DNA probes for the detection of toxin genes in Escherichia coli isolated from diarrhoeal disease in cattle and pigs

DNA gene probes specific for genes coding for heat labile toxin (LT), heat stable toxins (STpa, STpb) and Vero-cell toxins (VT1, VT2) were used to examine 1031 diarrhoeal disease isolates of E. coli (345 from cattle and 686 from pigs). Of the bovine strains, 60 hybridized with the STpa probe and most possessed the K99 (F5) or F41 adhesin. Five bovine strains possessed STpb genes and five either VT1 or VT2 genes. Of the porcine strains, 245 hybridized with one or more gene probes. Of 160 K88 (F4) positive strains, 133 possessed both LT and STpb genes, whilst 17 possessed LT or STpb or STpa alone or in combination. Ten K88 strains did not possess toxin genes. Isolates bearing the K99 (F5) adhesion possessed either STpa, STpb and VT2 genes alone or in combination; in one isolate only the LT gene was detected. Isolates belonging to serogroup 0138:K81 were more heterogeneous as to their toxin genes; of the 60 strains, fourteen carried only VT2 genes, thirty-two carried VT2, STpa and STpb genes, one carried LT, VT2, STpa and STpb genes, two carried STpb gene, four carried STpa and STpb genes, one carried LT and VT2 genes, two carried LT and STpa genes, whilst four carried none. Twenty-four percent of all toxigenic strains apparently did not possess adhesins.     

Comparison of a DNA probe, complement-fixation and indirect immunofluorescence tests for diagnosing Anaplasma marginale in suspected carrier cattle

Most estimates of the prevalence of anaplasmosis have been based on serologic data using the complement-fixation (CF) and/or card agglutination tests. Since these tests are considered to be only about 50 percent reliable for detecting carrier cattle in enzootically stable herds, the need for more sensitive diagnostic tests is widely recognized. The objective in the present study was to compare the sensitivity of the CF test with that of the indirect immunofluorescence (IIF) test and a recently developed DNA probe in determining the prevalence of Anaplasma marginale infection in cattle from an enzootic area. The study herd consisted of 52 8-month-old steers and 13 3-year-old cows of mixed beef breed. All cattle were initially tested for this comparative purpose. All but one animal (one that was a positive reactor as assessed by all three tests, and served as a positive control), were treated with long-acting oxytetracycline in an attempt to clear any carrier infections. Each animal was then retested at 1 month and 2 months post-treatment (PT), in an effort to determine if the DNA probe could be used to evaluate the effectiveness of the drug. Six of the 65 (9.2%) initial serum samples were CF positive. In contrast, 60 (92.3%) and 64 (98.5%) of the samples were positive as assessed with the IIF test and the DNA probe, respectively. The DNA hybridization reactions varied in intensity within the sample population indicating different individual levels of infection. The DNA probe hybridized with two samples taken at 1 month PT, and with two different samples taken at 2 months PT. The mean IIF titers were reduced at both the 1 month and 2 month sampling times. These results suggest that the drug did not eliminate infections in all cattle. Some may have been cleared, but, in any event, the drug did reduce the level of infections below the sensitivity of the DNA probe and interrupted continuity of stimulation of antibody. Therefore, the DNA probe and the IIF test appear to be considerably more sensitive in detecting carrier infections than the CF test, and should be considered in future epidemiologic studies.     

Attempted reactivation of latent bovine herpesvirus 1 infection in calves by infection with ruminant pestiviruses

Three calves, latently infected with bovine herpesvirus 1 (BHV 1), were each inoculated intranasally with 9 strains of ruminant pestivirus (BVDV). All three calves developed a biphasic pyrexia and a lymphopenia followed by a neutrophilia. They did not shed BHV 1 in their nasal secretions in the 14 days following BVDV inoculation, and their BHV 1 antibody levels remained static, as did those of 2 control calves not given BVDV. All five calves were subsequently shown to be latently infected with BHV 1 by the production of recrudescent infections following the administration of dexamethasone. BHV 1 was recovered from nasal secretions and there was a marked rise in BHV 1 antibody titres in the second week after dexamethasone administration.     

