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PubMed2005

Air pollution and birth weight among term infants in California.

OBJECTIVE: To examine associations between birth weight and air pollution among full-term infants in California. METHODS: We matched exposure data collected from air pollution monitors for small particles (PM(2.5)) and carbon monoxide (CO) to California birth records for singleton births delivered at 40 weeks' gestation in 2000 using the locations of the monitors and mother's residence. Pollution measurements collected within 5 miles of the mother's residence, averaged for the time period corresponding to the duration of pregnancy and each trimester, were used as exposure variables. Logistic and linear regression models were used to estimate the associations between the pollution measures and 2 pregnancy outcomes: small for gestational age (SGA) and birth weight. Variations of the models were used to examine the robustness of the findings. RESULTS: The adjusted odds ratio for SGA for exposure in the highest compared with lowest quartile of PM(2.5) was 1.26 (95% confidence interval [CI]: 1.03-1.50). We found no association between CO and birth weight or SGA after controlling for maternal factors and PM(2.5) (mean birth weight difference: 2.6 g; 95% CI: -20.6 to 25.8). The difference in mean birth weight for infants with a 9-month exposure in the highest quartile of PM(2.5) compared with that of infants who were exposed in the lowest quartile was -36.1 g (95% CI: -16.5 g to -55.8 g); this difference was similar after controlling for CO. We did not find PM(2.5) exposure during a particular trimester most important for assessing birth weight; trimester-level associations were similar to those found using the 9-month exposure variable. CONCLUSIONS: We found an increased odds of SGA and a small difference in mean birth weight between infants with the highest and lowest exposures to PM(2.5) but not CO. These findings have important implications for infant health because of the ubiquitous exposure to fine particulate air pollution across the United States.

Air Pollutants↗
PubMed2006

Costs of newborn care in California: a population-based study.

OBJECTIVE: We sought to describe the current costs of newborn care by using population-based data, which includes linked vital statistics and hospital records for both mothers and infants. These data allow costs to be reported by episode of care (birth), instead of by hospitalization. METHODS: Data for this study were obtained from the linked 2000 California birth cohort data. These data (n = 518,704), provided by the California Office of Statewide Health Planning and Development (OSHPD), contain infant vital statistics data (birth and death certificate data) linked to infant and maternal hospital discharge summaries. In addition to the infant and maternal hospital discharge summaries associated with delivery, these data include discharge summaries for all infant hospital-to-hospital transfers and maternal prenatal hospitalizations. The linkage algorithm that is used by OSHPD in creating the linked cohort data file is highly accurate. More than 99% of the maternal and infant discharge abstracts were linked successfully with the birth certificates. These data were also linked successfully with the infant discharge abstracts from the receiving hospital for 99% of the infants who were transferred to another hospital. The hospital discharge records were the source of the hospital charges and length-of-stay information summarized in this study. Hospital costs were estimated by adjusting charges by hospital-specific ratios of costs to charges obtained from the OSHPD Hospital Financial Reporting data. Costs, lengths of stay, and mortality were summarized by birth weight groups, gestational age, cost categories, and types of admissions. RESULTS: Low birth weight (LBW) and very low birth weight (VLBW) infants had significantly longer hospital stays and accounted for a significantly higher proportion of total hospital costs. The average hospital stay for LBW infants ranged from 6.2 to 68.1 days, whereas the average hospital stay for infants who weighed >2500 g at birth was 2.3 days. Overall, VLBW infants accounted for 0.9% of cases but 35.7% of costs, whereas LBW infants accounted for 5.9% of cases but 56.6% of total hospital costs. Although total maternal and infant costs were similar (approximately 1.6 billion dollars), the distribution of maternal costs was much less skewed. For infants, 5% of infants accounted for 76% of total infant hospital costs. Conversely, the most expensive 3% of deliveries accounted for only 17% of total maternal costs. CONCLUSIONS: The very smallest infants make up a hugely disproportionate share of costs; more than half of all neonatal costs are incurred by LBW or premature infants. Maternal costs are similar in magnitude to newborn costs, but they are much less skewed than for infants. Preventing premature deliveries could yield very large cost savings, in addition to saving lives.

