77. Newcastle disease (post mortem lesions, diagnosis, prevention, control).

Question 1

Pathological lesions?

Answer 1

Pathological lesions

• There are no pathognomic gross lesions; several birds must be examined to determine a
• tentative diagnosis & final diagnosis must await virus isolation & identification
• Only velogenic strains produce significant gross lesions
• Lesions that may be found include:
• Swelling of periorbital area or entire head
• Oedema of the interstitial or perotracheal tissue of the neck; especially at the thoracic inlet
• Congestion & sometimes haemorrhages in the caudal pharynx & tracheal mucosa
• Diphtheritic membranes may be evident in the oropharynx, trachea & oesophagus
• Petechiae & small ecchymoses on the mucosa of the proventriculus,
• concentrated around the orifices of the mucous glands
• Oedema, haemorrhages, necrosis or ulcerations of resp/digestive lymphoid tissue,
• including cecal tonsils and payers patches
• Though not pathognomic, ulceration/necrosis of payers patches suggests Newcastle disease
• Oedema, haemorrhages or degeneration of ovaries
• Although less evident in older birds, haemorrhages of the thymus & bursa of Fabricus
• May occur
• Spleen may appear enlarged, friable & dark red or mottled
• Some cases may present pulmonary oedema & pancreatic necrosis
• Haemorrhages everywhere, lymphocytic encephalitis important!

Question 2

Diagnosis?

Answer 2

Diagnosis

• Samples
• Samples should be collected from recently dead birds or moribund birds that have been killed humanely
• For ID of the agent
• Dead birds: oro-nasal swabs; lung, kidneys, intestine (including
• contents), caecal tonsils, spleen, brain, liver & heart tissues, separately or as a pool
• Live birds: tracheal or oropharyngeal & cloacael swabs (visibly coated with faecal material) from live birds or from pools of organs & faeces
• from dead birds; small delicate birds may be harmed by swabbing, but the collection of fresh faeces may serve as an adequate alternative
• Special attention should be given to appropriate types of media for shipping
• For serological tests: clotted blood samples or serum
• Identification of the agent
• Virus isolation (the prescribed test for international trade): inoculation of embryonated SPF eggs & tested for haemagglutination (HA) activity &/or by
• use of validated specific ,olecular methods
• Virus identification: use of specific antiserum in a haemagglutination inhibition (HI) test
• Cross-reativity & the risk of mistyping an isolate can be greatly reduced by using a panel of reference sera or monoclonal Abs (MAbs) specific for APMV-1, APMV-3 & APMV-7
• Pathogenicity index determined by intracerebral methodology
• Pathogenicity index determined by molecular basis
• Definition of Newcastle disease
• A) criteria based on either intracerebral pathogenicity index (ICPI) in day old chicks or
• B) correlation of multiple basic amino acids
• Monoclonal Abs: for rapid identification of NDV (avoiding cross-reactions with other APMV serotypes) & a valuable method for grouping & differentiating
• isolates of NDV
• Phylogenetic studies: allows for the rapid epidemiological assessment of the
• origins & spread of the viruses responsible for ND outbreaks
• Molecular techniques in diagnosis: advantage of extremely rapid
• demonstration of the presence of virus
• Virus isolation is possible, RT-PCR most often used
• Serological tests - only to prove that the animals are not immunised
• HA & HAI tests: most widely used & detects Ab response to virus
• glycoprotein (predictor against disease)
• Enzyme-linked immunosorbent assay (ELISA): as whole virus is used as Atg,
• detects Ab to all of the virus proteins
• Commercial ELISA kits available to assess post-vaccination Ab levels

Question 3

Differential diagnosis?

Answer 3

Differential diagnosis

• Fowl cholera: no neural signs, highly pathogenic avian influenza, laryngotracheitis,
• fowl pox (diphtheric form), psittacosis (psittacine birds), mycoplasmosis, infectious
• bronchitis, asperguillosis,
• Management errors such as deprivation of water, lack of or nutritionally deficient feed & poor ventilation
• In pet birds: Pacheos parrot disease (Psittachine birds) Salmonellosis, adenovirus & other paramyxoviruses
• paramyxoviruses
• In cormorants & other wild waterfowl: botulism, fowl cholera & conformational abmormalities

Question 4

Prevention & Control and public health consequences?

Answer 4

Prevention & control

• No treatment
• Sanitary prophylaxis
• Bird-proofing houses, feed & water supplies
• Proper carcass disposal
• Pest control in flocks; insects & mice
• Avoidance of contact with birds of unknown health status; including newly acquired domesticated poultry, pet birds & wild or feral birds
• Control of human traffic; facility employees should not have contact with outside birds & consideration of a policy of shower-in with dedicated clothing
• Control of vehicular traffic; strict disinfection of conveyances & equipment
• One age group per farm (“all in or all out” breeding is recommended; disinfection btwn groups
• During outbreaks
• Effective quarantines & movement controls
• Destruction of all infected & exposed birds; 21 days before restocking
• Thorough cleaning & disinfection of the premises
• Medical prophylaxis ʹ vaccination
• One of the most important considerations for any vaccination programme is the
• type of vaccine to be used, the immune & disease status of the birds to be vaccinated, the level of maternal immunity in young chickens & the level of
• protection required in relation to an possibility of infection with field virus under
• local conditions; various strategies exist & references, like the OIE Terrestrial
• Manual, should be consulted
• Vaccination with live &/or oil emulsion vaccines can markedly reduce the losses
• in poultry flocks but cannot ensure the prevention of virus circulation
• (replication & shedding)
• Sentinel chickens have been employed to monitor vaccinated flocks
• In general, the more immunogenic live vaccines, are more virulent, & are therefore more likely to cause adverse side effects
• Conventional live virus vaccines: 2 groups
• Lentogenic vaccines (e.g. Hitchner-B1, LaSota, V4, NDW, I2 & F)
• Mesogenic vaccines (e.g. Roakin, Mukteswar & Komarov); infectious of these viruses,
• would fall within the OIE definition of ND
• Live virus vaccines administered to birds by incorporation in the drinking water,
• delivered as a coarse spray (aerosol), or by intranasal or conjunctival instillation;
• some mesogenic strains are given by wing-web intradermal inoculation
• Inactivated vaccines
• Tend to be more expensive than live vaccines
• Application entails handling & injecting individual birds
• Prepared from allantoic fluid that has had its infectivity inactivated by
• formaldehyde or beta- propiolactone
• Incorporated into an emulsion with mineral oil or vegetable oil, & is
• administered IM or SC; each bird thus receives a standard dose
• Advantage of no subsequent spread of virus or adverse resp reactions
• Virulent & avirulent strains are used as seed virus; from a safety control
• perspective
• The use of the latter appears more suitable: much larger amount of atg is
• required for immunisation than for live virus vaccination; (no virus
• multiplication takes place after admin)
• New recombinant vaccines: fowlpox virus, vaccinia virus, pigeonpox virus, turkey
• herpesvirus & avian cells in which the HN gene, the F gene, or both, of NDV are expressed
• Public health consequence:
• high amount of the virus must be inhaled to get the
• symptoms (conjunctivitis, eye lid oedema, lacrimation)