(a)(i) Discuss about emerging zoonotic diseases, their prevalence and effects on animal and human population. (10 marks) (a)(ii)…

(a)(i) Emerging Zoonotic Diseases: Prevalence and Effects

Emerging zoonoses are infections transmitted between vertebrate animals and humans that are newly recognised, or that are already known but are rising in incidence or spreading to new areas or hosts. About 60% of emerging infectious diseases of humans are zoonotic, and most of these originate in wildlife. Drivers include deforestation and land-use change, expansion of livestock and poultry farming, wildlife trade and bushmeat, climate change extending vector ranges, urbanisation, and global travel and trade.

Important examples and their prevalence in India:

1. Nipah virus (fruit bats, Pteropus): repeated outbreaks in Kerala since 2018 after the 2001 and 2007 outbreaks in West Bengal; case fatality often 40–75%.
2. Highly pathogenic avian influenza H5N1: recurrent poultry outbreaks since 2006, with sporadic human cases.
3. Kyasanur Forest Disease (ticks, monkeys): endemic in the Western Ghats of Karnataka, now also reported from Kerala, Goa and Maharashtra.
4. Crimean-Congo haemorrhagic fever (Hyalomma ticks, livestock): outbreaks in Gujarat and Rajasthan since 2011.
5. Scrub typhus, leptospirosis, Japanese encephalitis and brucellosis: widespread and increasingly recognised.
6. COVID-19 (SARS-CoV-2) showed the pandemic potential of a spillover from animals.

Rabies remains the most important endemic zoonosis, with India accounting for a large share of global human deaths.

Effects on animals: deaths and illness, drop in milk, meat and egg production, abortion and infertility (brucellosis), mass culling and compensation costs (avian influenza), movement and trade restrictions, and threats to wildlife and conservation.

Effects on humans: illness and death, often with high fatality and no specific treatment (Nipah, CCHF), hospital-acquired spread, loss of livelihoods for farmers, a burden on health systems, food insecurity, and wider economic and social disruption in epidemics and pandemics.

(a)(ii) Methods of Disease Transmission and Control Measures

Direct transmission: physical contact (rabies through bites, brucellosis at parturition), droplet spread over short distances, and vertical transmission from mother to offspring through the placenta, colostrum or egg (e.g. Salmonella Pullorum in eggs).

Indirect transmission: vehicles such as contaminated food, milk, water and fomites (salmonellosis, leptospirosis via urine-contaminated water); airborne droplet nuclei and dust (Q fever); and biological vectors such as mosquitoes (Culex for Japanese encephalitis and West Nile fever), ticks (Hyalomma for CCHF, Haemaphysalis for KFD), sandflies and fleas; mechanical vectors (flies) carry agents on their body.

Control measures are matched to the route:

1. At the source: early detection and reporting, isolation and treatment, test and segregation or slaughter (brucellosis, tuberculosis), stamping out with compensation (HPAI), and control of reservoirs (dog population management for rabies).
2. Breaking transmission: biosecurity (restricted entry, disinfection, all-in all-out), quarantine of new or imported animals, movement control and zoning, safe disposal of carcasses, pasteurisation of milk and meat inspection, safe water, and vector control (acaricides, insecticides, draining breeding sites).
3. Protecting susceptible hosts: vaccination of animals (e.g. brucellosis and FMD under the National Animal Disease Control Programme, anti-rabies vaccination of dogs), pre- and post-exposure prophylaxis in humans, personal protective equipment for high-risk workers, and health education.
4. Surveillance and coordination: the National Animal Disease Reporting System (NADRS) for animal disease and the Integrated Health Information Platform for human cases, laboratory networks, WOAH reporting, and a One Health approach linking veterinary, human health and wildlife departments.

(b) Defects in Condensed and Evaporated Milk

Evaporated milk (unsweetened, sterilised in the can) and sweetened condensed milk (preserved by about 62–63% sugar in the water phase) have partly different defects.

