General EPI - notes for credit

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What is the principle of the Virus Neutralization Test (VNT)?

It is a highly specific test that estimates the capacity of antibodies (ABs) to neutralize the biological activity of an antigen (Ag) in vitro, thereby preventing viruses from infecting cells.

How do antibodies (ABs) block viral infection in a VNT?

Specific antibodies combine with and block critical sites on the virus, which prevents the virus from infecting susceptible cells and causing a cytopathic effect (CPE).

What are the main steps in performing a VNT?

1. A serum sample is diluted in steps and incubated with the same quantity of virus.

2. Susceptible cells are added to the samples to make the neutralization effect visible.

3. The plate undergoes a second incubation, allowing un-neutralized virus to damage cells.

What indicates a positive result in a VNT?

A positive serum contains specific antibodies that neutralize the virus. As a result, the susceptible cells remain intact, meaning a cytopathic effect (CPE) is not recognized or an immune staining remains negative.

What indicates a negative result in a VNT?

A negative serum lacks specific antibodies, so the virus

How are cell cultures divided according to their way of cultivation?

a. Primary and established b. Monolayers and established c. Monolayers and suspension

monolayers and suspension cultures.

What is the principle of Immunofluorescence Assay (IFA)?

IFA uses marked antibodies (ABs) from immune serum against an antigen (Ag) to visualize it. The Ag, bound to a marked AB, is visualized under a fluorescence microscope by a fluorochrome attached to the marked AB.

Which fluorochromes are commonly used for marking antibodies in IFA?

Common fluorochromes include fluorescein isocyanate and fluorescein isothiocyanate (FITC). These dyes bind well and allow antibodies to react with the antigen.

What is conjugation in the context of IFA?

Conjugation is the chemical reaction between the immunoglobulins (Igs) of the serum and the fluorochrome, resulting in a marked antibody, also known as a conjugate.

What is the difference between primary and secondary IFA?

PRIMARY IFA uses only one antibody, while SECONDARY IFA uses two antibodies.

What are the main reagents of PCR?

• Template DNA

• Nucleotides (dNTPs)

• Primers

• Buffer

• DNA polymerase (Taq polymerase)

What is PCR?

PCR (Polymerase Chain Reaction) is an in-vitro genetic amplification technique that uses repeated cycles of oligonucleotide synthesis to create large amounts of specific foreign DNA.

What are the three main steps of a PCR cycle?

Each PCR cycle consists of three steps:

1. Denaturation (94-95^{\circ}C, 1-2 min)

2. Annealing (45-60^{\circ}C, 1-2 min)

3. Extension (72^{\circ}C, 1-2 min)

What is the theoretical amplification principle of PCR?

Each time a PCR cycle is completed, there is a theoretical doubling of the target sequence.

How are PCR products detected?

Detection of PCR products can be done by:

• Electrophoresis of PCR products on an agarose gel

• Hybridization reaction

• Cleavage of product using specific restriction enzymes

What if the starting material for PCR is RNA?

If the starting material is RNA, it should first be transcribed into cDNA (complementary DNA) using reverse transcriptase before proceeding with standard PCR.

What does OIE stand for?

a) Organisation of internation disease elimination

b) world health organisation

c) world organisation for animal health

World Organisation for Animal Health

What are the stages of the infectious process?

The stages of the infectious process are:

1. Incubation period

2. Prodromal period

3. Manifestation period

4. Final period (recovery or death)

Define the 'Incubation period' in the infectious process.

time interval between exposure to an aetiological agent and the appearance of the first clinical signs.

Define the 'Prodromal period' in the infectious process.

characterized by unspecific signs of infection

Define the 'Manifestation period' in the infectious process.

when specific clinical signs of the infection become evident

What is the 'Final period' in the infectious process?

final period represents the outcome of the infection, which can be either recovery or death. For example, retroviruses like FIV can significantly affect the course and outcome of this period.

What does the infectious process require?

The infectious process requires:

• The presence of a pathogenic microbe.

• A way of shedding from the source of the aetiological agent to next susceptible macroorganisms.

