Infectious diseases in beef cattle
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What is one of the most common maladies in newborn calves (less than 28-30 days old)?
What percentage of calves will die from scours in the US each year?
What percentage of death losses between birth and 30 days are due to scours in AB?
What are the economic losses for a scouring calf?
$150-200/calf - include cost of dead calves, stunted calves, labour and medication
What is the cause of scours?
- Interaction between host, enviro and pathogens.
- Usually combination of viruses, bacteria and protozoa
scours agent responsible for watery brown to light green feces, blood and mucus
most commonly 1-6 days
Scours agent responsible for effortless passing of yellow to white feces
Most commonly 1-7 days
K 99 E. Coli
Scours agent responsible for watery yellow feces
Most commonly 7-10 days
Scours agent responsible for sudden death and blood tinged diarrhea
most commonly 7-28 days
Clostridium perfringens Type C
Scours agent responsible for watery brown to light green feces, blood and mucus
most commonly 7-21 days
Scours agent responsible for blood-tinged diarrhea
most commonly 7 days and after
Scours agent similar to E.coli with yellow to white feces
Most commonly 1-7 days
What are three factors contributing to scours?
- cold, wet weather
- Sanitation- crowded housing
- Nutrition- adequate amount of colostrum
What is considered an adequate amount of good colostrum?
10% of calf body weight in 12 hours
Four methods to treat calf scours?
- provide stress-free environment
- treat with antimicrobials- protect against secondary infections
- fluid and electrolyte therapy (oral or IV)
List 5 ways to prevent/manage scours
- separate healthy from sick animals
- ensure healthy animals are moved to a clean pasture with fresh bedding in calving area
- good sanitation- clean equipment, animal handlers
- Health cows: good body scores, better calving, less diarrhea
- Vaccinate cows prior to calving- (dead vacc)
Another name for bovine respiratory disease?
Describe shipping fever.
Pneumonia associated with the assembly of large groups of calves into feedlots from diverse genetic, nutritional and geographic backgrounds
How long after the assembly into a feedlot is shipping fever normally seen in calves?
What is the morbidity rate of shipping fever?
What is the mortality rate of shipping fever?
What are the two causes of primary infection in shipping fever?
- A viral pathogen
- Mycoplasma sp
What are some examples of viral pathogens that may cause shipping fever?
- Bovine Herpes virus I- Infectious Bovine Rhinotracheitis (IBR)
- Bovine Viral diarrhea Virus (BVDV): Togavirus
- Bovine respiratory virus- paramyxovirus
- Bovine Parainfluenza Virus (PI-3)- paramyxovirus
An example of a mycoplasma that causes shipping fever?
List three causes of secondary infection from shipping fever.
- Mannheimia (pasteurella) hemolytica
- Histophilus (Hemopholus) somni
- Pasteurella multocida
What is fibrino-plueropneumonia?
Infection of the lungs and pleural space.
List 7 non-cellular immunity mechanisms.
- Barriers: skin mucosa
- Enzymes/Proteins: reduce bacterial growth
- Secretions: stomach acid
- Physical Responses: cough reflexes
- Complement cascade: membrane attack complex
- Acute phase Proteins: inhibit or destroy microbes
List 5 cellular immunity mechanisms.
- Antigen-presenting cells (dendrites): links innate to adaptive immunity
- Macrophages and Granulocytes: digests and destroys pathogens
- NK cells: tumor surveillance and intracellular pathogens
- yo T cells: bacterial infections
- Cytokine: regulate adaptive and innate immune responses
Whats the difference between adaptive and innate immunity?
- Innate- generalized and no memory
- Adaptive- specific and has immunological memory
What do B Cells do?
Two types of antibodies produced by B-cells?
- Soluble- binds to pathogen and signals its destruction
- Membrane bound- B-cell receptor for antigen
What are T-cells used for?
central role in cell mediated immunity
Two types of T-cells?
