Expert Advisory Committee: thirteenth session: Ouagadougou, 8-12 June 1992: recrudescence and passive surveillance

WORLD HEALTH ORGANIZATION ORGAMSATION MONDIALE DE LA SANTE ONCHOCERCIASIS CONTROL PROGRAMME IN WEST AFRICA pRocRAMME DE LUTTE CONTRE L'ONCHOCERCOSE EN AFRIQUE DE L'OUEST EXPERT ADVISORY COMMITTEE Thirteenth session Ouaeadoueou. 8-12 June 1992 ocP/EAcr3.2 ENGLISH ONLY RECRUDESCENCE AND PASSIVE SURVEILLANCE In the initial OCP areas that have had successful and conplete interruption of vector control for the prescribed duration of 14 years, the prevalence of onchocercal infection is either zero or near zero. The incidence of infection as determined in children (0-15 years ) born sincethe vector control activities started is also zero. Such areas would be appropriately placed under epidemioiogical surveillance for the detection of possible recrudescence of onchocerciasis as confirmed by the presence of nen cases (Incidence). In the main, the detection of the occurrence of any such new cases, to be reasonably complete, would have to be based on active surveillance activities. This could be supplemented with passive surve i I lance. Passive surveillance activities alone wiII not be an appropriate means to the detection of the presence of recrudescence. This is becauseit is limited in coverage and very selective in nature by virtue of being carried out at fixed centres, where the attendance is entirely at thediscretion of the individual. Furthermore the detection nay not, be directed to the right group i.e the at risk groups. There is also thepossibility of recrudescence being detected rather late if the det,ectionis based on clinical manifestations. There is however an important and useful role of passive surveillance in the detection of recrudescence although its place ma."- be minimal. The usefulness of this means of detection of recrudescence could be envisaged as supplementarJ- to the active surveillance. In this regard passive surveillance will be seen to serve these roles; a) the detection of cases which might have been absent during the active survel' and b) the detection of cases rhich might present themselves during the long intervals (3 :rears) between the active surveys. Detection of new cases throuAh oassive surveillance In the context of passive surveillance, the presence of recrudescence of onchocerciasis will have to be discovered through the examination of individuals presenting themselves at their own will to health institutions. The initial diagnosis of onchocerciasis witl be presumptive, based on the history and certain clinical uanifestations. In contrast to active surveillance where certain villages a,re or would have been chosen to serve as indicator viIIages, aIl fixed centres/health institutions in the entire area freed of the infection and at high risk of recrudescence of onchocerciasis would be specially instructed to look for the possible presence of "cases " of onchocerciasis. The need for earll' discovery of the emergence of recrudescencedictates that only the early clinical manifestations of onchocerciasis will be useful in passive the foI lowing: I ) Synotoaq i ) pruritus, ocP/EACLr.2 -2 - surveillance. Thus, emphasis wiII be placed on i i ) history of skin chang-es of recent onset and iii) residentiai historl' from a previousll' oncho endemic are&. lll lraLiertts who give a history suggeslive of orrchocerciasis, or thehealth personnel suspect might be onchocercal cases would need to beittvestigated. 1n suclt suspected individuals it wiII be esgential to obtain a full history of their movements. In this respect the followinginformation will be collected: i ) Whether the individual is a new resident in the area i i ) I f so duration of staf in the area, previous residence to includethe exact place, r.iliage if possible or nearest town and rii) ir ) duration of stay at his or her last residence If an individual has stayed at several places, the places are recorded in stages by order of their duration In a sitr:ation where the individual is a regular resident in the village or area, a migration historl- wiII be taken to enqui re about the rn<lividual's movement out of the area concernecl. 2 ) CI in ical oanifestations i ) Scratch marks, excoriations, crusts ancl ulceration i t ) urt icar iaiir ) skin rash - papules, maculesit') oedema. The cases that are diagnosed either presumptively or on the evitlence of the clinical features shoulcl be confirmed by parasitological examination and/or immunological means if this becomes available. At present the parasitological diagnosis is based on the presence of microfilaria in the skin snip. cognisance is taken of the relativeinsensitivit]'of this method in ven'Iight infections, the IikeIy scenariothat ma1'be obtained in an area previously cleared of the infection. Itis hoped that immunological diagnosis will become a reality soon as welI as simple enouglt to be carried oub at such health centres. Furthermore the dangers of passing on HIV infection through the skin snip method wiIl needto be addressed. In this respect a revision of the sterilization method has been done. Sterilization r.riII be based on the simple method ofboilitrq the corneo-scleral punches for 20 minutes as recommended in Lhe revised trHO guidelines for sterilization, ( 1gBg). Personnel for _pg_ss_iv_e__Suryeil Lanqe for recrudescence clver the J-ears OCP has trained a collection of individuals uho form, ocP/tiAclr.2 - 3- at present, the national epidemiological teams. These national teams have hitherto undertaken epidemiological evaluations in their respecLive countries and are faniliar with the clinical diagnosis of onchocerciasis. Certain members of the team are placed in health centres in the areas where the risk of onchocerciasis is highest. For such health centres such individuals would spearhead the passive surveillance activities. hhere such individuals do not exist, staff stationed in these areas should be given the trairring required to enable them make the initial clinical diagnosis. Furthermore the st.aff at these centres will be reminded from time to time, about the need Eo look for possible onchocerciasis cases. The parasitological diagnosis will be done by the technicians usually available at such health centreg. Record-keepina and transrission of data An efficient record-keeping system including sufficient details on inmigrants will need to be kept at the various health institutions r{ithin the areas earmarked for surveillance activities. -{ny detected cases recorded wiII have to be reported to the national onchocerciasis surveillance unit /centre through clearly defined channels of conmunication. Confirmation of the detected cases will be done by the active surveillance team. Further investigations in the area where such detected cases may have come from would then be instituted to follow the procedures laid done for the detection of recrudescence through active survei I Iance.