phase of the disease between infection and the appearance of diagnosable parasite stages the appearance of tape worm eggs in the feces malaria parasites in a routine blood smear This time frame can change with improvements in the sensitivity of diagnostic assays A patent infection is thus at an established diagnosable stage.

48 Disease Terminology Incubation period: The incubation period is the time between infection and the development of symptoms (signs of disease like fever, pain or discomfort) Acute disease: With the onset of symptoms the infection enters its acute (lat. sharp) phase. Acute diseases have a relatively quick onset and short duration. The symptoms worsen into a crisis and then the disease resolves spontaneously into healing, results in the death of the patient, or transforms into chronic disease.

49 Chronic disease: Chronic diseases (gr. chronos, time) develop slowly (often over years) Persistent might show no symptoms once chronic or worsen over time. In chronic infections the parasite survives or persists over time (this time can be the rest of the life of the patient).

50 Convalescence: period after healing Describes a phase in which balance is regained and damage repaired. This phase is characterized by the absence of infectious agents and symptoms, and in certain cases goes along with the development of long-term immunity to reinfection.

51 A typical parasite life cycle diagram The fish tape worm Parasite stages are shown in the outer circle and hosts in the center The worm reproduces sexually in mammals (definitive host). A motile larva hatches and infects the first intermediate host a waterflea and transforms and grows. The waterflea is eaten by a fish again the parasite transforms and now lives in the musculature of the fish. Note that there is no further development of the parasite from trout to pike. The pike is a transport host.

52 PARASITIC ATTRIBUTES THAT INFLUENCE DISEASE Virulence. Virulence refers to the ability of a parasite to establish itself in a host, maintain that infection, and damage the body of the host. For one reason or another, one strain of a parasite may cause a more serious disease process than other strains of the same species. Parasitosis. The more parasites infecting a host, the more severe will be the effect on that host. Life Span of the Parasite. The longer the parasite lives in or on the host, the greater the damage that will be caused.

53 Repeated Contact. The more times that a host is parasitized by an organism, all other factors being equal, the worse the prognosis of the disease. Competition for Food. Intestinal parasites deprive the host of the necessary nutrients required for survival. Mechanical Interference. Some parasites accumulate (like in the intestines) in such great numbers that the normal flow of nutrients, waste, or fluid is obstructed. For example, the microfilariae of some nematodes obstruct the lymphatic system in elephantiasis. Their presence prevents lymphatic fluid from being circulated out of lymphatic tissue and the swelling associated with elephantiasis results.

54 Toxic Effects. By-products of metabolism and anatomic parts of the parasite can be very toxic to the host. In cases of massive infections with Trichinella spiralis, it is this toxicity that is lethal to the host. Tumor. Tumor formation in the host is a common occurrence with parasites that invade or irritate the tissue of the host. Pathologists have suggested that repeated infections with Trichomonas vaginalis could lead to cervical cancer? recently, some cases of malignant neoplasms have been reported from Egypt and attributed to Schistosoma infections. Some benign tumors are caused by the larval stage of the tapeworm Taenia solium in muscle tissue.

55 Loss of Blood and Body Fluids. The loss of blood and body fluids caused by parasites is significant. For example, it has been calculated that about 0.5 ml of blood per worm per day is lost by the host during a hookworm infection. These fluids contain nutrients and electrolytes needed by the host. Destruction of Host Tissue. Parasites destroy the host's tissue structures by the presence and activity of the adults, by the migration of larval forms, and by ovipository migrations. Psychological Disorders. The knowledge of parasites crawling inside the body can affect anxiety level of the host. But, the more detrimental psychological effects are those caused by the accumulation of chemicals in the system of the host.

56 HOST ATTRIBUTES THAT INFLUENCE RESISTANCE TO PATHOGENIC EFFECTS OF PARASITISM Fitness of the Host. The nutritional and emotional state of the host can effect the degree of pathogenicity caused by the parasite. Host Age. Both the very young and the very old are affected to a Greater degree by a parasitic infection than are young adults.

57 HOST ATTRIBUTES THAT INFLUENCE RESISTANCE TO PATHOGENIC EFFECTS OF PARASITISM Specific Factors That Influence Resistance. Immunity. Host resistance to parasitic infection is very similar to the resistance shown against bacteria. The immune system works by the formation of antibodies against a limitless amount of substances recognized as foreign antigens by the B lymphocytes.

