Plant poisonings and mycotoxicoses of importance in horses in southern Africa

Well-known plant poisonings such as 'dunsiekte' (seneciosis) and 'jaagsiekte' (crotalariosis) of horses in southern Africa are briefly reviewed. Relatively unfamiliar mycotoxicoses such as stachybotryotoxicosis and perennial rye grass staggers and potentially occurring exotic intoxications such as equine nigropallidal encephalomalacia and ergot alkaloid poisoning are also discussed. This article is aimed at informing the southern African equine practitioner about probable poisonings that might occur locally in horses.     

Avian paramyxovirus serotype 1 isolates from the spinal cord of parrots display a very low virulence

The spinal cord of 32 psittacines suffering from proventricular dilatation disease (PDD) was investigated. In six cases, a virus was isolated which upon electron microscopic examination revealed morphological details typical of members of the Paramyxoviridae. All isolates were subsequently characterized as avian paramyxovirus serotype 1 (APMV-1) by type-specific polyclonal antisera. According to their reactivity with APMV-1 specific monoclonal antibodies, the six isolates shared epitopes within the haemagglutinin-neuraminidase spike protein, distinct from pigeon-type paramyxoviruses and the LaSota vaccine strain. This grouping was further corroborated by properties of the haemagglutinin: all isolates showed a very thermosensitive haemagglutination activity and were rapid eluters. Virulence of the APMV-1 isolates in 1-day-old specific pathogen free (spf) chicken was very low, with intracerebral pathogenicity indices between 0 and 0.1. In embryonated spf chicken eggs, psittacine isolates replicated to high titres (10(8.6)-10(10.7) EID50/ml). However, they exhibited a reduced lethality over an observation time of 7 days (10(6.1)-10(8.3) ELD50/ml). In a haemagglutination inhibition test with parrot sera from birds with no history of APMV-1 vaccination, sera reacted preferentially with two isolates compared with APMV-1 vaccine strains LaSota and B1. The other four isolates exhibited a differentiated reaction pattern with the parrot sera, indicating an antigenic inhomogeneity. This is the first report of isolating very low virulent APMV-1 from neuronal tissue of parrots and implications for a possible role in slow progressing disease will be discussed.     

Experimental model of swine pneumonic pasteurellosis using crude Actinobacillus pleuropneumoniae cytotoxin and Pasteurella multocida given endobronchially.

This study was designed to develop and characterize a swine pneumonic pasteurellosis model by concurrent introduction of Pasteurella multocida type A and Actinobacillus pleuropneumoniae crude cytotoxin. After a series of preliminary experiments, a combination of 4 x 10(9) P. multocida and 4,000 toxic units of A. pleuropneumoniae crude cytotoxin was determined to produce optimal results. A total of 48 pigs were divided into four groups of 12 pigs each. The control group received buffered saline only. Four pigs from each group were randomly selected for necropsy 3, 7 and 14 days postinoculation (PI). Inoculation of pigs with P. multocida and A. pleuropneumoniae cytotoxin (group 1) resulted in moderate to severe pneumonia. Pasteurella multocida was isolated from pneumonic lesions, grossly normal lung, and bronchial lymph nodes of all group 1 pigs throughout the 14 day experimental period. Pathological changes typical of field cases of swine pneumonic pasteurellosis were produced. Pigs inoculated with P. multocida alone (group 2) had pneumonic lesions and P. multocida was reisolated from lungs at three days PI. Pasteurella multocida was not isolated from these pigs at 7 and 14 days PI, except for one pig in which an abscess developed in the thorax. Pulmonary lesions induced by A. pleuropneumoniae crude cytotoxin alone (group 3) were transient and resolved by seven days PI. Group 1 pigs had significantly greater lung lesion volumes than group 2 and 3 pigs at 3, 7 and 14 days PI. Statistical analysis indicated a significant interactive effect of P. multocida and A. pleuropneumoniae cytotoxin on the development of lung lesion volumes at 7 and 14 days PI (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Ketoprofen and phenylbutazone attenuation of PAF-induced lung inflammation in calves

