Joumal of the American Mosquito Control Association, 1l(3):343-353, 1995Copyright O 1995 by the American Mosquito Control Association, Inc.

MOSQUTTO VECTOR CONTROL AND BTOLOGY rNLATIN AMERICA-A FIFTH SYMPOSIUM1

GARY G. CLARK' (ORGANIZER)

Dengue Branch, Centers for Disease Control and Prevention,2 Calle Casia, San Juan, PR 00921-3200

ABSTRACT. The fifth Spanish language symposium presented by the American Mosquito ControlAssociation (AMCA) was held as part of the 6lst Annual Meeting in Portland, OR, in March 1995. Theprincipal objective, as for the previous 4 symposia, was to increase and stimulate greater participation inthe AMCA by vector control specialists, public health workers, and academicians from Latin America.This publication includes summaries of 20 presentations that were given in Spanish by participants from6 countries in Latin America and the USA. The symposium included the following topics: ecological andgenetic studies of anopheline vectors of malaria, laboratory and field evaluation of chemical and biologicalcontrol agents for several mosquito species, and community control of Aedes aegypti.

INTRODUCTION

The American Mosquito Control Association(AMCA) is the world's leading professional or-ganization dedicated to the study and control ofmosquitoes and other vectors. The AMCA pro-motes closer cooperation among those directlyor indirectly concerned with or interested inmosquito control and related work. Toward thatend and to further enhance the international roleof the association, a Spanish language sympo-sium was held in 1995 at the 6lst Annual Meet-ing in Portland, OR. This marked the fifth con-secutive year in which this session was held.Twenty presentations were given in Spanish byparticipants from 6 countries in Latin Americaand the USA. The symposium included the fol-lowing topics: ecological and genetic studies ofanopheline vectors of malaria, laboratory andfield evaluation of chemical and biological con-trol agents for several mosquito species, andcommunity control of Aedes aegypti. Summariesof 3 previous symposia have been published(Clark and Suarez 1991, 1992, 1993).

Financial support for this unique and inno-vative session at the Annual Meeting continuesto be good. Recognition for financial support forthe 1995 symposium goes to the following spon-sors and individuals: Clarke Mosquito ControlProducts (John L. Clarke, Jr.); ZENECA (Ed-uardo Moreira); ADAPCO (Allen Wooldridge);Northeast Vector Management (Bill Zawicki);Beecomist Systems (Ed Kutzner); Vectec, Inc.(Ed Meehan); American Cyanamid (Bill Jany);Summit Chemical (Larry Kase); ARRO-GUN

I Presented at the 6l st Annual Meeting of the Amer-ican Mosquito Control Association, Portland, OR, onMarch 21, 1995.

2 Reprints may be requested from Gary G. Clark,Dengue Branch, CDC, 2 Calle Casia, San Juan, PRoo92t-3200.

Spray Systems (Dan Ariaz); Zanus Corporation(David Sullivan); JAYCO Products (Jay Stew-art); and the Northwest Mosquito Vector ControlAssociation (Peter DeChant). Special recogni-tion also goes to the Pan American Health Or-ganization (Dr. Gabriel Schmunis and Dr. Mi-chael Nelson) for providing funds that supportedattendance of several speakers. Special thanksgo to Dr. Ronald A. Ward, Editor of the JAM-CA, for his assistance and encouragement topublish these summaries and for identifyingfunds for this publication.

As a result of the positive and enthusiasticresponse from participants and the AMCA lead-ership, this unique forum will be included in fu-ture meetings. In this way, the problems causedby mosquitoes and other vectors in areas outsideof the continental United States receive addi-tional attention. Offering this symposium hasserved to significantly increase AMCA mem-bership in Latin America and has fostered andfacilitated increased academic, intergovernmen-tal, and commercial interaction among col-leagues living in Latin American countries andwith their peers in the USA.

SUMMARIES

Larval ecology of the exotic dengue vector,Aedes albopiclus in two states in

northeastern Mexico

J. P Martfnez-Mufroz and I. Ferniindez-Salas

Laboratorio de Entomologia Mddica,FCB-UANL, Monterrey, Nuevo Le6n, Mexico

An Asian vector of dengue, Aedes albopictus(Skuse), was first reported in the United States(Houston, TX) in 1985. In 1988, it was identi-fied across the Mexican border from Texas inTamaulipas State, in northeastern Mexico. Themosquito was also found in abandoned tires in

343

344 Jounral oF THE AMERTcIN Moseurro CoNTRoL AssocrATIoN V o L . 1 1 . N o . 3

Matamoros city adjacent to Brownsville, TX.During 1993, the vector was also reported in 2bordering cities in Coahuila State: Piedras Ne-gras (adjacent to Eagle Pass, TX) and in Acuffacity (Del Rio, TX). These reports pointed towarddiscarded tires as the main site for Ae. albopictusbreeding in Mexico. However, considering themore abundant availability of breeding sites pro-vided by typical Latin American villages andtowns, plus an expected opportunistic behaviorin oviposition habits of Ae. albopictus, objec-tives of this study were: 1) to determine typeand frequency of breeding sites used by Ae. al-bopictus in northeastern Mexico, and 2) to mea-sure the degree of invasion of Ae. albopictusover known Aedes aegypti (Linn.) breeding sitesin the same area. A survey for Ae. albopictuswas carried out in Thmaulipas, Nuevo Le6n, andCoahuila states in northeastern Mexico. Thesearch covered cemeteries, abandoned tires, andperidomestic artificial containers. Larvae werecollected and reared to adult stage for identifi-cation. From April to June 1994, no Ae. albo-pictus were found in 14 villages in Nuevo Le6nState. In November, 5O breeding sites were sur-veyed in Matamoros, Tamaulipas State; 92Vowere infested by the Asian mosquito. These per-idomestic containers were 5-gallon buckets, ce-ment tanks, 55-gallon drums, animal drinkingwater containers, and trays. These sites were in-side houses or backyards (38Vo), in flower vasesin cemeteries (SOVo), in public parks (2Vo), andin used car establishments (2Vo). This specieswas identified in l6vo of flower vases surveyedwithin a private city cemetery in Piedras Negras,Coahuila State. Cemetery flower vases (87o)were also the only breeding sites in Acuffa cityin Coahuila. Colonization of typical Ae. aegyptibreeding sites by Ae. albopictus was only re-corded in Matamoros city, where this specieshas heavily infested urban and rural areas.