AcuteTrypanosoma vivax infection of ethiopian cattle in the apparent absence of tsetse

Summary Investigations of acute trypanosomiasis in a group of 1,200 cattle provided strong evidence for mechanical transmission by haematophagous flies other than tsetse. Although recently introduced cattle may have had previous contact with tsetse flies the incident occurred in an area remote from their known range. Mortality exceeded 6% before the outbreak was controlled by chemotherapy. Mechanically transmittedTrypanosoma vivax infection may be of widespread occurrence in eastern Ethiopia.

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Infeccion Aguda PorTrypanosoma Vivax En Ganado Etiope En La Ausencia Aparente De Tsetse

Resumen La investigación sobre tripanosomiasis aguda, en un grupo de 1.200 animales, proporcionó evidencia de transmisión por moscas hematófagas diferentes a la tsetse. El incidente ocurrió en un área remota del habitat de la tsetse, aunque un grupo de ganado recientemente introducido, pudo tener algun contacto previo con éstas últimas. La mortalidad excedió el seis por ciento, antes que el brote se controlara. La transmisión puramente mecánica de la tripanosomiasis en Etiopía, podría tener más importancia que la que actualmente se le da.

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Infection Aigue ATrypanosoma Vivax Chez Les Bovins Ethiopiens Malgre L'Absence Apparente De Tse-Tse

Résumé Les recherches des signes de la Trypanosomiase aiguë conduites dans un groupe de 1200 bovins ont apporté la preuve certaine de la transmission mécanique de la maladie par d'autres insectes hématophages que la tsé-tsé. Bien que du bétail récemment importé ait pu déjà être en contact avec ce vecteur, la maladie est apparue dans une région éloignée de sa zone habituelle. La mortalité a dépassé 6 p. 100 avant que le foyer n'ait pu être contrôlé par la chimiothérapie. La transmission mécanique de l'infection àT. vivax est probablement largement répandue dans l'Est éthiopien.

     

Chronic cervical compressive myelopathy in horses: clinical correlations with spinal cord alterations

Histological examination was performed on the cervical spinal cord from 13 horses with chronic cervical compressive myelopathy of 4 to 29 months duration. Structural alterations were correlated with clinical features. At the level of compression, the spinal cord was grossly deformed. Histological alterations included nerve fibre swelling and degeneration, occasional spheroids, astrocytic gliosis, increased macrophage activity and increased perivascular collagen. Myelin degeneration or loss at the level of the compressive lesion was greatest in the ventral and lateral funiculi and less consistently present in the dorsal funiculi. Asymmetry of lesions in the dorsal funiculi was associated with asymmetry of clinical signs in 5 horses. Histological alterations in areas of Wallerian degeneration were similar to that at the level of spinal cord compression, except that perivascular collagen was not increased. Wallerian degeneration was present cranial to the compressed site in the superficial portions of the lateral funiculi and in the middle of the dorsal funiculi. Caudal to the compressed site it was present in the ventral funiculi adjacent to the ventral median fissure and in the middle of the lateral funiculi. Deformation of the spinal cord did not correlate with the severity or duration of clinical signs but was positively correlated with the amount of perivascular collagen increase. The amount of nerve fibre swelling was not correlated with the severity of clinical signs but was negatively correlated with their duration. A rapid loss of nerve fibres apparently occurred early in the course of compression, since there was a marked decrease in the amount of nerve fibre swelling and Marchi stained degenerating myelin with increasing clinical duration.(ABSTRACT TRUNCATED AT 250 WORDS)     

The origins of gene instability in yeast

Two unstable mutations at the his4 locus of yeast are due to the insertion of the transposable elements Ty912 and Ty917 into the his4 regulatory region. The two transposons are related, one being derived from the other by a substitution of 4000 base pairs of DNA. Element Ty912 includes identical terminal repeats, whereas the terminal repeats of Ty917 are not identical. Transposition of Ty912 or Ty917 generates 5-base-pair duplications of the target DNA at either end of the element. Expression and reversion of a his4 gene containing Ty912 or Ty917 is controlled by three unlinked regulatory genes. The properties of these regulatory genes are similar to those described for the controlling elements in maize.     