58 Complement system. This is a complex system of enzymes found in normal serum that aids the lysis (destruction) of the parasite during an antigen-antibody reaction. Complement is composed of nine components labeled C-1 through C-9. Interferon. Interferon is composed of a group of soluble small proteins produced by infected cells that inhibit multiplication of virus. The proteins are not virus specific, but they are cell specific in production and effects.

59 Nonspecific Factors That Influence Resistance. There are some Barriers that affect parasitism. These barriers may be chemical, physical,or biological (the antagonistic effect of organisms already present at the site in question).

60 Barriers (1) Chemical barriers. The host combats the invasion of micro-organisms by the secretion of chemicals that are antimicrobial in nature: The acid ph of the stomachskin, and vagina; the bile salts of the intestines; and the lysozymes of the eyes and saliva serve as deterents to the invasion of microorganisms.

61 Barriers (2) Physical barriers. The intact skin, mucus (sticky lining of the mucous membranes) nasal hairs, cilia of the respiratory epithelium, Peristaltic movement, and normal microbial flora (occupying attachment sites) prevent the entrance of microorganisms.

62 Barriers (3) Microbial antagonism. Antiparasitic factors present in the serum competition for nutrients from the normal flora also serve as obstacles for the possible pathogenic parasites.

63 TAXONOMY OF PARASITES INFECTING HUMANS All living organisms have been divided into groups with similar characteristics. These groups have been subdivided further until organisms that have identical traits are classified under the same genus and species. It is important that you be familiar with the principles of taxonomy pertaining to parasites.

64 TAXONOMY OF PARASITES INFECTING HUMANS DIVISIONS OF LIVING ORGANISMS a. Kingdom. This is a large group of organisms with similar features. In the literature, various authors list from two to five kingdoms. (1) Kingdom PLANTA. This kingdom contains all of the plants. There are no plants parasitic to man. (2) Kingdom PROTISTA. Members of this kingdom are unicellular (onecelled) organisms. The kingdom is further divided into two subkingdoms. (a) Subkingdom EUCARYOTA. Eucaryotes are characterized by a nuclear membrane separating the nucleus from the cytoplasm, DNA that is grouped into units called chromosomes, multiplication accomplished by mitosis, and energy produced in structures called mitochondria. Some examples are protozoans and fungi.

65 (b) Subkingdom PROCARYOTA. The procaryotes are characterized by no nuclear membrane (therefore, there is no organized nucleus); no chromosomes (the DNA is not separated but is a continuous strand); no mitosis (multiplication is accomplished by simple cell division); and no mitochondria (energy is produced at The mesosomes). Some examples are bacteria and bluegreen algae. (3) Kingdom ANIMALIA. The higher animals, including man, are placed in this kingdom. There are many parasites that infect man in this kingdom.

66 Phylum. A phylum is a major division of a kingdom. There are four phyla (plural of phylum) that contain human parasites: PROTOZOA from the subkingdom EUCARYOTA, and phyla PLATYHELMINTHES, ASCHELMINTHES, and ACANTHOCEPHAHELMINTHES from the kingdom ANIMALIA. c. Class. A phylum is divided into classes. The name of the class should end in "a." Some examples are Cestoda and Nematoda. d. Order. Several orders may be contained within a class. This name ends in "ea." Some examples are Filaroidea, Pseudophyllidea. e. Family. An order may be subdivided into families. The family's ending is "ae." Some examples are Heterophyidae and Endamoebidae.

67 f. Genus. Each family is made up of various genera (plural of Genus). The genus name may have various endings. The first letter of the genus is capitalized and the name is underlined. The first letter may be used as an abbreviation: Macracanthorhynchus and Entamoeba. g. Species. Each genus is composed of species. The species' name may also have various endings. All letters are small case and the name is underlined. However,the species' name should never be abbreviated: E. histolytica and M. hirudinaceus. h. Identification. Parasitic organisms identified by laboratory procedures are reported by using the genus and species names. Some examples are Giardia Lamblia and Enterobius vermicularis.

68 Taxonomy The major divisions involved in medical parasitology: Protozoa intestinal and urogenital protozoa blood and tissue protozoa nematodes, trematodes, cestodes arthropods.

