Diseases of Commercial Poultry-Which farmer can identify

Disease is impairment from normal function of body organs or any part of body. Many factors like nutritional deficiency, injury, toxicity, stress, infectious agent, etc can cause disease. The outbreak of disease and its severity depends on factors like numbers and type of virulent agent, its route of entry and defense status of bird, also nutritional, genetic ability, environment, etc play important role. The infectious agent can be categorized as below.


Avian Salmonellosis

Its caused by one or many members of Salomonella bacteria.Most harmful being S.pullorum and S.gallinarum

S.pullorum infects mainly through hatching eggs,cannibalism,egg eating,through wound and contaminated feed and water.

Chicks hatched from infected eggs are moribound,sleepy,show weekness,inappetence,shrill cry while defecating,have chalky white diarrhoea,show exhaustion,huddling,sometimes respiratory distress,retarded growth and poor feathering.Usually heavy mortality during first few weeks.

Avian pasteurellosis or Fowl cholera

Usually appears when new flock is added to present flock.Contaminant like crates,feed bags,infected pullets,also insects acts as vector.In flock transmission is  by contaminated feed , water and by nasal and oral discharges.

Birds show temp.anorexia,mucous discharge from mouth,green diarrhoea,cynosis of comb and wattles,torticollis,pink or red shanks,etc.In chronic cases swelling of wattles,sinuses and tracheal rales is seen.

Infectious coryza

The disease is mainly of multi age group farms and carrier birds are main source of infection.Outbreak is fast and seen within 1-3 days.

Sinuses and nasal passage has serous to mucoid discharge,respiratory rales are seen,catarrhal conjunctivitis and subcutaneous edema of face and wattles,diarrhoea,reluctant to eat,drop in production and foul odour is common.There is low mortality but high morbidity.

Avian mycoplasmosis

Its quite common in poultry and spreads by contact,air borne,dust and dropping,contaminated equipments,etc.Spread of disease can take 1-3wks

Its characterized by tracheal rales,nasal discharge,sneezing,loss of body weight,decrease feed intake and production,foaming of eye secreations,swelling of sinuses,loss of body weight.Mortality is high in young pullets due to complication with secondary infection with e.coli and viral disease,which leads to chronic respiratory disease.

Gangrenous dermatitis or wing-rot

Its acute disease .Injury,Clostridium bacteria presence and immune suppression enhance chances of outbreak.It occurs spontaneously around 6-12 wks age.It usually starts with small pimple on skin and soon progresses to involve larger area.Birds with wing-rot have moist raw dark area where underline muscle is exposed.The breast,wing,rump,abdomen area is commonly involved.Blood tinged jelly like fluid may be found underneath skin.

Escherichia coli

This include infections like Colibacillosis,peritonitis,salphingitis,omphalitis,air saculitis,etc.

This is most common bacterial infection and the organism is normal inhabitants of gastrointestinal tract.Most important route is fecal contamination of feed,water and litter as well as dust.In commercial farms mostly seen  due to stress conditions.

Mushy chick disease

When e.coli infects yolk sac there is edema and infection of yolk sac.Infected chicks die  with-in 1st wk of hatch.Low brooding temp.and starvation increases omphalitis cases.

Air saculitis

Its characterized by air sac infection along with pericarditis and perihepatitis.Inhalation of infected dust and high ammonia level increases reproductive form of disease.It causes severe economic losses due to mortality and condemnation of carcass.


Its sequalae to e.coli septicemia,usually associated with myocarditis and perihepatitis.


Its characterized by granuloma of liver,ceca.duodenum and mesentry but not spleen.


Newcastle disease/Raniket

Classified as velogenic,mesogenic and lentogenic depending on virulence.Mostly air borne diseases.Seen in five clinical forms.

Doyle’s form-Its acute and birds die without showing any symptoms and sign in 2-4 days,causes by velogenic strains and mortality about 90%.Greenish diarrhoea,tremers of muscles,torticollis,listlessness and paralysis of wing and legs is seen.

Beach,s form-very acute and spreads very fast.Birds show respiratory symptoms like dyspnoea,sneezing,gasping,inappetence,drop in production,paralysis seen and high mortality in immature birds.

Beaudette,s form-Acute respiratory disease of adult birds characterized by coughing but rarely  gasping,feed intake and production decreases and internal quality of eggs is affected and is caused by mesogenic strains.Mortality is seen in young birds but adult birds usually won’t die.