Temporal abundance of Anopheles aquasalislarvae in a malarious area in northern

Venezuela and associated factors

M. E. Grillet, H. Montaflez and J. Berti

Instituto de Zoologia Tropical, Facultad deCiencias, Universidad Central de Venezuela,

Caracas and Direccion Sectorial deMalariologia y Saneamiento Ambiental,

Ministerio de Sanidad y Asistencia Social,Maracay, Venezuela

Anopheles aquasalis Curry is the principalvector of malaria in northeastern Venezuela. Astudy of the ecology of this species was carriedout in the southern region of Paria, a coastal areaof Sucre State where malaria is an important

public health problem. Two hypotheses weretested: l) the anopheline larval population hastemporal and spatial nonrandom distributions,and 2) these distributions are influenced by hab-itat variables that can be readily identified.Anopheles aquasalis larvae were sampledmonthly with a standard dipper for a l-year pe-riod (Jufy 1993-June 1994) in 4 dominant hab-itat types (brackish: mangrove lagoont freshwa-ter: marsh, pond, and swamp), and populationdensity (larvae/dip) was calculated from 30 dips.Twelve selected aquatic variables were quanti-fied (vegetation cover, plant height, phytoplank-ton, associated aquatic organisms, water depth,pH, temperature, dissolved oxygen and carbondioxide, conductivity, salinity, and alkalinity) todescribe larval habitat and predict temporal oc-currence of the species. Temporary shallowmangrove lagoons consistently harbored muchhigher densities of An. aquasalis (9.15 -r 1.121dip) than permanent freshwater ponds (l.O +

0.2/dip) and shallow marshes (0.9 -+ 0.1/dip),whereas semipermanent swamp habitats con-tained no larvae. Conductivity, salinity, and phy-toplankton were significantly higher, and alka-linity and animal species richness were lower inhigh-density An. aquasalis sites than in low-den-sity sites. Higher population density occurred atthe end of the rainy season (September-Octo-ber), with no correlation found between densityand rainfall. Regression analysis between den-sity and habitat variables showed a positive cor-relation with (in order of importance) salinity,depth, aquatic plant height, and dissolved oxy-gen; and a negative association with pH. Thesevariables explained 8OVo of the variation in lar-val density. The breeding of An. aquasalis inhigh-salinity habitats was confirmed by our re-sults; the results also revealed that the majorityof environmental factors evaluated, specially sa-linity and depth, can be good predictors for thespecies' reduced temporal distribution. The re-sults suggest the feasibility of formulating ap-propriate control strategies for An. aquasalis innorthern Venezuela. This research was fundedby CONICIT grant RPIV-130032-ll.

Vector biology of resting populations andbiting biorhythm of Culex tarsalis populations

in Montemey, northeastern Mexico

A. Solis-Santamaria, E Reyes-Villanueva andI. Fern6ndez-Salas

Laboratorio de Entomologia Midica,FCB-UANL, Monterrey, Nuevo Le6n, Mexico

Studies of potential vectors of equine enceph-alitis are lacking in Mexico. Despite frequent re-ports of arbovirus activity in several states in the

Ssp,rsMsen 1995 Moseurro Vpcron Svuposluv 345

US along the Mexico-USA border, knowledgeof viruses in mosquito vectors is poorly docu-mented in Mexico since the Venezuelan equineencephalitis (VEE) outbreak in the l970s. Culextarsalis Coq., a VEE and eastern equine enceph-alitis (EEE) virus vector, is abundant in rural andurban areas of Monterrey in northeastern Mex-ico. We studied age-structure, insemination rate,trophic and physiological stages, and bitingrhythm of resting females Cx. tarsalis. The studysite was in an agricultural area 20 km fromMonterrey. Resting mosquitoes were collectedin 23 redboxes (l x 2 x I ft.) and 5 old tires(5-ft. diam). Eight-hundred seventy femaleswere collected during the 20 days of the study.Mosquitoes were dissected in the laboratory andthe following parameters were checked: abdom-inal appearance (Sella stages), parity (Detinovatechnique), follicular development on ovariesand ovarioles (Christophers' stages), and sper-matheca for insemination. Preliminary resultsdemonstrated that 657o (566) of the femaleswere unfed, l5.5%o (135) were bloodfed, andl9.5%o (169) were gravid. Parity rate for unfedfemales was 2l%o (119), whereas 18.57o (25)was recorded for fed mosquitoes. Ovarian de-velopment showed that 89Vo of unfed femaleshad ovarioles at Christophers' lst stage, whereasChristophers' 3rd stage was found in 38.5Vo offed females. Ovariole relics were recorded inl.8%o.The insemination rate was 847o. We foundthat most of the unfed nullipars, showing Chris-tophers' lst stage, corresponded to newlyemerged females from nearby breeding sites.Biting rhythm was determined by human land-ing collections and by using a screen trap baitedwith a horse during a 10-day period, in a col-lecting schedule of 12 h from t800 to 0600 h.A total of 400 Cx. tarsalis females were caughtwith both methods; the highest biting activitywas recorded t h after sunset. Species collected,other than Cx. tarsalis, were Aedes dorsalis(Meigen), Aedes triseriatus (Say), Aedes tae-niorhynchus (Wied.), and Culiseta inornata(Williston). Because all of these also have beenreported as encephalitis vectors, the need to in-crease research on encephalitis vectors in north-ern Mexico is reinforced.

Dispersion of larval stages ofAnopheles nuneztovari in fish ponds from

Buenaventura, Colombia

D. L6pez-Matta and R. Gonz6lez

Departamento de Biologia, Universidad delValle, Cali, Colombia

Anopheles nuneztovari Gabaldon is one of theprimary vectors of malaria in Colombia. In Bue-

naventura, fish ponds are the principal breedi4gsites. In order to understand which factors mightbe useful as interventions for future control strat-egies, we determined the dispersion of An. nu-neztovari larvae in fish ponds, associated withdepth, turbidity, water-vegetation interphase area,orthophosphates, and dissolved oxygen. Sevenfish ponds were sampled during 1993 using a350-ml dipper; 4 ponds were surveyed 3 times.^the An. nuneztovari larvae were counted and theinstars present were determined. The dispersionof the larval population was analyzed using Tay-lor's power law, Lloyd's mean crowding index,and Iwao's contagious regression. The associationbetween larval density and the habitat variableswas analyzed with linear and multiple regression.