- CD4 MHC-II: important to control adaptive immune response
- CD8 MHC-II: important for intracellular pathogens and tumors
What are the 5 strategies to induce disease evasion of innate immunity?
- 1. Interference of physical barrier (lung)
- 2. Interference with phagocytosis
- 3. Interference with extracellular killing
- 4. Interference with INF (interferons)
- 5. Regulation of apoptosis
Give an example of a disease that interferes with a physical barrier.
Bovine Herpes-I: infects respiratory epithelium and goblet cells (prod. mucous), results in injury of epithelial tissue and lymphoid tissue
Give an example of a disease that interferes with phagocytosis.
Histophilus somni: Induces apoptosis when engulfed by phagocytic cell reducing capacity of phagocytosis. Organism releases an exopolysaccharide that may impair intracellular phagocytic mechanisms.
Give an example of a disease that interferes with intracellular killing.
Bovine Parainfluenza 3 (PI-3): inhibits superoxide anion production in alveolar macrophages without destroying macrophage- allows pathogenic bacteria to propagate.
Give an example of a disease that interferes with interferons.
Bovine viral diarrhea virus (BVDV)- the amino-terminal of BVDV virus inhibits (IRF3) from binding to IFN promoter
Give an example of a disease that interferes with regulation of apoptosis.
Bovine Herpes Virus 1: will induce epithelial cell at the end of the viral replication. ensures increased numbers of viral particles (delays apoptosis until ready to replicate) OR induces latency in neurons, which stops apoptosis until reactivation.
List 7 strategies to induce disease evasion in adaptive immunity.
- 1. Suppression of lymphocyte proliferation
- 2. Induction of humoral and cellular immune tolerance
- 3. Down regulation of MHC-II molecules
- 4. Inhibition of antibody production and antibody effectiveness
- 5. Loss of CD4 T cell function: loss of CD4 molecules will alter immune function
- 6. Interference with Cytoxic T cell (CTL) function
- 7. Shut down of protein synthesis: protein synthesis is needed to generate molecules used in immune function (MHC 1&2, cytokines, chemokines etc.)
Give an example of a disease that can suppress lymphocyte proliferation.
Bovine Herpes Virus-1: Epithelial cells infected with IBR have reduced responses to mitogens
Give an example of a disease that can induce humoral and cellular immune tolerance.
BVDV causing mucosal disease: Cytopathic form causes calf to become immunodeficient and prevents an immune response
Give an example of a disease that can induce down regulation of MHC-II molecules
Leukotoxin of Mannheimia (Pasteurella) hemolytica: decreases the expression of MHC-II molecules on antigen-presenting cells, which allows organism to grow in tissue
Give an example of a disease that induces the inhibition of antibody production and antibody effectiveness.
Histophilus somni: secretes proteins that bind to IgG2 antibodies in a non-specific manner.
Give an example of a disease that induces the loss of CD4 T cell function.
IBR: will induce the loss of CD4 molecules on lymphocytes and subsequent induction of apoptosis of these lymphocytes. There is CD4 in peripheral blood and lymph nodes
Give an example of a disease that induces interference with cytotoxic T Cell function
IBR: produces proteins that inhibit cellular processes and down regulate MHC-II and antigen presented in MCH-I molecules and thus escape CTL induced death.
Give an example of a disease that induces the shut down of protein synthesis.
IBR: produces 'virion host shut-off protein' that reduces protein synthesis by degrading mRNA of cellular protein.
What is a strategy to induce disease change in a pathogen?
Antigenic variation (shift): organisms can change the structure of surface membranes.
Give two examples of organisms that can change the structure of surface membranes.
- 1) Mycoplasma bovis: can reduce and shorten its surface proteins and if there is a drop in # of neutralizing antibodies (immunity decreases) the proteins will revert back to original form.
- 2) Histophilus somni: Glycoses and phosphoryl choline of its LPS will randomly vary. If this occurs at multiple sites the organism can evade antibody immune responses.
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