Hitchner’s form-mild form and may go unnoticed in adults its caused by lentogenic strains and respiratory signs visible only on close observations.If complicated with bacterial infection mortality is high

Asymptomatic enteric form-not much clinic signs seen

Avian encephalomyelitis

Mainly egg borne can also spread due to direct or indirect contact.Usually chicks between 1-2 wks show dullness,ataxia,sitting on hocks,fine tremor of head and neck.Mortality is mainly due to birds not being able to eat and drink.In adults only drop in production no nervous signs.

Egg drop syndrome

Chicken though is not natural host and in commercial conditions outbreak is rare.When there is horizontal transmission, there is loss of color in pigmented eggs and then production of thin shell,soft shelled and shell-less eggs.The thin shelled eggs have paper like texture or granular roughening on one side of egg.

Avian pox

Mainly transmission of virus is by injury or broken skin.

Cutaneous form-lesion are seen mainly on wattles and comb as local epithelial hyperplasia followed by nodule formation which is wart like.These nodules became rough and grey or brown in color.Also seen on legs and feet.This is followed by scab formation and desquammation of epithelial layers.When scab falls off, a smooth scar is left.

Diphtheritic form-there is white opaque nodules on mucous membrane which enlarges and forms like a plug.Mostly seen plugging trachea.It might extend at sinuses,pharynx.larynx and esophagus.

Infectious bursal disease/Gumboro

This being highly contagious is most feared.Water,feed and dropping spread disease.Its very fast spreading.Its also self limiting.Mortality peaks on 4-5th days and receeds 7-10 days post attack.There is white diarrohoea,anorexia,pecking of vent.depression,dehydration,ruffled feathers.trembling,tucked-up appearance and heavy mortality.Usually seen 3rd-8th wk age.


Mechanical means like equipments and litter spreads disease,also airborne,ingestion,intraocular,etc.

There is nasal discharge,moist tracheal rales,gasping,blood stained mucus from mouth in severe cases,watery eyes,conjunctivitis,unthriftyness,reduced egg production.Mostly adults recovers from mild form of disease in 2 wks.

Avian infectious bronchitis

Chicken is the main host and disease is spread mainly by air.Spreads fast and young birds show prominent respiratory signs like gasping,sneezing,tracheal rales and nasal discharge.Chicks huddle under the brooder.Sinus swelling might be seen.Pullets show retarded growth and feed consumption.Older birds show decrease in egg production.The external and internal quality egg is affected.The egg shell is soft,misshapen or rough.Albumin is watery,yolk separates from albumin or albumin sticks to shell membrane.Serous exudates in nasal passage and sinuses is seen.

Marek’s disease and Lymphoid leucosis

They are virus induced neoplastic disease.Marek’s is transmitted by direct or indirect contact between birds,affected feather follicles,poultry house dust and carrier birds.Its takes 4 wks to show symptoms.

At start there is asymmetric paralysis and later complete paralysis of one or both legs.If wing is involved then its characterized by dropping of wing,there can be drooping of neck,paralysis and dilation of crop,if sciatic nerve is involved then sportsman posture i.e one leg stretched forward one leg backwards.In acute cases severe depression is seen.Birds are emaciated and dehydrated.When eyes are involved causes pearl like appearance of eye,opacity of iris and also swelling of feather follicles and sloughing of feathers is seen.

Lymphoid leucosis is seen usually after lay starts.Clinically not seen before 15 wks and takes 14-30wks for symptoms to develop.Incidence is max. at around sexual maturity and pale,cyanotic comb,emaciation,inappetence is seen.Abdomen is enlarged and liver enlargesand can be felt on palpation.

Chicken Anemia Virus

Its acute disease usually of young chicks and is characterized by depression,anorexia,anemia,palesness,loss of weight,hemorrhages and sudden rise in mortality.It depresses immune-system.Its can spread vertically and horizontally.Infected birds shed virus upto 5 wks.Horizontal spread is through feed and air.


It has highly variable clinical signs and outbreak pattern.Respiratory signs are most common,depression,high to mild drop in production.In severe cases green diarrhoea,cynosis of comb and wattles,also edema of head,nasal discharge,discoloration of shank and feet seen.


Important disease as it causes great financial losses.If mild attack it causes weight loss,reduced feed intake.Severe outbreak leads to heavy mortality.Its transmitted through ingestion of sporulated oocysts.Farm labour’s shoes,hand,clothing serves source to transmit oocysts.Its rare to see disease in less than 11 day old bird.Affected birds are pale,dull.sleepy while standing,show ruffled feathers,birds tends to stand in corner,retracted head,initial dark brown later bloody droppings and emaciation.