California↗
PubMed2006

Prospective evaluation of postnatal steroid administration: a 1-year experience from the California Perinatal Quality Care Collaborative.

OBJECTIVE: Postnatal steroids (PNSs) are used frequently to prevent or treat chronic lung disease (CLD) in the very low birth weight (VLBW) infant, and their use continues despite concerns regarding an increased incidence of longer-term neurodevelopmental abnormalities in such infants. More recently, there has been a suggestion that corticosteroids may be a useful alternative therapy for hypotension in VLBW infants, but there have been no prospective reports of such use for a current cohort of VLBW infants. METHODS: The California Perinatal Quality Care Collaborative (CPQCC) requested members to supplement their routine Vermont Oxford Network data collection with additional information on any VLBW infant treated during their hospital course with PNS, for any indication. The indication, actual agent used, total initial daily dose, age at treatment, type of respiratory support, mean airway pressure, fraction of inspired oxygen, and duration of first dosing were recorded. RESULTS: From April 2002 to March 2003 in California, 22 of the 62 CPQCC hospitals reported supplemental data, if applicable, from a cohort of 1401 VLBW infants (expanded data group [EDG]), representing 33.2% of the VLBW infants registered with the CPQCC during the 12-month period. PNSs for CLD were administered to 8.2% of all VLBW infants in 2003, 8.6% of infants in the 42 hospitals that did not submit supplemental data (routine data-set group, compared with 7.6% in EDG hospitals). Of the 1401 VLBW infants in the EDG, 19.3% received PNSs; 3.6% received PNSs for only CLD, 11.8% for only non-CLD indications, and 4.0% for both indications. At all birth weight categories, non-CLD use was significantly greater than CLD use. The most common non-CLD indication was hypotension, followed by extubation stridor, for which 36 (16.3%) infants were treated. For hypotension, medications used were hydrocortisone followed by dexamethasone. Infants treated with PNSs exclusively for hypotension had a significantly higher incidence of intraventricular hemorrhage, periventricular leukomalacia, and death when compared with infants treated only for CLD or those who did not receive PNSs. CONCLUSIONS: The common early use of hydrocortisone for hypotension and the high morbidity and mortality in children receiving such treatment has not been recognized previously and prospective trials evaluating the short- and long-term risk/benefit of such treatment are urgently required.

Administration, Inhalation↗
PubMed2006

Economic evaluation of tandem mass spectrometry screening in California.

OBJECTIVE: On the basis of California's experience implementing a pilot tandem mass spectrometry (MS/MS) screening program, an economic evaluation was conducted to determine the economic benefits and costs of a statewide MS/MS screening program. METHODS: Cost-effectiveness, benefit/cost, and cost-utility analyses were conducted with a base-case set of assumptions. The base-case assumptions were varied by using a set of more-favorable and less-favorable assumptions to test the robustness of the analysis findings. RESULTS: The total estimated, annualized, incremental costs of MS/MS screening of 540,000 births in California were nearly $5.7 million; 83 affected newborns would be identified. Screening would reduce the expected lifetime costs of medical care for affected newborns by $7.2 million ($9.0 million in the best-case scenario and $1.8 million in the worst-case scenario). When all program costs and savings were considered, screening saved $1.5 million ($3.4 million saved in the best-case scenario and $3.8 million additional costs in the worst-case scenario). With only incremental program costs, the cost per life saved was $708,000 and the cost per case detected was $68,000. With consideration of the projected lifetime medical care costs, the total cost per case detected was $132,000. MS/MS screening produced a benefit/cost ratio of $9.32 ($11.67 with the best-case set of assumptions and $4.34 with the worst-case set of assumptions). In this analysis, the benefits of screening exceeded total program costs by $47.1 million (the net incremental benefit). In the worst-case scenario, the net incremental benefit of screening was $18.9 million. Screening saved 949 quality-adjusted life-years (QALYs) and saved $1628 per QALY in the base case analysis. Under the worst-case scenario, the cost per QALY was $14,922. CONCLUSIONS: We found that the benefits of MS/MS screening outweighed the costs and that the net benefits were significant and robust in various scenarios with various conservative underlying assumptions.

