Spread of porcine circovirus associated disease (PCVAD) in Ontario (Canada) swine herds: Part II. Matched case-control study

Background

The emergence of porcine circovirus associated disease (PCVAD) was associated with high mortality in swine populations worldwide. Studies performed in different regions identified spatial, temporal, and spatio-temporal trends as factors contributing to patterns of the disease spread. Patterns consistent with spatial trend and spatio-temporal clustering were already identified in this dataset. On the basis of these results, we have further investigated the nature of local spread in this report. The primary objective of this study was to evaluate risk factors for incidence cases of reported PCVAD.

Results

A time-matched case-control study was used as a study design approach, and conditional logistic regression as the analytical method. The main exposure of interest was local spread, which was defined as an unidentified mechanism of PCVAD spread between premises located within 3 kilometers of the Euclidean distance. Various modifications of variables indicative of local spread were also evaluated. The dataset contained 278 swine herds from Ontario originally sampled either from diagnostic laboratory submissions or directly from the target population. A PCVAD case was defined on the basis of the producer's recall. Existence of apparent local spread over the entire study period was confirmed (OR = 2.26, 95% CI: 1.06, 4.83), and was further identified to be time-varying in nature - herds experiencing outbreaks in the later part of the epidemic were more likely than control herds to be exposed to neighboring herds experiencing recent PCVAD outbreaks. More importantly, the pattern of local spread was driven by concurrent occurrence of PCVAD on premises under the same ownership (OR_{EXACTwithin ownership} = 25.6, 95% CI: 3.4, +inf; OR_{EXACToutside ownership} = 1.3, 95% CI: 0.45, 3.3). Other significant factors included PRRSv status of a herd (OR_EXACT = 1.9, 95% CI: 1.0, 3.9), after adjusting for geographical location by including the binary effect of the easting coordinate (Easting > 600 km = 1; OR_EXACT = 1.8, 95% CI: 0.5, 5.6).

Conclusions

These results preclude any conclusion regarding the existence of a mechanism of local spread through airborne transmission or indirectly through contaminated fomites or vectors, as simultaneous emergence of PCVAD could also be a result of concurrent change in contributing factors due to other mechanisms within ownerships.

     

Effects of the beehive type and queen-bee descent on the development of the bee-diseases at apiaries

An increased occurrence of disease at various members of the honeybee brood (queen-bee, workers, and drones) settled in the beehive, become evident recently. It is already known that various factors, primary ecological, determine disease development. The aim of the study was to discover which diseases at apiaries corresponds to similar ecological conditions at different beehive types. Effects of the following factors were studied: beehive type and building material, type and descent of the queen-bee, variable of the environmental conditions. All honeybee broods, belonging to the European Apis mellifera carnica rase, used identical honeyfull plants pastures.     

In vivo expression and function of recombinant GTPCH I in the rabbit carotid artery

Tetrahydrobiopterin (BH4) is an essential co-factor for endothelial nitric oxide synthase enzymatic activity. GTP cyclohydrolase I (GTPCH I) is the rate-limiting enzyme in BH4 synthesis. This study set out to test the hypothesis that in vivo gene transfer of GTPCH I to endothelial cells could increase bioavailability of BH4, enhance biosynthesis of nitric oxide and thereby enhance endothelium-dependent relaxations mediated by nitric oxide. In vivo gene transfer was carried out by adenovirus (Ad)-mediated delivery into rabbit carotid arteries. Each artery was transduced by 20-min intraluminal incubation of 10(9) plaque-forming units of Ad-encoding GTPCH I (AdGTPCH) or beta-galactosidase as a control. The rabbits were euthanized 72 h later, and vasomotor function of isolated arteries was assessed by isometric force recording. GTPCH I enzymatic activity, BH4, and oxidized biopterin levels were detected with the use of HPLC, and cGMP was measured with the use of radioimmunoassay. Expression of recombinant proteins was detected predominantly in endothelial cells. Both GTPCH I activity and BH4 levels were increased in arteries transduced with AdGTPCH. However, contraction to phenylephrine (10(-5) to 10(-9) M), endothelium-dependent relaxation to acetylcholine (10(-5) to 10(-9) M) and cGMP levels were not significantly affected by increased expression of GTPCH I. Our results suggest that expression of GTPCH I in vascular endothelium in vivo increases intracellular concentration of BH4. However, under physiological conditions, it appears that this increase does not affect nitric oxide production in endothelial cells of the carotid artery.     

