Entomological assessments of interruption of onchocerciasis transmission in APOC countries-Protocol

TECHNICAL CONSULTATTVE COMMITTEE Thirtythird session Ouagadougou. 12 - l6 September 201 I ENTOMOLOGICAL ASSESSMENTS OF INTERRUPTION OF ONCHOCERCIASIS TRANSMISSION IN APOC COUNTRIES. PROTOCOL Provisional Aeenda item 7 (iii) 1 49/APOC/ COORD / I I /Doc ENTOMOLOGICAL ASSESSMENTS OF INTERRUPTION OF ONCHOCERCIASIS TRANSMISSION IN APOC COUNTRIES- PROTOCOL 1. Introduction The 6 years study (2005-2010) carried out in Mali and Senegal (ex-OCP countries), provided the first evidence that it is feasible to eliminate onchocerciasis infection l and interrupt its transmission in endemic foci in Africa using ivermectin alone and that ivermectin treatment programmes can be brought to an end. Subsequent epidemiological evaluation exercises conducted in some foci in APOC countries (Nigeria and Chad), confirmed these findings and, APOC governing body, the Joint Action Forum (JAF) decided in 2009 that the Programme, the object of which was to have established, by 2015, a country-led system capable of eliminating onchocerciasis as a public health problem in endemic countries, should move from the control of Onchocerciasis as a public health problem to the elimination of infection and the interruption of transmission. JAF also instructed that further evidence be shown from APOC countries. The latest and final results of the epidemiological evaluation conducted in six countries to assess progress towards elimination of infection presented at the 16th session of JAF in December 2O7O in Abuja, Nigeria, showed that, 16 of the 19 study sites (there are 2 study sites in each of Cross River and Kaduna States, Nigeria) were making good progress towards elimination and 8 of them with zero infection levels may have reached focal elimination. To confirm the zero infection level with the results of transmission assessment as decided by the 16th session of JAF, it was important that entomological evaluations be undertaken. ln addition to the sites with zero infection in humans, entomological assessments will also be undertaken in sites with infection levels close to zero to collect baseline data. Therefore, a standardized protocol was to be prepared and agreed upon by experts in this field, and technical as well as financial support be provided to the countries. The protocol, as described below, has been prepared based on those being used in the OCP initial protocol and that presently used in former OCP countries to assess the impact of ivermectine on transmission The major component of the study will be detailed entomological investigations required to assess the level of onchocerciasis transmission in a given area. It is recommended that the study be conducted over two consecutive transmission seasons to ensure accuracy of the final results and conclusion. 1. Reduction of 0.volvulus infection and transmission to the extent that interventions can be stopped. However, post intervention surveillance is still a necessity. I 4 8/AP OC/COORD/ I I / Doc 4. Methodology This chapter will deal mainly with elements of objectives 2 and 3, specific objective 1 being country dependent, although APOC management and/or the Working Group, may be able to give advice on selection of entomologists and technicians (3.1a). Also there will be a requirement to provide base lines for budget estimates centrally (3.1b). 4.1. Choice of catching points The number of catching points to be selected will inevitably depend on the geographical extent of each study site and the complexity of its hydrographical network. Each catching point should usually relate to a key endemic community, but be precisely located near a major breeding site, to maximize the overall fly catch. Local knowledge should be called upon with respect to seasonal agricultural habits and the seasonality of blackfly biting. lt is suggested that 2 to 5 appropriate vector catching points be selected within each study site, as already defined by the Onchocerciasis elimination team of APOC for epidemiological assessments. The number of selected catching points will have to be realistic, taking into account available resources, particularly staff, and especially budgetary constraints. The entomologists or experienced technicians should conduct prospection missions for: Selection of catching points. The information should be comprehensive giving geographical coordinates and details of related breeding places together with their likely seasonalitity; nearby endemic villages, with their relevant epidemiological data, including CDTI coverage, and population size. Raising the awareness of various authorities (political/administrative, health, community authorities). This should be largely the work of the Project Leader.; Assessing the productivity of the breeding sites and their suitability for the study during the transmission period; Assessing field needs. 4.2. Entomological evaluation Fly catches will have to be carried out at each selected catching point on 3 consecutive days. The first two days will be devoted to bulk catching, and the third to standardized capture/dissections. This would allow the technicians doing the dissections to bring back to their base the samples collected during the first two days. This activity should cover the period of significant transmission, which generally means 4 to 5 consecutive months (June-October or July-October) in savanna areas, but may be year round in some forest zones. Through these two catching strategies, the average number of flies collected from each catching point should exceed 6000 for the total catching season. J I 48/APOC/COO RD/ I I /Doc forms duly filled) to the National Oncho-Coordinator for immediate shipping to the MDSC molecular biology laboratory, or any other laboratory which is approved by experts and subject to inspection and verification by MDSC. Standardized catches During the 3rd day, the OCP standardized blackfly capture method will be applied under the direct supervision of the entomology technician in charge of the study area. According to this method, flies are collected from 7 AM to 6 PM by 2 vector collectors working alternatively per hour. The collected flies are dissected (maximum subsample of 200) by the entomology technician to determine the parous rate and to preserve the filarial infective larvae (L3 head) for identification in the MDSC DNA laboratory in Ouagadougou. Debris of Malpighian tubules of each parous fly will also be preserved for identification of the vector species in the molecular biology laboratory. The eventual remaining flies are transferred into a bottle containing 80% alcohol. The latter is labeled (date, catching point, river basin, number of females) and sent to the MDSC DNA laboratory for "pool screening". The results of the third day's catches and dissections are recorded on standards forms (l and 24) previously used for the OCP entomological evaluation. Shipping preserved samples in due time is a major problem in transmission evaluation using bulk catching. However, preserved flies should be despatched to the central laboratory at least monthly. (The capacity of MDSC for handling samples at a large scale needs to be ascertained as has the means of shipping material to the laboratory). Larvae prospections Regularly during the study period, and preferably starting at the time of choice of catching point, larval samples of S. damnosum s.l. populations will be collected at breeding sites as near as possible to the catching points and preserved in Carnoy's fixative for cytological identification. Collections will be sent to APOC management in Ouagadougou or any other laboratory retained by both parties for cytotaxonomic identification within the country concerned. 4.3. Climatologic data collection Climatologic variables (temperature, rainfall, wind direction, relative humidity, FlT, etc.) will be recorded in the nearest climatology stations to the selected sites. These parameters could be helpful for the interpretation of the entomological data. 4.4. Sending samples to the molecular biology laboratory (DNA tab) and to the cytotaxonomic identif ication centres The bottles containing blackflies preserved in 80" alcohol and the glass strips carrying the parasites found in dissecting the flies will be sent to the molecular biology laboratory (MDSC, Ouagadougou) or elsewhere in the area (cf 4.2) any time this is feasible, but at least once a month, for processing. The bottles containing the larvae of I 48/APOC/COORD/ I I /Doc 5 Entomologist ........... Entomology t".r'ni.ir;;................. ... Drivers Village fly catchers (vector collectors) per catching point It is assumed that a standard team will cover two sites per week. However, this will have to be assessed in the field and may have to be modified in some places, especially in the rainy season. 7 2 L 4 I 4 8/A P OC/COO RD/ I I / Doc 7