eChapters

Major Histocompetibility Complex (MHC) is a closely linked cluster of genes which have codes for cell surface proteins known as MHC molecules. MHC molecules were previously called as HLA molecules. Since these molecules were first discovered on the leucocytes, these were called human leukocyte antigen or HLA molecules.

Embry Transfer Technology (ETT)

Definition: The process of removing one or more embryos from the reproductive tract of a donor female and transferring them to one or more recipient females.

Parasite- The word parasite is derived from the Greek. Para- beside and sitos- food. Parasites are those living organism which reside on or inside the body of some other species of living organism.

Host- Those organisms which provide food shelter and conducive environment to parasite for their growth, development and reproduction. e.g. Tape worm in small intestine of man and animals.

Disease = dis + aise (see + ease) old French word

Transmission- Movement of biological agents (Virus, Bacteria, Rickettsial, Fungi & Parasites) from one place to another place via vector or vehicle/ tools

Vector- Latin word- bearer

Vector is a living organism (usually an arthropod) which transfers infective forms of a parasite from one host to the other.

Veterinary physiology deals with the study of normal functions of animal systems. It includes the study of how animals work and the physical and chemical processes that occur within animals. The examples of various biological processes in animals include gas exchange, blood and circulation, osmoregulation, digestion, nervous and muscle systems, respiration, growth, reproduction, endocrine function and how animals behave and function in different environmental conditions. This also includes the possible manipulation of the reproductive processes by means of hormone manipulation techniques for more efficient livestock and poultry production.

There is only one type of scientific research and that is to solve a real problem or to understand the universe and provide a solution –either with the experiments or by putting a hypothesis. However, we have classified the research in various types as per our comfort. But for the employed researchers, it may be a matter of concern if they are working on time bound research schemes as their services may be co-terminus with the project and they may face the problem of un-employment, after termination of the scheme. According to the scholars’ activities and type of research being carried out in the country, we can discuss the subject under following topics.

Review of literature or consulting of literature is just beginning of a research project. The main intellectual work is to study the previous work meticulously and to draw conclusions regarding existing problems. This leads us to another intelligent part of the research i.e. planning of the research work. If you analyze what you are planning, it is only about materials to be employed and methodology of the research work (with planning of the work)- only these three parameters are under your control as results will be the outcome of these three facets while discussion will be how you consider your results in presence of previous research work. In fact, this statement of mine is more align to the sermon of “Shrimad Bhagwat Geeta” (5) where it is stated that man has control only on his actions (planning and conducting research) hence fulfill this duty without caring for the results-which in turn will depend on your analyzing the previous facts and how you have planned to solve the problem. Therefore, pay full attention on these three facts of the research.

Introduction

Tissue culture refers to the technique of growing cells, tissues, or organs under controlled, artificial conditions. This allows propagation of tissues from a small sample of cells/tissues under sterile conditions. Plant tissue culture is widely used for various purposes, including the production of disease-free plants, rapid multiplication of plants with desirable traits, genetic modification, conservation of rare or endangered species, etc. Tissue culture is a valuable technique because it enables consistent and large-scale production of plants, ensures genetic uniformity, and allows manipulation of plant biology at cellular level. In this chapter, we will discuss about the major types of tissue culture techniques and their advantages, disadvantages, as well as applications in brief.

Different Types of Tissue Culture

Callus culture involves induction and growing of unorganized, undifferentiated cell masses from an explant on a nutrient/culture medium. The part of plant used to induce callus is called explant which can be tissue, organ or part of a plant.

Organ culture is used to maintain or grow an entire organ or a part of organ in vitro. It preserves the structure and function of the organ for studies or transplantation.

Embryo culture involves isolating and growing embryos from seeds or ovules in a nutrient medium. It is used to bypass seed dormancy or rescue embryos from hybrid crosses that may not develop naturally.

Cell suspension culture involves growing dispersed cells or small cell clusters in a liquid medium under continuous shaking. This is used for large-scale production of cells, secondary metabolites, and studying cell biology..

Chemotherapy in Parasitology deals with the treatment of disease caused by different parasites by specific drugs; meanwhile particular drug has got the particular action against the particular parasite. Recently chemotherapy is a extensively used and emerging branch for the control of different stages of parasites that is normally not killed by the conventional methods of treatment. Thus, chemotherapy plays an important role in the treatment and control of parasitic infections by avoiding the outcome of the danger of the disease by treatment of the affected animals. They should have the maximum parasitotrophic action and minimum organotrophic action. It is mainly divided into two types: 1) Rational therapy: It is a mode of treatment based on the pharmacological actions of drugs with relation to disease. 2) Supportive therapy: It is a method of treatment other than drugs, e.g. giving high protein diet in the oedematous condition such as bottle jaw in fascioliosis and amphistomiosis. The drugs used for the killing or complete removal of the parasites from the body of the host called antiparasitic drugs.