Virilizing adrenal cancer and bail-out nephrectomy

We report a rare case of virilizing adrenal cancer with tumorous invasion of the left renal vein in which a retroperitoneal adrenalectomy with bail-out nephrectomy was performed. A tumor thrombus infiltrated the wall of the left adrenal vein and extended into the left renal vein. Initially, a kidney sparing procedure with partial tangential excision of the involved renal vein wall was performed. After positive vein margins were confirmed with intraoperative histology, the indication for nephrectomy was made. To the authors' awareness, this is the first report of a virilizing adrenal cancer with a tumor thrombus infiltration of the renal vein and surgical tendency for kidney preservation.     

Thickness of masticatory mucosa in the human hard palate and tuberosity dependent on gender and body mass index

The aim of this study was to clinically determine the thickness of masticatory mucosa in the hard palate and tuberosity as potential donor sites for subepitelial grafts for ridge augmentation procedures of small and moderate alveolar ridge defects to improve aesthetics of a pontic area of fixed partial dentures. In 102 periodontally healthy fully dentate subjects the thickness of mucosa was assessed by bone sounding with a periodontal probe. Twenty measurement points were defined, 18 on hard palate located on 3 lines running at different distances parallel to gingival margin and 2 on tuberosity. Data were analysed to determine differences between gender and different body mass index using t-test. The mucosa on the hard palate was significantly thicker than on the tuberosity. The thickest mucosa was registered on the second and the third line behind canines and on all 3 lines behind the first premolar. These areas are recommended as potential donor sites. Males had significantly thicker mucosa than females (p < 0.01), except for the sites behind the first molar (p > 0.05) where the mucosa was the thinnest in the both gender, which was attributed to the protuberance of the palatal root of the first molar. The same was with the body mass index. Therefore canine-premolar palatal region is recommended for harvesting free subepitelial grafts for moderate augmentation of alveolar ridges for achieving optimal aesthetics of the pontic area.     

Functional adaptation and remodeling of pulmonary artery in flow-induced pulmonary hypertension

Patients with left-to-right shunt congenital heart disease may develop pulmonary hypertension. Perioperative mortality of these patients is high due to abnormal vasoreactivity of the pulmonary artery (PA). We studied the changes in the PA induced by high pulmonary blood flow in rats with aortocaval fistula. Eight weeks after surgery, morphological changes of the PA were studied and vasomotor function was assessed by isometric force recording. Expression of endothelial nitric oxide (NO) synthase (eNOS), VEGF, and cyclooxygenase-2 (COX-2) proteins and levels of cGMP in the PA were analyzed. Rats with high pulmonary blood flow developed pulmonary hypertension, medial thickening, and increasing of internal elastic lamina and basement membrane in the PA. When compared with sham-operated animals, rats with fistula had significantly increased contractions in the PA, whereas relaxations to acetylcholine and NO donor were reduced. Concentrations of cGMP were reduced in the PA of rats with pulmonary hypertension (18.4 +/- 3.3 vs. 9.4 +/- 1.7 pmol/mg protein; P = 0.04). The altered vasomotor function was normalized by treatment with indomethacin. The PA of rats with fistula expressed higher levels of eNOS, phosphorylated eNOS, and COX-2. Sustained high PA blood flow in rats causes pulmonary hypertension that is morphologically and functionally identical with patients with flow-induced pulmonary hypertension. Abnormal vasomotor function of the PA in these animals appears to be mediated by reduced availability and the biological effect of endogenous NO and the high production of vasoconstrictor prostanoids. Increased eNOS and phosphorylated eNOS are most likely the adaptive changes in response to an increase in PA pressure secondary to high blood flow.