A sensitive, reproducible, and economic real-time reverse transcription PCR detecting avian metapneumovirus subtypes A and B.

Use of real-time PCR is increasing in the diagnosis of infectious disease due to its sensitivity, specificity, and speed of detection. These characteristics make it particularly suited for the diagnosis of viral infections, like avian metapneumovirus (AMPV), for which effective control benefits from continuously updated knowledge of the epidemiological situation. Other real-time reverse transcription (RT)-PCRs have been published based on highly specific fluorescent dye-labeled probes, but they have high initial cost, complex validation, and a marked susceptibility to the genetic variability of their target sequence. With this in mind, we developed and validated a SYBR Green I-based quantitative RT-PCR for the detection of the two most prevalent AMPV subtypes (i.e., subtypes A and B). The assay demonstrated an analytical sensitivity comparable with that of a previously published real-time RT-PCR and the ability to detect RNA equivalent to approximately 0.5 infectious doses for both A and B subtypes. The high efficiency and linearity between viral titer and crossing point displayed for both subtypes make it suited for viral quantification. Optimization of reaction conditions and the implementation of melting curve analysis guaranteed the high specificity of the assay. The stable melting temperature difference between the two subtypes indicated the possibility of subtyping through melting temperature analysis. These characteristics make our assay a sensitive, specific, and rapid tool, enabling contemporaneous detection, quantification, and discrimination of AMPV subtype A and B.

An outbreak of blindness due to retinopathy in nine flocks of guinea fowl.

Blindness was observed in 10- to 14-day-old guinea fowl. The incidence ranged from 25% to 80% in nine flocks within a total population of 110,000 guinea fowls. Clinical signs of blindness in birds included aimless wandering, failure to find feed and water, lateral recumbency, loss of weight, and increased mortality. The birds lacked papillary reflexes to light, and there were no gross lesions in the eyes. Histologically there was degeneration and disorganization of photoreceptors in the retina. The guinea fowl came from three different breeder sources but all of the birds were given the same feed. The condition was not observed in the subsequent flocks that came from the same breeder sources but that were given different feed. Based on these observations, toxicity of an unknown ingredient in the feed is suspected as the cause of blindness in the guinea fowl.

Gamma and Deltacoronaviruses in quail and pheasants from Northern Italy1.

In view of the restricted knowledge on the diversity of coronaviruses in poultry other than chicken, this study aimed to investigate the genetic diversity of coronaviruses in quail, pheasant, and partridge from two regions of Northern Italy. To this end, pools of tracheal and cloacal swabs from European quail (Coturnix Coturnix) and intestinal tract from pheasants (Phasianus Colchicus) and partridge (Perdix Perdix) flocks, with or without enteric signs, were collected during 2015. Avian coronavirus (Gammacoronavirus) was detected in quail not vaccinated against Infectious Bronchitis Virus (IBV) and in pheasants vaccinated with an IBV Massachusetts serotype. Based on DNA sequences for the gene encoding the S protein, the avian coronaviruses detected in the quail and pheasant are related to the IBV 793B and Massachusetts types, respectively. However, RNA-dependent RNA polymerase (RdRp) analyses showed the susceptibility of quail also to Deltacoronaviruses, suggesting that quail and pheasant avian coronaviruses share spike genes identical to chicken IBV spike genes and quail might host Deltacoronavirus.

Genome sequence analysis of a distinctive Italian infectious bursal disease virus.

In a recent study, an emerging infectious bursal disease virus (IBDV) genotype (ITA) was detected in IBDV-live vaccinated broilers without clinical signs of infectious bursal disease (IBD). VP2 sequence analysis showed that strains of the ITA genotype clustered separately from vaccine strains and from other IBDV reference strains, either classic or very virulent. In order to obtain a more exhaustive molecular characterization of the IBDV ITA genotype and speculate on its origin, genome sequencing of the field isolate IBDV/Italy/1829/2011, previously assigned to the ITA genotype, was performed, and the sequences obtained were compared to the currently available corresponding sequences. In addition, phylogenetic and recombination analyses were performed. Interestingly, multiple amino acid (AA) sequence alignments revealed that the IBDV/Italy/1829/2011 strain shared several AA residues with very virulent IBDV strains as well as some virulence markers, especially in the VP1 protein. Nevertheless, sequence analysis demonstrated the presence of several residues typical of IBDV strains at a low degree of virulence in the IBDV/Italy/1829/2011 strain. Although homologous recombination and reassortant phenomena may occur naturally among different IBDV strains, no evidence of those events was found in the genome of the IBDV/Italy/1829/2011 strain, which was confirmed to be a genetically distinctive IBDV genotype.

