Showing papers in "Journal of Medical Entomology in 1994"
TL;DR: Ricinus is medically the most important arthropod in northern Europe and has been recorded from 29 mammal species, 56 bird species, and two species of lizards in Sweden alone.
Abstract: This review covers the geographic distribution and host relationships of the tick species in Sweden. Ixodes uriae White, I. caledonicus Nuttall, I. unicavatus Neumann, I. arboricola Schulze & Schlottke, and I. lividus Koch are ornithophagous species. I. trianguliceps Birula, I. canisuga Johnston, I. hexagonus Leach, and Argas vespertilionis (Latreille) are mammalophagous. I. ricinus (L.) and Haemaphysalis punctata Canestrini & Fanzago feed on both birds and mammals. All these tick species may be considered to be permanently present in Sweden. I. persulcatus Schulze, Hyalomma marginatum Koch, and the brown dog tick, Rhipicephalus sanguineus (Latreille), may be regarded as not indigenous to Sweden although they may be regularly introduced by spring-migrating birds or imported dogs, respectively. The first European record of the American dog tick, Dermacentor variabilis (Say), is reported. There are several records of Hyalomma aegyptium (L.) from imported tortoises in Sweden. Excluding other ticks imported on exotic pets and zoo animals, another 13 tick species are listed that may occur, at least occasionally, in Sweden. Because of its wide geographic distribution, great abundance, and wide host range, I. ricinus is medically the most important arthropod in northern Europe. I. ricinus is common in southern and south-central Sweden and along the coast of northern Sweden and has been recorded from 29 mammal species, 56 bird species, and two species of lizards in Sweden alone. The potential introduction to Sweden of exotic pathogens with infected ticks (e.g., I. persulcatus and H. marginatum on birds or Dermacentor spp. and R. sanguineus on mammals) is evident.
196 citations
TL;DR: Studies were done on effect of temperature changes on survival of Culex tarsalis Coquillett, the primary vector of western equine encephalomyelitis (WEE) and St. Louis encephalitis (SLE) viruses, in two regions where temperatures differed by 5 degrees C.
Abstract: If global warming occurs in California, daily mean temperatures may increase by 3 to 5 degrees C, precipitation patterns will change, and sea level may rise 1 m. Studies were done on effect of temperature changes on survival of Culex tarsalis Coquillett, the primary vector of western equine encephalomyelitis (WEE) and St. Louis encephalitis (SLE) viruses, in two regions where temperatures differed by 5 degrees C. Daily mortality of adult vectors increased by 1% for each 1 degree C increase in temperature. At 25 degrees C, only 5% of Cx. tarsalis survived for 8 or more days, the time required for extrinsic incubation of these viruses. Extrinsic incubation times for these viruses shortened when temperatures were increased from 18 to 25 degrees C. WEE virus infection was modulated and transmission decreased at 32 degrees C. If temperatures in the warmer region increase by 5 degrees C, WEE virus may disappear and SLE virus would persist. In the cooler region, a 5 degrees C increase would decrease vector survivorship and virus activity in midsummer. In North America, epidemics of WEE have prevailed above a 21 degrees C isotherm and those of SLE below this isotherm. With global warming, epidemics of these viruses could extend into currently unreceptive northern areas. WEE virus would disappear from more southern regions. Geographic distribution of vector, human, and animal populations could be altered. North America could become more receptive to invasion by tropical vectors and diseases.
195 citations
TL;DR: It is found that infectivity of a rodent species is related to the number of infesting, potentially infective nymphal I. ricinus larvae infected, and control of Lyme disease by reduction of abundance of reservoir hosts will be difficult to achieve.
Abstract: Factors regulating prevalence of Borrelia burgdorferi s.l. Johnson, Schmid, Hyde, Steigerwalt & Brenner in Ixodes ricinus (L.) were examined during 1991–1992 at Bogesund, near Stockholm in south-central Sweden. Nine species of small and mediumsized mammals ( Sorex araneus L., S. minutus L., Neomys fodiens Pennant, Clethrionomys glareolus [Schreber], Microtus agrestis [L.], Apodemus sylvaticus [L.], A. flavicollis [Melchior], Lepus europaeus Pallas, L. timidus L.) were found to infect feeding tick larvae with B. burgdorferi s.l., whereas two species of large mammals ( Capreolus capreolus L., Alces alces L.) failed to infect feeding tick larvae with this spirochete. The most important mammalian reservoirs at the study locality were S. araneus and rodents, accounting for 91% of all I. ricinus larvae infected. In view of the great number of potentially effective reservoirs for B. burgdorferi s.l. in Sweden, control of Lyme disease by reduction of abundance of reservoir hosts will be difficult to achieve. We also found that infectivity of a rodent species is related to the number of infesting, potentially infective nymphal I. ricinus . Insectivores and rodents were the most important hosts of larval I. ricinus , whereas most nymphal ticks fed on hares and cervids. Adult I. ricinus were frequently found on all species of hares and cervids examined but never on insectivores and rodents. No single species seemed to be of paramount importance as a source of blood for female ticks. Therefore, control of Lyme disease by reduction of abundance of mammal hosts available for female tick engorgement will probably require massive reductions of numbers of both C. capreolus and L. timidus .
