eChapters

Introduction

Hepatocytes are tiny cells that constitute the primary structural unit of the liver. Periportal hepatocytes, the first to receive blood from the portal system, are particularly vulnerable to hepatotoxins and endotoxins. Periacinar hepatocytes, placed further away from the portal blood supply, are more susceptible to hypoxia, toxic metabolites and hypoperfusion. Inflammatory cells are drawn to injured hepatocytes and biliary epithelium due to the release of cytokines and inflammatory mediators. This causes additional hepatocyte necrosis and fibrosis. The liver has exceptional regenerative abilities as hepatocytes can be replaced even if only 12% remains intact.

Hepatocytes exhibit colour changes when they are laden with fat or pigments. In their f irst week of life, young turkeys and chickens typically have a lot of fat and pigments (carotenoids) deposited in the liver due to the ability of intestines in mobilizing the yolk content. It is typical to find fat vacuoles (microscopic fat deposits) within the hepatocytes at this point. A bird's liver will typically turn mahogany-brown after about seven days of life. Because of the influence of oestrogens, the hormones that are present in large concentrations once maturity is attained, the quantity of fat in the liver of adult hens increases before the age of lay. Because a large amount of fat and pigments are transferred from the liver to the oviduct for yolk formation in eggs, the majority of laying hens in a flock will typically have a pale brown or yellowish liver. When liver seems pale or yellow, histopathology is a crucial technique that can be used to establish a differential diagnosis.

Introduction

Musculoskeletal diseases in poultry are often exhibited as lameness or leg weakness. Numerous factors, including those related to diet, animal husbandry, infections, or heredity, might contribute to musculoskeletal problems. Lameness can be exhibited due to disorders in the central or peripheral neurological systems, reproductive system, trauma or infection in the foot, leg, hip, spine, or just a generalised sickness. Less frequently, musculoskeletal anomalies can affect the bird’s beak, neck, or wings. The diseases can also be classified as infectious origin (bacterial, viral) or non-infectious origin (congenital deformities, nutritional, trauma or neoplasia). Modern poultry production lines put a lot of strain on the musculoskeletal system due to factors like growth rate in broiler chickens and egg output in laying hens. As a result, poor nutrition and husbandry practices frequently lead to musculoskeletal disorders. Thus, musculoskeletal disorders in poultry can be controlled by choosing proper genetic selection, efficient vaccinations, adequate nutrition and proper husbandry practices.

Introdcution

Poultry have a nervous system made up of the brain, spinal cord, sympathetic nerves that govern their viscera, and branches that go to their ears and eyes. The structure of the brain and spinal cord is very similar to that of mammals. However, there are also significant structural variations between many bird brains and many human brains, including the following:

1. Absence of cortex: According to Cobb (1960), the cortex is “a peripherally placed coating (pallium) of cells arranged in layers,” yet it is completely absent in birds. However, other authors have compared the hyperstriatum to the mammalian cortex (Haefelfinger, 1957; Stingelin, 1958).

2. Presence of hyperstriatum: The functions of the hyperstriatum are comparable to those of the mammalian cortex. In pigeons and chickens, the hyperstriatum may be involved in the visual and hearing systems’ functions.

3. Birds have highly developed optic lobes.

4. Turkeys and vultures are the only birds with a well-developed olfactory system.

Introduction

The reproductive system is fundamental to poultry production, playing a crucial role in both the quantity and quality of eggs laid. Its importance goes beyond mere biology, impacting the profitability and long-term sustainability of poultry operations (Abbasi et al., 2024). Central to this is the egg, the ultimate product of avian reproduction. The reproductive system coordinates complex processes to ensure eggs meet high standards. Any disruption to this delicate balance can have far-reaching effects on the economic and environmental aspects of poultry farming. Disorders affecting the avian reproductive system pose significant challenges to the poultry industry. Whether they are minor disturbances or major disruptions, these disorders can undermine the foundation of successful production. They can lead to reduced egg production and compromised egg quality, affecting productivity, efficiency, and ultimately, profitability. In today’s poultry management landscape, where efficiency is paramount, the impact of reproductive disorders cannot be overstated. Beyond economic concerns, these disorders also affect sustainability and environmental responsibility. A healthy reproductive system is not only crucial for financial success but also for upholding ethical and responsible poultry practices. As such, ensuring the reproductive health of poultry is of utmost importance. It requires dedicated effort, attention to detail, and a comprehensive approach. By strengthening the reproductive system against various threats, poultry producers can secure not only the current success of their operations but also a legacy of responsible stewardship for future generations (Habibi et al., 2024).