Introduction 
The discovery of antibiotics—one of the greatest medical breakthroughs of the 20th century—began when Sir Alexander Fleming noticed that the fungus Penicillium notatum inhibited the growth of Staphylococcus spp. This finding sparked a search for similar properties in other fungi and bacteria. From 1940 to 1960, known as the ‘Golden Era of Antibiotic Discovery’, most modern antibiotics such as streptomycin, tetracycline, rifampicin, and nalidixic acid were identified through natural product screening (Clardy et al., 2006; Lewis, 2013). However, the declaration that “it is time to close the book on infectious diseases and declare the war against pestilence won” proved to be premature (Davies & Davies, 2010). It was not a final victory but a fragile truce. In the ongoing war between humans and microbes—nature’s own creations—our successes are brief, and the microbial battleground keeps shifting. Bacteria’s genetic adaptability, coupled with human complacency, led to antimicrobial resistance (AMR), where microbes gradually evolved resistance to almost all known antibiotics (Ventola, 2015). Resistance appeared soon after antibiotics entered clinical use, but the emergence of methicillin-resistant Staphylococcus aureus (MRSA), multidrug-resistant Mycobacterium tuberculosis, and extended-spectrum ß-lactamase (ESBL)-producing bacteria marked major setbacks (Prestinaci et al., 2015; WHO, 2023). AMR gained global attention with the rise of pan-drug-resistant strains—resistant to all antibiotic classes—seen in Klebsiella (India), Acinetobacter, and Pseudomonas (China, Italy, Greece), and extensively drug-resistant tuberculosis (XDR-TB). The infamous case of

Introduction
Aquaculture is one of the sunrise sectors contributing a significant quantity to the global supply of fish for human consumption. Fish is a superior source of highquality animal protein and highly digestible energy. Disease problems in farmed fishes are one of the main barriers, resulting in significant financial losses up to a tune of US$2.48 B, 14.95% of the annual aquaculture production value in Indian aquaculture. In the aquatic environment, bacteria are quite prevalent and the majority of bacterial pathogens are found in the water’s natural flora. They only spread illness when poor husbandry practices, inadequate nutrition, and unfavourable environmental circumstances contribute to fish stress. Pathogenic bacteria, including Aeromonas spp, Escherichia coli, Staphylococcus spp, Salmonella spp., Shigella spp., Yersinia enterocolitica, Clostridium botulinum, Plesiomonas shigelloides, and Listeria monocytogenes, can be either naturally present in fish or introduced to them during handling, processing, and storage. Antimicrobial resistance (AMR) in Indian aquaculture presents a multifaceted and growing challenge at the intersection of public health, environmental sustainability, and food security. As aquaculture expands to meet rising global demands for protein, the sector has increasingly relied on antimicrobials to prevent and treat bacterial infections. However, due to some indiscriminate and unregulated use of these agents as well as the householdsewage, hospital effluents, contamination from agricultural wastes andinadequately treated urban waters that enter the aquaculture through drains and rivers,creates strong selective pressure and accelerate the development and dissemination of resistant pathogens in aquatic environments posing a serious threat not only to farmed fish but also to human health through environmental contamination and the broader food chain. Resistant bacteria and resistance genes can spread through water systems, biofilms, and aquaculture products, creating reservoirs that contribute to the broader One Health AMR crisis. Food borne pathogens (Aeromonas spp., Vibrio spp., and Streptococcus spp.) from aquatic animals were found resistant to antimicrobial agents that are relevant for therapeutic usage in human clinical settings. E. coliwas found to be resistant as a sign of possible human and terrestrial animal effects. Distinguishing resistance that has been selected in different sectors is extremely difficult and caution is needed while trying to attribute the source of antibiotic resistance in bacteria in the aquatic environment. Understanding the drivers, mechanisms, and impacts of AMR in aquaculture is essential for developing effective mitigation strategies and sustainable management practices that safeguard both aquatic and human health.