134 citations
TL;DR: Eggs of five strains of Aedes albopictus were obtained in both diapause and nondiapause conditions and exposed to various cold acclimation regimes in the laboratory, after which they were subjected to diverse chilling treatments.
Abstract: Eggs of five strains of Aedes albopictus (Skuse) were obtained in both diapause and nondiapause conditions and exposed to various cold acclimation regimes in the laboratory, after which they were subjected to diverse chilling treatments. Larvae that survived chilling as eggs survived to the pupal stage. Eggs of Aedes aegypti (L.) and Aedes triseriatus (Say) were included as control species. Eggs of temperate Ae. albopictus were more cold-hardy than eggs of Ae. aegypti but less cold-hardy than the eggs of Ae. triseriatus . Cold acclimation and diapause enhanced cold hardiness of only temperate Ae. albopictus . Cold acclimation had a greater influence on cold hardiness than did diapause. Both the temperature and the duration of cold acclimation modulated cold hardiness. Cold hardiness induced in the laboratory was similar to cold hardiness induced in the field in northern Indiana. The cold hardiness of Ae. albopictus from central Florida was intermediate in comparison with temperate and tropical strains. Tropical Brazilian Ae. albopictus and tropical Asian Ae. albopictus were similar in cold hardiness.
133 citations
TL;DR: There was a distinct difference between the mortality curves for larvae at 93% RH and 100% RH, which suggests that larvae were taking in water from the air at the higher RH whereas those at an RH < or = 93% were not.
Abstract: Survival of unfed larvae and nymphs of Ixodes scapularis Say (formerly named I. dammini Spielman, Clifford, Piesman & Corwin) was tested at 27 degrees C for relative humidities ranging from 65 to 100%, which were maintained by various saturated salts or water. The times until half the larvae died (LT50) at 100, 93, 85, 75, and 65% RH were 67.1, 26.6, 8.3, 1.3, and 1.1 d, respectively. Maximal larval survival in the laboratory was 129, 59, 24, 3, and 2 d at the same relative humidities. There was a distinct difference between the mortality curves for larvae at 93% RH and 100% RH, which suggests that larvae were taking in water from the air at the higher RH whereas those at an RH < or = 93% were not. There was little difference between the 100 and 93% RH survival curves for the nymphs. All of the nymphs at 100% RH survived at least 149 d. At 93 and 100% RH, one nymph survived at each RH for 210 and 205 d, respectively. The LT50s for the nymphs of I. scapularis were 169.9 (100% RH), 168.5 (93%), 118.8 (85%), 10.7 (75%), and 3.6 (65%) d. Maximal nymphal survival in the laboratory was 162, 65, and 8 d at 85, 75, and 65% RH, respectively. The inability of the larvae to retain water effectively is probably more important than the ability to imbibe water from subsaturated air in the survival of this stage. Subadult I. scapularis require a relatively humid habitat for survival, although some individuals have the potential to seek a host for many weeks within a mesic environment.
130 citations
TL;DR: A 1% neem oil-kerosene mixture may provide economical personal protection from mosquito bites and reduced biting of human volunteers and catches of mosquitoes resting on walls in the rooms.
Abstract: The repellent action of neem oil (extracted from the seeds of Azadirachta indica A. Juss) was evaluated on mosquitoes at two villages near Delhi, India. Kerosene lamps containing neem oil were burned in the living rooms, and mosquitoes resting walls or attracted to human bait were collected inside rooms from 1800 to 0600 h. Neem oil (0.01-1%) mixed in kerosene reduced biting of human volunteers and catches of mosquitoes resting on walls in the rooms. Protection was more pronounced against Anopheles than against Culex. A 1% neem oil-kerosene mixture may provide economical personal protection from mosquito bites.
