Showing papers in "Journal of Medical Entomology in 1988"
TL;DR: A direct enzyme-linked immunosorbent assay (ELISA) was developed for bloodmeal identification of seven hosts and a system was developed whereby a single mosquito could be tested by both the blood meal ELISA and the malaria sporozoite ELISA.
Abstract: A direct enzyme-linked immunosorbent assay (ELISA) was developed for bloodmeal identification of seven hosts. Commercially available reagents are used; the test can be completed in only 4.5 h. Blood meals can be detected up to 32 h after feeding for dried mosquitoes and up to 23 h for frozen mosquitoes. A two-step procedure, using antihuman peroxidase conjugate and antibovine phosphatase conjugate, was developed to test a single mosquito for two hosts in the same microtiter plate well. The assay was applied to Anopheles gambiae Giles s. lat. and A. funestus Giles collected inside huts in western Kenya; 94% of 4,338 blood meals were identified as either human (88%), cow (4%), or mixed humancow (2%). Additionally, a system was developed whereby a single mosquito could be tested by both the blood meal ELISA and the malaria sporozoite ELISA.
316 citations
TL;DR: It is concluded that the presence of deer is a precondition for dense infestations of I. dammini and hence for intense transmission of Lyme disease and human babesiosis.
Abstract: We determined whether a dense infestation of Ixodes dammini Spielman, Clifford, Piesman & Corwin, the tick that locally transmits Lyme disease and human babesiosis, depends upon the presence of deer. This host was removed from a tick-infested land mass located on Cape Cod, Mass., and the abundance of the tick was monitored. Larval ticks became less abundant beginning in the summer following removal of deer, indicating that the adults of this species generally failed to feed and reproduce. The abundance of nymphal ticks declined more gradually. We conclude that the presence of deer is a precondition for dense infestations of I. dammini and hence for intense transmission of Lyme disease and human babesiosis.
185 citations
TL;DR: Although I. scapularis was a competent laboratory vector for Borrelia burgdorferi, natural populations of this tick taken from white-tailed deer and white-footed mice in Alabama were not infected with spirochetes.
Abstract: The ability of the immature stages of three tick species from the southeastern United States to acquire, maintain, and transmit Borrelia burgdorferi was determined under laboratory conditions. Dermacentor variabilis (Say) and Amblyomma americanum (L.) acquired spirochetal infection as larvae, but infection in D. variabilis (9% infected) and A. americanum , (1% infected) was inefficient and short lived. In contrast, Ixodes scapularis Say infected as larvae maintained spirochetal infection transstadially, and infected I. scapularis nymphs transmitted spirochetes to hamsters in four out of four trials. Although I. scapularis was a competent laboratory vector, natural populations of this tick taken from white-tailed deer and white-footed mice in Alabama were not infected with spirochetes.
163 citations
TL;DR: An artificial feeding system for adult cat fleas, Ctenocephalides felis (Bouche), in conjunction with standard larval and pupal rearing techniques has resulted in a colony that has completed 14 artificially reared generations at the time of writing.
Abstract: An artificial feeding system for adult cat fleas, Ctenocephalides felis (Bouche), is described. Survival and reproductive success of artificially fed fleas were attributed to continuous provision of blood at 37°C and a substrate that allowed the fleas to walk but not to jump. Fleas were confined for artificial feeding in three different kinds of cages, all of which were cylinders of clear plastic with nylon mesh cemented across both ends. The cages differed in dimensions and in the inclusion or lack of hair. The upper end of the cage was apposed to a Rutledge insect blood feeder supplied with a Parafilm membrane through which the fleas were able to feed on cattle or dog blood. Artificially fed fleas yielded equivalent survival rates and 13–19% the reproductive output of fleas fed on cats. This system in conjunction with standard larval and pupal rearing techniques has resulted in a colony that has completed 14 artificially reared generations at the time of writing.
112 citations
TL;DR: The positive response previously attributed to a larva-produced oviposition pheromone was the result of bacterial contamination of assayed media, and preventing bacterial growth during the holding and assay periods resulted in significant repellency of larval holding water compared to distilled water.
