Home page  |  About this library  |  Help  |  Clear       English  |  French  |  Spanish  
Expand Document
Expand Chapter
Full TOC
to previous section to next section

close this bookWHO Recommended Surveillance Standards (WHO; 1999; 157 pages)
View the documentAcknowledgements
View the documentAcronyms
View the documentIntroduction
View the documentNational Coordination of Communicable Disease Surveillance
View the documentExplanatory notes
View the documentSurveillance activities: criteria and WHO Department
View the documentCommunicable disease contacts in Regional Offices
close this folderDiseases
View the documentB20-B21-B22-B23-B24 AIDS
View the documentA22 Anthrax
View the documentA23 Brucellosis
View the documentA00 Cholera
View the documentA81.0 Creutzfeldt-Jakob disease
View the documentA90, A91 Dengue fever (A90) including Dengue haemorrhagic fever (DHF) & Dengue shock syndrome (DSS, A91)
View the documentA36 Diphtheria
View the documentB72 Dracunculiasis (Guinea worm disease)
View the documentA98.3, A98.4 Ebola-Marburg viral diseases
View the documentA83.0 Japanese encephalitis
View the documentB74 Lymphatic filariasis
View the documentB96.3 Haemophilus influenzae type b
View the documentB15-B17 Acute viral hepatitis
View the documentB20-B24 HIV infection
View the documentJ10, J11 Influenza
View the documentA96.2 Lassa fever
View the documentA48.1 Legionellosis
View the documentB55.1, B55.2 Cutaneous leishmaniasis
View the documentLeishmania / HIV co-infections
View the documentB55.0 Visceral leishmaniasis
View the documentA30 Leprosy
View the documentA27 Leptospirosis
View the documentB50-54 Malaria
View the documentB05 Measles
View the documentA39 Meningococcal disease
View the documentA87 Viral meningitis
View the documentB73 Onchocerciasis
View the documentA37.0 Pertussis
View the documentA20 Plague
View the documentA36 Poliomyelitis
View the documentA82 Rabies
View the documentA02.0 Salmonellosis
View the documentB65 Schistosomiasis
View the documentA50-52 Syphilis
View the documentA33 Tetanus, neonatal
View the documentB56-0, B56-1 African trypanosomiasis
View the documentB57 American trypanosomiasis
View the documentA15-A19 Tuberculosis
View the documentA75.3 Scrub typhus
View the documentA95.9 Yellow fever
open this folder and view contentsSyndromes
View the documentAnnex 1 Software free and in the public domain
View the documentAnnex 2 Proposed surveillance definitions
View the documentAnnex 3 Role and use of Geographic Information Systems (GIS) and mapping for epidemiological surveillance

B73 Onchocerciasis

(River blindness)


Onchocerciasis is endemic in 34 countries of Africa, the Arabian peninsula and the Americas. Success at controlling the disease in West Africa was achieved through the strategy of larviciding for vector control in order to interrupt transmission; since 1988 this has been combined with treatment by ivermectin, a safe, effective drug. The global strategy for controlling onchocerciasis is based on the yearly administration of ivermectin to affected populations. The first step is to map the endemicity of onchocerciasis in known or potentially endemic areas. The second is to implement cost-effective and sustainable ivermectin delivery, focusing on methods involving community treatment.

Once onchocerciasis is under control (as is currently the case in 11 West African countries), the risk of recrudescence must be kept to a minimum. The participating countries, during the phasing-out period 1998-2002 in West Africa, will ensure that detection and control of onchocerciasis recrudescence are routinely integrated within, and become a routine function of, national disease surveillance and control services.


Clinical case definition

In an endemic area, a person with fibrous nodules in subcutaneous tissues.

Laboratory criteria for confirmation

One or more of the following


• Presence of microfilariae in skin snips taken from the iliac crest

• Presence of adult worms in excised nodules

• Presence of typical ocular manifestations, such as slit-lamp observations of microfilariae in the cornea, the anterior chamber, or the vitreous body

Case classification

Suspected: A case that meets the clinical case definition.

Probable: Not applicable.

Confirmed: A suspected case that is laboratory-confirmed.


In zones where onchocerciasis is endemic:

Active case finding (skin snips, ophthalmological examination, diethylcarbamazine patch test) through surveys. Distribution of the disease can be assessed through rapid epidemiological mapping of onchocerciasis (REMO), a technique developed recently.

In the onchocerciasis-freed zones of West Africa:

Surveillance in sentinel villages:

To detect recrudescence of infection, a minimum of 260 sentinel villages in onchocerciasis-freed zones of West Africa have been kept under periodic surveillance (once every 3 years). They are located near former productive larval breeding sites and had high prevalence rates prior to beginning of control activities.

Routine surveillance:

All suspected cases must be investigated locally, with routine reporting of aggregated data from peripheral level to intermediate and central level. This is not yet fully effective in all of the countries because of insufficient training of health workers.

Migration investigation:

In the event that a positive case is detected in the course of epidemiological surveillance, a migration investigation is systematically carried out in order to identify the origin of infection and take appropriate action.


Individual patient record at peripheral level


• Age, sex, place of infection, treatment (Y/N), date treatment with Ivermectin started, reason for non-treatment (non-compliance)

Aggregated data for reporting


• Prevalence and incidence by age, sex and geographical area
• Community microfilarial load (CMFL)
• Number of cases treated
• Number of cases not treated and reason for non-treatment (pregnancy, breast-feeding, other defaulting)



Graphs: Number of cases by year, geographical area, age group.

Tables: Number of cases by year, geographical area, age group.

Maps: Number of cases by geographical area, using geographical information system (GIS).



• Eliminate onchocerciasis as a disease of public health and socioeconomic importance
• Prevent recrudescence of infection in the onchocerciasis-freed zones
• Assess effectiveness of intervention
• (In West Africa), decide on the cessation of larviciding activities


New diagnostic tests, such as patch test with DEC (diethylcarbamazine citrate), may become suitable for use in the field.


Regional Offices

See Regional Communicable Disease contacts on section "Communicable disease contacts in Regional Offices".

Headquarters: 20 Avenue Appia, CH-1211 Geneva 27, Switzerland

Onchocerciasis Control Programme/African Programme of Onchocerciasis Control

Control Liaison Office (ACP/APOC)


E-mail: daribia@who.ch / Surveillancekit@who.ch
Tel: (41 22) 791 3883/2111
Fax: (4122) 791 4190
to previous section to next section

Please provide your feedback   English  |  French  |  Spanish