1. B IOLOGY OF PARASITES

2. B IOLOGY OF P ROTOZOAN PARASITES Phylum: Protozoa Subphylum: Plasmodroma 1. Class: Mastigophora/ Flagellata (eg. Trypanosoma; Leishmania; Trichomonas; Giardia) 2. Rhizopoda/ Sarcodina ( Entamoeba ) 3. Sporozoa ( Plasmodium) ; Myxospora ( Myxobolus cerebralis ) (Protozoa or Cnidaria?) Subphylum: Ciliophora 1. Suctoria (No known parasite) 2. Ciliata ( Balantidium coli, Ichthyophthirius multifilis )

3. Biology of Balantidium coli  only Ciliate known to be pathogenic to humans.  the largest protozoan parasite of humans.  primarily a parasite of pigs, with strains adapted to various other hosts.  lives in the cecum and colon of humans, pigs, and many other mammals.  B. coli has two stages: trophozoite and cyst.

4. Biology of Balantidium coli  cysts (commonly) and trophozoite (rarely) are infective and diagnostic stage  not readily transmissible from one species of host to another  require a period of time to adjust to the symbiotic flora of a new host.  If adapted can be a serious pathogen

5. Biology of Balantidium coli The host most often acquires the cyst through ingestion of contaminated food or water.

6. Biology of Balantidium coli  Following ingestion, excystation occurs in the small intestine  Then trophozoites colonize the large intestine.  Unencysted trophozoites may live up to 10 days  Encystment is activated by dehydration of feces

7. Biology of Balantidium coli  The trophozoites in the large intestine replicate by binary fission, during which conjugation may occur.  Some trophozoites invade the wall of the colon and multiply.  In animals other than primates, B. coli is unable to initiate a lesion by itself, but it can become a secondary invader if the mucosa is ruptured by other means.

8. Biology of Balantidium coli  Trophozoites undergo encystation to produce infective cysts.  Mature cysts are passed with feces.  B. coli is destroyed by a pH lower than 5  Hence, infection is most likely to occur in malnourished persons with low stomach acidity.

9. Biology of Ichthyophthirius multifilis  A ciliate protozoan  A ectoparasite  Causes a freshwater white spot disease, also called freshwater ich (or ick)  It is easily introduced into a fish pond or home aquarium by new fish or equipment.  If not controlled, there is a 100% mortality rate of fish.  The disease can be controlled but the cost is high in terms of lost fish, labor, and cost of chemicals.

10. Biology of Ichthyophthirius multifilis  Trophozoite is round in shape, up to 1 mm in diameter, known as “trophont”.  The trophozoite (trophont) feeds in a nodule formed in the skin or gill epithelium.  Numerous short cilia are present over entire cell

11.  After 7-10 days, the trophont which attaches to gills or skin releases into environment  This free living form is called a “tomont”  Tomont is morphologically same as trophont, but cilia are more obvious.  Then, tomont attaches to substrate and is encysted to form cyst Biology of Ichthyophthirius multifilis

12.  Then, cyst is multiply into numerous Tomite by binary fission. Biology of Ichthyophthirius multifilis

13.  Cyst ruptures to release Tomites as free living ciliated forms called, Theront.  Theronts then infects the new fish and starts new cycle of life. Biology of Ichthyophthirius multifilis

14. Myxobolus cerebralis  a myxosporean parasite of salmonids (salmon, trout, and their allies)  causes whirling disease (Fish "whirl" due to skeletal deformation and neurological damage)  causes death up to 90% of infected population  is not transmissible to humans  has many diverse stages ranging from single cells to relatively large spores

15. Biology of Myxobolus cerebralis There are 3 main stages of M. cerebralis : 1. Triactinomyxon stage 2. Sporoplasm stage 3. Myxosporean stage

16. Biology of Myxobolus cerebralis  Myxobolus cerebralis has a two-host life cycle involving:  a salmonid fish and  a tubificid oligochaete.  There is a transmission stage between salmonid host stage and tubificid host stage. Salmonid host Transmission stage Tubificid host

