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Biomedical subjects

R B Davey

Publications and source records attributed to R B Davey.

At least 37 records · Page 2Linked to original sources
PubMed1999

Sequence analysis of the knockdown resistance-homologous region of the para-type sodium channel gene from pyrethroid-resistant Boophilus microplus (Acari: Ixodidae).

Using reverse transcription polymerase chain reaction and degenerate oligonucleotide primers, a partial para-homologous sodium channel cDNA was obtained from the southern cattle tick, Boophilus microplus (Canestrini). The cDNA sequence encoded the region in which knockdown resistance (kdr)-type mutations have been identified in numerous insect species. Comparison of deduced amino acids from the cDNA sequence showed high similarity with sodium channels from other species, particularly in highly conserved repeat domains of the sodium channel. Analysis of the kdr-homologous region of the genomic DNA sequences from several susceptible and pyrethroid-resistant tick strains did not detect mutations. The result suggests novel mutations in the sodium channel gene or metabolic detoxification may be involved in the resistance to pyrethroids in this tick.

Amino Acid Sequence↗
PubMed1998

Efficacy of amitraz (Taktic 12.5% EC) as a dip for the control of Boophilus microplus (Canestrini) (Acari: Ixodidae) on cattle.

Four groups of cattle infested with Boophilus microplus (Canestrini) were each dipped in a different concentration of amitraz diluted from a 12.5% EC formulation to determine the efficacy and performance of the product in an 11,400 l dipping vat. Except for the period when heifers were dipped, animals were restrained in stanchions placed individually inside 3.3 x 3.3 m2 stalls within an open-sided barn. The amitraz in the vat was stabilized with hydrated lime to maintain a pH of ca. 12. Analyses of vat samples showed that concentrations of amitraz in the vat were 7.6 to 13% lower than the targeted concentrations of 0.010, 0.015, 0.020, and 0.025% active ingredient (AI) for dilutions prepared according to instructions on the manufacturer's label. The large quantity of hydrated lime added to the vat (10 kg/1000 l) interfered with the HPLC analysis of vat samples. Therapeutic efficacy of each of the four observed concentrations (0.0088, 0.0131, 0.0174, and 0.0231% AI) of amitraz was excellent (> 99% control). However, the rapid detachment of all ticks from an animal within a few hours after treatment with amitraz, that has been frequently observed, was not pronounced in the present study. Only 47% of the B. microplus detached in the first 4 h post-treatment, and 84% detached within the first 24 h. All of the treatments, except the lowest concentration, provided protection of cattle against re-infestation by B. microplus larvae for 14 days post-treatment. Possibly as a result of the formation of a compact layer of lime and amitraz on the bottom after the vat was undisturbed for six weeks, intense agitation was required to re-suspend the active ingredient.

Animals↗
PubMed1998

Therapeutic and persistent efficacy of fipronil against Boophilus microplus (Acari: Ixodidae) on cattle.

Cattle infested with all parasitic life-stages of Boophilus microplus (Canestrini) were treated once with a pour-on formulation of fipronil at 0.25, 0.5, or 1.0% active ingredient (AI) to determine the therapeutic efficacy. Additionally, cattle were infested at weekly intervals for 13 consecutive weeks after treatment to determine the persistent effectiveness of the three concentrations. Results of therapeutic efficacy of fipronil showed that with each increase in concentration there was a corresponding and often significant (P < 0.05) decrease in the numbers, fecundity and fertility of engorged females. The overall control of the Index of Reproduction (IR) achieved at 0.25 and 0.5% AI was 86.2 and 94.3%, respectively, while the control of the IR at the 1.0% AI concentration was 99.7%. The persistent efficacy of fipronil, like the therapeutic efficacy, was also dose related. The 0.25% AI treatment failed to provide complete protection (100%) against larval reinfestation, although control of the IR remained high (> 95%) for the first 6 weeks after treatment. In contrast, at 0.5% AI the control of the IR remained at 100% for the first 4 weeks after treatment, and was > 90% for an additional 2 weeks (6 weeks posttreatment). The 1.0% AI concentration afforded the longest residual activity, providing virtually 100% protection against larval reinfestation for 8 weeks after treatment was applied. Based on the results, neither the 0.25 or 0.5% AI concentration completely eliminated the immature stages of the tick (nymphs and larvae) on the host at the time of treatment (therapeutic efficacy), and the residual activity (persistent efficacy) did not prevent reinfestation by larvae for long periods after treatment. While the 1.0% AI concentration provided both therapeutic and residual efficacy that would be suitable for use in the eradication program, caution is still warranted because a few engorged females detached for up to 25 days after treatment, although none reproduced after the 6th day.

