The specific concept of two triatominae species of epidemiological importance in the Mato Grosso Region (Brasil), Triatoma guazu Lent & Wygodzinsky, 1979 and Triatoma jurbergi Carcavallo, Galvão & Lent, 1998, the antenniferous tubercle and the four antennal segments of nymphs from the first to fifth instar were morphologically compared by scanning electron microscopy. The main differences observed were that the antenniferous tubercle in T. guazu did not present a smaller tubercle in the base of the larger tubercle. The first antennal segment in the fifth instar had sensilla distributed with an alternating array and the trichobothria in the first instar had half of its length reaching the third antennal segment. However, in T. jurbergi the antenniferous tubercle had two smaller tubercles in the base of the two larger tubercles. The first antennal segment in the fifth instar presents sensilla distributed in pairs, and the trichobothria in the first instar has only a small portion of the structure reaching the third antennal segment. These structures differentiated the nymphs of T. guazu and T. jurbergi.

The thermopreference of resting P. megistus (Burmeister, 1834) adults was studied in a temperature gradient. We also determined the thermopreference for oviposition and ecdysis. Thermopreference of resting individuals depended on the feeding state of the insects. Results demonstrated an initial resting preference of ≈29°C, which gradually changed to 26–27°C with increasing starvation. A daily variation in thermopreference was also observed with this species. The insects showed a daily maximum preference at the beginning of the dark phase, and a minimum preference during the first half of the light phase. Ecdysis took place all along the gradient, but exhibited a maximum frequency at 30°C. Most eggs were found between 25 and 29°C. Results are discussed in relation to the ecology of P. megistus as compared with other related species, and the existence of mechanisms of behavioral thermoregulation in the group.

Esterases are often used to measure genetic variation, yet they may be influenced by external factors. Isoelectrofocusing was used to investigate the effects of bloodmeal on the esterase variation in wild populations of Phlebotomus (Larroussius) ariasi Tonnoir and P. (L.) perniciosus Newstead and in a colonized population of P. (Phlebotomus) duboscqi Neveu-Lemaire. Modified electrophoretic profiles were demonstrated to be associated with blood digestion. The bloodmeal-induced esterase electromorphs were only found in the abdomen homogenates of the sand flies. These changes in esterase phenotype were probably due to a proteolysis phenomenon and disappeared at the end of bloodmeal digestion. The effect was eliminated by adding trypsin inhibitors.

Unfed adult Ixodes scapularis Say were treated with spores of the entomopathogenic fungus Metarhizium anisopliae Metschnikoff in the laboratory and in the field. An M. anisopliae suspension containing 4 × 10⁹ spores per milliliter caused 96% mortality in the laboratory, versus 53% mortality among field-treated ticks. The LC₅₀ value for unfed adult I. scapularis in the laboratory was 4 × 10⁷ spores per milliliter. Our results indicate that M. anisopliae was highly pathogenic to unfed adult ticks and showed potential for controlling questing adult I. scapularis.

This study was aimed at clarifying the nature of the resistance to Bacillus sphaericus Neide (Bs) that Culex pipiens L. has developed in west Mediterranean countries, France, and Tunisia. Two recessive and sex-linked mutants, sp-1^R and sp-2^R, were previously detected in southern France. Here, the Tunisian resistance was also shown to involve a single recessive and sex-linked gene that was temporarily named sp-T^R. In addition, sp-1^R, sp-2^R, and sp-T^R were shown to separately confer a similar high resistance level (>5,000-fold) in the homozygous state. Knowing that sp-1^R resistance does not alter the binding of Bs binary toxin to its specific receptor, we investigated this character in sp-2^RR and sp-T^RR homozygotes. This was performed by in vitro experiments in which larval brush border membrane fractions (BBMF) were exposed to the ¹²⁵I-Bin2 toxin of B. sphaericus strain 1593. The toxin-receptor binding was found disrupted by sp-2^R but not by sp-T^R. Comparing the binding kinetics among nine Culex pipiens strains of diverse origins revealed that the Bs receptors of sp-1^RR and sp-T^RR homozygous larvae were displaying the highest affinity toward Bs binary toxins. These results are discussed with regard to alternative assumptions on the dynamics of high Bs-resistance and on the emerging possibilities to test them in a near future.

