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PubMed1990

An ivermectin sustained release bolus in cattle: its effects on the tick Ixodes ricinus.

Five calves were given an intraruminal bolus orally, designed to release ivermectin for 120 days at the rate of 8 mg/day. This is equivalent to a dose of 40 micrograms/kg/day for a calf expected to weigh 200 kg at the end of the delivery period. Five control calves were given a placebo bolus. On days 7 and 36 after treatment ten nymphs and ten adult female Ixodes ricinus (Linnaeus 1758) were placed in ear bags on the calves. The engorgement rates were monitored for 10 days and subsequent egg production and hatching percentages determined. There were no significant differences between treatment groups for female mortality. However, ivermectin treatment significantly reduced the numbers and weights of engorged females, females laying eggs, and the number of larvae produced on the treated calves was reduced to 3% of that of the control group. The effects on nymphs, although similar, were less consistent than on adults.

Administration, Oral↗
PubMed1991

Reproductive and developmental biology of the oriental cockroach Blatta orientalis (Dictyoptera).

At 27 degrees C and 45% r.h. in the laboratory, the oriental cockroach Blatta orientalis (L.) developed to adulthood in seven to nine instars for males (66% had eight instars) and eight to ten instars for females (67% had nine instars) in mixed groups, with up to twelve instars for isolated females. Nymphal development lasted 185 +/- 2 days for males, 216 +/- 4 days for females, with 89% survival to adulthood. Adult longevity was significantly more for males than females in mixed groups. Virgin females lived for 135 +/- 6 days compared with 87 +/- 9 days for females kept with males. After an initial maturation time of 12.2-13.5 +/- 0.4 days for mated and unmated females, oothecae were produced, on average, every 6-7 (range 2-29) days. Ootheca viability was 68% from females kept with males, 32% from females kept apart from males. Numbers of nymphs emerging were 14.1 +/- 0.26 after 45 days from mated female oothecae 8.2 +/- 0.3 after 49 days from unmated females. With sexual reproduction the sex ratio of progeny reaching adulthood was 1.1 males per female (n = 443), whereas unmated females produced only female progency, which is consistent with parthenogenetic reproduction. Drawings of the ventral aspect of the terminalia are given to show features useful for instar determination and for distinguishing between male and female nymphs and adults of B. orientalis.

Animals↗
PubMed1992

Effects of hydroprene on development and reproduction in the Oriental cockroach, Blatta orientalis.

Nymphs of the Oriental cockroach Blatta orientalis were exposed during the penultimate and final instars to vinyl tiles treated with the juvenile hormone analogue hydroprene. Adults moulting from these nymphs exhibited deformities such as twisted wings in both sexes and modified genitalia in females. Females with deformities were unable to produce viable oothecae. B.orientalis confined on tiles treated with hydroprene at rates of 25-100 mg/m2 did not reproduce. The treatment rate of 10 mg/m2 reduced fecundity and caused 47-57% of resultant adults to have deformities, but some adults reproduced successfully and population growth was not suppressed.

Animals↗
PubMed1995

Analysis of stage-specific and shared antigens derived from Rhipicephalus sanguineus by electrophoresis and western blotting.

We carried out an SDS-PAGE analysis of antigens of Rhipicephalus sanguineus using extracts of eggs (EE), larvae (LE), nymphs (NE), male salivary glands (MSGE), male midguts (MME), female salivary glands (FSGE) and female midguts (FME). Under non-reducing conditions a common band of about 205 kDa was observed. EE, LE and NE extracts showed groups of bands between 150 and 75 kDa. A protein pattern was observed in FSGE extract with a group of bands between 75 and 50 kDa and four bands between 15 and 6.5 kDa. In this case an apparently exclusive band of molecular weight about 25 kDa was observed. Under reducing conditions similarities between LE and NE extracts increased, separating from the EE pattern. On the other hand, we have determined the presence of stage-specific and common antigens on EE, LE, NE, MSGE, MME, FSGE and FME extracts of R.sanguineus by means of immunoblots using polyclonal sera of rabbits infested with larvae, nymphs or adults of this tick. EE extract was only recognized by the anti-larva sera. Higher reactivity was observed when the extracts were tested with anti-adult sera. In these experiments a very prominent band of molecular weight about 45 kDa was detected. This band was not observed under reducing conditions. Higher reactivity with anti-adult sera was observed against FSGE extract.

