eChapters

A. Viral Diseases of Shrimp

Shrimp farming which has grown to an industry in the last three decades is young compared to fish farming in the world. Yet the shrimp farming is facing serious problems with several types of viral diseases. Intensive culture in hatcheries and grow outs along with movement of stock across national and international borders of these animals with poor immune system has encouraged emergence of large number of viruses. During a short span of 30 years, 15 viruses of economic concern have been reported in shrimp culture of the Asia Pacific region. Shrimp viruses (Plate 8) can be broadly categorised into two groups:

1. Viruses infecting ectodermal (epidermis, hypodermal epithelium of fore and hindgut, nerve cord and nerve ganglia) and mesodermal (hematopoitic organs, antennal gland, gonads, lymphoid organ, connective tissue and striated muscle) origin tissues and replicating within the cytoplasm (YHV, TSV) and within the nucleus (IHHNV, WSSV), 2. viruses like MBV, HPV, BMNV, and BP infecting endodermal origin tissue and replicating within the nucleus of hepatopancreatic and mid gut epithelial cells. Lack of established shrimp cell line is the major drawback in study of shrimp viruses. Following are some of the common viruses causing diseases in shrimp hatcheries and grow out ponds in the Asia Pacific region.

Plant viruses, like all other viruses, are obligate intracellular parasites that do not have the molecular machinery to replicate without the host. The plant viruses are defined as viruses pathogenic to higher plants. The discovery of plant viruses causing disease is accredited to Beijerinck who determined in 1898 that the plant sap obtained from tobacco leaves with the mosaic disease remained infectious even after passing through a filter. This was in contrast to bacteria, which were retained by the filter. Beijerinck referred to the infectious filtrate as a contagium vivum fluidum, thus, he used modern term virus.

Viruses occasionally cause significant problems in vegetable crops. However, the prevalence and severity of viral diseases differ from year to year. Aphids spread many of the viral diseases observed in vegetables. There are two types of viral transmission by aphids, i.e., persistent and non-persistent transmission. It is important to understand the difference between these two because persistent and non-persistent viruses differ both in their uptake and behaviour within the insect vector, consiquently, tactics used to limit their and spread vary considerably. In persistent transmission, the aphid usually carries the virus for life. Uptake of virus requires extended feeding and after an incubation period of several hours or days, the virus replicates and circulates within the insect. Because of the time required for feeding before acquisition by an insect vector, the spread of persistent virus is favoured by colonizing aphid species that spend time in the crop. Controlling the aphid vectors with insecticides can reduce the spread of persistent plant virus significantly. In contrast, aphids can acquire non-persistent viruses (NPV) within a few seconds after sampling an infected plant. Winged migratory aphids can move quickly from infected plants onto healthy ones, transmitting the virus in the process. Aphids rapidly lose the virus particles from their mouthparts, which are cleaned when they feed on the next available plant and are unable to transmit disease to additional plants. Because of the speed in which aphids acquire and transmit non-persistent viruses, insecticides are not usually effective in controlling their spread. One of the most common viruses found in many vegetable crops is cucumber mosaic virus (CMV). This is transmitted by several aphid species in a non-persistent manner. There are several strains of CMV that can infect over 775 different plant species in 85 families including snap bean, peppers, tomato, lettuce, tobacco and sugar beets. Symptoms vary depending upon the plant species infected but range may be from yellow-green mottling on leaves and fruits to severe stunting of plants. The viral diseases affecting different vegetable crops are being discussed below:

Clinical Symptoms • External haemorrhages

• Pale gills • Ascites

• Destruction of tissues in the kidney, spleen, and liver

• Excessive mucus secretion

• Skin hemorrhages with edema of the tissues

• Skin ulceration around the mouth and base of the fins

Causative Agent: Rhabdovirus

Host (Common sp.)

