(a)(i) Describe the effect of Avian Influenza Virus on Poultry industry and suggest the control measures to be adopted for…

(a)(i) Avian Influenza and the Poultry Industry

Avian influenza viruses (influenza A, family Orthomyxoviridae) are classed as highly pathogenic (HPAI, mainly H5 and H7 subtypes) or low pathogenic (LPAI). HPAI H5N1 (clade 2.3.4.4b is now dominant worldwide) causes a peracute systemic disease in chickens and turkeys with sudden deaths, cyanosis of comb and wattles, facial oedema, haemorrhages on the shanks and in the proventriculus, and mortality approaching 100%. H9N2, which is endemic in Indian poultry, is an LPAI virus: it causes mild respiratory disease and drops in egg production, but it worsens secondary bacterial infections and has donated internal genes to other zoonotic strains.

Effects on the poultry industry: direct losses from mortality and drop in egg and meat production; mass culling of birds, eggs and feed in infected zones; restrictions on the movement and sale of birds and bans on exports of poultry products; a sharp fall in consumer demand and prices during outbreaks (even in unaffected areas); losses to hatcheries, feed mills and traders; and the hardest hit are backyard and small commercial farmers, many of them women. India has recorded repeated H5N1 outbreaks since 2006 in states including Maharashtra, West Bengal, Kerala, Odisha, Jharkhand and Andhra Pradesh.

Control measures (India's Action Plan for Prevention, Control and Containment of Avian Influenza, revised 2021):

1. Early warning: active and passive surveillance, prompt reporting of unusual mortality, and confirmation at ICAR-NIHSAD, Bhopal; AI is a notifiable disease reported to WOAH.
2. Stamping out: culling of all poultry within 1 km of the epicentre (infected zone), safe disposal of carcasses, eggs, feed and litter by deep burial or incineration, cleaning and disinfection, and compensation to farmers.
3. Zoning: movement control and intensive surveillance within a 10 km surveillance zone, closure of bird markets, and post-operation surveillance before the area is declared free.
4. Biosecurity: all-in all-out rearing, bird-proof houses to exclude wild waterfowl, separating ducks from chickens, restricted entry, footbaths and disinfection of vehicles.
5. Vaccination against HPAI is not practised in India, because the country follows a stamping-out policy for trade and disease-freedom purposes.
6. Human protection: PPE and antiviral (oseltamivir) prophylaxis for culling teams, and health surveillance of contacts under a One Health approach.

WHO guidance for a pandemic situation: under the International Health Regulations (2005) countries must notify WHO within 24 hours of assessment of any human infection with a new influenza subtype, and WHO can declare a public health emergency of international concern. The Global Influenza Surveillance and Response System (GISRS) monitors viruses and selects candidate vaccine viruses. The Pandemic Influenza Preparedness (PIP) Framework (2011) links sharing of H5N1 and other potentially pandemic viruses with access to vaccines and antivirals. WHO's Pandemic Influenza Risk Management guidance asks countries to prepare national plans covering surveillance, antivirals, vaccines, non-pharmaceutical measures (isolation, hygiene, social distancing) and risk communication. The WHO Pandemic Agreement, adopted by the World Health Assembly in May 2025, adds commitments on prevention, One Health, equitable access to countermeasures and a pathogen access and benefit-sharing system.

(a)(ii) Acetonaemia (Ketosis) in Buffalo

Acetonaemia is a metabolic disorder of high-yielding buffaloes, usually in the first 2–6 weeks after calving, when energy intake cannot meet the demand of rising milk yield (negative energy balance). Body fat is mobilised as non-esterified fatty acids, which the liver cannot fully oxidise, so ketone bodies (β-hydroxybutyrate, acetoacetate, acetone) accumulate and fatty liver develops.

Contributing factors: high milk yield and early lactation; over-conditioned (fat) animals at calving; underfeeding or sudden change of diet; poor-quality or butyric silage; reduced appetite from other periparturient diseases (retained placenta, metritis, milk fever, mastitis); cobalt and phosphorus deficiency in some areas; and lack of exercise in stall-fed animals.

Clinical findings: two forms are seen. In the wasting (digestive) form there is gradual fall in milk yield and appetite (concentrates refused before roughage), loss of body weight, firm dry faeces and reduced rumen motility. The nervous form shows licking, chewing movements, salivation, head pressing, apparent blindness, circling, incoordination and aggression. A sweet acetone smell may be detected in breath and milk.

Diagnosis: history and signs; Rothera's (nitroprusside) test on milk or urine; blood β-hydroxybutyrate (above about 1.2 mmol/L indicates subclinical ketosis, above about 3 mmol/L clinical ketosis) and low blood glucose; cow-side BHB meters.