Introduction

Ante mortem diagnosis of cardio vascular diseases in avian patients is a challenging to the physician. Compare with the mammals, few anatomical and physiological features are unique in birds. The avian heart is anatomically similar to mammals, although birds have a proportionally larger heart size relative to a comparably sized mammal. Heart size in mammals remains equivalent to body mass, while larger birds have a proportionally smaller hearts in relation to body size than smaller birds. The apex of the heart is enclosed between the right and left hepatic lobes and lies along the sternum and parallel to the thoracic spine in the cranio ventral coelom. The avian cardiovascular system is adapted to the high aerobic requirements for flight, running or swimming. Efficient oxygen transfer to the tissues is facilitated by a lower total peripheral resistance, higher heart rate, higher arterial blood pressure and more rapid myocardial depolarization. The clinical signs seen in birds afflicted with cardiac disease can be vague and non-specific which are mimicking many other disease conditions. Similar to mammals, birds may present with lethargy, weakness, exercise intolerance, syncope, dyspnoea, coughing and even sudden death. On physical examination cardiac disease may be suspected based on the presence of arrhythmia, murmur, muffled cardiac sounds, poor peripheral pulses, cyanosis and coelomic distension. Pulmonary oedema, hepatomegaly, ascites and enlarged jugular veins with pulsation may be seen in cases of congestive cardiac failure. Pericarditis can occur with primary infectious agents or secondary to disease occurring in adjacent tissues, such as mycotic pulmonary granulomas. Visceral gout due to hyperuricaemia may also affect the pericardium. Congestive heart failure and systemic manifestations of disease, such as hypoproteinaemia, may result in effusions within the pericardium. Myocardial ventricular hypertrophy can occur with any condition that results in an elevated preload on the heart, including pulmonary hypertension and atherosclerosis. Myocarditis has been observed in cases of chlamydiosis, polyomavirus infection and proventricular dilatation disease from bornavirus. Heavy metal toxicosis has been associated with cardiac neural dysfunction and myocardial infarction. Vegetative endocarditis and resultant valvular insufficiency can occur with bacteraemia from chronic bacterial infections involving other organ systems.

Introduction

The digestive system of the birds has modifications to facilitate the easy flight. Length of intestine in birds is relatively shorter compared to mammals. Also, they lack teeth and jaw muscles which are replaced with light weight beak. Food grains are swallowed as whole and ground in the gizzard with the help of powerful muscles. In the mouth, tongue is used to manipulate the food and also aids in swallowing the food. Chickens have as many as 300 taste buds. The elementary system in birds consists of gastro intestinal tract and the accessory glands, the course of the elementary starts with Mouth, oesophagus, crop, proventriculus (glandular/true stomach), gizzard (mascular stomach), small intestine (duodenum, Jejenum, ileum), large intestine (colon and caeca) which lastly opens into cloaca. For fast growing poultry species elementary system is very important. It plays vital role in digestion, absorption and also provides protective immunity. Poultry intestines harbours diversified microflora which aids in enhanced availability of nutrients to the bird. Intestinal wall contains four layers: mucosal, submucosal, muscle tunic, and the serosal layer. As intestine is involved in important functions like digestion & immunity, any change in intestinal integrity / microflora balance impacts the bird performance in terms of body weight gain in broilers and egg number in layers. Some bacteria, viruses and also fungi produce different diseases / conditions in poultry birds. The ban on the use of antimicrobial growth promoters has pushed poultry producers from use of AGP’s to alternatives to AGP’s such as prebiotics, probiotics, essential oils and some herbals. Maintaining good gut health in the absence of AGP’s and anticoccidial drugs is a challenging situation for the poultry farmers across the globe. Poultry gut contains diverse community of bacteria, fungi, protozoa and viruses. The recent data suggests that gastrointestinal tract of a broiler chicken colonizes by an estimated 600 – 800 species of bacteria. The abundance and diversity of microbiota varies along the GI tract. After the hatch GI tract colonizes within 3-4 days. Small intestine of broilers mainly contains lactobacilli although enterococci, E.coli, eubacteria, clostridia, propionibacteria and fusobacteria can be found.

