Midterm 2 - Lecture 9 Flashcards
What is calf scours also known as?
Undifferentiated diarrhea in new born calves
Calf Scours
- major economic losses
- multiple agents cause the disease
- related to interactions btw host, agent, and enviro
Signs of an E.coli agent for calf scours
- effortless passing of yellow to white feces
- releases a toxin that binds to the cell to increase all the water into the intestine = dehydration
Signs of a Salmonella agent for calf scours
- similar to E.coli; yellow to white feces, possible blood
- obliterates the villi (which is the barrier to pathogens and bacteria coming in)
- ‘gut buster’
- zoonotic
Signs of a Coccidia agent for calf scours
- blood-tinged diarrhea
- ‘drills holes’ in the mucosa for bacteria to come in
Signs of a Cryptosporidium for calf scours
- watery brown to light green feces, blood and mucus
- zoonotic
- tiny protozoa
- defaces brush border around each villi
Contributing factors for calf scours
- cold, wet weather
- sanitation: crowded housing = sick animals in close proximity
- nutrition of both dam and calf
Medical treatment and prevention of calf scours
- stress free clean enviro
- treat with antimicrobial to protect against secondary infections
- fluid and electrolyte therapy
- colostrum
Management and prevention of calf scours
- separate healthy cow/calf from sick to clean pasture
- good sanitation of equipment and handlers
- healthy cows
- vaccinate cows prior to calving; antibodies passed to calf in colostrum
What is shipping fever also known as?
Bovine Respiratory Disease
What is Bovine Respiratory Disease?
- shipping fever pneumonia is associated with the assembly into feedlots of large groups of calves from diverse geographic, nutritional, and genetic backgrounds
- typically seen in feeder calves 7-10 days after feedlot assembly
What are the primary infection agents of shipping fever?
know how to spell these
1) insult with viral pathogen
- Bovine Herpes Virus-I
- Bovine Viral Diarrhea Virus
- Bovine Respiratory Syncytial Virus
- Bovine Parainfluenza Virus
2) and/or:
- Mycoplasma sp
What agents induce a secondary infection following shipping fever?
- Mannheimia hemolytica
- Histophilus somni
- Pasteurella multocida
Innate immunity
- generalized process, no immunological memory
- composed of 2 components:
1. non-cellular = barriers, enzymes/proteins, secretion, reflexes, complement cascades
2. cellular = antigen-presenting cells, macrophages and granulocytes, NK cells, cytokine
Adaptive immunity
- specific and has immunological memory
- B cells: produce antibodies
- T cells: control adaptive immune response
5 strategies to induce disease evasion of innate immunity
- Interference of physical barrier (lung)
- respiratory epithelia cells provides mechanical, chemical, and microbial barriers - Interference with phagocytosis
- phagocytosis is an important component of innate immune defense - Interference with intracellular killing
- phagocytic cells produce toxin compounds important for destroying bacteria - Interference with INF (interferons)
- INF: antiviral and induce/enhance immune fxns; reduce viral replication and cell-cell transmission - Regulation of Apoptosis
- viral-induced cell death important to prevent viral proliferation cell-cell transmission
Agent that infers with the physical barrier
Bovine herpes-I
- infects respiratory epithelium and goblet cells
- results in injury of epithelial barrier of epithelium and associated lymphoid tissue
- allows bacterial pathogens to invade from nasopharynx
What agent interferes with phagocytosis?
- Histophilus (Hemophilus) somni: when engulfed by phagocytic cells it induces apoptosis and reduces capacity of phagocytosis
What agent interferes with intracellular killing?
- Mycoplasma bovis: impairs intracellular signaling to alter a myeloperoxidase enzymatic response
What agent interferes with interferons?
Bovine Viral Diarrhea Virus
- the amino-terminal of BVDV inhibits IRF3 from binding to INF promoter
What agent interferes with the regulation of apoptosis?
Bovine Herpes Virus-I
- will induce apoptosis in epithelial cell at the end of viral replication = ensures increased numbers of viral particles
What are 7 strategies to induce disease evasion of adaptive immunity?
- Suppression of lymphocyte proliferation
- Induction of humoral and cellular immune tolerance
- Down regulation of MHC-II molecules
- Inhibition of antibody production and effectiveness
- Loss of CD4 T cell fxn: loss of CD4 molecules will alter immune fxn
- Interference with cytotoxic T cell fxn
- Shut down protein synthesis
What agent suppresses lymphocyte proliferation?
Bovine Viral Diarrhea Virus
- infects antigen-presenting cells and will reduce the clonal expansion of CD4-T cells
What agent induces humoral and cellular immune tolerance?
Bovine Viral Diarrhea Virus
- Mucosal disease = non-cytopathic form infects fetus and there is a reductions in INF production, the virus then replicates in tissues unrestricted
- Cytopathic form: Calf now has a lot of virus to induce immunotolerance (recognize as self) and ‘tolerized CD4-Tcells’; exposed to cytopathic form and cannot mount an immune response
What agent induces down regulation of MHC-II molecules?
Leukotoxin of Mannheimia hemolytica
- will decrease the expression of MHC-II molecules on antigen-presenting cells, allowing the organism to grow in tissue
- MHC-II needed to activate CD4-T cells and provide help to B cells
What agent inhibits antibody production/effectiveness?
Histophilus somni
- secrete proteins that bind to IgG2 antibodies in a non-specific manner
What agent induces the loss of CD4 T cell fxn?
Bovine Herpes Virus-I
- will induce the loss of CD4 molecules on lymphocytes and subsequent induction of apoptosis of these lymphocytes
- there is CD4 lympholysis in peripheral blood and lymph nodes
What agent interferes with cytotoxic T cell fxn?
Bovine Herpes Virus-I
- produces proteins that inhibits cellular processes and down regulates MHC-II and antigen presented in MCH-I molecules and thus escape CTL induced cell death
- MHC-I molecules are needed for CD8 T cells to eliminate virally infected cells
What antigen shuts down protein synthesis?
Bovine Herpes Virus-I
- produces ‘virion host shut-off protein’ that reduce protein synthesis by degrading mRNA of cellular protein
- protein synthesis is needed to generate molecules used in immune fxn
What strategy is used to induce disease change in the pathogen?
Antigenic variation (shift)
- organisms can change the structure of surface membranes
What agent induces antigenic variation?
Mycoplasma bovis
- can reduce and shorten surface proteins and if the immunity in the calf wanes the surface proteins will revert back to its original form
