A dynamic, optimal disease control model for foot-and-mouth disease: I. Model description

A dynamic optimization model was developed and used to evaluate alternative foot-and-mouth disease (FMD) control strategies. The model chose daily control strategies of depopulation and vaccination that minimized total regional cost for the entire epidemic duration, given disease dynamics and resource constraints. The disease dynamics and the impacts of control strategies on these dynamics were characterized in a set of difference equations; effects of movement restrictions on the disease dynamics were also considered. The model was applied to a three-county region in the Central Valley of California; the epidemic relationships were parameterized and validated using the information obtained from an FMD simulation model developed for the same region. The optimization model enables more efficient searches for desirable control strategies by considering all strategies simultaneously, providing the simulation model with optimization results to direct it in generating detailed predictions of potential FMD outbreaks.     

Effects of preemptive atropine administration on incidence of medetomidine-induced bradycardia in dogs

OBJECTIVE: To determine the cardiorespiratory effects of preemptive atropine administration in dogs sedated with medetomidine. DESIGN: Randomized crossover trial. ANIMALS: 12 healthy adult dogs. PROCEDURES: Dogs underwent 6 treatments. Each treatment consisted of administration of atropine (0.04 mg/kg [0.018 mg/lb] of body weight, IM) or saline solution (0.9% NaCl, 1 ml, IM) and administration of medetomidine (10, 20, or 40 microg/kg [4.5, 9.1, or 18.2 microg/lb], IM) 10 minutes later. Treatments were administered in random order, with a minimum of 1 week between treatments. Cardiorespiratory effects before and after atropine and medetomidine administration were assessed. Duration of lateral recumbency and quality of sedation and recovery were assessed. RESULTS: Bradycardia (heart rate < 60 beats/min) was seen in all dogs when saline solution was administered followed by medetomidine, and the dose of medetomidine was not associated with severity or frequency of bradycardia or second-degree heart block. However, a medetomidine dose-dependent increase in mean and diastolic blood pressures was observed, regardless of whether dogs received saline solution or atropine. Preemptive atropine administration effectively prevented bradycardia and second-degree heart block but induced pulsus alternans and hypertension. The protective effects of atropine against bradycardia lasted 50 minutes. Blood gas values were within reference limits during all treatments and were not significantly different from baseline values. Higher doses of medetomidine resulted in a longer duration of lateral recumbency. CONCLUSIONS AND CLINICAL RELEVANCE: Preemptive administration of atropine in dogs sedated with medetomidine effectively prevents bradycardia for 50 minutes but induces hypertension and pulsus alternans.     

Safety, efficacy, and immunogenicity of a modified-live equine influenza virus vaccine in ponies after induction of exercise-induced immunosuppression

OBJECTIVE: To determine safety, efficacy, and immunogenicity of an intranasal cold-adapted modified-live equine influenza virus vaccine administered to ponies following induction of exercise-induced immunosuppression. DESIGN: Prospective study. ANIMALS: Fifteen 9- to 15-month old ponies that had not had influenza. PROCEDURE: Five ponies were vaccinated after 5 days of strenuous exercise on a high-speed treadmill, 5 were vaccinated without undergoing exercise, and 5 were not vaccinated or exercised and served as controls. Three months later, all ponies were challenged by nebulization of homologous equine influenza virus. Clinical and hematologic responses and viral shedding were monitored, and serum and nasal secretions were collected for determination of influenza-virus-specific antibody isotype responses. RESULTS: Exercise caused immunosuppression, as indicated by depression of lymphocyte proliferation in response to pokeweed mitogen. Vaccination did not result in adverse clinical effects, and none of the vaccinated ponies developed clinical signs of infection following challenge exposure. In contrast, challenge exposure caused marked clinical signs of respiratory tract disease in 4 control ponies. Vaccinated and control ponies shed virus after challenge exposure. Antibody responses to vaccination were restricted to serum IgGa and IgGb responses in both vaccination groups. After challenge exposure, ponies in all groups generated serum IgGa and IgGb and nasal IgA responses. Patterns of serum hemagglutination inhibition titers were similar to patterns of IgGa and IgGb responses. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that administration of this MLV vaccine to ponies with exercise-induced immunosuppression was safe and that administration of a single dose to ponies provided clinical protection 3 months later.     

