Newcastle disease is a highly contagious, worldwide occurring and often severe disease affecting birds, especially domestic poultry. It is caused by a paramyxovirus. This germ is present in bronchial secretions and droppings. Transmission can occur through drinking water, feed, feed and water troughs, clothing, instruments and equipment.
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Origin of Newcastle Disease
Newcastle disease, or poultry pseudofowl flu, is a highly contagious viral disease that can affect a large number of bird species and cause severe economic losses in many countries. The causative agent is called Newcastle disease virus or avian paramyxovirus type I (avian paramyxovirus type 1, APMV-I). The first cases of Newcastle disease were described in 1926 in Java, Indonesia.
The economic impact of Newcastle disease is enormous and should not only be measured in terms of direct commercial losses such as mortality. In developed countries free of the disease, control measures, such as vaccination, and repeated testing to maintain their disease-free status represent a huge loss to the poultry industry.
In developing countries, where eggs and poultry meat are the main source of dietary protein, the Newcastle disease virus, due to its endemic circulation, constitutes an obstacle to the development of poultry production. In terms of public health, in addition to its contribution to malnutrition, Newcastle disease is considered a minor anthropozoonosis.
Incidence and Distribution
Newcastle disease is enzootic in most of Africa, the Middle East, Asia, Central America and the northern part of South America. In more developed areas, such as Western Europe and the United States, sporadic epizootics are still observed, despite the widespread use of vaccines.
Epidemiology
Epidemiological studies have indicated that several epizootics of Newcastle disease have occurred since the first described cases of the disease. First, genotypes II, III, and IV were enzootic in North America, Asia, and Europe, respectively, during the 1930s and 1940s.
Newcastle disease virus strains of genotype VI emerged as epizootics in the Middle East and Asia in the 1960s, while those of genotype V appeared in North America and Europe in the early 1970s. The fourth outbreak occurred during the 1990s in the Middle East following the prevalence of genotype VII. Genotype VIII was endemic in South Africa during the previous decade. (See Article: Breeding Hens)
Transmission
- Transmission of ND virus between poultry occurs via the fecal-oral route.
After multiplication of the Newcastle disease virus in the respiratory or digestive tract, infected poultry excrete the virus by the airborne or fecal route. Contaminated droplets and aerosols can be inhaled by healthy poultry or affect their mucous membranes, while feces can contaminate feed and drinking water and be ingested by other birds in the poultry house.
- The virus can also spread from one farm to another by transporting contaminated material such as soil, water or feed.
Indeed, although it is an enveloped virus, the Newcastle disease virus is relatively stable outside the host and can survive several days or even months in the presence of organic matter depending on temperature and humidity. This mode of transmission explains why an episode of Newcastle disease can quickly turn into an epizootic.At present, the possibility of vertical transmission is controversial. (See Article: How many hens to have per square meter?)
The Disease Presents Itself In 3 Forms:
- Lentogenic or slightly virulent
- Mesogenic or moderately virulent
- Velogenic or very virulent, also called “exotic form of Newcastle disease”.
Lentogenic strains are very but cause few disease outbreaks. The disease is usually manifested by respiratory signs, but the clinical picture is as follows: it may be dominated by despondency, nervous manifestations or diarrhea.
In its highly pathogenic form, Newcastle disease is covered by the Terrestrial Animal Health Code of the World Organisation for Animal Health (OIE) and is one of the diseases that must be reported to the OIE (OIE Terrestrial Animal Health Code).
Diagnosis
It is established by isolating the virus from tracheal or cloacal swabs along with serological tests to detect elevated antibody levels. Infectious laryngotracheitis can lead to similar symptoms, but lesions, serologic testing, and virus isolation are very important.
Symptoms
During natural exposure, the incubation period of Newcastle disease virus varies from 2 to 15 days. Generally, the clinical signs of Newcastle disease are:
- depression
- diarrhea
- prostration
- edema around the eyes
- decrease or interruption of egg laying.
Mortality and nervous signs torticollis, clones, among others, are very often present. Hemorrhagic lesions in the Provencal and intestine are almost constant. However, some differences can be made depending on the pathotype of the disease, as described above. They also include inflammation of the trachea, pneumonia or the presence of foam in the alveoli are the main lesions. Hemorrhagic lesions may be observed in the proventriculus and intestines.
