Parasitology Lecture Notes PDF

Parasitology First-Semester Lecture: 2 Dr. Azhar B-9& A-10/ 10/2022 Parasitic Helminthes (Page number1-11) Objectives of this...

Parasitology First-Semester Lecture: 2 Dr. Azhar B-9& A-10/ 10/2022 Parasitic Helminthes (Page number1-11) Objectives of this lecture: rd At the end of this lecture the 3 year student is able to: 1. List the classes of Helminthes. 2. Define the nematodes as group. 3. Describe the main nematodes characteristics features. 4. Determine how nematodes can be classified in various ways. 5. List the mode of infections can nematodes used. 6. Apply some terms associated with nematodes. 7. Describe & define the most famous nematode????? 50 species parasitize billions of humans - Transmission routes: acquired though… – ingestion of larvae or eggs in food. – from soil or water (ingestion or penetrate skin). – some are carried by insect vectors. X Most intestinal helminthes identified by stool examination. Parasitic Helminthes: are - Trematodes (flukes) – Venous system: Schistosoma – Biliary tract: Clonorchis, Fasciola – Lung: Paragonimus - Cestodes (tapeworms) – Taenia saginata, Taenia solium, H. nana Nematodes (roundworm) – Intestinal – Blood, lymphatic, subcutaneous 1  Introduction to Nematodes - Scientific classification Kingdom:Animalia Phylum: Nematoda =iscan The nematodes or roundworms (from Greek name: nemat "thread" + -ode "like") _ _ are one of the most common phyla of animals. - Textbook: p 127-170. Phylum Nematoda: female >> Male The nematodes are quite species diverse (about 10,000 species) and the many parasitic forms have a significant impact on humans. Most nematodes are under 5 cm. and- & - many are microscopic. However, some parasitic forms can be over a meter in length. ( Maybe short 00 05 a S or long ) Nematodes live in the soil, freshwater, marine, sands and mud. Other nematodes are parasites of almost every species of animal, including humans, and plant. They are also known as ‘eelworms’ and ‘roundworms’. Nematodes are typically worm-like, except they are unsegmented. Essentially the Shape : - body form is similar to a flexible cylinder with a rounded head and a pointed tail. - 53 & They have active movement, which is an i undulating motion similar to that of an eel. in - In humans, some 30 species of nematodes are of medical importance and are ☒ edema in the limbs responsible for diseases such as elephantiasis, river blindness, the intestinal - roundworm (Ascaris), the pin worm (Enterobius) and the hookworms. - - - Some species of nematodes, called entomopathogenic nematodes, can be used for 2 biological control of insects. They invade insect and release bacteria, which kill the insect and enable the nematode to feed on the proliferating bacteria. Nematodes as a group: secretion beatria to kill insect  Multicellular (metazoa). -  Unsegmented. -  Elongate & cylindrical with bilateral symmetry.  Contain complete digestive tract.  Body cavity: pseudocele, not lined with mesothelium. nee 2   They are dioecious or bisexual. Males are usually smaller than females and often have a characteristically bent tail for holding the female for copulation. - > - In few, the females may be parthenogenetic. * female don't need male -  They range in size from minute to many centimeters in length.  The body wall consists of an outer cuticula (may be with scales or spines), an = responsible inner muscular layer & an intermediate thin syncytial hypodermis. > - for secreting + maintaing outer cutical complex O O  Contain specialized structures at the anterior end for attachment, penetration & & sensory purposes.  Have excretory system.  Have nervous system. & ②  Have sense organs. Requires 1 host except filarial worms and Dracunculus (2 host).  Have reproductive organs. -6% %  Nematodes may produce eggs (oviparous) or larvae (viviparous or larviparous), others lay eggs containing larvae which immediately hatch out -ado (ovoviviparous). egg ↳ ¥. pie. Hypodermis 0 3 Nematode parasites may be classified in various ways: t.MU 1. Location of adult in the body: ¥ " 2. Mode of infection: = By ingestion of: - :  Eggs: Ascaris, Enterobius. Trichuris  Larvae within intermediate host: Dracunculus  Encysted larvae in muscle: Trichinella By penetration of skin: Ancylostoma, Necator, Strongyloides a- Mm By blood-sucking insects (Insects bite): Filariae - By inhalation of dust containing eggs: Enterobius 3. Based on whether they lay eggs or larvae:  Oviparous- laying eggs: - unsegmented eggs: Ascaris & Trichuris. - segmented eggs: Ancylostoma & Necator. - eggs containing larvae: Enterobius.  