125 citations
TL;DR: In this article, it was shown that the salivary glands of a tick can be infected by a virus that is imbibed with the blood meal, and the virus can survive molting by establishing an infection in at least one cell type that does not undergo histolysis.
Abstract: Arboviruses differ from other viruses in their need to replicate in both vertebrate and invertebrate hosts. The invertebrate is a blood-sucking arthropod that is competent to transmit the virus between susceptible animals. Arboviruses transmitted by ticks must adapt to the peculiar physiological and behavioral characteristics of ticks, particularly with regard to blood feeding, bloodmeal digestion, and molting. Virus imbibed with the blood meal first infects cells of the midgut wall. During this phase the virus must contend with the heterophagic bloodmeal digestion of ticks (an intracellular process occurring within midgut cells) and overcome the as yet undefined "gut barrier" to infection. Genetic and molecular data for a number of tick-borne viruses indicate ways in which such viruses may have adapted to infecting ticks, but far more information is needed. After infection of midgut cells, tick-borne viruses pass to the salivary glands for transmission during the next blood-feeding episode. To do this, the virus must survive molting by establishing an infection in at least one cell type that does not undergo histolysis. Different tick-borne viruses have different strategies for surviving the molting period, targeting a variety of tick tissues. The infection can then persist for the life span of the tick with little evidence of any detrimental effects on the tick. Transmission to a vertebrate host during feeding most probably occurs via saliva that contains virus secreted from infected salivary gland cells. The virus then enters the skin site of feeding, which has been profoundly modified by the pharmacological effects of tick saliva. At least three tick-borne viruses exploit such tick-induced host changes. This phenomenon (saliva-activated transmission) is believed to underlie "nonviremic transmission," whereby a virus is transmitted from an infected to an uninfected cofeeding tick through a host that has an undetectable or very low viremia. Thus tick-borne viruses that have adapted to the feeding characteristics of their tick vectors may not need to induce a virulent infection (with high viremia) in their natural vertebrate hosts. Efficient transmission of tick-borne viruses between cofeeding ticks may be a means of amplifying virus infection prevalence in F1 generations infected by transovarial transmission.
118 citations
TL;DR: Two aedine and three anopheline species were allowed to blood-feed to repletion, and their host-seeking behavior was measured with an olfactometer at intervals afterward, showing continued host- seeking by some anophelines during the gonotrophic cycle.
Abstract: Two aedine and three anopheline species were allowed to blood-feed to repletion, and their host-seeking behavior was measured with an olfactometer at intervals afterward. Both Aedes aegypti (L.) and Ae. albopictus (Skuse) were inhibited from subsequently seeking a host during the gonotrophic cycle, but Anopheles gambiae Giles, An. albimanus Wiedemann, and An. freeborni Aitken, all showed varying degrees of host-seeking behavior while their eggs matured. Continued host-seeking by some anophelines during the gonotrophic cycle has important implications for some assumptions commonly made about mosquito behavior and parasite transmission.
106 citations
TL;DR: In insight into how antibiotics, hormones, and metabolites may affect the development of P. falciparum in An.
Abstract: Anopheles gambiae Giles sensu lato (s.l.) and An. stephensi Liston were exposed as adults to para-aminobenzoic acid (PABA), human insulin, or gentamicin sulfate, an antimicrobial solution, to determine their effects on Plasmodium falciparum Welch development to the oocyst stage. For both mosquito species, concentrations of PABA from 0.001 to 0.05% had no effect on either oocyst infection rates or oocyst densities. At higher concentrations, PABA-fed mosquitoes had decreased oocyst infection rates when they were exposed after, but not before, experimental infections. Insulin-fed mosquitoes had significantly higher oocyst infection rates than controls and increased oocyst densities in both An. gambiae s.l and An. stephensi . The most dramatic impact on parasite development was observed for mosquitoes fed on gentamicin. For An. gambiae s.l. fed 0.05% gentamicin, oocyst infection rates were 3.7-fold higher than in controls, whereas oocyst densities were 5.7 times greater than in controls. Anopheles stephensi fed on diets of 0.1% gentamicin had 2.4-fold higher infection rates and increased oocyst densities. Concentrations of gentamicin above 0.1% had deleterious effects on mosquito survival and their ability to digest blood meals. These findings provide insight into how antibiotics, hormones, and metabolites may affect the development of P. falciparum in An. gambiae s.l. and An. stephensi .