The skin of the birds provides a physical barrier between the birds its environment, protecting the birds from bacteria and physical injury. The health of the bird can be compromised, and the value of the end-product can dramatically decrease. Bird’s skin differs from that of mammals by its thinness, by the presence of feathers instead of hair, and by the absence of sebaceous glands (sweat glands), although the overall histological structure is similar. Bird’s skin is composed of an epidermis separated from a dermis by a basal membranes to protect the body from infection. The integumentary system consists of the skin, the feathers and the appendages (claws and beak). The skin covers the majority of the body and contains glands in the outer ear canal and the preen gland at the base of the tail, that the bird uses to preen its feathers. The integumentary system is very important in providing protection to the bird from a number of potentially dangerous situations. The functions provided by the integumentary system include: A barrier between the external environment and the internal systems and organs thus provides support and protection from infection by microorganisms and from physical injury. Excellent thermal insulation to help regulate body temperature in a variable environment. Numerous nerve endings for the senses to enable the bird to be aware of potentially harmful situations. Pigments for display and protection from the elements. The compounds capable of conversion into vitamin D when exposed to sunlight. Avian skin is relatively thin with the epidermis consisting of only 2-10 cell layers. There are no sweat glands; instead heat is lost via the respiratory tract and by radiation from featherless areas. The brood patch is a featherless area that can occur in both sexes and is either seasonal or permanent depending on species.

Introduction

Knowledge of the avian respiratory system is essential for developing a health monitoring plan for a poultry flock, recognizing problems that may occur, and taking action to correct them. The avian respiratory system begins with nostril includes trachea, bronchi (bronchus) and ends with lungs and air sacs. Respiratory diseases are the most common cause of death in a poultry flock.

The avian respiratory system is involved in the following functions:

• Absorption of oxygen (O2)

• Release of carbon dioxide (CO2)

• Release of heat (temperature regulation)

• Detoxification of certain chemicals

• Rapid adjustments of acid/base balance

• Vocalization

Introduction The urinary system of poultry, consisting of the kidneys, ureters, and cloaca, is essential for removing waste products and maintaining fluid balance. However, this system can be susceptible to various disorders that can impact the health and productivity of the flock. This chapter will discuss some of the most common urinary system disorders in poultry.

Urinary system disorders can have significant negative impacts on poultry health and productivity (Klybeck, n.d; Mississippi State University Extension, n.d; Poultry Hub, n. d.). Some of the key ways these disorders affect poultry include:

1. Gout: Renal diseases often lead to gout in poultry, which is a metabolic disorder resulting in hyperuricemia and deposition of uric acid or urates in tissues (Klybeck, n.d.). This can further damage the kidneys or other body systems.

2. Reduced productivity: Gout has a direct effect on productivity by lowering weight gain, increasing feed conversion ratio (FCR), and causing mortality which may reach 11-30% (Klybeck, n.d)

3. Organ damage: Accumulation of uric acid can lead to swelling and damage of kidney cells, as well as visceral gout where whitish deposits are found on the surface of organs like the heart, liver, intestines, and lungs (Klybeck, n.d; Mississippi State University Extension, n.d.).

4. Mortality: Severe kidney damage and dysfunction can quickly lead to debilitation and death in poultry (Poultry Hub, n.d.). Acute septicemic coliform infections may also cause sudden death (Mississippi State University Extension, n.d.)

5. Respiratory issues: Infectious bronchitis virus can affect both the respiratory and urinary systems, causing inflammation and damage to the kidneys (Mississippi State University Extension, n.d.).

Poultry, encompassing a wide range of domesticated birds, plays a crucial role in agriculture, providing meat and eggs to populations worldwide. The health and well-being of poultry are of paramount importance for sustainable and efficient production. One aspect that significantly influences poultry health is the condition of their wings. Wings serve various purposes for birds, including flight, balance, and protection. Disorders affecting poultry wings can arise from a multitude of factors, ranging from nutritional imbalances to infectious agents and environmental stressors.

Understanding and addressing poultry wing disorders require a comprehensive approach that encompasses both preventive measures and therapeutic interventions. This comprehensive understanding involves recognizing the various disorders that can afflict poultry wings, their causes, symptoms, and potential treatments. In this exploration, we delve into 50 multiple-choice questions and answers covering a diverse array of poultry wing disorders, providing insights into the complexity of avian health management.