• presence of susceptible macroorganism

What is the infectious process?

dynamic process that refers to the interaction between the etiological triad. A pathogenic agent can only be transmitted by shedding into the environment.

What is a 'source of infection'?

a. Macroorganismus, in which etiological agent survives, multiplies and is excreted

b. Macrooganismus, in which etiological agent survives and multiplies

c. Macroorganismus, in which etiological agent survives and is excreted

a. macroorganism in which the etiological agent survives, multiplies, and is excreted.

What capabilities must an etiological agent possess to cause an infectious process?

An etiological agent must be able to:

• Penetrate into a susceptible macroorganism (MaO).

• Cause an infectious process.

• Be excreted into the environment.

• Be transmitted to next susceptible individuals.

Name four common serological methods.

1. ELISA

2. VNT (Virus Neutralization Test)

3. IFA (Immunofluorescence Assay)

4. HIT (Hemagglutination Inhibition Test)

Describe an 'abortive infection'.

An abortive infection is a virus infection in which no new infectious viral particles are produced. It is characterized by hardly noticed clinical signs which disappear relatively soon.

Define 'polyvalent vaccine'.

A polyvalent vaccine is a vaccine prepared from cultures of two or more strains of the same species of microorganism or virus, e.g., pneumococcal vaccines.

How are etiological agents divided according to their pathogenicity?

Etiological agents are divided into:

1. Pathogenic (obligatory): Always cause infectious disease after penetration into a susceptible MaO (e.g., anthrax, Ebola).

2. Facultative pathogenic: Survive as commensals and only cause disease under certain conditions (e.g., Staphylococcus, Streptococcus, or Malassezia in immunosuppressed animals like those with Cushing's disease).

3. Apathogenic: Not able to cause infectious disease.

What are the different forms of infectious processes?

Infectious processes can be:

• Apparent (typical or atypical): Clinically manifested infection with detectable signs.

• Inapparent (latent, subclinical, asymptomatic): Presence of infection without recognizable clinical signs, identifiable only by laboratory means.

  • Latent infection: A type of persistent infection where a pathogenic virus lies dormant within a cell.

• Persistent: Chronic or latent; when the infection is chronic, it is eventually cleared, while latent or slow infections last the life of the host.

What factors depend on the pathogenicity of etiological agents?

The pathogenicity of agents depends on their ability to:

• Infectivity (capability to enter, survive, and multiply in host)

• Adaptability

• Selectivity

• Reproducibility

• Heritability

• Immunogenicity (ability to provoke an immune response; relevant for vaccination)

• Transmissibility (contagious, non-contagious)

• Entry routes (e.g., respiratory tract, skin, urogenital tract, conjunctiva, umbilical infection, accidental entry).

How are etiological agents divided according to their tropisms? (Give examples)

Etiological agents are divided into:

1. Monotropic: Tropisms for one organ or system (e.g., influenza for the respiratory system, Malassezia for the skin).

2. Polytropic: Tropisms for more organs and systems (e.g., distemper affecting the nervous system, skin, digestive tract, immune system; leptospirosis affecting the kidney, liver).

3. Pantropic: Affecting multiple sites in the organism without specific targeting (e.g., anthrax).

Define epizootic process and its stages.

The epizootic process is a dynamic, multifactorial phenomenon involving continuous interaction between animal populations, etiological agents, and the environment.

Its stages are:

1. Inter-epizootic (latent): High population immunity, minimal etiological agents.

2. Pre-epizootic (awakening): Reduced population immunity, increased susceptible animals, highest pathogenicity.

3. Ascending: Rapid increase in affected animals, prevalent acute/subacute disease forms.

4. Culmination: Specific antibodies develop, population immunity rises.

5. Descending: Decrease in susceptible/diseased animals, chronic/sub-chronic/latent disease forms observed.

What is the epizootic triad?