104 citations
TL;DR: The reservoir competence of the lesser mealworm, Alphitobius diaperinus (Panzer) is reported for Salmonella typhimurium (Loeffler) relative to broiler chicken production, providing evidence that transstadial transmission of S. typhIMurium may occur.
Abstract: The reservoir competence of the lesser mealworm, Alphitobius diaperinus (Panzer) is reported for Salmonella typhimurium (Loeffler) relative to broiler chicken production. Salmonella typhimurium was isolated from feces of the adult lesser mealworm at least 28 d after feeding for 24 h on 1 g of chicken feed inoculated with 3 x 10(8) bacteria/ml. All larvae fed S. typhimurium ceased voiding the bacteria in their feces before pupal molt, except one. One beetle continued to void S. typhimurium after it emerged as an adult, providing evidence that transstadial transmission of S. typhimurium may occur. The bacteria were found both on the external body surface and inside the body of surface-sterilized adults and larvae during 16 d of exposure. Salmonella-positive cloacal swabs were obtained from 1-day-old broiler chicks within 24 h after eating one infected lesser mealworm adult or larva.
101 citations
TL;DR: A three-parameter density dependent growth equation is used to examine the critical parameter values that determine whether or not a mobile element will spread and become fixed in a finite diploid vector population and suggests that engineered transposons with a wide range of properties may be used to drive genes into wild vector populations.
Abstract: With a view to the possible use of transposable elements (TEs) as a mechanism to drive genes into insect vector populations, we used a three-parameter density dependent growth equation to examine the critical parameter values that determine whether or not a mobile element will spread and become fixed in a finite diploid vector population. Populations were simulated with parameter values affecting size, reproductive rate, density-dependence, and transposition efficiency of the mobile element. Simulations indicated that an equilibrium was reached quickly, typically in 0.75 that reduces fertility < 25% will become fixed when introduced at a frequency as low as 1% of the total population. These results are consistent with previously reported population genetics models. They suggest that engineered transposons with a wide range of properties may be used to drive genes, such as those for parasite resistance, into wild vector populations.
TL;DR: Mesocyclops longisetus (Thiébaud) should be of practical value for community-based Ae.
Abstract: Mesocyclops longisetus (Thiebaud), Mesocyclops thermocyclopoides Harada, Mesocyclops venezolanus Dussart, and Macrocyclops albidus (J urine) were tested for their effectiveness in controlling Aedes aegypti (L.) larvae in a variety of containers around homes in EI Progreso, Honduras. All four cyclopoid species killed >20 larvae per cyclopoid per d under container conditions. M. longisetus was most effective, not only because it was the most voracious predator, but also because it survived best in the containers. M. longisetus maintained long-term populations in 200-liter drums, tires, vases, and cement tanks (without drains), providing the cyclopoids were not dried or poured out. M. longisetus reduced third- and fourth-instar Ae. aegypti larvae by >980/0 compared with control containers without cyclopoids. M. longisetus should be of practical value for community-based Ae. aegypti control if appropriate attention is directed to maintaining it in containers after introduction.
TL;DR: Large Ae.
Abstract: The relationship of larval nutrition and adult body size to the susceptibility of Aedes aegypti (L.) to Ross River virus infection was examined. Large adult mosquitoes produced by feeding larvae a high-level diet consumed significantly more virus particles than did smaller mosquitoes. However, when a correction for body size was made, smaller mosquitoes were found to consume significantly more virus per unit of body weight. A host viremia of 2.4 log10 PFU/ml failed to infect mosquitoes of any size. Large Ae. aegypti mosquitoes were significantly more susceptible than small mosquitoes when fed on hosts with viremias of 4.8, 5.7, 6.4, and 7.5 log10 PFU/ml, but differences in susceptibility were less apparent at higher viremias.
TL;DR: It is provided evidence that a cryptic cycle develops weeks before epiornitic cycling is detected in C. melanura, indicating that the early season cycle is initiated by the recrudescence of latent virus in previously infected birds.
