Lymphatic Filariasis Treatment:

the effectiveness of combined treatment of

doxycycline, diethylcarbamazine, and albendazole

in elimination of microfilaria and adult nematode

March 17, 2008

Biology 448B

Summary

Lymphatic filariasis is one of the more neglected tropical diseases, despite its effect on

hundreds of millions of people worldwide. Although the WHO (2002) suggests that it is one of the six

eradicable infective diseases with the tools available today, there is yet to be an effective drug regimen

implementation. For this purpose, the goal of this study is to investigate the effectiveness of using

doxycycline, a new discovery in killing adult nematodes, in combination with the current treatment of

diethylcarbamazine (DEC) and albendazole. The study will take place in twelve lymphatic filariasis-

endemic villages in the Cuddalore district, Tamil Nadu State, southern India. To compare the effects of

the proposed combination treatment, 3 other treatments (doxycycline only, DEC-albendazole, and

control) will be conducted.

Introduction

Filariasis is a parasitic disease caused by nematodes inhabiting the human body. There are

eight species that infect humans: Wuchereria bancrofti, Brugia malayi, Onchocerca volvulus, Loa loa,

Mansonella perstans, M. streptocerca, M. ozzardi, and Brugia timori (DPD, 2004). These species

causes various diseases by inhabiting different parts of the body. Wuchereria bancrofti, Brugia malayi

and Brugia timori are responsible for lymphatic filariasis, which causes clinical features such as lymph

edema and elephantiasis (Nissen and Walker 2006).

The major cause of lymphatic filariasis world wide, Wuchereria bancrofti, will be the focus of this

study.

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Figure 1 Life Cycle of Wuchereria bancrofti Division of Parasitic Diseases (DPD). 2004. Filariasis.

The symptoms of lymphatic filariasis are mostly caused by the adult stage (figure 1, stage 2) of

the nematode parasite inside the lymph nodes and lymph vessels (Nissen and Walker 2006). With only

microfilaria in the system, patients are generally asymptomatic. Acute manifestations are usually caused

by bacterial secondary infections where affected limbs and lymph nodes become swollen, painful, and

tender (Anitha and Shenoy 2001). They can also be caused by death of adult worms in the lymphatic,

although this is much rarer (Anitha and Shenoy 2001). Chronic manifestations are characterized by the

disease progressing into lymphoedema and, consequently, elephantiasis in which genitals and limbs

swell (Anitha and Shenoy 2001). There could also be genitor-urinary lesions and various complications.

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Relevance

As one of the more neglected tropical diseases, the burdens of filariasis are grossly overlooked.

Although the disease itself is not fatal, it affects 120 million people worldwide, with 40 million disfigured

or disabled by it; over a billion people are at risk of contracting the disease (WHO, 2002). WHO (2002)

suggests that lymphatic filariasis could be the world leading cause of permanent and long-term

disability.

According to research by Michael et al. (1996), filariasis disease symptoms are more prevalent

in adults and seniors, especially males. This creates a detrimental decrease in productivity and

becomes a huge economic burden for many countries, a disease burden calculated in disability-

adjusted life years (DALYs) second only to malaria (WHO, 2002). The disease demographic also has an

effect on dependency ratio, and therefore, a lowered GDP per capita for endemic countries (figure 2).

Figure 2 Lymphatic filariasis endemic countries World Health Organization (WHO). 2002. Annual Report on Lymphatic Filariasis 2001.

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With new understanding of the disease, diagnosis, and treatment, it is not impossible to

eradicate lymphatic filariasis, given the resources (personnel, drugs, etc) and the right drug regime and

implementation (WHO, 2001). This study will test out a new combination of drugs that can, in theory,

eliminate both microfilaria and adult nematodes (figure 1: stages 2 and 3) at the same time. The results

of this study will be vital in generating a new implementation program towards eradicating lymphatic

filariasis.

Current Diagnosis and Treatment

Current diagnosis is done by sensitive, specific, user-friendly immunochromatographic card test

(ICT) using fingerpick blood to detect antigens without the need for expensive, hard to operate

equipment (Njenga and Wamae 2001). According to the evaluation by Njenga and Wamae (2001), ICT

has 100% specificity and sensitivity. ICT works by detecting circulating filarial antigens released by adult

worms, which distinguishes between past and current infections (Njenga and Wamae 2001). This is an

effective, quick method of diagnosis that can be incorporated easily into filariasis treatment projects

since it can be done on-site.