Introduction
The discovery of antibiotics in the early 20th century revolutionized medicine, agriculture, and public health. These compounds, capable of inhibiting or destroying pathogenic bacteria, not only saved millions of human lives but also transformed animal production systems by reducing morbidity and mortality, improving growth rates, and ensuring food security (Phillips et al., 2004). The application of antibiotics in food animals,whether for therapeutic, prophylactic, or growth-promoting purposes,has been instrumental in increasing global meat, milk, egg, and fish production, thus addressing the nutritional needs of a growing population (Darwish et al., 2013; Chen et al., 2019). However, the indiscriminate and excessive use of antibiotics in animal agriculture has created unintended consequences, most notably the presence of antibiotic residues in foods of animal origin and the global acceleration of antimicrobial resistance (AMR) (Bacanli & Basaran, 2019; Shahid et al., 2021). Antibiotic residues in food is the trace amounts of active compounds or its metabolites that remain in edible animal tissues, milk, eggs, and aquaculture products causes significant concerns for both consumer safety and public health. Even when below the maximum residue limits (MRLs) established by regulatory authorities, prolonged exposure may lead to allergic reactions, disruption of the gut microbiome, reproductive and developmental toxicity, mutagenicity, nephropathy, and in certain cases carcinogenicity (Ngangom et al., 2019; WHO, 2020). Furthermore, residues contribute to the selection pressure that drives the emergence and dissemination of resistant bacterial strains in humans, animals, and the environment (FAO, 2019; O’Neill, 2016). The One Health framework highlights these interconnected pathways, recognizing food as a critical link between veterinary antibiotic use and human AMR burden (Robinson et al., 2016). Globally, approximately 73% of antibiotics are consumed in food animal production, with projections estimating a further 11–67% increase by 2030,largely by intensification of livestock and aquaculture in developing economies (Van Boeckel et al., 2015; Tiseo et al., 2020). While industrialized nations have implemented bans on antibiotic growth promoters and introduced robust surveillance programs, most low- and-middle-income countries still facing challenges (Antibiotics, 2021; WHO, 2019). Consequently, foods containing antibiotic residues frequently enter local and international markets, undermining food safety standards and exacerbating AMR risks (Darwish et al., 2013; Antibiotics, 2021). Antimicrobial resistance (AMR) has emerged as a major global public health crisis, directly causing an estimated 1.27 million deaths and contributing to nearly 5 million deaths worldwide in 2019. Recognizing its severity, the World Health Organization (WHO) has identified AMR as one of the top ten threats to global health(Murray et al., 2022). By 2050, global economic losses linked to AMR are projected to reach USD 100–210 trillion, with Asia bearing a disproportionate mortality burden (O’Neill, 2016). Countries like India, with large livestock populations, rapidly growing aquaculture industries, and high human antibiotic consumption, represent critical hotspots where food, health, and environmental risks intersect (Chauhan et al., 2018; ICMR, 2020). Given these alarming trends, understanding the occurrence, detection, and consequences of antibiotic residues in foods of animal origin is paramount. This chapter explores the co-relationship between origin of antibiotic residues and AMR, regulatory measures aimed to safeguard food safety and strategies for prevention and control, framed within the One Health approach.

Introduction
It is reasonable to consider that the history of humanity has been marked by two transformational revolutions: the cognitive revolution (35,000 to 70,000 years ago), when Homo sapiens began to manifest our capacity to abstract, imagine things that did not exist and give meaning to non-representational thoughts; the agricultural revolution (10,000 to 12,000 years ago), when Homo sapiens stopped being a hunter/collector to settle on land, cultivating the soil and raising domesticated animals. It was possibly the beginning of property ownership, monogamy, family and also when malaria, and other diseases more easily spread in communities, became consolidated as human diseases. It was with the cognitive revolution that things changed and our previously acquired abilities of creating images and dealing with abstract concepts started to push humankind to become the “Dominant Mammal” controlling all other animals and Earth’s environments. Progressively, man learned to work with wood, iron and all minerals extracted from the soil, produced clothes with leather and wool from animals, linen and cotton from plants, silk from insects, and latter from natural oils created arts, jewellery, dynamite, electricity, vaccines, transatlantic ships, locomotives, cars, computers, antibiotics, contraceptives, robots, portable cell phones, informatics, bioengineering, internet, artificial intelligence, social networks and many other innovations . Not surprisingly, conscious of all these attributes, man felt important, central and essential, falling into the temptation of judging himself a magnificent creature with all rights and that became deep rooted in some cultures. For the pleasure,comfort, sophistication and power, man interfered with and altered the environment in a so ambitious and predatory manner that he modified and compromised his and other species living conditions, causing also climate changes that threaten his own survival on the planet. With time, it became clear that, in addition to this entirely anthropocentric “Ego’s” point of view, there might be another perspective fromwhich one can perceive the world and interact with it. An ecological “Eco’s” perspective corresponds to a compassionate view (how can we contribute to the greater good and make the world a better place) of the Globe. After all the damage done to nature by man, moving from the socalled Ego to the Eco attitude became a mandatory needConcerning Global Health, for a long-time, human health has benefited by sacrificing the “health” of wild ecosystems (e.g., deforestation and conversion of wilderness to farmland, damming of water for irrigation, destruction of swamps and dislocation and jeopardy of wild species) which reflects a protectionist vs utilitarian conflict, over the question of whether to put human domination of the biosphere on hold or whether to embrace it .It hides unaddressed concerns about the value of (macroscopic) life (human, animal or plant), the definitions of health and wellbeing (human, animal, plant and environmental) and their relative importance. This has hampered the development and acceptance of a One Health (OH) understanding of Global Health.