The purposes of this study were: (1) to investigate which arachidonic acid metabolites contributed to platelet-activating factor (PAF) induced pulmonary dysfunction; and (2) to compare the effect of two non-steroidal anti-inflammatory drugs, phenylbutazone and ketoprofen in a model of PAF-induced reversible lung inflammation in six calves. In placebo and phenylbutazone groups, PAF infusion induced significant dysfunctions in the pattern of breathing, mechanics of breathing and gas exchange. These dysfunctions were prevented by ketoprofen pretreatment, except for the mechanics of breathing which was moderately but significantly altered by the PAF challenge. In all calves, leukotriene (LT) B4 plasma concentrations did not significantly increase above baseline values at any time. Prostaglandin (PG) E2 plasma concentrations showed a minor significant increase in phenylbutazone pretreated calves (55.8 +/- 25.8 pg/mL from 36.7 +/- 16.13 pg/mL). Thromboxane (TX) B2 plasma concentration was significantly increased during PAF challenge in placebo- and phenylbutazone-pretreated groups, but not in ketoprofen-pretreated calves (1580.0 +/- 1370 from 42.7 +/- 10.7 pg/mL; 2340 +/- 477 from 63 +/- 32 pg/mL; and 36.5 +/- 4.12 from 39.3 +/- 12.0 pg/mL, respectively). These data suggest that TXA2 is an important cyclooxygenase metabolite of arachidonic acid produced in response to PAF and that ketoprofen (intramuscular injection, 3 mg/kg) is more effective than phenylbutazone (intramuscular injection, 10 mg/kg) in preventing respiratory dysfunctions induced by the PAF challenge 30 min after drug administration. Ketoprofen did not suppress totally the PAF-induced changes in mechanics of breathing, which suggests that PAF or a secondary release of mediators could have a direct action on airway smooth muscle.     

Insulin-like growth factor binding protein-3: its biological effect on bovine granulosa cells

This study was aimed at testing the hypothesis that insulin-like growth factor binding protein (IGFBP)-3 can modulate hormone-dependent differentiation of granulosa cells in vitro. Granulosa cells from small (1 to 5 mm) follicles were collected from cattle, cultured for 2 d in medium containing 10% fetal calf serum, washed, and then treated for an additional 2 d in serum-free medium with follicle-stimulating hormone (FSH) (50 ng/ml), recombinant human IGF-I (0, 1.3, 4.0, or 13.3 nM), or recombinant human IGFBP-3 (0 to 4.26 nM). In one series of experiments, IGFBP-3 (0.53 and 2.13 nM) inhibited (51% to 92% decreases; P < 0.05) progesterone and estradiol production induced by 1.3 nM of IGF-I, but did not influence (P > 0.10) granulosa cell numbers or steroidogenesis in the absence of IGF-I. Only 4.26 nM of IGFBP-3 inhibited (by 35%) the increase in granulosa cell numbers induced by 1.3 nM of IGF-I. In another series of experiments, 13.3 nM of IGF-I, but not 4.0 nM of IGF-I, was able to completely overcome the inhibitory effect of 4.26 nM of IGFBP-3 on estradiol production. The increase in cell numbers induced by 4.0 and 13.3 nM of IGF-I was attenuated (P < 0.001) by 4.26 nM of IGFBP-3. In a third series of experiments, IGFBP-3 inhibited 125I-IGF-I binding to granulosa cells. These results indicate that IGFBP-3 has a pronounced inhibitory effect on IGF-I action in cultured bovine granulosa cells, and that this inhibitory effect is likely attributable to IGFBP-3 binding/sequestering IGF-I. Thus, IGFBP-3 may play a significant role in regulating granulosa cell proliferation and steroidogenesis during follicular development in cattle.     

Use of a water hardness test kit to measure serum calcium concentration in cattle

OBJECTIVE: To determine whether a commercially available water hardness test kit could be used to measure total serum calcium concentration and diagnose hypocalcemia in dairy cows. DESIGN: Prospective study. ANIMALS: 30 dairy cows from 19 commercial herds. PROCEDURE: Serum calcium concentration was determined using a water hardness test kit and a standard, laboratory-based method. Simple linear regression was used to determine whether there was a linear relationship between results of the 2 methods, and Spearman's rank correlation was used to calculate correlation between measurements. Sensitivity, specificity, and predictive values of using test kit-derived values for diagnosis of hypocalcemia (laboratory value < 8 mg/dl) were calculated. RESULTS: There was a high correlation and significant linear relationship between results of the 2 methods. Sensitivity, specificity, predictive value of a positive test result, and predictive value of a negative test result were 100, 73, 86, and 100%, respectively. Accuracy was improved by using a test kit-derived calcium concentration of 7 mg/dl as the cut-off for determining hypocalcemia. CLINICAL IMPLICATIONS: Results indicate that a commercially available water hardness test kit can be used as a rapid, inexpensive method of estimating serum calcium concentrations and diagnosing hypocalcemia in dairy cattle. However, the test is not practical for cow-side use, because blood samples must be centrifuged to obtain serum for use in the test kit.     