California↗
PubMed1996

Asthma exacerbations during Santa Ana winds in southern California.

This study investigated the relationship between Santa Ana wind conditions and visits for asthma at a southern California emergency department. Visits to the emergency department for asthma were analyzed retrospectively to determine whether the incidence increased during Santa Ana wind conditions. These northeasterly winds are common during fall and winter in southern California and belong to a class known as Foehn winds. They are characterized by gusty winds, decreased relative humidity, warm temperatures, and decreased levels of airborne pollutants. During a 4-year period, we noted that emergency department visits for asthma increased (3.12 vs. 2.16 visits per day, P < 0.0001) during SantaAna winds compared with other weather conditions. Asthmatics presenting during Santa Ana winds appeared to be more ill, as judged by higher admission rates (21.9 vs. 18.7%, P < 0.05). These winds were also associated with reduced particulate matter (PM10) counts (P < 0.0001). Although the magnitude of the increase in emergency department visits was small, it occurred at a time when typical inciters of respiratory disease should be minimal. An as yet unidentified factor associated with these winds may be a stimulant for some asthmatics. Similar wind patterns in other localities might affect respiratory disease as well.

Air Pollutants↗
PubMed2000

Assessment of insecticide resistance after the outbreak of diamondback moth (Lepidoptera: Plutellidae) in California in 1997.

During an outbreak of the diamondback moth, Plutella xylostella (L.), in California in 1997, nine populations were collected from the major broccoli areas throughout the state. Populations were assayed for their susceptibility to currently used materials (Bacillus thuringiensis subsp. kurstaki, permethrin, and methomyl) and to newer materials that had not yet been commercially used in California (spinosad, emamectin benzoate, and chlorfenapyr). For the currently used insecticides, elevated levels of resistance were seen only with permethrin and seven of the nine populations had tolerance ratios (TR) of > 100. With the newer chemistries, TR values were all < 15. To compare potential cross-tolerance, TR values of the currently used insecticides were compared with TR values of the newer insecticides. There were significant relationships found between: methomyl and emamectin benzoate, methomyl and spinosad, and permethrin and spinosad. Further biochemical studies are needed to confirm the actual mechanisms that lead to these relationships and field tests are needed to determine what impact, if any, such TR levels would have on control in the field. These data indicate that resistance to at least one of the commonly used insecticides (permethrin) may have played a role in the outbreak during 1997. However, other factors may have been at least equally important. The winter of 1996-1997 was warmer than normal, and during the period from February through August of 1997 the amount of rainfall was < 50% of normal. Hot and dry conditions are known to be conducive to outbreaks of P. xylostella. These data add to an overall knowledge about the geographic variation of resistance in P. xylostella populations within the United States. They also serve as a baseline for monitoring changes in susceptibility to these newer insecticides and can also help explain the occurrence of outbreaks caused by factors other than insecticide resistance.

Animals↗
PubMed2001

Potential for outbreaks of leafrollers (Lepidoptera: Tortricidae) in California apple orchards using mating disruption for codling moth suppression.

Two species of leafrollers, Argyrotaenia citrana (Fernald) and Pandemis pyrusana Kearfott, represent serious obstacles to the implementation of mating disruption for control of codling moth in coastal California apple orchards. Larval and adult densities of A. citrana and P. pyrusana and subsequent fruit damage were compared under different codling moth control treatments. Leafroller larval counts and levels of fruit damage were significantly higher in most plots that were untreated or treated only with codling moth pheromone. Leafroller fruit damage levels in these plots were commonly between 10 and 15% at harvest. As summer larval counts were good predictors of fruit damage levels, larval sampling could be a useful tool for predicting leafroller outbreaks. Use of pheromone trapping for A. citrana to detect localized outbreaks within an orchard was not useful and failed to correlate with larval numbers, whereas adult monitoring for P. pyrusana appears more promising. Efforts to implement a codling moth mating-disruption program in California must include changes in strategies for monitoring and controlling leafroller species.

