eChapters

Multiple cropping includes both inter and sequential cropping systems and here the main objective is to utilize the available resources effectively in a given environment. Number of indices are available for assessing land use and the yield advantage of crop mixtures compared to pure stands. These indices not only reflect the difference in criteria used to appraise advantages often encompassing aspects of quality or values as well as yield, but also reflects the different reasons for which an assessment is made.

1. Rotational intensity (RI): Crops are grown in a recurring sequence on the same piece of land with sufficient diversity and intensity. Crop rotations to control erosion/ to improve or maintain soil fertility and to manage weeds, insects and disease. Lower values of rotational intensity indicate mono cropping and higher values of rotational intensity indicates more rotation.

In sustainable agriculture the word sustain is derived from the Latin word sustinere (sus-from below and tinere-to hold), to keep in existence or maintain, implies long term support or performance. As it pertain to agriculture, sustainable describes farming system that are capable of maintaining their productivity and their usefulness in society indefinitely. Such system should be resource conserving, socially supporting, commercially competitive and environmentally sound. Systems approach is essential for understanding sustainability and it gives us tools to explore the interconnections between farming and other aspects of our environment and sustainability implies at the following,

1. Meeting the basic needs of all people and giving this priority over meeting the greeds of a few
2. Keeping population densities if possible below the carrying capacity of the region
3. Adjusting consumption patterns and the design and management of systems to permit the renewal of renewable resources
4. Conserving, recycling and establishing priorities for the use of non- renewable resources
5. Keeping environmental impact below the level required to allow the systems unaffected to recover and continue to evolve.

Various definitions have been provided for what constitutes sustainable agriculture ranging from the narrow focus on economics or production to the incorporation of culture and ecology. Wendell Berry has simply said A sustainable agriculture does not deplete soils or people.

Classifications of cropping systems

Depending on the resources and technology available, different types of cropping systems can be adopted on farms and which are as below.

Mono cropping /single cropping: Mono cropping refers to growing only one crop on a particular land year after year or practice of growing only one crop in a piece of land year after year. Example, growing only crops during kharif in rainfed areas and this is due to lack of irrigation facilities and crops depend on rainfall alone.

Various types of cropping systems are practiced in a farm or region. They should be evaluated to find out their stability and relative advantages in yield. Again, comparisons may be made with reference to land use efficiency, biological potential and economics. Following are the important indices for assessment of competition and yield advantage:

1. Relative yield total (RYT): The oldest establishment measure of the yield advantage of crop mixtures is the Relative Yield Total. The RYT index was designed as a measure of the extent to which various crop components shared common resources, rather than as a direct measure of yield advantage.

When crops are grown in either intercropping or sequential cropping interaction between different component crops occurs which is essentially a response of one species to the environment as modified by the presence of another species is commonly referred to as interference or interaction.

The interaction are classified into three groups

1. Competitive interaction: One species may have greater ability to use the limiting factor and will gain at the expense of the other and this is called competitive interaction or when one or more growth factors are limiting, the species that is better equipped to use the limiting factor(s) will gain at the expense of the other and this is called competitive interaction.
2. Non competitive: If the crops are grown in association and the growth of either of the concerned species is not affected, such type of interaction is called non competitive interaction or if resources (growth factors) are present in adequate quantities, as a result of which, the growth of either of the concerned species is not affected, then it is non-competitive interaction or interference.
3. Complementary: If one species is able to help the other, it is known as complementary interaction or if the component species are able to exploit growth factors in different ways (temporal or spatial) or if one species is able to help the other in supply of factor (like legumes supplying part of N fixed by symbiosis to non-legumes), it is complementary interaction or interference and also referred to as Annidation.