Viviparous- producing larvae: Trichinella, Wuchereria, Brugia & Dracunculus.  Ovoviviparous: laying eggs containing fully formed larvae which hatch out immediately: Strongyloides. 4 4. Zoological classification (table to see only): for information : - 5  Terms Used in Relation to Nematodes ⑮ 1 Autoinfection Self infection with the parasite Maybe one parasite become 2 Retroinfection A form of autoinfection in which the larvae hatch ÷ out near the anus and migrate back into the large intestines to develop into adults d' anus # EÉÑ÷ intestines 2€ ↳→ Rhabditiform Larva with a short esophagus, which has a bulb at its 3 - Larva anterior end; feeding form Filariform Larva with an elongated esophagus, which does not Larva have a bulb at its anterior end; not feeding infective form Paratenic 5 - host A transport host in which the particular parasitic stage does not grow, but remains viable d → Parasite I-j.CI#j 6- Periodicity Term used to denote the presence or absence of & microfilariae in blood did j1441 , - 7- Nocturnal When microfilariae show pronounced peak periodicity during night time. The rest of the period they are absent or scanty. Diurnal When microfilariae show pronounced peak : periodicity during daytime. The rest of the period they are absent or scanty. Subperiodicity When microfilariae are present in appreciable numbers throughout the 24 hour period ✓ in night , daytimer 6 General life cycle of Nematodes Adult Egg Tim) ♂+♀ - i L4 L1 - dis I egg L3 L2 Mont ro changes Nematodes generally undergo 4 moults during their life. An external stimulus = apparently triggers a response which leads to production of enzymes which initiate moulting. – The first moult and occasionally the second moult may take place in the egg. = - – The remaining moults occur in the definitive host. Enterobius vermicularis (Oxyuris vermicularis) (Pinworm): - s '>  Known as the human pin worm of temperate climate zones. Most common es) anywhere poor hygiene is practiced.  Host: humans are the only normal host of E. vermicularis other species infect goats, sheep, horses, rabbits and others.  No intermediate host (direct life cycle).  Disease: Enterobiasis or oxyuriasis (old name).  Enterobiasis is the commonest helminthes. infect soo million cases annually  It is an urban disease of children in temperate zones & in crowded environment (schools, asylums, day care centers, etc.). "54 effect just human 7   Adults may get it from their children. -y  Cosmopolitan, 30%~50% of the population. - Morphology:  Adult has 3 lips & the anterior end bears dorsal & ventral bladder-like inflation. [  ♂ smaller than ♀, measured 5×0.1-0.2 mm. The posterior end strongly curved to the ventral side with one spicule (forms an inverted question mark ¿). female [ ♀ larger than ♂, measured 13×0.3-0.5 mm. The posterior end sharply pointed. &  Eggs (60 x 27 µm) are ovoid but asymmetrically flat on one side (D-shaped) = - & with double shell, the outer one albuminous that causes them to stick to each · other & to clothing or other objects. Place Habitat of adult is the lumen of large intestine (cecum & appendix). - @  Gravid ♀ migrate down the bowel to the rectum during host's sleep or I relaxation, they crawl out of the anus onto the perianal skin to lay eggs which immature & become mature within a few hours(6 hrs) & contain a fully developed infective stage (egg with L1).  