Multiple regression analysis showed that tur-bidity and the water-vegetation interphase area(Y : 0.57 + 0.06veg. - 0.016turb.; r : O.87;P < 0.001) were important to the dispersion andabundance of An. nuneztovari larvae. When tur-bidity increased, larval food production de-creased and affected larval development. This iscompensated for by the microflora associatedwith the water-vegetation interphase. When thewater level decreased, the water-vegetation in-terphase area diminished and larval density alsodecreased. Water depth accounted for 5O7o ofthe variation in the reduction in larval density.

Taylor's power law showed that An. nunezto-vari larvae had an aggregated distribution (b :

1.35), but according to the alpha parameter(0.48) of Iwao's regression, this distribution wasnot an inherent behavior ofthe larval stages. Thebeta parameter (1.30) of lwao's regression waslow and, therefore, showed no clear relationshipbetween aggregated distribution and habitat het-erogeneity given by the extension of the water-vegetation interphase. This index and the strongrelationship between Lloyd's mean crowding in-dex and the density (7 : O.996; P < 0.0001)suggested that aggregated distribution of larvalAn. nuneztovari was determined by female ovi-positional behavior and the later larval mortality.

Mosquitoes and bromeliads: species-specificselectivity patterns on the northern coast and

southern Guiana Shields in Venezuela

J. C. Navarro, J. Ingunza,Z. Fernandez and R. Barrera

Instituto de Zoologia Tropical, UniversidadCentral de Venezuela, Caracas, Venezuela

Collections were made at 4 locations in 3 na-tional parks in Venezuela; two on the northerncoast of Venezuela: Cerro Santa Ana (CSA)(Paraguan6 Peninsula, near the Lesser Antilles)and Sierra de San Luis (SSL) (continental origin

346 JounNel- on rnn AlcnrcnN Mosqurro CoNrnol AssocteloN VoL. I l , No. 3

close to coastal Andean mountains); and two onthe south Guiana Shield: La Gran Sabana (LGS)and Auyan-Tepui (AUY) (western Tepui sum-mit). Thirteen mosquito species were identifiedin 15 Bromeliaceae species and one species ofSarraceniaceae. The mosquito species richnesscollected in the plants per location (mosquitospecies/plant species) showed the following or-der: LGS (9/5), SSL (8/5), AUY (5/6), and CSA(416). ^fhe "Guild Structure" analysis estab-lished a selection model (D) for the bromeliadresource and a resource selection index (R) forthe most selected plant species. Selectivity (pos-itive and signiflcant) by one or more plants spe-cies was high in SSL with 6 of 8 mosquito spe-cies (75Vo); medium in Guiana Shield: LGS(55Vo) and AUY (5O%;o); and low in CSA (25Vo)I D > Z ( 0 . 9 9 ) = 3 . 3 2 1 .

The mosquito species with the greatest pref-erence for plant species ["D" > Z (O.99) =

3.82) per location were Aedes sexlineatus (Theo-bald) and Wyeomyia bicornis (Root) in SSL;Wyeomyia fshi Zavortink, Aedes (Howardina)sp. nov., and Wyeomyia (Cruzmyia) sp. nov. inLGS; Runchomyia frontosa (Theobald) andAnopheles (Kerteszia) "Auyantepui Mesa form"in AUY; and only Wyeomyia celaenocephalaDyar and Knab in CSA. The most selectedplants [R > Z (O.99) : 3.82) were Vriesea pla-tynema Gaudichaud and Aechmea paniculigera(Swartz) in SSL; Brocchinia micrantha (Baker)and Brocchinia reducta Baker in LGS; B. hec-tioides Mez and V. rubra (Ruiz and Pavon) inAUY; and Guzmania lingulata (Linn.) in CSA.

A species-specific selectivity pattern was ob-served in some mosquito species (49Vo of thespecies did not show selectivity) and this patterndepends on factors such as: degree of isolationand geoevolutive origin in the location, brome-liad resource abundance, macroclimatic factorsas consequences of altitude, and microclimaticfactors associated with the plant itself. Supportfor this research was provided by CONICIT RP-VII-240060 and PAHO.

Evaluation of light traps combined withcarbon dioxide and l-octen-3-ol to

collect anophelines in Venezuela

Y. Rubio-Palis

Division de Investigaciones, Escuela deMalariologia y Saneamiento Ambiental

"Dr. Arnaldo Gabaldon," Maracay, Venezuela

In a search for a satisfactory method for sam-pling anophelines that would reduce the need touse human landing catches for routine evalua-tion of control programs, updraft ultraviolet lighttraps combined with carbon dioxide (COr) and

l-octen-3-ol (octenol) were compared with theCDC light trap and human landing catches ofAnopheles albimanus Wied. and Anophelesaquasalis Cuny.

The study was carried out in Puerta Negra(10"06'N, 67"36'W),20 km south of Maracay,Aragua State, in northcentral Venezuela. Collec-tions were carried out between 1830 and 2130h, 3 nights/wk every month between September1994 and February 1995. Six collection stationslocated 100 m apart were established forming across to test the following methods: l) landingcatches on 2 human baits; 2) a battery-operated,updraft UV light trap; 3) an updraft UV lighttrap plus COr; 4) an updraft UV light trap plusoctenol; 5) an updraft UV light trap plus octenoland CO, and 6) the CDC light trap. Each meth-od was rotated each night so that equal numberof collections with each method were carried outat each station. The following morning mosqui-toes were killed, identified, counted, and dis-sected for parity.

Preliminary results show that significantlymore An. albimanus were collected with the up-draft UV light trap alone or with any of the at-tractants than An. aquasalis. The CDC light trapused alone was inefficient in collecting thesespecies. The updraft UV light trap was more ef-ficient for catching An. albimanas when usedwith octenol, whereas the use of octenol plusCO, did not significantly increase the number ofAn. albimanur collected. About 2O7o of the an-ophelines caught in all light traps could not beidentified. Of the anophelines caught in the CDClight trap, 75.'|Vo were males;3O.3Vo males werecaught in the updraft UV light; whereas the useof attractants produced only 47o males for oc-tenol and 9Vo males for CO, and CO, plus oc-tenol. The updraft UV light trap used with oc-tenol as an attractant is a promising collectionmethod that can substitute for or complementhuman landing catches for monitoring popula-tions of An. albimanus but not An. aquasalis.

