Comparison of serological and parasitological assessments of Onchocerca volvulus transmission after 7 years of mass ivermectin treatment in Mexico.
OBJECTIVE
To compare the utility of an ELISA using 3 recombinant antigens with that of the skin biopsy to estimate incidence of infections in a sentinel cohort of individuals living in an endemic community in southern Mexico during a set of 11 subsequent ivermectin treatments.


RESULTS
The apparent community prevalence of infection and microfilarial skin infection before and after 11 treatments with ivermectin plus nodulectomy were 78% and 13%, and 0.68 mf/mg and 0.04 mf/mg, respectively, as measured by skin biopsy. Of a group of 286 individuals participating in all surveys, a sentinel cohort of 42 mf and serologically negative individuals had been followed since 1994. The annual percentage of individuals becoming positive in this cohort was 24% (10/42), 28% (9/33), 0%, and 4.3% (1/23) in 1995, 1996, 1997 and 1998, respectively. Likewise, the incidence in children 5 years and under (n = 13) within this sentinel cohort was 15% (2/13), 18% (2/11), 0% and 11% (1/9), respectively. All individuals became positive to both tests simultaneously, indicating that seroconversion assessed infection incidence as accurately as skin biopsy in the sentinel group.


CONCLUSIONS
Incidence monitoring of a sentinel cohort provides an estimation of the parasite transmission in the community; it is less costly than massive sampling, and a finger prick blood test might be more acceptable in some communities.
Rodríguez-Pérez
M A
MA
Centro de Investigaciónes sobre Enfermedades Infecciosas, Instituto Nacional de Salud Pública, Cuernavaca, México. mrodriguez@insp3.insp
Danis-Lozano
R
R
Rodríguez
M H
MH
Bradley
J E
JE
D000293:Adolescent; D000328:Adult; D000818:Animals; D000909:Antibodies, Helminth / Q000097:blood; D000947:Antigens, Helminth / Q000276:immunology; D000977:Antiparasitic Agents; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D019353:Endemic Diseases; D004797:Enzyme-Linked Immunosorbent Assay; D005369:Filaricides / Q000627:therapeutic use*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007559:Ivermectin / Q000627:therapeutic use*; D008137:Longitudinal Studies; D008800:Mexico / Q000453:epidemiology; D008842:Microfilariae / Q000187:drug effects / Q000302:isolation & purification; D017181:Onchocerca volvulus / Q000187:drug effects / Q000276:immunology / Q000302:isolation & purification*; D009855:Onchocerciasis / Q000188:drug therapy* / Q000453:epidemiology / Q000469:parasitology / Q000635:transmission*; D011994:Recombinant Proteins / Q000276:immunology; D012867:Skin / Q000469:parasitology; D012876:Skin Diseases, Parasitic / Q000469:parasitology / Q000635:transmission
D000909:Antibodies, Helminth; D000947:Antigens, Helminth; D000977:Antiparasitic Agents; D005369:Filaricides; D011994:Recombinant Proteins; D007559:Ivermectin