Animals↗
PubMed2000

Patterns of avian seroprevalence to western equine encephalomyelitis and Saint Louis encephalitis viruses in California, USA.

Temporal and spatial changes in the enzootic activity of western equine encephalomyelitis (WEE) and St. Louis encephalitis (SLE) viruses were monitored at representative wetland study sites in the Coachella, San Joaquin, and Sacramento valleys of California from 1996 to 1998 using three methods: (1) virus isolation from pools of 50 host-seeking Culex tarsalis Coquillett females, (2) seroconversions in flocks of 10 sentinel chickens, and (3) seroprevalence in wild birds collected by mist nets and grain baited traps. Overall, 74 WEE and one SLE isolates were obtained from 222,455 Cx. tarsalis females tested in 4,988 pools. In addition, 133 and 40 seroconversions were detected in 28 chicken flocks, and 143 and 27 of 20,192 sera tested from 149 species of wild birds were positive for antibodies to WEE and SLE, respectively. WEE was active in all three valleys, whereas SLE only was detected in Coachella Valley. Seroconversions in sentinel chickens provided the most sensitive indication of enzootic activity and were correlated with seroprevalence rates in wild birds. Avian seroprevalence rates did not provide an early warning of pending enzootic activity in chickens, because positive sera from after hatching year birds collected during spring most probably were the result of infections acquired during the previous season. Few seroconversions were detected among banded recaptured birds collected during spring and early summer. Age and resident status, but not sex, were significant risk factors for wild bird infection, with the highest seroprevalence rates among after hatching year individuals of permanent resident species. Migrants (with the exception of mourning doves) and winter resident species rarely were positive. House finches, house sparrows, Gambel's quail, California quail, common ground doves, and mourning doves were most frequently positive for antibodies. The initial detection of enzootic activity each summer coincided closely with the appearance of hatching year birds of these species in our study areas, perhaps indicating their role in virus amplification. Bird species most frequently positive roosted or nested in elevated upland vegetation, sites where Cx. tarsalis host-seeking females hunt most frequently. These serosurveys provided important background information for planned host competence and chronic infection studies.

Animals↗
PubMed2002

Laboratory evaluation of fipronil and imidacloprid topical insecticides for control of the plague vector Oropsylla montana (Siphonaptera: Ceratophyllidae) on california ground squirrels (Rodentia: Sciuridae).

Two insecticides, fipronil and imidacloprid, were evaluated for efficacy and longevity against Oropsylla montana (Baker), the most important vector of plague in California. Wild-caught California ground squirrels, Spermophilus beecheyi (Richardson), were individually housed in the laboratory to serve as natural hosts to O. montana and for on-animal insecticide trials. Several concentrations oftechnical grade fipronil and imidacloprid in acetone were applied to samples of clean rodent bedding to determine residual activity and longevity against fleas. Immature and adult cat fleas, Ctenocephalides felis (Bouche), were used as representative fleas for periodic assays in place of less fecund O. montana. Toxicity of treated bedding did not decrease significantly for 1 yr at all applied concentrations. Fipronil provided 100% kill for at least 1 yr at > or = 100 ppm, whereas imidacloprid required 10,000 ppm for similar performance. Laboratory squirrels were treated with topical formulations of fipronil (Frontline Top Spot) and imidacloprid (Advantage Flea Adulticide) at a dosage rate of 15 mg/kg and evaluated for residual activity every 2 wk against adult O. montana. Residual activity was determined by percent recovery of O. montana adults released on treated and untreated animals after 48 h. Frontline provided 100% kill of adult fleas for at least 10 wk, and up to 26 wk on one animal. Advantage failed to provide 100% kill of adult fleas at 2 wk, with complete loss of efficacy by week 6. Concurrent assays with bedding samples from squirrel nest boxes showed negligible toxicity transfer from treated animals to nest bedding.

Animals↗
PubMed2003

Experimental infection of California birds with western equine encephalomyelitis and St. Louis encephalitis viruses.