Is there any treatment?
There is no treatment for Newcastle disease. Immunization against Newcastle disease with live or inactivated (killed) and adjuvanted vaccines is the only reliable preventive method.
The aim of the various prevention strategies is to prevent infection of susceptible birds and to reduce the number of susceptible birds by vaccination. Biosecurity and hygiene are considered the first lines of protection against the introduction of any poultry disease and, in particular, against Newcastle disease.
Therefore, the movement of people, breeders, veterinarians, care personnel, among others, and vehicles should be limited and be accompanied by disinfection and change of clothes and footwear, even in the absence of diseases. Direct and indirect contact of poultry with wild birds or pigeons should also be avoided.
Due to costs, air filtration and overpressure measures to limit the entry of virions into the poultry house are mainly reserved for high genetic value farms and parents.
Although biosecurity may be sufficient, vaccination is considered an additional precautionary measure, especially in areas with high density poultry populations. Therefore, preventive vaccination is also part of the general prophylactic measures against Newcastle disease.
Indeed, mass vaccination of poultry is aimed at limiting the risk of infection of poultry with NDV and reducing viral transmission, while avoiding clinical signs and mortality.However, vaccination policy varies according to the endemic status and emergence prospect of ND or according to geographical location.
Thus, in countries where NDV is absent and constitutes an epizootic threat, the aim of vaccination is to ensure maximum protection against ND. This is particularly the case in Belgium, the Netherlands and Germany, where vaccination has been made compulsory in all types of production since the 1990s following epidemics of Newcastle disease.
In other countries, such as France, only long-lived poultry (layers and breeders) are vaccinated. In countries where the Newcastle disease virus is enzootic, the aim of vaccination will be to reduce the infection pressure. Therefore, the disease may not appear due to the vaccination campaign.
Finally, countries such as Sweden, Finland and Estonia do not vaccinate at all and therefore reject any form of introduction of NDV into their territory. Europe only allows the use of certain specific attenuated vaccines and considers other vaccines to be of unacceptable virulence (mesogenic strains).
Finally, the measures taken to eradicate Newcastle disease during an outbreak are determined by several factors, such as the number, type and density of poultry farms in the region and country. Thus, in areas of lower density, an eradication policy is adopted with the culling of infected birds, in-contact birds and their products, followed by cleaning and disinfection of the poultry house and sanitation.
This policy generally includes restrictions on trade of birds in a defined quarantine zone around the outbreak for at least 21 days from the last outbreak. The same sanitary measures are taken in countries with high poultry density, with or without emergency vaccination of birds in a buffer zone around the outbreak called ring vaccination.
Newcastle Disease In Humans
Transmission to humans is anecdotal and causes eye infections, such as:
- conjunctivitis
- edematous eyelids and lacrimation.
Sometimes headaches and fever are observed, with or without conjunctivitis.
In Pigeons
Name of a family of viruses that includes the orthomyxovirus group often referred to as “myxoviruses” and the paramyxovirus group. In this family, the shape of the virions is similar and one property is common: the ability to agglutinate red blood cells. However, for the rest, there are fundamental differences between the two groups.
The orthomyxovirus group includes influenza (flu) viruses type A (humans, pigs, horses and birds), B and C (humans only). Virus particles (virions) are spherical or filamentous, irregularly shaped, with a diameter of approximately 100 nanometers (1 nm = 10 -9 n), comprising a dense central portion containing ribonucleic acid (RNA) with a total molecular weight of 3.10
Six Daltons in eight segments of negative polarity (this is the positive copy that is messenger) associated with proteins to form filamentous nucleocapsids, with helical symmetry six to nine nanometers in diameter surrounded by an envelope consisting of lipids and proteins. The virus is destroyed by lipid solvents (ether, detergents). The particles contain 66 p. 100% protein, 25% 100 lipids, 8 p. 100 carbohydrates and 1 p. 100 RNA. (See Article: Characteristics of pigeons)
The virus multiplies in cells of the respiratory system and other organs.RNA is synthesized in the nucleus, proteins in the cytoplasm and maturation, which includes assembly of internal constituents and envelope formation, takes place at the level of the cell membrane from which the virus borrows its lipids. The virus contains at least eight different proteins. It has a polymerase capable of copying RNA.
