Experimental and natural infection with the enzootic leukosis virus of cattle

A trial was performed with heifers at the age of six to seven months. The animals were experimentally infected with the lymphocytes of a virus-productive donor. Infection was produced in all the nine cases, as demonstrated by means of the positive syncytial test. As indicated by the results of the trial, the antibodies to the enzootic bovine leucosis virus (BLV) were produced soon after experimental infection. A high sensitivity of the serum-neutralization test and the ELISA method was demonstrated in this connection: by these methods, the antibodies were identified already two to three weeks after experimental infection whereas by the immunodiffusion test they could be detected only after five weeks. Twenty-four animals were exposed to natural contact infection. Within 270 days of the trial, the disease after contact was recorded only in one heifer out of the four that were in close contact with the experimentally infected animals. In this case, as compared with experimental infection, the antibodies were produced much later--after 85 to 93 days. Leucosis was recorded in none of the remaining animals. The reasons why such a favourable result was obtained were the thorough disinfection of the stables after blood collections and the strict observance of the aseptic conditions. The results of experimental infection in three cows were identical with those obtained in young cattle. In the experimentally infected dairy cows, antibodies in milk were determined by the ELISA method. As found, in milk the antibodies to BLV appear two to three weeks later than they do in serum. The ELISA method of BLV antibody detection can be used for the identification of infected animals in herds where enzootic bovine leucosis occurs.     

Untersuchungen zur Übertragung von Clavibacter michiganensis ssp. sepedonicus auf gesunde Kartoffelknollen

Zusammenfassung In den Jahren 1999 bis 2003 wurde in Freiland-, Klimakammer- und Lagerungsversuchen überprüft, ob ein Risiko für die Übertragung des Erregers der Bakteriellen Ringfäule der Kartoffel (Clavibacter michiganensis ssp. sepedonicus) besteht, wenn (a) gesunde Kartoffelknollen in Kontakt mit Maschinen und Geräten kommen, die mit dem Erreger kontaminiert sind (indirekter Kontakt) und (b) gesunde Kartoffelknollen direkt in Kontakt mit infizierten Knollen kommen (direkter Kontakt). Nach indirektem Kontakt konnte nur beim nachfolgenden Anbau der kontaminierten Knollen in der Klimakammer Befall in Kraut und Knollen festgestellt werden. Im Freiland konnte der Erreger, auch bei wiederholtem Nachbau der geernteten Knollen, nicht nachgewiesen werden. Nach direktem Kontakt und nachfolgendem Anbau der kontaminierten Knollen in der Klimakammer und im Freiland, wurde der Erreger in allen Fällen in den geerntete Knollen nachgewiesen. Befall im Kraut wurde nur in dem Klimakammerversuch und in einem Freilandversuch ermittelt. Wurden durch direkten Kontakt kontaminierte Knollen eingelagert, konnte der Erreger in allen untersuchten Knollen festgestellt werden. Insgesamt besteht ein hohes Risiko, dass gesunde Knollen infiziert werden, wenn oberflächliche Kontaminationen mit dem Erreger erfolgen. Die Wahrscheinlichkeit von Infektionen steigt mit zunehmender Kontaminationsstärke.     

Überleben von Ralstonia solanacearum Biovar 2 (Rasse 3), dem Erreger der Schleimkrankheit der Kartoffel, in Boden und auf verschiedenen Materialien (Mikrokosmos)

Microcosm studies were carried out to test the survival of Ralstonia solanacearum biovar 2 (race 3) in soil at the permanent wilting point (wp) water content and at field capacity (fc) water content and on various material. Soils were placed at permanent ?5°C, 4°C, 15°C and 20°C and weekly fluctuating ?10/0/+10°C and the material at 5, 15 °C, 20°C with relative humidity (rh) uncontrolled or at constant 10% or 90%. In soil, survival was clearly dependent on temperature independent of water content. At 20°C Ralstonia solanacearum could be reisolated up to 364 days, at 15°C up to 290 days, at 4°C up to 209 days and at fluctuating temperatures (?10/0/+10°C) only up to 18 days. The lower the temperature, the more the population declined. At 15°C and 20°C appr. 10⁷ cfu/g soil were detected after 100 days, whereas at ?5°C only 10² cfu/g soil were detected after only 18 days. The pathogen was longer detectable in sandy-clay loam than in lighter sandy soil. It could be longer reisolated at wilting point and the populations did not decline as rapidly as at field capacity. Ralstonia solanacearum could best survive on material surfaces like rubber, plastic and varnished metal with maximum survival of 40 days at 5°C and 10% rh. In general there is a low risk of Ralstonia solanacearum overwintering under European climatic conditions when the fields are cleared of plant debris and the soil is frozen. Contamined material surfaces pose the risk of pathogen transmission to healthy tubers.     