The stability of yield is an important characteristic to be considered when judging the value of a cropping systems when compared to others cropping systems. Here, we focus on multiple cropping and how this agroecological practice can be used to increase the sustainability of crop production. Strip, mixed and relay intercropping can be used to increase crop yields through resource partitioning and facilitation. In addition to achieving greater productivity, diversifying cropping systems through the use of strategic cropping systems will increase yield stability, reduce weeds, pests, disease and improve soil health. Several multiple cropping systems are already implemented in industrialized agricultural landscapes, including mixed intercropping with perennial grasses and legumes as forage and relay intercropping with winter wheat and red clover. Because multiple cropping systems will provide numerous benefits, researchers should be clear about their objectives and use appropriate methods so as not to draw spurious conclusions when studying multiple cropping systems. In order to advance the practice, experiments that test the effects of multiple cropping systems should use standardized methodology and researchers should report a set of common criteria to facilitate cross-study comparisons. Multiple cropping systems with two or more crops appears to be less common with annuals than perennials, which is likely due to differences in the mechanisms responsible for complementarity. One area where intercropping with annuals in industrialized agricultural landscapes has advanced is with cover crops, where private, public and governmental organizations have harmonized efforts to increase the adoption of cover crop mixtures.

Crop diversification refers to the addition of new crops or cropping systems to agricultural production on a particular farm taking into account of the different returns from value-added crops with complementary marketing opportunities.

Major driving forces for crop diversification

Crop diversification provides better conditions for food security and enable farmers to grow surplus products for sale at market and thus obtain increased income to meet other needs related to household well being. Crop diversification enable farmers to gain access to national and international market with new products, food and medicinal plants. Diversification from the monoculture of traditional staples are important for nutritional benefits of farmers in developing countries and can support a country to become more self reliant in terms of food production. Diversification also manages price risk and compared to monoculture techniques. For diversification crops generally consists of more sustainable natural resources and again, diversified farms are usually more economically and ecologically resilient.

The crop production is affected by the plant type, climatic condition, soil type and management factors. The production of the plant might be increased by changing plant type and increasing the grain filling period under certain climatic condition where management and soil factors are not limited. There is a direct relationship between the plant type and crop yield because the orientation and number of leaves play an important role in carbon fixation (photosynthesis). Again any variety/cultivar will contribute 21-25 per cent to the total yield of any crop in general. In recent years due to development of photoinsensitive varieties and hybrids which are more fertilizer responsive and high yielding varieties lead to increase overall production in the country.

Plant ideotypes

Refers to plant type in which morphological and physiological characteristics are ideally suited to achieve high production potential and yield reliability. The concept of ideotype was given by Donald in 1968 and he illustrated that there should be minimum competition between the crops and crop must be competent to compete with weeds. Ideotype is defined as a biological model which is expected to perform or behave in a predictable manner within a defined environment. On the basis of environment, Donald and Hamblin (1976) identified two forms of ideotypes that is isolation ideotypes and competition ideotypes. Isolation ideotypes are suitable for mono/single cropping and competition ideotypes are suitable for mixed cultivation.

Agriculture is the most important sector in India in terms of the population dependent on it. Although agriculture now accounts for on 14 per cent of GDP, it is still main source of livelihood for the majority of the rural population. Rapid growth of agriculture is critical for development of rural economy and viable development of rural economy will leads to overall development of country. Diversification in agriculture is need of the hour, any cropping system comprising crops with varied maturity period, crop canopy and high yielding potential is need for an average farmer. Again cropping systems depending upon the soil type, total rainfall and arrival of monsoon in the region. Low cost technology is essential for reducing financial burden on farmers and to increase production on sustainable manner.

An area with similar soil, climatic conditions and resource availability resulting in similar type of crops and cropping systems. Ex. Rice based cropping system, Ragi based cropping system, Wheat based cropping system, Cotton based cropping system etc.

Efficient cropping zone: An analysis of productivity efficiency of crop was made by Kanwar (1972) using relative yield index (RYI) and relative spread index (RSI).

A zone where both yield and spread indices are maximum that is above 90 per cent is called most efficient and in case of indices below 90 is the least efficient zone of a crop.

Horticultural crops include the fruit crops, vegetables, spices, plantation crops, medicinal plants, aromatic plants, commercial flower crops and ornamental plants.

Knowledge on the methods by which these reproduce is of primary importance from the standpoint of plant breeding. Besides, their annual or perennial nature also decides the methods of breeding to be adopted to get desired improvement.

