Zoonotic Diseases

Zoonoses Overview & Bacterial Zoonoses - Beastly Bugs

• Zoonoses Overview:
  • Definition: Diseases from vertebrate animals to humans.
  • Classification: By agent, reservoir, transmission cycle.
  • Transmission: Direct contact, bites, aerosols, ingestion, vectors.
• Key Bacterial Zoonoses: 📌 Mnemonic: B.L.P.A. (Brucellosis, Leptospirosis, Plague, Anthrax)
  • Brucellosis ("Undulant Fever"):
    • Agent: Brucella spp.
    • Reservoir: Cattle, goats, pigs.
    • Transmission: Unpasteurized dairy, contact.
    • Clinical: Undulant fever, arthralgia, sweats.
    • Dx: SAT, Blood culture.
    • Prev: Pasteurization.
  • Leptospirosis ("Weil's Disease"):
    • Agent: Leptospira interrogans.
    • Reservoir: Rodents (urine), domestic animals.
    • Transmission: Contaminated water/soil.
    • Clinical: Biphasic; Weil's: jaundice, renal failure, hemorrhage.
    • Dx: MAT, PCR.
    • Prev: Rodent control, PPE.
  • Plague:
    • Agent: Yersinia pestis.
    • Reservoir: Rodents; Vector: Fleas.
    • Transmission: Flea bite, aerosol (pneumonic).
    • Clinical: Bubonic (bubo), Septicemic, Pneumonic.
    • Dx: Bipolar stain (microscopy), culture.
    • Prev: Rodent/flea control.
  • Anthrax:
    • Agent: Bacillus anthracis (spores).
    • Reservoir: Herbivores, soil.
    • Transmission: Spore contact (cutaneous, inhalation, ingestion).
    • Clinical: Cutaneous (painless eschar), Inhalational (widened mediastinum), GI.
    • Dx: Gram stain (box-car bacilli), culture.
    • Prev: Animal vaccination, PEP.

⭐ Plague: Yersinia pestis shows bipolar "safety-pin" appearance on Wayson or Giemsa stain.

Viral & Rickettsial Zoonoses - Tiny Terrors

Viral Zoonoses

• Rabies (Hydrophobia)
  • Agent: Lyssavirus. Transmission: Animal bite.
  • Key: Hydrophobia, Negri bodies.
  • PEP: Wound wash, Vaccine, RIG.
    • Cat I (touch/lick intact skin): No PEP.
    • Cat II (nibble/minor scratch, no bleed): Vaccine.
    • Cat III (transdermal bite/scratch, lick broken skin, mucous membrane, bat): Vaccine + RIG.

%%{init: {'flowchart': {'htmlLabels': true}}}%% flowchart TD

Start["🐾 Animal Bite
• Exposure event• Risk assessment"]

Assess["📋 Category?
• WHO risk levels• Evaluation needed"]

Cat1["🩹 Category I
• Skin remains intact• Touching or licks"]

Cat2["🩹 Category II
• Minor nibbles• Scratch no bleed"]

Cat3["🩹 Category III
• Transdermal bites• Mucous membranes"]

NoPep["✅ No PEP
• No active treatment• Local hygiene only"]

WashVac["💊 PEP Level 1
• Wound washing• Rabies vaccine"]

WashVacRig["⚠️ PEP Level 2
• Wash and Vaccine• Give Rabies RIG"]

Start --> Assess Assess --> Cat1 Assess --> Cat2 Assess --> Cat3

Cat1 --> NoPep Cat2 --> WashVac Cat3 --> WashVacRig

style Start fill:#F7F5FD, stroke:#F0EDFA, stroke-width:1.5px, rx:12, ry:12, color:#6B21A8 style Assess fill:#FEF8EC, stroke:#FBECCA, stroke-width:1.5px, rx:12, ry:12, color:#854D0E style Cat1 fill:#F6F5F5, stroke:#E7E6E6, stroke-width:1.5px, rx:12, ry:12, color:#525252 style Cat2 fill:#F6F5F5, stroke:#E7E6E6, stroke-width:1.5px, rx:12, ry:12, color:#525252 style Cat3 fill:#F6F5F5, stroke:#E7E6E6, stroke-width:1.5px, rx:12, ry:12, color:#525252 style NoPep fill:#F6F5F5, stroke:#E7E6E6, stroke-width:1.5px, rx:12, ry:12, color:#525252 style WashVac fill:#F1FCF5, stroke:#BEF4D8, stroke-width:1.5px, rx:12, ry:12, color:#166534 style WashVacRig fill:#FDF4F3, stroke:#FCE6E4, stroke-width:1.5px, rx:12, ry:12, color:#B91C1C