Provenance Performance of Liriodendron tulipifera in South Africa

Four provenances of Liriodendron tulipifera were imported from the United States in 1973. Test plantings were made in three forest regions of South Africa, with major trials being established in one of the regions. The resulting provenance rankings show a classical clinal variation pattern with the southernmost United States source exhibiting the best growth rate. All sources tested appear to be equally sensitive to rat and buck damage.     

An outbreak of avian malaria in captive yellowheads/mohua (Mohoua ochrocephala)

CASE HISTORY: Eight mohua, or yellowheads (Mohoua ochrocephala), were held in a large open aviary over the summer months of 2003–2004, following their capture for captivebreeding purposes. Two birds died of transportation trauma shortly after arrival, one became ill and died a month later, and another four died within a 2-week period in February 2004. The eighth bird also became ill at this time but survived for a year following treatment with chloroquine and doxycycline.

CLINICAL AND PATHOLOGICAL FINDINGS: The affected birds were depressed, lethargic and dyspnoeic. Necropsy of three birds showed a slightly pale and swollen liver and spleen. Impression smears of the liver of one bird revealed schizonts resembling Plasmodium spp. within the cytoplasm of many hepatocytes, which was confirmed histopathologically. Similar protozoal organisms were seen within splenic histiocytes and pulmonary endothelial cells of 5/6 birds. Electron microscopy identified these as protozoal schizonts containing merozoites of similar size and structure to those of Plasmodium spp.

DIAGNOSIS: The birds were infected with a protozoal haemoparasite resembling Plasmodium spp.; asexual stages within hepatocytes and endothelial cells of the lung and spleen were typical of this organism.

CONCLUSIONS AND CLINICAL RELEVANCE: The mohua captured from west Otago were highly susceptible to avian malaria as they came from an isolated population that was likely to be naïve and have had no previous contact with this organism. The birds were probably infected by bites from mosquitoes feeding off local populations of blackbirds subsequently found to be infected with Plasmodium spp.     

Failure of zinc supplementation to prevent severe facial eczema in cattle fed excess copper

CASE HISTORY: A 400-cow dairy unit in the Waikato suffered a severe outbreak of facial eczema (FE) despite consistent zinc supplementation and significantly elevated serum zinc concentrations.

CLINICAL FINDINGS: FE prevention had begun in mid-January 2006, via zinc sulphate supplementation in the water. Photosensitisation was reported on 06 April, contemporaneous with a marked increase in the number of Pithomyces chartarum spores in pasture samples. Within 10 days of this first clinical case, 100 affected cows had been dried off, eight of which subsequently died or were culled. Blood samples were collected from ten affected cows; all had serum zinc concentrations >17 µmol/L, and eight had gamma-glutamyl transferase (GGT) activities >200 U/ml, indicating that the photosensitisation was secondary to liver damage, i.e. probably FE. Further investigation identified that this herd had been receiving excess copper supplementation; 4/6 culled cows had liver copper concentrations within or above the marginal range for copper toxicity.

DIAGNOSIS: Severe FE despite zinc supplementation that increased serum zinc concentrations above recommended levels

CLINICAL RELEVANCE: As zinc supplementation significantly reduces apparent copper status, copper supplementation is often used to counteract this. Previous excess copper intake may reduce the efficacy of zinc in preventing FE, thus copper intake should be assessed prior to the start of zinc supplementation.