Development of an enzyme-linked immunosorbent assay (ELISA) for the detection of antibody to the parasitic dinoflagellate Amyloodinium ocellatum in Oreochromis aureus.

An enzyme-linked immunosorbent assay (ELISA) using antibody to affinity-purified Oreochromis aureus immunoglobulin and antigens from the parasitic dinoflagellate amyloodinium ocellatum was developed. The ELISA was then used to evaluate the immune response of the tilapine fish to immunization with the parasite. Fish immunized with antigens of the dinospore stage, either live or sonicated, produced a specific immune response that was detectable by this ELISA. Combinations of serial dilutions of A. ocellatum antigen and fish anti-A. ocellatum serum were examined to determine which dilutions provided optimal differentiation of seropositive from seronegative fish. Fresh and heat-inactivated serum from both seropositive and seronegative fish produced similar results.     

Experimental cryptosporidiosis and infectious bursal disease virus infection of specific-pathogen-free chickens

Specific-pathogen-free chickens orally inoculated at 4 days of age with a moderately pathogenic vaccine strain of infectious bursal disease virus (IBDV) and/or at 5 days of age with Cryptosporidium baileyi oocysts remained free of overt clinical signs throughout a 16-day period postinoculation (PI). The prepatency period for C. baileyi oocyst shedding was shorter in chickens receiving higher numbers of oocysts, but once shedding was detected, there were no obvious differences in shedding patterns among groups receiving 10(3) through 10(6) oocysts. On days 8 and 16 PI, cryptosporidia were located primarily in the bursae of Fabricius. IBDV exposure was associated with bursal follicle atrophy, whereas C. baileyi infection resulted in bursal epithelial hypertrophy and hyperplasia, mild follicle atrophy, and heterophil infiltration of the bursal mucosa. Examination of experimental groups of 30 birds each indicated that concurrent infection with both agents resulted in more severe bursal lesions, more infected birds, and greater numbers of cryptosporidia in infected tissues. At the termination of the trial, 16 days PI, Cryptosporidium infection was associated with a 6% decrease in mean body weight compared with controls.     

Complete Heart Block in a Dog Seropositive for Borrelia burgdorferi: Similarity to Human Lyme Carditis

Lyme disease has been recognized in humans since 1975 when it was associated with an outbreak of oligoarthritis in children in Lyme, Connecticut. Erythema chronicum migrans (ECM) is a clinical marker for the human disease, which usually appears within 3 to 32 days after an infected tick bite. Lyme disease is caused by spirochete, Borrelia burgdorferi, which is vectored by the hard ticks Ixodes dammini or Ixodes pacificus in the United States. In humans, Lyme disease has been found to cause a variety of clinical syndromes including cardiopathy, neuropathy, dermatopathy, and arthropathy. Human Lyme carditis is characterized by varying degrees of atrioventricular (AV) heart block that usually resolve regardless of therapy. Lyme disease has been reported in the dog as an arthropathy. This article reports a case of complete heart block and myocarditis in a dog with a positive titer for B burgdorferi, in which clinical and pathologic findings were similar to those seen in human Lyme myocarditis.     

Gastroenterostomy for treatment of gastroduodenal ulcer disease in 14 foals

Gastroenterostomy was performed in 14 foals to treat gastric outflow obstruction caused by advanced gastroduodenal ulcer disease. The onset of excessive salivation and teeth grinding, without response to medical treatment, combined with endoscopic and radiographic evidence of gastric outflow obstruction, were indications for surgical intervention. Successful outcome in 5 foals was attributed to early diagnosis, patient stabilization, early surgical correction, and postoperative management including antibiotics and antiulcer medication.     

Acclimation of citrus to water stress

Alemow (Citrus macrophylla Wester) seedlings were subjected to moderate or severe water stress by watering them at different intervals for several irrigation cycles. Transpiration rate was measured after irrigation was resumed. Severe water stress reduced transpiration but increased leaf water potential (ψ_leaf), while moderate water stress reduced transpiration less and did not affect ψ_leaf. This suggests that moderate water stress influences only stomatal conductance and not root and shoot resistance.     