A total of 27 bird species from the San Joaquin and Coachella valleys of California were inoculated subcutaneously with sympatric strains of western equine encephalomyelitis (WEE) and St. Louis encephalitis (SLE) viruses. Overall, 133 of 164 birds inoculated with WEE virus developed a viremia detected by plaque assay; significantly greater than 72 of 163 birds inoculated with SLE virus. Host competence was calculated as the average number of days that each avian species had a viremia > or = 2 log10 plaque-forming units per 0.1 ml, the threshold for infecting susceptible Culex tarsalis Coquillett, the primary vector of these viruses in California. Eleven of 20 species inoculated with WEE virus had a value > or = 1 and were considered to be competent hosts, whereas only six of 22 species inoculated with SLE virus had a value > or = 1. Overall, 133 of 164 birds inoculated with WEE virus and 105 of 163 inoculated with SLE virus produced antibody detectable by enzyme immunoassay and/or plaque reduction neutralization test. Six birds infected with WEE virus (one house finch, three mourning doves, one Brewer's sparrow, and one white-crowned sparrow) and nine birds infected with SLE virus (two house finches, three white-crowned sparrows, one song sparrow, two Western scrub-jays, and one orange crowned warbler) contained viral RNA detected by reverse transcription-polymerase chain reaction at necropsy > 6 wk postinoculation; infectious WEE and SLE viruses were only recovered from three mourning doves and an orange-crowned warbler, respectively, after blind passage in mosquito cells. Our study indicated that birds with elevated field antibody prevalence rates may not be the most competent hosts for encephalitis viruses and that relatively few birds developed chronic infections that could be important in virus persistence and dispersal.

Animals↗
PubMed2004

The occurrence and distribution of Salmonella enteritidis and other serovars on California egg laying premises: a comparison of two sampling methods and two culturing techniques.

Between the summer of 1998 and the winter of 2000, Salmonella analysis was performed on 2128 single and 532 pooled manure drag swabs obtained from 133 California commercial egg laying farms. The isolation of Salmonella from all rows and from all flocks using single or pooled swabs was 80% and 92%, respectively. Hence, there was no statistical difference between single vs. pooled swabs in terms of identifying Salmonella on a row or flock basis. A total of 14 serogroups comprising 44 serotypes were isolated from 123 of 133 farms. When the top 10 serotypes were considered, there was no significant difference in the range of serotypes isolated by the two culturing methods. The overall S. enteritidis prevalence for California flocks was 10.5% (14/133). The overall row prevalence for S. enteritidis for all the farms was 1.1% (24/2128), and the overall pool prevalence was 2.4% (13/532). Sixty percent (12/20) of the S. enteritidis isolates from the positive farms were phage type 4, and 40% (8/20) represented five other phage types (1, 6B, 7, 8, and 28).

Animals↗
PubMed2001

Birds and their ticks in northwestern California: minimal contribution to Borrelia burgdorferi enzootiology.

Birds and their attendant ticks were surveyed for infection with the Lyme disease spirochete Borrelia burgdorferi, in chaparral and woodland-grass habitats in northwestern California from March to July, 1998 to 1999. In total, 234 birds were captured and recaptured (15%); nearly 2.5 times more birds were captured in chaparral than in woodland-grass. Overall, 34 species representing 15 families were collected during this study; of these, 24 species were caught in chaparral, 19 in woodland-grass, and 9 in both vegetational types. The most frequently captured birds were sage sparrows (Amphispiza belli) in chaparral, and American robins (Turdus migratorius) and oak titmice (Baelophus inornatus) in woodland-grass. Birds hosted 35 Ixodes pacificus (15 larvae, 20 nymphs) and 9 Haemaphysalis leporispalustris (3 larvae, 5 nymphs, 1 adult) ticks, of which 32 were removed from chaparral birds and 12 from woodland birds. The prevalence of tick infestation was 13% (21/167) in chaparral and 5% (3/67) in woodland-grass, but the relative and mean tick intensities of 0.19 and 1.5 for chaparral birds, and 0.18 and 4.0 for woodland birds, respectively, did not differ significantly by habitat. Spirochetes were not detected in either bird-blood or tick-tissue samples when tested by culture, immunofluorescence, or Giemsa-staining. In contrast, over 90% (86/94) of western fence lizards (Sceloporus occidentalis) collected in June or July were infested with an average of 6.9 and 8.9 immature I. pacificus in chaparral and woodland-grass, respectively. We conclude that birds contribute little to the enzootiology of B. burgdorferi in chaparral and woodland-grass habitats in northwestern California because of their limited parasitism by tick vectors and lack of detectable spirochetemias.

