Simultaneous polarimeter retrievals of microphysical aerosol and ocean color parameters from the "MAPP" algorithm with comparison to high-spectral-resolution lidar aerosol and ocean products.

We present an optimal-estimation-based retrieval framework, the microphysical aerosol properties from polarimetry (MAPP) algorithm, designed for simultaneous retrieval of aerosol microphysical properties and ocean color bio-optical parameters using multi-angular total and polarized radiances. Polarimetric measurements from the airborne NASA Research Scanning Polarimeter (RSP) were inverted by MAPP to produce atmosphere and ocean products. The RSP MAPP results are compared with co-incident lidar measurements made by the NASA High-Spectral-Resolution Lidar HSRL-1 and HSRL-2 instruments. Comparisons are made of the aerosol optical depth (AOD) at 355 and 532 nm, lidar column-averaged measurements of the aerosol lidar ratio and Ångstrøm exponent, and lidar ocean measurements of the particulate hemispherical backscatter coefficient and the diffuse attenuation coefficient. The measurements were collected during the 2012 Two-Column Aerosol Project (TCAP) campaign and the 2014 Ship-Aircraft Bio-Optical Research (SABOR) campaign. For the SABOR campaign, 73% RSP MAPP retrievals fall within ±0.04 AOD at 532 nm as measured by HSRL-1, with an R value of 0.933 and root-mean-square deviation of 0.0372. For the TCAP campaign, 53% of RSP MAPP retrievals are within 0.04 AOD as measured by HSRL-2, with an R value of 0.927 and root-mean-square deviation of 0.0673. Comparisons with HSRL-2 AOD at 355 nm during TCAP result in an R value of 0.959 and a root-mean-square deviation of 0.0694. The RSP retrievals using the MAPP optimal estimation framework represent a key milestone on the path to a combined lidar+polarimeter retrieval using both HSRL and RSP measurements.

Calibration of a high spectral resolution lidar using a Michelson interferometer, with data examples from ORACLES.

The NASA Langley airborne second-generation High Spectral Resolution Lidar (HSRL-2) uses a density-tuned field-widened Michelson interferometer to implement the HSRL technique at 355 nm. The Michelson interferometer optically separates the received backscattered light between two channels, one of which is dominated by molecular backscattering, while the other contains most of the light backscattered by particles. This interferometer achieves high and stable contrast ratio, defined as the ratio of particulate backscatter signal received by the two channels. We show that a high and stable contrast ratio is critical for precise and accurate backscatter and extinction retrievals. Here, we present retrieval equations that take into account the incomplete separation of particulate and molecular backscatter in the measurement channels. We also show how the accuracy of the contrast ratio assessment propagates to error in the optical properties. For both backscattering and extinction, larger errors are produced by underestimates of the contrast ratio (compared to overestimates), more extreme aerosol loading, and-most critically-smaller true contrast ratios. We show example results from HSRL-2 aboard the NASA ER-2 aircraft from the 2016 ORACLES field campaign in the southeast Atlantic, off the coast of Africa, during the biomass burning season. We include a case study where smoke aerosol in two adjacent altitude layers showed opposite differences in extinction- and backscatter-related Ångström exponents and a reversal of the lidar ratio spectral dependence, signatures which are shown to be consistent with a relatively modest difference in smoke particle size.

Coronavirus Disease 2019 in Patients With End-Stage Kidney Disease on Hemodialysis in Guatemala.

