sign in sign up
<<
Home , Pinworm infection

Lecture PowerPoint to accompany Foundations in Microbiology Seventh Edition

Talaro Chapter 23 The Parasites of Medical Importance

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 23.1 Parasitology

• The study of eukaryotic parasites, protozoa, and helminths • Cause 20% of all infectious diseases • Less prevalent in industrialized countries; increasingly common in AIDS patients

2 23.2 Typical Protozoan

• Single-celled, animal-like microbes, most having some form of motility • Estimated 100,000 species, approximately 25 are important pathogens • Life cycles vary – Most propagate by simple asexual cell division of the active feeding cell (trophozoite) – Many undergo formation of a cyst – Others have a complex life cycle that includes asexual and sexual phases

3 4 5 Infective Amebas

6 Entamoeba Histolytica and Amebiasis

• Alternates between a large trophozoite, motile by means of pseudopods and a smaller nonmotile cyst • Trophozoite has a large nucleus and lacks most other organelles • Humans are the primary hosts • Ingested • Carried by 10% of world population

7 Figure 23.1 Entamoeba histolytica

8 Entamoeba Histolytica

• Cysts are swallowed and arrive at the ; alkaline pH and digestive juices stimulate cysts to release 4 trophozoites • Trophozoites attach, multiply, actively move about and feed • Asymptomatic in 90% of patients • Ameba may secrete enzymes that dissolve tissues and penetrate deeper layers of the mucosa • Causing dysentery, abdominal , fever, , and

9 Figure 23.2 Intestinal amebiasis

10 Entamoeba Histolytica

• Life-threatening manifestations are: hemorrhage, perforation, , and tumorlike growths, amoebomas • May invade liver and lung • Severe forms of disease result in 10% fatality rate • Effective drugs are iodoquinol, metronidazole, and chloroquine

11 Figure 23.3 Entamoeba histolytica in specimen

12 Amebic of the Brain

• Caused by Naegleria fowleri and Acanthamoeba • Ordinarily inhabit standing water • Primary acute meningoencephalitis is acquired through nasal contact with water or traumatic eye damage • Infiltration of brain is usually fatal

13 An Intestinal Ciliate: Balantidium Coli

• An occupant of the intestines of domestic animals such as pigs and cattle • Acquired by ingesting cyst-containing or water • Trophozoite erodes intestine and elicits intestinal symptoms • Healthy humans are resistant • Rarely penetrates intestine or enters blood • Treatment – tetracycline, iodoquinol, nitrimidazine or metronidazole

14 Figure 23.5 (a) Microscopic views of Balantidium coli

15 The Flagellates

16 Trichomonads: Trichomonas Species

• Small, pear-shaped • 4 anterior flagella and an undulating membrane • Exist only in trophozoite form • 3 infect humans: – T. vaginalis – T. tenax – T. hominis

17 Figure 23.6 Trichomonads of humans

18 Trichomonas Vaginalis • Causes an STD called trichomoniasis • Reservoir is human urogenital tract • 50% of infected are asymptomatic • Strict parasite, cannot survive long outside of host • 3 million cases yearly, a top STD • Female symptoms – foul-smelling, green-to-yellow discharge; vulvitis; cervicitis; urinary frequency and pain • Male symptoms – urethritis, thin, milky discharge, occasionally prostate • Metronidazole

19 Giardia Lamblia and Giardiasis • Pathogenic flagellate • Unique symmetrical heart shape with concave ventral surface that acts like a suction cup • Cysts are small, compact, and multinucleate • Reservoirs include beavers, cattle, coyotes, cats, and humans • Cysts can survive for 2 months in environment • Usually ingested with water and food • ID 10 to 100 cysts

20 Figure 23.7 (a) Identification of trophozoites

21 • Cysts enter , germinate, travel to jejunum to feed and multiply • Causes giardiasis – diarrhea, • Diagnosis is difficult because organism is shed in feces intermittently • Treatment: quinacrine or metronidazole • Agent is killed by boiling, ozone, and iodine