Administration, Topical↗
PubMed1998

Observations of the rhythm of detachment of engorged female Boophilus annulatus (Acari: Ixodidae) from cattle.

A bimodal, diurnal rhythm of detachment was observed for engorged female Boophilus annulatus fed on Hereford heifers confined in individual stalls in an open-sided barn and exposed to ambient climate and light. In 3 experiments during which hosts were fed each morning and evening, a morning period of increased detachment activity occurred during a 6-h period centered around the 2-h collecting interval in which sunrise occurred. A 2nd peak of activity occurred during the 2-h interval that began 6-8 h later. Seventy-four to 84% of the total detachment occurred during these two 6-h intervals and most of the detachment (44-62%) occurred during the afternoon period. These experiments were done in July, September, and January when daylengths were 13 h, 27 min; 12 h, 22 min; and 10 h, 37 min, respectively. In a 4th experiment in which groups of hosts were fed at different times of the day, maximal percentages of 41.5 and 38.3 of the total detachment from morning-fed or both morning and evening-fed heifers, respectively, occurred during the 2-h interval in which the sun rose instead of during the evening. During the evening peak period, the number of engorged females that detached from these 2 groups of heifers was approximately 1/3-1/4 the number that detached during the peak period in the morning. In contrast, 43.6% of the engorged females in the evening-fed group detached during an 8-h morning period of increased detachment activity that began in the interval between 0200 and 0400 hours. About the same percentage of the ticks (38.5) detached during a 6-h period that began at 1400 hours. The less precisely delimited pattern of detachment of engorged females from cattle fed only in the evening, as contrasted with the rhythm observed for ticks that detached from heifers fed in the morning or both morning and evening, indicates that the nutritional or physiological state of the host may influence the rhythm exogenously. Whether the morning or evening peak of detachment activity is dominant is a question that remains unresolved.

Animals↗
PubMed1998

Comparison of genomic DNA in various strains of Boophilus microplus (Acari: Ixodidae).

The conventional method of identifying acaricide resistance in a suspect tick population by the United Nations Food and Agriculture Organization packet assay is a laborious and time-consuming process. DNA probes have been demonstrated as rapid and accurate tools for detecting pesticide resistance in insect species. Random-amplified polymorphic DNA (RAPD) has been used by other groups to differentiate species of mosquitoes and populations within a mosquito species. By using different arbitrary oligonucleotides as primers with RAPD, we have demonstrated that various strains of Boophilus microplus (Canestrini) show different patterns of DNA fragments on agarose gel electrophoresis. The unique DNA fragments may be useful for developing probes that can detect acaricide resistance in field pest populations.

Animals↗
PubMed1998

In vitro and in vivo evaluations of a strain of Boophilus microplus (Acari: Ixodidae) selected for resistance to permethrin.

A strain of Boophilus microplus (Canestrini) was selected fro resistance to permethrin by pressuring larvae with increasing doses (range, 0.05-0.35% [AI]) through successive generations (generations F2-F7). At the beginning of the selection process (F2), the pyrethroid resistant (PR) strain was 5.4 times more resistant to permethrin than the pyrethroid susceptible (PS) strain, and the level of resistance increased in each successive generation of the PR strain, reaching a resistance factor (resistance factor) of 20.9 in the F7 generation. Thus, in only 5 generations the level of resistance in the PR strain was increased by 4-fold. The efficacy of permethrin was evaluated by dipping cattle infested with the PS strain and cattle infested with the F7 generation of the PR strain in a vat at 0.057% (AI) (Coopers Animal Health, Mundelein, IL; recommended concentration). Evaluation of the PS strain showed that untreated cattle produced significantly (P < 0.05) more females with a higher index of reproduction than treated cattle. Additionally, biological factors (female weight, egg mass weight, and percent egg hatch) associated with the untreated females were all significantly (P < 0.05) greater than treated females. Conversely, results obtained from the PR strain showed that tick numbers, index of reproduction value, and biological parameters of females in the untreated group were not significantly different (P > 0.05) from those of the treated group. The overall control achieved in the PS strain (99.2%) was significantly higher (P < 0.05) than that of the PR strain (35.7%). The results of the study as they relate to the United States Boophilus Eradication Program are discussed.

Animals↗
PubMed1997

Orchidopexy: the relative importance of each step of mobilisation.