Abstract: A sequence of behavioral assays was performed in the laboratory to ascertain the contribution of bacteria to the oviposition response of gravid Aedes aegypti to water that previously had held fourth-instar larvae. Experiments using larval holding water with no control over bacterial growth showed an increasing oviposition response with increasing larval densities up to about two larvae per ml, beyond which the response decreased. Glutting larvae with kaolin prior to the preparation of holding water did not significantly reduce bacteria or the oviposition response at one larva per ml. Removing bacteria prior to assay decreased the response, and preventing bacterial growth during the holding and assay periods resulted in significant repellency of larval holding water compared to distilled water. It is concluded that the positive response previously attributed to a larva-produced oviposition pheromone was the result of bacterial contamination of assayed media. Two dominant species of bacteria, Acinitobacter calcoaceticus and Enterobacter cloacae , were identified in holding water. A pure suspension of A. calcoaceticus induced a significantly higher oviposition response than a pure suspension of E. cloacae . Additional assays with A. calcoaceticus showed that both contact-stimulation and olfaction may be involved. The ecological implications of a larva-produced repellent and bacteria-produced stimulants-attractants are discussed.
98 citations
TL;DR: Using a refined indirect enzyme-linked immunosorbent assay to identify serum proteins of different host species, the blood meal sources and the amount of multiple blood feeding among heterologous host species were investigated for members of the Anopheles punctulatus complex in Papua, New Guinea.
Abstract: Using a refined indirect enzyme-linked immunosorbent assay to identify serum proteins of different host species, the blood meal sources and the amount of multiple blood feeding among heterologous host species were investigated for members of the Anopheles punctulatus complex in Papua, New Guinea. Differences in host preferences were found among members of the complex; A. punctulatus and A. koliensis were more anthropophilic than A. farauti. Blood from two or more hosts species was detected in 5.2% of the engorged anophelines captured outdoors and in 4.3% of those captured indoors. Based on ABO blood group markers on human red blood cells, 13% of human fed anophelines captured indoors in experiments with selected mother-child pairs contained blood of both individuals. A model is presented that predicts the probability of a mosquito being interrupted while blood feeding. The epidemiological implications of the findings are discussed.
94 citations
TL;DR: The trapping efficiency for stable flies, Stomoxys calcitrans (L.), of Alsynite plastic traps of a new cylindrical design was evaluated against Williams traps made of the same plastic; the new trap is equal to the Williams trap in trapping house flies, Musca domestica L.
Abstract: The trapping efficiency for stable flies, Stomoxys calcitrans (L.), of Alsynite plastic traps of a new cylindrical design was evaluated against Williams traps made of the same plastic. The cylindrical traps (30 cm diameter, 30 cm high) and Williams traps with two plastic panels (60 by 30 cm) were equally effective in trapping stable flies; however, the former had a greater trapping efficiency (flies per surface area) because of its lesser surface area. The new trap requires less and thinner (hence cheaper) Alsynite plastic and less adhesive than the Williams trap. It is equal to the Williams trap in trapping house flies, Musca domestica L.; thus there is no disadvantage associated with the unwanted attraction of the house fly. The diameter of the cylindrical trap directly affected the number of stable flies caught. Stable flies landed predominantly on the areas of the trap most protected from the wind.
91 citations
TL;DR: This method revealed qualitative and quantitative differences in gut contents among fourth instars of Aedes triseriatus, Anopheles quadrimaculatus Say, and Coquillettidia perturbans and is applicable to gut content analysis of other filter-feeding arthropods.
Abstract: A method using 4'6-diamidino-2-phenylindole (DAPI) stain and epifluorescence microscopy for analyzing the food ingested by mosquito larvae is described. When stained with DAPI, food items (organic detritus, bacteria, algae, and protozoans) can be identified by fluorescence, color, and shape. Bacteria appear blue and protozoans light blue with a distinct nucleus, organic detritus autofluoresces dull yellow, chlorophyll in algae appears dull red, and algal nuclei are blue. This method revealed qualitative and quantitative differences in gut contents among fourth instars of Aedes triseriatus (Say), Anopheles quadrimaculatus Say, and Coquillettidia perturbans (Walker). The method is applicable to gut content analysis of other filter-feeding arthropods.
84 citations
TL;DR: From March to November 1985 and March to October 1986, white-tailed deer were examined for ticks at Land Between the Lakes (LBL) in western Kentucky and Tennessee to find no Dermacentor variabilis (Say) on deer, even though this tick is common throughout LBL.
