Impairment of oxidative burst in porcine neutrophils induced by pseudorabies virus

Industrial swine production is affected by several serious viral diseases, such as pseudorabies, hog cholera, porcine reproductive and respiratory syndrome, which are frequently complicated with the increased incidence of bacterial complications such as Actinobacillus pleuropneumoniae (APP). This clinical observation is suggestive of a virus-bacteria synergism on the pathogenesis. One hypothesis is that viruses induce polymorphonuclear cell (PMNs, primarily neutrophils) dysfunction resulting in defective antibacterial resistance. The purpose of this study was to use the pseudorabies virus (PrV) as a model to explore the possibility of virus-induced PMN dysfunctions in pigs. The goals were to evaluate, in ex vivo settings, the oxidative burst (OB) function of pig PMNs, and to evaluate whether PrV could affect these responses to APP. We found that PrV served as a mild OB stimulant (2-fold) to pig PMNs, which also launched a significant burst to phorbol 12-myristate 13-diacetate (PMA; 61-fold), to non-opsonized, heat-killed and formaldehyde-fixed APP (8-fold), and to normal pig serum-opsonized APP (34-fold). Interestingly, the PMA-induced OB could be reduced 50-70% by preincubating PMNs with PrV, and the critical target was not likely the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase itself. Inactivated PrV was as efficient as viable PrV at exerting the inhibitory effect. On the other hand, PrV exerted a primarily additive effect on APP-induced OB, when the cytotoxic effect of APP on PMNs was avoided. The current finding suggests the possibility that activated PMNs are susceptible to PrV-induced dysfunction, and that the PrV-APP synergism may require upstream stimuli of PMNs to be initiated.     

Construction and evaluation of genetically engineered replication-defective porcine reproductive and respiratory syndrome virus vaccine candidates

Porcine reproductive and respiratory syndrome virus (PRRSV) is an emerging pathogen causing significant economic losses in the swine industry worldwide. Two novel gene-deleted viruses were constructed and evaluated as vaccine candidates. Using the full-length infectious cDNA clone of North American PRRS isolate P129, the ORF2 and ORF4 genes (which encoded minor structural glycoproteins GP2a/2b and GP4, respectively) were individually deleted from the viral genome. Both deletion mutants were non-viable in MARC-145 cells and porcine alveolar macrophages, indicating that both genes are essential for virus replication. To rescue the replication-defective PRRSV, two complementing cell lines, MARC-2000 and MARC-400, were established to stably express the PRRSV GP2 and GP4 proteins, respectively. These cells were able to complement the deleted gene function of PRRSV in trans and supported production of the replication-defective DeltaORF2-PRRSV and DeltaORF4-PRRSV viruses. Both DeltaORF2-PRRSV and DeltaORF4-PRRSV viruses were propagated for 40-50 generations in the corresponding complementing cells and remained replication-defective in MARC-145 cells. To examine the immunogenic potential of the replication-defective PRRSV as vaccine candidates, four groups of pigs, 20 pigs per group, were immunized twice with DeltaORF2-PRRSV or DeltaORF4-PRRSV and challenged with the homologous virulent virus at 3 weeks post-immunization. In spite of the fact one group showed significant reduction in virus load, we could not demonstrate improvement from clinical diseases in this vaccination/challenge study. However, we did show that the cDNA clone of PRRSV can be a useful tool to genetically engineer PRRSV vaccine candidates and to study pathogenesis and viral gene functions.     

Infectious cDNA clones of porcine reproductive and respiratory syndrome virus and their potential as vaccine vectors

Full-length infectious cDNA clones have recently become available for both European and North American genotypes of porcine reproductive and respiratory syndrome virus (PRRSV), and it is now possible to alter the PRRSV genome and create genetically defined mutant viruses. Among many possible applications of the PRRSV infectious cDNA clones, development of genetically modified vaccines is of particular interest. Using infectious clones, the PRRSV genome has been manipulated by changing individual amino acids, deleting coding regions, inserting foreign sequences, and generating arterivirus chimeras. The limited available data suggest that all structural proteins of PRRSV are essential for replication of the virus, and that PRRSV infectivity is relatively intolerant of subtle changes within the structural proteins. The major tasks in PRRSV research are to identify virulence factors and pathogenic mechanisms, and to understand the structure-function relationships of individual viral proteins. Utilizing these infectious clones as tools, a new generation of safe and efficacious PRRS vaccines may be constructed.     

