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PubMed2005

Isolation of dipicolinic acid as an insecticidal toxin from Paecilomyces fumosoroseus.

Several entomopathogenic fungi produce toxins that could be used as bioinsecticides in integrated pest management programs. Paecilomyces fumosoroseus is currently used for the biological control of the whiteflies Bemisia tabaci and B. argentifolii. Supernatants from submerged batch culture, where the fungus produced abundant dispersed mycelium, conidia and blastospores, were toxic to the whitefly nymphs. The most abundant metabolite was purified by HPLC and identified by mass spectrometry and NMR as dipicolinic acid. Both the dipicolinic acid produced by the fungus and the chemically synthesized compound had insecticidal activity against third-instar nymphs of the insect. Dipicolinic acid was toxic to the whitefly nymphs in bioassays involving topical applications. In submerged culture, the specific growth rate of P. fumosoroseus was 0.054 h-1, the specific glucose consumption rate was 0.1195 g g-1 h-1 and the specific dipicolinic acid production rate was 0.00012 g g-1 h-1. Dipicolinic acid was detected after 24 h when the fungus started growing; and dipicolinic acid production was directly correlated with fungal growth. Nevertheless, the yield was low and the maximal concentration was only 0.041 g l-1. The maximal concentrations of conidia and blastospores (per milliliter) were 1.4x10(8) and 7x10(7), respectively.

Antibiosis↗
PubMed2006

Ticks (Ixodidae) from passerine birds in the Carpathian region.

Birds have been found to be a reservoir host of borrelia. In order to assess the situation in Slovakia ticks were collected from a total of 3057 mist-netted, ringed and released passerine birds in two locations at 500 m (in 2001) and 1000 m (in 2003) above sea level in the Bukovské Vrchy Hills, part of the Carpathian region in the north-east of Slovakia. A total of 75 birds of 16 species were infested with subadult ticks of Ixodes ricinus species (prevalence of parasitization 5%). Sixty-two larvae from 31 birds of 9 species and 80 nymphs from 52 birds of 15 species were found. The highest intensity of parasitization was observed on blackbirds Turdus merula, song thrushes T. philomelos and dunnocks Prunella modularis. Six Ixodes ricinus adult ticks were found on humans working with birds, and one I. ricinus female tick on their dog. In ticks, the presence of Rickettsia sp., Coxiella burnetii, Borrelia burgdorferi sensu lato and members of the Anaplasmataceae and Piroplasmidae, were investigated by polymerase chain reaction, followed by sequence analysis. Rickettsia sp. was found in 1 nymph from the European robin Erithacus rubecula, in 3 adult ticks (1 male, 2 females) from humans and in the tick from the dog. The closely related Ehrlichia- like species "Schotti variant" was detected in 1 nymph from the song thrush. Borrelia afzelii was identified in 1 male and B. garinii in 1 female tick collected on humans. Ixodes ricinus was found to be the vector of a wide spectrum of tick-borne pathogens in a mountainous area of the Carpathians. Because of the low yield of ticks and pathogens the importance of birds as reservoir hosts is still poorly understood.

Animals↗
PubMed2005

Potential of oil-based formulations of Beauveria bassiana to control Triatoma infestans.

The in vitro development of Beauveria bassiana conidia was monitored when immersed in six concentrations of seven non-ionic (MP 6400, MP 600, Renex 60, Renex 95, Span 80, Tween 20 and Tween 80) and three anionic (DOS 75, Hostapaval BVQ 9 and Surfax 220) surfactants and 11 vegetable oils (linseed, soybean, groundnut, rapeseed, thistle, sunflower, olive, sesame, corn, castor, and babassu). The influence of the oils on the settling behavior of Triatoma infestans nymphs and the activity of an oil-water formulation of the fungus against this vector under laboratory and simulated field conditions were also determined. With exception of DOS 75 and Surfax 220 germination of conidia on complete medium was >98% at 24 h after exposure to surfactants up to 10%. Elevated rates of germination (>25%) were observed in 10% corn, thistle and linseed oil 8 days after incubation. Pure oils had a significant repellent effect to T. infestans. Repellency decreased generally at 10% of the oil and some oils showed some attractiveness for nymphs when tested at 1%. Nymphs were highly susceptible to oil-water formulated conidia, even at unfavorable moisture for extra-tegumental development of the fungus on the insect cuticle.

