Mapping of Bancroftian Filariasis in Cameroon: Prospects for Elimination

Abstract

BackgroundLymphatic filariasis (LF) is one of the most debilitating neglected tropical diseases (NTDs). It still presents as an important public health problem in many countries in the tropics. In Cameroon, where many NTDs are endemic, only scant data describing the situation regarding LF epidemiology was available. The aim of this study was to describe the current situation regarding LF infection in Cameroon, and to map this infection and accurately delineate areas where mass drug administration (MDA) was required.MethodologyThe endemicity status and distribution of LF was assessed in eight of the ten Regions of Cameroon by a rapid-format card test for detection of W. bancrofti antigen (immunochromatographic test, ICT). The baseline data required to monitor the effectiveness of MDA was collected by assessing microfilariaemia in nocturnal calibrated thick blood smears in sentinel sites selected in the health districts where ICT positivity rate was ≥ 1%.Principal findingsAmong the 120 health districts visited in the eight Regions during ICT survey, 106 (88.3%) were found to be endemic for LF (i.e. had ICT positivity rate ≥ 1%), with infection rate from 1.0% (95% CI: 0.2–5.5) to 20.0% (95% CI: 10–30). The overall infection rate during the night blood survey was 0.11% (95% CI: 0.08–0.16) in 11 health districts out of the 106 surveyed; the arithmetic mean for microfilaria density was 1.19 mf/ml (95% CI: 0.13–2.26) for the total population examined.Conclusion/significanceICT card test results showed that LF was endemic in all the Regions and in about 90% of the health districts surveyed. All of these health districts qualified for MDA (i.e. ICT positivity rate ≥ 1%). Microfilariaemia data collected as part of this study provided the national program with baseline data (sentinel sites) necessary to measure the impact of MDA on the endemicity level and transmission of LF important for the 2020 deadline for global elimination.

Mapping lymphatic filariasis in Loa loa endemic health districts naïve for ivermectin mass administration and situated in the forested zone of Cameroon

“…7 Helen Keller International, New York, NY, USA. 8 RTI International, Washington, DC, USA. 9 Helen Keller International, Regional Office for Africa, Dakar, Senegal.…”

“…In the northern zone (two regions), which were not endemic for loiasis, W. bancrofti microfilaremia was confirmed microscopically using night blood smears [2]. In the southern part (8 regions) endemic for loiasis, LF was mapped based on the positivity of the immunochromatographic test (ICT) [8]. A total of 158 health districts in Cameroon were previously identified as endemic for LF.…”

“…A total of 158 health districts in Cameroon were previously identified as endemic for LF. About 134 HDs were eligible for LF MDA following completion of epidemiological mapping and based on historical data [2,8]. The other 24 health districts not eligible for MDA were later on carved out into 31 health districts by the health authorities and they were highly endemic for loiasis.…”

Positivity of Antigen Tests Used for Diagnosis of Lymphatic Filariasis in Individuals Without Wuchereria bancrofti Infection But with High Loa loa Microfilaremia

“…Furthermore, the presence of CFA is not always corroborated by W. bancrofti microfilaremia 3. Moreover, there have been several instances in which CFA positivity has been associated with Loa loa microfilaremia 4–6.…”

Mapping lymphatic filariasis in Loa loa endemic health districts naïve for ivermectin mass administration and situated in the forested zone of Cameroon.

“…In the northern zone (two regions), which were not endemic for loiasis, W. bancrofti microfilaremia was confirmed microscopically using night blood smears [3]. In the southern part (8 regions) endemic for loiasis, LF was mapped based on the positivity of the immunochromatographic test (ICT) [7]. A total of 158 health districts in Cameroon were previously identified as endemic for LF.…”