A tumor is said to be an abnormal growth of cells to form a lump or mass of transformed cells. This growth occurs due to loss of regulatory control of cell division. The majority of cells and organs have a balance between cell renewal and cell death. A cell has a particular life span;when it dies a new cell is generated. In normal condition, this system is regulated through cell cycle and cell division but at the time of any abnormality this growth mechanism is totally disturbed and failed. These cells give rise to clone of the cells and eventually produce tumor.

The well-being of a person depends on his immune system. Any deficiency in any component of immune system may lead to defects in the normal functioning of his body and makes him more susceptible to diseases. The immunodeficiency may be either in specific components (B cells or T cells) or nonspecific component (phagocytes and complement) of the immune system.

One of the characteristics of the immune system is to recognize and discriminate self from the non-self antigens.  But, sometimes, there is a failure to discriminate between self and non-self antigens in the body and an autoimmune response occurs. Body starts producing antibodies against its own cells/antigens. These antibodies are called autoantibodies and this state is called autoimmunity.

Rivolta (1873) first described the chain forming cocci in pus collected from the equine infection. Rosenbach (1884) established the genus Streptococcus’ Nocard and Mollereau (1887) first observed the relationship between the bovine mastitis and Streptococcus agalactiae. Lancefield (1933) classified beta-haemolytic streptococci on the basis of group specific-carbohydrate antigens.

Properties of genus

1. Morphology: Streptococci are gram positive cocci, capsulated, non-sporing and non-motile. Each coccus cell is 1µm in diameter. They are arranged in a pair or chain of cells as the cell division occurs in one plane(Figure 1 & 22). The chain formation and the chain length are variable. Streptococcus equi ssp. equi is a constant chain producer. Young cultures are gram positive whereas bacteria present in the pus and older cultures in the laboratory are often stained as gram negative.

Corynebacterium diptheriae was first observed by Klebs in 1883 and was described in details by Loeffler in 1884. So it is also known as ‘Klebs- Loeffler bacillus’. In 1888, Nocard isolated a similar type of bacteria from cases of bovine farcy. In 1894, Preisz described it completely and revealed its similarities with the diphtheria bacilli. Later it was named as Corynebacterium pseudotuberculosis (Preisz-Nocard bacillus). Bollinger (1890) first reported C. renale from the cases of pyelonephritis in cows.

The genus Trueperella was proposed by Yassin and others (2011) to describe T. pyogenes previously known as Arcanobacterium pyogenes or Actinomyces pyogenes or Corynebacterium pyogenes. The genus Arcanobacterium was first described (Collins and others, 1982) to include the bacteria originally isolated as Corynebacterium haemolyticum from the wounds of American soldiers. On the basis of 16S rRNA comparisons and menaquinone and phospholipid compositions it is proposed that the species Arcanobacterium pyogenes should be reclassified as members of the new genus Trueperella.

The genus Rhodococcus was first introduced by Zopf (1891) as a soil bacterium used in horticulture. Magnusson (1923) described C. equi (Rhodococcus equi) from suppurative pneumonia of a foal.

Since the periods of Hippocrates and Lord Buddha cholera like symptoms was described in human. The first outbreak of cholera was described in India in 1817. Filippo Pacini (1854), an Italian anatomist, observed a gram-negative bacterium associated with human cholera. Robert Koch (1884) first isolated and confirmed the association of ‘comma-shaped bacteria’, later designated as Vibrio cholerae with the disease in Calcutta (India). In 1959, Sambhu Nath De, Professor of Pathology at Nilratan Sircar Medical College in Calcutta discovered the exotoxin produced by V. cholerae and a simple method (rabbit ligated ileal loop assay) to study the in vitro effect of exotoxins. The Ganges delta of India and Bangladesh is considered as the worst affected place with cholera although the infection is widespread throughout the world. The spread of cholera in different continents occurred through six ‘waves’ (‘pandemics’) since 1817. The current seventh pandemic (7P) was originated in Indonesia (Sulawesi) in 1961 and spread throughout Asia, Africa and Latin America. In 1963, the seventh pandemic reached South Asia and circulated for more than 50 years with intermittent transmission to other continents. The recent major 7^th pandemic outbreak was detected in Haiti causing more than 9400 deaths in 2010 which was originated through patients from endemic countries.

In 1886, Escherich observed Campylobacter like organisms in stool samples of children with diarrhoea. In 1913, McFaydean and Stockman first confirmed the bacteria as Campylobacter in foetal tissues of aborted sheep. Confirmatory tests were also carried out by Smith in 1918 when similar bacteria were isolated from aborted bovine foetuses. The bacteria were then known as Vibrio foetus. In 1963, due to certain differentiating characteristics, the organisms were separated from Vibrionaceae family and the new genus Campylobacter (means ‘curved rod’) under Campylobacteraceae family was proposed.