On the surface of the envelope are spicules which are small glycoprotein “spines” of two types: some are able to bind to cell receptors and thus agglutinate certain free cells such as red blood cells (hemagglutinin), others have enzymatic activity (neuraminidase). Envelope lipids have the same composition as cell membrane lipids.
Symptoms
The virus can have a variety of impacts. Therefore, the disease can be mild or very severe with 100% mortality. Newcastle disease In its most severe form, Newcastle disease begins with high fever accompanied by profuse, greenish diarrhea. The bird coughs, has trouble breathing and the tissues around the eyes and neck swell.
Subjects no longer eat and drink a lot. They continue with very characteristic nervous symptoms: head sideways, rounded back, great difficulty in moving the wings which are then drooping, increasingly hesitant approach. The plumage is ruffled. Then convulsions, paralysis and death occur.
In Broiler Chickens
Newcastle disease is caused by a paramyxovirus that mainly affects poultry. Broilers are the most susceptible hosts. The incubation period varies depending on the disease and usually lasts 4 to 5 days (between 2 and 15 days). The virus is easily inactivated by formaldehyde, alcohol, merthiolate, lipid solvents, lysol and ultraviolet rays. Vaccination is a routine practice for disease prevention and control. However, it is difficult to transport and store vaccines. (See Article: Broiler Chicken)
Clinical Signs
The clinical signs of Newcastle disease vary greatly depending on the virulence and tropism of the virus. The species of birds affected, the age and immune status of the host and the environmental conditions. Therefore, no clinical sign can be considered as specific for Newcastle disease.
- Chickens infected with virulent strains of Newcastle disease virus may die if they show no signs of disease.
- The chicken ruffles its feathers and “its plumage appears to crawl on the ground.”
- Lethargy and inappetence.
- Respiratory signs such as mild rales and rubbing can be detected by careful examination.
- Swelling of the head and neck.
- Greenish diarrhea.
- Significant decrease in egg production. Sometimes, eggs laid may be distorted.
- Nervous signs of tremors, torticollis, convulsions and paralysis of the wings and legs are only observed when the disease is in an advanced stage.
- The mortality rate can be very high and sometimes reaches 50% to 100%.
Autopsy Lesions
Autopsy lesions are quite characteristic but not specific. Newcastle disease may be suspected when the following lesions are found:
- Congestion and mucous exudate in the trachea
- Pulmonary congestion (heavier than normal)
- Hemorrhages of the mucosa of the Proventriculus.
- Hemorrhagic and necrotic ulcers of the lymph nodes of the intestine, intestinal tract, gastrointestinal tract and intestinal tract and the bursa of Fabricius.
- Congested ovarian follicles in hens during the laying period.
Serum Samples
The reliability of any serological test depends to a large extent on the quality of the processed samples. Hemolyzed or contaminated samples often give few reliable results. Poor quality samples will give poor quality results and require the animals in question to be rechecked.
Blood sampling technique
To draw blood from domestic poultry, a wing vein is usually used. A different needle should be used for each animal to avoid the risk of transmission. The mechanics of transferring infectious agents from one animal to another, and
- If samples cannot be brought quickly to the laboratory and if samples are not available, the laboratory should be informed of the results, delays are likely to occur between the time of sample collection and analysis, it is preferable that you transfer the serum into sterile 5 ml or 1.8 ml plastic tubes, closed with<br
- In rural areas, it is preferable to feed in the morning, when the poultry are released from the poultry house. In areas with many water points, poultry find their own drinking source and this vaccine is not appropriate.
Don’t do it:
- Use metal drinking troughs
- Use disinfectants to clean the water troughs, as they will inactivate the vaccine system
- Use treated tap water. (If you only have access to treated tap water, it is recommended to let the water stand overnight to allow the chlorine to evaporate or to add one teaspoon of powdered milk per 10 liters of water to neutralize.
