Epizootic of rabies in raccoons in Maryland from 1981 to 1987.

The epizootic of rabies in raccoons entered Maryland in 1981 and systematically moved through the state affecting raccoons in all counties except those of the lower Eastern Shore. A precoded surveillance form was provided to all county and city health departments and data were requested for each animal head submitted for testing for the year 1985. The disease persisted and, in 1987, all counties previously reporting rabies in raccoons also had documented cases in other species. The incidence of rabies in raccoons increased in late winter and peaked in March. Most human exposures occurred during daylight hours and in private yards. Agricultural areas were similarly affected by rabid animals. Analysis of vaccination status of animals exposed to rabid animals gave estimations of statewide vaccination rates for dogs (70%) and cats (28%). The danger of rabies in cats was emphasized by the large number of animals exposed by each rabid cat. The spillover of rabies in raccoons to other species persisted in all jurisdiction through 1992, with periodic upsurges of disease at 3- to 4-year intervals as the raccoon population is replenished. Rabies was not diagnosed in any human beings.     

Persistence of elevated rabies prevention costs following post-epizootic declines in rates of rabies among raccoons (Procyon lotor)

Determining the benefits to cost relationships among different approaches to rabies control and prevention has been hindered by the inherent temporal variability in the dynamics of disease among wildlife reservoir hosts and a tangible and objective measure of the cost of rabies prevention. A major and unavoidable component of rabies prevention programs involves diagnostic testing of animals and the subsequent initiation of appropriate public health responses. The unit cost per negative and positive diagnostic test outcome can be reasonably estimated. This metric when linked to methodologies subdividing the epizootic process into distinct temporal stages provided the requisite detail to estimate benefits derived from rabies control strategies. Oral rabies vaccine (ORV), for prevention of the raccoon-associated variant of rabies, has been distributed in Ohio and adjoining states in an effort to develop an immune barrier to the westward spread of epizootic raccoon rabies. The costs of ORV delivery have been quantified. Herein, the cost structures required to assess the benefits accrued by prevention were developed. A regression model was developed effectively predicting (r² = 0.70) the total number of rabies diagnostic tests performed by 53 counties in five northeastern (NE) states from 1992 to 2001. Five temporal stages sufficed to capture the range of variability in the raccoon rabies epizootic process. Unit costs, dollars per diagnostic test outcome, were calculated for negative and positive results from published reports. Ohio counties were matched to NE counties based on similar socioeconomic characters. A “pseudo-epizootic” of raccoon rabies was introduced into Ohio and the costs savings from ORV were derived as the excess costs imposed by epizootic spread throughout the state. At 46 km/year (range modeled, 30–60 km/year), the pseudo epizootic spread, and reached the enzootic stage, in all Ohio counties by year 13 (range modeled, 11–17 years). Cumulative excess costs for Ohio ranged between $11 and $21 million; counties of low socioeconomic status experienced the greatest relative excess costs. The costs for rabies prevention activities reached apices during the epizootic stage of raccoon rabies (2.7–10.8 times baseline) an unforeseen finding indicated elevated costs persisted (1.7–7.2 times baseline) into the enzootic stage.     

Morphologic and immunoperoxidase study of neurologic lesions in naturally acquired rabies of raccoons.

Histopathologic (hematoxylin and eosin [HE]) and immunoperoxidase (streptavidin-biotin complex) methods were used for examination of formalin-fixed tissues of rabid raccoons from an enzootic area of Pennsylvania. Extensive morphologic lesions of rabies encephalitis were present in the cerebrum and the brain stem regions. Negri bodies were detected by both methods and were present in the brain (cerebral cortex, hippocampus, brain stem, cerebellum, and cervical spinal cord) and in the ganglia of the trigeminal nerves. The viral inclusions were also seen in ganglion cells in the tongue, parotid salivary glands, pancreas, intestines, and adrenal glands. These sites were not associated with any inflammatory cellular infiltrate. The immunoperoxidase method was superior to HE for the detection of Negri bodies. Because lesions of rabies encephalitis were consistently observed in the cerebrum, brain stem, and cervical spinal cord regions, these areas of the brain should be included when raccoons are examined by the fluorescent antibody test for rabies.     

