A new passive immune strategy based on IgY antibodies as a key element to control neonatal calf diarrhea in dairy farms.

Background: Neonatal diarrhea remains one of the main causes of morbi-mortality in dairy calves under artificial rearing. It is often caused by infectious agents of viral, bacterial, or parasitic origin. Cows vaccination and colostrum intake by calves during the first 6 h of life are critical strategies to prevent severe diarrhea but these are still insufficient.

Characterization of a type O foot-and-mouth disease virus re-emerging in the year 2011 in free areas of the Southern Cone of South America and cross-protection studies with the vaccine strain in use in the region.

Molecular, antigenic and vaccine matching studies, including protective response in vivo, were conducted with a foot-and-mouth disease type O virus isolated during the outbreak in September 2011 in San Pedro, Paraguay, country internationally recognized as free with vaccination in 1997. The phylogenetic tree derived from complete VP(1) sequences as well as monoclonal antibody profiling indicated that this isolate was related to viruses responsible for previous emergencies in free areas of the Southern Cone of South America occurring sporadically between the years 2000 and 2006. Marked differences with the vaccine strain O(1)/Campos, including the loss of reactivity with neutralizing MAbs, were recognized.

Characterization of foot-and-mouth disease virus from outbreaks in Ecuador during 2009-2010 and cross-protection studies with the vaccine strain in use in the region.

During the years 2009 and 2010 relevant epidemic waves of foot-and-mouth disease (FMD) serotype O occurred in Ecuador, representing a great drawback for the last stages of the ongoing eradication program in South America. This study describes the molecular and antigenic characterizations of 29 isolates collected from various regions in the country and their relationship to the vaccine strain. The phylogenetic tree derived from sequences spanning the complete VP(1) protein showed that, despite the widespread origin of the viruses, they were all related among themselves and to previous isolates occurring in 2008, with around 10% difference with the vaccine strain O1/Campos.

Updating of the correlation between lpELISA titers and protection from virus challenge for the assessment of the potency of polyvalent aphtovirus vaccines in Argentina.

Routine vaccination campaigns are carried out in Argentina twice a year, involving more than 100 million doses of foot-and-mouth disease (FMD) vaccine. Although the challenge test in cattle has not been totally replaced for the assessment of FMD vaccine potency, Argentine Animal Health authorities have used an indirect alternative method based on specific correlation studies of protection against podal generalization (PPG) tests performed in cattle with a validated liquid phase blocking ELISA (lpELISA). The change of vaccine formulations that took place after the 2000-2001 outbreaks, generated a gap in the correlation between lpELISA titers and PPG for the new FMD virus strains.

Foot-and-mouth disease vaccine potency testing in cattle using homologous and heterologous challenge strains: precision of the "Protection against Podal Generalisation" test.

The level of protection conferred by foot-and-mouth disease (FMD) vaccines in primovaccinated animals primarily depends on the potency of the vaccine and the relatedness of the vaccine strain and circulating field isolate. The "Gold Standard" FMD vaccine potency test is the in vivo test performed in the target species. The objective of the study was to determine the precision of the in vivo "Protection against Podal Generalisation" (PPG) FMD vaccine potency test in cattle using homologous (vaccine quality control) and heterologous (vaccine matching) viral challenge.