- Pathogen & Disease -

UNIT 4 Bio

Zoonoses ?

Infectious diseases that can be transmitted from one vertebrate group to another.

Pathogen ?

An infectious agent that causes disease

Viral structural features :

• Protein coat (capsid) and nucleic acid (DNA/RNA)

• Relatively small: 30-300 nanometers

• Recognize and bind to receptors

• Requires host cell to replicate

Examples of diseases caused by virus :

• Influenza 🐷→ 🧑

• Ross River Virus 🌾

• Viral disease of Honeybees 🐝

Ross River Disease

• Indirect via vector → female mosquito & reservoirs 🦟

• Via skin during blood feed, saliva into human ; blood into mosquito

• IMPACT - rash on limbs, painful swollen joints, fever and headaches 🤒

• Not contagious ❌

Deformed Wing Virus

• Indirect => varroa bite into bee (vector)

• Direct => transmission from Queen bee to offspring 👑 🐝

• Varroa bites into them and transmits virus into blood of bee

• IMPACT -

• stressing them out 😵‍💫, shriveled wings, bloated abdomens , decreased size …

Influenza

Direct → skin-to-skin

Indirect → fomite transfer, objects …

• It replicates in epithelial cells through respiratory system

IMPACT :

• Lethargy , cough, sneeze , fever

Bacteria features :

• PROKARYOTIC

• Uni - cellular

• No membrane bound organelles

• Circular DNA & plasmid

• Flagella for movement

• 1-10 micrometers

• cell wall (peptidoglycan)

Tuberculosis (TB)

Direct → Close contact

Indirect → Droplets from fomites

• Entry via respiratory

• Replication in alveolar macrophage

• Exit via cough / sneeze

IMPACT

• Persistent cough 😷, sputum 🩸, fever, loss of weight

Crown gall of plants

Direct → roots touching

Indirect → Human activities (from vehicle )

• Enters through a wound

• Induced growth of tumor-like galls around the stem. This is done when it inserts gene into genome of host cell causing the rapid growth of cells.

IMPACT

• ‘Gall‘ is formed (undifferentiated cells) and stunted growth . Death 😔🍃🪦

Bacteria reproduction by Binary fission

One cell splits into two identical daughter cells. 👧 👧 !

Binary fission begins when the DNA of the bacterium doubles in quantity then divides into two (replicates) 🧬→ 🧬

The bacterial cell then elongates and splits into two daughter cells, each with DNA that is identical to that of the parent cell

Fungi

UNICELLULAR & MULTICELLULAR

Cell walls (Chitin)

Zoospores a motile, asexual reproductive spore

Hyphae filaments (mycelium)

Micro-flaments (Hyphae)

Chyridiomycosis 🍄

Indirect → water or soil borne (spores motile)

Direct → Skin 🐸

Via motile zoospores which enter susceptible host skin

IMPACT :

• Amphibian skin is hardened, blocked gas exchange and lethargy

Protists

2 um to 1000 um

unicellular & multicellular

Cell wall

Eukaryotes with membrane bound organelles

Asexual & Sexual reproduction

Plasmodium are animal -like

• Cillia, flagella, pseudopodia can be present

Zoospores

Malaria ⭕

Indirect → Vector

Direct → Mixing of fluids

• Female pregnant mosquito during blood feed

• Saliva containing protist enters blood stream through exchange of fluids 🦠💧< — >🩸

IMPACT :

• Fever and chills

• Fatigue

• Anemia

• Death