INSTITUTE OF PULIC HEALTH, DHAKADepartment of Laboratory Medicine

BSc in Health Technology (Laboratory)- 1st Year

HELMINTHOLOGYLecture No. 02(Ascaris lumbricoides)

By

Sk. MIZANUR RAHMANAssistant Bacteriologist, MBL, IPH

MS in Biotechnology & Genetic Engineering (UODA)MS in Microbiology (SU)

MPH in Epidemiology (SUB)

INTRODUCTION

• Ascaris lumbricoides is the largest nematode (roundworm) parasitizing the human intestine.

• Ascaris lumbricoides is an intestinal worm found in the small intestine of man.

• They are more common in children then in adult.

• As many as 500 to 5000 adult worms may inhabit a single host.

Common name:- Giant Intestinal round worms.

Disease:-Ascariaisis

Host :- The human is intermediate and final host.

Location in Definitive host :-

the adult worm: in small intestines .

larva: in lung .

Infective stage :- Ovum

Female Characteristics

200 –350 mm X 4- 6 mm

Ivory mixed light red

Straight

Absent

Absent

1.Size

2.Color

3.Posterior end

4. Spicules

5.Papillae

Ascaris Lumbricoides female

Male Characteristics

150 – 200 X 2 -4 mm

Reddish pink

Curved

Has two spicules

Has many from papillae

1.Size

2.Color

3.Posterior end

4. Spicules

5.Papillae

Ascaris Lumbricoidesmale

Geography• Worldwide• High prevalence in underdeveloped countries

that have poor sanitation (parts of Asia, South America and Africa)

• Occurs during rainy months, tropical and subtropical countries

• Even occurs in rural areas in the United States

MORPHOLOGY• It is a elongated, cylindrical and

tapering at both ends. • Sexes are separate• The female is longer than male

20 – 35 cm long, 4-6 mm in diameter.

• Male is smaller being 15-30 cm long, 2-4 mm in diameter.

• The posterior end of male is curved having penial setae near the end.

The Mouth Parts • The mouth opens at the anterior end.• It is surrounded by three finely toothed

lips.• The lips are one dorsal and two

ventrolateral.• These lips bear sensory structures called

labial papillae• The dorsal lip has two double sensory

papillae and ventrolateral lip has one double sensory papilla.

• The ventrolateral lip also bear amphidial gland which is olfactory and chemoreceptor

Round worms

Some cool pictures

LIFE CYCLE

LIFE CYCLE cont……

1. Site of inhabitation: small intestine 2. Infetive stage: embryonated eggs 3. Route of infection: by mouth 4. No intermediate and reservoir hosts 5. Life span of the adult: about 1 year

• Adult worms live in the lumen of the small intestine. A female may produce approximately 200,000 eggs per day, which are passed with the faeces .

• Unfertilized eggs may be ingested but are not infective. Fertile eggs embryonate and become infective after 18 days to several weeks.

• After infective eggs are swallowed , the larvae hatch , invade the intestinal mucosa.

• Carried via the portal, then systemic circulation to the lungs. larvae mature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed.

• 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. Adult worms can live 1 to 2 years.

LIFE CYCLE cont…..

Rhabditiform larvae

Egg hatch------3rd stage larva --- hepatic portal vessels to liver (3-4 days) ------ Hepatic vein ------ Post caval vein ----- Heart --- Lungs (7days-3rd moulting) ---Larynx --- oesophagus --- Stomach (4th moulting)

Modes of transmission Occurs mainly by ingestion of contaminated

food or water with eggs. Occasionally by inhalation of contaminated dust

with eggs. Children playing in contaminated soil may

acquire the parasite from their hands.

INFECTION TO MAN• It occurs when the man swallows the infective

eggs of Ascaris with contaminated food or water.

Pathogenesis There are two phase in ascariasis: 1. The blood-lung migration phase of the larvae:

During the migration through the lungs, the larvae may cause a pneumonia. The symptoms of the pneumonia are low fever, cough, blood-tinged sputum, asthma. Large numbers of worms may give rise to allergic symptoms. Eosionophilia is generally present. These clinical manifestation is also called Loeffler’s syndrome.