Two divisions of methods of reproduction commonly recognized are:

1. Asexual i.e. vegetative parts of the plants are utilized to produce new individuals.

2. Sexual i.e. gametic fusion, the resultant zygote develops into seed which is utilized to produce new individual.

This group can be further placed in several sub divisions according to the mode of pollination. They are

a. Naturally self pollinated crop - (e.g. tomato, pepper, brinjal) wherein cross pollination occurs less than 4 % only.

b. Often cross pollinated crop- (e.g. chillies, bhendi) wherein though self pollination is more frequent, cross- pollination may occur so frequently that some methods of preventing cross pollination between varieties and strains of different genotypic constitution must be followed throughout the breeding programme.
Common breeding methods can be applied to the above two groups, however, the parents chosen for breeding under often cross pollinated crop need to be selfed for few generations to select desirable, homozygous lines.

TROPICAL AND SUBTROPICAL FRUITS

2.1 Mango
 

Mango is considered to be an allopolyploid. The chromosome number is 2n =40. The polyembryonic seedlings of cv. Vellaikolumban, earlier reported to be 2n= 80 was later shown to be a diploid. In Canary Island, a putative tetraploid viz Gomera-1 has been identified.

Floral biology

Flower starts opening early in the morning from 4-7 a.m. and maximum flowers open between 9.30-10.30 a.m. and complete 11 a.m. Dehiscence of anthers takes place at 11.30 a.m. and it continues up to 3.45 p.m. The pollen grains are oval, or triangular or oblong. Stigma becomes receptive even 18 hours before flower opening. Mode of pollination is entomophily; nectar is present to attract the insects.

The flowering duration is usually of short i.e. 2 to 3 weeks. The mango inflorescence or panicle bears mainly two types of flowers - male and perfect. The number of flowers per panicle varies between 1000 to 6000 depending upon the variety and climatic factors. The percentage of perfect flowers varies between 0.74 per cent in Rumani, 16.41 to 55.7 per cent in Neelum and up to 69.8 per cent in Langra.

3.1 Tomato

Tomato (Lycopersicon esculentum) is an important vegetable crop. Its 2n= 24.

Floral biology

Flowers are borne in small forked racemose cyme. Anthesis starts at 6.30 a.m. and continues up to 11.00 a.m. Anther dehiscence is longitudinal. It occurs 1-2 days after opening of corolla. The stamen sheds its pollen when the style grows up through anther tube, thus self-pollination occurs. When the stigma protrudes above the anther tube, chances of cross pollination through bees increases. The optimum temperature for pollination is around 21°C.

A

Abdomen: Area between the keel and the pubic (hip) bones.

Abdominal capacity: The distance between the two public bones (width) and between the pubic bones and the tip of the keel (depth).

Addled: An egg where the contents are decomposing.

Air cell: The air space between the two shell membranes, usually at the large end of the egg.

Albumen: The white of an egg.

Alektorophobia: The fear of chickens.

Allantois: A sac connected to the embryo’s abdomen and involved in embryo respiration.

Amnion: A sac surrounding the embry filled with amniotic fluid which protects the developing embryo from shock and provides a medium for the develop embryo to exercise their muscles.

Antibody: A natural substance in the blood that recognizes and destroys foreign invaders and that causes an immune response to vaccination or infection.

Anticoccidial: An anticoccidial drug used to treat or prevent coccidiosis.

Antigen: A foreign protein in the blood that differs from nautral body proteins and, as a result, stimulates the natural production of antibodies.

Artificial insemination: The introduction of semen into the female oviduct by methods other than by natural mating.

As hatched: Description of a group of chicks that have not been sorted.

Taxonomic classification of avian species is beyond the scope of this booklet. However, since the preliminary knowledge of bird species for students of avian medicine class is of interest, the following description of most common pet and wild birds are being attempted for their benefit.

GALLINEFORMES: This order includes domestic chicken, turkey, pheasants, peafowl, grouse, quail, guinea fowl, guans and curassows.

COLUMBIFORMES: Includes pigeons and doves.

PSITTACIFORMES: Includes parrots, which have strongly hooked maxilla with a flexible attachment to the skull. They also have dexterous zygodactyl feet (two digits point forward and two backwards). The order includes.