This research was funded by FUNDACITE-ARAGUA DLSAOO29 and PAHO.

Investigations of detoxifying esterasesin Culex pipi.ens quinquefasciatu,s fromMartinique and surrounding countries

A. Yebakima, M. M. Yp-Tcha, P Reiter,N. Pasteur, M. Raymond, D. Heyse,

D. Bourget and B. Delay

Couseil Gindral-Service Ddmoustication,Fort-de- France, Martinique ; Dengue Branch,

CDC, San Juan, Puerto Rico; andltrboratoire de Gdndtique et Environment,

CNRS/U RA, Montpe lier, France

Sep.Elassn 1995 Moseurro VEcroR Svuposluv 347

Several over-produced esterases confer resis-tance to organophosphorus insecticides in theCulex pipiens complex. Our preliminary inves-tigations showed that 4 esterases of high activity(esterase B1, the associated esterases A2-82,and esterase C2) have a wide geographic distri-bution and frequency in the Caribbean area:Cuba, Puerto Rico, Haiti, St. Martin, Guade-loupe, Martinique, St. Lucia, Barbados, FrenchGuiana, and Venezuela. These results underscorethe importance of indirect insecticide pressureand/or passive resistance on gene migration, be-cause in many countries there is no general vec-tor control program against Culex pipiens quin-quefasciatus Say.

Linkage disequilibrium in elevatedesterases of Culex quinquefosciatus in

the presence and absence of insecticideselection pressure

J. A. Bisset, M. Rodriguez, L. M. Recio,J. Hemingway, J. D. Lines, G. J. Small,

S. H. P P. Karunaratne and A. J. Ketterman

Instituto Medicina Tropical "Pedro Kouri,"Ciudad Habana, Cuba and

Department of Medical Parasitology,Inndon School of Hygiene and

Tropical Medicine, lnndon, England

ln Culex quinquefasciaras Say, the elevatedesterases Bl,82, and A2 are involved in broadspectrum organophosphate insecticide resis-tance. The Bl esterase has a limited distribution.with reports of its presence only in Californiaand Cuba. We now report the occurrence of Blin 2 additional field populations from Trinidadand Colombia. In both locations, as well as inCuba, 2 more elevated esterases, ,4,6 and 86,have also been found. Previously, the A2 and82 esterases had been found in numerous fieldpopulations of Cx. quinquefasciatus where theA2,Bl, andB�2 esterases are all present. The A2and 82 esterases no longer show any evidenceof linkage disequilibrium in the absence of pos-itive insecticide selection pressure.

Population genetic analysis ofAnopheles aquasalis in Venezuela and

Trinidad

Y. Rangel, G. Vele and D. D. Chadee

Instituto de Zoologia Tropical, UniversidadCentral de Venezuela, Caracas, Venezuela and

Insect Vector Control Division, Ministry ofHealth, St. Joseph, Trinidad

An outbreak of Plasmodium vivax malaria oc-curred in Icacos, Tiinidad, in l99l and was then

traced to a Tiinidad fisherman who had visitedPedernales (Delta Amacuro State), Venezuela.The vector of malaria in both countries isAnopheles aquasalis Curry. Continuous humanmigration between Venezuela and Tiinidad andthe presence of different morphologic character-istics in An. aquasalis populations from Peder-nales established a need to determine the geneticstructure of both populations for risk assess-ment. To do this, 6 populations from the westcoast of Trinidad and one population from Ped-ernales were analyzed for genetic variation at 18isozyme loci. Estimates of genetic variability forAn. aquasalis from Pedernales were relativelylarger than the values obtained in Tiinidad. Thepercentages of polymorphic loci were 22-33Vo;the average heterozygosities were 0.125 and0.08, respectively; and the mean number of al-leles per locus (1.9) was the same for both pop-ulations. The value of Fr, (Wright's F statistics),averaged over all loci, was 0.0516 indicatingthat there is only minor heterogeneity in allelicfrequencies, but there were positive values ofWright's fixation index for 3 enzyme-electro-morph loci in each country. These results indi-cate the need for local vector control to reducedisease incidence. Support for this research wasprovided by PAHO; CONICIT RPIV-130032;Ministry of Health, Venezuela; and Ministry ofHealth. Trinidad. W.I.

Polymorphism of circumsporozoite protein ofPlasmodium vivax frotn Colombia

J. M. Gonz6lez, M. E Suarez and S. Herrera

Fundaci6n Centro de Primates (FUCEP),Instituto de Salud del Pacifico (INSALPA)

and Departamento de Microbiologia,Universidad del Valle. Cali. Colombia

Malaria infection begins when infectedAnopheles mosquitoes inject sporozoites into theblood vessels. The circumsporozoite protein(CS) is the most extensively studied among sev-eral proteins that have been identified on the sur-face of the sporozoites. The Plasmodium vivaxCS protein contains a central region'composedof multiple tandem repeats of a nonapeptide. Ac-cording to the gene sequences, this region pre-sents 2 variants, designated type I or "com-

mon" and type 2 or "variant," that can be dif-ferentiated using monoclonal antibodies (mAb).These mAb have proven to be useful in the de-tection of sporozoites in salivary glands of in-fected mosquitoes. In addition, due to its im-munogenicity, this region has been incorporatedinto synthetic and recombinant malaria vaccinecandidates.

In order to determine the extent of polymor-

348 JounNnr- oF THE AMERTCAN Moseurro CoNrnol AssocrlloN VoL.

phism of the repetitive region of the CS in iso-lates of P. vivax from Colombia, sporozoiteswere obtained by experimental infection ofAnopheles albimanus Wied. Mosquitoes werefed by artificial membrane on infected blood of38 individuals from different malaria endemicareas and sporozoites were recovered 14 daysafter infection. Thirty-eight isolates were ana-lyzed using an immunofluorescence test with 2mAb specific for both type 1 or type 2 of the P.vivax CS. The type-2 sequence was found in 2lisolates (55Vo), and the type-l sequence in 13(34Vo) isolates. Three (8Vo) of the isolates react-ed with both mAb, and one was negative forboth mAb. The high frequency of the type-2 se-quence among the Colombian isolates indicatesthe necessity to use both mAb to accurately de-termine the infection of malaria vaccine candi-dates. Support for this research was provided byCOLCIENCIAS and a grant from the Commis-sion of the European communities.