INTRODUCTION: Coronavirus disease 2019 (COVID-19) is public health concern across the world. Data on the epidemiology among patients on hemodialysis in Latin America and low- and middle-income countries are limited. METHODS: Using electronic medical records from the second largest dialysis network in Guatemala, we performed a retrospective analysis of all adult patients on hemodialysis with the diagnosis of COVID-19 to estimate incidence of infection and to describe the demographics, comorbidities, and outcomes. We stratified incidence rate by region. We reviewed data from May 1 to July 31, 2020, with outcome data ascertained up to August 28, 2020. RESULTS: Of 3201 patients undergoing hemodialysis, 325 patients were diagnosed with COVID-19 (incidence rate 102/1000 patients on hemodialysis, compared with 3/1000 in the general population). Incidence was higher in the Central region (207/1000) and lowest in the Southeast region (33/1000), and unlike in the general population, the incidence was lower in Guatemala City. The mean age of patients diagnosed with COVID-19 was 51.1 years (standard deviation [SD] 14.8 years), and 84 (25.8%) were female. The median length of hospital stay was 12 days (interquartile range [IQR] 10-16 days). Two hundred twenty-nine (69.8%) of the patients recovered, 90 patients died (27.7%), and 6 (1.8%) patients were still in the hospital at the time of last follow-up. CONCLUSION: The incidence of diagnosed COVID-19 in Guatemalan patients on hemodialysis was much higher than reported in the general population, with outcomes similar to those described in high-income countries. Rural regions had higher incidence rates than the major metropolitan area.

Reconciling Assumptions in Bottom-Up and Top-Down Approaches for Estimating Aerosol Emission Rates From Wildland Fires Using Observations From FIREX-AQ.

Accurate fire emissions inventories are crucial to predict the impacts of wildland fires on air quality and atmospheric composition. Two traditional approaches are widely used to calculate fire emissions: a satellite-based top-down approach and a fuels-based bottom-up approach. However, these methods often considerably disagree on the amount of particulate mass emitted from fires. Previously available observational datasets tended to be sparse, and lacked the statistics needed to resolve these methodological discrepancies. Here, we leverage the extensive and comprehensive airborne in situ and remote sensing measurements of smoke plumes from the recent Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) campaign to statistically assess the skill of the two traditional approaches. We use detailed campaign observations to calculate and compare emission rates at an exceptionally high-resolution using three separate approaches: top-down, bottom-up, and a novel approach based entirely on integrated airborne in situ measurements. We then compute the daily average of these high-resolution estimates and compare with estimates from lower resolution, global top-down and bottom-up inventories. We uncover strong, linear relationships between all of the high-resolution emission rate estimates in aggregate, however no single approach is capable of capturing the emission characteristics of every fire. Global inventory emission rate estimates exhibited weaker correlations with the high-resolution approaches and displayed evidence of systematic bias. The disparity between the low-resolution global inventories and the high-resolution approaches is likely caused by high levels of uncertainty in essential variables used in bottom-up inventories and imperfect assumptions in top-down inventories.

Photochemical model evaluation of 2013 California wild fire air quality impacts using surface, aircraft, and satellite data.

The Rim Fire was one of the largest wildfires in California history, burning over 250,000 acres during August and September 2013 affecting air quality locally and regionally in the western U.S. Routine surface monitors, remotely sensed data, and aircraft based measurements were used to assess how well the Community Multiscale Air Quality (CMAQ) photochemical grid model applied at 4 and 12 km resolution represented regional plume transport and chemical evolution during this extreme wildland fire episode. Impacts were generally similar at both grid resolutions although notable differences were seen in some secondary pollutants (e.g., formaldehyde and peroxyacyl nitrate) near the Rim fire. The modeling system does well at capturing near-fire to regional scale smoke plume transport compared to remotely sensed aerosol optical depth (AOD) and aircraft transect measurements. Plume rise for the Rim fire was well characterized as the modeled plume top was consistent with remotely sensed data and the altitude of aircraft measurements, which were typically made at the top edge of the plume. Aircraft-based lidar suggests O3 downwind in the Rim fire plume was vertically stratified and tended to be higher at the plume top, while CMAQ estimated a more uniformly mixed column of O3. Predicted wildfire ozone (O3) was overestimated both at the plume top and at nearby rural and urban surface monitors. Photolysis rates were well characterized by the model compared with aircraft measurements meaning aerosol attenuation was reasonably estimated and unlikely contributing to O3 overestimates at the top of the plume. Organic carbon was underestimated close to the Rim fire compared to aircraft data, but was consistent with nearby surface measurements. Periods of elevated surface PM2.5 at rural monitors near the Rim fire were not usually coincident with elevated O3.