As of now, the World Heath Organization’s (WHO) strategy to treating filariasis in endemic

areas is by eliminating microfilaria in the blood of infected individuals, thereby eliminating transmission

by mosquitoes. As shown in figure 1, transmission of the disease is by ingestion of microfilaria in

circulation by mosquitoes. However, there are no treatments for killing adult worms for individuals

already infected.

Single dose of 6mg/kg body weight of diethylcarbamazine (DEC) each year is effective in

reducing microfilaria circulation; however, 50% of the time DEC is ineffective against adult worms

(Anitha and Shenoy 2001), which are the major cause of symptoms of lymphatic filariasis.

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According to Anitha and Shenoy (2001) 200 to 400 ugm/kg body weight of ivermectin is also

effective in lowering microfilaria counts despite the slower clearance. DEC and ivermectin have been

known to cause fever and discomfort due to destruction of microfilaria in the blood (Anitha and Shenoy

2001).

Albendazole is shown effective in killing adult worms with treatments of 400mg twice daily for

two weeks; however, there are severe reactions associated with it in W.bancrofti filariasis (Anitha and

Shenoy 2001) and the results are not ideal. Although albendazole does not act directly on microfilaria,

its effect in eliminating microfilaria when used in combination with DEC or ivermectin is quite

pronounced (Anitha and Shenoy 2001).

For the infected individuals, the WHO recommends treatment with combinations of DEC

(6mg/kg body weight) plus ivermectin (400ugm/kg body weight), DEC plus albendazole (400mg), or

albendazole plus ivermectin, all annual single doses.

So far, there have been suggestions for five year programs to eliminate lymphatic filariasis in

endemic villages (Plaisier et al. 2000). However, without the means to kill adult worms, the feasibility of

complete eradication seems unlikely. With an estimated maximum lifespan of 6-8 years (Gems 2000),

there is a possibility of adult worm lifespan outlasting the program and reproducing.

Recent Discovery

Inside filarial nematodes, there is an endosymbiotic bacterium Wolbachia that is essential in

larval development and adult worm fertility (Taylor et al. 2005). In terms of evolution, there is evidence

of a long and stable relationship of co-existence between Wolbachia and nematodes. Furthermore, the

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bacteria are passed down vertically (Fenn and Blaxter 2007). Early research by Hoerauf et al. (1999)

shows that treatment with tetracycline kills the bacteria and causes abnormalities in growth, shedding of

microfilaria, viability, and lifespan of nematodes.

In the recent research done by Hoerauf et al. (2007), doxycycline (a member of the tetracycline

antibiotics group) is found to be macrofilaricidal. Administration of 200mg/day of doxycycline for 4-6

weeks resulted in over 60% deaths of female worms. However, newly acquired Wolbachia-containing

worms were found after the treatment. This suggests that doxycycline would only be effective as a

treatment in transmission-free zones.

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Proposed Project

Goal

There are two stages of W.bancrofti in the human host as seen in figure 1. The current

treatment of DEC-albendazole treatment is effective in lowering microfilaria count in the blood. This

treatment, along with the recent discovery of the macrofilaricidal property of doxycycline by killing

Wolbachia bacteria, is the basis of this project. If W. bancrofti is unable to complete their life cycle and

reproduce in the human host, transmission will cease. In theory, by effectively eliminating both

microfilaria and adult nematodes concurrently, eradication of lymphatic filariasis is very much possible.

Therefore, the goal of this study is to investigate the effectiveness of combined treatment of

doxycycline, diethylcarbamazine (DEC), and albendazole (C) compared with DEC-albendazole

combination treatment (A), doxycycline treatment (B), and no treatment (D) in eliminating W. bancrofti

(both adult nematodes and microfilaria) from the system of the host and reducing transmission.

At the end of the study, the goal is to refine an effective new implementation and drug regime

strategy toward eradicating lymphatic filariasis.

Hypothesis

Treatment C will be significantly more effective in elimination of W. bancrofti and reduction of

transmission than treatments A, B, and D.

Subject

In a study by Srividya et al. (2000), thirty rural communities in a filariasis-endemic region in

Cuddalore district (figure 3) in Tamil Nadu State in southern India were assessed. The thirty villages

were chosen randomly from 62 villages that had populations between 500 and 2500 (Srividya et al.

