Antibiotic resistance and transferable antibiotica resistance Escherichia coli isolated from calves on a modern farm with therapeutic problems and unsatisfactory management conditions.

On a farm with therapeutic problems and unsatisfactory management conditions, the occurrence of antibiotic resistance and transferable antibiotic resistance has been studied in E. coli isolated from calves which were 5 and 30 days old. Strains with resistance to up to seven antibiotics as well as transferable resistance against up to five antibiotics were recorded. On an average, 4.2 strains with different patterns and 4.0 different strains with transferable resistance were isolated from each calf. The corresponding figures previously found for healthy control calves were 1.6 and 1.1 strains, respectively. Resistance and transferable resistance were most common against sulphonamide and penicillin.     

Studies on pentagastrin-induced hypocalcaemia in lactating cows.

During recent years it has been evident that a number of gastrointestinal hormones are potent calcitonin secretagogues, and it has been suggested that a gastrointestinal-thyroid C cell system exists as a part of post prandial calcium homeostasis. In the present study the hypocalcaemic effect of pentagastrin, a synthetic peptide with gastrin effects, was studied in lactating cows. Intravenous infusion of pentagastrin caused marked hypocalcaemia and hypophosphataemia in the cows. Thyroidectomy completely abolished the hypocalcaemic and hypophosphataemic effects of the peptide. The results thus suggested that the effects of the peptide were due to release of endogenous calcitonin.     

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.     

Natural bovine lentivirus type 1 infection in Holstein dairy cattle. II. Lymphoid tissue lesions

Bovine immunodeficiency virus (BIV) in Holstein cows was associated with morphologic evidence of lymphoid organ deficiency. Cows were subjected to normal management practices including parturition and lactation without adverse environmental stresses. During the clinical disease process there was marked weight loss and wasting with frequent and severe concurrent infections. Lymphoid follicular hyperplasia and dysplasia in lymph nodes, and hypertrophy and hyperplasia in hemal lymph nodes were characteristics of the lymphoid tissues. Atrophy of lymphoid cell compartments with depletion of lymphocytes and a lymphocytic lymphoid folliculitis were components of the lymphoid system pathology. The nodal tissue lesions resembled those observed in feline, simian, and human lentiviral disease. A functional correlation with immune system deficiency was the development of multiple bacterial infections which failed to resolve after appropriate therapy. The BIV-associated disease syndrome in dairy cows may be useful as a model system for investigation of the pathogenesis of the lymphoid organ changes that occur in humans and animals with lentiviral infection.     

Polymerase chain reaction detection of Mycobacterium tuberculosis complex and Mycobacterium avium organisms in formalin-fixed tissues from culture-negative ruminants

In the US eradication program for bovine tuberculosis, a definitive diagnosis depends on the isolation of Mycobacterium bovis. However, in some cases bacterial culture is unsuccessful, even though the tissue is considered suspicious by histopathology because granulomatous lesions and acid-fast organisms are present. The purpose of this study was to determine if polymerase chain reaction (PCR) tests on formalin-fixed tissue would successfully identify the organisms observed in suspect lesions from culture-negative animals. Diagnostic laboratory records were used to select paraffin blocks of tissue from 102 ruminants that had suspect microscopic lesions but no bacterial isolation. Sections from these blocks were examined with PCR primers for IS6110 to detect Mycobacterium tuberculosis complex infection, or with 16S ribosomal RNA and IS900 primers for detection of Mycobacterium avium. The PCR tests successfully identified a mycobacterial infection in 58 of 102 tissues, including 41 M. tuberculosis complex and 17 M. avium (11 subspecies paratuberculosis). These results demonstrate that PCR testing of formalin-fixed tissue, in combination with bacterial culture, may increase the effectiveness of laboratory diagnostic efforts to detect and identify the most common mycobacterial diseases of ruminants.     

Natural transplacental infection of dairy calves with bovine immunodeficiency virus and estimation of effect on neonatal health

Many experimental infection studies with bovine immunodeficiency virus (BIV) have been conducted, but neither virus transmission under natural conditions nor longitudinal clinical effects of naturally occurring infections in non-experimental populations are well explored. We tested the hypotheses that BIV is transmitted across the placenta during gestation and that intragestionally infected calves are at increased risk of neonatal disease. A cohort of 59 dairy cows on one farm were enrolled at parturition and the BIV serostatus of the cows and their pre-colostral calves determined with an indirect fluorescent-antibody assay. Moreover, the enrolled calves were monitored thrice weekly for specific clinical signs through the duration of the 30 day neonatal period and the occurrence of clinical signs analyzed for association with calf pre-colostral BIV serostatus and dam BIV serostatus. Confounding due to calf passive immunity and season of birth were also explored. Forty percent of seropositive cows (14/35) gave birth to seropositive calves but no seropositive calves (0/19) were born to seronegative dams (estimated relative risk 16, 95% exact confidence interval 2.6–5.8×10²⁹). Calf pre-colostral BIV serostatus was not associated with the occurrence or frequency of clinical signs — but dam BIV serostatus was associated with the odds of occurrence of calf hyperthermia and with the frequency of occurrence of calf hyperthermia and hyperventilatory events. This study is inconclusive about the effects of prenatal BIV infection on neonatal health — but it does provide evidence for the natural occurrence of transplacental BIV infection.