Animals↗
PubMed1999

Fatty acid delta9-desaturation in the Triatoma infestans fat body: response to food and trehalose administrations.

The effects of food intake and carbohydrate administration on fatty acid delta9-desaturation were investigated in isolated microsomes from Triatoma infestans fat body. Fifth instar nymphs, which were solely blood-fed just after the molt and then fasted, were used as controls and for determination of optimal assay conditions. Both [1-14C]palmitic and [1-14C]stearic acids in a medium containing ATP, CoA, MgCl2, NADH, NaF, and O2 were tested. For the control group, optimal conditions were a pH of 6.8-7.2, an incubation temperature of 29 degrees C, and an incubation time of 10 min. delta9-Desaturation depended on the presence of reduced pyridine dinucleotides; NADH and NADPH were equally efficient. Stearic acid showed a higher apparent Vmax than palmitic acid, but the apparent Km were very similar. When fifth instar nymphs were blood-fed weekly, a marked increase of delta9-desaturation was observed for both acids. Higher desaturation activity was also induced by injection of the carbohydrate trehalose into the hemolymph of fasted nymphs. These results indicate that insect delta9-desaturation, like the mammalian counterpart, is sensitive to dietary changes and carbohydrate administration.

Animals↗
PubMed1984

Detection of only JH III in several life-stages of Nauphoeta cinerea and Thermobia domestica.

We have conducted a reinvestigation into both the identification and quantification of juvenile hormone (JH) from several developmental stages of the cockroach, Nauphoeta cinerea, and the firebrat, Thermobia domestica, using a gas chromatography-mass spectrometric (GC/MS) method. We detected only JH III in these animals in contrast to prior studies in which JH I, II, and/or III had been reported using a different scheme relying on HPLC purification and subsequent GC/MS analysis under chemical ionization (CI) conditions. Very high levels (approximately 800 ng/g) of JH III were found in N. cinerea embryos at stages after dorsal closure whereas first stadium nymphs and female penultimate stadium nymphs contained only low levels (approximately 1 ng/g and approximately 7 ng/ml respectively); in adult females at the stage of rapid oocyte growth approximately 150 ng JH III per ml of hemolymph was measured. T. domestica nymphs and egg laying adults contained only low levels (approximately 1 ng/g) of JH III. The results emphasize the caution which must be used in interpreting results of procedures for analysis of JH at parts-per-billion levels, and also enforce prior observations that the higher JH homologs are not present except in the Lepidoptera.

Animals↗
PubMed1996

Enhanced immunity to Hyalomma anatolicum anatolicum ticks in cross-bred (Bos indicus x Bos taurus) calves using ascaris extract immunomodulator with the tick salivary gland extract antigens.

Development of acquired immunity in cross-bred (Bos indicus x Bos taurus) calves against Hyalomma anatolicum anatolicum, a tick vector of bovine tropical theileriosis was studied using ascaris extract (AE), an immunomodulator of IgE responses, along with the tick salivary gland extract (SGE) antigens in Freund's incomplete adjuvant (FIA) emulsion. Calves immunised with SGE + FIA showed significant rejection (47.4 +/- 2.8%) of larvae, whereas only marginal rejection (12.47 +/- 1.5%) of nymphs was observed. In contrast, calves immunised with the immunomodulator AE in addition to SGE + FIA showed significant enhanced rejection of nymphs (50.25 +/- 5.2%), while the rejection of larvae was only slightly higher (55.8 +/- 11.4%), and not statistically different. In addition, incorporation of the immunomodulator AE also resulted in significant enhancement in the percentage recovery of abnormally fed larvae and nymphs. This abnormal feeding was characterised by their white to pale-yellow colour instead of the dark-grey colour of normally fed ticks. It may possibly be attributed to their inability to gain access to the blood vessels owing to the host immunological reaction at the bite sites. Consequently, the ticks fed on extravascular fluid devoid of red blood cells resulting in their white to pale-yellow colour. Difference in the disease transmission potential of normally and abnormally fed ticks is of future interest. Sera from all the immunised calves after 2 weeks of immunisation were positive for anti-tick SGE antibodies in the dot enzyme immunoassay (DOT-EIA). The immunised calves were positive for immediate type hypersensitivity (ITH) skin reaction on intradermal inoculation of the tick SGE antigens. There was no apparent difference in the DOT-EIA antibody titres between the two immunised groups. However, ITH skin swelling was significantly higher in AE + SGE + FIA immunised calves. The study indicates that use of the AE as an immunomodulator along with the tick SGE antigens enhanced anti-tick immunity.

