Molecular epidemiology of Salmonella Heidelberg in an equine hospital

From 1992 to 1997, multi-drug resistant (MDR) Salmonella Heidelberg isolates were cultured from a number of horses hospitalised in a veterinary hospital in Victoria, Australia. To examine the relationships between the cases, 28 isolates from the hospital were compared by pulsed field gel electrophoresis (PFGE), IS200 element profiles, antimicrobial resistance patterns, plasmid profiles and phage typing. The PFGE patterns following digestion with XbaI and BlnI restriction endonucleases showed that the isolates from the veterinary hospital originated from a common source. These isolates also had indistinguishable IS200 profiles. However, PFGE was more discriminatory than IS200 profiles. All the veterinary hospital isolates and one independent isolate had the same antimicrobial resistance pattern and had at least one plasmid in common. Localisation of antimicrobial resistance genes indicated that the veterinary hospital isolates had more than one plasmid carrying resistance genes and that the genes encoding sulphathiazole and trimethoprim resistance were not on these plasmids. Phage typing was ineffective as 22 of the 28 isolates were untypeable. In conclusion, the combination of different methods used for epidemiological studies suggested that a single strain of MDR S. Heidelberg was isolated from horses admitted to the hospital for 6 years and caused salmonellosis in susceptible horses within that period with no apparent correlation between the antimicrobials used and retention of its MDR phenotype.     

柞蚕品种龄期经过与饲料效率的相关性研究

选用１６个饲料效率表现、化性、体色及龄期经过各异的品种,春秋分别单头室内育,采用干量折地,各２０次重复取平均值,统计春养、秋养和春秋养平均全龄经过,５龄经过日数与饲料效率对比分析、绘图展示等,发现：龄期经过都与品种的饲料效率有关,但无论全龄还是５龄经过最长、最短的,饲料效率表现都不好,而处于龄期经过第二高峰,即全龄比平均值长０．８４ｄ左右,５龄长０．７３ｄ左右,饲料效率表现最佳,这为高饲料效率品种     

Normal and aberrant tissue distribution of Loma salmonae (Microspora) within rainbow trout, Oncorhynchus mykiss (Walbaum), following experimental infection at water temperatures within and outside of the xenoma-expression temperature boundaries

Temperatures above 20 °C or below 9 °C interrupt the life cycle of the gill intracellular microsporidian parasite Loma salmonae (Microspora) prior to sporogony, inhibiting the production of xenomas. This study intended to characterize this life-cycle failure. Juvenile rainbow trout, Oncorhynchus mykiss (Walbaum), were experimentally infected with L. salmonae spores, and the effect of water temperature on the progress of infection, as determined by polymerase chain reaction, was compared for fish held at water temperatures of 5, 15 and 21 °C. At 15 °C, parasite DNA was first detected in the heart (3 days post-exposure [PE]), and then in the gills and spleen (2 weeks PE). Branchial xenomas developed by week 4 PE. In contrast, at 5 °C, the arrival of the parasite in the heart was delayed until 7 days PE. However, even though parasite DNA was detected in the gills at 7 days PE, xenomas failed to form in the gill, and by week 4 PE, parasite DNA was no longer detected. In fish held at 21 °C, parasite DNA was detected in the heart, gills and spleen by 3 days post-infection, and similar results were observed at 7 days PE. Xenomas also failed to form in these fish and parasite DNA was no longer detected by week 2 PE. Within the range of temperatures tested in this study, spore germination and delivery of their DNA into the host through the intestinal wall was not blocked by temperature. At 5 or 21 °C, migration to the heart and gills occurred, but at aberrant periods of time. The normal life cycle of L. salmonae may depend on the completion of relatively lengthy, but yet unknown, stages of development within the heart, prior to reaching the gill. This development may be adversely affected by temperature, and explain the temperature limits of this parasite.     