Benefits and costs of using an orally absorbed vaccine to control rabies in raccoons.

In November 1989, the epizootic of rabies affecting raccoons in the mid-Atlantic states reached New Jersey. An economic evaluation was conducted in 2 counties first affected by the epizootic to estimate the costs of the epizootic and to assess the costs and benefits of orally administering a newly developed recombinant rabies vaccine to prevent further spread of the disease. Data on expenditures associated with prevention of rabies in human beings and domestic animals and laboratory testing of suspect animals were collected and analyzed for 1988 (before the epizootic) and 1990 (first full year of the epizootic). Benefit-cost ratios were calculated and used to evaluate the economic advisability of the vaccine at various vaccination program alternatives. Two indices of capital investment analysis, payback period and net present value, were used to evaluate the economic benefits of the rabies vaccine. Expenditures were estimated to be $1,952,014 in 1990 (primarily for pet animal vaccinations), compared with $768,488 in 1988. Benefit-cost ratios ranged from 2.21 for the most expensive vaccination program alternative to 6.80 for the least expensive alternative. The payback period varied from 0.69 to 2.11 years, and the net present value ranged from $2,105,453 to $4,877,452. The high costs of this epizootic necessitated the reallocation of scarce public health resources to various rabies prevention activities, particularly the vaccination of dogs. This study also demonstrated the usefulness of benefit-cost analysis in developing public health strategies. Although the mass application of this recombinant vaccine was found to be economically beneficial, other qualitative considerations must be used to supplement these findings.     

Use of infrared thermography to detect signs of rabies infection in raccoons (Procyon lotor).

Infrared thermography was evaluated as a technique to determine if raccoons (Procyon lotor) experimentally infected with rabies virus could be differentiated from noninfected raccoons. Following a 10-day adjustment period, raccoons (n = 6) were infected with a virulent rabies street strain raccoon variant by injection into the masseter muscle at a dose of 2 x 10(4) tissue-culture infectious dose (TCID50) in 0.2 ml (n = 4) or 10(5) TCID50 in 1 ml (n = 2). Five of the six raccoons developed prodromal signs of rabies 17 to 22 days postinoculation (PI) and distinctive clinical signs of furious rabies between 19 and 24 days PI. At the time of euthanasia, which occurred 2 days after the onset of clinical signs of rabies, these five raccoons tested positive for rabies virus in brain tissue. Infrared thermal images of each raccoon were recorded twice daily during the preinoculation and PI periods. No apparent differences were identified among thermal temperatures compared among days for the eye, average body surface, and body temperature recorded from subcutaneous implants throughout the experiment for any of the six raccoons. However, increases in infrared surface temperature of the noses and differences in the visual thermal images of the noses were detected when animals began showing clinical signs of rabies. Differences were detected among the mean infrared nose temperatures for the disease progression intervals (F3.12 = 70.03, P < 0.0001). The mean nose temperature in the clinical rabies stage (30.4 +/- 3.5 degrees C) was significantly elevated over the prodromal stage (F1,12 = 151.85, P < 0.0001). This experiment provides data indicating that infrared thermography can be used in an experimental setting to detect raccoons in the infectious stage and capable of exhibiting clinical signs of rabies.     

Cytauxzoon felis infection in cats in the mid-Atlantic states: 34 cases (1998-2004)

