Assessment of changes in blood volume in response to resuscitative fluid administration in dogs

Objective: To determine the continuous changes in blood volume in response to fluid administration using an in‐line hematocrit monitor. Design: Prospective study. Setting: Research laboratory. Animals: Four healthy dogs. Interventions: Each dog received intravenous boluses of 80 mL/kg of 0.9% saline (S), 4 mL/kg of 7.5% saline (HS), 20 mL/kg of dextran 70 (D), 20 mL/kg of hetastarch (HES), or no fluids (control, C) on separate occasions. Fluids were administered at 150 mL/min in the S, D, and HES groups, and at 1 mL/kg/min in the HS group. Measurements and main results: Blood volume changes were measured every 20 seconds for 240 minutes using an in‐line hematocrit monitor. There was a rapid rise in blood volume during all infusions. Immediately after the administration of crystalloid fluids, the rapid rise in blood volume ceased. Subsequently, there was a steep decline in blood volume for 10 minutes, and a slower decline thereafter. In contrast, the rise in blood volume continued for at least 10 minutes after the infusion of the colloids was complete, and a plateau was observed for the remainder of the experiment. The blood volume effect, as measured by area under the curve, was significantly greater in the saline group than the other groups during the infusion time and for the 0–240 minutes time period. The areas under the curve for the two colloid solutions were not significantly different from each other during any time periods. The percent increase in blood volume immediately following the infusions was 76.4±10.0 in the S group, 17.1±3.2 in the HS group, 23.0±10.5 in the D group, and 27.2±6.4 in the HES group. At 30 minutes from the start of the infusion, the mean percent increases in blood volumes were 35.2±9.3 in the S group, 12.3±0.9 in the HS group, 35.9±7.3 in the D group, and 36.8±6.5 in the HES group. At 240 h post‐infusion, the mean percent increases in blood volume were 18.0±9.7 in the S group, 2.9±6.1 in the HS group, 25.6±16.1 in the D group, and 26.6±8.6 in the HES group. The C group had a mean percent change in blood volume of ?3.7±3.4 at the end of the experiment. Conclusions: This study indicates that the rapid administration of saline at clinically relevant doses leads to the largest immediate increase in blood volume, although this change is transient because of rapid redistribution of the fluid. Despite a brief increase in blood volume that was almost 3 times the volume administered, hypertonic saline led to the smallest increase in blood volume post‐infusion. The synthetic colloid solutions increased the blood volume by an amount greater than that infused and the effect was sustained for a longer period of time than seen following crystalloid administration, but the maximum increase in blood volume was significantly less than saline. The measurement of continuous changes in blood volume, using an in‐line hematocrit monitor, was a useful means of assessing the dynamic effects of fluid administration in dogs in a research setting.     

Serologic detection and practical consequences of antigenic diversity among bovine viral diarrhea viruses in a vaccinated herd.

Samples of sera were obtained from 5,725 cows in a semiclosed herd. In each of the preceding 7 years, the herd was vaccinated against bovine viral diarrhea (BVD) with killed virus. Neutralizing antibody tests were done on all samples of sera, using cytopathic virus, BVD-TGAC virus, that was antigenically distinct from the vaccine virus. Most samples of sera had high titers of neutralizing antibodies against BVD-TGAC virus. In 48 samples of sera, neutralizing antibodies were not detected against BVD-TGAC virus, but were detected against the vaccine virus. Neutralizing antibodies against selected noncytopathic BVD viruses were not detected in several samples of serum that had neutralizing antibodies against the vaccine virus and BVD-TGAC virus. Noncytopathic BVD virus was isolated from sera obtained from 3 cows less than 4 years old. Two cows were available for further testing, and persistent infection with BVD virus was confirmed in both cows. The BVD viruses isolated from those cows were not neutralized by several samples of sera. Immunoprecipitation of polypeptides induced by the vaccine virus was done with selected samples of serum. Two patterns of immuno-precipitated viral-induced polypeptides were identified. One pattern was consistent with exposure of cows with live virus. The other pattern was consistent with exposure of cows with only the killed virus vaccine.     

Comparison of cytopathic and noncytopathic isolates of bovine viral diarrhea virus by oligonucleotide fingerprinting.

The molecular technique of RNA fingerprinting was used to characterize the genomes of 5 isolates of bovine viral diarrhea virus (BVDV): 2 viral pairs from the same animal, BVD-ILN/BVD-ILC and BVD-TGAN/BVD-TGAC, and the cytopathic viral prototype, BVD-NADL. Oligonucleotide patterns from the viruses were compared, and unique and overlapping oligonucleotides were identified. A comparison of the fingerprints indicated that the genome of each virus was distinguishable by the T1 RNase oligonucleotide fingerprinting technique. The greatest similarity observed was between oligonucleotides from BVD-ILC and BVD-ILN. Eighteen large oligonucleotides were conserved in all 5 BVDV isolates studied. We found that within a pair of BVDV, the cytopathic fingerprint was different from the noncytopathic fingerprint, indicating that cytopathic and noncytopathic BVDV may be distinct viruses.     

Biochemical study of resistance to imidacloprid in B biotype Bemisia tabaci from Guatemala

Systemic uptake bioassays using excised cotton leaves confirmed resistance to imidacloprid in a Guatemalan population of the tobacco whitefly Bemisia tabaci Gennadius. Polyacrylamide gel electrophoresis of naphthyl esterases identified the insects as B-types. Upon collection from the field, resistance was determined to be 58-fold relative to a susceptible strain originating in the Imperial Valley of California. Resistance levels increased to 126-fold in this population during its continuous exposure to systemically treated cotton. In biochemical investigations, there was no detectable NADPH-dependent mixed function oxidase metabolism of 14C-imidacloprid at any time during the selection process. In contrast, microsomal preparations from housefly abdomens readily produced significant amounts of the mono-hydroxy and olefin derivatives of the parent compound. Detoxification of imidacloprid by housefly MFOs may account for reports of lower toxicity of the insecticide towards this insect compared with whiteflies, despite similar binding properties between imidacloprid and the nicotinic acetylcholine receptors in both species.     