Adjuvants, Immunologic↗
PubMed1991

Hexagenia rigida (ephemeroptera) as a biological model in aquatic ecotoxicology: experimental studies on mercury transfers from sediment.

The accumulation of two mercury compounds--HgCl(2) and CH(3)HgCl--by Hexagenia rigida (burrowing mayfly nymphs) from contaminated sediments was investigated experimentally. Three exposure periods were selected: 7, 14 and 28 days. Results reveal a high capacity of this species for Hg accumulation and considerable differences between the two chemical forms of the metal. Thus, the amount of total mercury accumulated after 28 days' exposure would be 60 times greater for the organic form if the two compounds were initially added to the sediment in the same concentrations. No significant growth inhibition appears for the different experimental conditions studied. Data treatment at the organism level showed a positive linear correlation between the fresh weight and Hg content in the nymphs; this was especially marked when the exposure time was relatively long and Hg was in the form of CH(3)HgCl. The study of mercury distribution in the organs of Hexagenia rigida (gills and gut) and the examination of results obtained in similar experimental conditions after contamination of the nymphs via the water column showed the importance of the trophic route, via ingested sediment, for the bioaccumulation of the metal initially introduced into the sediment.

Journal Article↗
PubMed1987

Activity of the insect growth regulator fenoxycarb (RO-13-5223) on Triatoma infestans (Hemiptera).

1. Fenoxycarb (RO-13-5223) exhibits a strong juvenile hormone type of activity against Triatoma infestans. 2. Topical treatment of last-stadium nymph with the juvenoid caused the formation of superlarvae, adult-larvae intermediates and adultoids. The ED50 was 0.02 microgram/insect. 3. Taking into account abnormalities in oceli, head, thorax, legs, wings, abdomen, conexivo and external genitalia, a scoring system to evaluate the retention of juvenile characters after moulting was developed. 4. Intermediate dose of the juvenoid produced the prolongation of the last instar nymph. 5. Abnormal individuals formed composite cuticles possessing both nymph and adult morphological features.

Animals↗
PubMed2006

Prevalence of Borrelia burgdorferi s.l. OspA types in Ixodes ricinus ticks from selected localities in Slovakia and Poland.

In this study, 746 questing Ixodes (I.) ricinus ticks from eastern Slovakia and 187 ticks from southern Poland were investigated for infection with Borrelia (B.) burgdorferi sensu lato and different outer surface protein A (OspA) types by an improved restriction fragment length polymorphism (RFLP) analysis of the ospA gene. The method enables differentiation of both single and multiple infections with B. burgdorferi s.s. (OspA type 1), B. afzelii (OspA type 2), B. garinii (OspA types 3-8), B. valaisiana (subgroups I and II), B. lusitaniae, B. bissettii, and the recently described genospecies A14S. Broad heterogeneity in B. burgdorferi s.l. was found including all species and subtypes except for B. lusitaniae, B. bissettii, and genospecies A14S. Regional prevalence of B. burgdorferi s.l. varied between 8% and 22.5%. The most frequent species were B. garinii (45.4%) and, notably, B. burgdorferi s.s. (31.3%). I. ricinus nymphs harbored almost exclusively B. burgdorferi s.s. and B. garinii OspA type 4, while in adults a broad variety of B. burgdorferi s.l. types was found. Mixed infections were significantly more often in nymphs than in adult ticks. In all mixed infected nymphs, B. burgdorferi s.s. with OspA type 4 was present. These data strongly suggest that B. burgdorferi s.s. and B. garinii OspA type 4 are maintained in these areas by specific transmission cycles involving a so far undetermined vertebrate host which is frequently fed on by I. ricinus larvae. This improved method provides a reliable tool for epidemiological studies on the heterogeneity of B. burgdorferi species and OspA types, an important prerequisite for improved local risk assessment and for test- and vaccine development for Europe.

