Nematodes -onchocerca volvulus slides

1. TISSUEANDBLOOD DWELLINGNEMATODES
-FILARIALWORMS
Onchocerca volvulus

2. Nematodes
1. INTESTINAL NEMATODES WITH TISSUE STAGES
 Ascaris lumbricoides (Giant Roundworm; Common Roundworm)
 Strongyloides stercoralis
 HOOK WORMS:-
 Ancylostoma duodenale
Cutaneous Larva Migrans
 Ancylostoma braziliense
 Ancylostoma caninum
 Necator americanus
2. INTESTINAL NEMATODES WITHOUT TISSUE STAGES
 Enterobius vermicularis (Pin Worm or Thread Worm)
 Trichuris trichuira (Whip Worm)
3. TISSUE AND BLOOD DWELLING NEMATODES
 Toxocara species (Toxocara canis; Toxocara cati)
- Visceral Larva Migrans
 Trichinella spiralis
 Dracunculus medinensis
 FILARIAL WORMS:-
 Wuchereria bancrofti
 Onchocerca volvulus
 Loa loa (The Eye Worm)
 Mansonella species

3. Zoological Classication of Nematodes
ORDER SUPER FAMILY FAMILY GENERA SPECIE
Enoplida Trichinelloidea Trichinellidae Trichinella T. spiralis
Trichuridae Trichuris T. trichiura
Rhabditida Rhabditoidea Strongyloididae Strongyloides S. stercoralis
Strongylida Ancylostomatoidea Ancylostomatidae Ancylostoma A. duodenale
Metastrongyloidea Angiostrongylidae Necator N. americanus
Ascaridida Ascaridoidea Ascarididae Ascaris A. lumbricoides
Oxyurida Oxyuroidea Oxyuridae Enterobius E. vermicularis
Spirurida Filarioidea Onchocercidae Wuchereria W. bancrofti
Loa L. Ioa
Mansonella M. perstans
M. ozzardi
M. streptocerca
Onchocerca O. volvulus
Dracunculoidea Dracunculidae Dracunculus D. medinensis

4. Onchocercavolvulus
Prevalence and Geographical distribution
 Onchocerciasis (River Blindness) - Eye and Skin Disease
 120 million people world-wide are at risk of Onchocerciasis
 96% are in Africa
 Of the 36 countries where the disease is endemic
30 are in Sub-Sahara Africa (plus Yemen)
6 are in the Americas
 18 million people are infected with the disease and have dermal
microfilariae
99% are in Africa
Over 6.5 million suffer from severe itching or dermatitis
270, 000 are blind

5. Loaloa -PrevalenceandGeographicaldistribution

6. ParasiteMorphology
Morphologies:
• Adult worms are coiled within a fibrous tissue capsules (nodules)
• Male: only about 5 cm long
• Female: 30 - 50 cm long
• Microfilariae:
Unsheathed
150 – 350 μm long; & a pointed tail tip with NO nuclei
Several Nuclei through-out the body
Have a Diurnal Periodicity
• Intermediate Host and Vector:-
Female Simulium damnosum (Black Fly), found around Plantations;
Rivers or River Basins

7. Filarial WormsSpecies/MicrofilariaeDifferentiations

8. Onchocercavolvulus-Microfilariae

9. Simulium damnosum

11. LifeCycle
 A Female Blackfly introduces 3rd Stage Filarial Larvae during it’s blood meal
to a human host
 In subcutaneous tissues the Larvae develops into Adult Filariae (3 months to
1 year)
 commonly reside in nodules in subcutaneous connective tissues
 In the Subcutaneous Nodules, the female worms produces Microfilariae
(thousands of new larvae daily)
 The Microfilariae are typically found in the Skin and in the Lymphatics of
connective tissues
 occasionally found in peripheral blood, urine, and sputum
 The larvae become detectable in the skin 10 - 20 months after the initial
infection
 A blackfly ingests the circulating Microfilariae during a blood meal
 After ingestion, the Microfilariae migrate from the Blackfly's Midgut
through the hemocoele to the Thoracic muscles
 In Thoracic Muscles the Microfilariae develops into 1st Stage Larvae; 2nd
Stage Larvae; 3rd Stage Larvae (Infective Stage), 10 - 12 days
 The 3rd Stage Larvae migrate to the Blackfly's Proboscis in readiness for
infection
Adults can live in the nodules for approximately 15 years