Four stereoisomers of p-menthane-3,8-diol, which make up the natural product obtained from Eucalyptus citriodora, were synthesized through stereoselective procedures. Repellency assays showed that all the four were equally active against Anopheles gambiae s.s. Racemic blends and the diastereoisomeric mixture of all the four isomers were also equally repellent. 1-α-terpeneol, with a single hydroxyl function at C-8 and unsaturation at C-8, and menthol, with a single hydroxyl function at C-3, were not repellent. The practical implication of these results is discussed.

Eleven cat flea, Ctenocephalides felis (Bouchè), strains, seven field-collected and four laboratory-colonized, were assayed for susceptibilities to five insecticides (carbaryl, chlorpyrifos, malathion, permethrin, and pyrethrin) with an insecticide-treated, horizontally-oriented, Nylon 6,6 disk in a test tube. The pyrethrin was synergized using piperonyl butoxide (PBO). Flea mortality at two doses was recorded after 4 and 24 h exposures. The field strains from Texas and Florida tolerated carbaryl, chlorpyrifos, and malathion; and carbaryl and PBO-synergized pyrethrin, respectively. Tolerance was observed in a field strain from Kansas against malathion. Colonies from California and North Carolina were susceptible to malathion and PBO-synergized pyrethrin, and chlorpyrifos and permethrin, respectively, but three colonies showed tolerance. The insecticidal response of the California colony varied; when exposed to a chlorpyrifos dose of 10 mg (AI)/m² for 24 h, at various times had mortality of 3–100%. With a PBO-synergized pyrethrin dose of 396 mg (AI)/m² for 4 h, the mortality ranged between 4.2 and 97%. Colonized strains were more susceptible than field strains at 4 h exposure to all insecticides except PBO-synergized pyrethrin. Colonized strains survived better in control tubes. The colony strains’ susceptibility and variability are of considerable importance because these strains are used for flea product efficacy evaluations and bioassays. The differences in susceptibility between laboratory colonies and the field strains suggested development of both adaptation to colonization, and extensive, multiple cross-resistance to insecticides in field strains. Varying susceptibility of cat fleas may affect control success.

A field study was conducted from 1991 through 1997 to evaluate the use of pyrethroid and organophosphate (OP) ear tags, alternated yearly, for the control of a pyrethroid resistant horn fly, Haematobia irritans (L.), population in Louisiana. Fly resistance was monitored by weekly fly counts, filter paper bioassays and diagnostic polymerase chain reaction (PCR) assays for the presence of pyrethroid resistance-associated mutations in the sodium channel gene coding region. Fly control in the first study year was poor, as pyrethroid ear tags were effective for only 7 wk. The following year, OP ear tags provided 15 wk of fly control. However, in all subsequent years, fly control was poor with both types of ear tags. The PCR assays showed that there were very few female flies homozygous for the pyrethroid susceptible sodium channel allele, never rising above 10% of the total females in the population. A fitness cost appeared to be associated with the pyrethroid resistant allele, as the resistant form was selected against in the absence of the pyrethroid ear tags. Despite this selection in favor of the susceptible allele and the annual alternation of pyrethroid and OP ear tags, the percentage of homozygous susceptible flies never reached over 19% of the population, resistant alleles of the sodium channel remained at high levels in the population, and horn fly control on cattle with either type of tag quickly became minimal.

This study tested the efficacy of permethrin-impregnated mattress liners in reducing house dust mites in the homes of volunteers with no previous recorded history of asthma, atopic eczema, or perennial rhinitis. The field trial using permethrin-impregnated (450 mg/m² of pure permethrin in polyester netting weighing 35 g/m²) mattress liners (n = 9) was conducted for 27 mo. The permethrin-impregnated bedding significantly reduced house dust mites in mattresses for at least 27 mo. Allergen concentrations were significantly lowered at 15-mo postintervention. No adverse side-effects were reported. This is a promising development in house dust mite control.