• Common carp

• Koi carp

• Crucian carp

• Silver carp

• Bighead carp

• Grass carp

• Goldfish

Ranikhet Disease

Ranikhet disease is a contagious viral disease of poultry characterized by high mortality petechial hemorrhage in proventriculus, ulcers and hemorrhage at caecal tonsils and pneumoencephalitis. It is also known as Newcastle disease (Fig.3.1).

Etiology

• Paramyxo virus

• RNA virus-3 types

• Lentogenic- mild virulent

• Mesogenic- moderate virulent

• Velogenic- highly virulent

1 The serotype of aphthovirus causing most outbreaks of FMD in India is

a) A b) O

c) C d) Asia-1

Wound healing is a complex phenomenon with three distinctive yet overlapping phases i.e. Inflammatory, proliferative and remodeling phases. Present study was conducted to unravel the molecular insights of Mangiferin in immunocompromised excisional rat model. Firstly, immunocompromised state was established following hydrocortisone injection @80 mg/kg body weight through intra muscular route and determining the immunocompromised state with neutrophilia, lymphocytopenia and reduced splenic weight in adult male rats weighing 200-250 grams. Then, 120 animals were randomly and equally divided into five groups i.e. group I served as Healthy control, group II served as Immunocompromised control, group III served as Immunocompromised group treated with silver sulphadiazine and group IV and V served as Immunocompromised group treated with 2.5 % Mangiferin and Immunocompromised group treated with 5 % Mangiferin, respectively. Study was conducted for a period of 28 days. Six animals were humanely sacrificed at weekly interval till day 28th of study. Wound healing efficacy and molecular cascading of pharmacodynamics of Mangiferin was determined following gross studies including digital photography, wound area measurement and per cent wound contraction and biochemical indices viz. hydroxyproline, DNA content, total protein and LPO assay.

The human civilization and environmental eco-system are the two most important components of real world. The technology intervention to safeguard human civilization and the environment has always been the foremost priority of scientific and engineering community through their innovative expeditions.

The emergence of Large Language Models has enabled the development of virtual teaching assistants capable of providing students with continuous, interactive, and personalized academic support. This chapter examines the role of LLM-powered chatbots and intelligent tutors in modern education. Unlike conventional digital resources, AI teaching assistants can engage learners through natural-language dialogue, explain difficult concepts, provide examples, generate practice activities, offer hints, and deliver immediate feedback. They can support individualized learning pathways by adapting explanations and learning materials to student needs, performance, and pace. The chapter explores applications in tutoring, assessment, academic guidance, interactive textbooks, student support, and self-directed learning. AI assistants can also reduce routine teacher workload by supporting activities such as grading, question generation, content recommendation, and classroom analytics. However, challenges remain concerning hallucination, accuracy, privacy, algorithmic transparency, inclusivity, and the appropriate balance between automated assistance and human mentorship. Large-scale and long-term evidence is still needed, particularly in diverse and low-resource educational settings. The chapter therefore emphasizes human–AI collaborative instruction, educator training, ethical integration, and responsible deployment of intelligent teaching assistants.

Importance of virtual water in agriculture
Virtual water is with the meaning of the concept when water embedded in goods and services and is exchangeable from one country to a different. The country is under water-scarce; the water that’s ‘saved’ is often used towards other ends. Water-scarce countries (like Israel) discourage the export of relatively water-intensive crops (like orange, water melon) precisely to stop large quantities of water from being exported to different parts of the earth. In recent years, the concept of virtual water on trade has gained weight both within the scientific also as restricted by the political debate. The notion of the concept is ambiguous. It changes between an analytical, descriptive concept and a political induced strategy. As an analytical concept, virtual water trade represents an instrument that permits the identification and assessment of policy options not only within the scientific but also within the political discourse. As a politically induced strategy, the question of virtual water trade are often implemented during a sustainable way, whether the implementation are often managed during a social, economical, and ecological fashion, and that countries the concept offers a meaningful option. the info that underlie the concept of virtual water can readily be wont to construct water satellite accounts and brought into economic models of international trade like the Computable General Equilibrium of Global Trade Analysis Project such a model are frequently wont to study the economic implications of changes within the water system or water policy, also because the water resource implications of economic development and trade liberalization. The data pertaining to virtual water is product of GTAP.
Keywords: Virtual water; foodstuff and food; water content in different food materials; water deficit areas;