Abstract: Eastern equine encephalomyelitis virus (EEEV) is perpetuated in eastern North America in a mosquito-wild bird maintenance cycle that involves Culiseta melanura (Coquillett) as the principal enzootic vector and passerine birds as the primary amplifying hosts. We examined the role of birds in the EEEV cycle at a site in southern New Jersey where EEEV cycles annually at high levels. Birds and mosquitoes were sampled during three epiornitics and one season of limited virus activity. We examined antibody prevalence in birds in relation to eight physical and natural history characteristics. Our goal was to compare EEEV cycling in C. melanura and the primary avian hosts better to understand the mechanisms that initiate annual epiornitics. Antibody prevalence was highest in the Blue Jay (62%), Wood Thrush (60%), and Tufted Titmouse (44%). Resident status of birds was the natural history characteristic most closely linked to participation in the EEEV cycle. Species spending the greatest amount of time at our study site (permanent residents, summer residents) had the highest antibody rates. We captured viremic birds as early as 25 May, 51 d before we first detected virus in C. melanura. We recaptured 10 after hatching year adults and one hatching year (HY) bird that seroconverted before we detected virus in C. melanura. We also found EEEV antibody in 15 HY birds up to 31 d before we isolated EEEV from C. melanura. We provide evidence that a cryptic cycle develops weeks before epiornitic cycling is detected in C. melanura by traditional laboratory techniques, indicating that the early season cycle is initiated by the recrudescence of latent virus in previously infected birds.
TL;DR: Based on winter flagging experiments on Long Island, NY, adult Ixodes scapularis Say have an apparent threshold of questing activity at 4 degrees C, which should be incorporated into public education efforts.
Abstract: Based on winter flagging experiments on Long Island, NY, adult Ixodes scapularis Say have an apparent threshold of questing activity at 4°C. This threshold should be incorporated into public education efforts because the public may be at risk of contracting Lyme disease any time during the winter when temperatures exceed 4°C.
TL;DR: Studies using serologic and polymerase chain reaction-(PCR) facilitated analysis of field samples from southern Texas indicate the presence of Rickettsia typhi and ELB agent infected cat fleas, Ctenocephalides felis, and the first observation of ELB infected vertebrates (opossums).
Abstract: Studies using serologic and polymerase chain reaction-(PCR) facilitated analysis of field samples from southern Texas indicate the presence of Rickettsia typhi and ELB agent infected cat fleas, Ctenocephalides felis (Bouche), and the first observation of ELB infected vertebrates (opossums). The ELB agent is a recently described typhus-like rickettsia that is not distinguished from R. typhi or R. prowazekii by currently available serologic reagents. Restriction digests of PCR products from 399 fleas revealed an ELB agent infection rate of 3.8% and a R. typhi infection rate of 0.8%. Three of nine tested opossums (Didelphis virginiana) were shown to harbor ELB agent infections. No R. typhi infected rats, Rattus norvegicus, or rat-fleas, Xenopsylla cheopis Rothschild, were detected among surveyed samples. The persistence of this murine typhus disease focus appears to be better accounted for by the presence of infected cat fleas, opossums, and other non-rat hosts found in close association with human populations. Involvement of the ELB agent in the biology of murine typhus is suggested by its prevalence among suspected vectors and reservoir hosts.
TL;DR: Whole-plant Soxhlet extractions for the three Tagetes species showed that T. minuta had the greatest biocidal effect on the larvae and adults of Aedes aegypti (L.) and Anopheles stephensi Liston.
Abstract: Whole-plant Soxhlet extractions for the three Tagetes species showed that T. minuta had the greatest biocidal effect on the larvae and adults of Aedes aegypti (L.) and Anopheles stephensi Liston. Bioassays of simultaneous steam distillation extractions of the various parts of T. minuta found extracts from the flowers provided LD90s of 4 and 8 ppm against the larvae and 0.4 and 0.45% against the adults of A. aegypti and A. stephensi , respectively. Further research on T. minuta floral extracts as new biorational insecticides tire discussed.
TL;DR: Results indicate that Ae.
Abstract: Daily survivorship and fecundity of Aedes aegypti mosquitoes were monitored for cohorts provided with five nutritional treatments: water, 2% sucrose, blood from a live chicken plus water, blood plus 2% sucrose, and blood alone. The median mortality time (LT50) for these females was 6, 54, 16, 12, and 29 d, respectively. There was no significant difference in the number of eggs laid by females in any of the treatments containing a host. Females maintained on blood alone laid as many or more eggs during their lifetime as females with access to sugar who had a greater life expectancy. Males maintained on sugar alone survived significantly longer than those in any of the other treatments. Large- and small-bodied, sugar-starved Ae. aegypti females that were marked, released, and recaptured in a Thai village survived as well as the replicate cohorts that received sugar or sugar plus blood during the 36 +/- 12 h period from emergence until their release. These results indicate that Ae. aegypti females live longer in the laboratory if they are provided a source of carbohydrate, but the increased survival associated with sugar feeding does not increase reproductive success.