Dose determination of a novel formulation of metaflumizone plus amitraz for control of cat fleas (Ctenocephalides felis felis) and brown dog ticks (Rhipicephalus sanguineus) on dogs.

A novel spot-on formulation containing metaflumizone and amitraz (ProMeris/ProMeris Duo for Dogs, Fort Dodge Animal Health, Overland Park, KS) was evaluated in a laboratory study to determine the appropriate dose for efficacy against fleas and ticks on dogs for 1 month. Thirty-six Beagles were randomly allocated to six equal groups and individually housed. One group remained nontreated. Another was treated with a placebo formulation (solvents with no active ingredients). Three groups of dogs were treated topically with the metaflumizone plus amitraz formulation (150mg of each of metaflumizone and amitraz/ml), at volumes providing doses of 10, 20 and 40mgeachactive/kg. The final group was treated with a commercial spot-on providing 6.7mgfipronil/kg. All treatments were applied to the skin at a single spot between the scapulae on Day 0. Dogs were infested with 50 adult brown dog ticks (Rhipicephalus sanguineus) on each of Days -2, 5, 12, 19, 26, 33 and 40, and with 100 cat fleas (Ctenocephalides felis felis) on Days -1, 6, 13, 20, 27, 34 and 41. Dogs were examined and parasites "finger counted" on Day 1 to estimate knock down efficacy, and all animals were comb counted to determine the numbers of viable fleas and ticks on Days 7, 14, 21, 28, 35 and 42. There were no significant differences in parasite counts between the nontreated control and the placebo-treated control groups for either fleas or ticks (P>0.05) except for very slight reductions on Day 7 for fleas and Day 14 for ticks, demonstrating that the formulation excipients had no activity. The qualitative finger counts on Day 1 indicated that all of the insecticidal treatments resulted in a noticeable reduction in flea and tick numbers within 1 day of treatment. All of the metaflumizone and amitraz treatments and fipronil resulted in significantly lower flea and tick numbers relative to nontreated controls on all posttreatment count days (P<0.05). For the metaflumizone plus amitraz treatments, mean flea and tick counts for the 10mg/kg dose were significantly higher than those for the 20mg/kg dose (P<0.05) from Day 21 on. There was no significant advantage provided by the 40mg/kg dose over the 20mg dose throughout the entire study (P>0.05). The two higher metaflumizone plus amitraz doses provided >95% control of fleas and >90% control of ticks for at least 35 days after treatment, and this level of control was similar to that of the commercial fipronil product. The 20mg/kg dose was selected as the minimum commercial dose rate to provide effective flea and tick control for at least 1 month following a single treatment.

Efficacy of a novel formulation of metaflumizone for the control of fleas (Ctenocephalides felis) on cats.

A novel spot-on formulation containing metaflumizone (ProMeris for Cats, Fort Dodge Animal Health, Overland Park, KS) was evaluated in five laboratory studies to determine the duration of residual efficacy in cats against fleas after a single spot treatment. In each study, eight domestic shorthair cats were randomly allocated to each treatment group and individually housed. One group in each study remained non-treated. In one study, an additional group of eight cats was treated with a placebo formulation. Cats were treated topically with metaflumizone formulation to provide a dose of at least 40mg metaflumizone/kg. Cats were infested with 100 cat fleas (Ctenocephalides felis felis) once per week for approximately 8 weeks. Cats were comb counted 48h after treatment and each infestation to determine the number of viable fleas present. There were no significant differences in flea counts between the non-treated control and the placebo-treated control (P>0.05) other than a 26% reduction at week 1, demonstrating that the formulation excipients had no activity. Metaflumizone treatment resulted in significantly lower flea numbers relative to non-treated controls on all post-treatment count days (P<0.05). Metaflumizone provided >90% control of flea infestations up to 7 weeks following a single treatment.