22 Hemoflagellates: Vector-Borne Blood Parasites • Obligate parasites that live in blood and tissues of human host • Cause life-threatening and debilitating zoonoses • Spread in specific tropical regions by blood- sucking insects that serve as intermediate hosts • Have complicated life cycles and undergo morphological changes • Categorized according to cellular and infective stages

23 Hemoflagellates

• Amastigote: the form lacking a free flagellum • Promastigote: the stage bearing a single, free, anterior flagellum • Epimastigote: the flagellate stage • Trypomastigote: large, fully formed stage

24 25 Trypanosoma Species and Tropanosomiasis

• Distinguished by their infective stage; trypomastigote is an elongate, spindle- shaped cell with tapered ends, eel-like motility • 2 types of trypanosomiasis: – T. brucei – African sleeping sickness – T. cruzi – Chagas disease – endemic to Central and South America

26 Trypanosoma Brucei and African Sleeping Sickness • Spread by tsetse flies • Harbored by reservoir mammals • Two variants of disease caused by 2 subspecies: – T.b. gambiense – Gambian strain; West Africa – T.b. rhodesiense – Rhodesian strain; East Africa • Biting of fly inoculates skin with trypomastigotes, which multiplies in blood and damages spleen, lymph nodes, and brain

27 Figure 23.8 Cycle of the tsetse fly vector

28 Trypanosoma Brucei and African Sleeping Sickness • Chronic disease symptoms are sleep disturbances, tremors, paralysis, and coma • Trypanosomes are readily demonstrated in blood, spinal fluid, or lymph nodes • Treatment before neurological involvement melarsoprol, eflornithine • Control involves eliminating tsetse fly

29 Trypanosoma Cruzi • Causes Chagas disease • Reduviid bug (kissing bug) is the vector • Infection occurs when bug feces is inoculated into a cutaneous portal • Local lesion, fever, and swelling of lymph nodes, spleen, and liver • Heart muscle and harbor masses of amastigotes • Chronic inflammation occurs in the organs (especially heart and brain) • Treatment nifurtimox and benzonidazole

30 Figure 23.9 American trypanosomiasis (Chagas disease)

31 Figure 23.10 Conditions associated with Chagas disease

32 Leishmania Species and Leishmaniasis

• Leishmaniasis – zoonosis transmitted among mammalian hosts by female sand flies that require a blood meal to produce eggs • Endemic to equatorial regions • Promastigotes are injected with sand fly bite, convert to amastigote and multiply; if macrophage does not migrate the infection is localized; systemic if macrophage migrates

33 • Cutaneous-oriental sore, Baghdad boil – localized ulcerated sore • Espundia – skin and infection of the head; chronic infection • Systemic (visceral) – high intermittent fever; weight loss, enlarged spleen, liver, and lymph nodes – Kala azar is the most severe and fatal form if untreated

34 Figure 23.11 Life cycle and pathology of Leishmania species

35 23.3 Apicomplexan Parasites

• Sporozoans • Lack locomotor organelles in the trophozoite state • Alternate between sexual and asexual phases and between different animal hosts • Most form specialized infective bodies that are transmitted by arthropod vectors, food, water, or other means – Plasmodium – Toxoplasma – Cryptosporidium

36 Plasmodium: The Agent of Malaria

• Dominant protozoan disease • Obligate intracellular sporozoan • 4 species: P. malariae, P. vivax, P. falciparum, and P. ovale • Female Anopheles mosquito is the primary vector; blood transfusions, mother to fetus • 300-500 million new cases each year • 2 million deaths each year