Introduction

Anatomy of the immune system in birds differs from that in mammals. Immune cells are present in primary lymphoid organs (PLO) and secondary lymphoid organs (SLO). In birds, thymus and bursa of Fabricius (cloacal bursa) are primary lymphoid organs. Secondary lymphoid organs include the spleen, bone marrow, Harderian gland, aggregates of lymphoid tissue in various organs; i.e. in the gut called gut-associated lymphoid tissue (GALT); in bronchi called bronchial- associated lymphoid tissue (BALT). SLO contains aggregates of lymphocytes and antigen presenting cells. Birds do not have lymph nodes.

In PLO, the lymphoid cells are processed for differentiation and maturation. T lymphocytes differentiate and mature in the thymus, whereas B lymphocytes mature in bursa of Fabricius. Functional lymphocytes move from PLO to SLO. Like mammals, birds defend the body against pathogens through innate immunity (non-adaptive immunity) and adaptive or acquired immunity. Under innate immunity system, physical barriers present in birds play their important role preventing the entry of pathogens into the body. Physical barriers are feathers, skin, aggregates of lymphoid cells in various organs and ciliary defence in the respiratory system. Phagocytosis is first defence for pathogens entering the body, evading the physical barriers. Phagocytic cells include mainly heterophils and macrophages. Natural killer cells (NK cells), thrombocytes and complement also help in innate immunity.

Adaptive immunity is a particular defence which develops when the innate immunity is inadequate to impart protection. Adaptive immunity is antigen specific. T cell, B cell and macrophages play a major role in adaptive immunity. Adaptive immunity is brought about by antibodies (humoral immunity) or also by cells (cell-mediated).

Introduction

Avian salmonellosis is the term used to describe a large group of acute or chronic diseases caused by one or more members of the bacterial genus Salmonella, which is a member of the large family Enterobacteriaceae. Domestic poultry is known to constitute the largest single reservoir of Salmonella organism existing in nature. They include host specific and nonmotile members of the genus S. enterica subspp. enterica pullorum/gallinarum. If the infection of poultry is due to other Salmonella organisms other than Salmonella enteric subspp. enterica gallinarum/pullorum, the infection is then referred to as paratyphoid.

Introduction

Disease caused by motile Salmonella species in birds is called “Paratyphoid infections”. Paratyphoid infections are present in all parts of the world.

Etiology

Salmonella enterica includes six subspecies. Only one of that subspecies; S. enteric subspecies enterica includes more than 2500 motile serotypes.

S. enterica subspecies arizonae (Salmonella arizonae), the cause of an acute septicemic disease in young turkey poults.

Host Range

S. arizonae are reported from a variety of avian, mammalian and reptile species. Among avian in addition to turkeys, it has been reported in chicks, ducklings, psittacines and passerines.

Transmission

Organism is present in the intestinal tract of infected birds. Hence transmission is similar to motile salmonellae. Many workers have reported transmission in turkeys through infected ovaries. Wild birds, reptiles, rats and mice are reported as the common reservoir of the organism. The organism is also transmitted by direct contact and through contaminated feed and water.

Introduction

From avian species alone approximately 20 mycoplasma serotypes have been isolated and characterised. Out of them, three serotypes (M. gallisepticum, M. meleagridis and M. synoviae) are most typical and pathogenic. A serotype M. iowae causes low hatchability in turkeys. Mycoplasmas are bacteria that lack cell wall and belong to the class Mollicutes. Although they have been considered extracellular agents, scientists admit nowadays that some of them are obligatory intracellular microorganisms, whereas all other mycoplasmas are considered facultative intracellular organisms

Introduction

Escherichia coli (E. coli) infections are responsible for significant economic losses to the poultry industry, worldwide. Disease conditions caused purely or partly by E. coli are as under:

Disease is worldwide in distribution

Etiology

Pasteurella multocida, a gram negative non spore forming, non motile rods which stain bipolar.

Epizootiology

Most species of birds are infected. Turkeys are more susceptible than chickens, and older chickens are more vulnerable than young chickens. Geese and ducks of all ages are highly susceptible to fowl cholera. Survivors of fowl cholera outbreaks become carriers and are the reservoir of infection. P. multocida isolates of pigs are pathogenic to fowls. Spread of P. multocida in a flock is by feed and water contaminated with excretions. Crates, feed bags and utensils serve as a mechanical carrier of the organism.