Confirmation of the efficacy of a novel formulation of metaflumizone plus amitraz for the treatment and control of fleas and ticks on dogs.

A novel spot-on formulation containing metaflumizone plus amitraz (ProMeris/ProMeris Duo for Dogs, Fort Dodge Animal Health, Overland Park, KS) was evaluated in four laboratory studies to confirm efficacy against fleas and ticks on dogs for 1 month. Three different strains of cat flea (Ctenocephalides felis felis) and four tick species were used. Rhipicephalus sanguineus and Dermacentor variabilis were evaluated concurrently in two studies and Ixodes scapularis and Amblyomma americanum in one study each. In all studies, dogs were randomly allocated to treatment groups and compared with nontreated dogs. One study also included a placebo treatment and a commercial product containing fipronil plus S-methoprene. All treatments were applied to the skin at a single spot between the scapulae on Day 0. Dogs were infested with fleas and/or ticks prior to treatment and then reinfested at weekly intervals for 6 weeks after treatment and evaluated for efficacy at 1 or 2 days after treatment and each reinfestation. These studies confirmed that treatment with ProMeris for Dogs at the proposed commercial dose rate rapidly controlled existing infestations of fleas and ticks on dogs. Treatment provided control of reinfesting fleas for up to 6 weeks and at least 4 weeks control of ticks. Efficacy was confirmed in a variety of dog breeds against three different flea strains and four common species of ticks found on dogs in the United States.

The MERRA-2 Aerosol Reanalysis, 1980 Onward. Part II: Evaluation and Case Studies.

The Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), is NASA's latest reanalysis for the satellite era (1980 onward) using the Goddard Earth Observing System, version 5 (GEOS-5), Earth system model. MERRA-2 provides several improvements over its predecessor (MERRA-1), including aerosol assimilation for the entire period. MERRA-2 assimilates bias-corrected aerosol optical depth (AOD) from the Moderate Resolution Imaging Spectroradiometer and the Advanced Very High Resolution Radiometer instruments. Additionally, MERRA-2 assimilates (non bias corrected) AOD from the Multiangle Imaging SpectroRadiometer over bright surfaces and AOD from Aerosol Robotic Network sunphotometer stations. This paper, the second of a pair, summarizes the efforts to assess the quality of the MERRA-2 aerosol products. First, MERRA-2 aerosols are evaluated using independent observations. It is shown that the MERRA-2 absorption aerosol optical depth (AAOD) and ultraviolet aerosol index (AI) compare well with Ozone Monitoring Instrument observations. Next, aerosol vertical structure and surface fine particulate matter (PM2.5) are evaluated using available satellite, aircraft, and ground-based observations. While MERRA-2 generally compares well to these observations, the assimilation cannot correct for all deficiencies in the model (e.g., missing emissions). Such deficiencies can explain many of the biases with observations. Finally, a focus is placed on several major aerosol events to illustrate successes and weaknesses of the AOD assimilation: the Mount Pinatubo eruption, a Saharan dust transport episode, the California Rim Fire, and an extreme pollution event over China. The article concludes with a summary that points to best practices for using the MERRA-2 aerosol reanalysis in future studies.

The MERRA-2 Aerosol Reanalysis, 1980 - onward, Part I: System Description and Data Assimilation Evaluation.

The Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) updates NASA's previous satellite era (1980 - onward) reanalysis system to include additional observations and improvements to the Goddard Earth Observing System, Version 5 (GEOS-5) Earth system model. As a major step towards a full Integrated Earth Systems Analysis (IESA), in addition to meteorological observations, MERRA-2 now includes assimilation of aerosol optical depth (AOD) from various ground- and space-based remote sensing platforms. Here, in the first of a pair of studies, we document the MERRA-2 aerosol assimilation, including a description of the prognostic model (GEOS-5 coupled to the GOCART aerosol module), aerosol emissions, and the quality control of ingested observations. We provide initial validation and evaluation of the analyzed AOD fields using independent observations from ground, aircraft, and shipborne instruments. We demonstrate the positive impact of the AOD assimilation on simulated aerosols by comparing MERRA-2 aerosol fields to an identical control simulation that does not include AOD assimilation. Having shown the AOD evaluation, we take a first look at aerosol-climate interactions by examining the shortwave, clear-sky aerosol direct radiative effect. In our companion paper, we evaluate and validate available MERRA-2 aerosol properties not directly impacted by the AOD assimilation (e.g. aerosol vertical distribution and absorption). Importantly, while highlighting the skill of the MERRA-2 aerosol assimilation products, both studies point out caveats that must be considered when using this new reanalysis product for future studies of aerosols and their interactions with weather and climate.

ANF (99-126) and its propeptide, ANF (1-16) are secreted simultaneously from the human atrial myocyte.

We have raised antisera to two synthetic peptides representing different portions of the human pro-atrial natriuretic factor (ANF) molecule; one antiserum identifies active human ANF, the 28-amino-acid sequence on the C-terminal end of the prohormone [ANF (99-126)], and the other detects ANF (1-16), the first 16-amino-acid sequence at the N-terminal end of the prohormone. With ultrastructural immunocytochemistry we have studied the distribution staining for both peptides within the myocytes in surgically excised human auricular appendages. Most of the endocrine granules stained with equal density for both ANF (1-16) and ANF (99-126). Also, double immuno-staining techniques on the same tissue section showed that both the C-terminal peptide and the N-terminal peptide co-existed within the same endocrine granules. It has been shown that, like other endocrine cells, atrial myocytes secrete their stored peptides by exocytosis of their granules. Therefore, our observations suggest that both the main active hormone, ANF (99-126), and the N-terminal propeptide ANF (1-16) are secreted simultaneously from the cell.

Structural analysis of placental terminal villi from growth-restricted pregnancies with abnormal umbilical artery Doppler waveforms.

The abnormal umbilical artery Doppler waveform represented by absent end-diastolic flow velocity (AEDFV) identifies a group of preterm small-for-gestational age fetuses that are at high risk of perinatal death due to chronic fetal hypoxia. The placental ischaemia that results from inadequate trophoblast invasion of spiral arterioles leads to an assumption of placental villous hypoxia, though an alternative explanation is that the placenta fails to adequately transfer oxygen to the fetus from the intervillous space. Because oxygen transport takes place within the terminal villi, we undertook the first detailed studies of villous ultrastructure structure and immunohistochemistry in order to determine the likely origin of fetal hypoxia in this condition. Terminal villi were examined ultrastructurally using transmission electron microscopy and by immunohistochemical localization of matrix molecules (laminin and collagens I, III and IV) and a marker of cell proliferation (MIB-1), in 16 small-for-gestational age pregnancies with AEDFV in the umbilical artery [deemed to have intrauterine growth restriction (IUGR)] and in 16 gestation age-matched controls. Terminal villi from the IUGR cases were smaller in diameter (P < 0.02) and had several abnormal features in comparison with the controls; increased syncytial nuclei (P < 0.01), reduced cytotrophoblast nuclei (P < 0.01), thickened basal lamina (P < 0.01), and increased stromal deposition of collagens and laminin. The amount of proliferating cytotrophoblast was reduced in the IUGR group (P < 0.014) and the degree of capillary erythrocyte congestion within terminal villous capillaries was increased (P < 0.001). Several of the structural differences in the terminal villi of the IUGR group such as reduced cytotrophoblast proliferation and stromal fibrosis are incompatible with the prevailing view of placental hypoxia in IUGR. Rather thickening of the basal lamina and congestion of the capillaries by erythrocytes are predicted to limit oxygen transfer from the intervillous space to the fetus and may represent an equilibration of oxygen tension between intervillous space and the terminal villi. Despite the known reduction in uteroplacental blood flow in IUGR, fetoplacental blood flow is compromised to a far greater extent in the presence of AEDFV such that maternal blood leaving the placenta has a higher oxygen content than under normal circumstances.