Abstract: From March to November 1985 and March to October 1986, we examined 97 white-tailed deer (approximately 6 deer per month) for ticks at Land Between the Lakes (LBL) in western Kentucky and Tennessee. The largest monthly half-body mean densities ($\bar x$ ± SE) of Amblyomma americanum (L.) were 66.8 ± 22.2 females and 147.7 ± 60.1 males in May, 479.2 ± 329.6 nymphs in June, and 1,493 ± 114.7 larvae in August. A. americanum attached to all body regions; however, adults attached mainly to the outer ear, head, udder, and escutcheon; nymphs to the inner and outer ear; and larvae to the inner and outer ear and foreleg. The ear alone (inner and outer combined) had 54% of the females, 67% of males, 97% of nymphs, and 81% of larvae. Significantly different densities were found on the left side versus right side of the body for adult and larval A. americanum. We found no Dermacentor variabilis (Say) on deer, even though this tick is common throughout LBL. Regression models were developed using counts of ticks attached to selected body regions as predictors of A. americanum density on deer. Use of the density estimators contributes greatly to the interpretation of sampling results.
78 citations
TL;DR: Serological assays were used to identify bloodmeal sources of 24 species of mosquitoes collected in primarily natural habitats in Duplin County, North Carolina during 1984 and 1985, and quinquefasciatus was the only mosquito species that fed in significant numbers on chickens and turkeys, although large numbers of poultry were present.
Abstract: Serological assays, using antisera produced against host serum proteins, were used to identify bloodmeal sources of 24 species of mosquitoes collected in primarily natural habitats in Duplin County, North Carolina during 1984 and 1985. Culex peccator fed almost exclusively on snakes and frogs. Cx. territans fed on reptiles and amphibians. Aedes triseriatus and Ae. canadensis fed primarily on turtles. Psorophora ferox, Ae. atlanticus , and Ae. fulvus pallens fed primarily on various mammals. Cx. quinquefasciatus, Cx. restuans, Culiseta melanura , and Ae. dupreei fed primarily on passerine birds. Cx. quinquefasciatus was the only mosquito species that fed in significant numbers on chickens and turkeys, although large numbers of poultry were present. Cx. erraticus and several other species fed opportunistically on a variety of hosts. Seasonal or geographical host-feeding variability was not apparent in any of the species investigated. Multiple feeding occurred at a low rate (<0.2%).
77 citations
TL;DR: Results indicate that these larvae drink the surrounding medium, and failure of this toxin to bind to midgut cells of certain mosquito species may be responsible for the restricted host range of B. sphaericus.
Abstract: Fluorescent-labelled Bacillus sphaericus (Neide) toxin was found to bind to sharply delineated regions of the proximal lobes of the gastric caecum and the posterior midgut of susceptible Culex quinquefasciatus Say larvae but did not bind to midgut cells of resistant Aedes aegypti (L.) and A. triseriatus (Say) larvae. Failure of this toxin to bind to midgut cells of certain mosquito species may be responsible for the restricted host range of B. sphaericus . The toxin appeared to enter the cells of C. quinquefasciatus larvae by receptor-mediated endocytosis, and it accumulated in the cells in bright fluorescent endocytic vesicles. Binding of fluorescent toxin to C. quinquefasciatus midgut cells and activity of the toxin to these larvae in bioassays was reduced by a lectin, wheat germ agglutinin. C. quinquefasciatus larvae ingested the toxin from clean water, and toxin passed through a column of kaolin in the larval gut to bind to midgut cells and intoxicate the larvae. A. aegypti larvae similarly ingested fluorescent-labelled toxin and other proteins from clean water. These results indicate that these larvae drink the surrounding medium.
TL;DR: A personal protection system consisting of an extended-duration repellent formulation containing 35% N,N-diethyl-m-toluamide (deet) and a permethrin-treated battle dress uniform was tested against Culiseta impatiens at Galena, Alaska.
