DISEASE E&E (Introduction) Flashcards
Infection:
-invasion of an organism’s body tissue by disease-causing agents, their multiplication, and the reaction of host tissues to the infectious agents and the toxins they produce
Infectious disease:
-also known as transmissible disease or communicable disease
-illness resulting from an infection
What common words do we use for infectious agents?
-pathogens
-vector
-parasites
Pathogen:
-anything that can produce disease
Parasitism:
-a relationship between species where one organism (parasite) lives on or in another organism (host) causing it harm and is adapted structurally to this way of life
Parasite:
-any organism that decreases the fitness of its host by infecting it
-ecological definition includes both micro-parasites (ex. viruses and bacteria) and macro-parasites (ex. worms)
Examples of parasites:
-tape worm
-mites
-parasitoid wasp
-cuckoo
-ticks
-HIV
What is NOT an infectious disease?
-genetic (or hereditary) diseases (hemophilia)
-environmentally-caused diseases (scurvy)
*most disease have both genetic and environmental origins
Ecology:
-study of spatio-temporal distribution of infectious diseases
-reflects the interactions of host populations with pathogen (or parasite) populations in the environment over time
*emphasizes infectious diseases of animals
Epidemiology:
-branch of medicine
-deals with incidence, distribution and possible control of diseases and other factors relating to health
-includes non-infectious disease (smoking, addictions, obesity, etc.)
*human medicine and includes non-infectious diseases
The disease triangle:
-for a parasite to cause pathology, need:
>parasite
>susceptible host
>environmental conditions must be sufficient to result in disease
*3 critical elements
Importance of infectious diseases:
-cause morbidity and mortality in their hosts, reduce productivity of farm animals (cattle, sheep)
-stop trade and travel across international borders (BSE)
-threaten food security for people in developing world
-spillover of pathogens from wildlife to domestic animals
SARS-CoV-2:
-originated in wildlife (bats) before spilling over into humans
-maybe racoon dog was intermediate host?
Study of pathogens and infectious diseases in animals:
-domain of veterinarians and disease ecologists
2001 Foot-and-mouth outbreak in the UK:
-viral disease that affects cloven-hoofed animals
-no risk to humans (not zoonotic)
-over 2000 farms recorded cases
-highly contagious and difficult to stop
-economic cost to farming and tourism was $16billion USD
*example of how infectious disease can have devasting economic consequences
Rinderpest in Africa:
-highly infectious viral disease of cattle
-close cousin of Measles virus
-was brought to Ethiopia in 18880s by Italian colonists who imported infected cattle from India
-spread rapidly through eastern and southern Africa
-killed more than 90% of domestic cattle and huge numbers of wild ungulates (multi-host pathogen)
-1/3 of Ethiopians and 2/3 maasai in Tanzania starved to death
*how infectious diseases of livestock threaten food security
Multi-host pathogen:
-it can affect many different host species
-cattle and buffalo have mortality rates of ~100%
-sheep and goats less serious
-pigs and deer have asymptomatic disease
Host factors:
-species
-genotype/breed
-sex
-age
-nutritional condition
-immune status
2 types of cattle:
- Taurine (Bos Taurus)
- Zebu (Bos Indicus)
Taurine cattle:
-temperate climates (Europe, northern Asia, West Africa)
-European taurine: high milk yields, meat quality, etc
Zebu cattle:
-hot arid and semi-arid regions of Asia and Africa
-larger sweat glands and resistance to ticks
-lower water and fodder requirements
-stronger herding instincts
-different vocal sounds
-meat is tougher
Cattle breed and TB pathology:
-chronic disease
-most common mode of transmission: inhalation of droplets in aerosols and from ingestion of contaminated food and water
-infected taurine (Holstein) vs. Zebu (Boran) cattle with M. bovis and scored the lungs
>lung pathology higher in taurine vs. zebu
Covid mortality rate:
*depends on age
-increases as get older
-higher in males
Pathogen or parasite factors:
-pathogen species
-pathogen genotype/strain/isolate/variant
-infectivity/transmissibility
-burden/load/abundance
-infectious dose
-pathogenicity/virulence
-immune evasion
Infectivity:
-probability that pathogen will establish infection in host following exposure
Burden:
-number of pathogen units in host tissues
Pathogenicity:
-pathogen-induced damage or pathology in the host
Immune evasion:
-pathogen ability to avoid clearance by the host immune system
SARS-CoV-2 variant waves:
-multiple waves caused by different variants of concern (VOCs)
-many were short lived
-changes what you need in vaccine
-increased transmissibility
Why do we care about SARS-Cov-2 variants?
-variants with higher transmissibility will cause more cases
-variants with higher pathology will cause more severe disease
-vaccines based on older variants may not protect against newer variants