TL;DR: During October-November 1990, 31,497 mosquitoes consisting of 25 different species were collected in Barkedji, Ferlo area (Senegal), and tested for virus infection, resulting in the first isolations of arboviruses from A. africana and Mimomyia species.
Abstract: During October–November 1990, 31,497 mosquitoes consisting of 25 different species were collected in Barkedji, Ferlo area (Senegal), and tested for virus infection. Viruses were isolated from 55 of 407 pools. Eighteen pools were found positive for both Bagaza virus (BGA) and West Nile virus (WN). One alphavirus (Babanki [BBK] and 72 flaviviruses (19 BGA, 53 WN) were isolated from Culex poicilipes Theobald (29 WN, 8 BGA), C. neavei Theobald (3 WN, 1 BGA), Mimomyia hispida Theobald (8 WN, 6 BGA, and 1 BBK), M. lacustris Edwards (4 WN, 1 BGA), M. splendens Theobald (6 WN, 2 BGA), Mimomyia . spp. (2 WN), and Aedeomyia africana Neveu-Lemaire (1 WN). These were the first isolations of arboviruses from A. africana and Mimomyia species. C. poicilipes and possibly Mimomyia spp. may be involved in an avian-mosquito cycle of West Nile virus transmission in Senegal.
TL;DR: Ch Chrysomya rufifacies appeared later in the decomposition process and over a wider period of days in goat than in rabbit carcasses, suggesting the dependence of presence or absence of a carrion arthropod taxon at a given point in succession on interactions between other arthropods or carcass type must be considered when using successional data to estimate postmortem intervals.
Abstract: Red imported fire ants, Solenopsis invicta Buren, caused an increased in the proportion of gaps in the daily occurrence of postfeeding larvae of Cochliomyia macellaria (F.) in carrion-baited traps. Chrysomya rufifacies appeared later in the decomposition process and over a wider period of days in goat than in rabbit carcasses. The dependence of presence or absence of a carrion arthropod taxon at a given point in succession on interactions between other arthropods or carcass type must be considered when using successional data to estimate postmortem intervals.
TL;DR: The vector competence of the western black-legged tick, Ixodes pacificus Cooley & Kohls, and the Pacific Coast tick, Dermacentor occidentalis Marx, for the Lyme disease spirochete, Borrelia burgdorferi, was compared.
Abstract: The vector competence of the western black-legged tick, Ixodes pacificus Cooley & Kohls, and the Pacific Coast tick, Dermacentor occidentalis Marx, for the Lyme disease spirochete (Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner) was compared. Rabbits, hamsters, and the deer mouse, Peromyscus maniculatus (Wagner), were injected with cultured spirochetes or infected tick-suspensions, or were fed upon by spirochete-infected ticks. Five of seven isolates used as inocula were reisolated from vertebrates with the ear-punch biopsy technique. Three isolates (CA4, 5, 7) that were infectious for both vertebrates and ticks possessed prominent low-molecular-weight protein bands that had relative mobilities of approximately 24-26 kd. The ability of ticks to acquire and maintain various inocula of B. burgdorferi was evaluated by feeding uninfected larvae xenodiagnostically on all three hosts 0-63 d postinjection. Low percentages (0-10.6%) of the I. pacificus and none of the D. occidentalis became infected. By contrast, 33% of I. pacificus and 40% of Ixodes scapularis Say (= I. dammini Spielman, Clifford, Piesman & Corwin) that fed on hamsters infected by tick-bite acquired and transstadially passed spirochetes; 10% of D. occidentalis fed on infected hamsters similarly acquired but did not maintain spirochetes. Ixodes pacificus nymphs efficiently transmitted B. burgdorferi to deer mice and a hamster. Feeding by one spirochete-infected nymph was sufficient to produce patent infections in each of five mice.
TL;DR: Biting rhythm as well as vertical and horizontal distribution of host-seeking Anopheles arabiensis Patton was studied at a remote warm-water spring in the Kruger National Park, South Africa, which usually is devoid of human presence.
Abstract: Biting rhythm as well as vertical and horizontal distribution of host-seeking Anopheles arabiensis Patton was studied at a remote warm-water spring in the Kruger National Park, South Africa, which usually is devoid of human presence. An. arabiensis seeking hosts were collected throughout the night with several peaks, often with greatest biting activity during the predawn period. Abundance did not decline linearly as a function of distance from the breeding area, but was related to vegetation patterns. Most bites occurred on the ankles or feet and decreased rapidly above that height. Wearing closed shoes or raising feet off the ground could reduce vector contact and therefore the risk of malaria infection.
