World Health Organization declares Viet Nam Free of Lymphatic Filariasis

Reepa Agrawal
14 Nov, 2018

World Health Organization (WHO) announced recently that Viet Nam has successfully eliminated lymphatic filariasis as a public health problem. Elimination is defined as “lymphatic filariasis ceases to be a public health problem, when the number of microfilaria carriers is less than 1% and the children born after initiation of elimination of lymphatic filariasis are free from circulating antigenemia.”

Lymphatic Filariasis is a tropical parasitic disease caused by nematodes of Filariadidae family, Wuchereria bancrofti (90% cases), Brugia malayi and Brugia timori which is transmitted by mosquitoes and affects the lymphatic system impairing its drainage. It is also known as elephantiasis because of the resemblance of the disfigurement caused by painful swollen limbs which makes the life of the patient miserable. This vector borne disease is caused by filarial parasite and transmitted by aedes (aegypti, polynesiensis) mosquito in the Pacific region.

WHO launched its Global Programme to Eliminate Lymphatic Filariasis (GPELF) in 2000. In 2012, the WHO neglected tropical diseases roadmap reconfirmed the target date for achieving elimination by 2020. WHO’s strategy is based on 2 key components:

• Stopping the spread of infection through large-scale annual treatment (known as Mass Drug Administration) of all eligible people in an area or region where infection is present; and

• Alleviating the suffering caused by lymphatic filariasis through provision of the recommended basic package of care.

This is a 4 step process which includes MAPPING, MASS DRUG ADMINISTRATION (MDA), SURVEILLANCE and finally VERIFICATION.

Most important strategy is MDA. The intent of MDA is to target every eligible individual, including children, living in all endemic areas. Its effectiveness in reducing microfilarial prevalence and density in the blood is directly related to the proportion of the population that takes the medicines every year (known as epidemiological drug coverage). The recommended regimens for MDA are:

• Once-yearly treatment with a single dose of two medicines given together: albendazole (400 mg) plus either ivermectin (150–200 mcg/kg)

• DEC (6mg/kg) for 4-6 years: or exclusive use of table and cooking salt fortified with DEC for 1-2 years

It is implemented and continued for a period of five years or more to reduce the number of parasites in the blood to levels that will prevent mosquito vectors from transmitting infection.

Post-MDA surveillance: When the criteria for interruption of transmission have been met in a given evaluation unit, and programmes decide to stop MDA, infection levels are monitored for at least 5 years, and routinely thereafter to evaluate whether recrudescence occurs. Surveillance is implemented after MDA is discontinued to identify areas of ongoing transmission or recrudescence. If criteria are met, the elimination of transmission is verified.

Final step is verification of interruption of transmission.

The basic package of care for morbidity management includes treatment for episodes of adenolymphangitis (ADL); guidance in applying simple measures to manage lymphedema to prevent progression of disease & debilitating, inflammatory episodes of ADL; surgery for hydrocele and treatment of infected people with anti-filarial medicines.

In Viet Nam the prevalence of infection gradually declined in many areas through environmental changes, improvements in housing, increased use of bed nets and selective treatment. Annual mass treatment campaigns between 2002 and 2008 stopped transmission in remaining endemic areas, and surveillance has continued. Last year, the country established a pioneering new training programme to ensure sustained care for people with complications from lymphatic filariasis. Surveillance showed Viet Nam completed 5 or more rounds of MDA with 100% geographical coverage.

Since WHO launched the Global Programme to Eliminate Lymphatic Filariasis in 2000, a total of 11 countries and areas in the Western Pacific Region have been validated as having eliminated lymphatic filariasis as a public health problem: Cambodia, China, Cook Islands, Niue, the Marshall Islands, Palau, the Republic of Korea, Tonga, Vanuatu, Viet Nam, and Wallis and Futuna. Lymphatic filariasis remains endemic in 13 countries and areas in the Region: American Samoa, Brunei Darussalam, Fiji, French Polynesia, Kiribati, Lao People’s Democratic Republic, Malaysia, Federated States of Micronesia, New Caledonia, Papua New Guinea, Philippines, Samoa and Tuvalu.

Achieving the goal of elimination was not easy at all and now continuous post surveillance as well as morbidity management is a herculean task.
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