Evaporated milk:

1. Coagulation during sterilisation (heat instability): caused by high acidity, a poor salt balance (calcium/magnesium vs phosphate/citrate) or insufficient forewarming. Prevented by using fresh milk of low acidity, forewarming (e.g. 95–100°C for 10–20 minutes), and adding stabiliser salts (disodium phosphate or sodium citrate) according to a pilot sterilisation test.
2. Age gelation and thickening during storage: related to storage time and temperature and to the heat treatment given. Prevented by correct forewarming and sterilisation and by storing cans in a cool place.
3. Fat separation (cream rising): insufficient homogenisation or long storage. Prevented by two-stage homogenisation at correct pressure and periodic inversion of stored cans.
4. Browning (Maillard reaction) and cooked flavour: excessive heat during sterilisation or high storage temperature. Prevented by controlling time–temperature and cool storage.
5. Bacterial spoilage: underprocessing or leaky seams allow spore-formers to survive or enter, causing flat-sour spoilage (Geobacillus stearothermophilus, formerly Bacillus stearothermophilus), coagulation (Bacillus coagulans) or blown cans (thermophilic clostridia). Prevented by adequate retort sterilisation (e.g. 115–118°C for 15–20 minutes) and good can seaming.
6. Metallic taste and can corrosion: prevented by lacquered cans and proper seaming.

Sweetened condensed milk:

1. Sandiness or grittiness: lactose crystals larger than about 10 micrometres because cooling and seeding were inadequate. Prevented by rapid cooling with vigorous stirring and seeding with fine lactose powder.
2. Thickening (age thickening): from high forewarming temperatures, high acidity or high storage temperature. Prevented by controlled forewarming (around 80–85°C) and cool storage.
3. Sugar sediment and lactose settling: prevented by correct sugar ratio and viscosity and by controlled crystallisation.
4. Buttons: brown, cheesy mould colonies (e.g. Aspergillus repens) on the surface where air is trapped in the can. Prevented by filling cans completely, vacuum sealing and hygiene.
5. Gas formation (blowing): sucrose-fermenting yeasts such as Torula. Prevented by adequate sugar concentration, pasteurisation of sugar syrup and hygienic filling.
6. Browning and rancidity (lipase activity if not inactivated): prevented by proper heat treatment and cool storage.

(c) Ante-Mortem Inspection

Ante-mortem inspection is the examination of live animals by a veterinarian before slaughter. In India it is required under the Food Safety and Standards (Licensing and Registration of Food Businesses) Regulations, 2011 and the Prevention of Cruelty to Animals (Slaughter House) Rules, 2001, which also require animals to be rested, and forbid slaughter of pregnant animals and animals below a certain age.

Purposes: to identify animals with notifiable or zoonotic diseases (e.g. anthrax, rabies, tuberculosis) and prevent them entering the food chain; to separate sick or suspect animals so that post-mortem inspection can be focused; to detect animals carrying drug residues within withdrawal periods; to prevent contamination of the abattoir and spread to workers; and to protect animal welfare by detecting fatigue, injury and cruelty in transport.

Procedure: animals are rested (usually 12–24 hours) with water; identification and transport documents are checked; each animal is observed at rest and in motion for behaviour, posture, gait, body condition, respiration, discharges, swellings, skin lesions and diarrhoea; suspect animals are separated and examined clinically, including rectal temperature, pulse, respiration, lymph nodes and mucous membranes; inspection is done in daylight or good light, and repeated if slaughter is delayed beyond 24 hours.

Categorisation based on ante-mortem findings:

1. Passed for normal slaughter: healthy animals.
2. Passed for slaughter under special precautions (suspect): animals with localised conditions (e.g. localised abscess, minor injury) are slaughtered separately, often at the end of the day, with detailed post-mortem inspection.
3. Detained (held for re-examination): fatigued or excited animals, animals with doubtful signs, or animals within a drug withdrawal period are held and re-examined.
4. Condemned (not to be slaughtered for food): animals with generalised or dangerous conditions such as rabies, tetanus, anthrax, septicaemia, high fever or moribund state; they are killed and disposed of without slaughter for food. Anthrax-suspect animals must not be opened; they are disposed of by incineration or deep burial with lime.
5. Emergency slaughter: animals that are otherwise healthy but have acute injury (e.g. fracture) are slaughtered at once in the emergency slaughter area under veterinary supervision, and the carcass is inspected in detail before release.