OBJECTIVE: To describe the demographic and clinical characteristics of feline cytauxzoonosis in the mid-Atlantic states and compare the Cytauxzoon felis 18S rRNA gene sequences from affected cats with sequences reported from affected cats in other regions. DESIGN: Retrospective case series. ANIMALS: 34 cats with C. felis infection. PROCEDURE: Medical records of cats in which C. felis infection was diagnosed from May 1998 through June 2004 were reviewed; data collected included signalment, month of diagnosis, geographic location, clinicopathologic abnormalities, medical treatments, outcome, and necropsy findings when applicable. Cytauxzoon felis DNA was amplified, cloned, and sequenced from 4 of these cats and compared with previously reported C. felis DNA sequences. RESULTS: Of 34 C. felis-infected cats, 28 resided in North Carolina, 3 resided in South Carolina, and 3 resided in Virginia; in 32 cats, a diagnosis of C. felis infection was made in April through September. Pancytopenia and icterus were the most common clinicopathologic abnormalities. Thirty-two cats either died or were euthanatized, and 2 cats survived. At 5 veterinary hospitals, multiple cases were identified, and 4 multicat households had > 1 cat infected with C. felis. The 18S rRNA gene sequences characterized in organisms obtained from 4 cats were nearly identical to C. felis DNA sequences reported from other US regions. CONCLUSIONS AND CLINICAL RELEVANCE: Data indicate that veterinarians in the mid-Atlantic region of the United States should consider C. felis infection in cats that become ill with fever, icterus, and pancytopenia or bicytopenia, especially in the spring and summer months.     

Porcupine quills in raccoons as an indicator of rabies, distemper, or both diseases: disease management implications

A relationship was detected between the presence of embedded porcupine quills and the diagnosis of rabies in raccoons in eastern Canada during 1999-2004. No relationship was found between the presence of quills in raccoons and the diagnosis of canine distemper. Raccoons with embedded quills should be submitted for rabies testing.     

Control of terrestrial animal rabies in Anne Arundel County, Maryland, after oral vaccination of raccoons (1998-2007)

Objective-To evaluate the effectiveness of an oral rabies vaccination (ORV) project conducted from 1998 through 2007 in Anne Arundel County, Md, for the control of rabies in terrestrial animals. Design-Retrospective analysis of surveillance data (1997 through 2007). Animals-Free-ranging raccoons (Procyon lotor) and other terrestrial mammals. Procedures-Vaccinia-rabies glycoprotein recombinant virus oral rabies vaccine-bait units were distributed annually by aircraft and ground teams targeting free-ranging raccoons. Approximately 2 to 4 weeks following the vaccine-bait placement, raccoons were live trapped, sedated, processed, and then released. Serologic samples were tested for the presence of rabies virus-neutralizing antibodies (RVNAs). Bait acceptance was estimated by analysis of tetracycline biomarking of sampled teeth. Rabies incidence was determined by the passive identification of rabid terrestrial animals. Results-The incidence of rabies in terrestrial animals decreased 92% between 1997 (the year prior to the start of the ORV project) and 2007. The mean RVNA prevalence across all years was 33% among trapped raccoons in areas baited with a fish meal polymer bait type, whereas the mean bait acceptance was 30%. Adult raccoons had a seropositivity rate twice that of juvenile raccoons, whereas the bait acceptance rate between adults and juveniles did not differ significantly. For areas baited with a coated sachet bait, adults and juveniles had the same seroprevalence. Juveniles had better seroprevalence when the annual campaign started in September and October, compared with August. Conclusions and Clinical Relevance-The ORV project contributed to a significant decrease in annual incidence of terrestrial animal rabies in Anne Arundel County, Md, during the 10-year project period. For fish meal polymer baits, juvenile raccoons accessed bait at the same rate as adult raccoons but had a significantly lower prevalence of RVNAs. For coated sachet baits, seroprevalence was the same in both age groups. The time of year the bait distribution occurred and the bait type used may be partial explanations for the difference in RVNA seroprevalence between adults and juvenile raccoons.     

Control of rabies: epidemiology of rabies in Asia and development of new-generation vaccines for rabies

Rabies is an enzootic viral disease widespread throughout the world. Although it is a vaccine-preventable disease, the annual number of human deaths caused by rabies is estimated to be 32,000 in Asia. Phylogenetic analysis based on sequence data of the partial N gene of rabies viruses in Asia has shown that the viruses are divided into five genogroups, distributed in Middle East, South Asia, South East Asia, Malay, and Arctic regions. The genetic relationships among these rabies viruses agree basically with the results of previous studies. Meanwhile, new types of vaccines are being developed by applying gene manipulation techniques to rabies virus in order to overcome the disadvantages of current vaccines. This article reviews the molecular epidemiology of rabies in Asia and progress made in the development of new-generation rabies vaccines with the goal of elimination or control of rabies in Asia.     

