Biomedical subjects

P G Koehler

Publications and source records attributed to P G Koehler.

At least 19 recordsLinked to original sources

PubMed1999

Outdoor survival and development of immature cat fleas (Siphonaptera: Pulicidae) in Florida.

In north-central Florida, cat flea, Ctenocephalides felis felis Bouché, larvae survived outdoors year round. Their survival was greatest (up to 84.6%) outdoors in the fall, from September to November, when both temperatures and relative humidities were moderate. Female cat fleas developed faster than males. Development times for flea larvae were shortest (20-24 d) in June and July. From January to March, flea larval mortality was highest (91.7-100%) and development times the longest (36-50 d) outdoors. This was the result of low temperatures and low relative humidities associated with the passage of cold fronts during this time of year. Flea larvae survived light frosts in protected microhabitats such as inside a doghouse and under a mobile home.

Animals↗

PubMed1998

Host grooming efficiency for regulation of cat flea (Siphonaptera: Pulicidae) populations.

Grooming efficiency was studied by infesting domestic short-hair cats, Felis catus L., with known numbers of cat fleas, Ctenocephalides felis felis Bouché, then collecting the cat feces and extracting the fleas to determine how many had been groomed off, varying the infestation level. Some hosts were found to be significantly more efficient at grooming fleas than others, with the best groomer removing 17.6% of its flea burden daily, compared with only 4.1% removed by the poorest groomer. Cats were more efficient at grooming fleas at infestations of < 50 fleas and > 150 fleas. Mean on-host flea longevity was 7.8 d.

Animals↗

PubMed1997

A microcomputer-based activity meter for multiple animals.

We describe and validate a computer-video system that records and displays in real-time the activity of multiple specimens in a user-defined space, at user-defined intervals. The computer program uses image subtraction algorithms to record changes in video images, and stores observations in column format or as a series of 2-D matrices. The program was tested under various lighting conditions, backgrounds, specimen size and specimen speed. An AV model of Macintosh computer with video input from a camera or video cassette recorder was used to record and analyze the mechanical movement of spots on a turntable and the locomotor activity of an ant colony. The limitations and potential applications of the program are discussed.

Animals↗

PubMed1996

A microcomputer-based system for real-time analysis of animal movement.

A microcomputer-based video system for tracking, recording, and analyzing the movement of animals in two dimensions on variegated background in real-time has been developed and validated, both mechanically and with moving animals. Hardware and software (donationware) costs are low. Specimens visualized as small as 3 pixels long may be tracked in an arena that is 240 x 320 pixels in size. The results of tracking a mechanical moving spot are compared with a theoretical circular path. Comparisons between frame-by-frame human observation and computer generated X-Y coordinates are also presented. Applications of the tracking system include insect toxicology and pheromone bioassay, vertebrate locomotion studies, and basic research on taxes and kineses.

Animals↗

PubMed1995

Residual effectiveness of insect growth regulators applied to carpet for control of cat flea (Siphonaptera: Pulicidae) larvae.

Three insect growth regulators, fenoxycarb, methoprene, and pyriproxyfen, formulated as total release aerosols, were tested for their residual effectiveness on carpet in bioassays with cat flea, Ctenocephalides felis (Bouché), larvae. All treatments except methoprene produced significant mortality for the 7-mo duration of the test. In general, fenoxycarb and the higher rates of pyriproxyfen reduced adult flea emergence by > 80%.

Animals↗

PubMed1995

Chlorpyrifos formulation effect on airborne residues following broadcast application for cat flea (Siphonaptera: Pulicidae) control.

Airborne residues of 3 chlorpyrifos formulations were measured up to 50 h after broadcast treatment for flea control in residences. Insecticide formulation, time after treatment, ventilation regime, and height above floor affected airborne residues. Before spraying, chlorpyrifos residues were low or undetected. In nonventilated residences, chlorpyrifos residues peaked in 0-6 h after treatment at 38 ng/liter for emulsifiable, remained low at < 12 ng/liter for the microencapsulated, and sharply peaked in 1-2 h after treatment at 52 ng/liter for the aerosol formulation. Residues for all formulations then slowly declined through 50 h. In ventilated residences, chlorpyrifos residues peaked from 2 to 10 h after treatment at 25-27 ng/liter for emulsifiable, remained low at < 10 ng/liter, and sharply peaked in 0-2 h after treatment at 21 ng/liter for the aerosol formulation. Maximum airborne concentrations were 74 ng/liter for emulsifiable, 17 ng/liter for microencapsulated, and 61 ng/liter for aerosol chlorpyrifos.