Plant viruses are unusual group of plant pathogens that almost depend on host cellular machinery for their survival, hence categorized under obligate intracellular parasites. They are smart entities as they encode very few proteins but take the advantage of host cellular metabolism to complete their replication and movement within plants cells. These viruses passively enter the host cells through various means such as wounds and injury, environmental factors, or by several vectors. Genomic material, either RNA or DNA of viruses, disassembles inside the plant cells, and replicates and transcribes mRNA to protein with the help of host factors and energy. Once they manage to assemble their required genetic materials and capsid protein, virions are then released to neighboring cells for further infecting other cells. They even reach to distant cells through plant vascular system causing systemic infection and different symptoms in host plant.

The most important property of a virus is its infectivity or ability to invade a cell and parasitize that cell to replicate itself. To measure infectivity, a titre is defined as the given number of infectious virus units/unit volume and an infectious unit is the smallest amount of virus that produces some recognizable effect in the host system. There are two basic types of infectivity assays (a) Quantal assays and (b) Quantitative assays.

Quantal assays do not measure the number of infectious virus particles present in the inoculum but denote a value for the virus titre where measurement is based on an all or none principle, CPE + or -, dead or alive etc. In the quantitative assays, the number of virus particles present in the suspension can be quantified.

Viruses can be cultivated only in living cells. Laboratory animals, embryonated avian eggs and cell cultures are three systems available for this purpose. These three systems are used for the basic procedures of isolation and identification of viruses, maintenance of stock cultures and production of vaccines.
Cultivation of Viruses in Laboratory Animals
Animal inoculation helps to confirm the infectious nature of the disease. Laboratory animals used for many kinds of virological works such as clinical studies, pathogenicity of viruses, epizootiology, potency tests on vaccines and production of diagnostic and prophylactic antisera.

An ideal experimental animal is one that is
1. Uniformly and fully susceptible to the virus under study
2. Free from intercurrent infection and adventitious lesions and
3. Inexpensive purchase and maintain
If possible it is better to use germ free, specific pathogen free or colostrums deprived animals for experimental purpose. The same species of animals or atleast closely related species of the natural host is selected for inoculation, wherever possible. For example in case of swine fever, which shows a high degree of host specificity, the same species should be used for inoculation. in others such as in case of rabies with low host specificity, the causative virus will grow in a wide range of animals.

Principle

Isolating the virus in a laboratory is the gold standard for diagnosing many viral infections. Virus isolation is a highly specialised technique used to diagnose viral infections and produce a stock of viruses for research purposes. The isolation of the virus relies on the suitability of the sample, the ability of the cells to allow entry, the successful replication of the virus, and the release of viral particles from the cells. The choice of cell lines is dependent upon the suspected viral disease and the availability of such cell lines in the laboratory.

Materials required

Equipment

a) Biosafety cabinet level 2 (B2)

b) Carbon Dioxide (CO2 ) Incubator (set to 37°C with a 5% CO2 in air atmosphere)

c) Refrigerated centrifuge

d) Refrigerator

e) Inverted Microscope

f) Water bath

g) -86°C/-80°C deep freezer

h) Autoclave

i) Hot air oven

j) Filtration Assembly

Principle

Neutralization refers to the process of reducing or nullifying the effect of a specific component. Neutralization is a process in which the effects of viral antigens or viruses reduce through Ag-Ab reactions. Neutralizing antibodies are a specific type of antibodies that play a role in neutralization. Not all antibodies generated within our body possess the capability to impede the effects of antigens. Only antibodies with the ability to neutralize can prevent the uptake of viral particles by cells and counteract their effects. The virus neutralization assay is a serological test utilized to identify the existence and extent of functional systemic antibodies that hinder the ability of a virus to cause infection.

