Lymphatic filariasis

Lifecycle

- Microfilariae in the blood

- Wuchereria bancrofti transmitted by Culex, Anopheles, Aedes, Mansonia mosquitoes

- Brugia malayi by Mansonia and Aedes mosquitoes

- Adult filaria live 6-8 years!

Global distribution

Species distribution

Brugia species restricted to Southeast Asia & Indian subcontinent

Pathology & disease

- Most infections asymptomatic

- Chronic pathology associated with tissue damage/blockage caused by microfilariae

- Elephantiasis & hydrocoele

Diagnostics - microscopy & nocturnal periodicity

- Identification of microfilariae by blood smear microscopy

- Blood collection for W. bancrofti should be done at night because of nocturnal periodicity

- Periodicity driven by biting behaviour of mosquito vector

Diagnostics -molecular methods

Alere Filariasis Test Strip (FTS) for the qualitativedetection ofWuchereria bancroftiantigen

- BrugiaRapid point-of-care cassette test (BRT)to detect IgG4 antibody

- PCR methods to detect microfilarialDNA

Diagnostics - ultrasonography

Treatment

- ivermectin, diethylcarbamazine & albendazole (IDA)

Mazzotti reactions

- Mazzotti reactions can be life threatening, characterized by fever, urticaria, swollen and tender lymph nodes, tachycardia, hypotension, arthr algias, oedema and abdominal pain

- Associated with the rapid killing of microfilariae, particularly those of Onchocerca volvulus

- Limits use of DEC in Africa (where O. volvulus is endemic)

Treatment - antiwolbachial therapy

- Wolbachia endosymbionts present in many filarial nematodes

- Required for fertility, development & viability of adult worm and microfilariae (transmission blocking)

- Treatment with tetracycline antibiotics leads to worm infertility & "controlled death"

Control methods

1. Reducing exposure

• Bed nets

• Indoor residual spraying

• Clothing

• Repellant

2. Vector control/management

• Larviciding

• Biological control

3. Preventive chemotherapy (mass drug administration)

Vector management/control of breeding sites

Anopheles (ponds, streams, clean unpolluted)

Aedes (tires, buckets, stagnant water)

DEC salt

- Low dose of DEC added to cooking salt

- Can tackle problems associated with poor adherence to MDA

- Questions remain on economic viability

Global Programme to Eliminate Lymphatic Filariasis (GPELF)

Impact of GPELF =

200 million (2000) -> 50 million (2018)