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Lymphatic filariasis control in Tanga Region, Tanzania: status after eight rounds of mass drug administration.

Simonsen PE, Derua YA, Magesa SM, Pedersen EM, Stensgaard AS, Malecela MN, Kisinza WN - Parasit Vectors (2014)

Bottom Line: Since then, the current project has monitored the effect in communities and schools in rural areas of Tanga District.LF burdens gradually decreased when moving to districts further inland and with higher altitudes.Monitoring should continue to guide the programme to ensure that the current major achievements will ultimately lead to successful LF elimination.

View Article: PubMed Central - PubMed

Affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Dyrlægevej 100, 1870, Frederiksberg C, Denmark. pesi@sund.ku.dk.

ABSTRACT

Background: Lymphatic filariasis (LF) control started in Tanga Region of Tanzania in 2004, with annual ivermectin/albendazole mass drug administration (MDA). Since then, the current project has monitored the effect in communities and schools in rural areas of Tanga District. In 2013, after 8 rounds of MDA, spot check surveys were added in the other 7 districts of Tanga Region, to assess the regional LF status.

Methods: LF vector and transmission surveillance, and human cross sectional surveys in communities and schools, continued in Tanga District as previously reported. In each of the other 7 districts, 2-3 spot check sites were selected and about 200 schoolchildren were examined for circulating filarial antigens (CFA). At 1-2 of the sites in each district, additional about 200 community volunteers were examined for CFA and chronic LF disease, and the CFA positives were re-examined for microfilariae (mf).

Results: The downward trend in LF transmission and human infection previously reported for Tanga District continued, with prevalences after MDA 8 reaching 15.5% and 3.5% for CFA and mf in communities (decrease by 75.5% and 89.6% from baseline) and 2.3% for CFA in schoolchildren (decrease by 90.9% from baseline). Surprisingly, the prevalence of chronic LF morbidity after MDA 8 was less than half of baseline records. No infective vector mosquitoes were detected after MDA 7. Spot checks in the other districts after MDA 8 showed relatively high LF burdens in the coastal districts. LF burdens gradually decreased when moving to districts further inland and with higher altitudes.

Conclusion: LF was still widespread in many parts of Tanga Region after MDA 8, in particular in the coastal areas. This calls for intensified control, which should include increased MDA treatment coverage, strengthening of bed net usage, and more male focus in LF health information dissemination. The low LF burdens observed in some inland districts suggest that MDA in these could be stepped down to provide more resources for upscale of control in the coastal areas. Monitoring should continue to guide the programme to ensure that the current major achievements will ultimately lead to successful LF elimination.

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Related in: MedlinePlus

Mean monthly transmission potential (MTP) for the main transmission months of May-August for the years of 2004–2013. Only 2 months included for 2012 and 2013 (see Methods).
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Fig3: Mean monthly transmission potential (MTP) for the main transmission months of May-August for the years of 2004–2013. Only 2 months included for 2012 and 2013 (see Methods).

Mentions: Results from the two months of vector and transmission surveillance in the post-MDA 7 and post MDA 8 periods are shown in Table 4, together with findings from the full-time pre-MDA and post-MDA 6 periods. When comparing results, it should be noted that not only the length of collection period differed, but also that the post-MDA 7 and 8 collections were made towards the end of the long rainy season when peak mosquito density was expected. The post-MDA 7 period thus had exceptionally low vector mosquito density, whereas the density was higher in the post-MDA 8 period. The previously reported [16,18] shift in vector composition from being predominantly anophelines during the pre-MDA period to being predominantly Culex quinquefasciatus in the later part of the study was still clearly seen. None of the dissected vector mosquitoes from post-MDA periods 7 or 8 were found to carry filarial infections. The mean MTP for the four main transmission months of May-August for the years 2004 to 2013 is shown in Figure 3 (only 2 months included for 2012 and 2013; see Methods) and indicates a dramatic decrease in transmission during the study period.Table 4


Lymphatic filariasis control in Tanga Region, Tanzania: status after eight rounds of mass drug administration.