69 Classification The parasites of humans: the four eukaryotic kingdoms: Protozoa, Animalia (Metazoa) Fungi(Microspora ) Stramenopila (formerly Chromista).

70 Classification Morphology intracytoplasmic structures:the nucleus the type of locomotive organelles Mode of reproduction Biochemistry Molecular biology of lower organisms (e.g., Protozoa, Fungi, and Stramenopila) Comparisons of small subunit ribosomal ribonucleic acid (SSU rrna) protein sequences have made it possible to arrange organisms within groups based on evolutionary distances.

71 Classification The Protozoa: animals whose life functions occur in a single cell

72 Classification The microsporidians single-celled organisms previously classified among the protozoans now thought to be more closely related to fungi

73 Classification Kingdom Animalia:metazoans multicellular animals life functions occur in cellular structures organized as tissue and organ systems.

74 Protozoa simple microorganisms size ranges from 2 to 100 µm their protoplasm is enclosed by a cell membrane contains numerous organelles: a membrane-bound nucleus endoplasmic reticulum food-storage granules Contractile digestive vacuoles

75 Protozoa The nucleus contains clumped or dispersed chromatin and a central karyosome. Organs of motility vary from simple cytoplasmic extrusions or pseudopods to more complex structures, such as flagella or cilia. The kingdom Protozoa: 13 major subgroups, or phyla 7 of which are the concern of medical parasitology.

76 Kingdom: Protozoa Phylum: The Flagellates Amoebozoa Sporozoa Ciliophora

77 Protozoa The Flagellates: -Move by the lashing of their whiplike flagella -The number and position of the flagella vary a great deal in different species. -Flagella may produce a characteristic morphologic appearance that may be useful in species identification.

78 Protozoa Amoebozoa Locomotion of amebae is accomplished by the extrusion of pseudopodia ( false feet ). Amebae are phagocytic and contain mitochondria with tubular cristae.

79 Protozoa Sporozoa -large group -sexually reproducing - spore-forming protozoans - similar morphology at the electron microscopic level - These organisms have a system of organelles at their apical end that produces substances to help the organism penetrate host cells and thus become an intracellular parasite

80 Protozoa Ciliophora free-living and symbiotic species. locomotion involves the coordinated movement of rows of hairlike structures, or cilia. Cilia are structurally similar to flagella but are usually shorter and more numerous. Some ciliates are multinucleate. The only ciliate parasite of humans, Balantidium coli, contains two nuclei: a large macronucleus and a small micronucleus.

81 Classification Protozoa Sarcomastigophora (flagellates and amebas) Apicomplexa (sporozoans) Ciliophora (ciliates) Microspora Helminths Plathyhelminthes (flatworms) Cestoda (flukes) Trematoda (flukes) Nemathelminthes (worm like, seperate-sexed, unsegmented roundworms)

82 Flagellates Intestinal flagellates Giardia intestinalis Trichomonas spp Dientamoeba fragilis Hemoflagellates Leishmania donovani Trypanosoma cruzi Trichomonas vaginalis

83 Amebas Intestinal amebas Entamoeba histolytica Entamoeba coli Free-living amebas Naegleria fowleri Acanthamoeba castellani

84 Sporozoans Blood sporozoans Plasmodium vivax Plasmodium malariae Plasmodium ovale Plasmodium falciparum Babesia microti Other Isospora belli Sarcocystis bovihumanis Cryptosporidium parvum Toxoplasma gondii

85 Animalia (Metazoa) eukaryotic organisms : Helminths ( worms ) Nemathelminthes Platyhelminthes Trematodes, or flukes Cestodes, or tapeworms Arthropods (crabs, insects, ticks, and others)

86 Helminths complex multicellular organisms Elongated bilaterally symmetric They are considerably larger than the protozoan parasites generally are macroscopic, ranging in size from less than 1 mm to 1 m or larger.

87 Helminths The external surface of some worms is covered with a protective cuticle, which is acellular and may be smooth or possess ridges, spines, or tubercles. The protective covering of flatworms is known as a tegument. Often helminths possess elaborate attachment structures, such as hooks, suckers, teeth, or plates. These structures are usually located anteriorly and may be useful in classifying and identifying the organisms Helminths typically have primitive nervous and excretory systems. Some have alimentary tracts; however, none have a circulatory system.