Aspergillosis-It produces toxin which are hemotoxic,neurotoxic and histotoxic.Infected hatcher and incubator are main source of contamination.Spores in air transmits infection.Birds show dyspnoea,gasping.polypnoea,emaciation,increase thirst and disease usually gets complicated by viral respiratory diseases.

Favus-symptoms are white spots on comb,wattles,also causes loss of feather and skin lesions.it spreads by contact.

Thrush-causes retarded growth,listlessness and reffled feathers,necrotic spots in crop mucosa,thickening of mucosa and also white raised ulcers.These lesions may extent to proventriculus

Mycotoxins-there is depressed growth,inappetence,mortality,drop in egg weight and production.It impairs immune system making birds prone secondary infections.



Birds infested with external parasites show scratching and preening also there will be drop in production.Area like feathers around vent,legs,wing and neck reveals parasites.

Internal-Pinworm,Roundworm,Tapeworm.All causes drop in production and loss of body weight,increase feed intake.

Other disease conditions

Egg bound-it’s a condition where egg is lodged in cloaca but is not laid.Its caused due to inflammation of oviduct or partial paralysis of oviduct muscles,also if egg is over sized.

Cage layer fatigue-its characterized by inability of birds to stand and there is marked fragility of bones.Birds recover when put on deep litter.

Bumble foot-its localized infection of foot that causes bulbous swelling of foot pad and surrounding tissues.May be in one or both foot.

Hemarrhagic syndrome-characterized by hemorrhages in muscles,internal organs and aplastic bone marrow.Ruffled feathers,huddling and sometimes diarrhoea.

Fatty liver syndrome-its characterized by fat deposits,fatty liver and drop in production.High energy ration with low energy usage and due to stress of high egg production.Birds have increased body weight and birds in good health die.

Poison and Toxin

Mainly caused by injudicious use of chemotherapeutic agents,disinfectants,insecticides,etc

 Autointoxication-its because of absorption of waste metabolites or due to decomposition in GI tract.High fiber diets results in impaction of crop,chilling leads to vent pasting.

Chemotherapeutic drugs-Sulphonamides causes blood dyscariasis,kidney and liver dysfunction.Toxic level leads to ruffled feathers,paleness,depression,poor weight gain and hemorrhagic syndrome.

Nitrofurans-toxic level causes depression,hyperexcitability

Nicarbazin-decreases production,reduces egg size,mottling of yolk,reduction in shell quality and hatchability.

Monensin-drowsiness,thirst,panting,flaccid paralysis.


 Cresol-Toxic level causes depression,huddling,rales,gasping,wheezing,extension of head and neck.

Potassium permanganate-severe cauterization of crop wall and hemorrhages in tissues in contact.

Quaternary ammonium compound-reluctance to drink,restlessness,foamy ocular discharge,nasal discharge,facial swelling,ataxia,convulsion and death


Copper sulphate-depression,weakness,convulsion.

Mercury compound-incordinaion of legs,weakness followed by prostration.

Nitrates-nitrates of K and Na are toxic.They cause thirst,anorexia,vomition,diarrhoea,cyanosis of comb,wattle and skin.

Sodium bicarbonate-weakness,increased water intake,watery dropping,nephritis and gout.

Sodium chloride-inappetance,somnolence,thirst,dysponea,convulsion,nephritis,myocardial hemorrhage,ascitis,subcutaneous edema.

Calcium-diarrhoea,intense thirst,paralysis with convulsion.


Chlorinated hydrocarbons-production drop 20-70% in a months time at levels 0.031-0.25%(DDT contaminated feed),hatchability reduced to zero at 0.125% DDT.Two wk old chicks with 0.05% DDT there is 100% mortality.Toxicity shows loss of weight,molting,ataxia,tremors,etc.

Organophosphorus compounds-like malathion causes drowsiness,ataxia,resting on hocks,paralysis and death.Also seen are signs like mucous hanging from beak,cynosis of head,blood tinged diarrhoea,birds are never hyperexcitable.

Parathion-most toxic increases salivation,lacrimation,gasping,muscular convulsion,ataxia and death.


Zinc phosphide-lethal dose is 7-15 mg/kg body wt in one hour birds show depression,ruffled feathers,diarrhoea,weekness,greenish diarrhoea,nervous signs and death.

 Note-Of late commercial layer poultry farming has become very technical and professional buisness.Farmers though has experience but usually follows trial and error  methods of learning or learns by losses.In poultry  there is not much time in outbreak and treatment as production and environment stress is maximum.Do take help of  good poultry consultant who knows and understands your birds professionally..He can guide you to minimize your losses and increase profits by decreasing cost of production of eggs.Prevention of disease is cash but treatment of disease is loan.

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