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BREEDING SITES OF CULICOIDES PARAENSISAND OPTIONS FOR CONTROL BY ENVIRONMENTAL MANAGEMENT1 A@ea? 15. Hoc& 2 DonaZd R. Roberts, 3 and Francisco D. I? Pinbeiro4 I NTRODUCTION this article is to present the results of studies that characterize C. paruensis Cz&coia’e.rpuraensis(Diptera: breeding habitats in field locations hav- Ceratopogonidae) is the primary vector ing dense populations of these medically for many urban outbreaks of Oropouche important midges. virus disease in the Amazon Basin (l-4). Outbreaks of this acute febrile illness commonly occur with high attack rates, up to 44% of the population being af- ATERIALS fected (I). Surveillance of man-biting ar- M thropods during outbreaks of the disease AND METHODS have shown C. paraensis to be the most common diurnal anthropophilic insect in The Study Site the affected urban areas (3). In addition, An agricultural research sta- this biting midge is a major pest in urban tion located on the grounds of IPEAN areas because its bite produces frequent (Instituto de Pesquisase Experimenta@o and significant physical discomfort and Agropecuaria do Norte) in BeKm, Pad, dermatologic reactions (5, 6). Documen- Brazil served as our study site. Belem, tation of the strong association of C. pa- raensis with domestic environments and its anthropophilic behavior has been pre- are those of the authors and should not be construed as official or reflecting the views of the U.S. Department sented elsewhere (l-6). The purpose of of the Army. Requests for reprints should be addressed to the Reprints Section, Division of Academic Affairs, Walter Reed Army Institute of Research, Walter Reed Army Medical Center, Washington, D.C. 20307-5100, r This article will also be published in Spanish in the Bo- USA. let62 de la Ojkina Sanitaria Panamericana, 1987. The z United States Army Medical Research Unit, Brasilia, work reported here was conducted under the auspices Brazil (APO Miami, Florida 34030-0008). of the Ministry of Health of Brazil. The research was 3 Department of Preventive Medicine/Biometrics, Uni- conducted at the Evandro Chagas Institute, BelEm, formed Services University of The Health Sciences, Pad, Brazil, under PAHO Project BRA 43 11, and was 4301 Jones Bridge Rd., Bethesda, MD 20814, USA. supported by Research Contract Number DAMD 17- 4 Pan American ‘Health Organization, Washington, 74-G-9378 from the U.S. Army Medical Research and D.C.. USA. Development Command, Offrce of the Surgeon Gen- eral, Washington, D.C. The opinions contained herein the capital of the state of Par& is located main after the main stalks have been cut, at the mouth of the Amazon River and will also decay. However, both the stalks has been the site of several major Oro- and stumps require several weeks to de- pouche virus disease epidemics (1). The cay; and during this time the vegetative agricultural research station had been es- matter is high in water content. tablished, in part, to conduct research on the cacao tree, a fruit-bearing tree that Breeding Site Surveillance produces the cocoa seed from which The potential breeding habi- chocolate is derived. Our specific study tats available at the study site were moni- site, encompassing an area of lo-15 tored with the emergence traps described hectares, was located in an area where below. Habitats evaluated as breeding cacao was being cultivated and that sites were cacao leaf litter, banana supported dense populations of C. stumps, decomposing banana stalks, leaf paraensis. ax& of banana plants, piles of discarded Four general types of habitat and decomposing cacao hulls, and stag- were found in the study area, these being nant water within the marsh area. Breed- (1) mixed plots of mature cacao and ba- ing site surveillance was conducted from nana trees, (2) marsh, (3) grassy areas, June 1977 to June 1978. and (4) a monoculture of maturing de- Trap locations were changed ciduous trees. Banana plants are com- at two to three week intervals to avoid monly planted with or before cacao as a depleting the populations of immature sun-screen for the maturing cacao plants. C. paraensis. Each type of potential Marsh areas with dense, low-growing breeding habitat was monitored continu- vegetation and mixed primary and sec- ously with no less than two emergence ondary forest stands bordered two por- traps. All collecting containers were ex- tions of the study area. amined periodically, and the CzlGicoides The fruit pods of the cacao within were identified, counted, and re- tree are normally picked by hand and corded. Fresh containers were installed at taken to a centralized location where the the time of each collection. This sam- pods are split in half to remove the cocoa pling program was designed to quantify seeds and meat. The hulls are then rou- gross differences in breeding