Newcastle Disease Outbreak 2018/2019
What Aviculturists Need to Know
By Steve Duncan
Avicultural Society of America
Organization of Professional Aviculturists
In April of 2018, Virulent Newcastle Disease (VND) was detected in a chicken in Los Angeles County, California. Soon after, other positive cases occurred in chickens elsewhere in Los Angeles County and in neighboring counties to the east, Riverside and San Bernardino Counties. Because VND can have a catastrophic impact on the poultry industry, USDA has a policy of eliminating it from the USA. Whenever a positive case occurs, a taskforce of state and federal veterinarians and agriculture officials is immediately established to control the spread of the virus. This is important not only to prevent the threat to our food supply and the birds in our aviaries, but it is also important for the US to remain VND-free since we export poultry to countries that would refuse our products if VND is present here. This gives any VND outbreak huge economic consequences as well. Since this outbreak is in California, USDA is working with the California Department of Food and Agriculture (CDFA) to control and eliminate the disease.
Newcastle Disease comes in multiple forms. It is caused by a type of paramyxovirus (PMV). Paramyxoviruses are a large group of viruses that are responsible for diseases such as measles and mumps in humans. The types that infect birds are called avian paramyxoviruses. There are 9 types of avian paramyxoviruses which vary in their ability to infect different types of birds. Parrots, for example, can be infected by PMV-1,2,3 and 5. Newcastle disease is caused only by PMV-1, but PMV-1 can infect all varieties of birds.
Within PMV-1, there are four groups based upon their effect on chickens. Two of the four groups of Newcastle viruses naturally occur in the U.S., but neither of these two endemic groups cause serious disease in chickens so they are not considered virulent. The other two groups of Newcastle viruses are the ones to be concerned about. These are called Virulent Newcastle Disease (VND) and are devastating to chickens. VND was formerly referred to as Exotic Newcastle Disease (END). The term exotic simply means it doesn’t naturally occur here in the United States and should not be taken to mean that exotic birds are somehow connected to the outbreak. VND can be either VVND (Velogenic Viscerotropic Newcastle Disease) which attacks the digestive system, or VNND (Velogenic Neurotropic Newcastle Disease) which attacks the nervous system. Complicating it further, within each of these two groups of VND, there are different strains of viruses each with differing effects on various bird species, but all strains of VND (VIRULENT Newcastle Disease) are a serious disease threat to the poultry industry and must be controlled to prevent damaging our food supply, exotic birds, and economy. The current strain of virus causing the outbreak in California appears to be especially good at infecting chickens and much less effective at infecting exotics, but good biosecurity is always essential.
The VND virus is typically spread through direct contact with an infected bird’s droppings or mucous. Bird-to-bird transmission is the most dangerous, and entire chicken flocks can be affected quickly if the virus is introduced. The most virulent strains can cause mortality in chickens after only a 4-day incubation period. The virus can be transmitted on clothing and equipment contaminated at a facility where the disease is present. Wild birds do not appear to be a factor in the spread of this strain of VND. Certainly, any wild animal or bird that may feed on a recently deceased infected chicken could potentially carry the virus on the surface of its body, but they do not appear to be carriers through infection and active shedding of the virus. The virus can remain infective outside the host for 7-30 days in contaminated fecal material or bodily fluids. It lasts longer in colder, wetter conditions, so it is more likely to spread this way in a wet winter than in a dry summer, for example.
It is recommended to change clothing, especially shoes, before returning to your birds after visiting places where the virus could be picked up such as other bird collections, bird shows, or feed stores. Taking simple biosecurity measures should be a normal procedure anyway to prevent the introduction of any disease to your flock. Lysol spray is effective against Newcastle virus and is readily available. Most veterinary disinfectants are also effective against VND but check the label to be sure. Spraying shoes and clothing, as well as any other items, such as feed bags for example, that are brought onto your property is a good idea that can help reduce exposure to all diseases including VND. Of course, quarantining any new birds being added to your flock is always a must.
