Introduction
Lymphatic Filariasis is a disease most commonly prevalent amongst people in the tropical and subtropical regions (Shenoy, 2008) and to date has been known to occur in 83 countries throughout the world (Streit & Lafontant, 2008). It has been shown to affect almost 120 million individuals worldwide and can be highly debilitating for affected individuals (Palumbo, 2008). It hence ranks as the second most common cause of physical disability globally, second only to psychiatric illnesses (Palumbo, 2008).
This disease affects both sexes and all age groups alike (Anosike, et al., 2005). Moreover, Filariasis has been known to be both a consequence of and a contributor to poverty (Streit & Lafontant, 2008). The magnitude of the burden of Lymphatic Filariasis is quite high as it contributes towards significant morbidity and is associated with both direct and indirect health-related costs.
Lymphatic Filariasis is a vector-borne disease, transmitted via mosquitoes, with the nematode worms Wuchereria bancrofti being the most common causative organism (Shenoy, 2008). Other, less common, causative organisms implicated in causing this condition are Brugia malayi and Brugia timori (Shenoy, 2008). The mosquito species most commonly implicated in the transmission of Lymphatic Filariasis in endemic regions include Culex, Anopheles, Aedes, and Mansonia (Shenoy, 2008).
As discussed above, Lymphatic Filariasis is a disease associated with poverty. Moreover, in regions where it is endemic, it affects a strikingly high number of individuals and thus has an enormous impact on the health-related quality of life of individuals residing in these regions. It has been reported that Nigeria accounts for the second-highest number of patients suffering from this disease amongst the countries harboring this infection (Anosike, et al., 2005).
Currently, an estimated 24 million Nigerians are at risk of contracting and developing this disease (Anosike, et al., 2005). Despite this high prevalence, to date, no large-scale study had been conducted in this region to determine the prevalence, trends, microfilaria rate, and clinical features of the disease in this part of the world. Anosike et al. (2005), thus, undertook a study to elucidate these previously mentioned factors.
Methods
This was a population-based cross-sectional survey carried out between July 2002–January 2003. A total of 1,243 individuals from the ethnic group Ezza were recruited in the study and screened for the presence of W. bancrofti microfilariae (Anosike, et al., 2005). Baseline demographic information was collected from these individuals and night blood specimens were collected to screen for the presence of W. bancrofti microfilariae in the peripheral bloodstream (Anosike, et al., 2005). Moreover, subjects were also questioned about the presence of any clinical signs and symptoms of Filariasis and any previous drug therapy undertaken in this regard (Anosike, et al., 2005). Entomological studies were also performed to determine the common vectors of this disease in the region being studied.
The data hence collected were analyzed to determine the community-wide prevalence of the disease (Anosike, et al., 2005). Moreover, chi-squared tests and regression analysis were also were used in the statistical analysis to determine associations between dependant (microfilarial rate and microfilariae density) and independent variables (age, sex, etc) (Anosike, et al., 2005).
Results
The prevalence of W. bancrofti associated Lymphatic Filariasis was found to be 16.9% in this ethnic subgroup of Nigeria (Anosike, et al., 2005). The prevalence of the infection was observed to increase with age and reached a peak in the fourth decade of life. Moreover, infection rates also varied significantly amongst different communities. There was no association found between gender and susceptibility to infection (Anosike, et al., 2005).
Entomological studies revealed that the most commonly implicated vectors in this region were An. Gambiae, An. funestus and Culex quinquefasciatus (Anosike, et al., 2005). A variety of clinical signs and symptoms of the disease were observed in this population ranging from asymptomatic infections to overt manifestations such as dermatitis, elephantiasis, and hydrocoele (Anosike, et al., 2005). Despite the high prevalence of the disease in this region, most of the patients affected by this disease were deficient in knowledge regarding the etiology of the disease and attributed disease acquisition to witchcraft and consumption of unhygienic food and water (Anosike, et al., 2005).
Discussion
The above-discussed results regarding the trends, prevalence, microfilaria rate, and clinical features of the Lymphatic Filariasis in the Ezza people of the Ebonyi state, Eastern Nigeria are similar to previously conducted studies in this region and also in other regions of the world where this disease is endemic. Worldwide, the prevalence of Lymphatic Filariasis has been shown to increase with increasing age (World Health Organization, 1984; Akogun, 1992). Moreover, this disease has been found to affect both the sexes equally as observed in this study.
Lymphatic Filariasis has been described as a ‘spectral disease’ with a wide range of clinical manifestations (Rajan, 2005; Akogun, 1992) as observed in the above-discussed study population. Patients with Lymphatic Filariasis may be completely asymptomatic or may develop overt signs and symptoms of the disease which can present in either an acute or a chronic form (Palumbo, 2008). Studies have shown that during the asymptomatic stage, patients harbor the nematodes in their bloodstream, and even though there may be an absence of clinical manifestations, subclinical irreversible dilation of the lymphatics has often already taken place especially in those vessels where the adult worms have been found to be living (Palumbo, 2008).
It has been observed that this asymptomatic lymphatic vessel dilation promotes the progression of the disease process and is known to persist even after the infection has been effectively treated and the parasite has been eliminated from the human body (Shenoy, 2008).