Measurements were recorded during 313 orchidopexies to assess the relative importance of each step of the procedure. Division of the sac or processus accounts for 60% of the increased length of the cord (1.453 cm), whilst the remaining 40% (1.048 cm) of the total net gain (2.501 cm) is due to dissection within the internal inguinal ring. Division of the lateral bands is an essential step to achieve a successful orchidopexy.

Adolescent↗
PubMed1997

Undescended testes: early versus late maldescent.

A review of 468 orchidopexies was undertaken to ascertain the importance of a complete hernial sac extending to or beyond the testis. A hernial sac was present in 84% (171/202) of testes in patients under 5 years of age, in contrast to 23% (61/266) in patients over 5 years. It seems reasonable to presume that the failure of the hernial sac to close is secondary to failure of normal descent, which in turn is due to antenatal factors and may be classified as "early maldescent". In the older age group maldescent is due to failure of the last stage of descent, which should occur in the 5- to 10-year prepubertal age period ("late maldescent", or the "ascending" testis). The cause of late maldescent is not due to a short processus, as this increases in length with age (approximately 0.5 cm/year), unless the persistence of the processus itself is the cause. A classification of early or late maldescent is suggested.

Age Factors↗
PubMed1996

Burn scar contracture release: a simplified technique utilizing contact media.

A technique to overcome the problems of inlay grafting for burn scar contracture release is described. A greater release can be achieved by moving the point of release away from the flexure crease, with the added advantage of grafting on to a 'flat non-mobile' surface. A simplified method of graft fixation and compression is described, along with the use of contact media in the postoperative management to prevent graft shrinkage and the recurrence of contracture. During a 6-year period, burn scar contracture release with inlay grafting was performed on 24 patients (10 limbs with 17 split-skin grafts and 14 fingers with 21 full-thickness grafts) with no recurrence.

Burns↗
PubMed1995

Bladder, urethral, and vaginal duplication.

The authors report on an infant girl with bladder duplication. There was complete duplication of the bladder, urethra, uterus, and vagina, associated with a urogenital sinus and an anterior ectopic anus. Despite careful attempts at examination, endoscopy, and organ imaging, the anatomy was not completely defined before surgical exploration. A satisfactory cosmetic result and functional lower genitourinary tract has been obtained.

Abnormalities, Multiple↗
PubMed1995

Childhood burns.

Attending to pain relief, preventing shock and infection and obtaining early skin cover with thought to subsequent scar management are the main thrusts of this article. The author also emphasises the point that prevention through education needs to be more aggressive. A detailed approach to treatment is given.

Adolescent↗
PubMed1994

Comparative reproduction and nonparasitic development of Boophilus microplus and hybridized Boophilus ticks (Acari: Ixodidae) under natural field conditions in subtropical south Texas.

The reproductive biology and nonparasitic development of Boophilus microplus (Canestrini) and hybridized Boophilus ticks (B. annulatus (Say) male x B. microplus female) held under natural field conditions in south Texas throughout the year were compared. Comparisons between the two types of ticks indicated that the ovipositional biology (percentage of ovipositing females and number of eggs laid) of the females favored hybrid ticks during some months and B. microplus ticks during other months. However, on a year long basis, there was virtually no difference in the percentage of ovipositing females or in the number of eggs deposited by hybrid females as compared to B. microplus. The duration of each nonparasitic development period (preoviposition period, incubation period of eggs, and larval longevity) showed that both types of ticks had very similar developmental and survival rates during the year. Generally the difference in duration of each of the nonparasitic parameters was < 8 days, leading to a high degree of synchrony of the nonparasitic developmental rates between the two types of ticks. On the other hand, egg hatchability of hybrid ticks was consistently lower than pure-strain B. microplus throughout the year with significantly lower hatch rates occurring in April, July, August, October, and November. Thus, results obtained on percentage of ovipositing females, number of eggs laid, preoviposition period, incubation period of eggs, and larval longevity provide encouragement for the possible use of sterile hybrid males as a means of eliminating a native B. microplus population. In contrast, results of the egg hatchability of the two types of ticks indicate that the selective advantage afforded to B. microplus could have an adverse affect on the success of a sterile hybrid male program by making the number of hybrid ticks necessary to eliminate a native population prohibitively high.

Animals↗
PubMed1993

Leiomyosarcoma of the saphenous vein in a child with 12-year follow-up.