Abstract: A personal protection system consisting of an extended-duration repellent formulation containing 35% N,N-diethyl-m-toluamide (deet) and a permethrin-treated battle dress uniform (0.125 mg permethrin [AI]/cm2) was tested against Culiseta impatiens (Walker) at Galena, Alaska. Participants wearing the system received 1 mosquito bite per h (99.9% protection), whereas those with an untreated uniform and no repellent received 1,188 mosquito bites per h. Deet alone provided greater than 99% protection (4 mosquito bites per h) for more than 8 h, whereas the permethrin-treated uniform alone provided 93% protection (78 mosquito bites per h).
TL;DR: Chrysomya megacephala (F.) and Chrysomya rufifacies (Macquart) were collected in La Paz, Baja California in February 1987, the first record for the former species in North America and for the latter species in that state of Mexico.
Abstract: Chrysomya megacephala (F.) and Chrysomya rufifacies (Macquart) were collected in La Paz, Baja California in February 1987. This is the first record for the former species in North America and for the latter species in that state of Mexico. The status of Chrysomya spp. in the New World is discussed.
TL;DR: The diel questing behavior of adult Ixodes pacificus Cooley and Kohls was examined in relation to meteorological and seasonal factors in outdoor arenas in northern California and positively correlated with relative humidity and negatively correlated with ambient temperature and light and soil surface temperature.
Abstract: The diel questing behavior of adult Ixodes pacificus Cooley and Kohls was examined in relation to meteorological and seasonal factors in outdoor arenas in northern California. Vertical wooden dowels 25, 50, and 75 cm high were provided as potential questing sites. Questing behavior of males and females was positively correlated with relative humidity and negatively correlated with ambient temperature and, to a lesser degree, with light and soil surface temperature. The most frequent questing posture was with the capitulum directed upward. After choosing a questing site, both sexes moved little; most movement occurred nocturnally. Male ticks exposed to direct sunlight stopped questing earlier in the day than those in shade. Questing occurred mainly near the tips of the 25- and 50-cm dowels, averaging 24.7 cm (range, 23.6–25.0 cm; n = 81) and 47.2 cm (25.0–50.0 cm, n = 64), respectively, whereas the mean questing height was not as close to the tip (mean, 54.7 cm; range 27.0–75.0 cm; n = 55) on the 75-cm dowels. Females selected the 25- and 50-cm dowels as questing sites significantly more often than 75-cm dowels. The distribution of ticks of both sexes on 25- and 50-cm dowels was clumped.
TL;DR: These are the earliest dates reported for head lice on personal combs found in Israel from the first century B.C. to the eighth century A.D.
Abstract: Head lice, Pediculus humanus capitis De Geer, and their eggs were discovered on 12 out of 24 hair combs recovered during archaeological digs in the Judean and Negev Deserts of Israel. The finds were dated from the first century B.C. to the eighth century A.D. These are the earliest dates reported for head lice on personal combs.
TL;DR: Borrelia burgdorferi had the greatest affinity for embryonic R. appendiculatus cells and the least for D. variabilis cells, and high spirochete concentrations elicited cytopathic effects—loss of surface membrane extensions, rounding up, detachment, and lysis.
Abstract: Borrelia burgdorferi, strain 297, was incubated with tick cell lines isolated from Rhipicephalus appendiculatus (Neumann), R. sanguineus (Latreille), Anocentor nitens (Neumann), Dermacentor variabilis (Say), and Boophilus microplus (Canestrini). A tick cell culture medium, L-15B, was modified by the addition of gelatin and N'-acetylglucosamine (L-15B/S) to permit the cocultivation of B. burgdorferi and tick cells. Spirochetes continuously passaged axenically in L-15B/S had longer population doubling times (27.1 ± 4.5 h) than those grown in BSK medium (11.7 ± 2.2 h), which was unsuitable for tick cells. Growth of spirochetes cocultured with five of six lines did not change, but when B. burgdorferi was incubated with R. sanguineus cells, the spirochetes disappeared and could not be detected after 1 wk. Spirochetes bound themselves to tick cells by one end within 30 min after being added to cultures. Not all spirochetes attached to tick cells nor did all cells of a given line bind spirochetes. B. burgdorferi had the greatest affinity for embryonic R. appendiculatus cells and the least for D. variabilis cells. Scanning electron microscopy revealed numerous intertwined, coiled spirochetes attached to foci at the surface of R. appendiculatus cells, apparently causing the formation of round bodies. Fewer spirochetes attached to A. nitens cells. High spirochete concentrations (>107 per ml) elicited cytopathic effects—loss of surface membrane extensions, rounding up, detachment, and lysis. This system should be applicable in the study of tick cell-spirochete interactions and the analysis of spirochete tropism and binding to tick cells.