Animals↗
PubMedDate not supplied

The proximate cue of density-dependent soldier production in a social aphid.

Tuberaphis styraci is a social aphid that produces 2nd instar soldiers with morphological, behavioral and reproductive division. High aphid density was shown to induce soldier production in T. styraci, although direct cue of soldier induction associated with high density has been unknown. In order to identify the proximate environmental cue underlying the density-dependent soldier production, a series of experiments was conducted using an artificial diet rearing technique. When adult aphids were reared with live normal nymphs, live soldiers, dead normal nymphs, shed skins, honeydew globules and excreted wax, only live normal nymphs effectively induced soldier production. In order to gain insights into the nature of soldier-inducing cue associated with normal aphids, we performed artificial diet experiments using partitioned and non-partitioned chambers, in which direct contact between aphids was either inhibited or allowed. Induction of soldiers was observed only when direct contact was allowed. Therefore, it was shown that the soldier-inducing cue is neither volatile in the air nor diffusible through the diet, but is transmitted between normal non-soldier aphids via direct contact. On the basis of these results, we suggest that the soldier-inducing cue might be physical stimulus combined with non-volatile surface chemicals whose properties differ between normal aphids and soldiers.

Animal Feed↗
PubMed2004

Sitobion avenae alatae infected by Pandora neoaphidis: their flight ability, post-flight colonization, and mycosis transmission to progeny colonies.

Epizootics caused by the obligate Entomophthorales pathogen Pandora neoaphidis may result from more than one possible means of fungal dissemination among host aphids, but we hypothesize that wide dispersal of the fungus is most likely to be associated with the flight behavior of migratory alates. We tested this hypothesis in a simulation experiment by assessing the flight capability of Sitobion avenae alates infected with P. neoaphidis and the potential of their post-flight survival, colonization, and mycosis transmission to progeny. A total of 281 alates were inoculated with P. neoaphidis, individually flown for up to 5h and 9km in a computer-monitored flight mill system and then reared for 10 days on wheat seedlings. The infected alates were capable of surviving on average for 2.9 days (range 1-7 days) and leaving 4.6 nymphs prior to deaths. Transmission of fungal infection within progeny colonies occurred after the mother alates died from P. neoaphidis mycosis. The level of contagious infection among the nymphs reached up to 16.8% within 7 days but varied with the survival time of the infected mother alates after flight. Based on stepwise polynomial regression analysis, progeny colony size was highly correlated with the interactions of flight time with both post-flight survival time and the number of nymphs left per alate before death (r2 = 0.997). Progeny mortality on day 5 after colonization was inversely correlated with post-flight survival time (r2 = 0.949) whereas infection on day 7 was correlated with flight distance and an interaction of post-flight survival time with fecundity of the infected alates (r2 = 0.970). Progeny mortality observed on day 10 was merely correlated to mortality observed on day 5 (r2 = 0.946). These results indicate a successful transmission of alate-borne P. neoaphidis to progeny colonies and further support our hypothesis on the means of primary dispersal of aphid epizootics by migratory alates in a geographically wide range.

Animals↗
PubMed2006

Fat body of Prorhinotermes simplex (Isoptera: Rhinotermitidae): ultrastructure, inter-caste differences and lipid composition.

