infectious bursal diseaes

INFECTIOUS BURSAL DISEAES

GUMBORO DISEASE

DEFINITION

• DEFINITION IBD or Gumboro disease

• is an acute (sudden & severe), highly contagious viral infection of young chicken

Disease is of economic importance for 2 reasons:

• 1- it causes heavy mortality in the chickens of 3 weeks of age

• 2- It causes immunosuppression which leads to vaccination failure, E.coli infection, gangrenous dermatitis, & Inclusion body hepatitis

ETIOLOGY:

•is a member of the Birnaviridae family Virus is single shelled Non enveloped virion

Source Of Infection:

• Source Of Infection Infected houses remain infected for 122 days. Water, feed & dropping from infected pen remain infected for 52 days. Litter, mites & mealworms are infected up to 8 weeks.

• Mechanical vector such as wild birds, humans & vermion also transmit disease.

• Litter used as manure spread disease in particular area.

ROUTE OF INFECTION

• Feco oral route Contaminated feed and water.

• Virus found in high concentration in faeces & litter.

Pathogenesis

• Pathogenesis Infection 1- through mouth virus

present in macrophages2- lymphoid cells in caeca

Intestine liver blood viraemia virus goes to bursa

3- different tissues

PATHOGENESIS

• Field viruses exhibit different degrees of pathogenicity. White Leghorn exhibit the most sever reaction and has the highest mortality. Less in meat type Period of greatest susceptibility is between 3 to 6 weeks in broilers & 7-12 weeks in layer chicks. Susceptible chicken younger than 3 weeks do not exhibit clinical sign but have sub clinical infection that are economical important because the result can be sever Immunosuppression of the chicken.

Clinical Forms:

• I. Clinical IBD Birds above 3 weeks of age Temporary Immunosuppression High Mortality

• II. Sub Clinical IBD Birds below 3 weeks of age Permanent Immunosuppression No mortality due to IBD

MORTALITY PATTERN:

• In broiler Mortality between 3-6 weeks. 2- 5% mortality rarely goes beyond 10%. Peak on 2nd and 3rd day. No mortality on 5th day.

• In layer Mortality between 7-12 weeks of age. 30- 70 % mortality Mortality runs from 7 to 14 days. Two peak. AT 3rd and 4th day AT 7th and 8th day.

• In unvaccinated flock 90% mortality. In cage layer high mortality.

Clinical signs/ symptoms:

• Depression. • Inappetance. • Unsteady gait. • Huddling under equipment. • Vent pecking. • Diarrhoea with urates in mucus

Post-mortem lesions:

• Bursa of Fabricius - enlarged and haemorrhagic

Post-mortem lesions:

Haemorrhages in skeletal muscle (especially on thighs).

Post-mortem lesions

• Dehydration. • Swollen kidneys with urates.

Post-mortem lesions

• Haemorrhagic in the proventriculus -gizzard junction

Diagnosis:

• Diagnosis History Symptoms Postmortem findings Differential diagnosis from Coccidiosis, Ranikhet, Vitamin A deficiency, fatty liver , Kidney syndrome & hemorrhagic syndrome of muscles.

• Confirmatory diagnosisa) ELISA b) Isolation & identification of the causal

agent.

Treatment:

• Treatment No specific treatment. Supportive treatment is given to reduce dehydration & improve immunity like electrolytes, Vitamin E, & selenium.

Vaccines:

• Vaccines Two types of IBD vaccines-

• 1) IBD live vaccinethere are 4 types i) Mild vaccine ii) Standard intermediate vaccine iii) Intermediate plus vaccine iv) Hot vaccine

• 2) IBD killed vaccine

Vaccination Schedule: • Commercial broilers- 13 day Intermediate plus in drinking water. • Commercial layers- 14 & 28 day Standard intermediate plus in

drinking water & on 21 day Intermediate plus in drinking water.

• For breeder hen- Traditionally at prelay stage & midlay stage

IBD inactivated vaccine is given to get high antibody titer.

Resistance:

• Resistance Birds with maternal antibody are resistant due to high antibody titer.

• When antibody titer drops birds become susceptible.

• Very virulent strain can break the antibody barrier at young age.

• Older birds in which bursa is reduced in size & disappears are more resistant.

Immunity:

• 1) Immunity Active immunity a) Natural infection b) Vaccination with either live or killed vaccines.• 2) Passive immunity a) Antibody transmitted through yolk of the egg. b) Passive immunity protects chicks against early

infection. c) Half life of maternal antibody is between 3 & 5

days thus, if the antibody titer of the progeny is known, the time when chicks will become susceptible can be said

Control: • Control Thorough cleaning & disinfection of

the houses between the flocks & the practice “all in, all out” management.

• It delays infection & also provide time for vaccines to produce immunity.

• Hygienic & sanitary precautions. Formaldehyde & Iodophores are found to be effective disinfectants.

• Removal of vectors like mealworms & rats.• Proper vaccination of birds & flocks.