respiratory disorders are major concern for dairy cattle industry. viruses and bacteria in combinationwith stress play a key role in triggering acute respiratory infections. the most important viral agents arebovine viral diarrhoea virus (bvdv), bovine herpes virus type 1 (bhv-1), bovine respiratory syncytial virus(brsv), parainfluenza virus type 3 (piv-3) and bovine adenovirus (bav). this cros...

In Argentina, bovine leukaemia virus (BLV) infection is common in dairy herds. The country currently has a National Voluntary Control Programme but relatively few farms have enrolled. However, there is increased interest from authorities and farmers to implement regional compulsory programmes but there is scarce quantitative information of the transmission of BLV in cattle herds. This informati...

The possibility of immunizing human infants against rotaviruses, which cause severe dehydrating diarrheal disease, may depend on the use of a related rotavirus, derived from another animal species, as a source of antigen. To test the feasibility of this approach, calves were infected in utero with a bovine rotavirus and challenged with bovine or human type 2 rotavirus shortly after birth. Infec...

Three types of agent cause cancer radiation, chemicals and viruses. The first demonstration of induction of cancer by a biological agent was made ^ 1911 by Rous who transmitted a tumour of fowls from one bird to another by means ?? cell-free extracts; later work has shown that such extracts contain the organism novV known as the Rous sarcoma virus. More recently, a number of other avian tumour8...

Human T-cell lymphotropic virus type 1 (HTLV-1) can cause adult T-cell leukaemia/lymphoma (ATLL). Two patients originating from the Caribbean area with ATLL are described. The first patient developed respiratory insufficiency due to acute T-cell leukaemia. The diagnosis was suspected because of characteristics of abnormal lymphocytes in the blood smear. The second patient had lymphadenopathy an...

Bovine leukaemia virus (BLV) resides in infected lymphocytes in a latent, repressed state but becomes expressed a few hours after the cells are cultured in vitro. We have identified several conditions and factors affecting the expression of BLV in short-term cultures of naturally infected lymphoid cells. The presence of foetal calf serum in the culture medium greatly stimulates virus expression...

In addition to the known induction of xenotropic endogenous virus in B-mitogen-stimulated murine lymphocyte cultures, distinguishable defective viruses were also induced in different mouse strains (NFS/N, 129, BALB/c). AKR cells produced xenotropic virus and also, in contrast to BALB/c, ecotropic virus. The drug bromodeoxyuridine appeared to have differential effects on virus expression, amplif...