Application of a GIS in the control of River Blindness
Fred L. Clark, M.Sc., Robert E. Klein, Ph.D, Frank O. Richards Jr., M.D.,
Michael Richards, Ph.D., and Sergio G. García.
Application of a GIS in the control of River Blindness
Authors: Fred L. Clark, M.Sc., Robert E. Klein, Ph.D., Frank O. Richards Jr., M.D., Michael Richards, Ph.D., and Sergio García
Defining Issue: To measure the magnitude and trend of a vector borne disease, onchocerciasis, or River Blindness that can lead to blindness, poses a current challenge to a regional public health initiative in six Latin American countries. The disease is endemic in inaccessible regions of Tropical America, including the Amazon Basin.
GIS solution: The Regional Mapping Center, seated at the Universidad del Valle de Guatemala through support of the Onchocerciasis Elimination Program for the Americas (OEPA), has implemented a GIS to identify suspect communities, program the delivery of medication, measure performance of health workers, and determine impact of treatment.
Application or Methodology: The GIS began with digitizing available maps of the endemic zones, identifying suspect and endemic communities using buffer zones of known vector breeding sites, locating communities with the help of GPS units, producing maps to measure the performance of health brigades in the delivery of medication at the community level, and measuring the endemicity and trend of the disease. This experience and technology have been transferred to the six countries where River Blindness is endemic through the training of key personnel, field work, geo-referencing of communities, and giving them digital maps, software and equipment.
Software: The GIS tool used at the Regional Mapping Center and the endemic countries is Atlas*GIS version 3.0 for windows, databases are in Xbase format, applications for gathering and keeping data are written in FoxPro and EpiInfo. The purpose of the paper is to show that GIS is a powerful tool for managing and modeling public health problems in developing countries where digital maps are almost non existent, access is difficult and funds are scarce.
The Onchocerciasis Elimination Program for the Americas (OEPA), is a non for profit joint initiative of the Global 2000 River Blindness Program of the Carter Center, the Pan American Health Organization and the Ministries of Health of the six countries where onchocerciasis is endemic. With partial funding from a grant from the Inter American Development Bank, OEPA founded the Regional Mapping Center at Universidad del Valle de Guatemala in Guatemala City, Guatemala.
Introduction
Onchocerciasis or River Blindness is a parasitic disease produced by a filarial worm known as Onchocerca volvulus. The infection is through the bite of a vector; a blackfly of the Simulium genus. The clinical manifestations are ocular and dermatological. If untreated, onchocerciasis can cause blindness and other visual complications. The treatment of choice is Ivermectin, donated to the Programs by Merck & Co. through the Mectizan® Donation Program.
River Blindness is endemic in six countries in the Americas (Brazil, Colombia, Ecuador, Guatemala, Mexico, and Venezuela). It affects an estimated 131 thousand people in 1,660 communities. There are 3,300 suspect communities pending epidemiological evaluation. The population at risk is over 1.6 million people, living in an area of 247,543 square kilometers ( 95,571 square miles). The following map shows the distribution of Onchocerciasis in the Americas.
The beginning
The GIS initiative began in Guatemala in 1988. Retrospective data on nodulectomies (surgical removal of an onchocercoma) from the 10 previous years was gathered at the Ministry of Health in Guatemala. Maps from 3 departments located in the central focus were digitized. The scale of these maps was 1:50,000. Communities were geo-referenced using hand held GPS units (Sony, Trimble, Magellan). A five kilometer buffer zone was indicated on these maps around the fly's breeding sites in mountain streams. This represents the flight range of the vector. Endemic communities located within this zone were indicated, as were those suspect communities awaiting future evaluations. Hyper-endemic communities were found to be located within this buffer zone.
Altitude is an additional criteria used as a risk factor indicator. It was thus plotted on the maps. Hyper and meso-endemic communities were invariably located between 500 and 1,500 meters of altitude (1,500 to 4,500 feet range).
The combination of breeding sites identification and the registry of altitude on the maps helped us narrow down our stratification process. The following map illustrates the buffers and altitude range.
By using field data from the programmatic aspect of the project in our base maps, we were able to show effectiveness of the Health Brigades in the delivery of Ivermectin to the community, to emphasize the treatment of those communities with fewer number of treatments, and those with low treatment coverage. GIS was used not only as an analytical tool for epidemiological purposes, but for managing the project. Below is a map showing the outcome of treatment rounds between 1990 and 1994.