Ultrastructure of the fat body was studied in following castes and developmental stages of Prorhinotermes simplex: larvae of the first and the second instar, pseudergates, presoldiers, soldiers, nymphs, imagoes and mature ergatoid neotenic reproductives of both sexes. Fat body always consists of two principal cell types: adipocytes and urocytes. Adipocytes are characterized by a presence of large amounts of storage substances, namely lipid droplets, glycogen rosettes and proteins in the form of either biocrystals or vacuoles. Proportion of these components strongly varies during ontogeny. Adipocytes are equipped by a large central vacuole in which lipid droplets may resolve. Cytoplasm of urocytes contain glycogen rosettes and spherical or irregular concretions, other organelles are rare. Only adipocytes change their inner structure in the course of ontogeny: amount of glycogen decreases during the postembryonic development, it is the major kind of inclusion in the larvae but lacks in nymphs and imagoes; opposite trend is performed by lipids. The changes in protein content are less obvious but are explained and discussed. The total amount of triacylglycerols (TAGs) was found to be roughly 100microg in a pseudergate, 250microg in a nymph, and 30microg in a soldier. The most abundant fatty acids in TAGs are oleic (O), stearic (S), palmitic (P) and linoleic (L) acid. TAGs form a complex mixture with OOO, OPO, OLO and OOS being the most abundant isomers. Only negligible differences exist among the castes.

Adipocytes↗
PubMed1999

Feeding frequency and nutritional status of peridomestic populations of Triatoma infestans from Argentina.

We studied the nutritional characteristics of peridomestic populations of Triatoma infestans from 25 habitats in an endemic area of Chagas disease in Argentina. The aim was to determine the feeding frequency, fresh weight of adults and older nymphs, and the gonotrophic status of females, in order to compare them with previous studies of domestic populations in the same region. The average infection rate of the bugs and blood meal origins were also determined in order to calculate the maximum risk for Trypanosoma cruzi transmission in these habitats. The number of bugs in each habitat correlated positively with the number of hosts. The estimated number of bites per night was strongly correlated with the total number of bugs collected from that habitat. The shortest biting interval (1.9 and 1.7 days) occurred in November and February, where 52-60% of insects suck blood each night. Adults and nymphs recently fed showed significantly higher fresh weight in November. There was no apparent correlation between the mean weights of adults or nymphs and the number of insects found within each habitat. Bloodmeal analysis showed that most of the bugs (87%) had fed from chicken, with human and dog scarcely represented and no bloodmeals identified from cat. However, human bloodmeals were only identified from chicken coops near the house (< 12 m). Almost all females (92-100%) captured during the spring months had been mated, whereas the proportion of mated females decreased significantly during summer (60-71%). The maximum risk (MR) average from these peridomestic habitats was 0.35 bites from infective bugs/night, tenfold lower than MR from domestic habitats. The good nutritional status of recently fed bugs, found in these chicken coops during all the hot season, suggest that active dispersal is unlikely to occur from peridomestic habitats.

Animals↗
PubMed2000

Directional sensitivity of an identified wind-sensitive interneuron during the postembryonic development of the locust.

Simultaneous extracellular recordings from both locust abdominal connectives show a differential activation of both bilateral homologues of an identified long projection interneuron (A4I1) in response to wind stimuli from different directions. Despite the previously shown extensive structural dynamics of sensory afferents and synaptic rearrangement of the direct afferent-to-interneuron connections during postembryonic development, a directional sensitivity is already present in first instar nymphs. Only quantitative changes in the strength of the directional response can be detected. Intracellular stainings of the A4I1 interneuron in first instar nymphs and adults show that general morphological features do not change during postembryonic development, in contrast to the presynaptic sensory afferents. This also holds for general morphological features of pleuroaxillary flight motoneurons. The output connections of A4I1 to these motoneurons and an unidentified intersegmental interneuron are already present in flightless nymphs.

Journal Article↗
PubMed2002

Ultrastructural changes to the midgut of the black field cricket (Teleogryllus commodus) following ingestion of potato protease inhibitor II.

Ultrastructural changes to the midgut epithelium of nymphs of the black field cricket (Teleogryllus commodus) after ingestion of potato protease inhibitor II (PPI-II) (0.6% (w/v) in artificial diet) were determined by light and electron microscopy. Crickets fed diet containing PPI-II grew more slowly than those fed control diet and changes observed to the PPI-II-fed nymphs included reduction of midgut wall depth, vacuolisation of the epithelial cells, swelling of the microvilli, cellular protrusions into the midgut and eventual rupture of individual or small groups of epithelial cells. These changes were first seen 2 days after PPI-II ingestion. Complete disintegration of the midgut to the basement membrane was not seen during the 27-day observation period and repair and regeneration of pockets of epithelial cells was observed. Immunocytochemistry revealed that PPI-II was localised within the ectoperitrophic matrix space of the gut. The location of the peritrophic matrix was determined by labelling with wheat germ agglutinin (WGA), but no rupture of this structure was observed in PPI-II-fed nymphs.