(New duck disease, Duck septicemia, Anatipestifer syndrome, Infectious Serositis, the disease in goose is called “goose influenza”)

Etiology

The disease was first described in ducks from 3 farms in Long Island, N.Y. in 1932. R. anatipestifer (Pasteurella anatipestifer) is a gram negative, non- motile, non-spore-forming rod occurring singly, in pairs and occasionally in chains. To date, 19 serotypes are reported.

Natural and experimental hosts: primarily a disease of domestic ducks. Outbreaks also reported in turkeys. Bacteria have been isolated from pheasants, chickens, guinea fowl, quail, partridge and other waterfowl.

Etiology

Erysipelothrix rhusiopathiae.

Disease Occurrence

The disease is worldwide in distribution.

Host Range

Outbreaks of significant economic loss are in turkeys. Occasional outbreaks have been reported in pheasants, ducks, geese, guinea fowl, chukars, grebes and emus. Erysipelas also occurs in swine, sheep, sea mammals, fish and many wild animals. In humans (fish handlers, butchers, kitchen workers, turkeygrowers and veterinarians) it causes a localised inflammation called “erysipeloid”.

Etiology

Yersinia pseudotuberculosis, non-motile at 37 C but motile at room temperature around 25 C. It is a disease of turkeys, ducks, geese, chickens, guinea fowl, and companion birds and free flying birds. It has also been reported in many species of mammals including man. In man, it causes symptoms of appendicitis. The disease has been reported in many countries. Body excretions of diseased birds or mammals that contaminate soil, food and water are the important factor in the transmission of the disease. The disease usually occurs as an acute septicemia of short duration, followed by a chronic focal infection.

Etiology

There are 18 species in genus Campylobacter. Campylobacter species in poultry include C. jejuni, C. coli and C. lari. The most predominant species is C. jejuni.

Epizootiology

The infection has been reported in chicken, but the organisms have been isolated from ducks, turkeys, black birds, sparrow and pigeons.

Transmission

Possibly through faeces, as organisms are in the intestinal tract. Egg transmission of bacteria on or in the egg through hatchery is strongly suggested.

Causative Organism: Borrelia anserina

B. anserina and B. burgdorferi (borreliosis of humans) share common flagellar antigens, suggesting their close relationship. B. burgdorferi infect both mammals and birds (mallards and bobwhite quail). Geese, turkeys, chickens, ducks, pheasants and canaries are natural hosts of B. anserina. All age birds are susceptible.

Transmission

Infection is mainly transmitted by a soft tick- Argus persicus. Transmission is also by ingestion of blood, excreta or tissues from infected or dead birds, through contaminated feed or water. Use of syringe and needles on multiple birds also makes transmission possible.

Etiology

Intestinal spirochetes colonise the large intestine of avian, swine and humans.

Family spirochaetacae has six genera, of which Borrelia, Serpulina and Treponema have species pathogenic for animals. Avian intestinal spirochetes are grouped in four: Serpulina hyodysenteriae, S. intermedius, S. pilosicoli (Angullina coli) and an unnamed group.

Chicken S. hyodysenteriae is different from porcine one. S. hyodysentriae, Angullina coli and unclassified groups are present in the USA, whereas S.intermedius is in Europe and Australia.

Avian intestinal spirochetes are gram negative, stain brown with silver impregnation techniques and blue in Wright-Giemsa stain. They can be divided in 3 pathotypes 1) severely pathogenic 2) Mildly to moderate pathogenic and 3) subclinical or apathogenic.

In avian species following diseases are caused by Clostridium bacteria.

1. Ulcerative enteritis
2. Necrotic enteritis
3. Gangrenous Dermatitis
4. Botulism
5. Yolk sac infections.

Clostridia infections are not common in birds and are not a significant source of infection for man and animals.

Etiology

Avibacter paragallinarum Serotype A, B and C. Based on hemagglutinin serotyping, three serotypes (A, B and C) have been recognized.

Epizootiology

The chicken is the natural host although the disease has occasionally been diagnosed in pheasants. All ages of chicken are susceptible but birds up to 10 weeks are less vulnerable.

1. The chronic or healthy carrier birds serve as source of infection. Infection within farm occurs by contact with drinking water or feed contaminated by nasal discharge from sick/carrier chickens. To farms situated at a distance, infection is through air borne transmission.
2. The disease occurs more in cold and wet conditions. The more severe disease occurs when other respiratory diseases are prevalent at the farm.