The efficacy of pour-on formulations of three macrocyclic lactone endectocides (moxidectin, ivermectin, and eprinomectin) was evaluated on cattle against Boophilus microplus (Canestrini) using two different treatment regimes. A single application treatment regime with each endectocide showed that fewer ticks per calf were recovered from all treated calves than from untreated cattle, but the level of control among the three treatments was similar (range; 78.7–87.7%) against all stages of ticks on the calves at the time of treatment. The engorged female and egg mass weights of all treated ticks were less than that of untreated ticks. Among the treated groups, the ivermectin and eprinomectin-treated females weighed less and produced lower weight egg masses than those from moxidectin-treated cattle. In a double application treatment regime with a 4-d interval between treatments, there were fewer ticks per calf recovered from the treated cattle than from untreated cattle. In addition, all treated females weighed less and produced lower weight egg masses than those from untreated cattle. Control with moxidectin (90.3%) was lower than with either ivermectin (98.9%) or eprinomectin (99.7%). The mean female and egg mass weight of the ivermectin and eprinomectin-treated groups was also less than that of the moxidectin treatment. A single application treatment against either 18- or 20-d-old adult ticks indicated that both moxidectin and ivermectin were less effective against 20-d-old ticks that were nearer to completing their parasitic development on the animal. In contrast, eprinomectin was the only endectocide tested that was equally effective against both 18- and 20-d-old ticks.

Polymerase chain reaction (PCR) diagnostic assays were used to identify possible resistance-associated roles of two amino acid substitutions found in pyrethroid resistance-associated genes of Boophilus microplus (Canestrini). Individual larvae from the San Felipe target site resistant strain and the Coatzacoalcos (Cz) metabolic resistant strain were separated into resistant and susceptible groups by larval packet bioassays and analyzed by PCR. A Phe → Ile amino acid mutation in the sodium channel gene S6 transmembrane segment of domain III was found to have a close association with survival of acaricide treatments containing as high as 30% permethrin. As the permethrin dose was increased, an increase was seen in the proportion of surviving larvae that possessed two mutated sodium channel alleles. An Asp → Asn amino acid substitution, originally found in high allele frequency in alleles of the CzEst9 esterase of the Cz strain, appeared to provide some resistance to permethrin. However, the presence of the mutation did not associate with resistance in the dose–response fashion seen with the sodium channel amino acid mutation. Resistance provided by CzEst9 might be more dependent on concentration of CzEst9 more so than the presence of a mutated allele.

The host-feeding patterns of mosquitoes (n = 247) collected in the Borough of Queens in New York City in July and August 2000 were investigated using an indirect ELISA and a polymerase chain reaction (PCR)-heteroduplex assay. Culex pipiens L. and Cx. restuans Theobald fed primarily on birds, and their feeding habits support their implication as enzootic vectors of West Nile virus. Culex salinarius Coquillett and Coquillettidia perturbans (Walker) fed mainly on mammals, with fewer blood meals taken from birds, and these two species are potential bridge vectors of West Nile virus. Culex mosquitoes took blood meals (n = 54) from 11 different avian species. Only the northern cardinal (Cardinalis cardinalis), American robin (Turdus migratorius), and Brown-headed cow bird (MolIothrus ater) were fed upon by all three Culex species. Multiple blood feedings on avian hosts were detected in Cx. pipiens and Cx. restuans. Species identifications of Culex mosquitoes made using morphological characteristics were confirmed with a PCR assay that employed species-specific primers. All Cx. pipiens (n = 20) and Cx. salinarius (n = 10) specimens were correctly identified, but three (20%) of 15 Cx. restuans were misidentified as Cx. pipiens.