The Regional Project
In September 1990, the XXIII Pan American Sanitary Conference called for the identification of diseases that might be eliminated near the turn of the century. The Conference, resolved to establish the mechanisms toward the elimination of Onchocerciasis, among other diseases. In 1992 the River Blindness Foundation (RBF) granted the first seed money towards establishing a program in the Americas, and procuring more financial aid. The following year the Onchocerciasis Elimination Program for the Americas (OEPA) was established. OEPA is a not-for-profit regional initiative financed mainly by a non-reimbursable grant from the Inter American Development Bank, originally coordinated by RBF and currently the Global 2000 River Blindness Program of the Carter Presidential Center. The six endemic countries of the Americas form a partnership with OEPA to eliminate the disease by the year 2007.
In 1995, the Regional Mapping Center was established at the Universidad del Valle de Guatemala. With the support of OEPA, the RMC has implemented a regional GIS to identify suspect communities, program the delivery of Ivermectin®, measure performance of health workers, and determine impact of treatment.
The experience gathered in the early stage of the project proved to be an enormous advantage when GIS was introduced at a regional level. First, paper maps of adequate scale were collected in every country, then digitized at the RMC, communities were geo-referenced, and community data were gathered, entered, and maintained. To assure compatibility, community data is kept in Xbase format. Later, the first thematic maps, like the two maps shown below, were produced and displayed at the Inter American Conference on Onchocerciasis.
In the last quarter of 1996, a regional workshop in the use of Atlas GIS for Windows, our GIS tool, took place in Guatemala. There, participants were trained on GIS Fundamentals, digitizing, production of thematic maps, database management, data operations and security, geo-reference of communities, and production of thematic maps. Trainees received digital maps of their endemic areas, laptop computers, hand held GPS units, a 12"x12" digitizer table, digital storage units, and Atlas*GIS for Windows V.3.1. Below is a sample of one of the digital maps given to the participants.
The authorities of the National Programs in the six countries have a strong interest in GIS. For calendar year 1997, they have requested over US$50,000.00 in equipment and maps to improve their GIS capabilities. Our partners in the six countries will help us in this stage of the project, assure the quality of the maps through field work, and to increase the coverage of maps. Below is a map that will be updated with the cooperation of field staff.
Conclusion
The low cost, ease of use and friendly user interface of Atlas*GIS for Windows, and low training period has contributed enormously to the successful replication at the regional level of the work previously done in Guatemala. Atlas*GIS for Windows has provided the tools to manage and model this public health problem. This experience can be replicated to almost any health problem in any developing country with a minimum investment.
Acknowledgments
The authors wish to thank the National Onchocerciasis Elimination and Control Programs of the six endemic countries, Global 2000 River Blindness Program of the Carter Presidential Center, Onchocerciasis Elimination Program for the Americas, Regional Mapping Center of the Medical Entomology Research and Training Unit of the Centers for Disease Control and Prevention, and the Universidad del Valle de Guatemala for their cooperation.
Authors
Fred L. Clark, M.Sc.
Long Term Consultant in Health MIS and GIS
Onchocerciasis Elimination Program for the Americas
8424 NW, 56th St. #570
Miami, FL 33166
Telephone: 011-502-366-6106 to 09
Fax: 011-502-366-6127
fclark@hotmail.com
Robert E. Klein, Ph.D.
Director
Medical Entomology Research and Training Unit
USEMB/HHS/MERTU
Unit 3321, APO AA 34024
Miami, FL
Telephone: 011-502-364-0336 to 40 x315
Fax: 011-502-364-0354
rekz@ciddpd3.em.cdc.gov
Frank O. Richards Jr. M.D.
Deputy Director
Global 2000 River Blindness Program
The Carter Center
One Copenhill
453 Freedom Highway
Atlanta, GA 30307
Telephone: (770)-488-4511
Fax: (770)-488-4521
fxr1@ciddpd2.em.cdc.gov
Michael F. Richards, Ph.D.
Research Associate
Universidad del Valle de Guatemala
18 avenida 11-37 zona 15, V.H. III
Ciudad de Guatemala, Guatemala 01015
Telephone: 011-502-364-0336 to 40 x313
Fax: 011-502-364-0354
richards@gca1.citel.com.gt
Sergio G. García
Jefe del Centro Regional de Mapeo
Universidad del Valle de Guatemala
18 avenida 11-37 zona 15, V.H. III
Ciudad de Guatemala, Guatemala 01015
Telephone: 011-502-364-0336 to 40 x337
Fax: 011-502-364-0354
sggz@ciddpd3.em.cdc.gov