Survey of the dog population of Zimbabwe and its level of rabies vaccination

A random sample survey using personal interviews was conducted in Zimbabwe in 1986 to determine the size and structure of the national dog population and its level of rabies vaccination. There was an average of 0.91 dogs per household in Zimbabwe giving an extrapolated total population of 1,308,577 dogs. There was a dog to people ratio of 1:6.5 and an average of 3.4 dogs per square kilometre. The ratio of adult male to female dogs was 0.56:0.44, with 20 per cent of the dog population being less than three months old. In the period 1950 to 1986 there was a 4.7 per cent per annum growth rate of the dog population. In one of the provinces, Manicaland, dogs were found to have an average age of 2.3 years and a life expectancy at birth of 4.6 years. An estimated 40 per cent of the dog population three months old and above had been vaccinated against rabies in 1985/1986. With the rabies incidence in Zimbabwe still unacceptably high this level of vaccination is clearly inadequate and measures designed to increase it are discussed.     

Hematotropic parasites of translocated raccoons in the southeast.

Ninety-four raccoons (Procyon lotor) from 6 southeastern states were examined for hematotropic parasites, to evaluate the carrier potential of these animals as they relate to translocation and release for hunting purposes. Four species of hematotropic parasites were identified, viz, Babesia procyonis, Haemobartonella procyoni, Hepatozoon procyonis, and Trypanosoma cruzi. Lesions in infected raccoons were associated only with H procyonis. Babesia procyonis was enzootic in populations of raccoons used as sources for exportation and in raccoons resident in typical release areas. Haemobartonella procyoni, H procyonis, and T cruzi were prevalent only in locales of raccoon origin. Due to the potential pathogenicity of H procyonis and T cruzi in raccoons or other hosts, the practice of translocating raccoons from enzootic to nonenzootic areas was considered biologically hazardous.     

Predictive qualitative risk model of bovine rabies occurrence in Brazil

Bovine rabies remains endemic in Brazil and despite control efforts, the disease still spreads insidiously. The main vector is the hematophagous bat, Desmodus rotundus. The present work aimed to create a predictive qualitative model of the occurrence of bovine rabies in each municipality in 25 of the 27 Brazilian States. The risk of rabies transmission from bats to bovine was estimated using decision-tree models of receptivity and vulnerability. Questionnaires, which covered a number of questions related to the surveillance of possible risk factors, such as bovine rabies outbreaks in the previous year, the presence of bat roosts, bat rabies positivity and environmental changes, were sent to the local veterinary units of each State. The bovine density and geomorphologic features were obtained from national databases and geographic information systems. Of the 433 municipalities presenting bovine rabies outbreaks in 2010, 178 (41.1%) were classified by the model as high risk, 212 (49.0%) were classified as moderate risk, 25 (5.8%) were classified as low risk, whereas the risk was undetermined in 18 municipalities (4.1%). An ROC curve was built to determine if the risk evaluated by the model could adequately discriminate between municipalities with and without rabies occurrence in future years. The risk estimator for the year 2011 was classified as moderately accurate. In the future, these models could allow the targeting of rabies control efforts, with the adoption of control measures directed to the higher risk locations and the optimization of the field veterinary staff deployment throughout the country. Additionally, efforts must be made to encourage continuous surveillance of risk factors.     

Prevalence of Toxoplasma gondii infection in raccoons.