Animals↗
PubMed1996

The occurrence of ixodid ticks on wild mink Mustela vision in England and Wales.

Four species of ticks found to infest 1391 American mink (Mustela vison) in Britain in five years were, in declining order of frequency, Ixodes hexagonus, Ixodes canisuga, Ixodes ricinus and Ixodes acuminatus. Ixodes hexagonus and I. canisuga occurred on 40% and 2.5% of mink respectively. Infestation rates (the proportion of infested mink) of adult females, nymphs and larvae were similar and tended to be lower in summer. The distribution of infestation size (the number of ticks per host) for adult females describes a negative binomial. The mean infestation size of nymphs varied with the sex of the host was 5.2 for males and 4.2 for females. Mink are competent hosts for I.hexagonus.

Animals↗
PubMed2006

The Lyme disease agent Borrelia burgdorferi requires BB0690, a Dps homologue, to persist within ticks.

Borrelia burgdorferi survives in an enzootic cycle, and Dps proteins protect DNA against damage during starvation or oxidative stress. The role of a Dps homologue encoded by Borrelia in spirochaete survival was assessed. Dps-deficient spirochaetes were infectious in mice via needle-inoculation at the dose of 10(5) spirochaetes. Larval ticks successfully acquired Dps-deficient spirochaetes via a blood meal on mice. However, after extended periods within unfed nymphs, the Dps-deficient spirochaetes failed to be transmitted to a new host when nymphs fed. Our data suggest that Dps functions to protect the spirochaetes during dormancy in unfed ticks, and in its absence, the spirochaetes become susceptible during tick feeding. dps is differentially expressed in vivo- low in mice and high in ticks - but constitutively expressed in vitro, showing little change during growth or in response to oxidative stress. Borrelia Dps forms a dodecameric complex capable of sequestering iron. The Dps-deficient spirochaetes showed no defect in starvation and oxidative stress assays, perhaps due to the lack of iron in spirochaetes grown in vitro. Dps is critical for spirochaete persistence within ticks, and strategies to interfere with Dps could potentially reduce Borrelia populations in nature and thereby influence the incidence of Lyme disease.

Amino Acid Sequence↗
PubMed2005

The occurrence of nymphal stage of Linguatula serrata in water buffaloes (Bubalus bubalis): nymphal morphometry and lymph node pathology.

The mesenteric lymph nodes (MLN) of buffaloes (n = 100) were examined for the presence of parasitic infection. The nymphal stage of Linguatula serrata was observed in two buffaloes. A single white-coloured nymph with transversely striated spines on a segmented body, two pairs of oral suckers and hooks was observed in the MLN. The morphometrics of the nymphs were studied. The affected lymph nodes were grossly enlarged with cyst and showed pathological lesions of fibroblastic reaction with a mild underlying inflammatory zone.

Animals↗
PubMed2002

Buffalo-associated Theileria parva: the risk to cattle of buffalo translocation into the Highveld of Zimbabwe.

There has been an increase in the introduction of game animals, including African buffaloes, into the Highveld of Zimbabwe to establish private game reserves on condition that they are confined in separate and secured paddocks. Owing to shortages of pastures cattle were grazed in buffalo-grazed paddocks resulting in outbreaks of buffalo-derived theileriosis. This paper reports the results of epidemiological observations carried out on two game reserves to assess the risk of buffalo translocation. The infection rate with Theileria parasites in ticks collected from buffalo-grazed pastures was high and produced fatal theileriosis in susceptible cattle. Similarly, adult R. appendiculatus ticks artificially fed as nymphs on the buffaloes produced fatal infections in susceptible cattle. Theileria parva (Boleni), the vaccine used to immunize cattle against theileriosis, and a buffalo-derived T. parva stabilate (BV-1) were inoculated in naïve buffaloes to study the Theileria carrier-state in these animals. The two buffaloes that had received the Boleni stabilate showed no clinical theileriosis reaction; however, the ticks derived from them produced a subclinical reaction in one susceptible calf. The buffalo which had received stabilate BV-1 developed fever, high schizont parasitosis for 10 days and 15% piroplasms parasitemia. R. appendiculatus ticks fed as nymphs on this buffalo produced fatal theileriosis reaction in a susceptible calf.

