NEWCASTLE DISEASE (Doyle’s Disease or Avian Pneumoencephalitis)
Newcastle disease (ND) is a highly contagious viral disease in many species of domestic, exotic and wild birds that, depending on its tropism, is characterized by marked variations in morbidity, death rate, symptoms and lesions. . Clinical signs are extremely variable depending on the strain of virus, species and age of bird, concurrent disease, and preexisting immunity.
The disease was first diagnosed in Newcastle-on-Tyne in England but was later found in United States in 1944 and has now spread worldwide avian populations
It is recognised by some/all of the following signs;
• Respiratory distress
• Nervous symptoms (sometimes)
Newcastle Disease Virus (NDV Paramyxovirus) of which 3 strains/ forms according to their pathogenicity
Lentogenic strain-very low pathogenic (non virulent)
Mesogenic strain-moderately pathogenic (intermediate virulence)
Velogenic strain-highly pathogenic (highly virulent)
Velogenic strains produce severe nervous and respiratory signs, spread rapidly, and cause up to 90% mortality. Mesogenic strains cause coughing, affect egg quality and production, and result in up to 10% mortality. Lentogenic strains produce mild signs with negligible mortality
The virus are present in all secretions and excretions of the bird-saliva and feaces, respiratory discharges hence making the disease to be common wherever poultry is bred as the virus is very resistant. All species of birds are susceptible. The virus can be isolated from other livestock. Infected laying birds can continue passing the virus through egg for 1-2 months
TRANSMISSION/SPREAD OF INFECTION
Infection is through ingestion of contaminated food materials with contamination occurring through discharges from infected birds. Infection is by direct contact with infected materials. The virus is highly contagious and spread in droppings and nasal discharge via direct contact, through the air, or on contaminated items such as bottoms of shoes, food, or infected dishes and cages. The virus can also penetrate eggshells that come in contact with infected tissue or food, thereby, infecting the embryo.
There is viraemia after infection. Virus is carried to almost all internal organs where it produces pathological lesions including the brain. There is inflammation particularly of the respiratory tracts and brain.
There is initial rise in temperature and discharges from the nose. Atimes there is shaking of the head probably to dislodge the exudates present in the nasal cavity.
These are followed by signs of Respiratory distress, important signs include; gasping respiration through half opened beak and stringy salivation from the beak. Mortality rate in this form is moderate
Enteric form of the disease presents greenish diarrhoea terminating to death. Mortality rate is very high in enteric form of the disease reaching up to 80-100% in susceptible flock.
Some cases show paralysis of the leg making walking difficult. Others may show nervous signs like twitching of the muscles. In young flock nervous signs may be more clearly seen which include torticolis, circling movement and walking backwards, Death may occur in quick successions. Cessation of laying, abnormal egg colour, egg shape and surface with watery albumen is common in laying birds.
POST MORTEM (PM) LESIONS
There is thick mucus in respiratory tract (nasal and lung organs), congestion of the lung and cloudy appearance of the air sacs)
The brain and meninges are congested
The Gastrointestinal tracts lesion are present in the
proventriculus with pin point haemorrhages at the tips of the glands
congestion of the ileocecal junction (atimes may be ulcerative) and haemorrhages at the glands.
catarrhal enteritis and ulcer in the small intestine
abnormal or normal spleen
The reproductive organs are inflamed (oophoritis, salpingitis), atresia of the follicle
The above figure (1) shows the petechiation and pin point haemorrhages of the gizzard and proventriculus- in the Velogenic (Viscerotropic NDV) form of Newcastle Disease (ND
The above figures (2, 3) show the haemorrhagic necrotic and focal diphtheroid lesions affecting the mucosa of the buccal cavity and the stomach respectively- in the Velogenic (Viscerotropic NDV) form of ND
Fig 5 Intestine
The above figures (4, 5) show the enlargement and haemorrhages of ileocaecal tonsils and intestines respectively- in the Velogenic (Viscerotropic NDV) form of Newcastle Disease (ND)
1. Presence of respiratory signs, nervous /paralysis symptoms and enteric involvement in the same flock with greenish and bloody diarrhoea. History of death in quick succession in unprotected flock
2. PM findings of pinpoint haemorrhages and enlargement of the glands of proventriculus and ileocecal junctions
3. Confirmatory diagnosis is by isolation and identification of the virus
The figure 6 above shows the neurotropic form of the disease is clinically manifested by ataxia, opisthotonus, torticolis, paresis and paralysis of legs. This form is frequently accompanied by respiratory symptoms.
i. No treatment is given though antidiarrhorics and antibiotics may be given
ii. If the disease occurs in a farm, immediate slaughter of the affected and in contact birds is advised
iii. Thorough disinfection of the pens
iv. Hygienically dispose of the animals
v. Injections of hyper-immune serum have been used to protect exposed birds before they become symptomatic. When birds begin showing symptoms, this is ineffective.
Unfortunately, the prognosis for this disease is poor, with nearly a 100 percent mortality rate, once infected.
a) Quarantine or isolate infected /suspected birds
Three (3) vaccine types used are
- Newcastle Disease Vaccine Intraocular (Ndv-I/O)
- Newcastle Disease Vaccine Lasota (Ndv-L)
- Newcastle Disease Vaccine Komorov (Ndv-L)
- Newcastle Disease Vaccine (Strain I2)
The following protocols and recommendations are helping to reduce the incidence of Newcastle Disease:
- All birds to be imported into Nigeria must be quarantined in facilities outside the country for 30 days before granting entrance into the country
- All suspected cases of Newcastle Disease must be reported to the appropriate regulating body.
- Newly acquired birds should be isolated for at least 30 days – 6 weeks.
- Set aside shoes and clothing to be worn only in the quarantine area.
- Certification should be requested from the supplier of your birds that confirms your bird or birds are legally imported or are raised within the country, health certificate should be requested and you should verify that the bird(s) will be transported in new or thoroughly disinfected transport cages.
- Ensure that your day old birds are given intra ocular vaccine on day 1
NB: The biggest contributor to the spread of Newcastle Disease is the avian smuggling industry
Recommendations to poultry farmers are as follows
▬ Allow only essential workers and vehicles on the farm or at least only in the areas immediately adjacent to and including the poultry houses.
▬ Provide clean clothing and cleansing facilities for employees.
▬ Clean and disinfect vehicles (including tires and undercarriages) entering and leaving the farm.
▬ Farm attendants and workers should avoid visiting other poultry operations outside their jurisdiction
▬ Maintain an all-in, all-out philosophy of flock management:
- Control the movement of all poultry and poultry products from farm to farm.
- Do not cull mature birds from a flock to be sold in a live market.
- Clean and disinfect poultry houses between each lot of birds.
▬ Do not keep pet birds on the farm.
▬ Protect flocks from wild birds trying to nest in poultry houses and do not feed flocks combined with domestic birds.
▬ Maintain strict controls over the disposal and handling of bird carcasses, litter, and manure.
▬ Bring diseased birds to an approved laboratory for examination.
We can all play a role in helping to eliminate this deadly avian disease by following the guidelines above. Any poultry or pet bird owners or veterinarians who suspect a bird may have Newcastle Disease, should immediately contact State or Federal Livestock Authorities. Any suspicions regarding suppliers should also be reported.
Vaccine should be purchased from a reliable source and handled professionally to avoid a break in cold chain or vaccine break. It is also worth noting that birds would react to the vaccine with pyrexia and lethargy immediately after vaccination, assist the birds with multivitamins. Avoid transporting the birds immediately after vaccination. Avoid vaccination of stressed or sick birds.
Dr Audrey Okafor.
Dr Paul Oche Adoyi.