Epidemiology And Host Genetic Factors Associated With Bancroftian Filariasis In Endemic Communities Of North Eastern Tanzania

ABSTRACT

Tanzania started a countrywide lymphatic filariasis elimination programme in 2000 adopting the mass drug administration (MDA) strategy. The drugs used for the MDA programme are a combination of ivermectin and albendazole. Clinically, the initial stages of lymphatic filariasis present as an acute febrile conditions with adenolymphangitis (ADL). Later on the disease is characterized by development of scrotal swelling (hydrocele) and swelling of the legs (lymphoedema) which gradually lead to elephantoid oedema. There is limited information on the current epidemiological trend of infections in areas where MDA implementation is ongoing and the immunological markers for early diagnosis of the disease have not been identified. The present study aimed at assessing the current status of bancroftian filariasis infection rate and morbidity in areas where MDA has been administered for over eight rounds as well as the clinical disease presentation and possible human genetic factors associated with disease development. The study was a cross-sectional descriptive study involving 472 individuals (>18 years) from endemic communities in Tanga region in north-eastern Tanzania where MDA has been implemented. Clinical data, socio-demographic survey and circulating filarial antigen (CFA) test was conducted using questionnaire and immuno chromatographic card test according to the manufacturer’s instructions respectively. A total of 76 individuals were tested for the presence or absence of a 23 nucleotide deletion within the 5’ untranslated region of toll like receptor 2 using allele specific real time -polymerase chain reaction (qPCR). A total of 472 individuals were screened: 307/472 (65.1%) of which were males while 165/472 (34.9%) were females. Of those, 272 were recruited for the study of which 87.86% were males and 12.14% were females. The proportion of CFA was 5.51%, that of hydrocoele was 73.2%, and that of lymphoedema was 16.0%. The proportion of hydrocoele combined with lymphoedema was 5.5%. The proportion of individuals with

iii

deletions in their toll like receptor 2 gene was 36.7 %. However, the presence of this deletion within the the TLR 2 gene was not statistically significantly associated with clinical outcome of the disease (P0.05). Our findings demonstrate a considerable low burden in filarial infection. However, there is clear evidence of ongoing transmission despite the 8 rounds of MDA. It is unlikely that the annual MDA would eliminate filarial transmission. The evidence of the presence of TLR 2 deletion genotypes in the 5’ untranslated region was found in individuals who reside in the endemic villages of Tanga region, North Eastern Tanzania, highlighting the potential for the susceptibility of bancroftian filariasis infection. These findings should inform the design of additional strategies to accelerate lymphatic filariasis control and elimination.