Urease-mediated destruction of bacteria is specific for Helicobacter urease and results in total cellular disruption.

The survival of Helicobacter mustelae, Proteus mirobilis, Escherichia coli and Campylobacter jejuni in the presence of urea and citrate at pH 6.0 was examined. H. mustelae, which has urease activity similar to H. pylori, had a markedly reduced survival, median 2.5% (0-78%) (P < 0.001) when incubated under these conditions. Only 7% of the ammonia produced by H. mustelae urease activity was recovered from the buffer, a similar percentage to that previously reported with H. pylori. None of the other organisms, all of which had lower urease activity, had impaired survival under these conditions. Electron microscopical studies demonstrated extensive structural damage to H. pylori following exposure to urea and citrate at pH 6.0. This structural damage to the organisms makes it unlikely that the low recovery of ammonia was due to retention of ammonia within the bacteria and suggests that the ammonia may have been incorporated into glutamate or other amino acids. Incorporation of ammonia into these compounds would deplete the cell of the key metabolic intermediate alpha-ketoglutarate and could thus explain the mechanism of the urease-dependent destruction of the organism.

Comparative efficiency of flagging and carbon dioxide-baited sticky traps for collecting the lone star tick, Amblyomma americanum (Acarina: Ixodidae).

Collections of Amblyomma americanum (L.) from five habitat types showed that significantly more ticks of all life stages could be collected by CO2-baited sticky traps than by the standard flagging technique. The effect of habitat type and season significantly influenced the number of ticks collected by both techniques. Traps baited with carbon dioxide revealed adult tick activity in several habitats several weeks earlier than did flagging, because flagging failed to efficiently recover ticks unless they had ascended vegetation. The CO2-baited traps required less time and effort and showed less variation for tick population surveys when compared with flagging.

Effect of ivermectin on the volume of blood ingested by two species of ticks (Acari: Ixodidae) feeding on cattle.

Females of the lone star tick, Amblyomma americanum (L.), and the American dog tick, Dermacentor variabilis (Say), were fed on ivermectin (Ivomec)-treated and untreated bovines to determine the effect of the acaricide on volume of blood ingested and to compare the weight differences between the treatment and control groups at various time intervals after attachment. Adult females from each genus were collected from Bos tarus hosts and subjected to hematin assays on three collection dates to estimate the volume of blood ingested. Before feeding, lone star ticks contained an average of 2.0 microliters of blood and had an average weight of 5.2 mg. Unengorged American dog tick females had an average blood volume of 3.3 microliters and a mean weight of 5.8 mg. Ticks of both species reacted to ivermectin by expressing lower mean weights, and they consumed smaller quantities of blood. Lone star tick females were significantly affected in terms of amount of blood consumed and body weight changes when compared with control ticks. After feeding on treated cattle, lone star tick females contained smaller quantities of blood than pretreatment females, but there were no significant differences observed until day 12 between the control and the treated groups. American dog tick females on treated hosts had measurable quantities of blood that were significantly different among the experimental groups.

Persistence of Anaplasma marginale (Rickettsiales: Anaplasmataceae) in male Dermacentor andersoni (Acari: Ixodidae) transferred successively from infected to susceptible calves.