Animals↗
PubMed2001

Prevalence and abundance of Ixodes pacificus immatures (Acari: Ixodidae) infesting western fence lizards (Sceloporus occidentalis) in northern California: temporal trends and environmental correlates.

The prevalence and abundance of immature Ixodes pacificus ticks on western fence lizards (Sceloporus occidentalis) were examined in relation to time of year, host attributes (i.e., age, gender, and presence or absence of blood parasites), and 5 environmental characteristics, including topographic exposure and ground cover substrate, over a 2-year period in northern California. Lizards were infested with subadult ticks from early March until late July or early August, with peak median numbers of larvae and nymphs recorded in late April and early May of both years. Peak larval and nymphal abundances differed between years. The overall ratio of larvae to nymphs on adult male lizards was low, ranging from 0.80 in 1999 to 2.41 in 2000. Such intensive feeding of nymphs versus larvae on these lizards, which are reservoir-incompetent for Borrelia burgdorferi spirochetes, may explain previous observations of decreasing spirochetal infection prevalence from the nymphal to adult stage in northwestern California. Adult male lizards were more likely to be infested with nymphs and harbored greater abundances of larvae and nymphs than adult females. Lizards uninfected with blood parasites had more nymphs than infected lizards. The measured environmental characteristics could explain only a small percentage of the total variation observed in larval prevalence (22%) and in larval and nymphal abundance (12 and 3%, respectively).

Animals↗
PubMed2004

Risk of transplacental transmission of Sarcocystis neurona and Neospora hughesi in California horses.

The study objective was to assess the risk of transplacental transmission of Sarcocystis neurona and Neospora hughesi in foals from 4 California farms during 3 foaling seasons. Serum of presuckle foals and serum and colostrum of periparturient mares were tested using indirect fluorescent antibody tests for S. neurona and N. hughesi. Serum antibody titers were < or =10 in 366 presuckle foals tested. There was no serologic or histologic evidence of either parasite in aborted fetuses or placentas examined. Positivity for S. neurona and N. hughesi in mares increased with age. Mares < or =9 yr that originated from Kentucky were 3.8 and 1.4 times more likely to be positive for S. neurona and N. hughesi, respectively, than mares from California. The strength of association between positivity to either parasite and state of birth decreased as age increased. Mares positive for S. neurona and N. hughesi were 2.2 and 1.7 times more likely, respectively, to have a previous abortion than negative mares, adjusted for age and state of birth. The annual mortality rate for mares was 4%. The annual incidence rate of equine protozoal myeloencephalitis was 0.2%. In conclusion, there was no detectable risk of transplacental transmission of S. neurona and N. hughesi. Prevalence of antibodies against both parasites in mares increased with age.

Abortion, Veterinary↗
PubMed2006

Ecological factors limiting the distribution of Gilia tricolor in a California grassland mosaic.

Recent evolutionary models of range limits emphasize the importance of ecological and demographic factors operating at species' margins. This study aims to establish the ecological context driving population boundaries in Gilia tricolor, a native California annual restricted to distinct habitat patches in the coastal range of California. A transplant experiment in one hillside G. tricolor population examined the roles of competition and soil chemistry as well as litter and biomass accumulation in setting local population boundaries. Results indicate that boundaries are maintained primarily by inhibition of seedling emergence by vegetation and litter, and that upslope and downslope population boundaries are heterogeneous in litter biomass and transplant performance. Consistent emergence inhibition in undisturbed, peripheral sites maintains limits to the distribution of G. tricolor in this population. Fine-scaled ecological heterogeneity and heterogeneous boundary conditions likely play important roles in limiting adaptation and subsequent range expansion at population boundaries in G. tricolor.