Virus isolation and vaccination of Mediterranean tortoises against a chelonid herpesvirus in a chronically infected population in Italy

A chelonid herpesvirus was isolated from a group of tortoises in Italy with a history of increased mortality and upper digestive and respiratory tract disease. The isolated virus was inactivated with formalin and used to prepare a nonadjuvanted vaccine and a vaccine adjuvanted with aluminum hydroxide. 57 tortoises, 26 Testudo hermanni, 25 T. graeca, and 6 T. marginata, were included in the study. The animals were vaccinated 3 times at 45 day intervals. Blood was collected from the animals 14 days prior to the first vaccination, and on day 0, 25, 45, 90, 113 and 369 after the first vaccination. Plasma antibody titers to the homologous chelonid herpesvirus were determined using a virus neutralization test (VNT). No significant rise in antibody titer was noted in the vaccinated animals. Antibody titers measured dropped below the cutoff-level sporadically in all positive animals. Repeat serological testing may therefore be necessary in order to detect seropositive animals.     

Detection of bovine immunodeficiency virus DNA in the blood and semen of experimentally infected bulls

Five 18- to 24-month-old bulls were inoculated with either a cell suspension containing bovine immunodeficiency virus (BIV-FL112; 3 bulls) or a BIV-free cell suspension (2 bulls). Blood and semen specimens were collected once a week for 14 weeks, and seroconversion was confirmed by indirect immunofluorescent antibody (IFA) testing. The presence of BIV in blood and semen was determined by virus isolation and/or polymerase chain reaction (PCR) assays. Antibodies to BIV were detected in the 3 experimentally infected bulls as early as day post inoculation (DPI) 17, and levels peaked at DPI 37-58. BIV was isolated from the peripheral blood mononuclear cells (MNCs) of the infected bulls at DPI 9 (2 bulls) and DPI 23 (1 bull), and could be isolated from one animal up to DPI 65. PCR analysis of MNC DNA, using BIV pol gene primers, detected virus in all three of the experimentally infected bulls from DPI 9 until the termination of the experiment at DPI 98. Efforts to isolate a significant number of non-spermatozoal cells (NSC) by gradient separation from the semen of the experimentally infected bulls were unsuccessful. Two methods for the extraction of total NSC DNA from up to 2 ml of non-extended semen were employed; however, no BIV pol fragment was amplified from these DNA preparations. Additionally, 30 bulls from artificial insemination (AI) centers were evaluated for BIV infection by PCR. No amplification products were obtained from MNC DNA from the AI submissions using primer sets for both the BIV pol and env genes.     

Intraocular melanoma in an alpaca

A case of primary intraocular melanoma in an alpaca is reported. This patient also presented with a mild normocytic, normochromic anemia and hypoproteinemia. These can be markers of an immunodeficiency syndrome associated with llamas. Although this patient did not appear to have clinical signs of this syndrome, its presence needed to be ruled out as animals affected with this syndrome are subject to recurrent severe debilitating diseases and death. To our knowledge, intraocular melanoma has not been previously reported in an alpaca.     

Prevalence of Campylobacter spp isolated from the intestinal tract of pigs raised in an integrated swine production system

OBJECTIVE: To enumerate the prevalence of Campylobacter isolates in the intestinal tract of market-weight swine raised in an integrated swine operation in Texas. SAMPLE POPULATION: Samples of cecal contents were collected from 595 pigs (mean body weight, 110 kg [242 lb]) at time of slaughter. Pigs were off-spring of Yorkshire-Landrace sows and Duroc or Hampshire boars. Pigs originated from 4 farrow-to-finish farms. PROCEDURE: During a 9-month period, visits were made to a slaughter plant to remove cecal contents from market-weight hogs. Samples were obtained from 50 pigs/visit from designated farms so that samples were obtained 3 times from pigs of each of 4 farms. Isolation of Campylobacter spp was accomplished by use of enrichment broth and restrictive media, using microaerophilic conditions. RESULTS: Campylobacter spp were isolated from 70 to 100% of the pigs, depending on the farm and the date the samples were collected. Campylobacter coli was isolated from 20 to 100% (mean, 60%) of samples, and C jejuni was isolated from 0 to 76% (mean, 31%) of samples. Campylobacter lari was isolated from 2 pigs. Concentrations of C coli or C jejuni ranged from 10(3) to 10(7) colony-forming units/g of cecal content. CONCLUSIONS AND CLINICAL RELEVANCE: Campylobacter coli generally is accepted as a common inhabitant of the intestinal tract of swine. However, analysis of results of this study suggests that a relatively high prevalence of C jejuni may be found in pigs raised on specific farms.