Infectious and Non-Infectious Disease Definitions (University of Alberta) PDF

INFECTIOUS & NON-INFECTIOUS DISEASE September 23, 2024 Today’s objectives Be able to define non-infectious and infectious diseases Demonstrate an understanding of non- infectious and infectious disease basic processes Identify the main categories of infectious disease: bacteria, virus...

INFECTIOUS & NON-INFECTIOUS DISEASE September 23, 2024 Today’s objectives Be able to define non-infectious and infectious diseases Demonstrate an understanding of non- infectious and infectious disease basic processes Identify the main categories of infectious disease: bacteria, virus, fungal, parasitic 2 Some terminology to know Infectious disease: illness caused by pathogens Example: influenza Non-infectious disease: illness resulting from causes other than pathogens Example: cancer Be careful: is pneumonia infectious or non-infectious? 3 Some terminology to know Pathogenicity: the level of ability of a pathogen to cause disease Example: commensal bacteria are non-pathogenic while E.coli O157 is highly pathogenic Transmissible (contagious): able to be spread from one individual to another either directly or indirectly 4 How infection develops 5 Preclinical phase = incubation period 6 The infectious period = when disease is transmissible ie; contagious 7 Two types of infection: Type A and Type B 8 Two types of infection: Type A and Type B 9 Why is this important? Can you explain this? 11 Part of how you feel when sick is because of your immune system! Viruses, bacteria, fungi, parasites Viruses 14  Viruses Most abundant biological entity on earth Consists of a protein coat (capsid), envelope (not all), core of DNA or RNA Requires a host cell to replicate (bacteria, animal or plant Most viruses cause disease ie; they are not commensal Each particle called a “virion” 15 Viruses Structure of virus helps evade immune system and resist destruction → Enveloped easier to kill with alcohol 16 Viruses 1. Entry 2. Release DNA or RNA 3. Hijack host cell machinery for replication 4. Latency period 5. Shedding of viral particles 17 Some DNA virus examples -Pox viruses (first virus ever seen via miscroscope): cow pox, monkeypox, small pox, myxoma virus → many are zoonotic -Parvo viruses: can infect a variety of hosts including dogs, pigs, humans, rats, ferrets -Herpes viruses: infect almost every species and considered “endemic” --> evade the immune system by down regulating MHC 18 Some RNA virus examples -Rhabdoviruses: Rabies -Corona viruses: Covid-19! Retrovirus: FIV, Avian influenza 19 Why are RNA viruses so problematic? They are “shapeshifters”: genome mutation and genome reassortment Immune cell memory ineffective because the antigen changes so frequently Need to be making new vaccines → not always feasible 20 Mutation 21 Genome Reassortment 22 Treatment and prevention of viral infection Supportive therapy Sometimes anti-virals Vaccination → herd immunity Good management 23  Prokaryotic: single celled organism that do not have a nucleus, mitochondria, or any other membrane bound organelles Free living Fewer than 100 species known to cause disease Commensal: we live symbiotically with most 25 Bacteria is essential for health Commensal bacteria required in the rumen of cattle, sheep and goats and the caecum of horses and rabbits to breakdown cellulose Required for the normal function of the gut and immune system 26 27 28 29 30 31 Gram staining done in clinic to identify bacteria quickly 32 33 Why is gram staining important? 34 35 36 37  Fungi Eukaryotic: yeasts, mold, mushrooms ~144,000 species w/ ~100 species pathogenic to humans and animals Some cause “mycosis” or “mycotoxicosis” Some are commensal such as Malasessezia: Can overgrow and cause “yeast infection” Many antimicrobials from yeast Yeast are thought to be important to maintaining ecosystem of microbiome 38 Protozoa Single celled eukaryotic organism Examples: giardia, coccidiosis, cryptosporidium Most cause diarrhea Treatment: some antimicrobials Resistance developing 39 Helminths 40 41 42 Antihelminthic resistance Worms are becoming resistance due to indiscriminate anti- helminthic use Should test for helminths and treat appropriately 43 44 Announcements No labs this week, but there will be a quiz! Wednesday: guest lecturer Dr. Christina Osborne