37 Figure 23.12 The malaria belt

38 2 distinct phases of malarial parasite development: • Asexual phase – human host – Infected female mosquito injects asexual sporozoite which localizes in liver; it then undergoes schizogony generating numerous merozoites which enter circulation in 5-16 days depending on species – Merozoites attach to and enter red blood cells, convert to trophozoites and multiply; red cell bursts releasing merozoites that differentiate into gametes

39 • Sexual phase – mosquito host – Mosquito draws infected RBCs; gametes fertilize forming diploid cell which forms sporozoites in stomach – Sporozoites lodge in salivary glands; available to infect human host

40 Figure 23.13 Plasmodium

41 Plasmodium • Symptoms include episodes of chills-fever-sweating, anemia, and organ enlargement • Symptoms occur at 48-72 hour intervals as RBCs rupture; interval depends on species • P. falciparum most malignant type; highest death rate in children • Diagnosis by presence of trophozoite in RBCs, symptoms • Increasing drug resistance • Therapy is chloroquine, mefloquine

42 Figure 23.14 Malaria

43 Coccidian Parasites

• Zoonotic in domestic animals and birds

44 Toxoplasma Gondii and Toxoplasmosis

• Intracellular apicomplexan parasite with extensive distribution • Lives naturally in cats that harbor oocysts in the GI tract • Acquired by ingesting raw meats or substances contaminated by cat feces • Most cases of toxoplasmosis go unnoticed except in fetus and AIDS patients who can suffer brain and heart damage • Treatment: pyrimethamine and sulfadiazine

45 Figure 23.16 The life cycle and morphological forms of Toxoplasma gondii

46 Figure 23.17 Toxoplasmosis in the brain of an AIDS patient

47 Sarcocystis and Sarcocystosis

• Sarcocystis – parasites of cattle, swine, and sheep • Domestic animals are intermediate hosts; they pick up infective cysts while grazing on grass contaminated with • Humans are infected when the meat is consumed • Symptoms include diarrhea, nausea, and abdominal pain • No specific treatment

48 Cryptosporidium: A Newly Recognized Intestinal

• An intestinal pathogen • Infects a variety of mammals, birds, and reptiles • Exists in tissue and oocyst phases • 1990s – 370,000 cases in Milwaukee, WI, due to contaminated water; filtration required for removal • of oocysts gives rise to sporozoites that penetrate intestinal cells • Causes gastroenteritis, headache, sweating, vomiting, abdominal cramps, diarrhea • AIDS patients may suffer chronic persistent diarrhea • No effective drugs 49 Figure 23.18 Other apicomplexan parasites

50 Isospora Belli and Coccidiosis

• Intracellular intestinal parasite with oocyst stage • Transmitted in fecally contaminated food or drink • Infection usually asymptomatic or self-limited • Symptoms include malaise, nausea and vomiting, diarrhea, fatty stools, abdominal cramping, and weight loss • Treat with sulfadiazine and pyrimethamine, when required

51 Cyclospora Cayetanensis and Cyclosporiasis

• Emerging protozoan pathogen; causes cyclosporiasis • Oral-fecal ; fresh produce and water • Oocysts enter small intestine and invade the mucosa • Symptoms of watery diarrhea, stomach cramps, bloating, fever, muscles aches • Diagnosis can be complicated • Treatment: trimethoprim and sulfamethoxazole

52 Figure 23.19 Cyclospora in a human fecal sample

53 Babesia Species and Babesiosis

• First protozoan found to cause a disease – redwater fever of cattle • First protozoan found to be associated with a vector – tick • Human babesiosis – relatively rare zoonosis • Associated with infected rodents • Infection resembles malaria

54 23.4 A Survey of Helminth Parasites

• Adults are large, multicellular animals with specialized tissues and organs • Adult mate and produce fertilized eggs that hatch; larvae then mature in several stages to adults • The sexes may separate or hermaphroditic • Adulthood and mating occur in the definitive host • Larval develop occurs in the intermediate host • A transport host experiences no parasitic development • Four basic patterns of life and transmission