Biomass↗
PubMed2006

Human impacts, plant invasion, and imperiled plant species in California.

Invasive species are one of the fastest growing conservation problems. These species homogenize the world's flora and fauna, threaten rare and endemic species, and impose large economic costs. Here, we examine the distribution of 834 of the more than 1000 exotic plant taxa that have become established in California, USA. Total species richness increases with net primary productivity; however, the exotic flora is richest in low-lying coastal sites that harbor large numbers of imperiled species, while native diversity is highest in areas with high mean elevation. Weedy and invasive exotics are more tightly linked to the distribution of imperiled species than the overall pool of exotic species. Structural equation modeling suggests that while human activities, such as urbanization and agriculture, facilitate the initial invasion by exotic plants, exotics spread ahead of the front of human development into areas with high numbers of threatened native plants. The range sizes of exotic taxa are an order of magnitude smaller than for comparable native taxa. The current small range size of exotic species implies that California has a significant "invasion debt" that will be paid as exotic plants expand their range and spread throughout the state.

California↗
PubMed2006

Simulating the effects of frequent fire on southern California coastal shrublands.

Fire disturbance is a primary agent of change in the mediterranean-climate chaparral shrublands of southern California, USA. However, fire frequency has been steadily increasing in coastal regions due to ignitions at the growing wildland-urban interface. Although chaparral is resilient to a range of fire frequencies, successively short intervals between fires can threaten the persistence of some species, and the effects may differ according to plant functional type. California shrublands support high levels of biological diversity, including many endangered and endemic species. Therefore, it is important to understand the long-term effects of altered fire regimes on these communities. A spatially explicit simulation model of landscape disturbance and succession (LANDIS) was used to predict the effects of frequent fire on the distribution of dominant plant functional types in a study area administered by the National Park Service. Shrubs dependent on fire-cued seed germination were most sensitive to frequent fire and lost substantial cover to other functional types, including drought-deciduous subshrubs that typify coastal sage scrub and nonnative annual grasses. Shrubs that resprout were favored by higher fire frequencies and gained in extent under these treatments. Due to this potential for vegetation change, caution is advised against the widespread use of prescribed fire in the region.

California↗
PubMedDate not supplied

A prospective study of canine infective endocarditis in northern California (1999-2001): emergence of Bartonella as a prevalent etiologic agent.

A prospective study was performed (June 1999 to May 2001) to determine the incidence of infective endocarditis (IE) due to Bartonella in dogs in northern California and to compare these patients with other dogs with IE. IE was diagnosed antemortem based on clinical signs and echocardiography in 18 dogs. The etiologic agent was Bartonella sp. in 5 dogs (28%) and was diagnosed by high seroreactivity to Bartonella (titer > 1:512; range, 1:1,024-1:4,096); and confirmed postmortem by positive polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) from the infected valve and partial DNA sequencing of the citrate synthase gene (glt A). Conventional bacteria were causative agents in 7 dogs (39%). An etiologic agent was not identified in 6 dogs (33%). Bartonella vinsonii berkhoffii (n = 3), B clarridgeiae (n = 1), and a B clarridgeiae-like organism (n = 1) were identified. Blood culture was positive only for the IE case due to B clarridgeiae. All dogs with IE due to Bartonella were also seroreactive to Anaplasma phagocytophilum. All dogs with IE due to Bartonella had lesions only on the aortic valve. Of the cases of IE not due to Bartonella, 31% involved the aortic valve, 61% the mitral valve, and 8% both valves. Dogs with mitral valve IE lived longer than all dogs with aortic valve IE (P = .004) and dogs with IE of the aortic valve due to Bartonella (P = .002). In conclusion, Bartonella is a common cause of IE in dogs of northern California. A high Bartonella serologic titer (> 1:512) is useful antemortem to diagnose aortic valve IE due to Bartonella.

Animals↗