Serum samples from 427 raccoons (93 from Pennsylvania, 45 from New Jersey, 72 from South Carolina, 68 from Virginia, 30 from Iowa, and 119 from Ohio) were evaluated for Toxoplasma gondii antibodies in dilutions of 1:25, 1:50, and 1:500. The distribution of T gondii antibody titers was less than 1:25 for 212 raccoons (49.6%), 1:25 for 34 raccoons (7.9%), 1:50 for 117 raccoons (27.4%), and greater than or equal to 1:500 for 64 raccoons (14.9%). Tissue cysts were seen in the liver, and tachyzoites were in the brain of a raccoon with abnormal neurologic signs and concurrent infection with canine distemper virus. Organisms in the liver were stained with anti-T gondii serum, and the raccoon had a T gondii titer of 1:160 in the agglutination test.     

Risk-based cost modelling of oral rabies vaccine interventions for raccoon rabies

Distribution of oral rabies vaccine (ORV) is an effective but costly strategy to control raccoon rabies. Because of high costs, ORV for raccoon rabies in the U.S. has been limited primarily to epizootic areas, leaving extensive raccoon rabies regions without any ORV intervention. Several cost scenarios for ORV application in raccoon rabies enzootic and epizootic regions were modelled in New York State to obtain estimated costs of ORV baits per scenario and potential savings compared with a uniform ORV baiting strategy. These cost scenarios modelled at the census tract, level the application of ORV baits at different densities according to levels of risk defined by the observed number of raccoon rabies cases per km2 and the expected number of cases per km2 estimated with a Poisson regression model. Bait purchase costs were lower using the modelled cost scenarios than a uniform baiting strategy, for both the NYS enzootic region and the Long Island epizootic zone. The proportion of savings for the NYS enzootic region was 29.57%, and the proportion of savings for the Long Island epizootic zone was 38.9%. Use of these cost scenarios to determine bait distribution by rabies risk level should be considered to maximize efficacy and reduce costs of ORV interventions.     

Serological survey for antibodies to Leptospira in dogs and raccoons in Washington State

A high number of reported canine leptospirosis cases occurred in Washington State from 2004 to 2006. This prompted a serosurvey of healthy dogs from around the state to determine the distribution of exposure risk and to provide insight into serovar epidemiology in the region. In addition, a convenience sample of sera from injured raccoons was also tested, and clinical serological data from the Washington Animal Disease Diagnostic Laboratory were examined. The proportion of dogs with an antibody titre (>or=1:100) to any serovar was 27/158 (17.1%, 95% CI 11.6-23.9), and that proportion among raccoons was 22/115 (19.1%, 95% CI 12.4-27.5) suggesting that the potential for exposure in Washington state is not uncommon. The most frequently detected serovars in healthy dogs were Autumnalis, Icterohemorrhagiae and Canicola, in clinical canine samples Autumnalis, Bratislava and Pomona were more frequent and in sick or injured raccoons Autumnalis, and Pomona were most frequently detected. Clinical canine serology demonstrated a late summer-fall seasonality that was consistent with other reports. An outbreak of canine leptospirosis occurred during 2004-2006 and was located primarily in western Washington counties, as were three reported human cases in 2005. Canine leptospirosis surveillance is an important tool for detecting human risk of exposure and may provide insights into which serovars are currently of clinical importance.     

Meeting the urgent need for rabies education in Haiti

The highest rate of human rabies deaths reported in the Americas is in Haiti, and most of these deaths result from rabies virus infections that occur after individuals are bitten by infected dogs and do not receive rabies post‐exposure prophylaxis. One barrier to rabies prevention in Haiti is a lack of knowledge about this disease among healthcare professionals and community members. During the past 4 years, The US Centers for Disease Control and Prevention has collaborated with public health officials and partners to develop, test and refine educational materials aimed at filling this need for rabies education. This report summarizes the use of feedback from knowledge, attitudes and practises surveys; key informant interviews; and focus groups to develop culturally appropriate rabies prevention materials for community members, health officials, clinicians, laboratory professionals, veterinary professionals, government officials and national and local district leaders about ways to prevent rabies. These formative research methods were critically important in ensuring that the materials would be culturally appropriate and would stand the greatest likelihood of motivating Haitians to protect themselves from rabies. Centers for Disease Control and Prevention is using lessons learned in Haiti to develop and test materials in other countries with high rates of canine rabies.