Time and financial costs of programs for live trapping feral cats

OBJECTIVE: To determine the time and financial costs of programs for live trapping feral cats and determine whether allowing cats to become acclimated to the traps improved trapping effectiveness. DESIGN: Prospective cohort study. ANIMALS: 107 feral cats in 9 colonies. PROCEDURE: 15 traps were set at each colony for 5 consecutive nights, and 5 traps were then set per night until trapping was complete. In 4 colonies, traps were immediately baited and set; in the remaining 5 colonies, traps were left open and cats were fed in the traps for 3 days prior to the initiation of trapping. Costs for bait and labor were calculated, and trapping effort and efficiency were assessed. RESULTS: Mean +/- SD overall trapping effort (ie, number of trap-nights until at least 90% of the cats in the colony had been captured or until no more than 1 cat remained untrapped) was 8.9 +/- 3.9 trap-nights per cat captured. Mean overall trapping efficiency (ie, percentage of cats captured per colony) was 98.0 +/- 4.0%. There were no significant differences in trapping effort or efficiency between colonies that were provided an acclimation period and colonies that were not. Overall trapping costs were significantly higher for colonies provided an acclimation period. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that these live-trapping protocols were effective. Feeding cats their regular diets in the traps for 3 days prior to the initiation of trapping did not have a significant effect on trapping effort or efficiency in the present study but was associated with significant increases in trapping costs.     

Persistent urinary tract infections and reinfections in 100 dogs (1989-1999)

A retrospective study was performed of 100 dogs with persistent urinary tract infections (UTIs) or reinfections presenting to the North Carolina State University (Raleigh, NC) Veterinary Teaching Hospital between 1989 and 1999. Criteria for selection included > or = 2 positive urine cultures within a 6-month period. Signalment, presence of predisposing disorders, urinalysis and urine culture results, and treatment strategies were extracted from the medical records. Dogs were a median age of 7 years when the UTI was 1st diagnosed. Dogs younger than 3 and older than 10 years were at increased and decreased risks, respectively, for reinfections or persistent UTIs. Spayed females were more common in the UTI population. More than half of the dogs were asymptomatic for a UTI at 1st presentation. Urine sediment examinations identified hematuria, pyuria, and bacteriuria in 47, 72, and 85% of the samples, respectively. The most commonly isolated organisms were Escherichia coli and Streptococcus/Enterococcus spp.; multiple isolates also were common. Of the isolates, 29.5% were resistant to achievable serum concentrations of all antibiotics commonly prescribed for PO administration. Dogs with abnormal micturition were more likely to have infections by organisms resistant to commonly prescribed antibiotics. Potentially predisposing disorders were identified in 71 dogs. A correction of these disorders was accomplished in 35% of these 71 dogs. Dogs given standard antibiotic therapy without addressing predisposing disorders experienced poor control of their UTIs; 74.5% of these dogs had an apparent disease-free interval (ADFI) of < 8 weeks. By comparison, dogs in which predisposing disorders were corrected or those that were treated with low-dose, long-term antibiotic regimens subjectively had better control.     

General toxicologic hazards and risks for search-and-rescue dogs responding to urban disasters

In large-scale disasters, it is not always possible to identify every potential toxic agent to which SAR dogs may be exposed. However, an understanding of the basic means by which dogs may be exposed to toxic agents can aid veterinarians in determining basic risks for particular SAR sites and allow veterinarians to institute general preventive measures (eg, frequent eye washes) to minimize exposure. Discussions with public health and other authorities on-site may aid in identifying site-specific risks for SAR dogs. Finally, ensuring that SAR dog handlers are aware of basic risks, precautions, and decontamination measures is essential, as handlers are the first line of defense in preventing illness or injury to SAR dogs as they work a disaster area.     

Thrombocytosis in 24 Horses (1989–1994)

The records of horses presented to the Veterinary Teaching Hospital of North Carolina State University College of Veterinary Medicine between January 1, 1989 and April 30, 1994 were evaluated to determine risk factors associated with thrombocytosis. Of the 2,346 horses for which a CBC was performed, 24 (1.0%) had a platelet count > 400,000/μL. Demographic, diagnostic, physical examination, and clinicopathologic variables from these cases were compared with a reference population consisting of 189 horses with a normal platelet count presenting during the same period. Infectious/inflammatory disorders were observed more commonly in horses with high platelet counts than in horses with normal platelet counts. Initial independent evaluation of demographic variables revealed that horses more than 3 years of age, females, and geldings were less likely to have thrombocytosis than were younger horses or stallions. Independent analysis of clinicopathologic variables revealed that horses with thrombocytosis were more likely to have hyper-fibrinogenemia, leukocytosis, hypoproteinemia, and anemia than were horses with normal platelet counts. Physical examination parameters associated with thrombocytosis included tachycardia and pyrexia. In the final multivariable model, the variables with the strongest association with thrombocytosis included leukocytosis, anemia, and hyper-fibrinogenemia. Thrombocytosis rarely causes clinical problems in horses and is not likely to require specific antiplatelet therapy. The strong association of thrombocytosis with infectious/inflammatory disorders, however, should lead clinicians to suspect these types of conditions in horses with high platelet counts.     