TL;DR: Passage of ingested host antibody from the digestive tract into the hemolymph was examined in six species of mosquitoes and those species that exhibited marked antibody passage stayed on the host and fed for extended periods of time while simultaneously excreting red fluid from the anus (prediuresis).
Abstract: Passage of ingested host antibody (IgG) from the digestive tract into the hemolymph was examined in six species of mosquitoes. Mosquitoes were fed upon either an immune host (typhus-immune rat) or nonimmune host (control) rat. At selected intervals after ingestion, hemolymph samples and midgut contents were collected and assayed for specific rat IgG using indirect immunofluorescent assay techniques. Within 3 h after ingestion, antibody appeared in the hemolymph of Anopheles stephensi Liston, An. gambiae Giles, and An. albimanus Wiedemann. In these species, the persistence of host antibody was longer in the gut (24–48 h after ingestion) than in the hemolymph (18–24 h after ingestion). Host antibody was detected at low levels in the hemolymph of Culex pipiens L. at 3 h after ingestion but not thereafter. Antibody passage was undetectable in An. freeborni Aitken and Aedes aegypti (L.) Those species that exhibited marked antibody passage stayed on the host and fed for extended periods of time while simultaneously excreting red fluid from the anus (prediuresis). Mosquito species not displaying antibody passage fed relatively quickly, left the host, and exhibited little, if any, prediuretic activity while feeding.
TL;DR: Sera from scabies-infested rabbits contained antibodies that recognized at least six antigens in extracts produced from DF body material and three from DF fecal material, and control sera from nonallergic control patients who were skin test negative to DF and without scabies exhibited no IgE binding to any SS band.
Abstract: Sarcoptes scabiei var. canis (L.) (SS) was shown to share a high degree of cross-reactivity with the house dust mite, Dermatophagoides farinae Hughes (DF). Sera from scabies-infested rabbits contained antibodies that recognized at least six antigens in extracts produced from DF body material and three from DF fecal material. Likewise, rabbit antiserum to DF body and DF fecal extracts contained antibodies that recognized SS antigens. Sera from control rabbits reacted with DF body and SS extracts did not show antibodies to antigens in either extract. Six of nine SS antigens were cross-reactive with DF antigens. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS—PAGE) fraction profiles of SS exhibited at least 30 protein and peptide bands. Fifteen SS bands bound DF-specific immunoglobulin E (IgE) following incubation in sera from nine DF skin-test-positive patients with no history of scabies. The IgE binding varied within and among these patients. The sera of these patients also exhibited significant IgE levels to multiple DF antigens, as demonstrated by crossed radioimmunoelectrophoresis (CRIE) and immunoblotting. Control sera from nonallergic control patients who were skin test negative to DF and without scabies exhibited no IgE binding to any SS band.
TL;DR: Results suggest that nonblood-feeding insects, such as houseflies, play a role in VSV transmission and that black flies also serve as vectors.
Abstract: Field studies were conducted during an epizootic of vesicular stomatitis virus (VSV) in Colorado to further assess the possible role of insects in the transmission of VSV. Insects associated with domestic livestock were collected at 11 premises along the Front Range of the Rocky Mountains in Colorado during the 1982 epizootic of vesicular stomatitis. Insects were pooled by date, location, species, and sex and were processed for virus isolation in three cell culture systems. Thirty-four isolates of vesicular stomatitis virus, New Jersey serotype, were obtained from 51,036 insects. Of these, 27 isolates were from Musca domestica (126 pools/5,285 specimens), 5 from other nonhematophagous Diptera (56 pools/936 specimens), and 2 from unengorged black flies (Simuliidae) (55 pools/1,221 specimens). Results suggest that nonblood-feeding insects, such as houseflies, play a role in VSV transmission and that black flies also serve as vectors.
TL;DR: Results suggest that oxidases are responsible for a part of the resistance to deltamethrin and that some other mechanism, most likely knock-down resistance, is involved in resistance to this insecticide and to DDT.
