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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.

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.

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.

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.

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.

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.

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.

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.

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.

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

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.

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

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.

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.

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

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.

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

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.

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

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”.