Air Pollutants↗

PubMed1995

Airborne insecticide residues after broadcast application for cat flea (Siphonaptera: Pulicidae) control.

Airborne residues of chlorpyrifos, propetamphos, and permethrin were measured up to 50 h after broadcast treatment for cat flea, Ctenocephalides felis (Bouché), control in residences. Type of insecticide, time after treatment, ventilation regime, and height above floor significantly affected airborne residues. Before spraying chlorpyrifos, residues were low or undetected. In nonventilated residences, chlorpyrifos residues peaked 0-6 h after treatment at 38 ng/liter, then slowly declined through 50 h. In ventilated residences, chlorpyrifos residues peaked from 2 to 10 h after treatment at 25-27 ng/liter, then declined to 8 ng/liter at 50 h. Propetamphos and permethrin residues in nonventilated residences peaked at 0-2 h at 32-40 and 40-44 ng/liter, respectively. Propetamphos peaked at 12-17 ng/liter at 0-2 h in ventilated residences. Permethrin was not detected in any of the samples in ventilated residences. Maximum airborne concentrations were 74 ng/liter chlorpyrifos, 49 ng/liter propetamphos, and 54 ng/liter permethrin.

Air↗

PubMed1995

Larvicidal effects of boric acid and disodium octaborate tetrahydrate to cat fleas (Siphonaptera: Pulicidae).

Borate products varied in efficacy against larval cat fleas, Ctenocephalides felis felis Bouché, with some effective at rates of 23 micrograms/cm2 when larvae were exposed to the compounds in sand. Powdered boric acid, granular boric acid, and disodium octaborate tetrahydrate (Polybor) at rates of 200 micrograms/cm2 produced < or = 90% mortality of larvae exposed in carpet for 96 h. LC50 values of larvae exposed in treated carpets for 96 h were 23 micrograms/cm2 for powdered boric acid, 40 micrograms/cm2 for granular boric acid, and 47 micrograms/cm2 for polybor.

Animals↗

PubMed1994

Harborage width preferences of German cockroach (Dictyoptera: Blattellidae) adults and nymphs.

Adults and nymphal cohorts of the German cockroach, Blattella germanica (L.), were allowed 24 h to select preferred harborage widths from eight harborages between 1.59 and 12.72 mm (increments of 1.59 mm) in both individual and combined cohort studies. In individual cohort studies, 1- and 2-wk-old nymphs significantly preferred 1.59-mm-wide harborage, with 74 and 68%, respectively; 3- and 4-wk-old nymphs significantly preferred 3.18-mm-wide harborage, with 63 and 45%, respectively; 5-wk-old nymphs selected the 4.77-mm-wide harborage; and 6-wk-old nymphs were evenly distributed in 3.18- to 9.54-mm-wide harborages. Males were in 6.36- to 12.72-mm-wide harborages. Nongravid females (81%) were in 4.77-, 6.36-, and 11.13-mm-wide harborages; gravid females (94%) preferred 4.77- and 6.36-mm-wide harborages. The percentage of nymphs outside harborages decreased as cockroach age increased from 1 to 5 wk. In combined cohort studies, preferred harborage widths for all cohorts and sexes were 6.36-7.95 mm and 11.13-12.72 mm. The percentage of nymphs outside harborages was low and constant (< 4.57%) irrespective of age or sex.

Animals↗

PubMed1994

Influence of carbon dioxide anesthesia on chlorpyrifos toxicity in the German cockroach (Dictyoptera: Blattellidae).