The persistence of Anaplasma marginale Theiler in male Dermacentor andersoni Stiles ticks exposed to the organism as adults was studied as the ticks were successively transferred to five susceptible calves. All calves fed upon by these ticks rapidly developed clinical anaplasmosis; incubation periods of infection ranged from 19 to 26 d and did not change significantly with successive feedings. Development of A. marginale in tick midgut and salivary glands was followed daily during tick feeding (total, 35 d) with light microscopy and DNA hybridization. With microscopy, A. marginale colonies persisted in midgut cells throughout the experiment. Large colonies were observed in gut muscle cells on days 8 through 35 and were the predominant infected cell type during this part of feeding. Colonies were seen in salivary gland acini from day 2 throughout the 35-d experiment. The DNA probe confirmed the presence of Anaplasma DNA in midgut and salivary glands throughout the experiment. Quantitative estimates of infection intensity in tissues of individual ticks approximated 10(7) initial body equivalents, confirming heavy infections. A marginale in midgut tissues decreased with feeding time, whereas the estimated number of organisms in salivary glands remained constant. These data demonstrate that D. andersoni males are efficient vectors of A. marginale and may be potential reservoirs of infection for ruminants for extended periods.

Systemic activity of a benzimidazoline compound in cattle against ticks and biting flies.

A benzimidazoline compound [4-nitro-2-(1,1,2,2-tetrafluoroethyl)-6 -(trifluoromethyl)-1H-benzimidazol-2-, 01, sodium salt] referred to as EL-979 showed systemic acaricidal and insecticidal activity in cattle against 2 tick species, Amblyomma maculatum (Gulf Coast tick) and Dermacentor variabilis (American Dog tick) and adult Stomoxys calcitrans (stable flies). Larvae of black blow fly (Phormia regina) were fed serum collected from treated calves. A complete kill of larvae was obtained with a serum level of 3 parts per million (p.p.m.) of EL-979. Intravenous infusion at the rate of 0.25 mg kg-1 per day for 12 days provided a concentration of EL-979 in the blood of approximately 5 p.p.m. In A. maculatum this blood level prevented feeding in larvae and molting in nymphs, reduced numbers of females successfully feeding and prevented larvae production. D. variabilis adults were not as susceptible to a blood level of 5 p.p.m., but the number of feeding larvae and molting nymphs were reduced. Complete mortality of adult S. calcitrans occurred with repeated feedings of a 5 p.p.m. blood level. Fly control of 80% was found with 2.3 p.p.m. multiple feeds. Calf sera with a concentration range of 16--20 p.p.m. killed all flies which took a single feeding.

Effect of simulated rain, coat length and exposure to natural climatic conditions on the efficacy of a topical formulation of eprinomectin against endoparasites of cattle.

A series of five controlled studies involving 114 cattle were conducted in Australia, North America and the United Kingdom to examine the effect of simulated rain, coat length and exposure to natural climatic conditions, on the efficacy of a topical formulation of eprinomectin against nematode parasites of cattle. In all trials infections were induced with a range of bovine nematode species and treatment was applied when the majority of nematodes were mature. In one study, simulated rain was applied to cattle ending one hour before treatment or beginning one, three or six hours after treatment. In a second study cattle had short (1 cm) or long (3-6 cm) haircoats at the time of treatment. Three other studies were conducted using cattle housed indoors or exposed to various natural climatic conditions. Nematode counts were determined using standard techniques and the efficacy of treatment was assessed relative to vehicle-treated controls. Regardless of the timing of simulated rain relative to treatment, eprinomectin was at least 99.9% effective (P < 0.01) against Haemonchus placei, Ostertagia ostertagi. Trichostrongylus axei and Cooperia spp. There were also no differences (p > 0.10) in efficacy between treatment administered to dry or wet cattle, or treatment administered before or after simulated rainfall. Efficacies against O. ostertagi, T. axei, Cooperia ancophora and Dictyocaulus viviparus were > 99.5% (p < 0.01) regardless of the length of the haircoat at the application site. Exposure of treated cattle to sunshine and precipitation had no effect on anthelmintic efficacy (p > 0.10) with efficacies of greater than 99.5% being maintained against H. placei, O. ostertagi (adult and fourth-stage larvae), T. axei, Cooperia spp., Nematodirus helvetianus (adult and inhibited fourth-stage larvae) and Oesophagostomum radiatum. These findings indicate that eprinomectin (500 micrograms/kg) in a topical formulation is a safe and highly effective nematocide for cattle regardless of their coat length and this high level of efficacy is maintained in cattle exposed to a wide variety of climatic conditions.