Simonsen PE, Derua YA, Magesa SM, Pedersen EM, Stensgaard AS, Malecela MN, Kisinza WN - Parasit Vectors (2014)

Mean monthly transmission potential (MTP) for the main transmission months of May-August for the years of 2004–2013. Only 2 months included for 2012 and 2013 (see Methods).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4233105&req=5

Fig3: Mean monthly transmission potential (MTP) for the main transmission months of May-August for the years of 2004–2013. Only 2 months included for 2012 and 2013 (see Methods).
Mentions: Results from the two months of vector and transmission surveillance in the post-MDA 7 and post MDA 8 periods are shown in Table 4, together with findings from the full-time pre-MDA and post-MDA 6 periods. When comparing results, it should be noted that not only the length of collection period differed, but also that the post-MDA 7 and 8 collections were made towards the end of the long rainy season when peak mosquito density was expected. The post-MDA 7 period thus had exceptionally low vector mosquito density, whereas the density was higher in the post-MDA 8 period. The previously reported [16,18] shift in vector composition from being predominantly anophelines during the pre-MDA period to being predominantly Culex quinquefasciatus in the later part of the study was still clearly seen. None of the dissected vector mosquitoes from post-MDA periods 7 or 8 were found to carry filarial infections. The mean MTP for the four main transmission months of May-August for the years 2004 to 2013 is shown in Figure 3 (only 2 months included for 2012 and 2013; see Methods) and indicates a dramatic decrease in transmission during the study period.Table 4

Bottom Line: Since then, the current project has monitored the effect in communities and schools in rural areas of Tanga District.LF burdens gradually decreased when moving to districts further inland and with higher altitudes.Monitoring should continue to guide the programme to ensure that the current major achievements will ultimately lead to successful LF elimination.

View Article: PubMed Central - PubMed

Affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Dyrlægevej 100, 1870, Frederiksberg C, Denmark. pesi@sund.ku.dk.

ABSTRACT

Background: Lymphatic filariasis (LF) control started in Tanga Region of Tanzania in 2004, with annual ivermectin/albendazole mass drug administration (MDA). Since then, the current project has monitored the effect in communities and schools in rural areas of Tanga District. In 2013, after 8 rounds of MDA, spot check surveys were added in the other 7 districts of Tanga Region, to assess the regional LF status.

Methods: LF vector and transmission surveillance, and human cross sectional surveys in communities and schools, continued in Tanga District as previously reported. In each of the other 7 districts, 2-3 spot check sites were selected and about 200 schoolchildren were examined for circulating filarial antigens (CFA). At 1-2 of the sites in each district, additional about 200 community volunteers were examined for CFA and chronic LF disease, and the CFA positives were re-examined for microfilariae (mf).

Results: The downward trend in LF transmission and human infection previously reported for Tanga District continued, with prevalences after MDA 8 reaching 15.5% and 3.5% for CFA and mf in communities (decrease by 75.5% and 89.6% from baseline) and 2.3% for CFA in schoolchildren (decrease by 90.9% from baseline). Surprisingly, the prevalence of chronic LF morbidity after MDA 8 was less than half of baseline records. No infective vector mosquitoes were detected after MDA 7. Spot checks in the other districts after MDA 8 showed relatively high LF burdens in the coastal districts. LF burdens gradually decreased when moving to districts further inland and with higher altitudes.

Conclusion: LF was still widespread in many parts of Tanga Region after MDA 8, in particular in the coastal areas. This calls for intensified control, which should include increased MDA treatment coverage, strengthening of bed net usage, and more male focus in LF health information dissemination. The low LF burdens observed in some inland districts suggest that MDA in these could be stepped down to provide more resources for upscale of control in the coastal areas. Monitoring should continue to guide the programme to ensure that the current major achievements will ultimately lead to successful LF elimination.

Show MeSH
Related in: MedlinePlus