(a) What are the main epidemiological principles of animal disease control? (20 marks) (b) Discuss the sanitation requirements of…

(a) Main epidemiological principles of animal disease control

Disease control rests on breaking the chain of infection: source, transmission route and susceptible host, guided by the agent–host–environment triad.

1. Diagnosis and surveillance: early, accurate diagnosis, passive reporting by field veterinarians and active serosurveillance, with mapping and forecasting at ICAR-NIVEDI through the NADRES system.
2. Control of the source: isolation and treatment of cases, slaughter or culling (test and cull) of infected animals where feasible, and safe disposal of carcasses, aborted foetuses and litter.
3. Interrupting transmission: quarantine, movement control, disinfection, vector control and biosecurity.
4. Raising host resistance: vaccination, which lowers the reproduction number R₀. Disease dies out when immunity in the population exceeds the herd-immunity threshold (1 − 1/R₀), for example under the National Animal Disease Control Programme for foot-and-mouth disease and brucellosis (Brucella S19 in female calves of 4–8 months) and the PPR eradication programme.
5. Zoning and compartmentalisation: disease-free zones or compartments under WOAH standards, to protect trade.
6. Eradication and monitoring: stepwise progression from control to eradication, with evaluation, and a One Health approach for zoonoses.

Where test-and-slaughter is not practicable, as in India, segregation with vaccination is used.

(b) Sanitation requirements of clean and safe milk production

• Healthy animals: animals are tested and free of mastitis, tuberculosis and brucellosis, clean, and groomed; the shed is well-ventilated with dry, clean floors and bedding and a drainage system.
• Udder preparation: washing the udder with clean water and drying with a single-use towel, fore-stripping to detect mastitis, and pre- and post-milking teat dipping.
• Milker: clean clothes, washed hands, trimmed nails, and absence of infection.
• Equipment: stainless steel or food-grade utensils, washed with a cold rinse, detergent wash, hot rinse and sanitiser, dried inverted; cleaning-in-place for milking machines and pipelines, with a narrow-mouthed pail, to reduce contamination.
• Post-milking: milk is filtered and chilled to 4°C within two hours, in a bulk milk cooler, and transported in a clean, cold vehicle.
• Environment: clean water, fly and pest control, and manure disposal.
• Standards: compliance with FSSAI and BIS standards, with microbial (plate count, coliform) and somatic cell count checks.

(c) By-products of the Indian dairy industry and broad principles of their utilization

By-products:

• Skim milk from cream separation and butter making.
• Whey from chhana, paneer and cheese making.
• Buttermilk from churning butter and curd.
• Ghee residue from ghee making.
• Lactose and casein, recovered from whey and skim milk.

Principles of utilization:

• Use them for human food wherever possible, since they keep full nutritive value; skim milk is made into powder, toned and double-toned milk, and cheese, and whey into beverages, whey powder and whey protein concentrates.
• Fractionation and recovery of valuable components, by membrane processes (ultrafiltration), into protein concentrates, lactose and casein.
• Fermentation of lactose-rich whey into lactic acid, alcohol and probiotics.
• Conversion into animal feed, such as calf feed and poultry rations, where human use is not possible.
• Drying and concentration to make stable products, and preventing pollution, since whey has a very high BOD.
• Ghee residue goes to sweets, bakery and confectionery.