patterns at tinely discarded in piles that gradually different sites over a one-year period. decay. While they are decaying, however, the discarded hulls serve as reservoirs of Emergence Traps organic matter and water that offer ideal breeding sites for a wide variety of inver- Emergence traps used in this tebrates. study, designed for sampling habitats as- Banana plants are pruned pe- sociated with banana cultivation, are riodically to keep them growing and shown in the accompanying photo- bearing fruit. A common practice in Bra- graphs. All were constructed with one or zil is to leave the pruned parts on the more removable transparent adult col- ground to decay, and sometimes to cut lecting containers affixed atop a larger, them into smaller sections to facilitate opaque emergence chamber covering the the degradation process. Banana stumps, breeding site or sites. Although the short basal portions of the plants that re- structure of the emergence chambers var- ied with the type of breeding site being sampled, the collecting containers were always identical. Each of these collecting 285 containers consisted of a funnel inverted to provide adequate space for fly move- so that the narrow end led into a 250 ml ment into the adult collecting contain- specimen cup. CzlZicoides midges were ers. trapped when they emerged into the Trap D (shown in Photo 4) emergence chamber and subsequently was employed to sample the decompos- entered the collecting container via the ing cacao leaf litter. This trap was con- inverted funnel A 70% alcohol solution structed of modified disposable plastic was added to each container to kill and mouse cages 10.5 x 8 x 4.5 inches. A preserve the specimens. The trap was de- small circular hole about 5 cm in diame- signed to take advantage of the positive ter was cut out of the top and fitted with phototaxis of C. paraensis. a half-pint container for collecting the One type of trap (designated adult midges. The disposable cage was Trap A) was made by attaching a black 2- turned upside down over the leaf litter 3 mil plastic sheet to a pyramidal wooden and covered with heavy black plastic to frame. The trap (shown in Photo 1) was exclude light and promote movement of 1.2 m high, covered 1 m* of surface area, adults into the collecting chamber. and could cover three to five sections of decaying banana stalks. Identical or simi- lar traps were used to sample piles of de- caying cacao hulls (Photo 2) and marsh- IL SULTS . land habitats. Trap B (shown in Photo 3) was Specimens of C. paraensis designed to collect emerging adults from were collected at three of the six habitats individual upright banana stumps. The sampled (Table 1). The banana stalks emergence chamber of this trap consisted yielded the largest number of specimens, of a one-gallon paperboard “ice-cream followed by the cacao hulls and then the carton” that was open at one end. The banana stumps. No C. paraensis were carton was made water-resistant by im- collected from banana leaf axils, or from pregnating it with melted wax. A lo-12 the cacao leaf litter or marshland habi- inch surgical stockinette was attached to tats. Consequently, sampling of the ca- the open end, and this served as a sleeve cao leaf litter and marshland habitats was that fit over the banana stump. A collect- discontinued in February and March ing container was attached over a small 1978, respectively. Leafaxil sampling was opening at the top of the chamber. The only conducted for three months. whole trap was covered by a small plastic Culicoides paraensis was the trash sack to protect it from the weather. principal species of Cdicoides found cl breeding in decaying banana stalks, Dur- 5 Trap C was used to sample the - large leaf axils of banana plants. The trap ing some months cacao hulls yielded 3 was made by encircling the upper two- smaller numbers of C. paraensis than did 8 thirds of the banana plant with heavy the banana stalks. Both habitats, as well .g black plastic and placing two adult col- as the marshland habitat, produced P) other speciesof Cdicoia’es biting midges Q8 letting containers near the top of the plastic cylinder. Wire spacerswere placed (Table 2). : between the tree and the plastic sheeting Considerable variation was s observed in the C. paraensis emergence a, patterns at the two primary breeding habitats providing banana stalks and ca- 286 cao hulls. As Figure 1 shows, the emer- PhotoI (above):A typical emergencetrap (type A) used for samplingadult CuBcuidesas they emerged from decayingbanana stalks. Threetu five sectionsof bananastalks are coveredby the trap. Photo2 (below): Another type A emergencetrap used to sample Cu/icoiies midges emergingfrum discarded cacao hulls. photo 3 (above):A type B emergencetrap used to samplebanana stumps. Photo4 (MOW): A type D emergencetrap used to sampledecaying leaf liir.