Molecular Epizootology Flashcards
Epizootology/Epidemiology investigates:
- Cause of the emergence of infectious diseases
- Methods of transmission of infectious diseases
- Legality of spread of infectious diseases
In Epizootological investigation what is evaluated: (10)
- Age structure of diseased and healthy animals
- Concentration of animals
- Course of the disease
- Time sequence of the spread of the disease
- Mortality, morbidity
- Import and export of animals
- Transfer of animals between farms
- Vaccination
- Level of breeding management and all environmental factors
- Share of wild animals in the possible transmission of the disease
The solution to the epizootological problem requires:
- Detailed analysis of the epizootological situation in the outbreak
- Results of laboratory diagnostics (Identification of the etiological agent, the causative agent of the disease)
- Confirmation of infection in the outbreak
What is the aim of Molecular Epizootology:
- To observe the variability of microorganisms at the molecular level
- To look for phylogenetic (developmental) relationships between strains of microorganisms with different origin (diff. outbreaks) in connection with the assessment of the overall epizootological situation
What does molecular epizootology need to analyze:
- Small part of the genome of a microorganism (about 500 nucleotides) or several parts of the genome and tracking mutations in those parts
In principle: Genomes of microrganisms (DNA/RNA) are:
Not stable during replication but undergo mutations
Synthesis of DNA molecules during replication:
Mutations are rarer because the enzyme DNA polymerase synthesizing DNA has a self-repair mechanism, controls the incorporation of the correct nucleotide = Proof-reading activity
Synthesis of RNA molecules during replication:
Mutation are more frequent, because the enzyme RNA polymerase does not have a self-repair mechanism
Mutation in the genome of a microorganism occur more frequently :
If it gets into a:
- New environment
- New host
What are the steps in general methodical process used in molecular epizootology:
- Assessment of the overall epizootological situation
- Selection of suitable microorganism strains for analysis
- Molecular-genetic analysis of the genomes of selected strains (by method of nucleic acid sequencing, the latest method of DNA sequencing-next gen.)
For the evaluation of infectious situation what is used:
Phylogenetic analyzes
What are Phylogenetic trees:
- In graphic form, they express the developmental relationships (phylogenetic, evolutionary) between studied strains
- They are constructed from the nucleotide sequences of pathogen genomes
- Computer programs are used for their construction (DNASTAR, MEGA)
What are the TWO approches used in construction of Phylogenetic trees:
- Measurement of distance data (Distance matrix method)
- Analysis of the impact of each nucleotide and mutation (discrete character method)
What is the procedure for studying the genetic variability of pathogens?
- Preparation of PCR products (the result of amplification)
- Chromatograms (the result of sequencing)
- Sequences processed by computer software (DNASTAR)
- Comparison of sequences (alignment)
- Similarity and identity of nucleotide sequences (%)
- Phylogenetic tree
- Added to International database - GEN BANK
What is the use of methods of molecular epizootology: (6)
(Long answer)
- For evaluation of the overall epizootological situation in connection with the occurrence of dangerous diseases, esp. Zoonoses
- For determining the direction of spread and the origin of outbreaks
- For control of the introduction of disease during the import/export of animals
- For genetic typing of the microorganism, determination of genotype, subtypes
- For distinguishing between vaccine strain and currently circulating field strains
- For the study of evolution of microorganisms