Revised list of themosquitoes of Mexico

R. E Darsie, Jr.

International Center for Public HealthResearch, University of South Carolina,

M c C le llanv ille, S out h C arolina

The serious study of the mosquito fauna ofMexico started with the original lists publishedin 1956. A revised list of the anopheline mos-quitoes was recorded in 1976 and a more exten-sive list of 118 species was given in 1977. Manyspecies have been added to the fauna, there arealso many supraspecific changes to report.

A concentrated effort to know the Mexicanmosquitoes was made in the 1940s to l96os dueto the important work of Dr. L. Vargas and hiscolleagues. Many species were added in the late1960s and the 1970s by Dr. J. N. Belkin and hisstudents who were involved in the project"Mosquitoes of Middle America." Until now,no attempt had been made to assemble a com-plete list of the Mexican mosquito fauna. Anaccompanying and necessary parallel is thecompilation of a bibliography dealing with Mex-ican mosquitoes. To date, 142 titles are includedin such a list of relevant references.

At present 20 genera,37 subgenera, and 223species are known in the Mexican mosquito fau-na (Table 1). Many details of the list will bediscussed in a more thorough report later, but 2issues are emphasized here. The following spe-cies have been erroneously reported from Mex-ico: Aedes impiger (Walker), Aedes punctor(Kirby), Aedes fulvithorax Lutz, Culiseta impa-riens (Walker), Deinocerites epitedeus (Knab),

Table l. Genera of mosquitoes occurring inMexico and the number of subgenera and

species in each.

GenusNo. No.

subgenera species

AedeomyiaAedesAnophelesChagasiaCoquillettidiaCulexCulisetaDeinoceritesHaemagogusJohnbelkiniaLimatusMansoniaOrthopodomyiaPsorophoraSabethesShannonianaToxorhynchitesTrichoprosoponUranotaeniaWyeomyia

Totals

I

3029I0I00I0J

201I2-t

3 T

l6026

I4

60J

64II2I

l 84L

429

1 4223

and Deinocerites spanius (Dyar and Knab).Also, there are 29 species that are apparentlyrestricted to Mexico, based on present knowl-edge.

Susceptibility of Anopheles darlingi tochemical insecticides in

Bolivar State, Venezuela

F Saume, D. Molina de Ferniindez, O. Hidalgo,A. Anaya and M. Castillo

Facultad de Agronomia, Universidad Centralde Venezuela and Direcci6n de Endemias

Rurales, Ministerio de Sanidad yAsistencia Social, Maracay, Aragua, Venezuela

The susceptibility to chemical insecticideswas evaluated in 2 populations of Anophelesdarlingi Root from Bolivar State, where malariatransmission due to this species represents ahigh percentage of malaria cases reported forVenezuela. The standardized methods at the di-agnostic doses of the World Health Organizationwere used in this study. The results were similarin both populations, with a high level of toler-ance to DDT and cypermethrin; a low level oftolerance was found to the following insecti-gids5-elg2nophosphate: malathion, fenthion,pirimiphos methyl, and fenitrothion; carbamates:

SEp,rrNrssn 1995 Moseurro Vscron Svuposluu

propoxur and bendiocarb; and synthetic pyre-throids: lamdacyhalothrin, deltamethrin, and cy-fluthrin. These results will permit a better im-plementation of the chemical control strategyused for An. darlingi through a rational programof insecticide rotation in order to maintain lowlevels of tolerance to the most commonly usedinsecticides.

Residual effect of lvo Abate@ granules andSVo Abate@ pellets in field and laboratory

conditions in Monterrey, northeasternMexico

R. Ndjera-Velinqtez

Ittboratorio de Entomologia M€dica,FCB-UANL, Monterrey, Nuevo Le6n, Mexico

The larvicide Abate@ (temephos 17o granules)is intensively used by the Vector Control Pro-gram in Mexico against immature populations ofthe dengue vector, Aedes aegyptl (Linn.). A con-centration of I part per million (ppm) per literof water is used in mosquito breeding sites.However, water management, washing, and re-filling of peridomestic containers such as drums,buckets, and cement tanks affects residuality ofthe temephos granular formulation. During thisresearch the aims were: l) to compare residual-ity and effectiveness of the l7o granular Abateformulation versus the 5Vo Abate pellets in thesame concentration of I ppm/liter, a larvicidealready in use in the United States for reducinglarval populations of Ae. aegypti and Culexquinquefascialas Say breeding in domestic 55-gallon drums; 2) to compare alternative doses ofthe 5Vo Abate pellets such as 2, 3, 4, and 5 ppm/liter in both residuality and efficacy; and 3) todetermine the same parameters under laboratoryconditions. Field trials were conducted in a sub-urban residential area near Monterrey. A groupof 35 drums belonging to residents was treatedwith the larvicide as follows: I ppmAiter of l%ogranular Abate; I ppm.4iter of 5Vo Abate pellets;2, 3, 4, and 5 ppm/liter of 5Vo Abate pellets (5drums were used for each dose): and 5 drumsthat served as controls. People were allowed touse the water as they routinely do to determinethe effect of such activities on larvicide efficacy.Comparisons were made with another group of35 drums containing the same dosages but with-out perrnitting people to use the water. Drumsand dosages were randomly selected for thedwellings. Samples of dead and live larvae werecollected fortnightly from October 1993 to May1994. The laboratory study was made using 55-gallon drums treated similarly but using onlyone drum per dose. Drums were set for 8months; assays were made every 2 wk using 3OO

ml of treated water with 25 Ae. aegypti larvae.Mortality was recorded after 24-h exposure.Field results showed an overall IOOVo mortalityfor 16 wk for all doses regardless if water wasused or not. Abate 5Vo pellets at 3 and 5 pprn/liter produced the highest residual effect,24 and27 wk, respectively. Due to severe lack of watersupply during the study interval, people usedwater in several drums without permission. Thisfact limited our results from both formulationsand concentrations in the field. This practice em-phasizes the need to involve participation of thecommunity to increase vector control successeven when chemical control is utilized. The laststatement is supported by our finding of lOOTomortality and 8-months residuality in the labo-ratory study for all concentrations and formu-lations tested.