12. LifeCycle

13. FILARIALWORMS -CHARACTERISTICS
PARASITE
ADULTS
LOCATION
MICROFILARIA
LOCATION
MICROFILARIA CHARACTERISTICS
MICROFILARIA
PERIODICITY
Lymphatic Filariasis
Wuchereria
bancrofti
lymphatics Blood
Sheathed, pointed tall tip free
of nuclei
Nocturnal
Brugia malayi lymphatics Blood
Sheathed, blunt tail tip with 2
terminal nuclei
Nocturnal
Brugia timori lymphatics Blood Sheathed Nocturnal
Subcutaneous Filariasis
Loa loa
Connective
tissue,
conjunctiva
Blood
Sheathed, nuclei extending up
to pointed tail tip
Diurnal
Onchocerca
volvulus
Subcutaneous
nodules
Skin, eyes
Unsheathed, blunt tail tip free
of nuclei
Non periodic
Mansonella
streptocerca
Subcutaneous Skin
Unsheathed blunt tail tip
with nuclei
Non periodic
Serous Cavity Filariasis
Mansonella
ozzardi
Peritoneum and
pleura
Blood
Unsheathed, pointed tail tip
without nuclei
Non periodic
Mansonella
perstans
Peritoneum and
pleura
Blood
Unsheathed, pointed tail tip
with nuclei
Non periodic

14. RiverBlindness(Onchocerciasis):ClinicalFeatures
The symptoms are primarily caused by Microfilariae that move around the
human body in the subcutaneous tissue or those that die and the body’s
intense immunological response:-
1. Onchocerciasis - Skin disease
 Pruritus
 Acute skin inflammation
 Onchodermatitis
 Skin hypo- or hyper- pigmentation (due to antigenic material from dead
Microfilaria)
 Hyperpigmented skin changes termed as Sowda (usually limited to one limb)
 Onchocercomata – Several skin fibrous nodules (1 -5 cm) enclosing Adult
worms as a host-parasite reaction
 The skin becomes thickened and wrinkled, showing “lizard” or "leopard skin"
appearance
 Elephantiasis of the external genitalia; hanging groin
2. Onchocerciasis - Eye disease
 Reversible lesions on the cornea
 Permanent clouding of the cornea and Blindness
 Inflammation/Atrophy of the Optic Nerve resulting in Vision Loss and
eventually Blindness

15. Onchocerciasis - The Skin Disease
(Thickened/Wrinkled Skin; Onchodermatitis)

16. Onchocerciasis-Skindisease
(SkinNodules& Sowda)

19. Onchocerciasis - TheEye Disease

20. LaboratoryDiagnosis
Skin Onchocerciasis
 The most common method - The skin snip:-
 A 1- 2 mg shaving or biopsy of the skin is done to identify larvae
 In patients with nodules in the skin :-
Surgical removal and examination for adult worms
 Polymerase chain reaction (PCR) of the skin can allow for diagnosis if
the larvae are not visualized
Eye Onchocerciasis
 Slit-lamp examination of the anterior part of the eye

21. Treatment
 WHO recommends treating Onchocerciasis with Ivermectin every 6
months or once yearly for about 10 to 15 years
Because it kills Microfilariae but not adult worms
Exerts Microfilaricidal effects slowly – less severe side effects
 Doxycycline kills the adult worms
kills Wolbachia bacteria on which the adult worms depend in order to
survive
 Diethylcarbamazine (DEC) is the alternative drug
kills the Microfilariae and Adult worms
Very rapid onset of it’s action
Should be used with care!
 The most common side effects are dizziness, nausea, fever, headache, or pain
in muscles/joints

22. PreventionandControl
1. Targeting Vector control and elimination
 The Onchocerciasis Control Programme (OCP) launched in 1974 in West
Africa
The programme has been jointly sponsored by WHO, the World Bank,
UNDP, FAO and more than 20 donor countries and agencies
 OCP's principal method for controlling Onchocerciasis:-
Breaking the cycle of transmission by eliminating the black fly
Simulium larvae are destroyed by application of selected Insecticides
through aerial spraying of Breeding sites in fast-flowing rivers
 Once the cycle of river blindness has been interrupted for 14 years the
reservoir of Adult worms dies out in the human population
The parasite reservoir has now virtually died out in the original 7-
country operations area
 OCP also distributes the drug Ivermectin where needed
 Program success
When launched, more than 1 million people in West Africa suffered
from Onchocerciasis
Currently, number of infected people within the original area of
operations is practically nil

23. PreventionandControl,continued
2. Personal protection measures against biting insects:-
• Wearing insect repellant such as N,N-Diethyl-meta-toluamide
(DEET) on exposed skin
• Wearing long sleeves and long pants during the day when blackflies
bite
• Wearing Permethrin- treated clothing
• Establishment of villages away from Simulium breeding places
3. Mass Distribution and Treatment : Ivermectin