Leiomyosarcomas of the vasculature are exceedingly rare tumors in childhood. The case of a 2-year-old girl who underwent three local excisions with two courses of adjuvant chemotherapy over 3 years for a leiomyosarcoma of a saphenous vein tributary is described. Follow-up over the following 9 years has shown no evidence of further recurrence or metastases suggesting that cure has been achieved. Treatment options are discussed and pertinent literature is reviewed.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

Stagewise mortality, ovipositional biology, and egg viability of Boophilus annulatus (Acari: Ixodidae) on Boselaphus tragocamelus (Artiodactyla: Bovidae).

The stagewise mortality, ovipositional biology, and egg viability of the cattle tick, Boophilus annulatus (Say), on nilgai antelope, Boselaphus tragocamelus Pallas, was compared with ticks reared on Bos taurus (Hereford) cattle. Mortality was highest during the larval stage on both host species, but larval mortality on nilgai (78.6%) was significantly higher than on cattle (45.6%) hosts. Mortality during the nymphal stage was also significantly higher on nilgai (49.3%) than on cattle (13.9%). During adult female development, although the mortality rate on nilgai was 40.9% compared with no mortality of females on cattle, this difference was not significant. Significantly fewer ticks reached repletion on nilgai (4.0 females per animal) than on cattle (48.5 females per animal). The mean female weight and egg mass weight of ticks obtained from cattle were significantly higher than ticks produced from nilgai. On the other hand, no differences in mean conversion efficiency index (CEI), preoviposition period, incubation period, or egg hatch were observed among ticks obtained from the two host animals. Although nilgai produce fewer replete females, and the females that do survive are smaller and produce smaller egg masses, nilgai cannot be disregarded in an eradication program. The fact that even a small number of viable ticks is able to reproduce successfully on nilgai could lead to the failure of current eradication strategies by compromising the required quarantine interval.

Animals↗
PubMed1992

Radiological assessment of duodenal calibre in congenital duodenal obstruction.

A review of barium meal studies in 32 cases of congenital intrinsic duodenal obstruction (CDO) from the Adelaide Children's Hospital was performed to assess and measure pre and post operative duodenal dilatation. Comparisons were made with a group of 153 normal barium studies from the same Hospital with a view to quantifying normal and abnormal proximal duodenal calibre. Duodenal size was expressed as a ratio D1/L1, (diameter of 1st part of duodenum/height of first lumbar vertebra). In this study a normal range of duodenal diameter was found to be 0.90 to 1.62 (+/- 2 SD from mean), with a mean of 1.26. The CDO patients recorded a range of postoperative ratios on first follow-up barium studies of between 1.2 and 4.5 with a mean of 2.28. Where serial studies had been performed, duodenal diameter was found to show some decrease in size postoperatively. In patients who underwent surgery for membrane obstruction there was a trend towards normalisation of duodenal diameter over time, compared with the atresia group. However, this difference did not reach statistical significance.

Barium Sulfate↗
PubMed1992

Efficacy of cyhalothrin and lambdacyhalothrin against Boophilus microplus (Acari: Ixodidae).

A study was conducted to determine the efficacy of cyhalothrin and lambdacyhalothrin as a whole-body spray and lambdacyhalothrin as a pour-on application on cattle infested with Boophilus microplus (Canestrini). A laboratory bioassay was also done with both spray formulations. Cattle were infested with all parasitic life stages of B. microplus, then treated with 0.007 or 0.01% (AI) concentrations of cyhalothrin as a spray; 0.005, 0.007, or 0.01% (AI) concentrations of lambdacyhalothrin as a spray, or 1% (AI) lambdacyhalothrin as a pour-on. As determined by calculations of the index of reproduction (IR), the 0.007 and 0.01% (AI) cyhalothrin provided 92.4 and 97.3% control, respectively; the 0.005, 0.007, and 0.01% (AI) lambdacyhalothrin provided 92.4, 98.2 (average of two treatments) and 99.3% control, respectively; and the lambdacyhalothrin pour-on treatment provided < 50% control. Bioassay results indicated lambdacyhalothrin to be twice as effective as cyhalothrin against B. microplus.

Animals↗
PubMed1992

Test for assortative mating between Boophilus microplus and Boophilus annulatus (Acari: Ixodidae).

The closely related cattle ticks, Boophilus microplus (Canestrini) and B. annulatus (Say), were tested for possible assortative mating under conditions designed to mimic those in the field. Patterns in the numbers of the four possible types of matings were generally indicative of a preference for conspecific mates in both species. There were significantly more conspecific and fewer interspecific matings than would be predicted from the observed frequencies of males and females among the two species had they mated at random.

Animals↗