Acceptance of simulated oral rabies vaccine baits by urban raccoons

In summer 1986, a study was conducted to evaluate raccoon (Procyon lotor) acceptance of oral baits that could be used for rabies vaccination. One thousand wax-coated sponge bait cubes were filled with 5 mg of a seromarker (iophenoxic acid), placed in polyethylene bags, and hand-distributed in an 80 ha area within an urban National Park in Washington, D. C. (USA). After 3 wk, target and nontarget animals were trapped and blood samples collected to evaluate bait uptake. Thirty-three of 52 (63%) raccoons had elevated blood iodine levels indicating they had eaten at least one bait, 13 (25%) were negative, and six (12%) had marginal values. These results indicate that sponge baits hand-placed at a density of 12.4/ha can reach a significant proportion of an urban raccoon population. Implications for oral rabies vaccination of raccoons are discussed.     

Trap-vaccinate-release and oral vaccination for rabies control in urban skunks, raccoons and foxes.

Two rabies control tactics, trap-vaccinate-release (T-V-R) and oral vaccination were used for the control of rabies in skunks (Mephitis mephitis), raccoons (Procyon lotor), and foxes (Vulpes vulpes) in metropolitan Toronto, Canada. Using T-V-R, a mean of 45% to 72% (95% confidence limits of 40% to 81%) of the skunks and a mean of 17% to 68% (95% confidence limits of 14% to 76%) of the raccoons in a 60 km2 area of Toronto were vaccinated against rabies between 1987 and 1991. The area has been free of skunk rabies from May 1989 to April 1992. Forty-five rabies cases were diagnosed during 1980 to 1986. In contrast, only three skunk cases have been reported since the vaccination program began in July 1987. The T-V-R area also remained rabies free during an epizootic of skunk rabies in metropolitan Toronto during 1991. Following distribution of rabies vaccine-baits throughout the ravines of metropolitan Toronto, June 1989 to December 1991, 46% to 80% of the Toronto fox population was immunized during 1989, 1990 and 1991. Only one case of fox rabies was reported in metropolitan Toronto since vaccination began, compared to 80 cases reported between 1982 and 1988. The area has been free of reported fox rabies from October 1990 to April 1992.     

Variation in demographic patterns and population structure of raccoons across an urban landscape

Raccoons (Procyon lotor) are considered synanthropic, with high densities reported from urban landscapes. However, little information is available on population density and demography within the urban matrix. To better understand how urban land-use patterns influence raccoon density and demographic patterns, we sampled raccoons at multiple, replicated sites across an urban landscape. Density differed by land-use type (F_2,17 = 4.66, P = 0.027): urbanized sites, = 4.96 ± 2.64 raccoons/km², range = 1.25–10.00 raccoons/km²; urban open sites, = 14.84 ± 6.35 raccoons/km², range = 3.00–29.25 raccoons/km²; rural open sites, = 15.50 ± 4.66 raccoons/km², range = 13.00–20.25. Although we found no clear patterns in sex ratio, reproductive condition, or body condition, we observed differences in age structure among urban open, rural open, and urbanized sites. The most striking difference was the absence of older animals at urbanized sites and relatively low numbers of young individuals at urban open sites. Raccoons were the dominant mesocarnivore in open fragments, but less so in the urban matrix. Spatial variation in density across urban landscapes is likely influenced by site level differences in abundance of anthropogenic resources and differences in habitat quality. Furthermore, the association between changes in land-use and population age structure may have reflected different mortality sources across the landscape. Our results illustrate that wildlife species considered synanthropic may have complex relationships with urban landscapes. © 2012 The Wildlife Society.     

Intramuscular vaccination of skunks and raccoons against rabies

Live-captured striped skunks (Mephitis mephitis) and raccoons (Procyon lotor) were immunized with inactivated rabies vaccine by intramuscular injection and released at the point of capture during a rabies control program in Metropolitan Toronto (Ontario, Canada). Serum samples collected prior to and following vaccination revealed that 100% of the skunks and 98% of the raccoons seroconverted. Rabies antibody was still detectable 314 to 757 days postvaccination. Five of six skunks vaccinated in the laboratory survived challenge with rabies virus 90 days postvaccination. To our knowledge, this is the first documentation of the successful seroconversion of skunks and raccoons vaccinated against rabies in the field.     