Media and Materials

Equipment

a) Biosafety cabinet level 2 (B2)

b) Carbon Dioxide (CO2 ) Incubator (set to 37°C with a 5% CO2 in air atmosphere)

c) Refrigerated centrifuge

d) Refrigerator e) Inverted Microscope

f) Micro pipettes (1-10 μl, 10-200 μl, 100-1000 μl)

g) -86°C/-80°C deep freezer

h) Autoclave

i) Hot air oven

j) Filtration Assembly

Plant viruses are ultramicroscopic particles that multiply only within living cells and are potentially pathogenic while composed of nucleic acids surrounded by protein coat.

More than half of the known viruses cause diseases of plants. All plant species are probably susceptible to one or more plant viruses. Symptoms of virus infection may include stunting, yellowing, necrosis, mosaic, mottling, ring spots, or abnormal structures. Economic damage consists of reduced yield and quality.

Viruses neither divide nor produce any kind of specialized reproductive structures such as spores. Instead, they multiply by inducing host cells to form more viruses. Viruses causes disease not by consuming cells or killing them with toxins, but by utilizing cellular substances during multiplication, taking up spaces in cells, and disrupting cellular processes. These in turn upset the cellular metabolism and lead to the development of abnormal substances and conditions injurious to the functions and life of the cells or the organism. The property of transmissibility is an essential criterion for viruses. Plant viruses are transmitted from plant to plant in a number of ways. Mode of transmission includes vegetative propagation, mechanically through sap, seeds, pollen, dodder and by insects.

Virus can be defined as a genetic element containing either DNA or RNA that replicates in host cells as intracellular parasites but is characterized by having an extracellular state.

Virus can use the metabolic machinery of the host cell and can modify the genetics of the host cell. Virus has both extracellular and intracellular state.

Extracellular State

Outside the host cell, the virus is a minute particle containing nucleic acid surrounded by protein, which is referred as virions or virus particles. Virions are inert and have no biosynthetic and metabolic functions. Extracellular state or virus particle is the perfect stage of virus to study the morphology and chemistry.

Intracellular State

The active state in which the virus replicate in the host cell. When the virus nucleic acid is introduced to host cell and replication starts, the process is referred as infection. The cell in which infection of virus and replication takes place is referred as host cell.

A five-kingdom classification system fails to classify viruses because they are not considered to be living. They neither reproduce independently nor utilize energy

General properties of virus

Viruses differ fundamentally from other classes of microorganism in that:

1.They are ultramicroscopic disease-producing entities.

2.They are simple in structure, basically composed of nucleic acid wrapped up in a protein coat.

3.The genome nucleic acid is either DNA or RNA , either single stranded or double stranded, but never both

4.Viruses have no metabolic activity of their own and lack enzyme systems and other constituents fundamental for independent growth and multiplication.

5.They do not posses ribosomes, nor transfer RNA and enzymes required for synthesis of nucleic acids and proteins.

6.Viruses are incapable of growth and division.

A. Viruses: Structure and Characteristics
What is a Virus?
A virus is an infectious agent composed primarily of nucleic acid (either DNA or RNA) enclosed in a protein coat called a capsid. In some cases, viruses may also have an outer lipid membrane or envelope. Plant viruses are much smaller than bacteria and fungi, and they lack the cellular structures necessary for independent life. They can only replicate by hijacking the host cell’s machinery.
Structure of Viruses
1. Nucleic Acid: This is the genetic material of the virus, which can be either RNA or DNA, and it carries the instructions for making new virus particles. Plant viruses are mostly RNA viruses, though some DNA viruses also exist.
2. Capsid: The protein shell that encloses and protects the nucleic acid. The capsid is made of protein subunits called capsomeres and can take various shapes, such as rod-like (rigid or flexible) or spherical.
3. Envelope: Some plant viruses may have an outer lipid envelope derived from the host cell’s membrane, which provides additional protection.