NEMATODES

FILARIAL WORMS
 FILARIAL WORMS (Life Cycle)
• Nematodes found in blood and lymphatics, transmitted by vectors
• Wuchereria bancrofti (more prevalent) and Brugia malayi

Mosquitoes suck human blood

• Drops of blood drop on skin
• Blood contains the larva (penetrates the skin through the bite wound)
• Larva is not injected
L3 larva goes to lymphatic system
• Develops into adult male and female
• Reproduce to produce microfilaria
 FILARIAL WORMS (Life Cycle)
Microfilaria released to bloodstream
• Passes through the lungs (blood vessels of lungs)
• Goes to the peripheral blood
• Diagnostic stage
Mosquito bites human
• Ingests microfilaria
• Microfilaria goes to mosquito’s stomach
• Sheath sheds
Unsheathed microfilaria migrates to the thorax of the mosquito
• Microfilaria becomes L1 then L3
• L3 migrates to proboscis
 FILARIAL WORMS
• Malayan Filariasis: seen in Palawan, Eastern Samar, Agusan del Sur, Sulu
• Disease seen more in adults than children
• Males more affected
• Final host: man
• Intermediate host: mosquito
• W. bancrofti: prefer localization in scrotal lymphatics
• B. malayi: less severe
• Infective stage to FH: L3 filiform larva
 FILARIAL WORMS
• Infective stage to IH: microfilaria (sheathed)
• Diagnostic stage: microfilaria
• ideal breeding sites for mosquitoes:
• Colocasia esculenta
• Musa textilis
o Water lilies
• Those constantly exposed: have less severe symptoms
o Immune system is primed/exposed
o People not exposed: when they go from a non-endemic to an endemic
area, they may experience more severe symptoms (called the
Expatriate Syndrome)
 FILARIAL WORMS
Habitat - Lymphatics (in adults)
Mode of Transmission - Active larval penetration
Disease Manifestation
Lymphatic Filariasis
• To get the infection, they are constantly bitten by the mosquito
• Asymptomatic Phase: thousands to millions of microfilaria in the
blood and adult worms in the lymphatics
o Seen in “Endemic Normals” (they have in their blood the
parasite antigen instead of the microfilariae)
o Patients appear healthy and no clinical manifestations seen
o Microfilaria come from lymphatic vessels (from the adult
worms there)
o Symptoms are nonspecific
• Early Manifestation: Fever, lymphadenitis, welling, redness of arms and legs,
vomiting, headache o Lymphadenitis: inflammation of lymphatic
vessels, triggered by the adult worms
 FILARIAL WORMS
• ADLA (Acute Dermatolymphangioadenitis)
o Inflammation of lymph
o Adenolymphangitis
o Swelling or inflammation of lymphatic vessels
o Most common manifestation
• Chronic Phase: Elephantiasis, Hydrocoele, Chylocoele,
Lymphocoele, Chyluria
o 10 years or more after the initial infection
o Elephantiasis: enlargement of different parts of the body
o Parasites might be dead already (life span of around 10 years)
▪ Parasites calcify and cause obstruction and
inflammation (this triggers the Elephantiasis, Hydrocele,
Chylocele, Chyluria)
• Accumulation of lymphatic fluid
• Chyluria: fluid find its way to the urinary system
 FILARIAL WORMS
Diagnosis
• Best to diagnose early (when acute and asymptomatic)
• Thick smears (Giemsa) – look for microfilaria
o W. bancrofti: collect blood from 10 pm to 2 am (Nocturnal
Periodicity)
o B. malayi: subperiodic periodicity
• Diethylcarbamazine Provocative Test
o Orally
o Done especially if difficult to collect sample during the night
o 3 mg/weight kilogram of patient
o Triggers release of microfilaria
 FILARIAL WORMS
Epidemiology
• Bancroftian Filariasis: more widespread, affects India, SEA, Pacific
Islands, Africa, and South and Central America
• Malayan Filariasis – affects SEA
• Common in Bicol (because of abaca, where the mosquitoes breed)
o Most affected: farmers working in abaca plantations
• Disease among adults (elephantiasis)
o Because they got the infection when they were children,
manifested when they were adults already
 FILARIAL WORMS
Treatment
• DOC: Diethylcarbamazine (DEC)
• Ivermectin
• Albendazole
• doxycycline
• For elephantiasis, doctor aspirates fluid
o Can lead to bacterial infections
Prevention
• Insect repellants
• Vector control
• Mass drug administration (MDA)
 Brugia timori
• Similar to bancroftian filarisis in clinical presentation
• Microfilaria
o Longer than B. malayi
o Cephalic space = 3:1
o Sheath unstained by Giemsa
o Periodicity: nocturnal
o Vector: Anopheles barbirostris
OTHER FILARIAL WORMS
 LOA LOA
• common name: African Eye Worm
Vector
• Chrysops, Mango fly, Tabanid fly
Disease Manifestation - Loaiasis
• worms able to migrate through tissues and conjunctival tissue across the eyeball
o Edema of Conjunctivitis and eyelids
o Calabar swellings: localized subcutaneous edema (also called fugitive swelling)
▪ Allergic reaction indicative of Loa loa
• Cause blindness
• Progressive keratitis
Diagnosis
• Presence of calabar swellings (allergic reaction)
• Appearance of worm in conjunctiva
• Detection of microfilaria
• Skin test
Periodicity - Diurnal (during the day)
Epidemiology - Sudan, Congo, West Africa
 MANSONELLA OZZARDI
• common name: New World Filaria
• Disease manifestation: Mansonellosis ozzardi
o Usually asymptomatic
o Inguinal adenopathy: inflamed lymph nodes in the inguinal
area
 MANSONELLA STREPTOCERCA
• Formerly known as Dipetalonema streptocerca
• Vector: small midges belonging to Culicoides
• Disease manifestation: pruritus dermatitis with hypopigmented
macules (pale spots) and inguinal adenopathy
• Microfilaria found in the skin
o Unsheathed: nuclei extend up to the tip, tip bent in the form
of a shepherd’s crook
 MANSONELLA PERSTANS
• Formerly Dipetalonema perstans
• Common name: persistent filarial worm
• Disease manifestation: usually benign, calabar swellings, pruritus,
hives, fever
• Causes Kampala or Ugandan Eye Worm
 ONCHOCERCA VOLVULUS
• Onchocerciasis: major cause of blindness in some parts of Africa
• Also known as river blindness (blindness)
• Vector: Black fly (Simulium damnosum)
• Can cause skin nodules, progressive keratitis
• Diagnosis: history, symptoms, microfilaria in nodules
 DIROFILARIA IMMITIS
• Common name: Dog heartworm
• Final host: dogs
• Accidental host: man
• Vector: mosquitoes
• Pathology: presence of peripheral nodules in the lung (coin lesions),
obstruction of heart