Isolation of an attenuated myxoma virus field strain that can confer protection against myxomatosis on contacts of vaccinates

Twenty MV strains obtained from a survey of field strains currently circulating throughout Spain were analyzed for their virulence and horizontal spreading among rabbits by contact transmission. A virus strain with suitable characteristics to be used as a potential vaccine against myxomatosis in wild rabbit populations was selected. Following inoculation, the selected MV strain elicited high levels of MV specific antibodies and induced protection of rabbits against a virulent MV challenge. Furthermore, the attenuated MV was transmitted to 9 out of 16 uninoculated rabbits by contact, inducing protection against myxomatosis

Safety evaluation of a recombinant myxoma-RHDV virus inducing horizontal transmissible protection against myxomatosis and rabbit haemorrhagic disease

We have recently developed a transmissible vaccine to immunize rabbits against myxomatosis and rabbit haemorrhagic disease based on a recombinant myxoma virus (MV) expressing the rabbit haemorrhagic disease virus (RHDV) capsid protein [Barcena et al. Horizontal transmissible protection against myxomatosis and rabbit haemorragic disease using a recombinant myxoma virus. J. Virol. 2000;741114-23]. Administration of the recombinant virus protects rabbits against lethal RHDV and MV challenges. Furthermore, the recombinant virus is capable of horizontal spreading promoting protection of contact animals, thus providing the opportunity to immunize wild rabbit populations. However, potential risks must be extensively evaluated before considering its field use. In this study several safety issues concerning the proposed vaccine have been evaluated under laboratory conditions. Results indicated that vaccine administration is safe even at a 100-fold overdose. No undesirable effects were detected upon administration to immunosuppressed or pregnant rabbits. The recombinant virus maintained its attenuated phenotype after 10 passages in vivo. (C) 2000 Elsevier Science Ltd

Horizontal transmissible protection against myxomatosis and rabbit hemorrhagic disease by using a recombinant myxoma virus

We have developed a new strategy for immunization of wild rabbit populations against myxomatosis and rabbit hemorrhagic disease (RHD) that uses recombinant viruses based on a naturally attenuated field strain of myxoma virus (MV). The recombinant viruses expressed the RHDV major capsid protein (VP60) including a linear epitope tag from the transmissible gastroenteritis virus (TGEV) nucleoprotein. Following inoculation, the recombinant viruses induced specific antibody responses against MV, RHDV, and the TGEV tag. Immunization of wild rabbits by the subcutaneous and oral routes conferred protection against virulent RHDV and MV challenges. The recombinant viruses showed a limited horizontal transmission capacity, either by direct contact or in a flea-mediated process, promoting immunization of contact uninoculated animals

First field trial of a transmissible recombinant vaccine against myxomatosis and rabbit hemorrhagic disease

As a novel approach for immunisation of wild rabbits, we have recently developed a transmissible vaccine against myxomatosis and rabbit hemorrhagic disease (RHD) based on a recombinant myxoma virus (MV) expressing the RHDV capsid protein [J. Virol. 74 (2000) 1114]. The efficacy and safety of the vaccine have been extensively evaluated under laboratory conditions. In this study, we report the first limited field trial of the candidate vaccine that was undertaken in an island of 34 Has containing a population of around 300 rabbits. Following administration by the subcutaneous route to 76 rabbits, the vaccine induced specific antibody responses against both myxomatosis and RHDV in all the inoculated rabbits. Furthermore, the recombinant virus exhibited a limited horizontal transmission capacity, promoting seroconversion of around 50% of the uninoculated rabbit population. No evidence of undesirable effects due to the recombinant virus field release was detected. © 2001 Elsevier Science Ltd. All rights reserved

Cryptosporidium

Cryptosporidium sp. infects the gastrointestinal tract of a wide range of vertebrates, including domestic and livestock animals as well as humans. Cryptosporidiosis of neonatal farm ruminants causes considerable economic losses as the disease is commonly associated with intense diarrhea leading to an impaired growth, a decreased performance and production, and often animal death. The highly infective oocyst stage is excreted with the feces and disseminated into the environment, contaminating water and food. Neonatal calves are a major reservoir of the zoonotic C. parvum, which causes, in addition to the anthroponotic C. hominis, human cryptosporidiosis and is of considerable public health concern. Currently, no vaccine or efficient drug is available against the disease. From a veterinarian economical point of view, C. parvum is the most important species among the 30 recognized species infecting bovines, lamb, goats, pigs, horses, and dogs worldwide. After the discovery of C. parvum by Tyzzer in the year 1912, the taxon Cryptosporidium has been classified into coccidia. However, recent findings on the Cryptosporidium life cycle and molecular phylogenetic evidence resulted in the reclassification of Cryptosporidium into the gregarines. This novel placement appreciates previously underestimated and/or neglected features of Cryptosporidium that are common to gregarines such as a low host specificity and/or the possibility to survive without a host.Fil: Tomazic, Mariela Luján. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Patobiología; ArgentinaFil: Garro, Carlos. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Patobiología; ArgentinaFil: Schnittger, Leonhard. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Patobiología; Argentina. Universidad de Morón; Argentin