TL;DR: The results corroborate earlier conclusions that North American strains of Ae.
Abstract: Aedes albopictus (Skuse) lays eggs refractory to hatching in response to several environmental cues. The goal of this statistical treatment was to quantify the role and interaction of latitude and country of origin (Japan and the United States), photoperiod, rearing/holding temperature, and a newly identified element, elevation of the site of origin, with critical photoperiod (Cpp). We also describe the development of an equation relating the incidence of diapause to daylength, rearing/holding temperature, and latitude and elevation of the site of origin, an equation useful in the development of a simulation model of the population dynamics and distribution of Ae. albopictus in North America. The analysis indicated that elevation from 0 to 300 m is significantly correlated with Cpp. The results also corroborate earlier conclusions that, on the basis of a shallower geographical cline in photoperiodic response in the United States, North American strains of Ae. albopictus have a temperate origin in Asia and indicate that the rapid spread of this mosquito within the United States via the distribution of used tires resulted in founder populations that were only partially adapted in diapause response to local conditions.
TL;DR: Four aspects of olfaction in host location by tsetse flies, Glossina spp.
Abstract: Four aspects of olfaction in host location by tsetse flies, Glossina spp., are discussed as follows: (1) host location and its mechanism, (2) factors affecting host location, (3) kairomones and host location, and (4) kairomones and host selection. Flight behavior in the various phases of host location (i.e., ranging, activation, orientation, and landing) in the absence and presence of olfactory cues is summarized. Movement toward an odor source is effected inter alia through optomotor-steered, upwind anemotaxis. It is still unclear how tsetse employ upwind anemotaxis to realize host location, considering the often highly variable wind direction. Olfactorily induced activation is governed by the olfactory cue perceived and threshold levels set by the internal state of the fly. The former depends on the odor source and distance from it; the latter is determined by species, sex, and physiological state. Wind direction and speed, as well as vegetation and the mobility of the host, interfere with successful completion of odor-induced host location. Close-range olfactory cues (including composition and concentration gradients), visual cues, and nutritional state determine whether a fly, having reached the host animal, will land on it. Carbon dioxide is important in host location because it induces landing and long-range attraction. The role of the other kairomones (acetone, 1-octen-3-ol, 4-methyl-phenol, and 3-n-propyl-phenol) is less clear. Apart from the complacency of various host species under tsetse attack, host choice by tsetse is predominantly opportunistic and primarily the result of the frequency of successful tsetse-host encounters. Nevertheless, host selection based on olfactory cues cannot be ruled out.
TL;DR: It is concluded that the presence of salivary tachykinins or catechol/oxidase is not unique to A. aegypti or A. albimanus.
Abstract: Salivary vasodilators of Aedes aegypti (L.) and Anopheles albimanus (Wiedemann) were characterized previously as a tachykinin peptide and a catechol oxidase/peroxidase activity, respectively. To verify whether these two different vasodilators also were found in other distantly related members of each mosquito genus, we characterized the vasodilators from A. triseriatus and A. gambiae. A. triseriatus salivary gland homogenates produced a reversible, endothelium dependent vasorelaxation of rabbit aortic rings constricted with norepinephrine, and contracted an isolated guinea pig ileum preparation. Additionally, the homogenate had no activity on both smooth muscle preparations when both tissues were desensitized previously by a large dose of substance P. Taken together, these assays suggest the presence of a salivary tachykinin in A. triseriatus. A. gambiae salivary gland homogenates induced a slow vasodilation on both endothelium intact and endotheliumless preparations of aortic rings. A. gambiae homogenates also displayed catechol oxidase and peroxidase activity against o-dianisidine but not against serotonin, indicating the presence of an enzyme system slightly different from A. albimanus. We conclude that the presence of salivary tachykinins or catechol/oxidase is not unique to A. aegypti or A. albimanus.
TL;DR: In Senegal, Dengue-2 virus appears to be maintained in an enzootic cycle and, therefore, plays an expanding role in human disease and increases the need for effective surveillance in mosquito populations.