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27. B IOLOGY OF P LATYHELMINTHES Phylum: Platyhelminthes Three classes: 1. Class Turbellaria (Mostly free living or commensals) 2. Class Trematoda Order-Digenea ( Fasciola hepatica ; Schistosoma sp.) 3. Class Cestoda ( Taenia solium; T. saginata )

28. Biology of Fasciola hepatica Fasciola hepatica:  is known as Common/ Sheep Liver Fluke(trematodes)  causes the disease fascioliasis  is one of the largest flukes of the world (30 mm by13 mm)  is leaf-shape, pointed at the end  has small but powerful oral sucker  The acetabulum is larger than the oral sucker

29. Biology of Fasciola hepatica 1. Immature Fasciola eggs are discharged in the biliary ducts and in the stool

30. Biology of Fasciola hepatica 2. Eggs become embryonated in water

31. Biology of Fasciola hepatica 3. eggs release miracidia

32. Biology of Fasciola hepatica 4. M iracidia invade a suitable snail intermediate host, including the genera Galba, Fossaria and Pseudosuccinea.

33. Biology of Fasciola hepatica 4. In the snail the parasites undergo several developmental stages (sporocysts, rediae, and cercariae ).

34. Biology of Fasciola hepatica 5. The cercariae are released from the snail and encyst as metacercariae on aquatic vegetation or other surfaces.

35. Biology of Fasciola hepatica 6. Humans and other mammals can become infected by ingesting metacercariae-containing freshwater plants.

36. Biology of Fasciola hepatica 7. After ingestion, the metacercariae excyst in the duodenum and migrate through the intestinal wall, the peritoneal cavity, and the liver parenchyma into the biliary ducts.

37. Biology of Fasciola hepatica 8. In the biliary ducts, metacercariae develop into adult flukes. In humans, maturation from metacercariae into adult flukes takes approximately 3 to 4 months. Then, the adult flukes reside in the large biliary ducts of the mammalian host.

38. Biology of Fasciola hepatica

39. Biology of Taenia solium & T. saginata  T. saginata is known as beef tapeworm and T. solium is known as pork tapeworm.  Adult tapeworm causes the disease called “Taeniasis”  Larva of T. solium causes the disease in human called “Cysticercosis”  Humans are the definitive hosts for T. saginata and T. solium.  Length of adult worms is usually 5 m or less for T. saginata and 2 to 7 m for T. solium. Taenia solium T. saginata

40. Biology of Taenia solium & T. saginata  T. solium has rostellum of hooklets but T. saginata has no hooklets.  T. saginata adults usually have 1,000 to 2,000 proglottids, while T. solium adults have an average of 1,000 proglottids.  T. saginata may produce up to 100,000 and T. solium may produce 50,000 eggs per proglottid respectively. Taenia solium T. saginata

41. Biology of Taenia solium & T. saginata 1. Eggs or gravid proglottids are passed with feces; the eggs can survive for days to months in the environment.

42. Biology of Taenia solium & T. saginata 2. Cattle ( T. saginata ) and pigs ( T. solium ) become infected by ingesting vegetation contaminated with eggs or gravid proglottids

43. Biology of Taenia solium & T. saginata 3. In the animal's intestine, the oncospheres hatch, invade the intestinal wall, and migrate to the striated muscles, where they develop into cysticerci. A cysticercus can survive for several years in the animal.

44. Biology of Taenia solium & T. saginata 4. Humans become infected by ingesting raw or undercooked infected meat.

45. Biology of Taenia solium & T. saginata 5. In the human intestine, the cysticercus develops over 2 months into an adult tapeworm, which can survive for years. The adult tapeworms attach to the small intestine by their scolex

46. Biology of Taenia solium & T. saginata 6. Adults reside in the small intestine. The adults produce proglottids which mature, become gravid, detach from the tapeworm, and migrate to the anus.

