Interruption of Infection Transmission in the Onchocerciasis Focus of Ecuador Leading to the Cessation of Ivermectin Distribution

Introduction: A clinically significant endemic focus of onchocerciasis existing in Esmeraldas Province, coastal Ecuador has been under an ivermectin mass drug administration program since 1991. The main transmitting vector in this area is the voracious blackfly, Simulium exiguum. This paper describes the assessments made that support the decision to cease mass treatment. Methodology and Principle Findings: Thirty-five rounds of ivermectin treatment occurred between 1991–2009 with 29 of these carrying >85% coverage. Following the guidelines set by WHO for ceasing ivermectin distribution the impact on parasite transmission was measured in the two vector species by an O-150 PCR technique standard for assessing for the presence of Onchocerca volvulus. Up to seven collection sites in three major river systems were tested on four occasions between 1995 and 2008. The infectivity rates of 65.0 (CI 39–101) and 72.7 (CI 42–116) in 1995 dropped to zero at all seven collection sites by 2008. Assessment for the presence of antibodies against O. volvulus was made in 2001, 2006, 2007 and 2008 using standard ELISA assays for detecting anti-Ov16 antibodies. None of total of 1810 children aged 1–15 years (between 82 and 98% of children present in the surveyed villages) tested in the above years were found to be carrying antibodies to this antigen. These findings were the basis for the cessation of mass drug treatment with ivermectin in 2009. Significance: This fulfillment of the criteria for cessation of mass distribution of ivermectin in the only known endemic zone of onchocerciasis in Ecuador moves the country into the surveillance phase of official verification for national elimination of transmission of infection. These findings indicate that ivermectin given twice a year with greater than 85% of the community can move a program to the final stages of verification of transmission interruption.     

Onchocerciasis in Minnesota cattle.

Umbilical hides from 536 dairy cattle in Minnesota were tested for the microfilarial stage of Onchocerca species to determine the distribution of onchocerciasis in the state. The infection was widespread as microfilariae were obtained from 214 (40%) of the animals, representing nearly all areas of the state. Adult Onchocerca parasites were collected primarily from nodules associated with tibial bones but also were found to a lesser extent within the gastrosplenic ligament. Specific identity of these organisms is unclear as they exhibit certain morphological features previously described as being characteristic of either Onchocerca gutturosa, Onchocerca lienalis, or Onchocerca stilesi.     

Onchocerciasis in Canada

The first two cases of onchocerciasis seen in Canada are reported. The patients had come from West Africa to study in Canada several months prior to admission to hospital. The presenting symptom in each case was intense pruritus. One of the patients had early ocular involvement. The diagnosis was made by means of microscopic examination of a skin snip. The subcutaneous nodule excised from one of the patients showed the adult Onchocerca volvulus. Both patients also had urinary schistosomiasis. The clinical features, laboratory findings, treatment and public health aspects of onchocerciasis are discussed.     

Mass Administration of Ivermectin for the Elimination of Onchocerciasis Significantly Reduced and Maintained Low the Prevalence of Strongyloides stercoralis in Esmeraldas,Ecuador

Objectives

To evaluate the effect of ivermectin mass drug administration on strongyloidiasis and other soil transmitted helminthiases.

Methods

We conducted a retrospective analysis of data collected in Esmeraldas (Ecuador) during surveys conducted in areas where ivermectin was annually administered to the entire population for the control of onchocerciasis.Data from 5 surveys, conducted between 1990 (before the start of the distribution of ivermectin) and 2013 (six years after the interruption of the intervention) were analyzed. The surveys also comprised areas where ivermectin was not distributed because onchocerciasis was not endemic.Different laboratory techniques were used in the different surveys (direct fecal smear, formol-ether concentration, IFAT and IVD ELISA for Strongyloides stercoralis).

Results

In the areas where ivermectin was distributed the strongyloidiasis prevalence fell from 6.8% in 1990 to zero in 1996 and 1999. In 2013 prevalence in children was zero with stool examination and 1.3% with serology, in adult 0.7% and 2.7%.In areas not covered by ivermectin distribution the prevalence was 23.5% and 16.1% in 1996 and 1999, respectively. In 2013 the prevalence was 0.6% with fecal exam and 9.3% with serology in children and 2.3% and 17.9% in adults.Regarding other soil transmitted helminthiases: in areas where ivermectin was distributed the prevalence of T. trichiura was significantly reduced, while A. lumbricoides and hookworms were seemingly unaffected.

Conclusions

Periodic mass distribution of ivermectin had a significant impact on the prevalence of strongyloidiasis, less on trichuriasis and apparently no effect on ascariasis and hookworm infections.     

Skeletal evidence for kneeling in prehistoric Ecuador.

Bony changes on the superior distal surface of the metatarsals and the superior proximal surface of the first proximal foot phalanx are described in a prehistoric skeletal sample from Coastal Ecuador. The location and morphology of the alterations, as well as their association with femoral "squatting facets" strongly suggests they were produced by prolonged hyperdorsiflexion of the toes, probably resulting from habitual kneeling posture. Comparative data are presented from five other New World skeletal samples.