There are two major acute manifestations of Lymphatic Filariasis, viz. Acute Adeno-Lymphangitis (ADL) and Acute Filarial Lymphangitis (AFL) (Palumbo, 2008). During ADL patients experience recurrent episodes of fever and lymph node swelling and this is accompanied by gradually worsening lymphedema, especially of the lower extremities, genitalia, and the breasts, over the period of time (Palumbo, 2008). Secondary bacterial infections, in particular, those caused by streptococci have been implicated in the pathogenesis of these episodes (Suma, Shenoy, & Varghese, 1997). On the other hand, AFL is caused mainly by adult filarial worms (Palumbo, 2008). It occurs rarely when the worms either die themselves or as a result of treatment and manifest as lymph node tenderness, nodule formation, and the inflammation of lymphatics (Palumbo, 2008).
Amongst the chronic manifestations of Lymphatic Filariasis, the most common ones are
- Lymphedema, which if left untreated, eventually progresses to Elephantiasis, and
- Genito-urinary lesions (Palumbo, 2008).
Other less common manifestations of this disease include hydrocoele in males, and rarely hydrocoele, chyluria and chylous ascites (Palumbo, 2008; Anosike, et al., 2005). Moreover, pulmonary manifestations, with an increased eosinophil count, and deranged renal function, with microscopic and/or macroscopic hematuria can also occur in rare instances (Palumbo, 2008; Anosike, et al., 2005).
The diagnostic modalities most commonly used in the assessment and determination of the disease include night blood examination which is performed to detect the presence of microfilaria in the bloodstream, antigenic testing using the Immuno-chromatographic-card test (ICT) card test, and ultrasonography which helps in locating the adult worms and assessing the thickness of tissues (Shenoy, 2008). Moreover, Lymphoscintigraphy is used to assess the status and functioning of the lymphatics and any abnormalities such as dilation, valvular incompetence, backflow, and obstructions to the flow can be picked up via this technique (Shenoy, 2008).
In the year 1997, Lymphatic Filariasis was identified as being amongst the six potentially eradicable diseases in the world by the World Health Organization (WHO) (Streit & Lafontant, 2008), and keeping this in view, a global program for the eradication of this disease was formulated and launched in the year 2000 (Shenoy, 2008). Under this Global Programme for Elimination of LF (GPELF), annual mass administration of anti-filarial drugs is undertaken to break the cycle of transmission and infection in endemic areas (Shenoy, 2008). Moreover, this program also aims at reducing the morbidity and the impact of disability amongst affect individuals (Shenoy, 2008).
With regards to the treatment of this condition, the three most commonly used drugs include Diethylcarbamazine (DEC), Ivermectin (IVM), and Albendazole (ALB) (Hoerauf, 2008). The drug of choice for the management of an active infection is Diethylcarbamazine (DEC) (Shenoy, 2008). However, DEC is effective in killing only 50% of the filarial worms and does not have any role in the reversal of the already established lymphatic damage or the treatment of ADL (Shenoy, 2008; Dreyer, Medeiros, Netto, Lea, Gonzaga de Castro, & Peissens, 1999).
For the treatment of ADL, measures such as bed rest, limb elevation, and local applications of antibiotics or antifungals are effective (Shenoy, 2008). Systemic antibiotics including penicillin, doxycycline, ampicillin and amoxicillin, and anti-inflammatory agents can also be used depending on the severity of the disease (Shenoy, 2008).
Thus, Lymphatic Filariasis is a common disease especially in developing nations and regions where poverty prevails. It can present in a variety of ways and its prompt recognition and treatment are important to decrease the prevalence of this disease in endemic regions. Moreover, this disease has been identified as a preventable disease and thus, the development of strategies to combat this disease and to prevent its occurrence is imperative in controlling the global burden of this disease.
References
Akogun, O. (1992). Filariasis in Gongola State Nigeria. I: Clinical and parasitological studies in Mutum-Biyu District. Angew Parasitology , 125-131.
Anosike, J. C., Nwoke, B. E., Ajayi, E. G., Onwuliri, C. O., Okoro, O. U., Oku, E. E., et al. (2005). Lymphatic Filariasis among the Ezza people of the Ebonyi state,Eastern Nigeria. Ann Agric Environ Med , 181-186.
Dreyer, G., Medeiros, Z., Netto, M., Lea, l. N., Gonzaga de Castro, L., & Peissens, W. (1999). Acute attacks in the extremities of persons living in an area endemic for bancroftian filariasis: differentiation of two syndromes. Trans Roy Soc Trop Med Hyg , 413-417.
Hoerauf, A. (2008). Filariasis: new drugs and new opportunities for lymphatic filariasis and onchocerciasis. Current Opinion in Infectious Diseases , 673-681.
Palumbo, E. (2008). Filariasis: diagnosis, treatment and prevention. Acta Biomedica , 106-109.
Rajan, T. V. (2005). Perspective Natural Course Of Lymphatic Filariasis: Insights From Epidemiology, Experimental Human Infections, and Clinical Observations. American Journal of Tropical Medicine and Hygiene , 995-998.
Shenoy, R. K. (2008). Clinical and Pathological Aspects of Filarial Lymphedema and Its Management. Korean Journal of Parasitology , 119-125.
Streit, T., & Lafontant, J. G. (2008). Eliminating Lymphatic Filariasis: A View from the Field. Annals of the New York Academy of Sciences , 53-63.
Suma, T., Shenoy, R., & Varghese, J. e. (1997). Estimation of ASO titer as an indicator of streptococcal infection precipitating acute adenolymphangitis in brugian lymphatic filariasis. South East Asian J Trop Med Pub Health , 826-30.
World Health Organization. (1984). Lymphatic filariasis: Fourth report of the WHO Expert Committee on filariasis. WHO Tech Rep Ser.