Which phase of FMD infection involves the development of... | Agrigyan

• Chronological Progression of Rabies Clinical Signs:

• Behavioral changes (Prodromal Stage, 1--3 days): Characterized by personality reversals (affectionate animals become shy/withdrawn, aggressive animals become docile, wild animals lose fear of humans), slight fever, pupillary dilation, and licking the inoculation site.
• Excessive salivation (Excitative / Furious Stage): Exaggerated sensory reactivity, agitation, biting inanimate objects, and pronounced hypersalivation (due to painful pharyngeal spasms preventing swallowing saliva loaded with virions).
• Abnormal vocalization: Progressive paresis of the recurrent laryngeal nerves and vocal cords causes a characteristic altered bark or dropping, high-pitched howl.
• Pharyngeal paralysis (Paralytic / Dumb Stage): Bilateral masseter and pharyngeal flaccid paralysis ("dropped jaw"), inability to swallow water (hydrophobia manifestation), ascending paralysis of limbs, coma, and respiratory failure.
  • Conclusion: The correct chronological sequence is (B) $\to$ (A) $\to$ (D) $\to$ (C) (Option 4).

• Mechanism of Chronic Anemia in Nagana: In African animal trypanosomiasis (nagana, caused by Trypanosoma congolense, T. vivax, T. brucei), chronic-stage anemia is primarily maintained by inadequate bone-marrow response (dyserythropoiesis).
• Cytokine Suppression: Prolonged high levels of inflammatory cytokines (TNF-$\alpha$, IFN-$\gamma$) suppress erythropoietin signaling in the bone marrow, disrupt iron recycling, and inhibit erythroid progenitor differentiation.

Correct option: (3) Inadequate bone-marrow response

• Epidemiology of Fasciolosis: The transmission risk and seasonal intensity of hepatic fasciolosis (Fasciola hepatica, F. gigantica) in grazing ruminants are determined fundamentally by the number and population density of infected intermediate host snails (Lymnaea spp.).
• Pasture Contamination: Higher snail infection rates directly dictate the magnitude of cercarial shedding and subsequent metacercarial encystment on pasture vegetation.

Correct option: (2) Number of infected snails