Infectious Bursal Disease by Dr zapadia

INFECTIOUS BURSAL DISEAES/GUMBORO DISEASE : 

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 : 

Disease is of economic importance for 2 reasons As it causes heavy mortality in the chickens of 3 weeks of age & older It causes immunosuppression which leads to vaccination failure, E.coli infection, gangrenous dermatitis, & Inclusion body hepatitis

INTRODUCTION. : 

INTRODUCTION. IBD is an acute highly contagious viral infection of young chicken. In 1962 first recognized and referred to as “avian nephrosis” Since first outbreak occurred in area of Gumbora in U.S.A.called Gumboro disease. In India first outbreaks in 1977-78.

ETIOLOGY : 

ETIOLOGY IBDV is a member of the Birnaviridae family Virus is single shelled Non enveloped virion. Has two segment (i) Segment A (large) VP2, VP3,VP4. (ii) Segment B (Small) VP1.

PATHO/SERO TYPES OF IBDV : 

PATHO/SERO TYPES OF IBDV Serotype-1. Sub types (i) Standard serotype –1 Moderate mortality and Immunosuppression. (ii) Variant serotype-1 No mortality and high Immunosuppression. Found in U.S.A. (iii) Very virulent serotype-1 High mortality and high Immunosuppression. Found in Asia, Europe. Serptype-2. Found only in Turkey.

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 upto 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 : 

ROUTE OF INFECTION Feco oral route Contaminated feed and water. Virus found in high concentration in faeces & litter.

Pathogenesis : 

Pathogenesis Infection through mouth virus present in macrophages & lymphoid cells in caeca Intestine liver blood viraemia virus goes to bursa & different tissues

PATHOGENESIS (Cont.) : 

PATHOGENESIS (Cont.) 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 : 

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 : 

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 : 

Clinical signs/ symptoms 1)Severe / Clinical form a. Depression b. White watery diarrhoea c. Soiled vent d. Loss of appetite e. Ruffled feathers f. Unwilling to move g. Closed eyes h. Exhaustion i. Death 2)Mild / Subclinical form a. Poor growth b. Decrease response to vaccines c. Immunosuppression

Slide 14: 

Chicken with IBD exhibiting depression and severe prostration.

Postmortem Findings : 

Postmortem Findings Carcass is dehydrated. Breast muscle dark in colour. Hemorrhages is seen on thigh & breast muscle & also on the lining on the proventriculus. Kidneys are swollen a7 white appearance due to dialation of tubules. Liver may be swollen & show areas of dead tissue. Bursa is the primary organ to be affected i) On third day of infection bursa increase in size & weight due to accumulation of fluid (edema) & blood (hyperemia). ii) By the fourth day bursa is double in its normal weight & size, then decrease. iii) By fifth day bursa returns to its normal weight & continues to decrease in size.

Slide 16: 

Cont- iv) From 8 day onwards, it is about 1/3 rd its normal weight. Bursa shows necrotic foci, & a cheasy mass is found in the lumen from fallen cells. Inner surface ( mucosal surface) of bursa shows large hemorrhages. Spleen is slightly enlarged with small grey foci on its surface. Hemorrhages are observed at the junction of proventriculus & gizzard.

BF Edema & Enlargement : 

BF Edema & Enlargement

Slide 18: 

Bursa of Fabricius - enlarged and haemorrhagic

Swollen Haemorrhagic BF : 

Swollen Haemorrhagic BF

Swollen Haemorrhagic BF : 

Swollen Haemorrhagic BF

Muscular Haemorrhages- Breast : 

Muscular Haemorrhages- Breast

Muscular Haemorrhages- Leg : 

Muscular Haemorrhages- Leg

Leg & Breast Haemorrhages : 

Leg & Breast Haemorrhages

Diagnosis : 

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

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.

Vaccines : 

Vaccines Two types of IBD vaccines- 1) IBD live vaccine 2) IBD killed vaccine 1) IBD live vaccine- there are 4 types i) Mild vaccine ii) Standard intermediate vaccine iii) Intermediate plus vaccine iv) Hot vaccine

Slide 28: 

Strains of different types- 1)Mild – Leukert’s strain 2)Intermediate – Georgea strain, Gaivellelae strain, Bursin- S-2, 79-B 3)Intermediate plus – MB strain, B-2K, 4)Hot strain- 228-E

Vaccination Schedule : 

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 : 

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.

Slide 32: 

An enlarged haemorrhagic bursa of Fabricius.

Slide 33: 

Muscular haemorrhages

Slide 34: 

Haemorrhages in the thigh muscles

Slide 35: 

Haemorrhages in the pectoral muscles

Slide 36: 

Haemorrhagic in the proventriculus-gizzard junction

Slide 38: 

Bursa of Fabricius - (section) haemorrhages

Slide 39: 

THANK YOU