The inference of immunochromatographic test, microscopy and polymerase chain reaction in diagnosis of lymphatic filariasis in Tana Delta, Kenya
Kagai, James Mwaniki
MetadataShow full item record
The current diagnostictests for Wuchereriabancrofti infections are insensitive and logistically unsuitable in epidemiological studies and disease surveillance. Although needing refinement, potentially sensitive polymerase chain reaction (PCR) assays have been developed. The suitability of these assays as molecular epidemiological and surveillance tools has not been extensively studied. These assays can be used to estimate disease indices, such as vector infection rate and are important in estimation of the infection pattern in the suspect areas. The main objective of this work was to study W. bancrofti infections in an identified population in the Tana Delta district, using modified molecular assays. The Tana delta, situated along the Kenyan north coast lies in a potentially lymphatic filariasis endemic region but no data on the disease has been documented. This study improved and evaluated PCR assays in monitoring of W. bancrofti infections in humans and the vectors in the Tana Delta. Samples which included, blood, sputum and urine were collected from consenting participants along with mosquitoes which were collected from their homes. The mosquitoes were identified and examined for W. bancrofti infections. Observations from the study indicated that PCR assays had sensitivity and specificity above 84%. This study demonstrated that the W. bancrofti infections exist in the Northern part of the Kenyan coast with prevalence of 6.4% to 9.6% using traditional diagnostic tests and PCR assays respectively. The prevalence of W. bancrofti in mosquito vectors was 1.0% microfilariae by dissection and 1.6% by PCR mosquito assay. A relationship between LF prevalence in the population and vector prevalence was observed. Through a calculation of a factorש (Hebrewshin), the relationship could enable projection of LF prevalence in the population from the determined vector prevalence. The study suggests that this factor ש would be directly proportional to the disease prevalence in the population (p=0.005). By using the modified PCR assays which are both sensitive and specific (p<0.005), an end point (denoted as a prevalence of 0.1%) for the mass drugs administration (MDA) can be determined. The age group 11-20 years was found to be more enthused in participating in the study, with the best turn out of 31% compared to all other age groups (p=0.001). This group had the highest lymphatic filariasis prevalence too. The results from sputum and urine are comparable, suggesting that either of these samples may be used in LF surveillance studies. It is observed that whereas the molecular methods are sensitive and specific, the cost involved is high. The study therefore recommends the use of PCR assays in determination of end-point for MDA. Further, it is recommended that where a survey of lymphatic filariasis is required; 11-20 age group be used to represent the community.