Etiology

Ornithobacteriun rhinotracheale, bacteria, under phylum Cytophaga- Flavobacterium-Bacteroids. It is Gram negative non-motile, non-sporulating pleomorphic rod shaped bacteria. 18 serotypes Athrough R have been identified. Serotype A is prevalent in chicken and turkeys.

Disease occurrence

The disease is worldwide in distribution.

An important disease in Turkey producing areas of the world. It is reported an opportunistic pathogen to human. Bactria grows in ciliated epithelium of vertebrates.

Etiology

Bordetella avium, a small Gram-negative bacillus, which is motile and aerobic. Differences in pathogenicity among strains exist.

Transmission

Recovered birds serve as carriers. Turkey coryza is highly contagious, and transmission occurs directly through close contact and contaminated feed and water.

Etiology

Genus Mycobacterium contains many pathogenic species that can cause disease in birds (M. avium, M. tuberculosis, M. genavenes, M. gordonae). Within M. avium, organisms are divided into four sub species. M. avium sp avium, M.avium sp silvaticum, M. avium sp homnissuis and M. avium sp paratuberculosis. Mycobacterium avium sp avium - has wide host spectrum; poultry, pigeons, raptors, ratites and wild birds. M. genavense- affects Psittacines and passarines. M. tuberculosis- psittacines and other cage birds, and wild birds in captivity. M.bovis- Psittacines and others.

Under natural conditions, M. avium sp avium does not cause severe disease in mammals except in rabbit and pig. Majority of mycobacteriosis in pigs is by M. avium sp avium. In cattle and other mammal infection by M. avium remain localized and is known to give positive reaction to mammalian tuberculin. The disease in caged and wild birds in captivity is common with M. tuberculosis, because of its close contact with humans. Tuberculosis is a serious problem in zoological gardens. M. avium is being isolated in increasing number of immunocompromized human patients.

Chlamydial organisms are spherical 0.2-1.5 um in diameter. They can be stained and seen in the light microscope, but they grow only in living cells. Chlamydial organisms infect mammals and birds causing various disease syndromes. Chlamydiacae family has one genus; Chlamydia. C. trachomatis, C. suis and C. muridarum. They cause disease in man, swine and mice. C. psittaci, C. pneumonia, C. felis, C. Caviae, and C. abortus. cause disease in man, birds and animals. Species can be differentiated on their growth characters inside the host cell.

Etiology

Mostly associated with bacterial infections. Salmonella sp, Escherichia coli, streptococcus fecalis, Staphylococcus aureus, Clostridia sp. (C. pefringens), Pseudomonas and Proteus spp. have been isolated from cases of omphalitis. Chilling, overheating or stress during transport may predispose for the condition.

Inflammation of yolk sac, characterized by infected unhealed navels in young birds.

The diseases caused by Staphylococci are found in all avian species and reported through out the world.

Etiology

There are more than 45 species and 25 subspecies in the genus Staphylococcus.

S. aureus is the most common species of birds causing disease. Staphylococci are Gram - positive, coccoid and when grown on solid medium, bacteria form grape like clusters.

Streptococcosis has been reported from avian species worldwide. Bacteria produce acute septicemic and chronic infection. Streptococcosis has wide range of host ranging from many avian species including wild birds.

Etiology

Streptococci are Gram-positive, non-spore forming, non-motile facultative anaerobes. They occur singly, in pairs or short chains. S. zoozooepidemicus is species associated with disease in avian species. Other species of streptococcus (S. bovis, S. dysgalactiae, S. pleomorphus) have occasionally been isolated from birds.

Enterococcus sp. belongs to Lancefield antigenic serogroup D. Enterococcus is considered normal flora of the chicken intestine.

Etiology

Enterococci bacteria are Gram positive, spherical seen in singles, pairs or chain. Enterococuus sp. Causing disease in birds include E. faecalis, E. faecium, E. durans, E. avium, E. hirae and E. cecorum. E. faecalis is most common isolate from birds.

ND is a viral disease of poultry, wild and cage birds characterized by marked variation in morbidity, mortality, signs and lesions. Reported in 235 species of birds.

