Potentiation of immune response of live lentogenic Newcastle disease vaccine using adjuvant

Tropical Animal Health and Production -     

Velogenic Newcastle Disease Virus in Captive Wild Birds

Newcastle disease virus (NDV) was isolated from the faeces of seven different species of clinically healthy captive wild birds. All seven NDV isolates were characterized as velogenic, based on the mean death time in embryonated hens' eggs and the intracerebral pathogenicity index in day-old chicks. Three of the isolates were placed in group C₁ based on the reactions with monoclonal antibodies. The role of captive wild birds in the epidemiology of Newcastle disease is briefly discussed.     

ISOLATION OF NEWCASTLE DISEASE VIRUS FROM AN INDIAN HOUSE CROW

Tropical Animal Health and Production -     

Sedative and analgesic effects of medetomidine in beagle dogs infected and uninfected with heartworm

The sedative and analgesic effects of medetomidine were evaluated in heartworm-infected (HW+) and uninfected (HW–) beagle dogs by intravenous (IV) and intramuscular (IM) administration of 30 µg/kg and 40 µg/kg doses, respectively. Posture, response to noise and the pedal reflex were monitored. A procedure for mock radiographic positioning was performed to evaluate its overall clinical use. Observation times were 0, 15, 30, 60, 90, 120 and 180 min. In addition, the times from injection until the dog could not stand on its feet (down time), from lateral to sternal recumbency (sternal recumbency time), and from sternal recumbency to rising again (rising time) were also noted.Medetomidine produced rapid sedation and analgesia by both routes. Down times for the IM and IV routes were similar, which verified the manufacturer's recommended doses. The HW+ dogs had shorter down times, probably owing to increased blood flow to the brain caused by adrenergic alpha-2 activity. Sternal recumbency and rising times did not differ between the groups, suggesting a similar metabolism. Sedation and analgesia were adequate for performing the procedure in all dogs. HW– dogs showed less resistance to handling during the procedure than HW+ dogs. Overall, medetomidine seems to be a suitable agent for short-term chemical restraint in dogs, even with subclinical heartworm infestation.     

Assessment of smooth muscle function in Sesbania drummondii toxicosis in Gallus domesticus

An in vitro assessment based on tissue responsiveness to 2 agonists-histamine and carbachol-was made on smooth muscle activity in chickens experimentally poisoned with sesbania. Crude extracts of Sesbania drummondii were prepared and 2 dosage levels, 0.25% and 0.5% of body weight, were used. The birds were dosed orally with the extract for 3 consecutive days, and on the 4th day segments of ileum and lung were collected from each bird. The isometric contractions of each tissue, produced by the addition of histamine or carbachol in graded concentrations, were recorded. The cumulative concentration-effect curves for the tissues to the agonists were constructed and compared with respective control curves. The results indicated the responsiveness of the tissues in the treated groups was significantly decreased, compared with that of tissues in the controls. Responses of both intestinal and parenchymal strips in the chickens given the higher dosage (0.5%) were decreased significantly, whereas in those given the smaller dosage (0.25%), only parenchyma had a significant response. This indicates that the activity of smooth muscles in general was depressed by sesbania. The effect was more evident in the lung than in the intestine. Therefore, an active principle in the extract which affects smooth muscle, rather than causing direct irritation, may exist. This assessment of smooth muscle activity is sensitive and was effective in detecting changes in tissues from sesbania-treated birds which had not shown any clinical signs. The results also support the possibility that smooth muscle involvement could be a primary cause of toxicity in sesbania poisoning.     

Unexpected newcastle disease virus in day old commercial chicks and breeder hen

Newcastle disease virus (NDV) specific antigen in the gut contents and NDV specific antibody in blood circulation were seen in day old chicks belonging to nine different commercial hatcheries of Tamil Nadu, India. Antigen disappeared by 4th week and antibody by 6th week of age. Fourteen NDV isolates obtained from the gut contents of day old chicks of different commercial hatcheries, one NDV isolate from dead in shell eggs and one NDV isolate from breeder hen were characterized and grouped under velogenic, mesogenic and lentogenic pathotypes. Four isolates were grouped under F and another four isolates were grouped under E based on reaction with monoclonal antibodies (Mabs) but found to be velogenic based on pathogenicity tests. In one particular flock velogenie NDV was isolated from breeder hen, dead in shell embryos and day old chicks and they all belong to Mabs group E. Vertical transmission of velogenic, mesogenic and lentogenic NDVs and role of NDVs in the gut contents have been discussed.     

Pharmacokinetics and relative bioavailability of tiamulin in broiler chicken as influenced by different routes of administration

The bioavailability and pharmacokinetic disposition of tiamulin in broiler chicken were investigated after administration through the crop, drinking water, and feed at 40 mg/kg body weight. Residues of tiamulin in tissues of broiler chicken were also assessed. Plasma and tissue concentrations of tiamulin were analyzed by reverse‐phase high‐performance liquid chromatography (HPLC) method. Plasma concentration–time data were described by the non‐compartmental model for all three routes, and pharmacokinetic parameters were calculated. There were no significant differences (p > 0.05) in pharmacokinetic parameters and mean plasma concentrations of tiamulin between three routes tested (crop, water, and feed), indicating equal efficacy. Tiamulin residues in edible tissues (muscles, skin, and fat) were lower than the advocated maximum residue limit (MRL of 0.1 µg/g and that of liver was 1 µg/g) on the 3rd day. No traces were found on the 5th day after drug administration. This indicated that the withdrawal period (less than 5 days) is very short, which makes it safer. This study shows that tiamulin can be used with equal efficacy through all routes of administration in broiler chicken (crop, water, and feed).     

In vitro response of large colon arterial and venous rings to vasodilating drugs in horses

OBJECTIVE: To determine in vitro vasomotor response of equine large colon arterial and venous rings with and without endothelium to vasodilator drugs, including dopamine (DOP), dopexamine (DPX), acepromazine (ACE), isoxsuprine (ISX), and nifedipine (NFP). ANIMALS: 7 adult horses. PROCEDURE: Relaxation of large colon arteries and veins in response to vasodilating drugs was determined by measuring the change in tension of vessel rings when exposed to a cumulative concentration range (10(-8) to 10(-4)M) of each drug. Vessel rings, with and without endothelium, were mounted in organ baths, attached to a transducer, and contracted with norepinephrine (NE). Cumulative concentration-response relationships, percentage maximal relaxation, and EC50 (concentration of drug required to relax the NE-induced contracted tissue to 50% of its contracted state) values were calculated. RESULTS: There were significant differences among drugs for EC50 (ACE = ISX < NFP) and percentage maximal relaxation (ACE = ISX > NFP = DPX > DOP) values in veins. Endothelium removal from veins had no significant effect. There were no differences in EC50 values for arteries; however, percentage maximal relaxation was significantly different among drugs (ACE = ISX = NFP > DPX = DOP). Endothelial removal resulted in higher EC50 and lower percentage maximal relaxation values, compared with endothelium-intact arteries. CONCLUSION AND CLINICAL RELEVANCE: ACE and ISX were the most potent and efficacious drugs evaluated and could potentially be used to improve blood flow after correction of large-colon volvulus. Dopamine cannot be recommended because of its biphasic response and potential to further decrease blood flow. Endothelium removal altered the vasodilatory responses of colonic arterial rings, but did not affect venous rings.