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Avian influenza also called Bird flu virus
Avian influenza is an infection caused by avian (bird) influenza (flu) A viruses. These influenza A viruses occur naturally among birds. Wild birds worldwide get flu A infections in their intestines, but usually do not get sick from flu infections. However, avian influenza is very contagious among birds and some of these viruses can make certain domesticated bird species, including chickens, ducks, and turkeys, very sick and kill them.

Infected birds can shed influenza virus in their saliva, nasal secretions, and feces. Susceptible birds become infected when they have contact with contaminated secretions or excretions or with surfaces that are contaminated with secretions or excretions from infected birds. Domesticated birds may become infected with avian influenza virus through direct contact with infected waterfowl or other infected poultry, or through contact with surfaces (such as dirt or cages) or materials (such as water or feed) that have been contaminated with the virus.

Infection with avian influenza viruses in domestic poultry causes two main forms of disease that are distinguished by low and high extremes of virulence. The "low pathogenic" form may go undetected and usually causes only mild symptoms (such as ruffled feathers and a drop in egg production). However, the highly pathogenic form spreads more rapidly through flocks of poultry. This form may cause disease that affects multiple internal organs and has a mortality rate that can reach 90-100% often within 48 hours.
Blackhead (Histomoniasis, Enterohepatitis)
A protozoan parasite of turkeys, and occasionally chickens, pheasants and game birds that acts together with facultative bacteria to produce the condition of Blackhead. The parasite is ingested in the ova of Heterakis worms or as larvae in earthworms. The life history of the Heterakisworms is similar to that of the common roundworm. The eggs are produced in the ceca and pass in the feces. They reach the infective form in about two weeks. In cool weather, this may take longer. The eggs are very resistant to environmental conditions and will remain viable for long periods. Since the worm itself produces no observable damage and the eggs live for long periods, it is advisable and necessary to keep chickens and turkeys separated to prevent spread of blackhead. This disease affects the large intestine, then attacks the liver.
Signs

  • Depression.
  • Inappetance.
  • Poor growth.
  • Birds develop foamy yellow diarrhoea and sit huddled up ( Any sulphur coloured foamy droppings should be considered as blackhead, even if the bird is not showing any other signs of the disease)
  • Cyanosis of head.
  • Blood in faeces (chickens).
  • Progressive depression and emaciation.
  • The birds can be so ill, that their wattle and comb goes blue (thus the name blackhead)

Prevention

Good sanitation, avoid mixing species, concrete floors. Regular worming to help control the intermediate hosts.
Botulism
A condition of chickens, turkeys, ducks and other waterfowl occurring worldwide and caused by a bacterial toxin produced by Clostridium botulinum mainly types A / C. The toxin is produced in decaying animal (usually carcases) and plant waste, and toxin-containing material (pond-mud, carcases, maggots) is consumed by the birds.
Signs
* Weakness
* Progressive flaccid paralysis of the legs, wings and neck
( when neck is affected the head hangs limp, referred to as "limberneck" )
* Loose feathers that are pulled out easily.
* Dull partly closed eyes.
Prevention
Preventing access to toxin, suspect food and stagnant ponds, especially in hot weather. The single most important measure is careful pick-up and removal of all dead birds on a daily basis.
Treatment
Remove source of toxin, supportive treatment if justifiable, antibiotics
Newcastle Disease
There are three forms of Newcastle disease -- mildly pathogenic (lentogenic), moderately pathogenic (mesogenic) and highly pathogenic (velogenic). Newcastle disease is characterized by a sudden onset of clinical signs which include hoarse chirps (in chicks), watery discharge from nostrils, labored breathing (gasping), facial swelling, paralysis, trembling, and twisting of the neck (sign of central nervous system involvement). Mortality ranges from 10 to 80 percent depending on the pathogenicity. In adult laying birds, symptoms can include decreased feed and water consumption and a dramatic drop in egg production
Transmission
The Newcastle virus can be transmitted short distances by the airborne route or introduced on contaminated shoes, caretakers, feed deliverers, visitors, tires, dirty equipment, feed sacks, crates, and wild birds. Newcastle virus can be passed in the egg, but Newcastle-infected embryos die before hatching. In live birds, the virus is shed in body fluids, secretions, excreta, and breath.
Treatment
There is no specific treatment for Newcastle disease. Antibiotics can be given for 3-5 days to prevent secondary bacterial infections (particularly E. coli ). For chicks, increasing the brooding temperature 5°F may help reduce losses.
Prevention
Prevention programs should include vaccination, good sanitation, and implementation of a comprehensive biosecurity program.
Fowl Pox
Chicken pox (not to be confused with chicken pox in humans; the human disease does not affect poultry and vice versa), sore head, avian diphtheria, bird pox. Most poultry chickens, turkeys, pheasants, quail, ducks, psittacine, and ratites -- of all ages are susceptible.
Signs
There are two forms of fowl pox. The dry form is characterized by raised, wart-like lesions on unfeathered areas (head, legs, vent, etc.). The lesions heal in about 2 weeks. If the scab is removed before healing is complete, the surface beneath is raw and bleeding. Unthriftiness and retarded growth are typical symptoms of fowl pox. In laying hens, infection results in a transient decline in egg production. In the wet form there are canker-like lesions in the mouth, pharynx, larynx, and trachea. The wet form may cause respiratory distress by obstructing the upper air passages. Chickens may be affected with either or both forms of fowl pox at one time.
Treatment
No treatment is available. However, fowl pox is relatively slow-spreading. Thus, it is possible to vaccinate to stop an outbreak. The wing-web vaccination method is used for chickens and the thigh-stick method for turkeys older than 8 weeks.
Prevention
Fowl pox outbreaks in poultry confined to houses can be controlled by spraying to kill mosquitos. However, if fowl pox is endemic in the area, vaccination is recommended. Do not vaccinate unless the disease becomes a problem on a farm or in the area. Refer to the publication PS-36 (Vaccination of Small Poultry Flocks) for more information on fowl pox vaccinations