Insecticide-susceptible (Orlando normal) and multi-insecticide-resistant (Village Green) adult male German cockroaches, Blattella germanica (L.), were exposed to carbon dioxide (CO2) gas in either varying durations or multiple exposures of fixed duration followed by topical treatment with acetone or chlorpyrifos (LD25) to evaluate the effect of CO2 anesthesia on chlorpyrifos toxicity. CO2 anesthesia did not increase chlorpyrifos toxicity in either strain regardless of exposure duration up to 1 h. However, multiple CO2-induced knockdowns alone caused mortality and increased chlorpyrifos toxicity. Twenty-four-hour weight loss was independent of CO2 duration exposure by strain. Village Green and Orlando cockroaches lost 5.3 and 7.6% of their weight in 24 h when treated with acetone and 10.5 and 12.8% when treated with chlorpyrifos, respectively. Conversely, 0- and 24-h weight loss increased with increasing CO2-induced knockdowns regardless of strain or topical treatment. Based on these results, CO2 used either once of limited duration (< or = 15 min) or multiple times of short duration, not to exceed four total knockdowns, does not increase chlorpyrifos toxicity in the adult male German cockroach.

Anesthesia↗

PubMed1994

Rearing improvements for the German cockroach (Dictyoptera: Blattellidae).

Known-age cohorts of three strains of German cockroach, Blattella germanica (L.), were mass-reared by establishing one rearing container each week (so that cockroaches within a container would be of known age). An average of 330-443 females was placed in oviposition units within these rearing containers. Percentage hatch of oothecae was 77.49-84.63%, resulting in an average of 12,258-16,359 nymphs per rearing container. Development of nymphs was similar for the three strains. Survivorship of nymphs to the adult stage was 19.95-29.56%; survivorship was significantly higher for the strain most recently colonized from the field. Adult emergence occurred at 6-7 wk, and average production per container was 2,834-3,971 cockroaches.

Animals↗

PubMed1993

Oral toxicity and repellency of borates to German cockroaches (Dictyoptera: Blattellidae).

The oral toxicities of boric acid and disodium octaborate tetrahydrate (DSOBTH) in dry-mixed, wet-mixed, and water-based solution baits were determined for German cockroaches, Blattella germanica L., in choice and nonchoice experiments. In dry-mixed, nonchoice bait tests, all cockroaches died within 1 wk. Time to mortality decreased as the concentration of boric acid increased. The LT50s for DSOBTH were not significantly different for any concentrations tested. In choice tests, the order of LT50s of boric acid and DSOBTH were 6.25% = 12.5% > 25% = 50% and 25% > 12.5% > 50% > 25%, respectively. Consumption of treated and control baits and the differences between the LT50s of the nonchoice and choice tests indicate repellency of the toxicants. Most German cockroaches died in 3-6 d in wet-mixed nonchoice tests, but all cockroaches survived the wet-mixed choice tests except at the lowest concentration of boric acid. This result indicated repellency. In nonchoice tests with water-based solutions, all cockroaches died in 5 d. In choice tests with boric acid solutions, mortality did not increase at concentrations > 1%. Choice/nonchoice ratios indicate no repellency of water-based solutions. In addition, consumption of treated and blank solutions was not significantly different for any concentration except 4% DSOBTH.

Administration, Oral↗

PubMed1993

Age- and sex-related effects in German cockroaches fed an allopurinol diet (Dictyoptera: Blattellidae).

The effects of feeding several ages of adult and nymphal German cockroaches a laboratory rat chow diet containing 0.10% allopurinol were investigated. All cockroaches fed the allopurinol diet suffered increased mortality. The range of LT50 values (the time required to kill 50% of an experimental cohort) for four ages of nymphs (1-8, 16-23, 21-28, and 28-35 d old following hatch) continuously fed the allopurinol diet was 1.36 wk (4.72-6.08 wk). Regardless of sex, young adult (1-7 d old following eclosion) cockroaches fed the allopurinol diet died significantly sooner than older adults (28-35 d old following eclosion); males died significantly sooner than females. All females fed the allopurinol diet as nymphs aborted their oothecae. Although an initial ootheca were hatched from cockroaches fed the allopurinol diet as adults, all subsequent oothecae were aborted. Untreated females mated with allopurinol-fed males experienced successful reproduction, but allopurinol-fed females mated with either allopurinol- or control diet-fed males failed to reproduce. Evidence suggests that cockroaches suffer increased mortality and reproductive failure from increased levels of hypoxanthine and xanthine.

Allopurinol↗

PubMed1992

Effect of methoprene and diflubenzuron on larval development of the cat flea (Siphonaptera: Pulicidae).