47. B IOLOGY OF N EMANTODA Parasites belonging to following two classes will be discussed: 1. Class Adenophorea (eg. Trichuris trichiura ) 2. Class Secernentea (eg. Ascaris lumbricoides )

48. Biology of Trichuris trichiura  It is a nematode (round worm) belonging to class Adenophorea  It causes the disease called “Trichuriasis”  Trichuris trichiura is known as the human whipworm.  It looks like a whip with wider "handles" at the posterior end.  The life span of the adults is about 1 year.

49. Biology of Trichuris trichiura 1. The unembryonated eggs are passed with the stool

50. Biology of Trichuris trichiura 2. In the soil, the eggs develop into a 2-cell stage

51. Biology of Trichuris trichiura 3. An advanced cleavage stage occurs and then they embryonate

52. Biology of Trichuris trichiura 4. Eggs become infective in 15 to 30 days and become infected by ingestion (soil-contaminated hands or food).

53. Biology of Trichuris trichiura 5. After ingestion, the eggs hatch in the small intestine, and release larvae

54. Biology of Trichuris trichiura 6. Larvae mature and establish themselves as adults in the colon. The adult worms (approximately 4 cm in length) live in the cecum and ascending colon. The females begin to oviposit 60 to 70 days after infection. Female worms in the cecum shed between 3,000 and 20,000 eggs per day.

55. Biology of Ascaris lumbricoides  It is a nematode (round worm) belonging to class Secernentea  It causes the disease called “ Ascariasis ”  It is known as the giant or human intestinal roundworm.  It is the largest nematode parasitizing the human intestine. (Adult females: 20 to 35 cm; adult male: 15 to 30 cm.)  Adult worms can live 1 to 2 years.

56. Biology of Ascaris lumbricoides 1. Adult worms live in the lumen of the small intestine. A female may produce approximately 200,000 eggs per day.

57. Biology of Ascaris lumbricoides 2. Eggs are passed with the feces. Unfertilized eggs may be ingested but are not infective.

58. Biology of Ascaris lumbricoides 3. Fertile eggs embryonate and become infective after 18 days to several weeks, depending on the environmental conditions (optimum: moist, warm, shaded soil).

59. Biology of Ascaris lumbricoides 4. Infective embryonated eggs are swallowed.

60. Biology of Ascaris lumbricoides 5. The larvae hatch, invade the intestinal mucosa.

61. Biology of Ascaris lumbricoides 6. From the intestinal mucosa, the larvae are carried via the portal, then systemic circulation to the lungs. Then, the larvae mature further in the lungs (10 to 14 days), penetrate the alveolar walls.

62. Biology of Ascaris lumbricoides 7. From the alveolar walls, the larvae ascend the bronchial tree to the throat, and are swallowed.

63. Biology of Ascaris lumbricoides  Upon reaching the small intestine, they develop into adult worms.  Between 2 and 3 months are required from ingestion of the infective eggs to oviposition by the adult female.

64. Arthropoda Class Insecta:  Order- Siphonoptera (Fleas) and  Order- Mallophaga (Lice) Class Arachnida:  Subclass- Acarina (Mites and Ticks)

65. Biology of Fleas Many species of fleas can feed on humans. For example: The human flea, Pulex irritans, is  less-commonly seen these in industrialized areas.  not an effective vector of disease  an intermediate host for few species of cestodes. The dog and cat fleas ( Ctenocephalides canis and C. felis )  may also feed on humans.  intermediate hosts for cestodes.  C. felis can serve as a vector of Rickettsia felis. The Oriental rat flea ( Xenopsylla cheopis ) is  the primary vector for Yersinia pestis (plague).

66. Biology of Fleas Fleas, like other holometabolous insects, have a four-part life cycle consisting of  eggs,  larvae,  pupae,  adults.

67. Biology of Fleas 1. Eggs are shed by the female in the environment.

68. Biology of Fleas 2. Eggs hatch into larvae in about 3-4 days and feed on organic debris in the environment. The number of larval instars varies among the species.

69. Biology of Fleas 3. Larvae eventually form pupae, which are in cocoons that are often covered with debris from the environment (sand, pebbles). The larval and pupal stages take about 3-4 weeks to complete.