The epizootic triad consists of:

• Animal populations (herd, flock)

• Etiological agents and factors of mass diseases

• Environmental factors (e.g., temperature, humidity)

What does 'Post-epizootic' mean?

a. Mild degree of epizootic disease/intensity

b. The highest degree of epizootic disease/intensity

c. The lowest degree of epizootic disease/intensity

c. The lowest degree of epizootic disease/intensity

How is a natural focus of infection limited?

a. By age and season b. By season c. Geographically and seasonally

c. Geographically and seasonally

Note: A natural focus is a geographical territory precisely bordered and characterized by a given geobiocenosis and ecosystems with circulating pathogens. Its principal components are the etiological triad (population, etiological agent, and environment).

What are the basic components of a natural focus of infection?

a. Etiological agent, donor, vector, recipient, environment

b. Etiological agent, donor, vector, recipient

c. Etiological agent, donor, vector, environment

a. Etiological agent, donor, vector, recipient, environment

Tricomponental foci of infections are divided into:

a. Synantropic, interhostal, recipiental

b. Vector, interhostal, postinterhostal

c. Interhostal, synantropic, vector

b. Vector, interhostal, postinterhostal

How is pathogen transmission divided according to its multiplication in the vector?

a. Propagative, inoculative, cyclopropagative

b. Propagative, cyclometamorphic, cyclopropagative

c. Inoculative, cyclometamorphic, cyclopropagative

b. Propagative, cyclometamorphic, cyclopropagative

• Propagative: The agent only multiplies in the vector's body.

• Cyclometamorphic: The agent survives in the vector's body but does not multiply.

• Cyclopropagative: The agent survives and multiplies in the vector's body.

In which disease is therapy prohibited (among the given options)?

a. Foot and mouth disease b. Parvovirosis c. Eysipelas

a. Foot and mouth disease

Therapy is also prohibited in other OIE-listed diseases such as anthrax, rabies, rinderpest, African swine fever, and classical swine fever.

Young of ruminants are born:

a. Agammaglobulinaemic b. Hypogammaglobulinaemic

a. Agammaglobulinaemic

Calves are born without antibodies (agammaglobulinaemic) due to the separation of the maternal and fetal blood supplies in the placenta of the cow.

What is the role of colostrum?

Colostrum provides passive immunity, protecting against early septicemia, organ infections, and local intestinal bacterial multiplication. Serum Ig concentration directly correlates with the amount of ingested Ig, which depends on the quantity and Ig concentration of the colostrum.

What does WHO stand for?

WHO stands for the World Health Organisation.

What are the consequences of intrauterine infections?

The consequences of intrauterine infections include:

• Abortion/mummification

• Birth of a clinically healthy animal

• Immunotolerance (clinically healthy but persistently infected)

What is the eradication of infectious disease?

The eradication of infectious disease refers to the elimination of all diseased animals, primarily via two methods:

1. Slaughtering policy of affected and suspected animals (test & slaughter)

2. Complete depopulation (without testing) of all animals in the territory

Name the methods used in epizootology.

The methods used in epizootology are:

1. Diagnostic methods: To reveal etiological agents, sources, and environmental factors in space and time.

2. Descriptive methods: Collection, compilation, and processing results of diagnostic activities.

3. Analytical methods: Evaluation of the true epizootiological situation and decision-making for epizoo strategy, programs, and measures.

4. Statistical methods: Calculations and principles of probability, epizootiological indicators.

5. Experimental methods: Confirmation of epizoo hypotheses and development of new methods.

6. Theoretical methods: Generalization of findings and practical experience.

What are the objectives of epizootology?

The objectives of epizootology are:

• To create disease-free animal populations.

• To protect infectious disease-free populations against the introduction of these diseases.

• To protect non-infectious disease-free populations against etiological agents.

• To protect human populations against diseases transmissible from animals.

• To improve and recover animal population health.

• To reduce, eliminate, and finally eradicate mass diseases of animals.

What is a zoonosis?

A zoonosis is a disease that can be transmitted from vertebrate animals to humans.

How are zoonoses classified?

Zoonoses are classified as:

1. Direct zoonoses: Transmitted directly from a host vertebrate animal to a human.

2. Cyclozoonoses: Require more than one vertebrate animal host for the survival and transmission of the agent (e.g., Echinococcus requiring canids and ruminants).

