Immunity and Infection Flashcards
global determinants of infectious disease in a herd/flock
exposure to infection, spread of infection within group, resistant to infection, and treatment of sick animals
exposure to infection
biosecurity and eradication
resistance to infection
genetic resistance to disease, colostral immunity, vaccination, environment, and nutrition
spread of infection within group
stocking density, reoval of sources of contamination, isolation of sick animals
treatment of sick animals
individual animal treatment, group treatment, antibiotics
infection and immunity balance
factors promoting infection balance with factors promoting immunity
factors promoting immunity
vaccines, limiting stress, biosecurity
opportunistic pathogens
not common infection but common in weak animal groups
highly pathogenic agents
cause disease in immune competent animals (EX: salmonella, pathogenic E. coli, influenza, anthrax)
less pathogenic agents
cause sever infections in immune deficient, immune competent may carry infection (EX: cryptosporidium, non-pathogenic E. coli)
what groups would be susceptible to opportunistic infections?
young animals, immunosuppressive drugs, pregnant animals
the major components of defense
physical and chemical barriers to infection, innate immune responses, and acquired immune responses
first line of defense
physical and chemical barriers
physical and chemical barriers examples
nasal cavity traps inhaled microorganisms, antimicrobial protein in saliva and tears, trachea and lung epithelial barrier, skin barrier, intestinal epithelial barrier
respiratory barriers
nasal cavity and muco-ciliary escalator
respiratory barriers: nasal cavity
nasal turbinate bones have lots of surface area and trap large particles of dust and bacteria, viruses and fungi
respiratory barriers: muco-ciliary escalator
lining of the airway has lots of mucous, mucous catches the bacteria and cilia move the bacteria up to be coughed out
what environmental conditions influence the efficacy of the muco-cilary escalator?
drop in humidity and drop in temperature decrease transport velocity and impair muco-ciliary clearance
viruses can damage physical barriers
bovine respiratory disease complex, viruses damage respiratory epithelium and impair muco-ciliary clearance increasing the risk of bacterial pneumonia.
innate immunity specificity
non-specific responses
adaptive immunity specificity
pathogen specific responses
innate immunity adaptability
response is not more effective on second exposure to pathogen
adaptive immunity adaptability
improved response on second exposure to pathogen
innate immunity speed
activated in minutes, important during initial/early infection
adaptive immunity speed
days to weeks for full immunity
innate immunity defense
complement proteins, lysozyme in milk, saliva, and tears, lactoferrin in saliva
adaptive immunity defense
antibody dependent, cell mediated immunity
acute
short duration or sudden onset
itis
inflammation
innate immunity: acute inflammation
acute mastitis from staphylococcal infection, acute pneumonia from mannheimiosis, acute enteritis from salmonella
what are 5 signs of acute inflammation?
redness, swelling, heat, pain, and loss of function
what are the key phagocyte cell types involved in innate immunity?
neutrophils and macrophages
what do neutrophils do?
isolate and destroy disease causing microorganisms
innate immunity neutrophil defense
draining of pus onto surface of site of inflammation, focal accumulation of pus in tissue cavities (abscessation), phagocytize bacteria
outcomes of acute infection in individual animals
local acute inflammation can lead to recovery and reduced productivity and tissue damage or systemic inflammation and death
what are examples of reduced productivity?
growth, milk yield, fertility
adaptive immunity key cells
lymphocytes
humoral immunity
antibodies bind to pathogens in body fluids
cell mediated immunity
immunity against intracellular pathogens
humoral immunity defined
production of antibodies by plasma cells, antibody mediated, B lymphocytes differentiate into antibody mediating cells
B cells
named from the bursa of fabricius in the bird, made in bone marrow of mammals and develop into plasma cells
antibody types
five major classes of antibody, IgA, IgM, IgG, IgE
IgA
important for mucosal immunity, respiratory and GI tracts
IgM
often first to be produced following infection, early in infection, valuable for diagnostics
IgG
most abundant in the body, used for quantification of antibodies in the blood
IgE
important for immunity to multicellular parasites
what do antibodies do?
bind extracellular pathogens and mediate destruction, promote phagocytosis by bringing antigens close to phagocytes
passively acquired immunity
maternal transfer and injection of antibodies
passive maternal transfer
placental transfer of antibodies and colostral transfer of antibodies
passive injection of antibodies
antitoxins are used during outbreaks of enterotoxemia types C and D, generally doesn’t work well, used as treatment rather than prevention
relationship between serum IgG and survival in calves
higher IgG leads to greater survival rates of calves
passive transfer of antibodies via placenta is species dependent
ruminants and pigs are born without any IgG in the blood, mothers do not pass IgG through the placenta, humans and rodents have placental crossover of IgG due to fewer layers of placenta to maternal antibodies
colostral antibody absorption is time dependent
the sooner the better, first 24 hours of life IgG can be absorbed, IgG broken down if given late
how are antibodies absorbed from colostrum into the blood stream?
endocytosis of the intestinal epithelium
failure of passive transfer
important predisposing factor to infectious disease in neonatal ruminants, piglets, and foals, major risk for neonatal disease
colostrum failure of passive transfer predisposing factors
insufficient colostrum, ingested too late resulting in poor absorption, mother not exposed to relevant pathogens, mother in poor condition not producing milk, unhealthy neonate not wanting to drink milk
passive immunity wanes
in the first weeks of life
how long does passive immunity need to last?
it needs to last until adaptive immunity has to developed so an animal is not susceptible disease
why is initial intake of colostrum important?
sufficient intake is important, if initial intake is low there will be a gap where antibody is low before the animal develops adaptive immunity
T lymphocytes
develop in the thymus, key role in cell mediated immunity
cell mediated immunity and killing
mediated by T cells, antibody independent, important for defense against intracellular pathogens
diagnostic use of adaptive immune responses
useful when infectious agent is difficult to detect or tissue samples are unavailable, serological diagnosis of disease, skin testing for tuberculosis
leptospira in cattle disease sign
anemia, jaundice, red urine, nephritis
rising antibody titer in graphs
demonstrates exposure to the pathogen and body producing antibodies, or building antibodies from vaccine
single antibody titers
of limited use for acute infections
paired titers
important for diagnosis of infectious diseases, enables confirmation of recent infection when initial results were negative, takes 2 weeks to obtain
single titers are valuable for
detecting disease where there has been no vaccination, like surveillance of foreign animal diseases