Susceptibility studies of Aedes aegyptifrom different regions of Venezuela to

organophosphorus and pyrethroidinsecticides

D. Molina de Ferndndez. A. Salcedo.J. Gonzillez, O. Salas, J. Bisset and

M. Rodriguez

Direcci6n de Endemias Rurales, Ministeriode Sanidad y Asistencia Social, Maracay,

Aragua, Venezuela and Instituto de MedicinaTropical Pedro Kouri, ln Habana, Cuba

The basic tool for the control of Aedes aegypti(Linn.), the principal vector of dengue and den-gue hemorrhagic fever (DHF) in Venezuela, hasbeen the use of chemical insecticides. This strat-egy when used for several years can select vec-tor populations more tolerant to and eventuallyresistant to some insecticides. For this reason,the objective ofthis research was to establish thebaseline of susceptibility to organophosphateand pyrethroid insecticides for Ae. aegypti lar-vae from different states of Venezuela (Araguay,Apfre, Barinas, Carabobo, Gu6rico, Lara, Mir-anda, and T6chira) where dengue and DHFtransmission has been high. World Health Or-ganization procedures were used.

Preliminary results indicated that 6 out of 8field strains were susceptible to malathion (Re-sistance Factor 0.50 < 3) and the other 2reached a verification level with a ResistanceFactor O.5O between 5.8 and 7.8. All field strainswere susceptible to fenitrothion and tolerant topirimiphos methyl. As for the synthetic pyre-throids, we found deltamethrin resistance with-out any cross-resistance to lamdacyhalothrin, cy-permethrin, or cyfluthrin. These results will per-mit the prediction of the levels of resistance inthe adult staee.

JounNet- or rHe ArvrenrceN Mosqurro CoNrnol AssoclettoN Vor-.

Field effectiveness of three insecticidesin ULV spraying of malathion, Dursban andMosquito Master 412 against Aedes aegypti

and Culex quinquefasciatus inMonterrey, Mexico

N. J. Vel6zquez-Quintana, I. Ferniindez-Salasand A. Flores-Leal

Laboratorio de Entomologia Midica,FCB-UANL, Monterrey, Nuevo Le6n, Mexico

In many Latin American countries. emergen-cy control measures during outbreaks of denguefever and malaria are based mainly on ultralowvolume insecticide spraying. For decades, mal-athion (95Vo) has been the most used adulticideto reduce adult densities. Clearly, the search foralternative chemicals is needed in developingcountries interested in controlling these diseases.This study was conducted to determine field ef-ficacy of the commonly used malathion95Vo and2 other chemicals that have never been used inMexico-Dursban (chlorpyrifos 727o) and Mos-quito Master (chlorpyrifos lZvo plus 4Vo per-methrin)-to kill caged adult populations of Ae-des aegypti (Linn.) and Culex quinquefasciatusSay. Tests were conducted in an open, vegetatedarea in a semiurban location l0 km from Mon-terrey. An LECO 500 aerosol generator wasused, at the following insecticide flow rates: 6.3oz./min for each chemical and a second rate of6.5 oz.lmin for Dursban. Open and vegetated as-says were conducted by placing 2 parallel, 600-ft.-long lines of caged mosquitoes. Cages foreach line were placed at 6 different exposuredistances: 100, 200, 300,400, 500, and 600 ft.A total of 24 cages, each containing 20 femalemosquitoes, was hung at a height of 6 ft. Sprayswere made separately for each species and foropen and vegetated areas in the study site. Ve-hicles carrying the generator drove at 10 mph;each assay was carried out at sunset while re-cording ambient temperature, wind velocity, anddirection. Controls were placed during all fieldtests. The effectiveness of insecticides was re-corded as l-h mortality. Greater than 857o mor-tality was produced by each chemical for bothmosquito species up to 3OO-ft. distances in theopen area. A IOOVo 24-h mortality was recordedfor all chemicals in 6 tested distances in the veg-etated area. The combined product MosquitoMaster showed a higher l-h mortality effect.Mortality was reduced 4.8Vo for every 100-ft.distance in the open area. A 5.6Vo mortality re-duction for every 100 ft. was also recorded forthe 3 chemicals in the open area at 24 hr.

'fhe

study also addressed costs and benefits of tra-ditionally used malathion versus Dursban andMosquito Master 412, an important considera-

tion in Latin American countries wantins to re-place malathion.

Utilization of the copepodM e socy clop s longis etus (Copepoda:

Ciclopoidea) to control larval populationsof Aedes aegypti in domestic cement tanks

in Chiapas, southeastern Mexico

E. Magall6n-Gastelum,

Laboratorio de Entomologia Mddica,FCB-UANL, Monterrey, Nuevo Le6n, Mexico

Recent work has considered the possibility ofusing predacious copepods to reduce immaturepopulations of the dengue vector Aedes aegypti(Linn.). Satisfactory results have been obtainedunder controlled conditions and also in field sit-uations where water is always present in breed-ing sites. However, successful use of copepodsreleased in the field is highly dependent on com-munity participation. Cement tanks (pilas) rep-resent the chief breeding site for the dengue vec-tor in villages in southeastern Mexico. Theymaintain water as well as larval populations ofmosquitoes throughout the year. This work wasaimed at evaluating the efficiency of the cope-pod Mesocyclops longisetas (Thi6baud) in re-ducing larval populations of Ae. aegypti in pilasin Huixtla, a city with 30,000 residents near Ta-pachula in southeastern Mexico.

Additional objectives were to assess copepodsurvivorship when assisted by community par-ticipation and to assess predator reproductionrate in pilas. Research was conducted during therainy season from June to November 1994. Agroup of 600 pilas was selected in houses inHuixtla; 300 were treated with 200 ovigerousfemale M. longisetus, and 300 served as con-trols. Residents where pilas were treated re-ceived a 30-min talk on dengue, the role of Ae.aegypti larvae, and the copepod controllingagent. Directions on how to take care of ciclo-poids at the time of pila washing were also pro-vided in a calendar nailed on the wall of thehouse. A marker set in the pila bottom was alsoa reminder of copepod presence for residents.Fifty treated pilas and 5O controls were sampledmonthly to check copepod abundance and larvaedensities. Preliminary results showed that amean of l97o (mtn. = 9.3, max. = 27) of thepilas maintained copepod populations during the6-month stttdy. Mesocyclops longiselrrs was notable to successfully reproduce in these contain-ers; of 200 females initially introduced per pila,only a mean of 23.2 (min. : 10.2, max. : 38.7)copepods was present 6 months later. Compari-sons of larval densities between treated and con-trol pilas did not show statistical differences.

