Onchocerciasis in Ecuador: infection in children in the Santiago Basin focus, Province of Esmeraldas

Abstract

The prevalence of onchocerciasis infection in children aged 1-12 in the Santiago Basin focus, province of Esmeraldas, Ecuador, was determined to see if active transmission of the disease had occurred in the past 6 years. An infection rate of 45.0% was found. Compared to that found in 1980 (14.5%), the infection rate had increased by 210.1%. The increase was greater on the Rio Santiago (340.5%) than on the Rio Cayapas (195.5%). An increase of 286% was seen in the skin microfilarial density in the 1-4 year age group, with a 56.8% increase in the 5-12 year age group. The prevalence of infection in children aged 0-4 years (those born since the first enquiry in 1980) was 64.3%, with an average skin microfilarial density of 12.2 microfilariae (mf)/mg and with 20% presenting nodules, of which 92.1% occurred in the head region. Of the 34 children examined aged less than one year, 25 (73.5%) were positive for microfilariae with an average microfilarial skin density of 9.6 mf/mg. These data suggest that there is active transmission of the disease in the Santiago Basin onchocercal foci.

Simuliidae and the transmission and control of human Onchocerciasis in Latin America

“…unarmed cibaria and high host and vector capacities occur recrudescence may be rapid even if parasite densities are low. Evidence for this hypothesis comes from recent work in Ecuador where Guderian et al (1988) showed that the disease moved from hypoendemicity to mesoendemicity in six years at a locality where the Cayapa cytospecies of S. exiguum was shown to have high host and vector capacities Shelley et al, 1986, in press b). Conversely, species with armed cibaria do not produce significant changes in hypoendemic areas and only show high vector capacities if biting rates and parasite levels are high.…”

“…This is currently the most important focus in South America with recent parasitological surveys (Guderian et al, 1988) showing increasing prevalence rates and skin densities of O. volvulus. Simulium exiguum Cayapa and Aguarico forms are the primary vectors in hyperendemic areas of the main Santiago focus and the Cayapa form in the peripheral mesoendemic Canandé focus Shelley et al, 1986).…”

Human Onchocerciasis and Tetanus Vaccination: Impact on the Postvaccination Antitetanus Antibody Response

“…The definition of whether an O. volvulus-infected subject had acute or chronic infection was based on the mean parasite burden over the observation period. Since transmission is likely to be unstable in the Rio Cayapas region (13,14), we chose a relatively low microfilarial intensity to distinguish between light and heavy infections, with Ͻ5 mf/mg representing light or acute infection and Ͼ5 mf/mg representing heavy or chronic infection. Despite the crudeness of this approach, we were able to detect real differences in the antitetanus antibody responses between the two infection groups.…”

Treatment of Pregnant Women with Ivermectin during Mass Drug Distribution: Time to Investigate Its Safety and Potential Benefits

“…The study compared the incidence rates of spontaneous abortions between onchocerciasisendemic and non-endemic areas. Between 1982 and 1989, a marked increase in spontaneous abortions of 9.5/1000 maternal years at risk (myar) was observed in the onchocerciasisendemic area and was associated with an increase in community O. volvulus microfilarial (mf) load, potentially related to the El Niño climatic phenomenon, which resulted in a marked increase in rainfall and the blackfly population [25]. In the same period, the incidence rate of spontaneous abortions in the non-endemic area was 1.3/1000 myar.…”