The Significance of Poultry Wing Health

Maintaining the health of poultry wings is not merely a matter of ensuring their ability to f ly; it is intrinsically linked to the overall well-being of the bird. Poultry wings are vital for performing a myriad of daily activities, including foraging, preening, and maintaining social hierarchies within flocks. Additionally, the condition of the wings often reflects the bird’s general health status, making them an essential diagnostic indicator for avian health professionals.

Calcification

Calcification is the deposition of calcium phosphates and calcium carbonates in soft tissues other than bones and teeth. It may be classified as dystrophic and metastatic calcification.

Dystrophic Calcification

Dystrophic calcification is characterized by the deposits of calcium salts in necrosed tissue of any organ (Fig 8.1).

Etiology /Occurrence

• Necrosis.

• Parasitic infections.

• Tuberculous lesions.

Cloudy Swelling

Swelling of cells occur with hazy appearance due to a mild injury. The cells take more water due to defect in sodium pump leading to swollen mitochondria which gives granular cytoplasmic appearance. It is the first reaction of cell to the mildest injury. Cloudy swelling is a reversible reaction (Figs. 4.1 & 4. 2).

Etiology

• Can be caused by even mildest injury.

• Any factor causing interference with metabolism of the cell like bacterial toxins, fever, diabetes, circulatory disturbances etc.

Macroscopic features

• Organ becomes enlarged and rounded.

• Weight of organ increases.

• Bulging on cut surfaces.

• Amount of fluid increases in organ.

Microscopic features

• Swelling of cells, edges become rounded.

• Increased size of cells.

• Cytoplasm of the cells becomes hazy/cloudy due to increased granularity.

• Can be seen in liver, kidney and muscles.

Congestion/ Hyperemia

Hyperemia is increased amount of blood in circulatory system. It is of two types, active and passive. In active hyperemia blood accumulates in arteries while in passive hyperemia the amount of blood increases in veins (Figs. 3.1. to 3.4).

Etiology

• As a result of inflammation.

• Obstruction of blood vessels.

Macroscopic features

• Organ becomes dark red/cyanotic.

• Size of organ increases.

Aplasia/Agenesis

Aplasia or agenesis is absence of any organ (Fig. 9.1).

Hypoplasia

Hypoplasia is failure of an organ/tissue to attain its full size (Fig. 9.1).

Etiology

• Congenital anomalies e.g. hypoplasia of kidneys in calves.

• Inadequate innervation.

• Inadequate blood supply.

• Malnutrition.

• Infections e.g. cerebral hypoplasia in bovine viral diarrhoea.

A laboratory is essential for research work in science and development. Most of the research institutes have dedicated laboratories for researchers and students to conduct experiments, perform research work, as well as to provide hands-on learning/training to students. There are certain rules and regulations laid down by the laboratory in-charge which need to be followed strictly for safety purposes. Some of the laboratories keep ‘safety manual’ for researchers to read before entering into the laboratory to conduct experiments. Whenever safety is compromised in a laboratory, there is increase in risk of unwanted incidents in the laboratory. Storing food/beverages in the same refrigerator where laboratory chemicals are kept may lead to disastrous effects on health. This chapter aims to provide instructions in brief on the things to be performed (Do’s) before and after entering onto a laboratory as well as the things never to be done (Don’ts) in a laboratory for the safety reasons.

Good Laboratory Practices (Do’s)

• P Wear apron/labcoat while working in the laboratory.
• P Use gloves/respiratory mask/fumehood while handling toxic/volatile/inflammable chemicals/reagents.
• P Use pippet or pippetor for safety in transfer of solutions.
• P Protect eyes, face and naked parts of the body from UV radiations. Use safety goggles or face mask/apron.
• P Keep your eyes away from Liquid Nitrogen and use cryogloves while handling it.
• P Arrange all the necessary materials/solutions before starting the experiment.
• P Periodically fumigate/ozonize culture and inoculation rooms.
• P Autoclave all contaminated materials before discarding.
• P Pre-treat gel or solution containing Ethidium Bromide (EtBr) before discarding into laboratory waste-disposal bin, and use gloves while handling them.
• P Burn all the transgenic plant materials in an incinerator after taking necessary observations.
• P Make entry in the designated log-book and clean the instrument after using it properly.
• P Switch-off the instrument after use or when not in use.
• P Wash hands with soap and remove the labcoat before leaving/going out of the laboratory7.
• P Ensure that switches for fans/lights, and water taps are off while leaving the laboratory.
• P Follow the biosafety guidelines suggested for handling and disposal of the hazardous chemical.