Reversion to virulence of a subtype B avian metapneumovirus vaccine: is it time for regulators to require availability of vaccine progenitors?

Empirically derived live avian metapneumovirus (AMPV) vaccines developed during the late 80s and early 90s have generally performed well in controlling turkey rhinotracheitis. Nonetheless, unstable attenuation was previously demonstrated in an AMPV subtype A vaccine. Until now this had not been investigated in subtype B vaccines due to lack of any similar availability of a vaccine progenitor or its sequence. The publication of the full genome sequence for the VCO3 vaccine progenitor facilitated a conclusive investigation of two AMPVs isolated from poults on a farm which had been vaccinated with VCO3 derived vaccine. Full genome sequencing of the isolates and their comparison to sequences of the vaccine and its progenitor, confirmed their vaccine origin. After determining the absence of extraneous infectious agents, one of these virus isolates was inoculated into 1-day-old turkeys in disease secure isolators and shown to cause disease with a severity similar to that caused by virulent field virus. This suggests that instability in live AMPV vaccines may be generalized and highlights the need for availability of vaccine progenitor sequences for the field assessment of all live viral vaccines.

In vitro antiviral activity of chestnut and quebracho woods extracts against avian reovirus and metapneumovirus.

Field evidences have suggested that a natural extract, containing tannins, could be effective against poultry enteric viral infections. Moreover previous studies have shown that vegetable tannins can have antiviral activity against human viruses. Based on this knowledge three different Chestnut (Castanea spp.) wood extracts and one Quebracho (Schinopsis spp.) wood extract, all containing tannins and currently used in the animal feed industry, were tested for in vitro antiviral activity against avian reovirus (ARV) and avian metapneumovirus (AMPV). The MTT assay was used to evaluate the 50% cytotoxic compounds concentration (CC(50)) on Vero cells. The antiviral properties were tested before and after the adsorption of the viruses to Vero cells. Antiviral activities were expressed as IC(50) (concentration required to inhibit 50% of viral cytopathic effect). CC(50)s of tested compounds were > 200 microg/ml. All compounds had an extracellular antiviral effect against both ARV and AMPV with IC(50) values ranging from 25 to 66 microg/ml. Quebracho extract had also evident intracellular anti-ARV activity (IC(50) 24 microg/ml). These preliminary results suggest that the examined vegetable extracts might be good candidates in the control of some avian virus infections. Nevertheless further in vivo experiments are required to confirm these findings.

Renal response to atrial peptides is reduced in experimental nephrosis.

The aim of this study was to evaluate the renal response to atrial extracts (AE) and synthetic atrial natriuretic factor (ANF) in control rats and in rats with experimental nephrotic syndrome (NS). NS was obtained by a single intravenous injection of adriamycin (7.5 mg/kg). Bolus injection of AE from normal or NS rats resulted in marked increase of diuresis and natriuresis in bioassay control rats (AE from normal rats, urine flow rate, 14.87 +/- 2.94 to 186.18 +/- 55.86 microliters/min; Na excretion, 0.68 +/- 0.26 to 21.80 +/- 5.45 mu eq/min; AE from NS, urine flow rate, 13.49 +/- 4.30 to 167.14 +/- 51.44 microliters/min; Na excretion, 0.98 +/- 0.57 to 20.71 +/- 9.76 mu eq/min). In contrast, blunted diuretic (from 11.26 +/- 3.05 to 65.20 +/- 27.30 microliters/min) and natriuretic (from 0.58 +/- 0.15 to 4.52 +/- 1.59 mu eq/min) effect was observed when AE were injected in rats with NS. Injection of the vehicle in which AE were dissolved or ventricular extracts did not increase urinary flow rate or Na excretion in both control and NS animals. Bolus injection of synthetic ANF (Arg-101-Tyr-126) induced marked diuretic and natriuretic response in control but not in NS rats. Similar results were obtained when AE were infused by constant infusion in control or in NS bioassay rats. AE given by constant infusion induced comparable increase in glomerular filtration rate (GFR) over basal values both in control and NS animals (controls, 39%; NS rats, 40%).(ABSTRACT TRUNCATED AT 250 WORDS)

Tertatolol ameliorates renal function in rats with chronic renal failure.