Scratching transfers eggs to the fingers, in the dirt beneath the nails. These are → carried to the patient's own mouth (autoinfection). ( The life cycle: ) Dave the life cycle Infection occurs when embryonated eggs are ingested from the environment, with ÷ - food or by hand to mouth contact. The embryonic larvae hatch in the duodenum and Ii reach adolescence in jejunum and upper ileum. Adult worms descend into lower ileum, cecum and colon and live there for 7 to 8 weeks. The gravid females, containing more than 10,000 eggs migrate, at night, to the perianal region and deposit their eggs there. Eggs mature in an oxygenated, moist environment and are infectious 3 to 6 hours later. Man-to-man and auto infection are common. Man is the only host. 8  life cycle -draw i Eggs are deposited on perianal folds (1). Self-infection occurs by transferring infective eggs to the mouth with hands that have scratched the perianal area (2). Person-to-person transmission can also occur through handling of contaminated clothes or bed linens. Enterobiasis may also be acquired through surfaces in the environment that are - > W contaminated with pinworm eggs (e.g., curtains, carpeting). Some small number of eggs may become airborne and inhaled. These would be swallowed and follow the same development as ingested eggs. Following- ingestion of infective eggs, the larvae hatch in the small intestine (3) and the adults establish themselves in the colon (4). The time - interval from ingestion of infective eggs to oviposition by the adult females is about one month. The life span of the adults is about two months. Gravid females migrate nocturnally outside the anus and oviposit while crawling on the skin of the perianal area (5). The larvae contained inside the eggs develop (the eggs become infective) in 3 to 6 hours under optimal conditions (1). Retroinfection, or the migration of newly hatched larvae from the anal skin back into the rectum, may occur but the frequency with which this happens is unknown. Note:  The life cycle complete in about 1 month or less. -  Man-to-man and auto infection are common.  Man is the only host. fwm →← * → is retro infection Auto infection )  Site of inhabitation (adult): cecum and colon.  Infective stage: embryonated egg.  Without intermediate host and reservoir host (direct life cycle). - 9  age  The life span of the pinworm is less than two months, but retro-infection is very = common.  Autoinfection: Female crawl out of anus and release eggs on the perianal region. Patients feel anus pruritus. Scratching leads to contamination of hands and nails, then by hand-mouth result in reinfection. IN.-W≥ E- %  Retro-infection: Some eggs hatch on the perianal skin and become larvae. They will crawl back into the anus and mature into adults. Mode of transmitting:  Ingestion ) ( absorption  Inhalation (air-borne). Pathogenesis: The infection is most common in children. & Enterobiasis is relatively innocuous and rarely produces serious lesions. About one-third of pinworm-infected persons are asymptomatic. The - adult worms may cause slight irritation of the intestinal mucosa. Major symptom is anal pruritus, which associates with the nocturnal migration # of the gravid females from the anus and deposition of eggs in the perianal folds of the skin. Itching scratching+ irritation with scarification weep eczema of the perianal region. Restless sleep and insomnia. Tiredness during the daytime. Loss of appetite and abdominal pain. } May cause appendicitis. { Rare migration & disintegration of female worms into urogenital tract of female, & encapsulated within uterus or fallopian tube with lesions in abdominal cavity via oviducts may cause vaginitis. a- = No tissue invasion. = No apparently toxic by-product production. 10 Diagnosis: Diagnosis is made by finding eggs in the perianal area by a specific technique cellophane tape or Scotch tape technique or NIH swab (national institutes of health). The cellophane is now usually replaced with sticky tape. This must be done in the morning, before defecation and washing. Diagnostic stage: Eggs in the perianal area (egg with L1 or emberyonated egg). Treatment:  Mebendazole, piperazine or pyrvinium.  The whole family should be treated at the same time, to avoid re-infection.  Treatment should be repeated after about 2 weeks.  Bedding and underclothing must be sanitized. - im Control: Personal & family hygiene. % Mass chemotherapy. Repeated treatment may be necessary for a radical cure. Health education and hygienic habits. & Laundering of bedding. Note: Nematodes not showing systemic migration in man Enterobius vermicularis { Trichuris trichiura } End of the lecture-2 11