SsPTEr4sen Moseur.ro VEcroR Svvposruv 351

Likely explanations for these results may be at-tributed to poor community participation, fre-quent washing of the pilas, and drainage of thewater through a hole in the bottom of the pila.

Field evaluation of Mesocyclops longisetus(Copepoda: Ciclopoidea) in controlling larval

populations of Aedes aegypti inMonterrey, Mexico

N. Gorrochotegui-Escalante

Laboratorio de Entomologia Mddica,FCB-UANL, Monterrey, Nuevo Le6n, Mexico

Mesocyclops longisetus (Thi6baud) has shownpotential as a biocontrol agent for reducing lar-val populations of the dengue vector Aedes ae-gypti (Linn.). Field tests in Honduras proved theeffectiveness of M. longisetus in peridomesticbreeding sites; however, considering differencesin breeding sites and in general larval ecologyfrom a tropical region versus a temperate areasuch as northeastern Mexico, effectiveness of ci-clopoids could vary. Therefore, this study wasaimed at determining reduction in mosquito lar-val density by copepods and copepod survivor-ship when assisted by community participationin breeding sites of epidemiological importancein Monterrey, Mexico. Field tests were conduct-ed in Colonia El Mirador, San Nicolas de losGarza, Nueva Leon, Mexico. Two hundred ovi-gerous M. longisetus females were introduced ineach of 60 55-gallon drums in several dwellings.In 40 of these drums, people were allowed touse water as they ordinarily did. Also, a markerwas placed in the bottom to remind residentsthat they were taking care of copepods duringdrum washing. In the remaining 20 drums, wateruse was not permitted by the residents in orderto determine the survivorship rate of M. longi-setus in this aquatic environment. Controls wereincluded for both of these groups. At the sametime, 50 abandoned tires in backyards were eachtreated with 50 ovigerous female M. longisetusand 2O tires served as untreated controls. A 3rdbreeding site that was included was flower vasesin the city cemetery. Fifty flower vases wereeach treated with 50 female copepods and 30were used as controls. Fortnightly sampling ofonly larval populations occurred in all breedingsites from May to September 1994. At the endof the study, copepods were removed and count-ed to assess survivorship, reproduction rate, andlarval control. After 4 months, copepods werepresent in 9OVo of the drums where water wasintensively used. The success of this programwas supported by community participation.However, farval reduction was only 37.5Vo indrums where people utilized the water. A similar

reduction (39.9Vo) of dengue vector populationswas found in drums where people did not usethe water. Many (547o) of the backyard tiresmaintained copepod populations during almost 4months, but larval reduction corresponded onlyto 4O.97o. A greater effectiveness of M. longi-setus was found in cemetery flower vases, wherethey reduced larval populations up to 67Vo andsurvived in 9OVo of treated vases during a 4-month period. Reproduction of ciclopoids inflower vases produced a mean of 450 copepodsper vase, about 9 times more than initially intro-duced populations. However, during the ceme-tery study, water had to be poured into vasesevery week because local precipitation in thissemiarid region was scarce. Our results indicatethat use of copepods to control Ae. aegypti pop-ulations may be of limited value in places witha short rainy season and with a poor nutritionalenvironment for copepods in metal drums.

Preliminary evaluation of Vavraia sp.(Microsporidia: Pleistophoridae) on

C ukx quinquefasciatus underlaboratory conditions

J. S. Zuluaga and S. Orduz

Corpo rac i6n para Investigaciones B iologicas,Medellin, Colombia

A microsporidian of the family Pleistophori-dae, genus Vavraia, was found infecting mos-quito larvae growing in bromeliads near the set-tlement of Jovi (Pacific coast of Choc6, Colom-bia). Mosquitoes found in bromeliads belongedto the genera Wyeomyia, Anopheles, and Ortho-podomyia. Natural infection of larvae by Va-vraia was 6.8Vo, afflicting Wyeomyia circum-cincta Dyar and Knab, WyeomTtia simmsi (Dyarand Knab), Anopheles neivai Howard, Dyar andKnab, and Orthopodomyia sp.

Laboratory-reared Culex quinquefasciatusSay larvae were subject to colonization by Va-vraia sp. Its life cycle was studied in the labo-ratory colony, where we observed meronts with2,4,8, 16, and 32 nuclei and sporonts contain-ing sporoblasts with 8, 16, 32, and 64 spores.Spores produced in Cx. quinquefasciatus wereegg-shaped, 4,78 '+ O.44 p.m long and 2,66 '+

0.23 pm wide. In the pathogenicity study, wedetermined the effect of increasing concentra-t ionsofs X 104, I x 105, 5 X l0s , I X 106, 5X 106, and I x 107 spores/ml on the longevityand fecundity of Cx. quinquefasciatus. We ana-lyzed the results using the MANCOVA test andthe Tukey significance test with a 95Vo confi-dence.

In the group of individuals that survived fromthe larval, pupal, and adult stages, we observed

352 JounNel oF THE AMERTcIN Mosqurro CoNTRoL AssocnrroN Vor. 11, No. 3

signiflcant differences only between the concen-trations of I x 105 and 5 X 106 spores/ml inpupae and adults. We analyzed longevity basedon the number of weeks during which 5OVo ofthe populations died and found no statistical dif-ferences. Fecundity was analyzed by observingthe number of egg rafts laid weekly by females;we observed significant differences between thecontrol group and the concentrations of 5 X 105and 5 x lff spores/ml. We determined the in-fection concentrations 50 and 90 (IC5o and ICru),which were 24,865 and 684,O26 spores/ml, re-spectively.

Characterization of Aedes aegyptibreeding sites in Panama according to the

population social stratum, pII, andbacterial contamination

A. Y. de Turneq G. Ddvila and C. Campos

Facultad de Medicina, Universidad de Panama,Panama City, Panama

To characterize the breeding sites of Aedes ae-gypti (Linn.) in the metropolitan area of PanamaCity during 1994, 3 counties with populationshaving different social characteristics were cho-sen. These were Curundu (extreme poverty), RioAbajo (lower and middle class), and Bella Vista(middle and upper class). The pH of the waterof 102 of the most frequently found breedingcontainers was recorded and 50 water sampleswere cultivated to determine the associated mi-croflora and levels of fecal contamination.