Doppler ultrasound is a non-invasive diagnostic tool being employed in evaluating blood flow in major vessels, veins and arteries. Information regarding perfusion in an organ or an area can also be obtained through Doppler ultrasonography. Doppler ultrasound is an important part of echocardiographic examination in dogs and cats. Its more recent application is in the investigation of the tissue wall motion while evaluating the heart. B-mode ultrasound is used to examine cardiac structures.

Key Points

• Drowning is a common cause of accidental death in animals.

• Submersion in water or other fluids prevents atmospheric air from reaching the lungs.

• To diagnose drowning, trustworthy witnesses and a history of drowning at the accident location are required.

Introduction

Drowning or immersion is a type of asphyxial death caused by a body being submerged in water or another fluid medium and preventing atmospheric air from reaching the lungs. Drowning isn't always fatal. When a drowning causes death, it is known as a fatal drowning. Complete submersion is not required for lethal drowning; simply submerging the nose and mouth is sufficient. Drowning is a difficult process. It comprises liquid aspiration, struggle, involuntary movements, dyspnea, and cardiovascular responses. Drowning ultimately leads to hypoxia and death.

The ability to inject a drug into a free ranging animal using a remote injection system is a main stay of zoo and wild life medicine and the accepted and routine procedures of today for anesthetizing free ranging, dangerous, or hyper excitable animals are to be well understood for the proper preventive medical procedures, medical treatment, surgery, or scientific study. However, all these were earlier existing only as a dream, until remote injection-based gadgets like darts, blow pipes and distant drug-delivery gadgets like pistol and rifle were duly developed, in conjunction with safer injectable anesthetics.

Introduction
Haemoprotozoan diseases are highly prevalent in tropical and sub-tropical countries owing to the ubiquitous distribution of ticks and blood-sucking flies which are natural vectors for the pathogens. In India, theileriosis, babesiosis and trypanosomosis are major haemoprotozoan diseases and cause substantial economic losses to the livestock industry. Though vaccination of the susceptible stock by attenuated schizont vaccine is available for the control of tropical theileriosis in cattle, chemotherapy is the mainstay for the control of haemoprotozoan diseases. However, the limited available antihaemoprotozoan drugs is being depleted by a combination of two factors viz. emergence of drug resistance and the failure to replace old drugs (de Koning, 2017). Drug resistance against parasites is one of the emerging problems affecting veterinary health sector. Since last few decades, development of drug resistance in haemoprotozoan parasites to several drugs has been reported (Tuvshintulga et al., 2019; Ali et al., 2022). Though, understanding of drug resistance in parasitic protozoa is progressing steadily but possibly not as rapidly as parasites are becoming resistant to drugs. The genetic changes in the target sites, the reduced uptake and increased efflux of drugs, and metabolic regulations are the possible mechanism for the cause of drug resistance (Fairlamb et al., 2016). Anti-protozoan drug resistance has been reported in many economically important protozoa to isometamedium, diminazene aceturate, quinapyramine, suramin, melarsomine dihydrochloride, buparvaquone. The resistance initially evolves at genetic level of parasite with genetic traits that allow them to survive exposure to a drug, which is transferred to the subsequent generation thereby potentially increasing the percentage of resistant parasite that can survive subsequent exposure to the chemical. The emergence of drugresistant parasites has serious implications for treating clinical cases, leading to increased morbidity and mortality among the animals and control of the diseases.

Antimicrobial Susceptibility Test
The routine use of the modified Kirby-Bauer method is recommended.
Material
• Sterile cotton swabs
• Soyabean – Casein digest broth or Tryptone soya broth
• Non selective agar such as nutrient agar.
• 0.5 Mc Farland turbidity standard:
Solution A
Bacl2, 2H2O. 1.75G
Make upto 100 ml with distilled water.
Solution B
H2SO4 1.0 ml
Make upto 100 ml with distilled water.
Stock Solution
0.5 ml of solution A + 99.5 ml of solution B. Dispense in 5 ml amounts.
Seal and store in dark.
• Glass vials or tubes 10 ml capacity
• Muller – Hinton agar
• Antimicrobial discs
• Sterile forceps
• Ruler or calipers