88 Helminths two phyla, the Nemathelminthes and the Platyhelminthes. Nemathelminthes: Roundworms cylindric bodies The sexes of roundworms are separate these organisms have a complete digestive system. intestinal parasites blood and tissue parasites

89 Helminths two phyla, the Nemathelminthes and the Platyhelminthes. Platyhelminthes Flatworms flattened bodies leaflike or resemble ribbon segments Platyhelminthes : Trematodes Cestodes

90 Trematodes Flukes leaf-shaped bodies Most are hermaphroditic, with male and female sex organs in a single body. Their digestive systems are incomplete and only have saclike tubes. Their life cycle is complex; snails serve as first intermediate hosts, and other aquatic animals or plants serve as second intermediate hosts.

91 Cestodes Tapeworms have bodies composed of ribbons of proglottids, or segments. All are hermaphroditic, all lack digestive systems, with nutrition being absorbed through the body walls. The life cycles of some cestodes are simple and direct, whereas those of others are complex and require one or more intermediate hosts.

92 Classification Protozoa Sarcomastigophora (flagellates and amebas) Apicomplexa (sporozoans) Ciliophora (ciliates) Microspora Helminths Plathyhelminthes (flatworms) Cestoda (flukes) Trematoda (flukes) Nemathelminthes (worm like, seperate-sexed, unsegmented roundworms)

93 Cestodes Taenia solium Taenia saginata Echinococcus granulosus Echinococcus multilocularis Diphyllobothrium latum Hymenolepsis nana

94 Trematodes Taenia solium Taenia saginata Echinococcus granulosus Echinococcus multilocularis Diphyllobothrium latum Hymenolepsis nana

95 Nematodes Ascaris lumbricoides Dracunculus medinensis Enterobius vermicularis Wuchereria bacrofti Ancylostoma duodenale Toxocara spp. Loa loa Strongyloides stercoralis Trichinella spiralis Trichuris trichiura

96 Arthropods largest group of animals in the kingdom Animalia. complex multicellular organisms: that may be involved directly in causing invasive or superficial (infestation) disease processes indirectly as intermediate hosts and vectors of many infectious agents, including protozoan and helminthic parasites In addition, envenomization by biting and stinging arthropods can result in adverse reactions in humans that range from local allergic and hypersensitivity reactions to severe anaphylactic shock and death.

97 There are five major categories of arthropods Myriapoda painful bite Pentastomida Humans may serve as intermediate hosts for these parasites. Crustacea The crustaceans include familiar aquatic forms, such as crabs, crayfish, shrimp, and copepods. Several are involved as intermediate hosts in life cycles of various intestinal or blood and tissue helminths. Chelicerata vectors for microbial diseases (mites and ticks) venomous animals that bite (spiders) or sting (scorpions). Insecta aquatic and terrestrial forms: such as mosquitoes, flies, midges, fleas, lice bugs, wasps, and ants. vectors for microbial diseases (mosquitoes, fleas, lice, and bugs) s venomous animals that sting (bees, wasps, and ants).

98 Physiology and Replication of Protozoa The nutritional requirements are generally simple require the assimilation of organic nutrients. The amebae, ameboflagellates, and certain other protozoa accomplish this assimilation by the rather primitive process of pinocytosis or phagocytosis of soluble or particulate matter.the engulfed material is enclosed in digestive vacuoles. The flagellates and ciliates generally ingest food at a definitive site or structure, the peristome or cytostome. Other unicellular parasites, such as the intracellular microsporidia, assimilate nutrients by simple diffusion. The ingested food material may be retained in intracytoplasmic granules or in vacuoles. The undigested particles and waste may be eliminated from the cell by extrusion of the material at the cell surface. Respiration in most parasitic protozoa is accomplished by facultatively anaerobic processes.

99 Physiology and Replication of Protozoa Under harsh or unfavorable environmental conditions Many develop cyst form: less metabolically active surrounded by a thick external cell wall capable of protecting the organism from otherwise lethal physical and chemical insults an integral part of the life cycle of many protozoan parasites and facilitates the transmission of the organism from host to host in the external environment Parasites that cannot form cysts: must rely on direct transmission from host to host or require an arthropod vector to complete their life cycles.

