Nematodes and Ascaris lumbricoides

• Lecture six is about the Class Nematodes

Nematodes (Roundworms)

• From Greek: "nema, nematos = thread and ode = like"
• They are elongate, cylindrical, round or oval, tapering at both ends
• They are non-segmented, and have a well developed digestive tract
• Sexes are separate; males are shorter and slenderer than females
• Reproduction is usually sexual through the genital systems
• Female worms may lay eggs (oviparous), or give birth to larvae (larviparous or viviparous)
• Males have curved posterior ends, females have straight posterior ends
• Most nematodes are free-living in soil or water

Nematodes Classified by Habitat

• In the human body, nematodes are classified into intestinal nematodes and tissue nematodes

Intestinal Nematodes

• Have no intermediate host
• Ascaris lumbricoides
• Trichuris trichiura (L.I.)
• Enterobius vermicularis (L.I.)
• Hook worms
• Trichinella spiralis
• Strongyloides stercoralis

Tissue Nematodes

• Require an intermediate host; usually an arthropod

Lymphatic

• Wuchereria bancrofti
• Brugia malayi

Cutaneous

• Onchocerca volvulus
• loa loa
• Dracunculus medinensis

Nematode Molting

• Nematodes lay down a new cuticle periodically and shed the old one

Intestinal Nematodes: Ascaris lumbricoides (Giant Intestinal Roundworm)

• It is the largest of the common nematodes in human infections
• Adult worms are pink or yellow-white when fresh
• The are cylindrical with tapering ends
• They have 3 fleshy lips, and each lip has two minute sensory papillae
• They have club-shaped esophagi
• Males are about 20 cm long and have ventrally curved posterior ends
• Females are about 25 cm long and have straight posterior ends

Ascaris lumbricoides Life Cycle

• After ingestion of infective eggs, they hatch in the small intestine
• Liberated rhabditiform larvae penetrate the intestinal wall and enter the circulatory system to the right side of heart then to the lung
• In the lung, the larvae remain for about 10 days, moulting twice, then break into the alveoli to the bronchioles, bronchi, trachea and epiglottis
• The larvae are swallowed and passed again to the small intestine
• In the small intestine, they moult for the fourth time and develop into mature worms
• Mating occurs and immature eggs pass in feces about 3 months after infection
• In suitable environmental conditions (shady soil, suitable temperature and humidity), rhabditiform larvae develop and moult for the first time inside the egg shells

Ascaris lumbricoides additional Info

• Auto infection is uncommon
• Ascariasis is the disease it causes
• It has a worldwide distribution
• Children are more frequently infected than adults
• The definitive host: Man
• Reservoir: None
• Intermediate host: None
• Habitat: Small Intestine
• Diagnostic stage: Fertilized and unfertilized eggs are passed in feces of infected person, larva and adult worm
• Infective stage: Larvated egg (Embryonated egg w. 2nd rahbditiform larva)
• Mode of infection: Ingestion of embryonated eggs in food, drink or contaminated hands
• Transplacental migration into a developing fetus is known

Ascaris lumbricoides Clinical Picture

• Migration: Loeffler's Syndrome may occur
• Intestinal symptoms: Nausea, vomiting, colic, dyspepsia, diarrhea or constipation may occur
• Complications: Traumatic Intestinal obstruction, toxic effects, antienzymes, and toxins may occur

Ascaris lumbricoides Pathogenicity

• A light infection is usually asymptomatic

Migration Phase (Pulmonary Phase)

• Larval migration through the lungs may cause Loeffler's syndrome due to minute hemorrhages and eosinophilic infiltration.
• Symptoms may include fever, cough with blood stained sputum and allergic manifestation (asthma and edema)

Intestinal Phase

• Toxic effects: By product of living or dead worms produce allergic manifestation, nervous irritability, anorexia, loss of weight and dyspepsia.
• Worms produce a trypsin-inhibiting substance which interferes with protein digestion.
• Digestive disorders as nausea, vomiting diarrhea and abdominal discomfort may occur.

