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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 age groups, American Samoa 2010.
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pntd-0003297-g001: Prevalence of filarial antigen and antibodies by age groups, American Samoa 2010.

Mentions: Table 1 provides a summary of the associations between demographic variables and the presence of LF antigen and antibodies. Our results show that both antigen and antibody prevalence were higher in males compared to females (Table 1). Figure 1 shows the age distribution of participants, and the prevalence of antigen (Og4C3>128 and Og4C3>32) and antibodies (Wb123 and Bm14) in each age group. Antigen-positive individuals were identified in all age groups, with no significant difference between ages. Prevalence of both Wb123 and Bm14 antibodies were higher in the older age groups. In participants aged 30 years and older, Bm14 prevalence was two to three times higher than Wb123 prevalence in all age groups.


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 age groups, American Samoa 2010.
© Copyright Policy
Related In: Results  -  Collection

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

pntd-0003297-g001: Prevalence of filarial antigen and antibodies by age groups, American Samoa 2010.
Mentions: Table 1 provides a summary of the associations between demographic variables and the presence of LF antigen and antibodies. Our results show that both antigen and antibody prevalence were higher in males compared to females (Table 1). Figure 1 shows the age distribution of participants, and the prevalence of antigen (Og4C3>128 and Og4C3>32) and antibodies (Wb123 and Bm14) in each age group. Antigen-positive individuals were identified in all age groups, with no significant difference between ages. Prevalence of both Wb123 and Bm14 antibodies were higher in the older age groups. In participants aged 30 years and older, Bm14 prevalence was two to three times higher than Wb123 prevalence in all age groups.

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