Elevated virulence of Newcastle disease virus strains following serial passages in kidney cells in vitro

Serial passage of two lentogenic Newcastle disease virus (NDV) strains in kidney cell lines increased virulence and changed viral biological properties. In two cell lines (BHK and MDBK), elevation in virulence was demonstrated by plaque formation under an overlay with no additives, decrease in mean death times, elevated intracerebral pathogenicity index, and cytopathic effect in chicken embryo fibroblasts. Some other markers not directly correlated to virulence, such as heat inactivation of hemagglutinin and neuraminidase, were not influenced by passage in kidney cells. In addition, all strains were slow eluters. This observation emphasizes the importance of preventing the virus from reaching the viscera.     

Yield loss of sweet corn cultivars in response to defoliation and to infection byexserohilum turcicum

The effect of northern leaf blight (NLB) or leaf defoliation on the yield of nine sweet corn cultivars was studied in field experiments. Plants were defoliated or infected in the bottom, middle or top third of the leaf canopy. The effect of defoliation or infection on yield was significantly higher for plants treated 55 days after planting than for those treated 70 days after planting. Cultivar response differed significantly for both treatments, the most sensitive cultivar being ‘Jubilee’ and the least sensitive being Ssupersweet 7900. In all cases, the highest yield loss was recorded when the middle third of the leaf canopy was treated. The relative importance of the top third of the leaf canopy increased if the treatment was done 3 weeks before harvesting. This study emphasized the importance of leaf position, cultivar, and plant growth stage for evaluating losses caused by NLB, and may explain the failure of various models to describe yield loss due to NLB.     

Testing a process-based model of tree seedling growth by manipulating

A model was developed that simulated photosynthesis, growth and allocation in tree seedlings. The model was parameterized with data from experiments on seedlings of sycamore (Acer pseudoplatanus L.), Sitka spruce (Picea sitchensis (Bong) Carr.) and young birch trees (Betula pendula Roth.). In these experiments, CO2 concentration ([CO2]) and nutrient addition rate were varied. Parameters quantifying nutrient uptake, translocation and starch synthesis were fitted, based on data from control treatments. Elevated [CO2] and low-nutrient treatments were then used to test the predicted response of growth and allocation against observations. The model accurately predicted total seedling growth in the elevated [CO2] treatments. A response of growth to elevated [CO2] was seen in the birch and sycamore experiments, but not in the Sitka spruce, because of photosynthetic down-regulation. Predictions of allocation were reasonably accurate in the birch and Sitka spruce experiments, but were notably poorer in the sycamore experiments, possibly because of differences in sink strength between root and shoot. In the birch and sycamore experiments, little change in allocation with elevated [CO2] was observed or predicted. This was ascribed to the relative values of K(Tc) and K(Tn), the translocation coefficients that determine the sensitivity of allocation to carbon and nitrogen uptake rates, respectively. Growth and allocation in the low-nutrient treatments were poorly predicted by the model. In Sitka spruce, it was suspected that the photosynthetic parameters measured in August 1994 had been higher earlier in the season, before nutrients became depleted. In sycamore, the discrepancies were thought to relate to differences in sink strength between root and shoot that could not be described by the model.     

Chromobacterium violaceum infection in two dogs

Chromobacterium violaceum is a saprophyte of soil and water in tropical and subtropical environments that is associated with rare but highly fatal infections in animals and humans. Systemic infection was diagnosed in two critically ill dogs from Florida. Fever was absent in both dogs. Both dogs were treated surgically and provided with intensive care, but only one survived. The identification of characteristic, violet-pigmented bacterial colonies on routine microbial cultures should alert microbiologists and clinicians to the likelihood of this dangerous pathogen. Because of the rapidly progressive nature of this infection, empirical antibiotic administration with fluoroquinolones should be employed pending susceptibility testing.