Oral efficacy of an attenuated rabies virus vaccine in skunks and raccoons

Raccoons and skunks are major rabies reservoirs in North America. Oral vaccination is one method to consider for disease control in these carnivores. Under field conditions in the USA, only one oral rabies vaccine has been used. It is efficacious in wildlife such as raccoons (Procyon lotor), coyotes (Canis latrans), and foxes (Vulpes vulpes) but not in skunks (Mephitis mephitis). The objectives of this study were to evaluate an attenuated SAG-2 rabies virus vaccine for safety, immunogenicity, and efficacy by the oral route in skunks and raccoons. Two of five skunks and three of five raccoons developed virus neutralizing antibodies (VNA) by day 14 following oral administration of SAG-2 vaccine. All animals remained healthy. Upon challenge, naive controls succumbed to rabies. Among vaccinated animals, four of five skunks and all five raccoons had VNA on day 7 post-challenge and all survived. Given these results, SAG-2 is a promising candidate vaccine that may satisfy both safety and efficacy concerns for oral rabies immunization of major North American rabies reservoirs.     

Oral rabies vaccine contact by raccoons and nontarget species in a field trial in Florida

Rabies is enzootic in raccoons (Procyon lotor) in the eastern United States. Oral vaccination of free-ranging raccoons against rabies has the potential to control the disease in a principal reservoir and reduce the risk of rabies exposure among domestic animals and humans. Free-ranging animal contact with baits containing a vaccinia virus recombinant vaccine expressing the rabies glycoprotein gene (V-RG) was monitored in Pinellas County (Florida, USA) from February through May 1997. Bait contact was assessed with 423 tracking plate nights; conducted in four land use zones: single residential, multiple residential, industrial-commercial, and undeveloped. The undeveloped land use zone was further described by six vegetation communities: mangrove swamp, red maple swamp, beach dune, pine forest, mixed oak hammock, and cabbage palm hammock. Seven animal taxa contacted the baited tracking plates across the four land use zones: raccoons, opossums (Didelphis virginiana), cats (Felis catus), dogs (Canis familiaris), rabbits (Sylvilagus sp.), unidentified rodents, and birds. A total of 252/413 (61%) of the baits was contacted by animals; 95 (38%) of these were specifically by the raccoon, the target species. Overall bait contact by all animals was significantly different among the four land use zones, being highest in the undeveloped zone (82%) and lowest in the industrial-commercial zone (34%). Bait contact by raccoons also was significantly different among the undeveloped and pooled urban zones. Among the six vegetation communities, bait contact by all animals was significantly different ranging from 95% in the mangrove to 50% in the cabbage palm hammock. Among the four vegetation communities tested, bait contact by raccoons also was significantly different.     

Immunogenicity and efficacy of two rabies vaccines in wild-caught, captive raccoons

The immunogenicity and efficacy of two rabies vaccines in wild-caught, captive raccoons (Procyon lotor) were investigated. Raccoons were fed Ontario Slim (OS) baits containing a recombinant vaccinia virus-rabies glycoprotein (VRG) oral rabies vaccine, or they were given an intramuscular (IM) injection of IMRAB(?) 3 rabies vaccine. Blood samples collected before treatment and from weeks 1 to 16 posttreatment were assessed for the presence of rabies virus antibody (RVA). There were significantly more positive responders in the group that received an IM injection of IMRAB 3 (18/27) than in the group that consumed VRG in OS baits (VRG-OS; 4/ 26). There were no significant associations among age, sex, and seroconversion. Of those animals that mounted a humoral immune response to vaccination, RVA was first detected between weeks 1 and 5, with the majority of initial seroconversions detectable at week 2. A subsample of 50 raccoons (19 VRG-OS, 18 IMRAB 3, and 13 controls) from the longitudinal serology study was challenged with live raccoon variant rabies virus 442 days after initial treatment. There were significantly more survivors in the group that received IMRAB 3 (13/18) than in the VRG-OS (5/19) or control (2/13) groups. All 15 raccoons that demonstrated a serologic response survived challenge regardless of treatment. Of the 35 raccoons with no detectable serologic response, 30 (86%) succumbed to rabies virus infection (14/15 VRG-OS, 5/7 IMRAB 3, and 11/13 controls).     