Abstract: A strain of Culex quinquefasciatus collected in February 1986 in Bouake, Ivory Coast (West Africa), was tested for resistance to various insecticides. Low but consistent resistance ratios (RR = 3–4) were observed for five organophosphates and two carbamates. Use of the synergist S,S,S-tributylphosphorotrithioate (DEF) showed that esterases or glutathione-S-transferases played a major role in organophosphate resistance. Two highly active esterases, A2 and B2, were detected in Bouake mosquitoes. Selection with chlorpyrifos increased significantly the frequency of these enzymes, confirming that they are involved in organophosphate resistance. High resistance ratios to deltamethrin (RR = 62.5) and DDT (RR = 380) also were recorded. Only part of the deltamethrin resistance could be suppressed by piperonyl butoxide, and no part of the DDT resistance could be suppressed by this synergist or by chlorfenethol (DMC). These results suggest that oxidases are responsible for a part of the resistance to deltamethrin and that some other mechanism, most likely knock-down resistance, is involved in resistance to this insecticide and to DDT.
TL;DR: The occurrence of HJ virus, the differences in mosquito infection rates, and widespread epizootic disease during a year of low mosquito densities are used to develop a hypothesis on the distribution of multiple endemic foci of EEE virus in upstate New York.
Abstract: Mosquito and arbovirus surveillance activities have been routinely conducted in upstate New York since 1971. This report details the surveillance results during 1978–85. Minimal virus activity was detected in the first 4 yr of concentrated surveillance at Toad Harbor Swamp, Oswego County. In 1983, an outbreak of eastern equine encephalitis (EEE) resulted in one human and nine equine cases. The outbreak was preceded by an epiornitic of Highlands J (HJ) virus in 1982; this was the first evidence of HJ virus activity in the region. Isolations of EEE virus from mosquitoes in 1983 incriminated Culiseta melanura (Coquillett) and Cs. morsitans (Dyar) as epiornitic vectors and Aedes canadensis (Theobald) as an epizootic vector. Mosquito collection data from two endemic foci indicated substantial and significant differences in EEE virus infection rates. The occurrence of HJ virus, the differences in mosquito infection rates, and widespread epizootic disease during a year of low mosquito densities are used to develop a hypothesis on the distribution of multiple endemic foci of EEE virus in upstate New York.
TL;DR: A positive response to environmental sanitation and public education campaigns was indicated at Thursday Island and Townsville but not at Cairns, and garden accouterments such as saucers for pot plants and plant-striking containers provided the majority of habitats.
Abstract: In a survey of artificial water-bearing containers in northern Queensland, Australia, the eight wet-container categories generally did not differ significantly in proportions containing Aedes aegypti (L.) larvae. Water storage containers were a significant source of breeding on a tropical island (Thursday Island) and moderate at an inland rural town (Charters Towers); at two eastern seaboard cities (Townsville and Cairns), garden accouterments such as saucers for pot plants and plant-striking containers provided the majority of habitats. Rubbish (including automobile tires) and discarded household items were of less importance at all localities. A positive response to environmental sanitation and public education campaigns was indicated at Thursday Island and Townsville but not at Cairns.
TL;DR: The effectiveness of a recently developed DNA-probe method of identifying the morphologically identical mosquito species Anopheles gambiae Giles and A. arabiensis Patton was compared to that of an enzymatic typing method.
Abstract: The effectiveness of a recently developed DNA-probe method of identifying the morphologically identical mosquito species Anopheles gambiae Giles and A. arabiensis Patton was compared to that of an enzymatic typing method. Specimens reared from eggs laid by wild-caught females collected in Kenya were used. Either individual specimens were split and tested by both methods, or different individuals from isofemale egg batches were subjected to each of the two tests. Prior chromosomal analysis of material from these areas had shown that only A. gambiae and A. arabiensis were present in the samples. The DNA probe method gave results that were consistent with those obtained by enzymatic typing. No individuals or families, even those heterozygous for enzyme alleles typical of both mosquito species, showed DNA-probe hybridization patterns that suggested interspecies hybridization. This work demonstrates the validity of the DNA-probe method of distinguishing the species of field-collected specimens of A. gambiae and A. arabiensis in areas where these two species are sympatric.
TL;DR: Considering the likelihood that environmental changes associated with development will lead to increased population densities of at least some of these potential vectors, mosquito-borne diseases can be expected to play a significant role in human health after settlement and irrigation.