Journal Article↗
PubMed1998

Effects of sensory stimuli on the behavioural phase state of the desert locust, Schistocerca gregaria.

The nature of stimuli, emanating from other locusts, which are effective in inducing gregarization in the desert locust was investigated. Isolated-reared fifth-instar nymphs were subjected to tactile, visual and olfactory stimuli, presented singly and in combination, and the effect on the behavioural phase state was quantified using logistic regression analysis. Tactile stimulation provided by rolling paper spheres proved to be highly gregarizing, whether presented alone or in combination with the other stimuli. Olfactory and visual stimuli together caused partial behavioural gregarization. Visual stimulation alone was weakly gregarizing after prolonged exposure, while olfactory stimuli alone were ineffective. Nymphs and pre-reproductive and reproductive adults of both sexes were also treated with synthetic adult male `aggregation' pheromone blend (Torto et al., 1994, Journal of Chemical Ecology 20, 1749). No effect of this blend was found on the behavioural phase state, even when visual stimuli were present. Non-locust related stimuli, including wheat odour and flashing lights, were also tested on nymphs. Neither induced any change in the behavioural phase state, indicating that increased sensory flow is not a sufficient explanation for locust-induced behavioural phase change.

Journal Article↗
PubMed2000

Population dynamics of the free-living stages of Amblyomma cajennense (Fabricius, 1787) (Acari: ixodidae) on pastures of Pedro Leopoldo, Minas Gerais State, Brazil.

A study on the population behavior of Amblyomma cajennense larvae, nymphs and adult free-living stages was carried out in Pedro Leopoldo County, Minas Gerais State, Brazil, from July 1995 to July 1997. Larvae were collected from pasture from April to October using the technique of drag sampling with flannelette. The maximal larval population was observed during autumn (May) representing, respectively, 48 and 82% of the total numbers recovered during the first and the second years of the experiment. Nymphs and adults were captured throughout the year by the use of traps with carbon dioxide as chemical attractant. The highest population of nymphs occurred during the winter (July), representing 39.5% of the total collected specimens. Adults had the highest population density on pasture during spring and summer, i.e., from August to May, with peaks in January and February, representing 46 and 38.3% of the total collected specimens during the first and the second year of study, respectively.

Animals↗
PubMed2001

Survival away from sheep and alternative methods of transmission of sheep lice (Bovicola ovis).

Transmission of sheep lice is thought to occur mainly by sheep to sheep contact although the possibility of other sources of infestation is often suggested. This study investigated the period of survival of Bovicola ovis after removal from sheep under varying conditions and assessed the likelihood of new infestations arising from contaminated facilities, wool caught on fences and shearers' footwear. In laboratory studies with lice held away from sheep at 4, 20, 25 and 36.5 degrees C, adults and nymphs survived longest at 25 degrees C (LT90 of 11.7 and 24.1 days for adults and large nymphs, respectively). Nymphs survived longer than adults and lice provided with raw wool survived longer than lice provided with wool that had been degreased. Nymphal lice survived for up to 29 days on unscoured wool at 36.5 degrees C, but the LT50 was less than 9 days in most experiments. In shearing sheds in winter and early spring lice survived for up to 14 and 16 days, respectively. These periods of survival are considerably longer than previously indicated for B. ovis. Most lice dropped out of wool staples attached to a fence within 1 h and only two of a total of 225 lice were still present after 24 h, suggesting that sheep are unlikely to become infested from wool caught on fences. Adult and nymphal lice readily transferred to shearers' moccasins and survived there for up to 10 days, indicating that transmission of lice on the footwear of shearers or other sheep handlers may be a cause of new infestations. Microwaving each moccasin for 5 min killed all lice and may provide a simple method of reducing the likelihood of transmission of B. ovis between properties.

Animal Husbandry↗