Raccoon rabies: the re-emergence of an epizootic in a densely populated area

Investigation of sporadic or isolated cases of rabies was encouraged in the 1950s by the implementation of a national surveillance system for reporting of rabies cases. Low level enzootic disease was recognized in several wild species during this period, including a small focus of rabies in raccoons in Florida. Phylogenetic analysis of the virus transmitted by rabid raccoons and reconstruction of the early history of raccoon rabies in the United States suggests that rabies was present in these animals long before its recognition by the public health community and that the emergence of raccoon rabies as a major threat to public health was the result of several natural and human-mediated events. In recent years, reports of raccoon-human contact and rabies in raccoons have increased as changes in human demographics and land development have concentrated raccoon populations in urban and suburban settings. In addition to the natural spread of rabies from Florida to raccoon populations in Georgia, Alabama, South Carolina and North Carolina, a separate focus in the northeastern states is believed to have been caused by the translocation of raccoons from the southeast to Virginia and West Virginia. Oral vaccination of wild species may be an important adjunct to traditional rabies control measures in the management of this disease in the future.     

Frequency dynamics of foxes as a factor of epizootic risk of rabies

During the period preceding the year 1998 when the peak values of the rabies incidence were registered in the Moscow region, a noticeable increase in fox frequency and the density of their population occurred, especially in 3 endemic areas of the north-western zone. Considering the fact that this zone was endemic for rabies, an increased density of the fox population was, most probably, the critical factor of the epizootological risk and the main cause of the emergency situation in rabies in 1998. The data obtained in this investigation may serve as a real basis for the prediction of the epizootic situation.     

The effect of incubation time distribution on the extinction characteristics of a rabies epizootic

The continuous model of Anderson et al. (1981), Nature 289, 765–771, is successful in describing certain characteristics of rabies epizootics, in particular, the secondary recurrences which follow the initial outbreak; however, it also predicts the occurrence of exponentially small minima in the infected population, which would realistically imply extinction of the virus. Here we show that inclusion of a more realistic distribution of incubation times in the model can explain why extinction will not occur, and we give explicit parametric estimates for the minimum infected fox density which will occur in the model, in terms of the incubation time distribution.     

Formulation and evaluation of baits for oral rabies vaccination of raccoons (Procyon lotor)

Captive raccoons were offered a variety of vaccine containers and bait components in a series of three-choice tests. Paraffin wax ampules were the most readily accepted vaccine container. Preferred bait components included corn and shellfish oils, deep fried corn meal batter, and egg, apple and buttermilk flavorings. These results, together with factors including ease of bait formulation, cost, and suitability for field use, were used to develop an experimental delivery system for an oral rabies vaccine. The developed system was composed of a polyurethane sleeve (1.5 x 5.5 cm) dipped in a commercial food batter mix together with corn meal, milk and egg. The sleeve was deep fried in corn oil and a 2.0 ml ampule containing a recombinant rabies vaccine was then inserted into the sleeve bait. These baits were presented to 10 captive raccoons. Nine of the 10 animals developed high levels of rabies virus neutralizing antibodies. Field tests are needed to determine if the delivery system developed also is effective for wild raccoons.     

土地利用变化与土壤养分的变化——以河北省遵化县为例

土地利用变化可以引起土壤养分的变化,以河北省遵化县为例,研究该县1980年到1999年土地利用变化及土壤养分的变化,结果表明,近20a来,旱地、草地、水田面积大幅度减少,林地和村镇用地大幅度增加,旱地转换为林地,土壤有机质提高了21％,全氮提高了10％,碱解氮提高了65％,速效磷提高了17％,速效钾提高了17％。旱地转换为草地,土壤有机质提高38％,全氮提高了37％,碱解氮提高了71％,速效磷提高了2％,速效钾提高了28％。退耕还林还草不仅改变了土地棉覆被,而且提高了土壤养分。     

Demonstration of rabies virus-specific antibody in the sera of free-ranging Iowa raccoons (Procyon lotor).