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2000). From these 62 filariasis endemic villages, twelve that meet the criteria of being secluded and with

a small population (ideally under 750) will be chosen. Furthermore, since transmission of disease is also

a factor in the study, the villages must be far apart enough so that mosquito’s habitat areas do not

overlap. We will be working out details of the recruitment with the Tamil Nadu State government, which

should not be a problem since they have been cooperative toward programs aimed toward filariasis

elimination (WHO, 2002).

Figure 3 Filariasis distribution in India (1995) Pradeep Kumar, N., K.P. Patra, S.L. Hoti, and P.K. Das. 2002. Genetic variability of the human filarial parasite, Wuchereria bancrofti in South India. Acta Trop., 82(1):67–76

Since filariasis can be asymptomatic, at the start of the study, every villager (adult and children)

will be screened with ICT for active filariasis infections during the night time (night blood survey 20:00 to

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24:00). The infected individuals of each village will be the subject of the study. There will be 3 villages

for each of the 4 treatments. The treatments will be assigned to the villages randomly.

Protocol

Treatments:

A: DEC-albendazole combination: Single doses of 6mg/kg body weight DEC with 400mg albendazole

will be given to all infected individuals as soon as they are diagnosed. The treatment will be followed by

3 months of daily placebos. Data will be collected every 4 months to see the microfilaria counts in the

blood.

B: Doxycycline: Subjects will be treated with 200mg/day of doxycycline for 3 months with two placebos

on the first day of treatment. Data will be collected every 4 months.

C: Doxycycline and DEC-albendazole combination: As soon as subjects are diagnosed with filariasis,

single doses of 6mg/kg body weight of DEC and 400mg of albendazole will be given on the first day of

treatment. Then, 200mg/day of doxycycline for 3 months will follow. Data will be collected every 4

months to see the process of treatment.

D: Control: Two placebos will be given on the first day, followed by 3 months of daily placebos. Data will

be collected every 4 months to see the progress of the disease.

Then, every 6 months, ICT will be performed on all villagers previously diagnosed as non-

infected to monitor the transmission rate of the disease. If found infected, the persons will undergo

treatments as well.

The team will be working with a NGO group whose aim is to educate villages in reduction of

transmission by vector control through bed nets, insecticide sprays, and elimination of breeding sites.

However, analysis of the effect of vector control is not part of this study. Since all 12 villages will be

educated in the same method, this will not be considered a variable in this study.

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Furthermore, the team at each village will provide education of ways to alleviate disease burden

such as elevating affected limbs, personal hygiene, and self-care.

Data Collection

Every 4 months, all infected individuals will provide a blood smear and physical examination for

microfilaria count and disease symptoms. The study is to run for 2 years from the start of diagnosis. The

data will be used to compare the effectiveness of treatments A, B, C, and D. ICT will give disease

transmission rate data every 6 months. The results of the treatments will be evaluated on severity of

disease symptoms, microfilaria count, and rate of disease transmission. If treatment C is more effective

than the other 3 treatments, then the microfilaria count and number of new filariasis-positive ICT after

initial diagnosis will be significantly lower.

Cost

The cost of ICT is US$2.75/unit (Braga et al. 2003). However, taken into account the high

sensitivity and user-friendliness, ICT reduces the cost of highly trained and experienced personnel.

Assuming that the twelve villages have average populations of 625 each, US$83,000 will be needed to

perform ICT twice a year for two years on every member of the community.

From previous survey done by Srividya et al. (2000), the disease prevalence in Cuddalore

district villages ranges from 8-26%. Extrapolated from this data, if 10% of the population (75

individuals/village) is to be treated with doxycycline (6 villages) and DEC (6 villages), then the cost

would be US$2,000 in total (estimation of US$2/person) (PAHO, 2006).

SmithKline Beecham, which has supported WHO New Lymphatic Filariasis Regional Strategic

Plan for south-east Asia (WHO, 2001), will support this study with a free supply of albendazole.

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Data collection of all infected individuals every 4 months is estimated to cost US$10,000 each

year, including the cost for personnel and compensation for local leaders. Since the exact population of

the villages and the disease prevalence are yet to be known, the costs will vary slightly.