Cat flea larvae, Ctenocephalides felis Bouche, exposed to glass surfaces treated with methoprene concentrations from 0.127 to 1,270 ng/cm2 did not emerge as adults. Most larvae died in the third instar, but those exposed to the 0.127 ng/cm2 concentration formed larval-pupal intermediates. Larvae exposed to glass surface treated with diflubenzuron concentrations from 12.7 to 1,270 ng/cm2 died during the process of molting in all three instars. Exposure of larvae to 12.7 and 127 ng/cm2 diflubenzuron resulted in 15 and 5.2% adult emergence, respectively.

Animals↗

PubMed1992

Susceptibility of cockroaches (Dictyoptera: Blattellidae, Blattidae) to infection by Steinernema carpocapsae.

The susceptibility of American cockroaches, Periplaneta americana (L.); smoky brown cockroaches, P. fuliginosa (Serville); oriental cockroaches, Blatta orientalis L.; German cockroaches, Blattella germanica (L.); and brownbanded cockroaches, Supella longipalpa (F.), to Steinernema carpocapsae Weiser (All strain) was evaluated under laboratory conditions. A 1-ml water suspension containing 500,000 nematodes was placed on filter paper in a petri dish or the pad of a bait station. German, brown-banded, oriental, and smoky-brown cockroaches died within 1 d after placement in the petri dishes. The relative order for the LT50s were American greater than oriental greater than smoky-brown greater than brown-banded = German. All cockroaches actively groomed nematodes from legs and antennae of forced (petri dish) exposure. The LT50s for S. carpocapsae for nonforced (bait station) exposure were significantly greater than those for forced exposure. The LT50s were 3.25, 4.13, 9.86, and 11.38 d for brown-banded, German, oriental, and smoky-brown cockroaches, respectively. The relative order of the LT50s after forced (American greater than oriental greater than smoky-brown greater than German = brown-banded) and nonforced (American greater than smoky-brown greater than oriental greater than German greater than brown-banded) exposure to S. carpocapsae was inversely related to the moisture of their preferred habitats.

Animals↗

PubMed1992

Detection of insecticide resistance in the German cockroach (Dictyoptera: Blattellidae) with glue-toxin traps.

Glue that contained an insecticide was evaluated for its ability to yield useful toxicological data for German cockroaches, Blattella germanica (L.). Toxicities of three classes of insecticides were evaluated by topical applications (LD50) and exposure to insecticide-impregnated glue (LC50). Cockroaches that were resistant to topical insecticide applications were also resistant to the glue formulation. Reliability was greatest when mortality was scored 40 to 48 h after the cockroaches were placed on the glue. This method should be adaptable for insecticide resistance monitoring of German cockroaches.

Adhesives↗

PubMed1992

Diel patterns of cat flea (Siphonaptera: Pulicidae) egg and fecal deposition.

The quantity of eggs and feces deposited by replicate populations of cat fleas, Ctenocephalides felis (Bouché), from domestic house cats. Felis catus, were recorded at 1-h intervals over a 24-h period, in a photoperiod of 12:12 (L:D) (photophase, 0600-1800 hours [EST]). Egg production averaged 23.96 +/- 0.83 eggs per female per day and was greatest from 2400 to 0300 hours and lowest from 0700 to 0900 hours and from 1700 to 1900 hours. Daily fecal deposition was 0.77 +/- 0.03 mg feces per flea and did not vary significantly among hours. Flea eggs and adult feces were dropped continuously from infested cats, but significantly more eggs were shed at times of day when cats normally rest. More feces are concentrated in the small areas where cats rest than over the large areas they roam. Consequently, eggs and feces would not be deposited uniformly throughout the hosts home range, resulting in a clumped distribution of larval development sites at host resting areas.

Animals↗

PubMed1992

Spectrophotometric method of quantifying adult cat flea (Siphonaptera: Pulicidae) feces.

Cat flea, Ctenocephalides felis felis (Bouché), feces are an essential part of larval nutrition under natural conditions. The mass values of adult flea feces can be measured by dissolving samples of flea feces in Drabkin's reagent, filtering, centrifuging, and measuring absorbance spectrophotometrically at 540 nm. Either flea feces or air-dried host blood can be used to generate the standard curve used to convert absorbance (optical density) values into mass values. Debris collected from flea-infested house cats averaged 23.02 mg debris per cat per h with an average of 10.41 mg flea feces per cat per h. Flea feces deposited in the environment serve as potential larval food. Adult flea feces comprised an average of 44.28% of the debris deposited from infested domestic house cats in this study.

Animals↗