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Seroprevalence and spatial epidemiology of Lymphatic Filariasis inAmerican Samoa after successful mass drug administration.

Lau CL, Won KY, Becker L, Soares Magalhaes RJ, Fuimaono S, Melrose W, Lammie PJ, Graves PM - PLoS Negl Trop Dis (2014)

Bottom Line: Og4C3 antigen of >128 units (positive) were found in 0.75% (95% CI 0.3-1.6%) of participants, and >32 units (equivocal plus positive) in 3.2% (95% CI 0.6-4.7%).Prevalence was higher in males, and inversely associated with years lived in American Samoa.Strategies to monitor cluster residents and high-risk groups are needed to reduce resurgence risk.

View Article: PubMed Central - PubMed

Affiliation: WHO Collaborating Centre for Children's Health and Environment, Queensland Children's Medical Research Institute, The University of Queensland, Brisbane, Australia; Research School of Population Health, Australian National University, Canberra, Australia.

ABSTRACT

Background: As part of the Global Programme to Eliminate Lymphatic Filariasis (LF), American Samoa conducted mass drug administration (MDA) from 2000-2006, and passed transmission assessment surveys in 2011-2012. We examined the seroprevalence and spatial epidemiology of LF post-MDA to inform strategies for ongoing surveillance and to reduce resurgence risk.

Methods: ELISA for LF antigen (Og4C3) and antibodies (Wb123, Bm14) were performed on a geo-referenced serum bank of 807 adults collected in 2010. Risk factors assessed for association with sero-positivity included age, sex, years lived in American Samoa, and occupation. Geographic clustering of serological indicators was investigated to identify spatial dependence and household-level clustering.

Results: Og4C3 antigen of >128 units (positive) were found in 0.75% (95% CI 0.3-1.6%) of participants, and >32 units (equivocal plus positive) in 3.2% (95% CI 0.6-4.7%). Seroprevalence of Wb123 and Bm14 antibodies were 8.1% (95% CI 6.3-10.2%) and 17.9% (95% CI 15.3-20.7%) respectively. Antigen-positive individuals were identified in all ages, and antibody prevalence higher in older ages. Prevalence was higher in males, and inversely associated with years lived in American Samoa. Spatial distribution of individuals varied significantly with positive and equivocal levels of Og4C3 antigen, but not with antibodies. Using Og4C3 cutoff points of >128 units and >32 units, average cluster sizes were 1,242 m and 1,498 m, and geographical proximity of households explained 85% and 62% of the spatial variation respectively.

Conclusions: High-risk populations for LF in American Samoa include adult males and recent migrants. We identified locations and estimated the size of possible residual foci of antigen-positive adults, demonstrating the value of spatial analysis in post-MDA surveillance. Strategies to monitor cluster residents and high-risk groups are needed to reduce resurgence risk. Further research is required to quantify factors contributing to LF transmission at the last stages of elimination to ensure that programme achievements are sustained.

No MeSH data available.


Related in: MedlinePlus

Prevalence of filarial antigen and antibodies by years lived in American Samoa.
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pntd-0003297-g002: Prevalence of filarial antigen and antibodies by years lived in American Samoa.

Mentions: Antibody and antigen prevalence were inversely associated with the number of years lived in American Samoa (Figure 2 and Table 1). Of all study participants, 68.8% (n = 555) had lived in American Samoa for all of their lives. Compared to individuals who had lived in American Samoa for over 10 years, new migrants who had lived there for <5 years had odds ratios of 13.7 (95% CI: 2.4–78.4) of having Og4C3 antigen of >128 units, and odds ratio of 6.1 (95% CI: 1.9–19.4) of having Og4C3 antigen of >32 units (Table 1). New migrants also had higher prevalence of Wb123 and Bm14 antibodies compared to those who had lived in American Samoa for >10 years, but differences were not statistically significant. The prevalence of antibodies and antigen were higher in residents on the main island of Tutuila compared to those who lived in smaller islands, but differences were not statistically significant. Tuna cannery workers had significantly higher prevalence of Wb123 antibodies, but there were no other associations between occupational groups and seroprevalence. Our study did not find any association between income and seroprevalence.