55 Figure 23.20 Four helminth cycles

56 57 Helminths

• Pathology arises from worms feeding on and migrating through tissues, accumulation of worms, and products • Diagnosis based on blood cell count (eosinophilia), serological tests; eggs, larvae, or adult worms in feces; sputum, urine, blood, or tissue biopsies • Antihelminthic drugs suppress a helminthic metabolic process that differs from the human process, inhibit the worm’s movement, prevent it from holding position, and act locally in the intestine

58 59 (Roundworm)

• Most abundant animal groups; 50 species that affect humans • Elongated, cylindrical worms with protective cuticles, circular muscles, a complete digestive tract, and separate sexes • Divided into intestinal , and tissue nematodes

60 Figure 23.21

61 Ascaris Lumbricoides • A large intestinal roundworm • Most cases in the U.S. occur in the southeastern states • Indigenous to humans • Ascaris spends its larval and adult stages in humans; release embryonic eggs in feces, and are spread to other humans; food, drink, or contaminated objects • Ingested eggs hatch into larvae and burrow through the intestine into circulation and travel to the lungs and pharynx and are swallowed • Adult worms complete cycle in intestines and reproduce – 200,000 eggs/day 62 Ascaris Lumbricoides

• Worms retain motility, do not attach • Severe inflammatory reactions mark the migratory route • Allergic reactions can occur • Heavy worm loads can retard physical and mental development

63 and Whipworm Infection • Whipworm • Humans sole host • has its highest incidence in the tropics • Eggs hatch in intestines, larvae attach, penetrate the outer wall and develop into adults • Females lay 3,000-5,000 eggs daily • Worms can pierce capillaries, cause localized hemorrhage • Heavy infestations can cause dysentery, rectal prolapse – can be fatal in children

64 Enterobius Vermicularis and Infection • Pinworm or seatworm • Enterobiasis most common worm disease of children in temperate zones • Eggs are picked up from surroundings and swallowed • After hatching in the small intestine, they develop into adults • Anal itching occurs when mature females emerge from intestine to release eggs • Self-inoculation is common • Tape test

65 • Characteristic curved ends and hooked mouths • and • Humans shed eggs in feces, which hatch into filariform larvae and burrow into the skin of bare feet • Larvae travel from blood to lungs, proceed up bronchi and throat and are swallowed • Worms mature and reproduce in small intestine and complete the cycle • May cause pneumonia, nausea, vomiting, cramps, and bloody diarrhea • Blood loss is significant – anemia 66 Figure 23.22 The hookworms

67 Strongyloides Stercoralis and • Threadworm • Tiny roundworms completes life cycle in humans or moist soil • Larvae penetrate skin and migrate to lungs, are swallowed, and complete development in the intestine • Can reinfect the same host without leaving the body • Heavy worm loads can cause pneumonitis and eosinophilia, bloody diarrhea, liver enlargement, bowel obstruction, and malabsorption 68 and Trichinellosis

• Life cycle entirely within mammalian host • Acquired from eating undercooked or bear meat • Larvae migrate from intestine to blood vessels, muscle, heart, and brain, where it forms cysts • First symptoms – flulike, diarrhea • Second symptoms – muscle and joint pain, shortness of breath, pronounced eosinophilia • No cure after have encysted

69 Figure 23.24 The cycle of trichinellosis

70 Tissue Nematodes

• Complete their life cycle in human blood, lymphatics, or skin • Filarial worms; elongate, filamentous bodies, spread by biting arthropods • Cause chronic, deforming disease • – elephantiasis • – river blindness • – eye worm

71 Wucherereia Bancrofti and Bancroftian • Tropical infection spread by mosquitoes • Vector deposits larvae which move into lymphatics and develop into adults • Chronic infection causes blockage of lymphatic circulation and elephantiasis, massive swelling in the extremities

