lymphatic filariasis
TRANSCRIPT
Filariasis is a major parasitic infection, which continues to be a public health problem in the Philippines. It was first discovered in the Philippines in 1907 by foreign workers. Consolidated field reports showed a prevalence rate of 9.7% per 1000 population in 1998. It is the second leading cause of permanent and long-term disability. The disease affects mostly the poorest municipalities in the country about 71% of the case live in the 4th-6th class type of municipalities.
The World Health Assembly in 1997 declared “Filariasis Elimination as a priority” and followed by WHO’s call for global elimination. A sign of the DOH’s commitment to eliminate the disease, the program’s official shift from control to elimination strategies was evident in an Administrative Order #25-A,s 1998 disseminated to endemic regions. In support to the program, an Administrative Order declaring “November as Filariasis Mass Treatment Month was signed by the Secretary of Health last July 2004 and was disseminated to all endemic regions.
Vision: Healthy and productive individuals and families for Filariasis-free Philippines
Mission: Elimination of Filariasis as a public health problem thru a comprehensive approach and universal access to quality health services
Goal: To eliminate Lymphatic Filariasis as a public health problem in the Philippines by year 2017
General Objectives: To decrease Prevalence Rate of filariasis in endemic municipalities to <1/1000 population.
Specif ic Objectives:The National Filariasis Elimination Program
specifically aims to:1. Reduce the Prevalence Rate to elimination level
of <1%;2. Perform Mass treatment in all established
endemic areas;3. Develop a Filariasis disability prevention program
in established endemic areas; 4. Continue surveillance of established endemic
areas 5 years after mass treatment.
Human Lymphatic Filariasis is a chronic parasitic infection caused by nematode parasites known as wuchereria bancrofti, brugia malayi or brugia timori.The young and adult worms live in lymphatic vessels and lymph nodes while the microfilariae are usually found in blood. The life- span of the adult parasites is about 10 years ( but a 40-year life- span has been reported)while microfilariae live for about a year at the most.
The disease is transmitted to a person through bites from a infected female mosquito primarily Aedes poecillius that bites at night.
The filarial life cycle, like that of all nematodes, consists of 5 developmental (larval) stages in a vertebral host and an arthropod intermediate host and vector. Adult female worms produce thousands of first-stage larvae, or microfilariae, which are ingested by a feeding insect vector. Some microfilariae have a unique daily circadian periodicity in the peripheral circulation. The arthropod vectors (mosquitoes and flies) also have a circadian rhythm in which they obtain blood meals. The highest concentration of microfilariae usually occurs when the local vector is feeding most actively.
Microfilariae undergo 2 developmental changes in the insect. Third-stage larvae then are inoculated back into the vertebral host during the act of feeding for the final 2 stages of development. These larvae travel through the dermis and enter regional lymphatic vessels. During the next 9 months, the larvae develop into mature worms (20-100 mm in length). An average parasite can survive for about 5 years.
The prepatent period is defined as the interval between a vector bite and the appearance of microfilariae in blood, with an estimated duration of about 12 months.
The quantity of accumulating adult worm antigen in the lymphatics
The duration and level of exposure to infective insect bites
The number of secondary bacterial and fungal infections
The degree of host immune response
Filarial infection generates significant inflammatory immune responses that participate in the development of symptomatic lymphatic obstruction. Increased levels of immunoglobulin E (IgE) and immunoglobulin G4 (IgG4) secondary to antigenic (from dead worms) stimulation of Th2-type immune response have been demonstrated.
Studies have shown that there is a familial tendency to lymphatic obstruction, providing support for the hypothesis that host genes influence lymphedema susceptibility. Studies also suggest that microfilaremia may be increased in individuals with low levels of mannose-binding lectin, suggesting a genetic predisposition.Further, a propensity to develop chronic disease has been demonstrated in patients with polymorphisms of endothelin-1 and tumor necrosis factor receptor II.
Prenatal exposure seems to be an important determinant in conferring greater immune tolerance to parasite antigen. Thus, individuals from endemic areas are often asymptomatic until late in the disease when they have high worm burden, whereas nonimmune expatriates tend to have brisk immune responses and more severe early clinical symptoms, even in light infections.
Studies have shown that lymphatic filarial parasites contain rickettsialike Wolbachia endosymbiotic bacteria. This association has been recognized as contributing to the inflammatory reaction seen in filariasis.