Effect of dietary n-6-to-n-3 fatty acid ratio on complete blood and total white blood cell counts, and T-cell subpopulations in aged dogs

OBJECTIVE: To determine effect of diets with variable n-6-to-n-3 fatty acid (FA) ratio on CD4+ and CD8+ T-lymphocyte subpopulations, and on results of routine laboratory analyses (CBC and total WBC count, serum biochemical analyses, and urinalysis). ANIMALS: 20 healthy, aged (9.5 to 11.5 years old) female Beagles. PROCEDURE: Dogs were fed 1 of 3 diets that contained 6% fat by weight but differed in amounts of n-6 and n-3 FA. For 11 weeks, 6 dogs were fed a low concentration of n-3 FA (ratio, 31:1), 7 were fed a medium concentration (5.4:1), and 7 were fed a high concentration (1.4:1). Preprandial blood and urine samples were collected before beginning the study and at 8 weeks for evaluation of laboratory variables. Before and at 3, 6, and 8 weeks during the study, blood was drawn for total WBC and lymphocyte counts and for characterization of T-cell subpopulations. At 8 and 10 weeks, dogs were vaccinated with keyhole limpet hemocyanin suspension. Blood was drawn 4 days after each vaccination, and lymphocytes were isolated for flow cytometry. Effects of diet and vaccination on each variable were determined. RESULTS: After vaccination, total lymphocyte count increased and CD4+ T lymphocyte count and the CD4(+)-to-CD8+ ratio decreased in dogs consuming the diet with n-6-to-n-3 FA ratio of 1.4:1. CONCLUSION: Feeding a diet with n-6-to-n-3 FA ratio of 1.4:1 had significant effects on CD4+ T lymphocytes in healthy, aged Beagles after vaccination.     

In vitro dose-dependent effects of enrofloxacin on equine articular cartilage.

OBJECTIVE: To determine whether enrofloxacin has detrimental, dose-dependent effects on equine articular cartilage in vitro. ANIMALS: Cartilage explants were developed from 6 healthy horses between 0 and 96 months old. PROCEDURE: Patellar cartilage explants were incubated in 5 concentrations of enrofloxacin (2 microg/ml, 10 microg/ml, 1,000 microg/ml, 10,000 microg/ml, and 50,000 microg/ml) for 72 hours. Proteoglycan synthesis (Na35SO4 incorporation for 24 hours), proteoglycan degradation (Na35SO4 release for 72 hours), endogenous proteoglycan content (dimethylmethlene blue assay), and total protein content were determined. Cartilage explants were evaluated by use of histomorphologic and histomorphometric techniques (toluidine blue stain) for cytologic and matrix characteristics. Quantitative data were analyzed with a one-way ANOVA to compare results among various enrofloxacin concentration groups and the control group. A general linear model was used to determine whether age had an effect. RESULT: Proteoglycan synthesis was excellent in control specimens and in specimens incubated in low concentrations of enrofloxacin (2 microg/ml and 10 microg/ml). High concentrations of enrofloxacin (> 1,000 microg/ml) effectively eliminated proteoglycan synthesis regardless of horse age. Proteoglycan degradation at low concentrations (2 microg/ml and 10 microg/ml) was not different than control. High concentrations of enrofloxacin (> 1,000 microg/ml) caused significant degradation. Different concentrations of enrofloxacin did not affect endogenous proteoglycan. High concentrations of enrofloxacin were associated with a significant increase in number of pyknotic nuclei. CONCLUSION: Concentrations of enrofloxacin that might be achieved following systemic administration did not suppress chondrocyte metabolism in vitro. High concentrations of enrofloxacin (> 1,000 microg/ml) were toxic to chondrocytes.     

Nucleotide sequence of UK and Australian isolates of feline calicivirus (FCV) and phylogenetic analysis of FCVs.

We have determined the first complete genome sequence and capsid gene sequences of feline calicivirus (FCV) isolates from the UK and Australia. These were compared with other previously published sequences. The viruses used in the comparisons were isolated between 1957 and 1995 from various geographical locations and obtained from cats showing a range of clinical signs. Despite these diverse origins, comparisons between all strains showed a similar degree of sequence variation within both ORF1 (non-structural polyprotein) and ORF2 (major capsid protein) (amino acid distances of 7.7-13.0% and 8.8-18.6%, respectively). In contrast, ORF3 (putative minor structural protein) sequences indicated a more heterogenous distribution of FCV relatedness (amino acid distances of 1.9-17.9%). Phylogenetic analysis suggested that, unlike some other caliciviruses, FCV isolates within the current data set fall into one diverse genogroup. Within this group, there was an overall lack of geographic or temporal clustering which may be related to the epidemiology of FCV infection in cats. Analysis of regions of variability in the genome has shown that, as well as the previously identified variable regions in ORF2, similar domains exist within ORFs 1 and 3 also, although to a lesser extent. In ORF1, these variable domains largely fall between the putative non-structural protein functional domains.