As part of investigations into Japanese encephalitis (JE) virus and related flaviviruses in northern Australia, 153,529 mosquitoes were collected and processed for virus isolation from the Gulf Plains region of northwest Queensland. Collections from within 30 km of each of the townships of Croydon, Normanton and Karumba yielded 3,087 (2.0%), 66,009 (43.0%), and 84,433 (55.0%) mosquitoes, respectively, from which 16 viruses were isolated. Four isolates of Murray Valley encephalitis (MVE), two of Kunjin (KUN), three of Ross River (RR), and one of Sindbis (SIN) viruses were obtained from Culex sitiens subgroup mosquitoes. Molecular identification of the mosquito species composition of these virus positive pools revealed that most isolates were from pools containing mainly Culex annulirostris Skuse and low numbers of Culex palpalis (Taylor). Only three pools, one each of MVE, KUN, and RR, were from mosquitoes identified exclusively as Cx. annulirostris. Other viruses isolated include one Edge Hill virus from Ochlerotatus normanensis (Taylor), an isolate of SIN from Anopheles meraukensis Venhuis, two isolates of RR from Anopheles amictus Edwards, and single isolates of RR from Anopheles bancroftii Giles and Aedes lineatopennis (Ludlow). The isolate of RR from Ae. lineatopennis was the first reported from this species. The public health implications of these isolations in the Gulf Plains region are discussed briefly.

The introduction of a St. Louis encephalitis virus (SLE) genotype new to southeastern California during 2000 was followed by focal enzootic amplification in the Coachella Valley that was detected by seroconversions of 29 sentinel chickens in five of nine flocks of 10 chickens each, isolations of virus from 30 of 538 pools of 50 Culex tarsalis Coquillett females, and collection of 30 positive sera from 2,205 wild birds. This SLE strain over wintered successfully and then amplified during the summer of 2001, with 47 sentinel seroconversions in eight of nine flocks, 70 virus isolations from 719 pools of Cx. tarsalis and Cx. p. quinquefasciatus Say, and 40 positive sera from 847 wild birds. Human illness was not detected by passive case surveillance, despite issuance of a health alert during 2001. Virus amplification during both years was associated with above average temperatures conducive for extrinsic incubation and below average precipitation during spring associated with below average vector abundance. Seroconversions by sentinel chickens provided the timely detection of virus activity, with initial conversions detected before positive mosquito pools or wild bird infections. Vertical infection was not detected among Cx. tarsalis adults reared from immatures collected during the fall-winter of 2000, even though SLE over wintered successfully in this area. Early seroconversions by a sentinel chicken during February 2001 and a recaptured Gambel’s quail in April 2001provided evidence for transmission during winter and spring when ambient temperatures averaged below 17°C, the threshold for SLE replication.

We evaluated the effect of triethylamine (TEA) on the recovery of infectious virus from pools of mosquitoes for two South American alphaviruses (eastern equine encephalomyelitis and Venezuelan equine encephalomyelitis subtypes IIIC and ID), one flavivirus (Ilheus) and two bunyaviruses (Mirim [Guama group] and Itaqui [group C]). Mosquitoes were inoculated intrathoracically with virus, held for 7–10 d at 26°C, and handled under one of four regimens before testing for the presence of virus by plaque assay. Mosquitoes were killed by freezing at −70°C for 3 min and tested immediately for the presence of virus; killed by freezing at −70°C for 3 min and then held at room temperature for 1 h before testing for the presence of virus; anesthetized with TEA and assayed immediately for the presence of virus; or anesthetized with TEA and then held at room temperature for 1 h before being assayed for the presence of virus. For each of the viruses tested, viral titers in mosquitoes anesthetized with TEA were similar to those in mosquitoes killed by freezing at −70°C. Likewise, there was no significant difference in viral titers in mosquitoes anesthetized with TEA and held at room temperature for 1 h or in mosquitoes frozen at −70°C and held at room temperature for 1 h before being processed for virus by isolation. Triethylamine is advantageous for the handling of mosquitoes in a field environment. The elimination of the need for a cold chain, without compromising virus recovery, increases the feasibility of conducting research projects requiring the isolation of live virus from mosquitoes in remote tropical environments.