Results revealed the following:

l. Aedes aegypti breeding sites varied in accor-dance to the social stratum, with a definitetrend toward more nonusable breeding con-tainers in low income areas and a higher pro-portion of usable breeding containers asso-ciated with areas having better social condi-tions. However, there was a large number ofpotential breeding sites in areas from all so-cial strata.

2. 'fhe most abundant Ae. aegypti breeding siteswere of plastic, metal, and concrete in thecorregimiento of Rio Abajo.

3. The pH was not a critical factor in the breed-ing sites, varying from 5.0 to 8.0.

4. Some bacterial indicators of fecal contami-nation (e.g., Proteus, Enterobacter, Klebsiel-la) were found, even though the major indi-cator of fecal contamination, Echerichia coli,was not found. We concluded that eventhough Ae. aegypti is usually found breedingin relatively clean waters, its larva can tol-erate a variable degree of fecal contamina-tion.

Dengue next door-the Panama Canalresponse to the 1994 epidemic in

PanamaM. Boreham and G. D6vila de De Obaldia

Entomology Unit, Panama Canal Commission,Panama City, Panama

Over the past decade, dengue fever has be-come more frequent throughout Latin Americaand the Caribbean. Following the 1985 reinfes-tation of Aedes aegypti (Linn.), this dengue vec-tor spread throughout Panama City and to othercities and towns in the Republic of Panama. Ashouse indices rose in nearby urban districts, thePanama Canal Commission became concernedabout the possibility that a massive dengue ep-idemic could drastically affect the operation ofthe Panama Canal, as more than SOVo of the Ca-nal workforce lives in or near these areas.

On November 19, 1993, after some 5O yearsof being free from dengue, the Minister ofHealth of Panama confirmed that the first caseof this disease, in a suburban development onthe outskirts of Panama City, had been diag-nosed in the laboratory. Fourteen cases of DEN-2 were recorded in this neighborhood beforetransmission ceased in early December.

Prior to the outbreak, Commission publichealth and vector control officials had developeda comprehensive "dengue contingency plan"that centered on education of the Panama Canalworkforce about how dengue is transmitted, itssymptoms, and what to do if dengue was sus-pected. Agency-wide classes covering these top-ics were presented and educational fliers andpamphlets were distributed to all employees giv-ing "action lists" of what to do to prevent Ae.aegypti from breeding around the home. Com-munity and neighborhood cleanup campaignswere emphasized in employee newspaper arti-cles and recommendations were given on howto reduce the risk of contracting the disease.Panama Canal "larva hunter" teams were aug-mented to provide weekly vector surveillance,source reduction, and mosquito control withinCanal residential areas, Commission facilitiesand buildings, as well as adjacent housing areas.Close coordination was also maintained withU.S. military health and vector control officials,as well as diagnostic laboratory personnel, epi-demiologists, and vector control authorities ofthe Ministry of Health.

In July 1994, epidemic dengue (DEN-I) be-gan in an urban district of Panama City and rap-idly spread to other parts of the metropolitanarea. Peak transmission occurred in August andSeptember and the number of cases declinedfrom October through December. Separate out-

Moseurro Vrcron Svvpostutu 353

breaks took place in the province of Chiriqui(near the border with Costa Rica) and in the in-terior province of Herrera during the last 2months of the year. Remarkably, even thoughnear the entire population of Panama had notbeen exposed to dengue for 5 decades, onlyabout 800 cases of dengue were confirmed inthe Republic during this outbreak and no casesof hemorrhagic dengue or dengue shock syn-drome were observed.

To the best of our knowledge, none of theapproximately 8,500 Panama Canal Commissionemployees or their dependents became ill withdengue during this epidemic.

Evaluation of four different interventionsfor Aedes aegypti control in Merida,

Yucatan, Mexico

J. Mendez-Galvan, L. Rivas-Gutierrez,M. Capetillo-Pazos, M. Narvaez,S. Canto-Celis, G. Pacheco-Can,

H. Gomez-Dantes, C. R. Munoz-Barahonaand R. Tapia-Conyer

Direccion General de Epidemiologia,Secretaria de Salud, Mexico City; ProgramaEspecial de Participacion Comunitaria para

Control de Dengue, Merida, Yucatan; andServicios Coordinados de Salud Publica del

Estado, Yucatan, Merida, Mexico

During a clean-up campaign that was held toeliminate breeding sites in the city of Merida,Yucatan, 4 different educational and promotion-al interventions were promoted to help the com-munity identify and eliminate those Aedes ae-gypti (Linn.) breeding sites, defined as disposa-ble containers. These interventions were done in4 neighborhoods with similar features to findwhich approach resulted in continuous commu-

nity participation for dengue prevention andcontrol. The first was an educational game or"rally" involving children at an elementaryschool. The 2nd involved a person in a costume

who promoted the prevention message with aloud speaker and musical songs designed to in-crease popular participation. This interventionalso had newly developed educational posters.The 3rd intervention was a combination of the2 previously described strategies. The 4th inter-vention was the traditional campaign, used forover l0 years, with a loud speaker and distri-bution of leaflets. The leaflets were distributedin all neighborhoods.

At the same time, polls studied change in thepeople's knowledge and practice about this sub-ject. When comparing the results of the tradi-tional campaign with the other 3 interventions,there was a significant difference in the reduc-tion of "disposable" breeding sites, dependingon which strategy was applied. Results fromthese interventions suggest that the evaluation ofcontainers (breeding sites), as well as the meth-ods of promotion and education, can help in theidentification and elimination of target contain-ers in a cleanup campaign for Ae. aegypti con-trol.

REFERENCES CITED

Clark, G. G. and M. R Suarez (organizers). 1991.Mosquito vector control and biology in Latin Amer-ica-a symposium. J. Am. Mosq. Control Assoc. 7:633-645.

Clark, G. G. and M. R Suarez (organizers). 1992.Mosquito vector control and biology in Latin Amer-ica-a second symposium. J. Am. Mosq. ControlAssoc .8 :305-317.

Clark, G. G. and M. F Suarez (organizers). 1993.Mosquito vector control and biology in Latin Amer-ica-a third symposium. J. Am. Mosq. Control As-soc.9:441453.