Animals↗
PubMed1999

Lethal effect of Rickettsia rickettsii on its tick vector (Dermacentor andersoni).

Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever, was lethal for the majority of experimentally and transovarially infected Rocky Mountain wood ticks (Dermacentor andersoni). Overall, 94.1% of nymphs infected as larvae by feeding on rickettsemic guinea pigs died during the molt into adults and 88. 3% of adult female ticks infected as nymphs died prior to feeding. In contrast, only 2.8% of uninfected larvae failed to develop into adults over two generations. Infected female ticks incubated at 4 degreesC had a lower mortality (80.9%) than did those held at 21 degreesC (96.8%). Rickettsiae were vertically transmitted to 39.0% of offspring, and significantly fewer larvae developed from infected ticks. The lethal effect of R. rickettsii may explain the low prevalence of infected ticks in nature and affect its enzootic maintenance.

Animals↗
PubMed2000

Prevalence of Lyme disease Borrelia spp. in ticks from migratory birds on the Japanese mainland.

Borrelia sp. prevalence in ticks on migratory birds was surveyed in central Japan. In autumn, a total of 1,733 birds representing 40 species were examined for ticks. A total of 361 ticks were obtained from 173 birds of 15 species, and these ticks were immature Haemaphysalis flava (94.4%), Haemaphysalis longicornis, Ixodes columnae, Ixodes persulcatus, Ixodes turdus, and an unidentified Ixodes species. Of these, 27 juveniles of H. flava on Turdus pallidus, Turdus cardis, or Emberiza spodocephala, 2 juveniles of I. persulcatus on T. pallidus, and 1 female H. flava molted from a T. pallidus-derived nymph were positive for the presence of Borrelia by Barbour-Stoenner-Kelly culture passages. In spring, a total of 16 ticks obtained from 102 birds of 21 species were negative for the spirochete. Isolates from 15 ticks were characterized by 5S-23S rRNA intergenic spacer restriction fragment length polymorphism analysis; all isolates were identified as Borrelia garinii with pattern B/B' based on the previous patterning. According to the intergenic spacer sequences, 2 of 15 isolates, strains Fi14f and Fi24f, were highly similar to B. garinii strains 935T of Korea and ChY13p of Inner Mongolia, China, respectively. These findings indicate that Lyme disease-causing B. garinii may have been introduced to Japan by migratory birds from northeastern China via Korea. Additionally, a case of transstadial transmission of B. garinii from nymph to adult H. flava suggests that the infected H. flava may transmit Borrelia to large animals.

Animals↗
PubMed1991

Rickettsiae and Borrelia burgdorferi in ixodid ticks.

Nymphs and adults of hard-bodied ticks were collected in Connecticut and tested by direct and indirect immunofluorescence staining methods for rickettsiae and Borrelia burgdorferi. Of the 609 Ixodes dammini ticks examined, 59 (9.7%) harbored rickettsialike microorganisms in hemocytes (blood cells). These bacteria reacted with fluorescein-conjugated antiserum to Ehrlichia canis, the etiologic agent of with fluorescein-conjugated antiserum to Ehrlichia canis, the etiologic agent of canine ehrlichiosis. Prevalence of infection ranged from 6.8 to 12.7% for males and females, respectively. Although the specific identities of the hemocytic rickettsialike organisms are unknown, they share antigens with ehrlichiae. Electron microscopy revealed rickettsiae in ovarian tissues of I. dammini that also had infected hemocytes. Rickettsialike organisms were also observed in the hemocytes of 5 (6.9%) of 73 Dermacentor variabilis ticks. In analyses for B. burgdorferi, 146 (23.7%) of 617 I. dammini ticks harbored these spirochetes in midguts. Hemocytic rickettsialike microorganisms coexisted with B. burgdorferi in 36 (6.7%) of the 537 nymphs and adults of I. dammini examined. I. dammini, with its broad host range, has the potential to acquire multiple microorganisms.

Animals↗
PubMed1985

Spotted fever group rickettsiae in immature and adult ticks (Acari: Ixodidae) from a focus of Rocky Mountain spotted fever in Connecticut.

