ABSTRACT
Epinotia aporema granulovirus (EpapGV) has attracted interest as a potential biocontrol agent of the soybean pest Epinotia aporema in Argentina. Studies on virus/host interactions conducted so far have lacked an accurate method to assess the progress of virus load during the infection process. The present paper reports the development of a real-time PCR for EpapGV and its application to describe viral kinetics following ingestion of two different virus doses by last-instar E. aporema larvae. Real-time PCR was shown to be a reliable method to detect and quantify the presence of EpapGV in the analyzed samples. The increase in virus titer (log) exhibited a sigmoidal pattern, with an exponential growth phase between 24 and 48 h postinfection for both initial doses tested.
Subject(s)
Baculoviridae/isolation & purification , Lepidoptera/virology , Real-Time Polymerase Chain Reaction/methods , Animals , Baculoviridae/chemistry , Baculoviridae/classification , Baculoviridae/genetics , Kinetics , Viral Proteins/chemistry , Viral Proteins/geneticsABSTRACT
Argentina suffered an extensive foot-and-mouth disease (FMD) epidemic between July 2000 and January 2002, 3 months after obtaining the official FMD-free without vaccination status conferred by the World Organization for Animal Health. This is one of the largest FMD epidemics controlled by implementation of a systematic mass vaccination campaign in an FMD-free country. In 2000, 124 herds were reported as FMD positive, 2394 herds in 2001 and one in January 2002; the total number of cattle herds in the country at that time was approximately 230 000. Estimates of FMD transmission are important to understand the dynamics of disease spread and for estimating the value for the parameterization of disease transmission models, with the ultimate goals of predicting its spread, assessing and designing control strategies, conducting economic analyses and supporting the decision-making process. In this study, the within-herd coefficient of transmission, ß, was computed for herds affected in the 2001 FMD epidemic and categorized as low or high based on the median value of ß. A logistic regression model was fitted to identify factors significantly associated with high values of ß. Results suggested that the odds of having a high within-herd transmission were significantly associated with time from initial herd infection to disease detection, date of report, vaccination, and time from initial herd infection to herd vaccination. Results presented in this study demonstrate, in quantifiable terms, the protective impact of vaccination in reducing FMD transmission in infected herds. These results will be useful for the parameterization of epidemiological models aimed at quantifying the impact of vaccination and for the design and implementation of FMD emergency vaccination strategies in face of an epidemic.
Subject(s)
Cattle Diseases/transmission , Disease Outbreaks/veterinary , Foot-and-Mouth Disease Virus/classification , Foot-and-Mouth Disease/prevention & control , Viral Vaccines/immunology , Animals , Argentina/epidemiology , Cattle , Cattle Diseases/epidemiology , Disease Outbreaks/prevention & control , Foot-and-Mouth Disease/epidemiology , Foot-and-Mouth Disease/transmission , Logistic Models , Multivariate Analysis , Serotyping , Time FactorsABSTRACT
During 2000-2002 a foot-and-mouth disease (FMD) epizootic affected Argentina and spread across the country resulting in more than 2500 outbreaks. In order to study the evolution of the FMD viruses (FMDV) and help with disease control measures, a genetic characterization and phylogenetic analysis was performed of 43 field isolates representative of the epizootic. The nucleotide sequence of the VP1-coding region was determined for the viruses and used in this study. Two serotype A lineages, A/Arg/00 and A/Arg/01 (1000/1000 bootstrap value) and two different serotype O/Arg/00 lineages (848/1000 bootstrap value) were identified. Phylogenetic analysis showed that viruses A/Arg/01 and O/Arg/00 could be related with former South American isolates, while the origin of A Argentina 2000 viruses remains unclear. Comparison of the amino acid sequences with vaccine reference strains revealed differences at critical antigenic sites for emergent strains A/Arg/00 and A/Arg/01, leading to a change in the current vaccine formulation.
Subject(s)
Capsid Proteins/genetics , Foot-and-Mouth Disease Virus/genetics , Foot-and-Mouth Disease/epidemiology , Amino Acid Sequence , Animals , Argentina/epidemiology , Base Sequence , Capsid Proteins/chemistry , Cattle , Cattle Diseases/epidemiology , Cattle Diseases/virology , Disease Outbreaks/veterinary , Foot-and-Mouth Disease/virology , Foot-and-Mouth Disease Virus/classification , Molecular Epidemiology , Molecular Sequence Data , Phylogeny , RNA, Viral/chemistry , RNA, Viral/genetics , Reverse Transcriptase Polymerase Chain Reaction/veterinary , Sequence Alignment/veterinary , Sequence Homology, Nucleic Acid , Serotyping/veterinaryABSTRACT
The complete nucleotide sequence of foot-and-mouth disease virus (FMDV) South American strain O(1) Campos/Bra/58 was determined. The 8,168 Kb sequence and the deduced amino acid sequence were compared to published FMDV sequences. They showed the highest sequence homology with the O(1) Kaufbeuren/FRG/66 strain, but closer evolutionary relatedness to the Argentinean strains.