    *   ![Rabies Postexposure Prophylaxis Clinical Pathway](https://ylbwdadhbcjolwylidja.supabase.co/storage/v1/object/public/notes/L1/Community_Medicine_Infectious_Diseases_Zoonotic_Diseases/e7073b26-e00b-4c36-a0ac-eb9f2af5f22f.png)
*   **Kyasanur Forest Disease (KFD)**
    *   Agent: Flavivirus. Vector: *Haemaphysalis spinigera* ticks. Reservoir: Rodents; Monkeys amplify.
    *   Key: Biphasic fever, hemorrhagic, neuro. Karnataka.
*   **Japanese Encephalitis (JE)** (Zoonotic aspect)
    *   Agent: Flavivirus. Vector: *Culex* spp. Hosts: Pigs, birds. Man dead-end.

**Rickettsial Zoonoses**
*   Diagnostic aid: Weil-Felix test (agglutination with *Proteus* antigens).
*   **Scrub Typhus**
    *   Agent: *Orientia tsutsugamushi*. Vector: Chiggers (larval trombiculid mites).
    *   Key: Eschar, rash, fever. Weil-Felix: OX-K (+).
*   **Indian Tick Typhus**
    *   Agent: *Rickettsia conorii*. Vector: Ticks.
    *   Key: Eschar, rash (palms/soles). Weil-Felix: OX-19, OX-2 (+).

> ⭐ Rabies is nearly **100%** fatal once clinical symptoms appear, but **100%** preventable with prompt and appropriate Post-Exposure Prophylaxis (PEP).

## Parasitic Zoonoses & General Control - Bug Busters

*   **Hydatid Disease (*Echinococcus granulosus*)**
    *   Agent: *E. granulosus* (dog tapeworm)
    *   Host: Dog (Definitive), Sheep/Human (Intermediate)
    *   Transmission: Ingestion of eggs (food/water)
    *   Clinical: Liver/lung cysts; rupture → anaphylaxis
    *   Dx: Imaging (USG/CT), serology
    *   Prevent: Deworm dogs, hygiene
*   **Cysticercosis/Taeniasis (*Taenia solium*)**
    *   Agent: *T. solium* (pork tapeworm)
    *   Host: Human (Definitive for taeniasis; Intermediate for cysticercosis), Pig (Intermediate)
    *   Transmission: Taeniasis (undercooked pork); Cysticercosis (eggs via fecal-oral)
    *   Clinical: Neurocysticercosis (seizures, headache)
    *   Dx: Brain imaging (CT/MRI), serology
    *   Prevent: Cook pork thoroughly, sanitation
    ![Taenia solium lifecycle and control measures](https://ylbwdadhbcjolwylidja.supabase.co/storage/v1/object/public/notes/L1/Community_Medicine_Infectious_Diseases_Zoonotic_Diseases/877c6420-8648-4e54-a92a-8b1b4632436d.gif)
*   **Toxoplasmosis (*Toxoplasma gondii*)**
    *   Agent: *T. gondii*
    *   Host: Cat (Definitive), Human/mammals/birds (Intermediate)
    *   Transmission: Oocysts (cat feces), undercooked meat, transplacental
    *   Clinical: Mostly asymptomatic; Congenital (chorioretinitis, hydrocephalus)
    *   Dx: Serology (IgM/IgG)
    *   Prevent: Cook meat, careful cat litter handling (pregnant women)

*   **General Control Principles**
    *   One Health Approach: Integrated human-animal-environment health
    *   Surveillance & Reporting: Early detection, rapid response
    *   Inter-sectoral Coordination: Health, veterinary, wildlife sectors collaboration
    *   Health Education: Community awareness on transmission & prevention
    *   India Example: National Rabies Control Programme (also benefits other zoonoses control)
    > ⭐ Neurocysticercosis is the most common parasitic infection of the brain globally and a leading cause of acquired epilepsy in endemic areas.


##  High‑Yield Points - ⚡ Biggest Takeaways
> * **Rabies**: **Animal bites**; **Negri bodies** pathognomonic; crucial **Post-Exposure Prophylaxis (PEP)**.
> * **Brucellosis**: **Undulant fever**; linked to **unpasteurized dairy** or direct **animal contact**.
> * **Leptospirosis**: **Weil's disease** (jaundice, renal failure); exposure to **rodent urine/contaminated water**.
> * **Plague (Yersinia pestis)**: **Bubonic plague** commonest; transmitted by **rat fleas**.
> * **Kyasanur Forest Disease (KFD)**: **Tick-borne viral hemorrhagic fever**; endemic to **Karnataka**.
> * **Japanese Encephalitis (JE)**: **Culex mosquito-borne**; **pigs** are amplifying hosts; causes **encephalitis**.
> * **Anthrax**: **Malignant pustule** (cutaneous); **wool-sorter's disease** (inhalational).