Traumatic Effect (Phase of Complication)

• During migration many worms get lost and accumulate in almost every organ of the body causing acute tissue reaction
• When bacterial infections become superimposed death can result before the disease is diagnosed
• Heavy infection results in intestinal obstruction, perforation and peritonitis

Ascaris lumbricoides Diagnosis

• History: child playing in soil + Loeffler
• Clinical symptoms: vague abdominal symptoms after transient cough and dyspnea
• CBC to test for eosinophilia
• Parasitological examination of eggs in the stool
• Adults in vomitus, feces or intestinal obstruction
• Larvae in sputum + Blood + Eosinophils
• Serology: Loeffler IHAT IFAT
• Radiology: X-ray
• Barium meal

Ascaris lumbricoides Prevention and Control

• Avoiding eating insufficiently cooked or washed food
• Treating infected cases to reduce egg output
• Improve hygienic habits (particularly in children).
• Sanitary disposal of excreta
• Health education about the hazards and mode of infection of the parasite

Ascaris lumbricoides Treatment

• Mebendazole
• Albendazole: Single dose
• In mixed infections, treat Ascaris first

Enterobius vermicularis (Pinworm, Threadworm, or Oxyuris)

• Affects humans and children especially
• Adult worms are whitish with dorsoventral cuticular expansions at the anterior end
• Have double bulbed esophagi
• Males: ~4 mm long with ventrally curved posterior ends
• Females: ~1 cm long with straight posterior ends
• Eggs have a Oval-shape, asymmetrical with flattened one side and convexed the other side
• Shell: Thick, Translucent, containing a Infective larva

Enterobius vermicularis Infection

• Also called Oxiuris, Pinworm, Seatworm
• It is The commonest nematode and is Biphasic
• E. vermicularis Life Cycle
• After ingestion of the infective eggs, they hatch in the small intestine
• Liberated rhabditiform larvae develop into mature worms on reaching the large intestine
• In the large intestine, mating occurs, the males usually die, gravid females migrate to the rectum, pass out of the anus and:
• Lay their eggs on the perianal skin about one month after infection
• The eggs are fulled-embryonated and infective within a few hours

Pinworm Infection

• Causes :
• Enterobiasis
• Oxyuriasis
• Thread worm

Pinworm Host

• Definitive: Man
• Reservoir: None.
• Intermediate: None.
• Habitat: Large intestinee especially caecum and appendix.
• Both diagnostic and infective stage : Enterobius eggs.

Pinworm Mode of Infection

• Ingestion of eggs in food, drink or from contaminated hands
• External autoinfection by hand mouth infection
• Retroinfection when the eggs on the perianal skin hatch and the liberated larvae migrate back into the large intestine through the anus
• Inhalation of air-born eggs can also occur

E. vermicularis Additional Info

• Worldwide Distribution
• Commonly in children
• When laid are larvated and are immediately infective

E. vermicularis Clinical Picture

• Irritation and pruritus ani at night (Nocturnal periodicity)
• Scratching may cause dermatitis and secondary bacterial infection
• Can cause nervous irritability, restlessness and insomnia
• Can cause nausea, vomiting, colic diarrehea alternating with constipation
• Also appendicitis.
• In female patients, worms may migrate to vagina, uterus, bladder and urethra: causing irritation and inflammation

E. vermicularis Diagnosis

• Recovery of adult worms from anus at night or on the stool
• Eggs are best obtained by swabbing the perianal region by:
• NIH Swab
• Scotch adhesive tape swab
• Eggs may be recovered from urine in female patients

E. vermicularis Treatment

• Albendazole or Mebendazole
• Repeated after 2 weeks (Autoinfection & Hyperinfection)
• Treat All Family

E. vermicularis Prevention and Control

• Personal cleanliness
• Mass treatment
• The treatment should be for all members of the household