Logistical, Social, and Cultural Factors

The method of diagnosis with ICT, being very quick and non-invasive, should be culturally and

socially acceptable by all villages. However, the drug regime of daily doxycycline tablets may prove to

be difficult to follow. Therefore, it is essential that local leaders be very involved in educating and

supervising the subjects. To motivate the local leaders to keep a record of the patients’ progress and to

hand out drugs, the team will compensate accordingly.

Due to governmental health policies, ivermectin, despite being the drug that acts directly on

microfilaria, is not licensed for human use in India and is therefore not used in this study (Anitha and

Shenoy 2001).

The social effect of the study must be taken into account for future reference. The treatments

with placebos may have negative consequences. With no improvement after the “treatments”, villagers

may lose confidence in western medicine and may refuse other health programs in the future. Though

ethically challenging, a control is necessary for the purposes of this study.

Another potential problem is the willingness of infected individuals to seek treatment due to the

shame and stigmatization especially with lymphoedema genital damage. As with many other challenges

that may arise during the period of study, proper education and reasoning about the disease can be

very helpful.

Feasibility

The study does not require expensive equipment or experienced personnel. The drugs are all

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available and at low-costs. ICT can be performed by local villagers with simple instructions. However,

good leadership and management of the project are vital.

Since there are only 12 small villages, there is no need for large teams of researchers on site at

each village. There will not be a shortage of personnel. Since the implementation of the study will largely

involve local leaders, there will only be teams of 5 researchers, doctors or project managers at each

village. They will train and appoint local leaders for the distribution of drugs and explanation of study to

villagers.

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References

Anitha, K. and R.K. Shenoy. 2001. Treatment of lymphatic filariasis: Current trends. Indian J Dermatol Venereol Leprol, 67:60-5

Braga, C., M.I. Dourado, R.A. de A. Ximenes, L. Alves, F. Brayner, A. Rocha et al . 2003. Field evaluation of the whole blood immunochromatographic test for rapid bancroftian filariasis diagnosis in the northeast of Brazil. Rev. Inst. Med. trop. S. Paulo, 45(3): 125-129.

Division of Parasitic Diseases (DPD). 2004. Filariasis.

Fenn, K. and M. Blaxter. 2007. Coexist, cooperate and thrive: Wolbachia as long-term symbionts of filarial nematodes. Issues Infect Dis. Basel, Karger, 5:66-76.

Gems, David. 2000. Longevity and ageing in parasitic and free-living nematodes. Biogerontology, 1: 289–307

Hoerauf, A., K. Nissen-Pahle, C. Schmetz, K. Henkle-Duhrsen, M.L. Blaxter, W.B. Dietrich, M.Y. Gallin, K.M. Al-Qaoud, R. Lucius, and B. Fleischer. 1999. Tetracycline therapy targets intracellular bacteria in the filarial nematode Litomosoides sigmodontis and results in filarial infertility. J. Clin. Invest, 103(1):11–18.

Michael, E., D.A. Bundy, and B.T. Grenfell. 1996. Re-assessing the global prevalence and distribution of lymphatic Filariasis. Parasitology, 112(4):409-28.

Nissen, M.D. and J.C. Walker. 2006. Filariasis [online]. Available from http://www.emedicine.com/med/topic794.htm [cited 8 March 2008]

Njenga, S.M. and C. N. Wamae. 2001. Evaluation of ICT Filariasis Card Test Using Whole Capillary Blood: Comparison with Knott's Concentration and Counting Chamber Methods. The Journal of Parasitology, 87(5):1140-1143.

Pan American Health Organization (PAHO). 2006. Financing the National PELFs: Identifying Alternatives for 2006 & Beyond—the Need for a Regional Plan & the Way Forward.

Srividya, A., R. Lall, K.D. Ramaiah, K.Ramu, S. L. Hoti, S. P. Pani, and P. K. Das. 2000. Development of rapid assessment procedures for the delimitation of lymphatic filariasis-endemic areas. Tropical Medicine and International Health, 5(1):64-71.

Taylor, M.J., W.H. Makunde, H.F. McGarry, J.D. Turner, S. Mand, and A. Hoerauf. 2005. Macrofilaricidal activity after doxycycline treatment of Wuchereria bancrofti: a double-blind, randomized placebo-controlled trial. Lancet, 365(9477):2116-21.

World Health Organization (WHO). 2001. Regional Strategic Plan for Elimination of Lymphatic Filariasis (2000-2004).

World Health Organization (WHO). 2002. Annual Report on Lymphatic Filariasis 2001.

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