Newcastle disease is a highly contagious disease caused by a virus called the avian paramyxovirus (APMV), also known as the Newcastle Disease Virus (NDV). Newcastle disease goes by many other names such as; Avian Distemper, Avian Pneumoencephalitis, Ranikhet Disease and Exotic Newcastle Disease.
The vial disease mostly affects both domestic and wild birds in different degrees, Domestic fowls, turkeys, parrots and sometimes pigeons are always susceptible to the infection while it is mild in affecting geese, quail, ducks and guinea fowl.
Humans may become infected with the Newcastle disease virus; the resulting infection is typically limited to conjunctivitis. Recovery for humans rapid and the virus is no longer present in the eye fluids after about seven days.
Laboratory workers, vaccination crews and poultry keepers are mostly infected.
Brief History about Newcastle Disease
The first recognized outbreak occurred in 1926 in a poultry located in Java, Indonesia. However, there were earlier reports of similar disease outbreaks in Central Europe this date.
In 1896, particular in Macpherson, death of all the chickens in the Western Isles of Scotland was attributed to an infection similar to Newcastle disease.
It is likely therefore, that Newcastle disease did occur in poultries before 1926, but was recognized as a scientifically defined disease of viral aetiology dates from outbreaks during this year in Newcastle.
The name “Newcastle disease” was invented by Doyle as a temporary measure in order to avoid a descriptive name that might be confused with other diseases. The name however, continued to be of function although when referring to the Newcastle Disease Virus (NDV), the synonym ‘avian paramyxovirus type 1’ (APMV-1) is now often employed.
Causes of Newcastle Disease
The disease is caused by the paramyxovirus. The Newcastle Disease Virus strains were originally grouped into three virulent groups using an embryo inoculation process; virulent (velogenic), moderately virulent (mesogenic) and low virulence (lentogenic).
For regulatory purposes, this classification system was modified so that velogenic and mesogenic viruses are now classifies as Virulent NDV; the Virulent NDV is used in the production of vaccines.
The most severe strain of the virus is called viscereotropic velogenic Newcastle disease (VVND), which is often referred to as Exotic Newcastle Diease.
Contamination is usually through direct contact with dead or infected birds; the virus is usually present in manure and is air borne. Some other unverified causes of infection can be contaminated equipment, carcasses, water, food and clothing as earlier stated, the Newcastle disease does not affect people as it does with birds but the infection- conjunctivitis should not be overlooked.
Symptoms of Newcastle Disease
The following known clinical symptoms exist in birds only and it varies depending on the system of the body affected. Some strain of the virus attacks the nervous system while others affect the respiratory system and the digestive system.
Apart from the system affected, the severity of Newcastle Disease varies widely, and it is also dependent on other factors such as: the strain of virus, the age of the bird as young chicks are more susceptible, concurrent infection with other pathogens, stress and immune status.
Most featured signs of the Newcastle Disease in birds are manifestations as a result of the central nervous system been affected, the symptoms are:
- Abnormal head and neck positioning characterized by head tilt and wry (twisted) neck appearance.
- Ataxia (uncoordinated) walk and body movement; affected birds may be seen stumbling frequently and appear to lack balance and muscle spasms.
- Partial or total paralysis of the leg(s) and wings.
- Drooping wings.
- Many affected birds may only show signs of general weakness and prostration.
- Diarrhea with hemorrhage (blood in stool, usually greenish and watery) is a classical sign of the highly pathogenic (visceral, velogenic) Newcastle disease in domestic chicken.
- Sneezing and Nasal discharges
- Swelling of the tissue lining around the eyes and sometimes in the neck.
- Loss of weight due to loss of appetite in birds
- Fluffed up feathers
- In laying birds, there can be a partial or total drop in egg production and produced eggs possess thin shells.
In humans, conjunctivitis or pinkeye following Newcastle Disease infection may presents the following symptoms:
- Redness, dryness, itchiness of the eyes and eyelid
- Pains in area around the eyes
- Nasal congestion and sneezing
- High sensitivity to light
- Crust formation around the eyes.
Transmission of Newcastle Disease
Newcastle disease is dispersed by already infected birds by shedding the virus in feces, body fluids (respiratory discharges fro, nares, mouth and eyes), and eggs.
The disease is spread primarily through direct contacts between healthy birds and bodily fluids of infected birds. When Newcastle disease infected birds that may shed large amounts of the virus, all members of the flock become infected within a week. Infected ducks and geese (wild waterfowl) can actually maintain low virulence strains of the Newcastle disease virus to themselves and other birds including chickens.
The Newcastle virus can survive for long periods outside the living host and cam remain infective for several weeks in the environment, specifically in regions of low temperature or when it is been organically protected such as in carcasses, water eggs and feathers. However, the virus is destroyed rapidly by exposure to UV rays in sunlight.
Incubation period of Newcastle Disease Virus
Between the period of infection and appearance of the first clinical sign is generally two to six days but can be up to 15 to 21 days. However, incidents have been recorded in severe viral strain majorly killing flock within 72 hours of infection without showing any prior signs of the disease.
Prevention of Newcastle Disease
Prevention of a Newcastle Disease infection in birds relies solely on good and early quarantine, biosecurity procedures and vaccination routinely.
Newcastle Disease vaccination of commercial meat and egg layer birds is very necessary and has been made compulsory in many Australian States. So, legislations should be designed to reduce the likelihood of outbreaks from specific sources.
In regions and areas that are virulent Newcastle Disease Virus free, the primary aim should be to prevent the introduction of the virus. Because migratory and other feral birds frequently carry NDV strains of low virulence which spread from time to time in domestic poultry.
Also, poultry keepers should be observant, and they should regularly check their flocks, ensuring total separation of infected birds from the rest of the flocks and provision of vitamin A rich supplements and Vitamin A rich feeds; from studies conducted, these delays clinical signs of Newcastle Disease virus and significantly reduced mortality rate by lessening the negative impact of the virus on the body system.
Treatment of Newcastle Disease
There is no particular treatment for Newcastle disease; however, combating the disease with antibiotics to control secondary infections may be of huge positive impact. Visit a veterinarian for suitable antibiotics for the birds.
Birds and eggs are especially chicken products, and they are good sources of protein, they serve as ready cash for some households. The small-scale poultry producers have an enormous potential to stimulate growth in the socio-economic sector of rural economies and in resource-average households, yet Newcastle disease is a disease that has single-handedly withheld the full potentials of this sector.
The commercial sector is not also left out as it bears a huge economic burden as a result of the disease.
- Newcastle Disease; http://www.gov.scot/publications/newcastle-disease
- Newcastle Disease in Poultry; http://www.msdvetmanual.com/poultry/newcastle-disease-and-other-paramyxovirus-infections/newcastle-disease-in-poultry
- Virulent Newcastle Disease; https://en.m.wikipedia.org/wiki/Virulent_Newcastle_disease