A disease of primary importance and concern worldwide which causes continuous massive economic loss. It is a reportable disease in many countries of the world.

Occurrence

Species: All birds susceptible. Temporary conjunctivitis may develop in people who come in close contact with NDV for the first time.

Etiology

The subfamily Pneumovirinae includes two genera: Pneumoviruses and metapneumovirus. The later consists of both human and avian metapneumovirus (aMPV). aMPV produces turkey rhinotracheitis (TRT) in turkey and Swollen head syndrome (SHS) in chickens. aMPV has been detected in other species of birds, but the disease in those birds are not well defined.

Occurrence Species

A new disease of turkeys (in the UK since 1985) which is suspected to cause some lesser problems in chickens.

ILT is an acute viral disease of chickens, pheasants and peafowl characterized by marked dyspnea, coughing, gasping and expectoration of bloody exudate. The disease is worldwide.

Hosts

Chickens particularly susceptible; reported to occur in pheasants and peafowl.

Age Range

All ages susceptible but is most often found in adult (mature or nearly mature) commercial chicken layers.

IB is an acute, highly contagious, viral disease of chickens characterized by respiratory signs (gasping, sneezing, coughing, and nasal discharge), the severe renal disease associated with neurotropic strains, and a marked decrease in egg production. It is a serious cause of sub-optimal egg production and poor egg quality. This disease is worldwide in ditribution.

Hosts

Chickens only. Recently IBV has been detected in species other than chickens. The disease may be produced only in chickens, IBV may multiply in other species of birds and be a source of infection.

Etiology

IB is caused by the avian coronavirus; numerous strains of infectious bronchitis virus (IBV) exist because of high genetic diversity and cross protection between strains is not reliable.

This ‘virus’ is widespread in commercial flocks worldwide, but its taxonomic position is not determined. The disease is characterized by aplastic anaemia and generalized lymphoid atrophy with a concomitant immunosuppression. Consequently, infectious anaemia is frequently complicated by viral, bacterial, or fungal infections.

Occurrence

Chickens up to 3 weeks of age are most susceptible.

Adenoviruses have been found in several species of birds and animals. There are at least 12 serotypes of chicken adenoviruses. The chicken adenoviruses are host specific, meaning they will not infect other animal species. Avian adenoviruses are divided into three major groups. Members of each type may share group antigens, but there is no common antigen shared between types.

Quail bronchitis (QB) is caused by group I (aviadenovirus). QB is an acute respiratory disease of bobwhite quail, occasionally with high mortality. Disease has sporadic occurrence many parts of the world. QB virus is closely related to the prototype CELO (chick embryo lethal orphan) virus, which is cause of high mortality in chicks.

IBH is an adenovirus infection of young chickens characterized by sudden onset and sharply increased mortality, short course, anaemia, and hepatitis often accompanied by intranuclear inclusion bodies. It is described in Canada, USA and many other countries.

Etiology

Group 1 adenovirus. First reported in Pakistan in 1987, where it caused a devastating effect on broiler industry. It has spread to all continents.

EDS 76 is an infectious disease of laying hens caused by hemagglutinating adenovirus and characterized by failure to achieve production targets or by the production of thin-shelled or shell-less eggs in otherwise healthy birds.

This important disease caused loss of egg production for several years - vaccination introduced the disease and a new vaccine virtually eradicated it.

(Tenosynovitis; Ruptured gastrocnemius tendon; Reovirus infection)

Viral arthritis is a reovirus infection primarily of broilers characterized by arthritis and tenosynovitis (primarily of the tarsus and metatarsus, the digital flexor and tarsometatarsal extensor tendons) and, occasionally, by rupture of the gastrocnemius tendon(s) resulting in lameness and condemnations at slaughter. The disease is reported worldwide.

Fowl pox is a slow spreading viral disease of chickens, turkeys and other birds characterized by cutaneous lesions on the un-feathered skin of the head, neck, legs and feet and/or by diphtheritic lesions in the upper digestive and respiratory tract. The disease is worldwide in distribution.

Occurrence

Among poultry chicken and turkey are more susceptible. Other birds include pigeons, canaries, psittacines and wild birds. Fowl pox has been reported from more than 200 species of birds. The incidence is severe in multiple age groups and intensive poultry farming areas.