Abstract: During 1990, Dengue-2 (DEN-2) virus was isolated for the first time from mosquitoes (Aedes furcifer, six isolates; Ae. taylori, six isolates; Ae. luteocephalus, seven isolates) collected during an epidemic in which DEN-2 virus also was isolated from humans. Numerous isolations have been made previously from mosquitoes in the absence of human infection. In Senegal, DEN-2 virus appears to be maintained in an enzootic cycle and, therefore, plays an expanding role in human disease and increases the need for effective surveillance in mosquito populations.
TL;DR: The ability of AMP-FLP analyses to provide individual human locus characterizations from desiccated arthropod excreta obtained from adult crab lice, Pthirus pubis, fed on human volunteers is reported.
Abstract: The ability to identify individual hosts of hematophagous arthropods via bloodmeal analyses is a continuing pursuit in both medical and forensic entomology. Characterization of human DNA from blood-feeding arthropods has been advanced substantially by preparation techniques, such as the polymerase chain reaction (PCR). Successful application of amplified fragment length polymorphism (AMP-FLP) analysis to excreta obtained from adult crab lice, Pthirus pubis (L.), fed on human volunteers is reported herein. Human DNA derived from crab louse excreta was typed successfully for two human DNA genetic markers, D1S80 and HUMTH01. Although preliminary, these results illustrate the ability of AMP-FLP analyses to provide individual human locus characterizations from desiccated arthropod excrement.
TL;DR: Three morphologically different pupal phenotypes were selected from a parent strain of Anopheles albimanus Wiedemann collected from the Suchiate region in the state of Chiapas, Mexico and significant differences in susceptibility to coindigenous Plasmodium vivax Grassi & Feletti were observed.
Abstract: Three morphologically different pupal phenotypes (green, striped, brown) were selected from a parent strain of Anopheles albimanus Wiedemann collected from the Suchiate region in the state of Chiapas, Mexico. Significant differences in susceptibility to coindigenous Plasmodium vivax Grassi & Feletti were observed when striped was compared with the parent colony as well as with brown and with green phenotypes. Differences in susceptibility were not significant between the other phenotypes and the parent colony.
TL;DR: Results suggest that populations of I. scapularis can occur and reproduce in the absence of white-tailed deer, so that eradication of all deer would greatly reduce, but not eliminate, all risk of Lyme disease.
Abstract: Nymphal Ixodes scapularis Say deer ticks were collected at 22 parks or other natural areas on Long Island, New York, to examine the relationship between tick populations and geographic position, size of area, presence of white-tailed deer, Odocoileus virginianus (Zimmerman), and numbers of human Lyme disease cases in adjacent communities. Nymphal ticks were 93% less abundant when deer were absent and were also less common in smaller natural areas. Geographic position on Long Island was not important. Tick numbers were significantly correlated with human Lyme disease incidence in adjacent townships. A second survey of larval ticks from five areas where deer were absent and six where deer were present found larvae present at four of the five sites without deer, but at only 2% of the levels found where deer were present. These results suggest that populations of I. scapularis can occur and reproduce in the absence of white-tailed deer, so that eradication of all deer would greatly reduce, but not eliminate, all risk of Lyme disease.
TL;DR: It is proposed that host blood excretion evolved in response to larval nutritional requirements, and fleas fed in vivo on cats and mosquitoes, Aedes aegypti (L.)--contained significantly less protein and more digested protein than the blood that they had fed upon.
Abstract: Protein content and ion composition of host blood and feces from blood-fed adult cat fleas, Ctenocephalides felis (Bouche), were examined. Total fecal protein differed slightly from host blood indicating that there was little digestion of host blood by adult fleas. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels of host blood and flea feces also revealed little digestion, as evidenced by the quantitatively and qualitatively similar protein banding patterns. Blood and fecal ion compositions also were similar, except for fleas fed in vivo on cats, where both potassium and chloride compositions of feces were approximately 50% lower. Host blood or flea feces alone were not of sufficient food value to allow > 12.5% of larvae to develop to adults. The addition of yeast or dog chow increased larval development to the pupal stage to 100% and 87.5% of first instars tested, respectively. Although some larval survival occurred with diets of dog chow + yeast (37.5%), feces + hair (20%), and feces + stratum corneum (16.7%), the period to cocoon formation was twice as long as that of larvae fed diets containing blood or flea feces + yeast. In contrast to fleas, feces of adults of two other hematophagous insects--bed bugs, Cimex lectularius L., and mosquitoes, Aedes aegypti (L.)--contained significantly less protein and more digested protein than the blood that they had fed upon. We propose that host blood excretion evolved in response to larval nutritional requirements.