Between 1984 and 1988, a study was conducted to evaluate the frequency of rabies virus neutralizing antibodies in raccoons (Procyon lotor) in two counties in Iowa. Nine hundred eighty five raccoons were trapped and tagged in Guthrie and Cerro Gordo counties during the spring, summer and fall of each year. Sex, age and weight were recorded for each animal and a blood sample was collected. Serum samples were tested for the presence of serum neutralizing antibodies (SNA) by the rapid fluorescent focus inhibition test (RFFIT), mouse serum neutralization test (MSN), and an indirect fluorescent antibody (IFA) technique for detecting immunoglobulin G. Fifty-one raccoons (5%) were found to have SNA by the RFFIT. Thirty-six serum samples (24 with RFFIT antibody titer greater than 3.0, and 12 less than 3.0) were also tested by the MSN, with results correlating well with the RFFIT results (r = 0.86, P less than 0.01, Kappa = 0.93). In 35 raccoons with SNA by the RFFIT, six individuals had immunoglobulin G binding activity by the IFA test. These results provided serologic evidence of exposure of raccoons to rabies virus in an area free of enzootic raccoon rabies.     

Zygotic associations and multilocus statistics in a nonequilibrium diploid population

The usual approach to characterizing and estimating multilocus associations in a diploid population assumes that the population is in Hardy-Weinberg equilibrium. The purpose of this study is to develop a set of summary statistics that can be used to characterize and estimate the multilocus associations in a nonequilibrium population. The concept of "zygotic associations" is first expanded to facilitate the development. The summary statistics are calculated using the distribution of a random variable, the number of heterozygous loci (K) found in diploid individuals in the population. In particular, the variance of K consists of single-locus and multilocus components with the latter being the sum of zygotic associations between pairs of loci. Simulation results show that the multilocus associations in the variance of K are detectable in a sample of moderate size (> or =30) when the sum of all pairwise zygotic associations is greater than zero and when gene frequency is intermediate. The method presented here is a generalization of the well-known development for the Hardy-Weinberg equilibrium population and thus may be of more general use in elucidating the multilocus organizations in nonequilibrium and equilibrium populations.     

沈阳经济区土地利用和净初级生产力变化

分析了沈阳经济区2000到2010年土地利用变化情况。基于CASA(Carnegie-Ames-Stanford Approach)模型估算2000年、2005年、2010年沈阳经济区净初级生产力(NPP),从行政区划和地类角度分析其时空变化,统计了不同地类转换模式下NPP的损益值,从土地利用变化探讨分析了沈阳经济区土地利用变化带来的NPP变化情况。结果表明:(1)农田,林地和城镇用地为研究区最主要土地利用类型。土地利用最显著变化是城镇用地扩张迅速,农田面积大量减少。林地面积有所减少,草地、湿地、裸地面积变化较小;(2)沈阳经济区NPP呈明显退化趋势,并且时空变化显著,2000到2005年退化幅度大于2005到2010年。除了阜新市有增加,其他市的NPP均为减少;(3)沈阳经济区6种土地利用类型的平均NPP都在下降,降幅最大的是林地。NPP损益分析表明农田转城镇带来的年均NPP损失最大。     

Ochre star mortality during the 2014 wasting disease epizootic: role of population size structure and temperature

Over 20 species of asteroids were devastated by a sea star wasting disease (SSWD) epizootic, linked to a densovirus, from Mexico to Alaska in 2013 and 2014. For Pisaster ochraceus from the San Juan Islands, South Puget Sound and Washington outer coast, time-series monitoring showed rapid disease spread, high mortality rates in 2014, and continuing levels of wasting in the survivors in 2015. Peak prevalence of disease at 16 sites ranged to 100%, with an overall mean of 61%. Analysis of longitudinal data showed disease risk was correlated with both size and temperature and resulted in shifts in population size structure; adult populations fell to one quarter of pre-outbreak abundances. In laboratory experiments, time between development of disease signs and death was influenced by temperature in adults but not juveniles and adult mortality was 18% higher in the 19°C treatment compared to the lower temperature treatments. While larger ochre stars developed disease signs sooner than juveniles, diseased juveniles died more quickly than diseased adults. Unusual 2–3°C warm temperature anomalies were coincident with the summer 2014 mortalities. We suggest these warm waters could have increased the disease progression and mortality rates of SSWD in Washington State.