Tertatolol is a new beta-blocking agent which induces renal vasodilation in experimental animals and humans and increases glomerular filtration rate (GFR), diuresis and natriuresis. The mechanisms underlying renal effects of tertatolol are not known. Our aims were to establish whether tertatolol influences renal function by a systemic or by an intrarenal effect and to assess whether tertatolol could maintain GFR in chronic renal failure. Tertatolol but not propranolol when given as i.v. bolus injection at the dose of 25 and 50 micrograms/kg. b.w. induces a significant increase in GFR and perfusate flow rate (PFR) in an isolated perfused kidney model [GFR: tertatolol, 25 micrograms/kg; preinjection: 0.477 +/- 0.077 ml/min/g of kidney; 30 min postinjection: 0.996 +/- 0.114 ml/min/g of kidney. Tertatolol (50 micrograms/kg) preinjection: 0.517 +/- 0.040 ml/min/g of kidney; 30 min postinjection: 0.879 +/- 0.035 ml/min/g of kidney. Propranolol (500 micrograms/kg) preinjection: 0.574 +/- 0.045 ml/min/g of kidney; 30 min postinjection: 0.538 +/- 0.029 ml/min/g of kidney. PFR: tertatolol, 25 micrograms/kg, preinjection: 30.00 +/- 0.79 ml/min; 30 min postinjection: 36.20 +/- 2.58 ml/min. Tertatolol (50 micrograms/kg) preinjection: 29.30 +/- 1.44 ml/min; 30 min postinjection: 38.01 +/- 1.87 ml/min. Propranolol (500 micrograms/kg) preinjection: 28.70 +/- 1.04 ml/min; 30 min postinjection: 28.30 +/- 0.91 ml/min]. In the same preparation tertatolol significantly increases urine flow rate and Na+ excretion [urine flow rate: tertatolol (25 micrograms/kg) preinjection: 28.28 +/- 4.10 microliter/min; 60 min postinjection: 38.23 +/- 6.74 microliter/min. Tertatolol (50 micrograms/kg) preinjection: 24.02 +/- 0.63 microliter/min; 60 min postinjection: 33.18 +/- 2.07 microliter/min.(ABSTRACT TRUNCATED AT 250 WORDS)

Blunted excretory response to atrial natriuretic peptide in experimental nephrosis.

Adriamycin (ADR) nephrosis and a model of unilateral ADR-induced proteinuria were produced in Sprague-Dawley (S.D.) rats to investigate the mechanism of sodium retention by the nephrotic kidney. Plasma volume, as measured by the dilution principle using radioiodinated serum albumin, was significantly higher in nephrotic animals than in control ones (NS: 69.61 +/- 15.02: control: 47.05 +/- 5.32 ml/kg: P less than 0.01). Similarly plasma levels of immunoreactive ANP (iANP) were significantly higher in nephrotic animals compared to controls (NS 104.22 +/- 36.41: control 59.94 +/- 20.88 pg/ml; P less than 0.05). Using the unilateral model we found a markedly reduced diuretic and natriuretic response to the infusion of synthetic rat atrial natriuretic peptide (ANP 1-28) in proteinuric kidney but not in contralateral kidney, despite a comparable increase in glomerular filtration rate. To explain the blunted diuresis and natriuresis in the presence of normal glomerular response to ANP, we investigated the possibility of an abnormality at post-glomerular level by studying ANP receptor density and affinity of the inner stripe of outer medulla and the inner medulla in ADR-and vehicle-treated rats. The inner stripe of outer medulla and the inner medulla receptor density and affinity were not significantly different in ADR rats as compared to animals given the vehicle alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Central prolactin infusions stimulate maternal behavior in steroid-treated, nulliparous female rats.

A series of experiments were conducted to determine whether and under what conditions central prolactin (PRL) administration would stimulate the onset of maternal behavior in female rats and to identify possible neural sites of PRL action. In each experiment ovariectomized, nulliparous rats whose endogenous PRL levels were suppressed with bromocriptine were tested for maternal behavior toward foster young. In experiments 1, 2, and 4, females were also exposed to pregnancy-like levels of progesterone (days 1-11) followed by estradiol (days 11-17). In experiment 1 infusions (days 11-13) of four doses of ovine PRL (400 ng, 2 micrograms, 10 micrograms, or 50 micrograms, but not 80 ng) into the lateral ventricle resulted in a rapid onset of maternal behavior (behavioral testing, days 12-17). The stimulatory action of these doses of PRL appears to be central, since subcutaneous injections of 50 micrograms of ovine PRL failed to affect maternal responsiveness (experiment 2). Experiment 3 indicated that the stimulatory effect of intracerebroventricularly administered PRL is steroid dependent. Infusions of either 10 micrograms of ovine PRL or 10 micrograms of rat PRL failed to induce maternal behavior in nonsteroid-treated animals. In the final experiment (no. 4) bilateral infusions of 40 ng of ovine PRL into the medial preoptic area of steroid-treated rats resulted in a pronounced stimulation of maternal behavior. These findings demonstrate a central site of PRL action in the stimulation of maternal responsiveness and point to the medial preoptic area as a key neural site for PRL regulation of maternal behavior.