Immature and adult ixodid ticks were collected during 1983 and 1984 in Newtown, Connecticut, an area endemic for Rocky Mountain spotted fever (RMSF), to determine prevalence of infection by spotted fever group (SFG) rickettsiae. Direct fluorescent-antibody (FA) staining revealed SFG organisms in 6 (1.8%) of 332 Dermacentor variabilis larvae, 5 (7.8%) of 64 D. variabilis nymphs, and in 2 (40%) of 5 Ixodes cookei nymphs removed from small- and medium-sized mammals. Hemolymph tests detected rickettsia-like organisms in 15 (8.8%) of 170 D. variabilis adults; 8 specimens retested by direct FA were negative. In contrast, hemocytes from 5 (8.6%) of 58 Ixodes texanus females contained organisms that stained positively in both hemolymph and direct FA tests. An indirect microimmunofluorescence test identified specific antibodies to Rickettsia rickettsii, the etiologic agent of RMSF, in serum samples from a chipmunk, raccoons, and white-footed mice. Results indicate that immature or adult ticks of at least three species may be involved in the maintenance and transmission of SFG rickettsiae at Newtown.

Animals↗
PubMedDate not supplied

Lethal effect of a bait for Rhodnius prolixus (Hemiptera: Reduviidae), the vector of Chagas' disease, containing hexachlorocyclohexane (HCH), under laboratory conditions.

The lethal effect of a bait containing an aqueous hexachlorocyclohexane (HCH) suspension at the concentration of 1g/l and maintained at room temperature was studied in the laboratory over a period of 12 weeks. The suspension was placed in a latex bag hanging inside a 1000-ml beaker tightly covered with nylon netting, and left there with no changes for 85 days. Sixteen groups of R. prolixus bugs, consisting on average of 30 specimens each, were successively exposed to the bait and observed at different intervals for one week each. The mortality rate was 100% for all groups, except for the 16th, whose mortality rate was 96.7%. As the groups succeeded one another, mortality started to occur more rapidly and was more marked at the 6- and 24-h intervals. Later tests respectively started at 6:00 a.m. and 6:00 p.m. showed that diurnal and nocturnal periodicity in the offer of food had no effect on mortality. First- and 2nd- instar nymphs and adults male were more sensitive and 5th- instar nymphs were more resistant to the active principle of the bait.

Animals↗
PubMed2002

Dynamics of evolution and resistance to starvation of Triatoma vitticeps (Stal 1859) (Reduviidae: Triatominae), submitted to two different regimens of food deprivation.

The resistance to starvation of Triatoma vitticeps has been analyzed comparatively, according to different regimens of food deprivation under laboratory conditions. One cohort, composed of 100 specimens of each evolutionary nymphal stage, was submitted to continuous fasting until death; the second group, arranged in the same way, was fed once on chicken. Through this work, it was possible not only to compare the results obtained from the first group with other authors' results but, also, to analyze the dynamics of evolution, molting, longevity and the increase in insect longevity, in the second group. The average values recorded for survival time revealed statistical differences between the two groups. Among the important results detected, there is one that deserves to be emphasized: the incredible increase in longevity among insects that received only one feed - an average increase in survival time that reached 2.95 to 3.30 times in nymphs of 3rd and 4th stages, respectively. One 5th stage nymph survived for up to 350 days and the females may triplicate their survival rate, what represents an important epidemiological factor. The knowledge about this type of biological characteristic of T. vitticeps may contribute to prevent the domiciliation of this species, what seems to be incipient in some municipal districts, in Brazil.

Animals↗
PubMed2004

[Efficacy of Fipronil in the control of the peridomiciliary cycle of Triatoma infestans in an area resistant to Deltamethrin].

This study tested the efficacy of liquid Fipronil (1.0%) against Triatoma infestans, administered by pouring on birds and mammals both in laboratory and field conditions. In the laboratory a chicken, dog, and goat were treated with Fipronil, after which deltamethrin-resistant stage III T. infestans nymphs were fed on them. The control group used same-stage nymphs reared in laboratory. During the field phase, Fipronil was used to treat 4 dogs, 1 cat, and 2 broody hens. Intradomiciliary infestation was treated using aerothermics. In laboratory, nymphal mortality was 100.0% after 7 days and 88.8% after 30 days. In the field, there was a 65.4% decrease in the triatomine density rate after 30 days.