100 Physiology and Replication of Protozoa Many protozoan parasites have developed elaborate immunoevasive mechanisms that allow them to respond to attack by the host immune system by continuously changing their surface antigens, thus ensuring continued survival within the host.

101 Physiology and Replication of Protozoa Reproduction: generally by simple binary fission (merogony) although the life cycle of some protozoa, such as the sporozoans, includes cycles of multiple fission (schizogony) alternating with a period of sexual reproduction (sporogony or gametogony).

102 Physiology and Replication of Animalia Helmintes: Nutritional requirements met by Active ingestion of host tissue, fluid: tisse distruction Passive absorbsion Energy is used: Muscular motility Reproduction: many worms quite profilic and produce as many as off springs

103 Physiology and Replication of Animalia Helmintes: -Generally lay eggs: oviparous Few: bear live young(viviparous): produce larvae distinct from adult Primarily anaerobic Larval forms may require oxygen

104 Physiology and Replication of Animalia Most Helmintes: Protection barrier: -tough external layer-cuticle:tegument Worms : -secrete enzymes :destroy host cell and neutralize immunologic and cellular defense mechanisms

105 Physiology and Replication of Animalia Alter antigenic properties of external surfaces Evade host immune system Incorporate host antigen in their external cuticular layer Avoid immunologic recognition: Schistosomiasis

106 Physiology and Replication of Arthropods Segmented bodies Joined appendages Well dveloped digestive and nervous systems Seperate sex Hard chitin outside:exoskeleton Respiration via gills or tubular body structures

107 EPIDEMIOLOGY Epidemiology is the science that studies -propagation and prevalence of human disease - It determines the frequency and distribution of a disease in a community.

108 EPIDEMIOLOGY. a. Endemic A disease is endemic when it is present in a community at all times but is clinically found in a few individuals and with low morbidity. b. Hyperendemic A hyperendemic disease is one that is present in a high frequency in a community. c. Sporadic A low frequency of disease that is not widely diffused is referred to as sporadic. d. Epidemic An epidemic occurs when a disease spreads rapidly through a community and affects a large number of individuals. Pandemic:Whole world is affected: Influenza, AIDS

109 Mode of Infection Some parasites can infect the host by direct contact while others require a complex mechanism to enter the host: (1) Direct contact. Some parasites can complete their life cycle by being transmitted from an infected site to another site where there is no disease. Then they can parasitize either the new or the same host.

110 Mode of Infection (2) Congenital. Some parasites can be transmitted to the younger generation by the older generation. malaria, toxoplasmosis several other parasitic diseases may be accomplished by parasitic forms crossing the placental barrier from the mother's blood to the unborn fetus.

111 Mode of Infection (3) Ingestion. Food and water are very important in the spread of parasitic diseases because most parasites inhabit the gastrointestinal tract. The infective form of the parasite (ova or larvae) may be present in the flesh of the intermediate host (plant or animal) or may be swimming free in contaminated water. The organism may gain access to food through contamination with -soil -water -the hands of foodhandlers, by mechanical agents -by biological carriers such as insects. In some instances, the intermediate hosts, like small arthropods, are consumed with the food or water.

112 Mode of Infection (4) Arthropod-borne Members of the phylum Arthropoda serve as vectors (carriers) : - parasitic diseases - bacterial - viral infections The vector is an integral part of the life cycle of the parasite. In some instances the arthropods are intermediate hosts while in others they are the definitive host.

113 Mode of Infection (5) Active penetration larval stage may have the capability of penetrating the host tissues. (6) Transfusion. Certain blood and tissue parasites

114 PREVENTIVE MEASURES The individual, as well as the community, must get involved in the prevention of parasitic infections. Life cycles of parasites may be interrupted by eradication of the vectors. Education about hygiene, eating habits, and disposal of human and animal wastes can also be used in combating parasites. Treatment of diseased individuals not only relieves the suffering, but also prevents the spread of the disease.

115 Emerging and reemerging microorganisms HIV Crimean-Congo haemorrhagic fever West Nile virus Influenza(Avian flue, Pandemic flue) Sars (SARS-CoV) EBOLA MERS-CoV.....

116 Who Cdc, ecdc saglik.gov.tr, Society websites ( klimik.org,

117 Medical Microbiology Patrick R Murray Ken S Rosenthal Michael A Pfaller