Viral and non-viral pathogens

VIRAL DISEASES

Older Diseases

• Rabies, Measles, Mumps, Rubella, Polio

• Controlled/prevented via widespread vaccination

Re-emerging Diseases

• AIDS (HIV), Ebola, Monkeypox

• Often zoonotic or due to breakdown in public health measures

RHABDOVIRUSES (Group V: -ssRNA)

Example: Rabies virus

• Wide host range

• Infects peripheral nervous system → CNS (brain) → causes encephalitis

Rabies Replication:

1. RNA-polymerase produces mRNA (+ssRNA)

2. Host translates mRNA into proteins

3. Replication of +ssRNA and -ssRNA

4. Assembly of new virions

Forms of rabies

Furious rabies - behavioural changes

Dumb rabies (paralytic)

MONKEYPOX (Group I: dsDNA)

Transmission:

• Zoonotic: bites, scratches, handling infected animals

• Human-to-human: contact with lesions, contaminated objects (fomites)

Vaccines:

• ACAM2000 – live vaccinia virus

• Modified Vaccinia Ankara (MVA)

• LC16m8 – licensed in Japan

VIROIDS

• Smallest pathogens

• Circular ssRNA, naked, no capsid

• Infect plants only

• No proteins coded, replicate autonomously

• Resistant to nucleases/proteases

• Mode of action unknown

OBELISKS

• Viroid-like elements in humans (recently discovered)

• Circular RNA, predicted rod-like secondary structure

• Found in oral and metatranscriptomic data

PRIONS

• Infectious proteins (no DNA/RNA)

• Resistant to inactivation

• Misfolded form: PrPᵖˢᶜ

• Normal form: PrPᶜ (253 amino acids)

Diseases (Spongiform Encephalopathies):

Animals:

• Scrapie: sheep/goats – fatal CNS degeneration

• BSE: cattle – “Mad cow disease

  Humans:

• Kuru: tremors, neurodegeneration (ritual cannibalism origin)

• CJD (Creutzfeld-Jakob Disease): memory loss, motor issues

  • Most common form: Sporadic CJD (sCJD)