2. The intestinal phase of the adults. The presence of a few adult worms in the lumen of the small intestine usually produces no symptoms, but may give rise to vague abdominal pains or intermittent colic, especially in children. A heavy worm burden can result in malnutrition. More serious manifestations have been observed. Wandering adults may block the appendical lumen or the common bile duct and even perforate the intestinal wall. Thus complications of ascariasis, such as intestinal obstruction, appendicitis, biliary ascariasis, perforation of the intestine, cholecystitis, pancreatitis and peritonitis, etc., may occur, in which biliary ascariasis is the most common complication.

Symptoms of Ascariasis• No symptoms • Stage 1: worm larvae in the bowels attach to bowel walls • Stage 2: worm larvae migrate into the lungs: • Fever and breathing difficulty• Coughing and pneumonia • Stage 3: worms enter the small intestine and mature into worms

and remain there to feed • Abdominal symptoms • Abdominal discomfort • Intestinal blockage - may be partial or complete • Partial intestinal blockage • Total intestinal blockage • Severe abdominal pain • Vomiting • Restlessness • Disturbed sleep • Worm in stool • Worm in vomit

CLINICAL FEATURES• Abdominal pain, diarrhoea, vomiting and

slight temperature.• It blocks intestine and appendix.• They may enter bile or pancreatic duct

and interfere with digestion.• Injure the intestine and cause peritonitis.• They produce toxins which irritate the

mucous membrane of the gut, or prevent digestion of protein by host by destroying an enzyme trypsin.

• In children they cause stunted growth and makes the mental capacity dull.

• Larvae causes inflammation and haemorrhage in the lungs which results in pneumonia – may prove fatal.

DiagnosisThe diagnosis depends on the Identify worm or egg:-

The Stool examination : for seeing the adult worm or

egg .

The sputum examination :for seeing larva during

migration in the lung.

Eosinophilia as indicator on parasitic infection .

Diagnosis• The symptoms and signs are for reference only. The

confirmative diagnosis depends on the recovery and identification of the worm or its egg.

1. Ascaris pneumonitis: examination of sputum for Ascaris larvae is sometimes successful.

2. Intestinal ascariasis: feces are examined for the ascaris eggs.

(1) direct fecal film: it is simple and effective. The eggs are easily found using this way due to a large number of the female oviposition, approximately 240,000 eggs per worm per day. So this method is the first choice.

(2) brine-floatation method: (3) recovery of adult worms: when adults or

adolescents are found in feces or vomit and tissues and organs from the human infected with ascarids , the diagnosis may be defined.

The EggsEggs

FertilizedUnfertilized

DecorticatedCorticated

Fertilized egg( corticated egg)

1.Size:- 45-75 mm by 35-50 mm.

2.Shape:-Rounded or oval

3. Shell:-Thick,consisting of 3 layers : (Inner layer ) consist of

thin yolk Membrane ,(Mid layer) thick ,(Outer

layer ) coarse consist of regular Albuminous,There is

crescent shaped clear space at the each end inside the

shell.

4.Colour:-Golden brown.

( outer layer) coarse

( regular Albuminous )

(Inner layer)

the thin yolk membrane

( mid layer) thick

Embryo

Crescent space

Decorticated Egg fertilized eggs sometimes

may lack the outer albuminous layer and are colorless.

Unfertilized eggs : elongated and larger than fertile egg

1.Size:- 85-95 mm by 43-47 mm.

2.Shape:- Elongated oval

3.Shell:-Thin ,not has inner layer , irregular

albuminous layer , not has Crescent space.

PREVENTION• Keeping good sanitation conditions is the only way to prevent

the infection of Ascaris.• Pollution of soil with human faeces should be avoided.• Vegetable should be thoroughly washed in a mild solution of

Pottasium permanganate and properly cooked before use.• Finger nails should be regularly cut to avoid the collection of

dirt and eggs below them.• Hands should be properly washed with some antiseptic soap

before touching edibles or eating.