THE FILARIAE

Tissue Nematodes comprises 8 species of filariae: 1. Wuchereriria bancrofti 2 Brugia malayi 3. Brugia timori 4. Onchocerca volvulus 5. Loa Loa 6. Mansonella perstans 7. Mansonella streptocerca 8. Mansonella ozzardi 9. Dracunculus medinensis = not a filarial worm but morphologically similar

Characteristic features:(1) the adults live in the tissues(2) female worms give birth to larvae known as microfilariae that circulate in the blood and lymph or are present in tissues(3) transmission requires the ingestion of the microfilariae by a bloodsucking arthropod, which in turn, transmits the infection to another human

Wuchereria bancrofti Syn : Filaria Bancrofti Disease : Bancroftian Filariasis Adult Worm

= long, hair-like & transparent w/ smooth cuticle = filiform shape w/ both ends tapering but terminate bluntly

rounded = head slightly swollen w/ 2 rings of small sessile papillae = mouth unarmed

Male = measures 40 mm. L X 0.1 mm. in diameter= copulatory spicule distinctly unequal & dissimilar= gobernaculum cresent – shaped = caudal end curved & sharply ventrad

Female = measures 8-100 mm. X 0.24 – 0.3 mm. = vulva cervical in position

= post. end narrow & abruptly pointed Microfilaria

= elongate, bluntly rounded anteriorly & pointed caudally = hyaline sheath extends beyond the ant. & post end of the

embryo = single stylet at the ant. end = cephalic space is long & broad & devoid of granules or nuclei = central column of nuclei discrete & do not extend down to the

tip of the tail = has graceful sweeping curve

Life Cycle :

Epidemiology := widely distributed in the tropics & subtropics = 2 types of filarial infection in the Phil.

A) urban type most prevalent in abaca raising areas mosquito vector – Aedes poecilus B) rural type occurs away from houses towards mountain and hill

Mosquito vector – anopheles minimus = both are night biter but may also bite during the day and breeds in clear running mountain stream Endemic Provinces ( Phil ) Camarines Norte & Sur Albay, Sorsogon, Quezon, Mindoro, Masbate, Romblon, Bohol, Leyte and Samar. All provinces of Mindoro, Mountain Province ( Bontoc ) Sulu & Palawan = Anopheles minimus & Flavirostris are vectors in Mt. Province, Sulu & Palawan = Aedes Poecilus in the rest of provinces

Pathology : = pathology prod. by parasite is centered in lymph vessel & lymph glands = inflammation, edema & fibrosis gives rise as a result of obstruction of lymph flow resulting to lymphangitis, edema& chyluria = clinical manif. includes: hydrocoele, chylocoele, elephantiasis of scrotum & vulva

Dx: 1) Blood smear (peripheral smear at night time 8:00 PM. to 4:00 AM.) because of nocturnal periodicity

= peak hours 10:00 PM. to 2:00 AM

2) Biopsy of material important for confirmatory diagnosis

Rx: 1. Diethyl carbamazine ( Hetrazan )-2mg/kg TID X 2-4wks 2. Surgical procedures 3. CorticosteroidsPrevention and Control :1) All abaca workers should wear long sleeve-shirt 2) Use of mosquito net3) Insect repellant4) Spray house w/ insecticide

Brugia Malayi Disease : Malayan Filariasis Geog. Distribution : Southeast Asia includes the Phil. Morphology :

Adult worm both male & female resembles that of W. Bancrofti Male = measures 23 mm. x 0.09 mm. in diameter

Female = measures 55 mm. x 0.16 mm. in diameter

Microfilaria:= measures 170-260 u = smaller than W. bancrofti = sheathed= appears knob-like = double stylets found at anterior end = cephalic space longer than broad = 2 discrete nuclei at the tail end portion

Life Cycle := similar with W. Bancrofti except for the species of mosquitoes as its intermediate host (mansonia bonnae & mansonia uniformis) ¯ ¯ found fresh H2O found in ricefield swamps

Pathogenesis and Pathology := pathological changes similar w/ Bancrofti filariasis = it has been observed that malayan filariasis affect the lower

extremities with lymphatic obstruction more frequent than in W. Bancrofti.Symptomatology :

= similar w/ W. Bancrofti

Epidemiology : 1) Endemic provinces ( Phil.) Palawan, Sulu, Agusan, Eastern Samar 2) Mosquito vector are night biter (Nocturnal periodicity) bites usually start 5:00 PM – 11:00 PM.3) Cat is an important reservoir host and may transmit the worm to man by means of Cat – Mosquito cycle Dx: = Blood smear ( appearance of sheathed filaria is nocturnal or maybe taken also) during daytime Treatment : The same with Prevention & Control : W. Bancrofti

Brugia Timori = 1st reported from island of Timor in 1964 = island of lesser Punda group in Indonesia = closely resembles bancroftian filariasis = high rate of abscess formation = predominance of elephantiasis of the legs

Microfilariae

= longer than B. malayi (ave. 310um)= cephalic space has a length-width ratio of 3:1 compared to B.

malayi 2:1= sheath does not stain with Giemsa stain = exhibit a nocturnal periodicity = vector: Anopheles barbirostris = humans: only definitive host

Treatment:= DEC = used for mass treatment = 5mg/kg/yr. for 10 days

= In adenolymphangitis = additional course of DEC = 300mg daily for 20 days (150mg

daily for children younger than 10 years)In ELISA: drop in filarial antigen level

Side effects: headache, generalized body malaise, chills, dizziness, anorexia® peak on 2nd day ® proven effective