Abstract: The adult mosquito fauna of forest land due to be developed into irrigated agriculture under System C of the Mahaweli Development Project of Sri Lanka was surveyed in 1984 and 1985. Seventy-one species of mosquitoes were collected during the survey, 38 of which were taken at diurnal human bait; the most abundant were Aedes albopictus (Skuse), a vector of dengue in Southeast Asia, Ae. novalbopictus Barraud, and Ae. w-albus (Theobald). Nocturnal human-bait catches yielded 48 species, of which Mansonia annulifera (Theobald), was dominant. Other common species included Culex tritaeniorhynchus Giles, Cx. gelidus Theobald, Cx. fuscocephala Theobald, and Cx. pseudovishnui Colless, all potential vectors of Japanese encephalitis, and Anopheles culicifacies Giles, the established vector of human malaria in Sri Lanka. CDC light traps attracted 49 species, of which the most abundant were Mimomyia hybrida (Leicester) and Cx. pseudovishnui. Thirty-two species were collected from temporary huts in the forest; Ma. annulifera was dominant. Significant seasonal and site-related density differences were apparent in several species. There was evidence of the rapid invasion of areas disturbed by humans by two peridomestic species, Culex quinquefasciatus Say, the vector of bancroftian filariasis in Sri Lanka, and Armigeres subalbatus (Coquillett). Considering the likelihood that environmental changes associated with development will lead to increased population densities of at least some of these potential vectors, mosquito-borne diseases can be expected to play a significant role in human health after settlement and irrigation.
TL;DR: It is concluded that Ae.
Abstract: Studies were conducted to determine the ability of a West African strain of Aedes fowleri (Charmoy) to transmit Rift Valley fever (RVF) virus. Infection rates ranged from 11% (12/105) for mosquitoes that ingested 101.3-1.6 plaque-forming units (PFU) of virus to 89% (206/231) for those ingesting >106.4 PFU. Dissemination of virus to the hemocoel was time dependent. Virus was disseminated in only 34% (23/68) of the infected mosquitoes after 5–9 d incubation, compared with 76% (22/29) in those held 26 or more days after the infectious blood meal. Infection and dissemination rates were similar for mosquitoes exposed orally to either an Egyptian (ZH501) or a central African (ArB 1976) strain of RVF virus. Likewise, transmission rates (53%, 50/94) and viral titers (mean = 105.4 PFU) were similar for Ae. fowleri inoculated with either viral strain. Mosquitoes with a disseminated infection after oral exposure transmitted virus during 43% (13/30) of the refeedings. We conclude that Ae. fowleri should be considered as a potential vector of RVF virus.
TL;DR: Cattle, mongooses, and Carib grackles were the most abundant host species found in each of the three habitat types; dry pasture habitat supported the highest densities of ticks on these hosts.
Abstract: The hosts used and the importance of each host in the population dynamics of Amblyomma variegatum (F.) (the tropical bont tick) on Guadeloupe are presented. All potential hosts of the tick were sampled in three habitat types (defined by rainfall and topography) used for livestock production. Over 99% of all host-associated ticks were on cattle, goats, feral dogs, and mongooses. Other hosts of immature ticks were free-ranging domestic chickens, cattle egrets, Carib grackles, common ground doves, and grassquits. Adult ticks were collected only on cattle and goats, the most important hosts for all stages of A. variegatum . Cattle, mongooses, and Carib grackles were the most abundant host species found in each of the three habitat types; dry pasture habitat (lower rainfall and not seasonally flooded) supported the highest densities of ticks on these hosts. Potential methods of dissemination of A. variegatum to uninfested areas are discussed. Incidental collections of other tick species are given.
TL;DR: Test results suggest that an altered AChE with decreased sensitivity to inhibition is an important defense mechanism used by this Mexican strain of B. microplus to develop resistance to coumaphos, and perhaps other anticholinesterase insecticides.
