Nematodes” are Round worms Most nematodes are free living in fresh water, sea water and soil. Are elongated bilaterally symmetrical, Non-segmented cylindrical worms, tapering at both the ends. Sexes are separate (diecious), male is smaller than female & its posterior end is curved ventrally. Females are either Viviparous (produces larvae/ embryo), Oviparous (lay egg) or ovo-viviparous (lays eggs which hatches immediately) Lives in intestinal tract or tissues.

1. NEMATODES

3. Cestodes(Tapeworms): Long, ribbon like
segments
Trematodes(flukes): flat, leaf shaped worm
Nematodes(Roundworm): elongate,
cylindrical, tapered at both the ends

4. NEMATODES (INTRODUCTION)
• “Nematodes” are Round worms
• Most nematodes are free living in fresh water, sea water and
soil.
• Are elongated bilaterally symmetrical, Non-segmented
cylindrical worms, tapering at both the ends.
• Sexes are separate (diecious), male is smaller than female &
its posterior end is curved ventrally.
• Females are either Viviparous (produces larvae/ embryo),
Oviparous (lay egg) or ovo-viviparous (lays eggs which hatches
immediately)
• Lives in intestinal tract or tissues.

5. Classification
•On the basis of location of adult worm:
• Small Intestine- Ascaris, Ancylostoma, Necator,
Trichinella, Strongyloides, Capillaria.
• Large Intestine- Trichuris, Enterobius.
• Somatic- Lymphatic system- Filaria (Woucheria
Bancroftii)
• Subcutaneous tissue- Loa, Onchocerca, Dracunculus
• Mesentry- D perstans, Mansonella
• Conjunctiva- Loa

6. Classification
•On the basis of Mode of transmission
• Ingestion- Ascaris, Trichuris, Enterobius, Dracunculus,
Trichinella
• Penetration- Ankylostoma, Necator, Strongyloides
• Vector borne- Filaria
•On Laying eggs/ larvae-
• Oviparous
• Viviparous- Trichinella, Filaria, Dracunculus
• Ovo viviparous- Strongyloides

7. Common human parasitic nematodes
Ascaris lumbricoides Enterobius vermicularis
Trichuris trichiura Hook worm
Dracunculus medinesis
Trichinella spiralis Filaria
Strongyloides stercolaris

8. Strongyloides stercoralis
Strongyloides stercoralis
Common Name Threadworm
Infective Stage Third Stage Filariform Larvae
Habitat duodenum and upper jejunum
Mode of Transmission Skin Penetration of Infective Larvae/ autoinfection

9. Nematodes: Rhabditida
Introduction
• Strongyloides stercolaris is a human roundworm,
commonly known as Threadworm.
• Inhabit small intestine mucosa (duodenum &
jejunum)
• Causing the disease Strogyloidiasis.
• It is soil transmitted infection (infective stage is
larva found in soil).
• The disease can also found in dogs and cats.

10. Morphology (the worm)
• Shape: Cylindrical
• Color: Pink-creamy-grey
• Size: very small
• Male: 0.7-1.0 mm long
• Female: 1.0- 2.7 mm long
• Habitat: mucosa of Small intestine.

12. Mode of transmission
• The most common way of becoming infected with Strongyloides is by
contacting soil that is contaminated with Strongyloides larvae(Flariform
larvae). Therefore, activities that increase contact with the soil increase the
risk of becoming infected, such as
• Walking with bare feet
• Contact with human waste or sewage
• Occupations that increase contact with contaminated soil such as farming
and coal mining
• Furthermore, many studies have shown an association
with Strongyloides and infection with Human T-Cell Lymphotropic Virus-1
(HTLV-1). These studies have shown that people infected with HTLV-1 are
more likely to become infected with Strongyloides, and that once infected,
are more likely to develop severe cases of strongyloidiasis

13. Complications
• Most people infected with Strongyloides do not know they are infected. If they do feel sick the
most common complaints are the following:
• Abdominal
• Stomachache, bloating, and heartburn
• Intermittent episodes of diarrhea and constipation
• Nausea and loss of appetite
• Respiratory
• Dry cough
• Throat irritation
• Skin
• An itchy, red rash that occurs where the worm entered the skin
• Recurrent raised red rash typically along the thighs and buttocks
• Rarely, severe life-threatening forms of the disease called hyperinfection syndrome and
disseminated strongyloidiasis can occur. These forms of the disease are more common in people
who are on corticosteroids or other immunosuppressive therapies or who are infected with HTLV-
1. In this situation, people become critically ill, and should be taken to the hospital immediately.

14. Lab diagnosis
• Strongyloides infection is best diagnosed with a blood test.
• Strongyloides infection may be diagnosed by seeing larvae in stool
(Rhabdtiform larvae) when examined under the microscope, but it
might not find the worms in all infected people. This may require
that you provide multiple stool samples to your doctor or the
laboratory

15. Prevention & Control
• The best way to prevent Strongyloides infection is to wear shoes when you are
walking on soil, and to avoid contact with fecal matter or sewage. Proper sewage
disposal and fecal management are keys to prevention.
• Furthermore, if you believe that you may be infected, the best way to prevent
severe disease is to be tested and, if found to be positive for disease, treated.
• You should discuss testing with your doctor if you are:
• Taking steroids or other immunosuppressive therapies
• About to start taking steroids or other immunosuppressive therapies
• A veteran who served in the South Pacific or Southeast Asia
• Infected with Human T-cell Lymphotropic Virus-1 (HTLV-1)
• Diagnosed with cancer
• Going to donate or receive organ transplants

16. Treatment
• Acute and chronic strongyloidiasis
• First line therapy
Ivermectin, in a single dose, 200 µg/kg orally for 1—2 days
• Relative contraindications include the following:
• Confirmed or suspected concomitant Loa loa infection
• Persons weighing less than 15kg
• Pregnant or lactating women
• Alternative
Albendazole, 400 mg orally two times a day for 7 days.