Trichuris Trichiura (Whip Worm)

• Adult worm is whip-like in shape
• It has thin anterior parts (about 60% of the body length)
• Thick posterior part (40% of body length)
• Male worms have a coiled posterior end
• Female worms have a straight end
• Eggs are barrel-shaped with polar plugs
• Thick Shell
• Have Yellowish – brown Color
• Contains unsegmented ovum cellular esophagus (unicellular glands surrounding esophageal tube )

T. trichiura (Whip Worm) Transmission

• The anterior part embeds and has subsequent formation of;
• An Embryonated egg with 1stage Rhabditifom larva and Cecum Anterior part in humans

T. trichiura Whip Form Life Cycle

• After ingestion of the embryonated eggs, they hatch, penetrating the intestinal villi and staying for about 1 week as development of:
• Mature worms, with mating and eggs passing in feces after 3months

T. trichiura Whip Form additional info

• embryotic period takes 3 weeks
• Embryonic first stgae Larvae are produced inside the egg shells
• Worldwide distribution: are often infecting childeren more then adults
• Large intestine Host
• Imature eggs from Definitive Hosts are diagnostic
• Laraved EGGS are infectous

T. trichiura diseases from infection

• *Trichuriasis
• *Whipworm infection

T. trichiura Pathogensis

• Depends on Intesity and duration of infection

Light Infection

• asymptomatic

Moderate Infection

• abdominal pain
• anorexia
• diaherra

Heavy Infection

• Anemia
• Intestinal perfuration Acute appendicitis

T. trichiura Diagnosis

• Finding the eggs in the faces
• Prevention and control as ascariasis

Hook Form Morpholgical Characters

• Greyish white, Large bucal capsule with 2 ventral teetjh and dorsal plate
• Oval shape with clear space

Hook Form Life cycle

• Enter through skin to heat to long
• Larvae break into alveoli through bronchi trachea and into small instetine to mature after 2 moult
• Females deposit eggs which come out via infection

Hook Form Transmissions

• Small instetine after 2 moults on small insteine

Ancylostoma Duodenale (Hook Worm)

• Small Intestine worm that has the Infective Stage Filariform larva and can form a Disease: Ancylostomiasis
• Can be transmitted worldwide and is espically in tropical and subtropical areas
• Has Definitve Mans Host which Penetration of filariform larvae through skin or mucous membranes

Ancylostoma Duodenale (Hook Worm) Symptoms

• Intermittent diaherra espeically in childteren
• Nausea Vomiting with blood stools
• Eating soil and iron deficiency

Ancylostoma Duodenale (Hook Worm) Pathogensis

• Loeffler Continuous Blood loss via antioagulant infection and eating a tenth of an ml of blood
• Pallore swelling weaknws retartdation

Ancylostoma Duodenale (Hook Worm) Diagnosis

• clinical picture in an endemic area. • CBC: Eosinophilia +anemia
• Finding eggs and finding larva in specimens
• Mebendozole or Albendozle
• Iron as treatemtn

Strongyloides Stercoralis Morphology

Rhabditoide sphagous

• Male only milimeter
• Ventricle Cylindrical Straigh short pointed tail
• Thin Oval shapw with transparent shell

Strongyloides steroraclis infections

• *Parasitic Form
• *Free Living for

Strongyloides sterorcalis transmissions

• Enter the membrane
• Interal infection and autoingection via skin

Strongyloides sterorcalis cycle

• has a sexual and asexual lifcycle

Strongyloides sterorcalis Pathognesis

• Filariform larvae transmitted world wide in tropical ares in small intestines
• Infections stage Filariform
• has a Man definitive to the lack of role on treansmission

Symptoms of Strongyloides sterorcalis

• Water blood diahrea plus epastric paine with high ocbc count
• Loefflers syndrome
• Dissemated and opportuintiis

Strongyloides sterorcalis treatmetsn

• Ivermacitn
• Thiabenezole