3. Metazoonoses: Involve both a vertebrate and an invertebrate host; humans are typically infected when bitten by the invertebrate vector.

4. Saprazoonoses: The infection requires a non-living site (such as soil or water) to persist or multiply; these can be parasitic or mycotic.

5. Anthropozoonosis: An animal disease transmissible to humans.

6. Zooanthroponosis: A human disease transmissible to animals.

Cyclozoonoses require:

a. One vertebrate host

b. More than one vertebrate host

c. Vertebrate and invertebrate host

b. More than one vertebrate host

Anthropozoonosis describes a disease that:

a. Primarily occurs in humans and can be transmitted to animals
b. Primarily occurs in animals and can be transmitted to humans
c. Primarily occurs in animals and can be transmitted to animals by a human vector

b. Primarily occurs in animals and can be transmitted to humans

What is the CAMP method used to identify?

The CAMP method is used to identify Streptococcus agalactiae.

What is Sabouraud agar used for?

Sabouraud agar is used for culturing fungi.

What are the forms of infectious processes according to their duration?

The forms of infectious processes according to their duration are:

• Peracute: Minutes to hours

• Acute: Days to 3 weeks

• Sub-acute: 3 to 7 weeks

• Chronic: More than 7 weeks

Clinical signs of not getting Lgs in newborns are?

Newborns will be weak and unable to mount an immune response, likely leading to death within a day or two after birth due to infection.

Define immunomodulation.

Immunomodulation is a change in the body's immune system caused by agents that either activate or suppress its function.

What is an immunomodulator?

An immunomodulator is a substance that affects the immune system, having either a suppressive or stimulating effect.

Give examples of immunosuppressants and their roles.

Immunosuppressants play a major role in organ transplantations and autoimmune diseases. They include T-cell inhibitors; anti-proliferative drugs (e.g., cyclophosphamide), glucocorticoids (e.g., prednisolone), and antibodies (e.g., against CD3, thymocytes).

What are immunostimulators and their purpose?

Immunostimulators stimulate the immune system by inducing activation or increasing the activity of its components. Their purpose is to restore immunocompetence and control/treat infectious diseases.

How are immunostimulators classified by mechanism?

Immunostimulators can be:

1. Specific: Possess antigen specificity (e.g., vaccines, antigens).

2. Non-specific: Stimulate immune system components without antigen specificity.

3. Passive: Involve the substitution of endogenous substances (e.g., Ig, cytokines, hormones).

4. Active: Exogenous biological or synthetic substances.

What are the indications for using immunostimulators?

Indications include secondary immunodeficiency, increasing vaccine efficiency, chronic or recurrent infections, inefficient therapy (e.g., with antibiotics), and supportive therapy (e.g., for infections, tumors).

How are immunostimulators classified by origin, and provide examples?

Immunostimulators can be classified by origin:

1. Biological substances: Bacteria, bacterial or fungal extracts, vitamins.

2. Products of the immune system: Lymphokines, growth factors, hormones.

3. Synthetic immunomodulators: Examples include Levamisole (for demodicosis), Isoprinosine (for bacterial & viral infections; increases specific Ab production), and Lactoferrin (protein of bovine origin; binds iron, reducing its availability for bacteria).

Define the 'Pre-epizootic process'.

The Pre-epizootic process (awakening period) is when population-specific immunity is reduced, the number of susceptible animals increases, and pathogenicity is at its highest.

Define 'indirect transmission' of disease.

Indirect transmission is the secondary or passive transmission of disease involving a vector, such as an inanimate object.

Which of the following are synthetic immunomodulators?

a. Glucans

b. Cyclophosphamide

c. Levamisole & Isoprinosine

c. Levamisole & Isoprinosine

glucans are natural, b is synthetic immunosuppressive.

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What indicates a positive result in a Hemagglutination Inhibition Test (HIT)?

Sedimentation of red blood cells (RBCs).

What is PCR (Polymerase Chain Reaction) used for?

PCR is used for the detection of etiological agents' nucleic acids.