Effects of selenium source on measures of selenium status and immune function in horses

The effects of selenium (Se) supplementation and source on equine immune function have not been extensively studied. This study examined the effects of oral Se supplementation and Se source on aspects of innate and adaptive immunity in horses. Fifteen horses were assigned to 1 of 3 groups (5 horses/group): control, inorganic Se (sodium selenite), organic Se (Se yeast). Immune function tests performed included: lymphocyte proliferation in response to mitogen concanavalin A, neutrophil phagocytosis, antibody production after rabies vaccination, relative cytokine gene expression in stimulated lymphocytes [interferon gamma (IFNγ), interleukin (IL)-2, IL-5, IL-10, tumor necrosis factor alpha (TNFα)], and neutrophils (IL-1, IL-6, IL-8, IL-12, TNFα). Plasma, red blood cell Se, and blood glutathione peroxidase activity were measured. Plasma and red blood cell Se were highest in horses in the organic Se group, compared with that of inorganic Se or control groups. Organic Se supplementation increased the relative lymphocyte expression of IL-5, compared with inorganic Se or no Se. Selenium supplementation increased relative neutrophil expression of IL-1 and IL-8. Other measures of immune function were unaffected. Dietary Se content and source appear to influence immune function in horses, including alterations in lymphocyte expression of IL-5, and neutrophil expression of IL-1 and IL-8.     

Nonisotopic detection of Loma salmonae (microspora) in rainbow trout (Oncorhynchus mykiss) gills by in situ hybridization

Loma salmonae, a microsporidian parasite of salmonids of the genus Oncorhynchus, is a significant cause of economic loss in pen-reared chinook salmon (O. tschawytscha). Final stages of L. salmonae infections are easily recognized by the xenomas that form in the gills during sporogony. However, early prexenoma stages of infection (3 weeks or less after infection) are difficult to detect on histologic slides. An L. salmonae-specific single-stranded DNA probe labeled with digoxigenin was used to detect these prexenoma stages of L salmonae by in situ hybridization in experimentally infected rainbow trout. This method allows detection of the parasite in the gills only 2 weeks after infection, providing a sensitive and specific way of detecting L. salmonae during the early stages of infection.     

Induction of enzootic pneumonia in pigs by the administration of an aerosol of in vitro-cultured Mycoplasma hyopneumoniae

The aim of this study was to establish whether enzootic pneumonia could be induced reliably in piglets by administering an aerosolised culture of Mycoplasma hyopneumoniae. Groups of five M hyopneumoniaefree Landrace x Large White piglets weaned at 11 to 14 days of age were exposed to aerosols of in vitro cultures of a virulent strain of M hyopneumoniae. In three separate trials, 14 of 15 pigs exposed to the bacteria developed pneumonia, but pigs exposed to the culture medium alone did not develop the disease. Lung pathology, both gross and histological, indicated acute disease. Ten of the pigs were tested for seroconversion by Western blot and they were all positive. The growth rates of the infected pigs were significantly reduced and the water consumption of the infected groups was also depressed. M hyopneumoniae was recovered from eight of the 15 infected pigs.     

The effect of age on serum antibody titers after rabies and influenza vaccination in healthy horses

BACKGROUND: The proportion of geriatric horses within the equine population has increased in the past decade, but there is limited information on the immune function of these animals. HYPOTHESIS: Aged horses will have a lesser increase in serum antibody response to vaccination. ANIMALS: Thirty-four aged healthy horses (> or = 20 years) and 29 younger adult horses (4-12 years) of various breeds. METHODS: All horses were vaccinated with vaccines of killed rabies and influenza virus. Horses in each age group were allocated to receive either rabies or influenza booster vaccine 4 weeks after the initial vaccination. Serum samples were taken at 0, 4, 8, and 24 weeks. Rabies serum neutralization titers and equine influenza virus specific antibody sub-isotypes (IgGa, IgGb, IgG(T), and IgA) as well as single radial hemolysis (SRH) titers were determined. RESULTS: Rabies antibody titers were similar in the 2 age groups at all sampling times. Aged horses had higher IgGa and IgGb influenza antibody titers before vaccination than younger horses but similar titers after vaccination (P= .004 and P= .0027, respectively). Younger horses had significantly greater increases in titer than aged horses at all sampling times for IgGa (P= .001) and at 8 and 24 weeks for IgGb (P= .041 and .01, respectively). There was no detectable serum IgG(T) at any time point. A significant booster vaccine effect was seen for both antirabies and anti-influenza titers. Anti-influenza titer before vaccination also had a significant effect on subsequent antibody response. CONCLUSIONS AND CLINICAL IMPORTANCE: Healthy aged horses generated a primary immune response to a killed rabies vaccine similar to that of younger adult horses. Aged horses had a significantly reduced anamnestic response to influenza vaccine.