Eprinomectin: a novel avermectin for control of lice in all classes of cattle.

Eight trials were conducted in the United States to determine the efficacy of eprinomectin applied topically against four common species of lice in cattle. In two dose titration trials, eprinomectin dosages of 125 to 750 mcg/kg body weight applied topically were compared to untreated controls. In dose confirmation studies, animals treated topically with eprinomectin applied at the rate of 500 mcg/kg were compared to vehicle-treated controls. Four species of lice were present in these trials: Linognathus vituli, Haematopinus eurysternus, Solenopotes capillatus, all sucking lice, and Damalinia (Bovicola) bovis, the cattle biting louse. Louse counts were made on six to nine predilection sites (the same number of sites in all animals in the same trial) prior to treatment. The same sites were counted again seven days after treatment and weekly thereafter until trial termination eight weeks after treatment. When no lice were found in the predilection sites, a modified whole body search was conducted. Each species of lice was present on at least six animals in each treatment group on at least one counting date in two or more trials. No lice were found on any animal treated topically with eprinomectin at a dosage of > or = 500 mcg/kg after 14 days posttreatment until termination of the trials eight weeks after treatment.

Efficacy of selamectin against experimentally induced tick (Rhipicephalus sanguineus and Dermacentor variabilis) infestations on dogs.

Seven controlled studies were conducted to investigate the efficacy of selamectin against weekly infestations of dogs with Rhipicephalus sanguineus and Dermacentor variabilis. Treatments (selamectin or vehicle alone) were applied topically at weekly, 2-week, or monthly intervals or in a "Monthly Plus" regimen (monthly treatment with an additional treatment at 14 days after the first treatment). Selamectin was supplied in unit dose tubes designed to deliver a minimum dosage of 6mgkg(-1). The studies ranged in duration from 37 to 90 days. Fifty adult ticks (+/-2) were applied approximately weekly, and tick counts were performed 3, 4, and 5 days after each infestation. The efficacy of selamectin was expressed as the percentage reduction in geometric mean tick counts on selamectin-treated dogs compared with those for dogs treated with the vehicle alone (negative-control). In one study, the engorgement of Dermacentor variabilis was assessed by weighing ticks after removal on the fifth day after each infestation. Weekly and 2-week interval treatments with selamectin provided efficacies against R. sanguineus of >89% across the entire study periods, with 100% efficacy being achieved from 21 days after the first dose and thereafter (study duration, 37 days for the weekly regimen and 44 days for the 2-week interval regimen). D. variabilis also was well controlled by the 2-week interval treatment regimen, with >96% efficacy being achieved from 21 days after the first treatment and thereafter until the end of the study (study duration: 90 days). In five of six studies incorporating three treatments at monthly intervals, the percentage reduction in R. sanguineus and D. variabilis counts 5 days after infestation ranged from 90 to 100% in the second and third months after treatment began. In the sixth study, reductions of > or =95% in D. variabilis counts 5 days after infestation were achieved for 2 weeks after each treatment in the second and third months. For the Monthly Plus regimen, from the second treatment (day 14) onwards, selamectin achieved 83-100% reductions in R. sanguineus and D. variabilis counts 3 days after infestation, and 94-100% reductions 5 days after infestation in three of the four studies. In the fourth study, selamectin demonstrated good efficacy against D. variabilis for 2 weeks after each treatment. In all seven studies, the counts from the selamectin-treated dogs were significantly (P< or =0.018) lower than those from the vehicle-treated dogs on 77 of the 80 assessments made 5 days after infestation. Selamectin also significantly (P< or =0.0105) reduced engorgement of female D. variabilis. These studies demonstrated that selamectin, administered topically to the skin in a single spot at a minimum dosage of 6mgkg(-1) at monthly intervals, was effective in the control of experimentally induced R. sanguineus and D. variabilis infestations on dogs.