Animals↗
PubMed2004

Photoperiod influence on the biology and phenological characteristics of Dichelops melacanthus (Dallas, 1851) (Heteroptera: Pentatomidae).

The influence of the photoperiod on the biology and seasonal morphs of Dichelops melacanthus (Dallas, 1851) was studied in the laboratory. Four different photoperiods (11, 12, 13, and 14 hL = hours of light) were tested, keeping the temperature at 25 +/- 1 masculine C and the relative humidity at 65 +/- 5%. Nymph developmental time tended to be longer under shorter photophases (11 and 12 hL). The 14-hour photophase (long day) resulted in lower nymph mortality rates. Females maintained at 13 and 14 hL showed greater weight gain (1st-28th day) than females under 12 hL. D. melacanthus showed reproductive oligopause induced by short photophases, especially when exposed to 11 hL. Under 13 and 14 hL, 85% and 65% of females oviposited, respectively, in comparison to 10% and 15% of females ovipositing under 11 and 12 hL, respectively. Fecundity (number of egg masses and number of eggs/female) was greater in the longer than under the shorter photophases. Seasonal dimorphism induced by photoperiod was observed in D. melacanthus adults. Under short-day conditions (11 and 12 hL), adults showed short and rounded shoulder spines, grayish brown abdomen (mainly in 11 hL), high lipid contents, and lower percentage of mature reproductive organs. Under long-day conditions (13 and 14 hL), the stink bugs showed greatly developed shoulder spines, green abdomen, low lipid contents, and mature reproductive organs.

Animals↗
PubMed2002

Action threshold for applying insect growth regulators to tomato for management of irregular ripening caused by Bemisia argentifolii (Homoptera: Aleyrodidae).

The whitefly Bemisia argentifolii Bellows & Perring is a major pest of tomatoes, causing an irregular ripening disorder characterized externally by incomplete or inhibited reddening of fruit, especially in longitudinal sections, and internally by an increase in the amount of white tissue. Experiments were undertaken during the spring and fall of 1997 and 1998 and the spring of 1999 to develop an action threshold for applying the insect growth regulators (IGRs) buprofezin and pyriproxyfen to manage B. argentifolii and irregular ripening. The IGRs were applied when predetermined thresholds were reached and were compared with a high rate of the systemic insecticide imidacloprid, which was applied at transplanting and provided season-long whitefly control. Only plots treated when the numbers of sessile nymphs (second through fourth instars) reached five per 10 leaflets consistently had both external and internal irregular ripening severity ratings similar to the imidacloprid standard. Results were similar for buprofezin and pyriproxyfen even though the modes of action differ. The five nymphs per 10 leaflets threshold lends itself to field scouting because nymphal counts completed in the field using the unaided eye supplemented with a 10x hand lens were linearly and significantly related to counts completed in the laboratory with a dissecting microscope.

Animals↗
PubMed2002

Particle film affects black pecan aphid (Homoptera: Aphididae) on pecan.

Three species of aphids attack pecan foliage, Carya illinoensis (Wang.) K. Koch, and cause economic damage. We tested a kaolin-based particle film against one of these aphid species, black pecan aphid, Melanocallis caryaefoliae (Davis). Effect of particle film on host selection, adult mortality, and production of nymphs by M. caryaefoliae was tested on seedling pecans in the laboratory. Fewer M. caryaefoliae adults selected treated foliage compared with untreated foliage. A higher percentage of adults that did select treated foliage were recovered from upper leaf surfaces compared with the percentage of adults recovered from upper leaf surfaces of untreated leaves. Observations with a microscope revealed an accumulation of particle film on aphid body parts, especially on tarsi, and strongly suggests that aphid mobility was restricted. Adult mortality was higher on treated foliage and led to an overall decrease in production of nymphs on those seedlings. In addition, we measured spectral properties of treated seedling pecan foliage. Light reflectance by treated foliage was increased and absorptance decreased compared with control foliage whereas transmittance of light through control and particle film-treated leaves was similar. We did not detect any phytotoxic effect on pecan due to application of particle film.

Animals↗