Guide to detecting a potential recrudescence of onchocerciasis during the posttreatment surveillance period: the American paradigm

Figures & data

Figure 1 Four stages of evaluation of onchocerciasis transmission and subsequent action leading to application for certification of elimination.⁶

Table 1 Schedule of activities toward the elimination of onchocerciasis

Treatment phase	Treatments started
	– Baseline and programmatic evaluations (every 4 years) showing positivity of major indicators (clinical [nodules] parasitological [mf], ophthalmological [MfAC, MfC], and entomological [L3])
	Transmission ongoing
	– Infective stage O. volvulus larvae found in vectors (heads) and children < 5 years old with mf in skin, nodules, and serologically positive
	Transmission suppressed
	– Evaluations begin to show negative results
	– Evaluations are initiated to demonstrate that transmission has been interrupted in the focus
	Transmission interrupted
	– Transmission considered interrupted following negative entomological results
	– Complete documentation to corroborate negative results
	– PCC reviews available entomological data with government representatives
	– PCC issues written recommendation to government to stop treatment
	– Government accepts recommendations
Posttreatment surveillance	Transmission interrupted
	– Program conducts health education about the reason for halting treatments within the respective focus area
	– PTS implemented for a 3-year period and evaluations conducted
	– PCC reviews results from evaluations corresponding to the PTS period
	– New confirmation (recommendation) that elimination has occurred if data support this recommendation
	– When elimination is confirmed in the last focus in the country, PCC recommends that the government request initiation of the PAHO/WHO certification process
	– OEPA assists country in developing dossier to submit to PAHO/WHO for the certification process
	– Results leading to “stop treatment” decision are published in a peer-reviewed journal
Certification of elimination	Transmission eliminated
	– Country to formally write PAHO/WHO and request certification
	– PAHO/WHO forms an independent international team to review the data in the field
	– PAHO/WHO grants final certification (whole country only)
	Final certification of Elimination of Transmission by the WHO

Abbreviations: mf, microfilariae; MfAC, microfilariae in the anterior chamber of the eye; MfC, microfilariae in the cornea; PCC, program coordinating committee; PTS, posttreatment surveillance; PAHO, Pan American Health Organization; WHO, World Health Organization; OEPA, Onchocerciasis Elimination Program for the Americas.

Figure 2 Sequential steps in the evolution of onchocerciasis recrudescence.

Abbreviations: Mf, microfilariae; Ov-16, recombinant antigen of O. volvulus; PCR, polymerase chain reaction.

Figure 3 Posttreatment surveillance decision tree for the detection, confirmation, and response to a potential recrudescence event.

Abbreviations: ATP, annual transmission potential; PCR, polymerase chain reaction; STP, seasonal transmission potential.

World Health OrganizationGuidelines: Certification of elimination of human onchocerciasis: criteria and procedures2001GenevaWHO/CDS/CPE/CEE/200118b http://whqlibdoc.who.int/hq/2001/WHO_CDS_CPE_CEE_2001.18b

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