Efficacy of a mephentermine‐based product as a vasopressor and a cardiac performance enhancer when given intramuscularly to cattle

The goal of this study was to confirm the vasopressor and cardiac effects of POTENAY^® INJETÁVEL (POT), a mephentermine‐based product, given to cattle with induced vascular/cardiac depression. Ten healthy Holstein cattle (206 ± 13 kg) followed a randomized‐complete‐block design (RCBD) utilizing crossover study design. Each animal randomly received (1 ml/25 kg, IM) of either POT (n = 10) or volume‐matched placebo control (0.9%NaCl, CP, n = 10). A subset of animals (n = 5) received POT first (day 0) while the remaining (n = 5) received CP; after a six‐day washout period, cattle received the opposite compound. Animals were anesthetized and catheterized for systemic/left ventricular hemodynamic monitoring. Myocardial dysfunction/hypotension was induced by increasing the end‐tidal isoflurane concentration until arterial blood pressure was 20% lower than at baseline and remained stable. Once the animal was determined to be hypotensive and hemodynamically stable, steady‐state hypotensive baseline data (BL2) were acquired, and treatment with either POT or CP was given. Data were acquired post‐treatment at every 15 min for 90 min. POT improved cardiac output (+68 L/min, ±14%, p < 0.05), MAP (+14 mmHg, ±4%, p < 0.05), HR (+22 bpm, ±8%, p < 0.05), and peak rates of ventricular pressure change during both systole (dP/dt_max: +37 mmHg/s ±13%, p < 0.05) and diastole (dP/dt_min: +31 mmHg/s, ±7%, p < 0.05). No improvements were noted following placebo‐control administration. Results indicate that POT improves cardiac performance and systemic hemodynamics in cattle with induced cardiovascular depression when given as single intramuscular injection.     

Evaluation of the effectiveness of selected measures against bovine spongiform encephalopathy (BSE) in Switzerland by use of the basic reproduction ratio R0

The effectiveness of two measures against Bovine Spongiform Encephalopathy (BSE), the compulsory processing of animal by products to meat and bone meal (MBM) at 133 degrees C under 3 bars of pressure for 20 minutes in February 1993 and the exclusion of fallen stock, heads with eyes and spinal cord of cattle older than 30 month from MBM production in April 1996, was evaluated in a process model. The transmission of BSE by calculation of the basic reproduction ratio R0 was modelled.The results were verified by use of a cohort model, based on observed surveillance data. Prior to 1990, before the ban of feeding MBM to ruminants, R0, as calculated in the process model, was above 1, coherent with a slowly progressing BSE epidemic. Since 1991, values of R0 were low at 0.06.The corresponding R0 values derived from the cohort model were higher, the lowest value 0.13 calculated for 1996. Given such low R0 values, the epidemic should have died out. Additionally, no influence of the two measures was obvious at that time given the low level of R0. The discrepancy between the results of the two models is evidence for a dependency of the BSE epidemic from an infection source not considered in the process model. This infection source is most likely importation of feed ingredients and MBM.     

Expression of porcine endogenous retroviruses (PERVs) in melanomas of Munich miniature swine (MMS) Troll

Porcine endogenous retroviruses (PERVs) are integrated in the genome of all pig breeds. Since some of them are able to infect human cells, they might represent a risk for xenotransplantation using pig cells or organs. However, the expression and biological role of PERVs in healthy pigs as well as in porcine tumours is largely unknown. Since we and others have recently shown overexpression of a human endogenous retrovirus, HERV-K, in human melanomas, we studied the expression of PERVs in melanomas of selectively bred Munich miniature swine (MMS) Troll. This breeding herd of MMS Troll is characterised by a high prevalence of melanomas, which histologically resemble various types of cutaneous melanomas in humans. Several genetic factors have been defined when studying inheritance of melanomas and melanocytic nevi in MMS Troll. Here we show that the polytropic PERV-A and PERV-B as well as the ecotropic PERV-C are present in the genome of all melanoma bearing MMS Troll investigated. Most interestingly, in the spleen, but not in other organs, recombinant PERV-A/C proviruses were found. PERV expression was found elevated in melanomas when compared to normal skin and viral proteins were expressed in melanomas and pulmonary metastasis-derived melanoma cell cultures. During passaging of these cells in vitro the expression of PERV mRNA and protein increased and virus particles were released as shown by RT activity in the supernatant and by electron microscopy. Genomic RNA of PERV-A, -B and -C were found in pelleted virus particles. Although PERV expression was elevated in melanomas and pulmonary metastasis-derived cell cultures, the function of the virus in tumour development is still unclear.