Abstract: The acetylcholinesterases of three strains of larval Boophilus microplus (Canestrini) —one susceptible, the Escondido strain, and two resistant to coumaphos, the Tuxtla and Tuxpan strains, were studied. Initial studies showed that the total activity of acetylcholinesterase (AChE) of the susceptible strain was 4.5 and 7.6 times greater than that of the Tuxtla and Tuxpan strains, respectively. All three strains were more susceptible to chlorpyrifosoxon, the oxygen analog of chlorpyrifos, than to coroxon, the oxygen analog of coumaphos, in inhibition studies. The Tuxtla strain appeared to have at least two types of AChE, one susceptible to coroxon and the other resistant. Test results suggest that an altered AChE with decreased sensitivity to inhibition is an important defense mechanism used by this Mexican strain of B. microplus to develop resistance to coumaphos, and perhaps other anticholinesterase insecticides.
TL;DR: The relative tolerance of Anopheles larvae to suspensions of the bacterial toxin is a result of their low filtration rates, and in Cx.
Abstract: To study the impact of ingestion rate on the effectiveness of the stomach toxin produced by Bacillus thuringiensis var. israelensis , fourth-instar larvae of Aedes aegypti, Culex quinquefasciatus, Anopheles albimanus , and Anopheles quadrimaculatus were exposed to a series of toxin suspensions at larval densities ranging from 0.15 to 2.4 individuals per ml water. Toxin was dosed as weight per larva; consequently, toxin concentration increased with increasing larval density. Because filtration rates of individual larvae are not influenced by larval density, it was hypothesized that the toxin particles are ingested by larvae at a speed relative to particle concentration. With increasing larval density, increasing toxin concentrations were necessary to elicit equal levels of mortality. Based on regression analysis of the dosage-mortality correlation, toxin amounts inducing 50% mortality in groups at various densities were calculated. The average amount of toxin per larva inducing this level of mortality decreased by 62–63% ( An. quadrimaculatus ), 43–64% ( An. albimanus ), and 34–44% ( Ae. aegypti ) when larval density increased from 0.15 to 1.2 individuals per ml water. This effect was independent of toxin formulation and also was present when density was varied without surface crowding of larvae. Previously documented species-specific differences in susceptibility of test species were significant at low larval densities ( 1.2 individuals per ml water). We conclude that the relative tolerance of Anopheles larvae to suspensions of the bacterial toxin is a result of their low filtration rates. In Cx. quinquefasciatus , toxin effectiveness did not change with larval density, possibly due to feeding inhibition caused by the bacterial agent.
TL;DR: Bovine leukemia virus was transmitted mechanically to goats and sheep from a cow with persistent lymphocytosis and an infectious titer between 103 and 104 doses/ml by groups of 50 and 100 horse flies, Tabanus fuscicostatus Hine, but not bygroups of 25 and 10 flies.
Abstract: Bovine leukemia virus was transmitted mechanically to goats and sheep from a cow with persistent lymphocytosis and an infectious titer between 103 and 104 doses/ml by groups of 50 and 100 horse flies, Tabanus fuscicostatus Hine, but not by groups of 25 and 10 flies A total of 185 flies did not transmit BLV to goats from a cow with a normal lymphocyte count Transmission trials indicated at least 20% of the 10 nl blood residue on the mouthparts of T fuscicostatus may be deposited upon a second probe
TL;DR: The levels of enhanced metabolic detoxification in R ticks appeared insufficient to account for all of the reported substantial differences between S and R strains in susceptibility to coumaphos.
Abstract: A study was made of the comparative fate of [14C]coumaphos in larvae and adults of coumaphos-resistant (R) and -susceptible (S) strains of Boophilus microplus (Canestrini) that originated in Mexico. There were no differences between R and S strains in rates of cuticular penetration or internal accumulation of radioactive material after topical treatments (0.05 μg/tick) of unengorged adult females or after drench treatments (1 ppm) of larvae. Radioactive products of the metabolism of [14C]coumaphos in both larval and adult stages included the toxic oxygen analog (coroxon) and free and conjugated forms of chlorferon, the nontoxic substituted-coumarin ring moiety of the molecule. The rate of metabolic detoxification of absorbed coumaphos was more rapid in larvae than in adults of both strains. Concentrations of detoxification products were significantly lower, and of coumaphos and coroxon higher, in both larvae and adults from the susceptible strain. However, the levels of enhanced metabolic detoxification in R ticks appeared insufficient to account for all of the reported substantial (ca. 32–38 ×) differences between S and R strains in susceptibility to coumaphos.