Weekly administration of DEC at Low dosage ®proven effective over 18 months

= children <10 year old = 25mg >10 year old = 50mg

= swelling disappears within 1 year = elephantiasis clears up 2-4 years

Elephantiasis involving 1 extremity or affecting an arm rather than a leg proved easier to treat

It proved that Timoran filariasis responds better to therapy than the other lymphatic filariasis

Loa – Loa Syn : Eye worm Disease : Loasis / Calabar Swelling / Fugitive Swelling Geog. Distribution :

= West & Central Africa esp. Nigeria, Cameroon and Zaire Morphology :

Adult worm = threadlike cylindrical = cephalic end provided w/ papillae = body had cuticular bosses

Male = measures 32 mm. in length x 0.3-0.4 mm. in diameter Female = measures 50-70 mm. X 0.5 mm. in diameter Microfilaria = measures 250-300 u X 6-8 u in diameter

= sheathed = nuclei of the body are extended to the tip

Life Cycle := similar w/ that of W. Bancrofti = intermediate host are day-biting (diurnal periodicity) flies of the

genus chrysop (C. dimidiata & C. silacea)Pathology & Symptomatology:

= transitory inflammation of the subcutaneous tissue usually in the head (swelling may attain a hens egg size) w/c is tender & painful

= swelling usually disappear w/ in 2-3 days after occurrence thus the name fugitive swelling

Dx: = Surgical exploration of the swelling for presence of worm = Blood smear (recover microfilaria in the blood)= Serological test

Onchocerca volvulus ( convoluted filaria )Disease : Onchocerciasis / River Blindness / Blinding filariasis / Divers Blindness Geog. Distribution :

= Endemic Central & South America & Africa Morphology :Adult worm

= threadlike or wire-like white, opalescent transparent = measures 19-42 mm. x 130-210 u

= both ends blunt = cuticula possess distinct transverse striation = habitat – subcutaneous connective tissue as a tumor-like lesion

Male = measures 19-42 x 130-210 u = provided w/ perianal & caudal papillae =post. end tightly recurved ventrad

Female = measures 33.5-50 cm. in length x 270-400 u in width = vulva opens slightly behind the post end of esophagus

Microfilaria:= measures 150-368 u X 5-9 u in diameter = unsheathed w/ tail end pointed & nuclei free = ant end bluntly rounded & enlarged = post end narrow = no stylets seen at ant. end

Life Cycle := similar w/ W. Bancrofti = arthropod vector: genus simulium (black fly) which breeds in

river & stream = microfilaria in subcutaneous tumors migrate to other site but do

not enter to the bloodstream = periodicity (non-periodic) no statistical significance in the

appearance of infective stage

Pathology := encapsulation & proliferation as a result of migration of larva to the other part of body & elaboration of metabolites there is multiple nodular swelling of subcutaneous tissue (esp. head, chest &joints) presence of urticarial rashes and itchiness = eye lesion may also occur accompanied w/ photophobia or may progress to complete blindness

Dx: Skin biopsy (aspirate fluid from nodules) or scraping of the skin where nodules are found Rx: Diethyecarbomazine ( Hetrazan )

Antripol 100-200 mg initially then 1 mg. every week Prednisolone ( as anti-inflammatory drug )

Prevention and Control ( similar w/ Loa-Loa )

Dracunculus medinensis Disease: Dracontiasis, Dracunculosis, Dracunculiasis

= “the guinea worm”Female: 500-1,200L x 0.9-1.7mm in diameter Male: 12-29L x 0.4mm

= inhabits the cutaneous and subcutaneous tissues= attains sexual maturity as early as 10 weeks = female life span: 12-18 months

Epidemiology:= Middle East = Central India; Pakistan = Africa = parasite of dogs and other carnivores in

N. America

= worms develop to maturity in the body cavity in deeper connective tissues = females migrate to the subcutaneous tissues when they became gravid = body of fully gravid female worm is completely filled with uterus distended with larvae= papule is produced in the skin where the head of the female lies just under the dermis ® vesicular® ulcerate ® exposure of worm = loop of uterus prolapses through the wall of the worm ® lie in ulcer opening ® immersed in H2O ® larvae discharged = microfilariae have a well-developed digestive tract and never found in the blood in tissues of host ® discharged directly into water ® ingested by copepods ® mature within 2 weeks = whenever ulcer of infected person is immersed in H2O ® larva is liberated = if copepods are swallowed ® deep conn. Tissues maturation (1 year)

Pathology and Symptomatology:= onset of symptoms occurs just previous to the local eruption of the worm = early manifestation:- urticaria, erythema, dyspnea, vomiting, pruritus = slight to moderate increase in Eosinophils = if worm is broken during extraction and the larvae escape into the subcutaneous tissue ® severe inflammatory reaction produced ® pain ® secondary bacterial infection and abscess formation & sloughing of the tissues

Diagnosis:= made from the local lesion, worm or larvae = outline of the worm under the skin revealed by reflected light = calcified worms may be located by roentgenologic exam= discharge of the larvae is stimulated by cooling the ulcerated

area Treatment: 1) Metronidazole ® DOC

® 200mg TID x 7 days

® anti-inflammatory effect and action upon the worm Alternative:

Niridazole 25g/kg p.o. x 7 days Thiabendazole 25g/kg BID 2 days

2) Surgical removal under anesthesia Prevention:1) Avoid bathing and washing in waters 2) Drinking water and wells; springs should be surrounded by cement curbing3) Boil drinking water 4) Treating water supplies with chlorine