Seroprevalence and spatial epidemiology of Lymphatic Filariasis inAmerican Samoa after successful mass drug administration.

Lau CL, Won KY, Becker L, Soares Magalhaes RJ, Fuimaono S, Melrose W, Lammie PJ, Graves PM - PLoS Negl Trop Dis (2014)

Prevalence of filarial antigen and antibodies by years lived in American Samoa.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4230933&req=5

pntd-0003297-g002: Prevalence of filarial antigen and antibodies by years lived in American Samoa.
Mentions: Antibody and antigen prevalence were inversely associated with the number of years lived in American Samoa (Figure 2 and Table 1). Of all study participants, 68.8% (n = 555) had lived in American Samoa for all of their lives. Compared to individuals who had lived in American Samoa for over 10 years, new migrants who had lived there for <5 years had odds ratios of 13.7 (95% CI: 2.4–78.4) of having Og4C3 antigen of >128 units, and odds ratio of 6.1 (95% CI: 1.9–19.4) of having Og4C3 antigen of >32 units (Table 1). New migrants also had higher prevalence of Wb123 and Bm14 antibodies compared to those who had lived in American Samoa for >10 years, but differences were not statistically significant. The prevalence of antibodies and antigen were higher in residents on the main island of Tutuila compared to those who lived in smaller islands, but differences were not statistically significant. Tuna cannery workers had significantly higher prevalence of Wb123 antibodies, but there were no other associations between occupational groups and seroprevalence. Our study did not find any association between income and seroprevalence.

Bottom Line: Og4C3 antigen of >128 units (positive) were found in 0.75% (95% CI 0.3-1.6%) of participants, and >32 units (equivocal plus positive) in 3.2% (95% CI 0.6-4.7%).Prevalence was higher in males, and inversely associated with years lived in American Samoa.Strategies to monitor cluster residents and high-risk groups are needed to reduce resurgence risk.

View Article: PubMed Central - PubMed

Affiliation: WHO Collaborating Centre for Children's Health and Environment, Queensland Children's Medical Research Institute, The University of Queensland, Brisbane, Australia; Research School of Population Health, Australian National University, Canberra, Australia.

ABSTRACT

Background: As part of the Global Programme to Eliminate Lymphatic Filariasis (LF), American Samoa conducted mass drug administration (MDA) from 2000-2006, and passed transmission assessment surveys in 2011-2012. We examined the seroprevalence and spatial epidemiology of LF post-MDA to inform strategies for ongoing surveillance and to reduce resurgence risk.

Methods: ELISA for LF antigen (Og4C3) and antibodies (Wb123, Bm14) were performed on a geo-referenced serum bank of 807 adults collected in 2010. Risk factors assessed for association with sero-positivity included age, sex, years lived in American Samoa, and occupation. Geographic clustering of serological indicators was investigated to identify spatial dependence and household-level clustering.

Results: Og4C3 antigen of >128 units (positive) were found in 0.75% (95% CI 0.3-1.6%) of participants, and >32 units (equivocal plus positive) in 3.2% (95% CI 0.6-4.7%). Seroprevalence of Wb123 and Bm14 antibodies were 8.1% (95% CI 6.3-10.2%) and 17.9% (95% CI 15.3-20.7%) respectively. Antigen-positive individuals were identified in all ages, and antibody prevalence higher in older ages. Prevalence was higher in males, and inversely associated with years lived in American Samoa. Spatial distribution of individuals varied significantly with positive and equivocal levels of Og4C3 antigen, but not with antibodies. Using Og4C3 cutoff points of >128 units and >32 units, average cluster sizes were 1,242 m and 1,498 m, and geographical proximity of households explained 85% and 62% of the spatial variation respectively.

Conclusions: High-risk populations for LF in American Samoa include adult males and recent migrants. We identified locations and estimated the size of possible residual foci of antigen-positive adults, demonstrating the value of spatial analysis in post-MDA surveillance. Strategies to monitor cluster residents and high-risk groups are needed to reduce resurgence risk. Further research is required to quantify factors contributing to LF transmission at the last stages of elimination to ensure that programme achievements are sustained.

No MeSH data available.


Related in: MedlinePlus