72 Figure 23.25 Bancroftian filariasis

73 Onchocerca Volvulus and River Blindness • Transmitted by biting black flies • Larvae develop into adults in subcutaneous tissues • Adult females migrate via the blood to the eyes, provoking inflammatory reactions • Coinfection with Wolbachia causes river blindness • Treatment: tetracycline and ivermectin

74 Loa Loa: The African Eye Worm

• Spread by bite of small flies • Temperature-sensitive worm migrates around/under the skin and may enter the eye • Treatment – pull worm from a small hole in conjunctiva or diethylcarbamazine

75 Trematodes or Flukes

• with ovoid leaflike bodies • Have digestive, excretory, neuromuscular, and reproductive systems • Lack circulatory and respiratory systems • Animals such as snails or fish are usually the intermediate hosts and humans are the definitive hosts

76 Blood Flukes: Schistosomes

• – prominent • mansoni, S. japonicum, S. haematobium • Adult flukes live in humans who release eggs into water; early larva (miracidium) develops in freshwater snail into a 2nd larva (cercaria) • This larva penetrates human skin and moves into the liver to mature; adults migrate to intestine or bladder and shed eggs, giving rise to chronic organ enlargement

77 Figure 23.26 Stages in the life cycle of Schistosoma

78 Liver and Lung Flukes

• Zoonotic Liver flukes: • Opisthorchis (Clonorchis) sinensis – cycles between mammals and snails and fish; humans are infected by eating inadequately cooked fish containing cercariae, larvae crawl into bile duct, mature, and shed eggs into feces; snail are infected • – cycles between herbivores, snails, and aquatic plants; humans are infected by eating raw aquatic plants; fluke lodges in liver

79 Lung fluke: • – cycles between carnivorous animals, snails, and crustaceans; humans infected by eating undercooked crustaceans; intestinal worms migrate to lungs

80 Figure 23.27 Fasciola hepatica

81 Cestode (Tapeworm) Infestations

• Flatworms • Long, very thin, ribbonlike bodies composed of sacs (proglottids) and a scolex that grips the intestine • Each proglottid is an independent unit adapted to absorbing food and making and releasing eggs • •

82 Taenia Saginata • Beef tapeworm • Very large, up to 2,000 proglottids • Humans are the definitive host • Animals are infected by grazing on land contaminated with human feces • Infection occurs from eating raw beef in which the larval form has encysted • In humans, larva attaches to the small intestine and becomes an adult • Causes few symptoms; vague abdominal pain and nausea; proglottids in stool

83 Figure 23.28 Tapeworm in humans

84 Taenia Solium • Pork tapeworm • Infects humans through ingesting cysts or eggs • Eggs hatch in intestine, releasing tapeworm larva that migrate to all tissues and encyst • Most damaging if they lodge in heart muscle, eye, or brain • May cause seizures, psychiatric disturbances

85 Figure 23.29

86 23.5 The Arthropod Vectors of Infectious Disease

• Arthropods – exoskeleton and jointed legs; includes arachnids and crustaceans; many must feed on blood and tissue fluid of host during life cycle; ectoparasites • Those of medical importance transmit infectious microbes in the process of feeding – biological vectors

87 88 Insects • Mosquitoes – require an aquatic habitat; females take blood meal transmitting disease: malaria, filariasis, Dengue fever • Fleas – highly motile, flattened bodies; feed on warm-blooded animals; carry zoonotic diseases: plague, murine typhus • Lice – small, soft; attach to head and body hair feeding inconspicuously on blood and tissue fluid; release feces that contaminate wound; epidemic typhus, relapsing fever

89 Arachnids • Ticks – cling on vegetation and attach to host on contact; larvae, nymph, and adults get blood meal by piercing skin of host – Hard or ixodid ticks – small compact, rigid bodies; transmit bacterial, rickettsial, and viral diseases – Soft or argasid ticks – flexible outer bodies; transmit relapsing fever

90 Figure 23.30 Arthropod vectors

91