Differential diagnosis: traumatic reticuloperitonitis, simple indigestion, milk fever and hypomagnesaemia, fatty liver, and for the nervous form rabies, lead poisoning, listeriosis and polioencephalomalacia.

Line of treatment: 500 ml of 25–50% dextrose intravenously; oral propylene glycol (about 300 ml twice daily for 3–5 days), which is converted to glucose; a glucocorticoid such as dexamethasone (except in pregnant animals near term) to promote gluconeogenesis; vitamin B12 with cobalt and niacin as supportive therapy; treatment of any concurrent disease. Prevention is by correct body condition at calving and gradual increase of energy-dense feed after calving.

(b) Stay Apparatus and Bow-String Mechanism in Horse

The stay apparatus is a set of ligaments and tendinous muscles that lock the limb joints so that the horse can stand, and even doze, with very little muscular effort.

In the forelimb: the shoulder is stabilised by the biceps brachii, whose tendinous strand (lacertus fibrosus) joins the extensor carpi radialis; this prevents flexion of the shoulder and keeps the carpus extended. The carpus, fetlock and pastern are supported by the superficial digital flexor tendon with its proximal (radial) check ligament, the deep digital flexor tendon with its distal (carpal) check ligament, and the suspensory apparatus (suspensory ligament, proximal sesamoid bones and distal sesamoidean ligaments), which prevents over-extension of the fetlock.

In the hindlimb: the stifle is locked by the patellar locking mechanism, in which the medial patellar ligament and the parapatellar fibrocartilage hook over the enlarged medial ridge of the femoral trochlea. Through the reciprocal apparatus (peroneus tertius cranially and superficial digital flexor caudally), fixing the stifle also fixes the hock. The distal joints are then supported as in the forelimb. The horse rests one hindlimb at a time and shifts weight between them. Failure of the patella to unlock is called upward fixation of the patella.

The bow-and-string mechanism (Slijper) explains how the trunk supports the heavy abdominal viscera. The "bow" is the thoracolumbar vertebral column with its ligaments and the epaxial muscles, which tend to straighten (extend) it. The "string" is the ventral trunk: the sternum, the rectus abdominis and other abdominal muscles and the linea alba, which tend to flex the bow. The weight of the viscera and the forward and backward thrust of the limbs act on this system. The balance of tension between bow and string keeps the back rigid and slightly arched, carries the weight of the abdomen, and transmits the propulsive force of the hindlimbs to the trunk during locomotion.

(c) Diseases of the Nervous System: Clinical Manifestations and Neurological Examination

Clinical manifestations depend on the site of the lesion:

1. Altered mental status and behaviour: depression, stupor or coma, excitement, aggression, head pressing, compulsive walking (e.g. rabies, polioencephalomalacia, lead poisoning, hepatic encephalopathy).
2. Seizures and involuntary movements: convulsions, tremors, tetany, opisthotonus (e.g. hypomagnesaemia, tetanus, canine distemper).
3. Abnormal posture and head position: head tilt, circling, star-gazing (e.g. listeriosis with unilateral facial paralysis, vestibular disease).
4. Cranial nerve deficits: blindness, anisocoria, facial paralysis, dysphagia, tongue paralysis.
5. Gait abnormalities: ataxia, dysmetria, weakness (paresis) or paralysis, knuckling (e.g. spinal cord compression, intervertebral disc disease in dogs).
6. Changes in reflexes and sensation: upper motor neuron signs (increased tone and reflexes) or lower motor neuron signs (flaccidity, reduced reflexes, muscle atrophy), and loss of pain sensation.
7. Autonomic signs: urinary retention or incontinence, loss of anal tone.

Methods of neurological examination:

1. History (onset, progression, number of animals affected, feed, vaccination, exposure to toxins or bites).
2. Observation from a distance: mental status, behaviour, posture, head carriage and gait (walking, turning, backing, walking on a slope, blindfolding).
3. Cranial nerve examination: menace response, pupillary light reflex, palpebral and corneal reflexes, facial sensation, eye position and nystagmus, tongue tone, swallowing (gag reflex).
4. Postural reactions: proprioceptive positioning (knuckling), hopping, wheelbarrowing, hemi-walking and placing reactions (mainly in small animals); sway test and tail pull in large animals.
5. Spinal reflexes and muscle tone: patellar, withdrawal (flexor), perineal and panniculus reflexes, muscle tone and atrophy.
6. Sensory evaluation: superficial and deep pain perception, and palpation for spinal pain.
7. Lesion localisation from these findings (forebrain, brainstem, cerebellum, spinal cord segment or peripheral nerve).
8. Ancillary tests: cerebrospinal fluid collection (cisternal or lumbosacral) for cells, protein and culture; haematology and biochemistry (glucose, calcium, magnesium, lead); radiography and myelography; CT and MRI; electroencephalography and electromyography; and post-mortem examination including brain sampling for rabies.