Comparison of individual and pooled sampling methods for detecting bacterial pathogens of fish.

Examination of finfish populations for viral and bacterial pathogens is an important component of fish disease control programs worldwide. Two methods are commonly used for collecting tissue samples for bacteriological culture, the currently accepted standards for detection of bacterial fish pathogens. The method specified in the Office International des Epizooties Manual of Diagnostic Tests for Aquatic Animals permits combining renal and splenic tissues from as many as 5 fish into pooled samples. The American Fisheries Society (AFS) Blue Book/US Fish and Wildlife Service (USFWS) Inspection Manual specifies the use of a bacteriological loop for collecting samples from the kidney of individual fish. An alternative would be to more fully utilize the pooled samples taken for virology. If implemented, this approach would provide substantial savings in labor and materials. To compare the relative performance of the AFS/USFWS method and this alternative approach, cultures of Yersinia ruckeri were used to establish low-level infections in groups of rainbow trout (Oncorhynchus mykiss) that were sampled by both methods. Yersinia ruckeri was cultured from 22 of 37 groups by at least 1 method. The loop method yielded 18 positive groups, with 1 group positive in the loop samples but negative in the pooled samples. The pooled samples produced 21 positive groups, with 4 groups positive in the pooled samples but negative in the loop samples. There was statistically significant agreement (Spearman coefficient 0.80, P < 0.001) in the relative ability of the 2 sampling methods to permit detection of low-level bacterial infections of rainbow trout.     

Identification of Atlantic bluefin tuna (Thunnus thynnus) stocks from putative nurseries using otolith chemistry

Chemical signatures in the otoliths of teleost fishes represent natural tags that may reflect differences in the chemical and physical characteristics of an individuals' environment. Otolith chemistry of Atlantic bluefin tuna (Thunnus thynnus) was quantified to assess the feasibility of using these natural tags to discriminate juveniles (age 0 and age 1) from putative nurseries. A suite of six elements (Li, Mg, Ca, Mn, Sr and Ba) was measured in whole otoliths using solution‐based inductively coupled plasma mass spectrometry. Otolith chemistry of age‐1 T. thynnus collected from the two primary nurseries in the Mediterranean Sea and western Atlantic Ocean differed significantly, with a cross‐validated classification accuracy of 85%. Spatial and temporal variation in otolith chemistry was evaluated for age‐0 T. thynnus collected from three nurseries within the Mediterranean Sea: Alboran Sea (Spain), Ligurian Sea (northern Italy), and Tyrrhenian Sea (southern Italy). Distinct differences in otolith chemistry were detected among Mediterranean nurseries and classification accuracies ranged from 62 to 80%. Interannual trends in otolith chemistry were observed between year classes of age‐0 T. thynnus in the Alboran Sea; however, no differences were detected between year classes in the Tyrrhenian Sea. Age‐0 and age‐1 T. thynnus collected from the same region (Ligurian Sea) were also compared and distinct differences in otolith chemistry were observed, indicating ontogenetic shifts in habitat or elemental discrimination. Findings suggest that otolith chemistry of juvenile T. thynnus from different nurseries are distinct and chemical signatures show some degree of temporal persistence, indicating the technique has considerable potential for use in future assessments of population connectivity and stock structure of T. thynnus.     

Occurrence of Psorospermium sp. in several North American crayfish species, with comparative notes on Psorospermium haeckeli in the European crayfish, Astacus astacus

Psorospermium haeckeli is a thick-walled, unicellular organism widely reported in European astacid crayfish. Its taxonomic status and life cycle have not been elucidated. It is often referred to as a “parasite”, but conclusive evidence has yet to be found. Recent examination of two North American crayfish species, Procambarus clarkii and Procambarus zonangulus, confirmed its presence in the south-central USA (Louisiana) with morphologies that differ from that of P. haeckeli. This form had been previously reported from Orconectes virilis in southern Canada. We report here the presence of this North American form of Psorospermium in additional North American crayfish including Orconectes immunis and Orconectes rusticus from the northern USA (Minnesota and Wisconsin), Procambarus alleni and Procambarus fallax from the southern USA (Florida), and Pacifastacus leniusculus from the western USA. We also confirm this Psorospermium in O. rusticus from eastern Canada (Ontario). It was not, however, confirmed in several additional southern crayfish species including Cambarus diogenes, Cambarellus puer, Fallicambarus fodiens, and Orconectes palmeri. We describe the morphological forms of this Psorospermium and conclude that it is present in many crayfish species in North America.