Effects of administration of antimicrobials in feed on growth rate and feed efficiency of pigs in multisite production systems

OBJECTIVE: To evaluate effect of various regimens for administration of antimicrobials in feed on growth rate and feed efficiency (feed/gain) of pigs in multisite production systems. DESIGN: Controlled trial. ANIMALS: 24,099 growing pigs in 3 multisite production systems. PROCEDURE: 10 trials involving various regimens for administration of antimicrobials in feed were evaluated. Trial 1 compared effects of 2 antimicrobial regimens on finishing pig performance. Trials 2 through 10 compared growth rate and feed efficiency of nursery and finishing pigs given antimicrobials in feed with values for control pigs not given antimicrobials. RESULTS: In trial 1, no significant differences were observed between the 2 antimicrobial regimens. In the remaining trials, growth rate of nursery pigs fed antimicrobials was significantly improved, compared with growth rate of control pigs. However, growth rate of finishing pigs and feed efficiency of nursery and finishing pigs were not significantly improved by adding antimicrobials to the feed. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that use of antimicrobials in the feed to promote growth should be limited to the nursery phase in multisite pig production systems. Use of antimicrobials in the feed of finishing pigs should be limited to therapeutic applications in which a diagnosis of bacterial infection susceptible to the antimicrobial to be used has been confirmed.     

Minimum space allowance for transportation of swine by road

Space allowance for animals in transit is a consistent concern in many countries that are developing codes of practice and regulations to assure humane treatment of food producing animals. The minimum space allowance requirements for a broad size range of swine in transit has not been well described or scientifically substantiated. A maximal loading pressure recommendation for pigs weighing from 5 to 250 kg was derived by a consultative process involving the swine transportation industry, animal welfare groups, and a literature review. The recommended maximal loading pressure under ideal conditions for swine loaded in groups can be described as a hoerl model y = (37.53)(0.9969)w(W0.5008), where y = loading pressure in kg body weight/m2 and W = average animal body weight in kilograms.     

Morphologic lesions in type 2 BVDV infections experimentally induced by strain BVDV2-1373 recovered from a field case

Widespread outbreaks of severe acute BVDV, some associated with hemorrhagic syndrome (HS), were reported in Quebec and Ontario in 1993. These outbreaks caused significant economic hardship in infected herds. In the Ontario outbreak 150 dairy, 600 beef and 100 milk and grain fed veal herds were affected with losses estimated at $40000-$10000 per herd in lost animals, milk production, abortions and genetics. Fever, pneumonia, diarrhea, and sudden death occurred in all age groups of cattle. Abortions were frequently observed in pregnant cattle. The viruses associated with this outbreak were determined to be noncytopathic BVDV from the type 2 genotype. All BVDV2 associated with these outbreaks were noncytopathic. One of the viruses isolated from the Ontario outbreak, BVDV2-1373, was used to experimentally induce HS in 5-6 weeks old colostrum deprived, seronegative calves. All animals developed leukopenia and thrombocytopenia within 6-10 days with some developing bloody diarrhea and becoming moribund. Animals were killed for necropsy between 6 and 11 days postinfection. Histopathologically lesions were similar, but more severe, to those seen early on (within first 9 days after superinfection) in animals with experimentally induced mucosal disease (MD). There were no erosions and ulcerations present in the upper digestive tract. In hemorrhages in the mucosa, virus antigen (VA) was present in macrophages of both the lamina propria and the submucosa and in basal epithelial cells. Cells containing VA were vacuolated and separated from each other. The most severe lesions observed in the digestive tract were in the Peyers patches and were characterized by depletion of lymphocytes and proliferation of crypt cells resulting in crypthyperplasia. Apoptotic cells were present in crypts and areas of lymph follicles where viral antigen was detected. Out of the six animals, VA was present in four animals in the pancreas, three animals in the pituitary and in two animals in the adrenal glands. The results suggest that the pathology resulting from acute infection with a highly virulent noncytopathic BVDV2 differs from the pathology observed in classic mucosal disease.     

Toxoplasma gondii in an African crested porcupine (Hystrix cristata).

An adult female crested porcupine (Hystrix cristata) was evaluated for acute onset of neurologic signs including head tilt, circling, and ataxia. She was found dead in her holding area 2 days after initially exhibiting clinical signs. Necropsy was unremarkable. Histopathology of brain tissue revealed the presence of protozoal cysts associated with inflammation as the underlying cause of clinical signs and death. Immunohistochemical staining of brain tissue for Toxoplasma gondii was strongly positive. PCR on fresh brain confirmed T. gondii as the causative organism. An adult male in the same enclosure has demonstrated similar neurologic signs over the past 3 years and has failed to respond to various medical treatments. Clinical disease associated with T. gondii has not been previously reported in this porcupine species or any other Old World porcupines, although there are several reports of clinical toxoplasmosis involving New World porcupine species.     

Accidental intra-auricular artery injection of ceftiofur in two beef steers.

Two beef steers accidentally injected into a branch of the auricular artery with an oil-based formulation of ceftiofur died within 5 minutes of injection. Notable pathologic findings included distention and obstruction of cerebral and cerebellar arteries by a whitish tan material and hemorrhages within meningeal spaces, the choroid plexus, cerebrum, and cerebellum. Lipid material was identified within cerebral blood vessels in frozen sections stained with oil red O. This report describes an unusual case of brain ischemia in beef cattle.