Arrhythmias in newborn thoroughbred foals.

Foetal electrocardiograms (ECG) were obtained from 39 of 50 Thoroughbred foaling mares close to delivery. The 50 newborn foals were studied electrocardiographically during their adaptive period, immediately after birth. In 48 foals there were paroxysmal arrhythmias or mixed arrhythmias. The most common arrhythmias were sinus arrhythmias including wandering pacemaker (32/50) and atrial premature contraction (30/50). The others observed were atrial fibrillation (15/50), ventricular premature contraction (10/50), partial atrioventricular block (7/50), ventricular tachycardia (4/50), atrial tachycardia (3/50) and idioventricular rhythm (1/50). The duration of the arrhythmias was approximately 5 min, and in all cases the arrhythmia disappeared within 15 min of birth. From foetal ECG recordings, no indication of the likelihood of neonatal arrhythmias was detected. With the exception of 2 cases, all foals have continued to grow and develop normally. These arrhythmias are considered normal physiological processes in newborn Thoroughbred foals during the adaptive period to extra-uterine life. High vagal tone and hypoxaemia at birth are probably the main contributing factors.     

Mycoplasma meleagridis of turkeys: probability of eliminating egg-borne infection

An equation was developed that describes the probability of eliminating egg-borne Mycoplasma meleagridis (MM) of turkeys by egg treatment. Probability (P) of MM elimination was described in terms of four parameters: pretreatment prevalence of MM, alpha; treatment failure rate, beta; number of eggs treated, n; and hatching rate, h. The eradication equation, based on the Poisson probability distribution, was P(0) = e-n alpha beta h. Probabilities derived from 12 hypothetical MM-eradication situations showed that increasing the size of any or all of the parameters decreased the likelihood of eradication. Use of the predictive equation as a planning tool in a successful MM-eradication program is demonstrated.     

Relationship between the development of the gubernaculum and the testicular descent in the rat fetus: macroscopic and light and electron microscopic observation

The gubernaculum consists of the gubernacular cord connected with the vas deferens and the gubernacular bulb connected with the retroabdominal wall. The cord was first distinguished on day 15 of gestation. Its length reached the peak on day 16, followed by a reduction until day 18 to be almost constant thereafter. The bulb was first distinguished on day 16, and its length was steadily increased toward term. The testis began to descend with a reduced length of the cord. By day 19, the testis descended close to the caudal part of the bulb by the sharp bending of the cord. Microscopically, the bulb consisted at first of a centrally located mesenchymal mass and of a covering layer of myoblasts. Thereafter, the mesenchymal mass was gradually shifted toward the cranial part of the bulb, trailing loose mesenchymal tissue in the caudal part of the bulb. On day 19, the mass was decreased in cell population but increased in amount of collagen fibers. It is suggested that the testicular descent starts on day 16 together with the commencement of shortening of the gubernacular cord and enlargement of the gubernacular bulb.     

Prevalence of Mycoplasma gallisepticum and M. synoviae in commercial layers in southern and central California

The prevalence of Mycoplasma gallisepticum (MG) and M. synoviae (MS) in commercial pullet and layer flocks in Southern and Central California was estimated by testing serum and egg-yolk samples from 360 sample flocks in Southern California and 41 sample flocks in Central California. Data relating to potential risk factors associated with MG and MS infections were collected. The estimated true prevalence rate of MG was 73% in Southern California and 3% in Central California. The estimated true prevalence rate of MS was 91% in Southern California and 32% in Central California. Compared with uninfected flocks, MG-infected flocks in Southern California were significantly older and were medicated less (P less than 0.05). More managements were under a multiple-age system, more flocks had molted, more were vaccinated with F-strain, and more had concurrent infection with MS (P less than 0.05). Only one sample flock in Central California was MG-infected; none were vaccinated with F-strain. In Southern California, MS-infected flocks were older than uninfected flocks, more had molted, more were medicated, and more had concurrent infection with MG (P less than 0.05). In Central California, MS-infected flocks did not differ significantly from uninfected flocks in any factor examined; the lack of statistical significance may be due to small sample size.     

The pathogenesis of infectious bursal disease: serologic, histopathologic, and clinical chemical observations

Infectious bursal disease in 35-day-old specific-pathogen-free (SPF) chickens was characterized clinically by its acute onset and brief duration. Clinical signs included depression, anorexia, diarrhea, and polyuria. A detectable precipitin antibody response occurred between 3 and 5 days postinoculation. Evaluation of pooled serum samples obtained from infectious bursal disease virus (IBDV)-infected chickens revealed transient changes in potassium, cholesterol, uric acid, lactate dehydrogenase, serum glutamic-oxalic transaminase, and serum proteins. Individual serum samples analyzed for uric acid concentration indicated that several IBDV-infected chickens had serum uric acid concentrations above the normal comparison range. Histopathologic examination of lymphoid and nonlymphoid tissues from IBDV-infected SPF chickens affirmed that the predominant lesion was lymphoid necrosis in the bursa of Fabricius. Other lymphoid organs were much less severely affected and possessed greater regenerative potential. Nonspecific and relatively mild changes were found in the liver and kidney: hepatic lipidosis and necrosis, renal intratubular crystalline deposits (probably urates), and increased ectopic lymphoid foci. There was no evidence of immune-complex-mediated arteritis/vasculitis in the sartorius muscle or any other tissue examined. Histopathologic and ultrastructural evidence of glomerulonephritis was rare but compatible with acute immune complexemia.     

Whole-cell protein profiles of Haemophilus paragallinarum as detected by polyacrylamide gel electrophoresis

The soluble whole-cell protein profiles of 15 isolates of Haemophilus paragallinarum were examined using standardized sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The patterns were reproducible and the isolates were similar overall. Despite this similarity, two protein profile types were recognized.     

Epidemiology, pathology, and immunohistochemistry of layer hens naturally affected with H5N1 highly pathogenic avian influenza in Japan

Epidemiology, pathology, and immunohistochemistry were investigated in layer hens affected with H5N1 highly pathogenic avian influenza, which occurred for the first time in 79 years in Japan. The farm, which had a total of 34,640 chickens, experienced up to 43.3% mortality before the chickens were depopulated. Clinically, the affected chickens exhibited mortality without apparent clinical signs. Histologically, hepatocytic necrosis; necrosis of ellipsoids and follicles with fibrin in the spleen; necrosis with glial nodules in the brain stem, cerebrum, and cerebellum; necrosis of acinar cells in the pancreas; and necrosis of lymphoid tissues in intestinal lamina propria were seen. Occasionally, mild bronchiolitis, degeneration of smooth muscle fibers in the cecum, and mild tubulonephrosis were noted. Immunohistochemically, influenza virus antigens were detected often in the liver and spleen, heart, intestine, gizzard, proventriculus, and oviduct. In addition, antigens were seen also in the brain, kidney, pancreas, and ovary, but seldom in the lung and trachea. Virus antigen was mainly detected in the capillary endothelium and parenchymal cells. This suggests that virus excretion from the respiratory tract was not as prevalent as that from the digestive tract in the present cases.