The incubation period which starts from the entry of the infective larvae to the development of clinical manifestation is variable. Nevertheless, it ranges from 8-16 months.
ASYMPTOMATIC STAGE: Characterized by the presence of microfilariae in the
peripheral blood No clinical signs and symptoms of the disease Some remain asymptomatic for years and in some
instances for life Others progress to acute and chronic stages Microfilariae rate increases with age and then levels off In most endemic areas including the Philippines the
Philippines, men have higher microlariae rate than women.
Starts when there are already manifestation such as:
Lymphadenitis ( Inflammation of lymph nodes) Lymphangitis ( inflammation of lymph vessels) In some cases, the male genitalia is affected
leading to funiculitis, epidydimitis, or orchitis ( redness, painful and tender scrotum)
Develop 10-15 years from the onset of the first attack
Immigrants from areas where filariasis is not endemic tend to develop this stage more often and much sooner (1-2 years) than do the indigenous population of endemic areas.
Hydrocoele (swelling of the scrotum) Lymphedema ( temporary swelling of the upper
and lower extremities) Elephantiasis ( enlargement and thickening of the
skin of the lower and/or upper extremeties, scrotum, breast)
Physical examination is done in the main health center or during scheduled survey bites in the community
History taking Observation of the major and minor signs ang
symptoms
STRATEGY 1. Endemic Mapping STRATEGY 2. Capability Building STRATEGY 3. Mass Treatment (integrated with
other existing parasitic programs) STRATEGY 4. Support Control STRATEGY 5. Monitoring and Supervision STRATEGY 6. Evaluation STRATEGY 7. National Certification STRATEGY 8. International Certification
Nocturnal Blood Examination (NBE)- blood are taken from the patient at the patient’s residence or in the hospital after 8:00 pm
Immunochromatographic Test (ICT)- it is the rapid assessment method. It is an antigen test that can be done at daytime.
1. Selective Treatment – treating individuals found to be positive for microfilariae in nocturnal blood examination.
Drug: Diethylcarbamazine Citrate
Dosage: 6 mg/kg body weight in 3 divided doses for 12 consecutive days (usually given after meals)
2. Mass Treatment – giving the drugs to all population from aged 2 years and above in all established endemic areas.
Drug: Diethlcarbamazine Citrate (single dose based on 6 mg/kg body wt) plus Albendazole 400mg given single dose given once annually to people 2 yrs & above living in established endemic areas
3. Disability Prevention thru home-based or community-based care for lymphedema & elephantiasis cases. Surgical management for hydrocele patients.
PROVINCES THAT REACHED ELIMINATION STAGE: Southern Leyte, Sorsogon, Biliran, Bukidnon, Romblon, Agusan Sur, Dinagat island, Cotabato Province and COMVAL
1. Assist low performing areas to increase the MDA coverage in order to interrupt the transmission of the LF.
2. Assist implementing Units to reach the goal of elimination.
3. Strengthen integration with other NTD programs. 4. Strengthen the disability prevention strategy thru
community-based or home –based care & thru integration with leprosy.
5. Implement an integrated vector management 6. Implement a sustainability plan for provinces that
have reached elimination level.
Basic Components1. Hygiene2. Prevention & cure
of entry lesions3. Exercise4. Elevation of foot5. Use of proper
footwares
Lymphoedema management helps
to eliminate the bad odour to prevent & heal entry
lesion to help patients self-
confident to reduce the size of the
lyphoedema to prevent disability to prevent economic loss
Filariasis patients are advised to observe personal hygiene by washing the affected areas with soap and water at least twice a day or prescribed antibiotics or anti- fungals for super infection.
A.Measures aimed to control the vector
Environmental sanitation such as proper drainage and cleanliness of surroundings
Spraying with insecticides may also produce harmful effects)
B. Measures aimed to protect the individual and families in endemic areas
Use of mosquito nets Use of long sleeves, long pants and socks Application of insect repellants screening of
houses Health education
The prognosis in filariasis is good if infection is recognized and treated early. Filarial diseases are rarely fatal, but the consequences of infection can cause significant personal and socioeconomic hardship for those who are affected.
The morbidity of human filariasis results mainly from the host reaction to microfilariae or developing adult worms in different areas of the body. The WHO has identified lymphatic filariasis as the second leading cause of permanent and long-term disability in the world.
References:
Cuevas, Frances Prescilla L.et al;2007 Public Health Nursing in the Philippines 10th edition,pp257-260
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