Although the majority of recent outbreaks of Newcastle disease in Europe, the U.S. and Colombia have occurred in backyard flocks, the level of alert has been raised for those in the commercial poultry sector in those and neighboring countries.
Within Europe, the first outbreak of Newcastle disease this year officially reported was in Luxembourg in May. It occurred in a hobby flock, in birds that had been brought in from another country, according to the Luxembourg government.
In Belgium, the first cases of Newcastle disease were observed on June 28, according to the Federal Agency for the Safety of the Food Chain (FASFC). Affected were around 3,600 birds at a farm in East Flanders.
This was followed by two further outbreaks, one in East Flanders (57,800 birds), and another in West Flanders (39,500 birds).
In each case, the source of infection is unknown. However, the virus may have been circulating among hobby flocks in Belgium since April, according to a presentation of the FASFC to the European Commission Standing Committee on Plants, Animals, Food and Feed this month.
Thirteen outbreaks of Newcastle disease occurred at different locations in the country between April 26 and July 7. Eleven of these outbreaks were in small hobby flocks, and one was at a dealer in hobby birds in Liege, Antwerp, Hainaut, Brabant Wallon, Brabant Flamande, East Flanders, and West Flanders.
At the time of the FASFC report, only one outbreak had occurred at a commercial farm. Located at Zulte in the province of East Flanders, the farm had 57,820 laying hens of three different ages. Starting on July 3, the outbreak led to the death of almost 6,100 birds, and the rest were humanely destroyed.
Concerned by the risk of the disease spreading to nearby commercial flocks — of which there were 12 within three kilometers, and 45 more within 10 kilometers — the Belgian authorities imposed bans on all commercial poultry within 500 meters of affected premises, and stopped all other movements of poultry, other birds, and hatching eggs. Feed and water could only be offered inside the poultry house, and all poultry had to be vaccinated (or re-vaccinated) against the disease. Additionally, all poultry shows and exhibitions in Belgium were canceled.
On July 13, Newcastle disease hit another commercial farm, this time at Waregem in the province of West Flanders, according to a report to the World Organisation for Animal Health (OIE) from FASFC. About 2,000 of the 39,517 birds died, and the rest were culled.
To date, the disease has not been confirmed at further Belgian poultry farms.
After these events in continental Europe, the risk level for Newcastle disease in the United Kingdom poultry sector has been raised from “low” to “medium” by the Animal and Plant Health Agency (APHA). This change is based on the proximity of the U.K. to Belgium in relation to wild bird movements, and to the practical difficulties in controlling the trade in hobby birds.
The source of the Newcastle disease virus affecting Belgian flocks remains inconclusive. According to the APHA report, it is similar to strains circulating in Eastern Europe, although it is unclear how it reached Belgium — possibly in the hobby bird market, or in wild birds. Furthermore, the agency says, Newcastle disease vaccination is mandatory in the commercial poultry sector in Belgium, so the apparent failure of the vaccine against this new virus is a concern.
In December 2017, the agriculture ministry in France confirmed to the OIE a single outbreak of Newcastle disease.
The cases were among a mixed flock of 12,000 broilers and pigeons in the northerly department of Nord. Some of the pigeons presented typical symptoms of the disease, including stiff neck, lethargy, reduced water intake, and egg drop. About 150 of the birds died, and the rest of the flock was destroyed.
There have been neither further cases of the disease nor detection of the virus in France since that time, and the region was declared free of Newcastle disease by the agriculture ministry in March 2018.
Latin America: two recent outbreaks in Colombia
Within the last few days, Newcastle disease has been detected at two premises in the municipality of Granada in central Colombia.
There are few details but several birds are reported to have died of the disease.
Multiple outbreaks in Californian backyard flocks
First cases of a virulent form of Newcastle disease (vND) in the U.S. state of California were confirmed in mid-May of this year.
According to the USDA Animal and Plant Health Inspection Service (APHIS), 66 cases have been confirmed since that time (as of July 26). All these have occurred in “backyard exhibition chickens” in three counties of California — San Bernardino (57), Riverside (five), and Los Angeles (four).
APHIS reports that vND has not been found in commercial poultry since 2003, and that the virus poses no risk to human health.
Africa: Newcastle disease in Botswana in 2017
The animal health agency of the southern African state reported to the OIE three outbreaks of Newcastle disease in poultry in the last quarter of 2017. A total of 249 poultry were affected, including 73 that died. Source of infection was thought to be wild doves and pigeons.
Continuing surveillance of wild and domestic bird species has not revealed any more cases since October, according to the agriculture ministry.
6 key features of Newcastle disease
Caused by the avian paramyxovirus type 1 virus (APMV-1), Newcastle disease is found throughout the world, according to the OIE. It is generally under control through routine vaccination in Europe, Canada and the United States, but outbreaks continue to be reported in Africa, Asia and South America.
The virus is carried by wild birds, and this may be the source of infection in most cases among poultry. Once the disease is present in the flock, spread between poultry may be rapid.
Depending on the strain of virus, birds may show nervous, respiratory or digestive symptoms. Mortality is variable but may be as high as 100 percent.
Because of the similarity in symptoms to avian influenza, diagnostic tests may be required to confirm the presence of the Newcastle disease.
Newcastle disease is considered to be a minor zoonosis. It can lead to eye infections in humans, but the condition is usually mild and self-limiting.
According to the APHA, the causative agent of Newcastle disease has recently been renamed avian avulavirus type 1. It exists in many different forms that vary in their ability to infect different bird species, and to cause differing severity of disease. Causing acute and lethal symptoms, the most virulent is referred to as velogenic or highly virulent (AAvV1 ND).