70. Biology of Fleas 4. Afterwards, adults hatch from pupae and seek out a warm- blooded host for blood meals.

71. Biology of Fleas 5. The primary hosts for C. felis, C. canis, X. cheopis and P. irritans are cats, dogs, rodents (rats) and human respectively, although other mammals, may be fed upon. In North America, plague ( Yersinia pestis ) is cycled between X. cheopis and prairie dogs.

72. Biology of Head Lice Pediculus humanus capitis, the head louse:  is an insect of the order Mallophaga  is an ectoparasite whose only host is human.  feeds on blood several times daily  resides close to the scalp to maintain its body temperature.

73. Biology of Head Lice Like other hemimetabolous insect, the head louse has three stages in life cycle:  egg,  nymph  adult.

74. Biology of Head Lice 1.Eggs:  Louse eggs, called nits are hard to see.  Nits are laid by the adult female and are cemented at the base of the hair shaft nearest the scalp.  They are oval (0.8 mm by 0.3 mm) and yellow to white.  Viable eggs are usually located within 6 mm of the scalp.  Nits take about 1 week to hatch (range 6 to 9 days).

75. Biology of Head Lice 2. 1 st nymph:  The egg hatches to release a 1 st nymph.  The nit shell then becomes a more visible dull yellow and remains attached to the hair shaft.  The nymph looks like an adult head louse, but is about the size of a pinhead.

76. Biology of Head Lice 3. 2 nd nymph:  1 st nymph develop into 2 nd nymph after 1 st molting

77. Biology of Head Lice 4. 3 rd nymph:  2 nd nymph develop into 3 rd nymph after 2 nd molting

78. Biology of Head Lice 5. Adult:  3 rd nymph mature into adult after 3rd molting.  Nymphs become adults about 7 days after hatching.  Females are usually larger than males  The adult has 6 legs with claws, and is tan to grayish-white  Females can lay up to 8 nits per day.  Adult lice can live up to 30 days on a person’s head.  To live, adult lice need to feed on blood several times daily.  Without blood meals, the louse will die within 1 to 2 days.

79. Biology of Mites ( Sarcoptes scabiei ) Sarcoptes scabiei var. hominis is called the human itch mite, It is belonging to Class Arachnida, subclass Acarina (Acari) It causes scabies in human Transmission occurs primarily by the transfer of the impregnated females during person-to-person contact. Occasionally transmission may occur via fomites Other races of scabies mites may cause infestations in other mammals. Races of mites found on other animals may cause a self-limited infestation in humans.

80. Biology of Mites ( Sarcoptes scabiei ) Sarcoptes scabiei undergoes four stages in its life cycle:  egg,  larva  nymph  adult

81. Biology of Mites ( Sarcoptes scabiei ) Females deposit 2-3 eggs per day as they burrow under the skin

82. Biology of Mites ( Sarcoptes scabiei ) Eggs are oval in shape

83. Biology of Mites ( Sarcoptes scabiei )  Eggs hatch in 3 to 4 days to release larvae.  The larvae migrate to the skin surface and burrow into the intact stratum corneum to construct molting pouches.  The larval stage has only 3 pairs of legs and lasts about 3 to 4 days.

84. Biology of Mites ( Sarcoptes scabiei )  After the larvae molt, the resulting nymphs have 4 pairs of legs.  This form molts into slightly larger nymphs before molting into adults.  Larvae and nymphs may often be found in molting pouches or in hair follicles.

85. Biology of Mites ( Sarcoptes scabiei )  Adults are round, sac-like eyeless mites.  Females are 0.30 to 0.45 mm long and 0.25 to 0.35 mm wide, and males are slightly more than half that size.  Mating occurs after the active male penetrates the molting pouch of the adult female.  Mating takes place only once and leaves the female fertile for the rest of her life.

86. Biology of Mites ( Sarcoptes scabiei )  Impregnated females leave their molting pouches to find out a suitable site for a permanent burrow.  On a suitable location, it begins to make its characteristic serpentine burrow, laying eggs in the process.  She remains there and continues to lengthen her burrow and lay eggs for the rest of her life (1-2 months).