Why not vaccinate? The available vaccine for Newcastle Disease is only effective against the less virulent strains and is not very effective against VND. What’s worse is that a vaccinated bird may achieve only enough immunity to prevent it from dying but not enough to prevent it from becoming infected and harboring VND thus spreading it further than it would be spread without the vaccine. Since VND is not normally present in the US, it makes sense to not vaccinate especially since vaccinating could actually help the virus spread in the rare instances that it arrives here.
The import quarantine system in the USA was specifically created to prevent the introduction of VND into the US, although it also is now used to prevent the introduction of other avian diseases as well. As a result, VND is now mostly brought to this country through smuggled birds that do not go through proper quarantine. The most common type of smuggled bird to carry the virus may come as a surprise to many because we don’t often think of them as being smuggled. We often hear about smuggled exotic birds which are certainly a threat too, but it turns out that the main vectors are chickens smuggled across our southern border. VND is normally present in Mexico, so any birds illegally coming across the US/Mexico border should be suspected of carrying the virus. Since the import quarantine system was put in place, smuggled chickens have been the main culprit for bringing VND to the US.
Making it more difficult to control is the fact that these smuggled chickens are primarily fighting-cocks which are destined for illegal cock-fighting activities. Since cock-fighting is already an underground, illegal activity, it is very difficult to control their movement. Making matters worse is the nature of the activity. Fighting-cocks from many different owners are brought together over large distances at an event where they comingle and transmit the virus to each other. They are then brought back to their homes carrying the virus with them. This is why the positive cases appear to jump around to localities that may be many miles apart. As soon as a flock is infected, the virus can then spread to other neighboring chickens at nearby homes via foot traffic or free-roaming chickens. These neighboring flocks may simply be personal egg-laying hens or pet chickens, but the result is the same – a hotspot of infected flocks in a neighborhood. Tragically, workers at commercial poultry farms may also unwittingly track the virus from home flocks to commercial facilities resulting in the loss of many thousands of chickens thus resulting in the serious concern for containment.
When CDFA and USDA make announcements about the spread of VND in “backyard flocks” or “exhibition chickens”, they are referring primarily to the movement of fighting-cocks, but because the virus spreads to nearby flocks too, these are more inclusive terms. However, the fact is clear that the spread of the virus creating new hotspots miles away is primarily the result of the movement of fighting-cocks to and from illegal events.
During outbreaks in the 1970’s and in 2002/2003, the Newcastle task forces instituted drastic euthanasia efforts targeting all birds within a hotspot radius of a positive VND case. This resulted in the euthanasia of rare species and beloved indoor pet birds that were not a factor in the spread of the disease. With increased understanding of how the VND virus is being spread, this drastic euthanasia policy of the past has been abandoned for a more reasonable approach more recently.
There are two levels of quarantine zones to control the spread of the virus. The broader quarantine area is currently the entire county of Los Angeles and the western portions of San Bernardino and Riverside Counties. Within the broader quarantine zone are local “hot zones” around birds confirmed to have been infected.
The movement of poultry species is prevented within the broader quarantine area which covers all or most of the affected counties, but the movement of exotic birds that are not exposed to poultry is still permitted. This allows the pet trade and the aviary trade in psittacines, finches, and softbills to continue as long as they are not exposed to poultry.
A special CDFA permit to move exotic birds from facilities that also house poultry species within the broader quarantine zone can be acquired by applying with CDFA, reviewing facility biosecurity, and sample testing of the poultry at the facility for VND. This permit is only good for a month so testing to renew the permit must happen on a monthly basis. Currently, this permit is only available on a case-by-case basis and may not be processed quickly due to the limited CDFA resources available as personnel are concentrating on isolating ongoing VND outbreaks in the field.
The radius of the narrower hot zones is determined by local conditions and the number of birds in the infected flock and surrounding area. Hot zones are typically a radius of about 1 to 3 Kilometers or about a ½ mile to 2 miles. USDA and CDFA taskforce members will go door-to-door in a hot zone to notify bird owners of the situation and will take the required action described in the following paragraph. Additional taskforce members will intensify public outreach and education in areas surrounding any hot zones.
Within a hot zone, there is no movement of birds allowed. This includes exotic aviary birds and indoor pet birds. All poultry within a hot zone will be euthanized. If a person owns exotic birds within a hot-zone, the exotic birds will be put under strict quarantine in place and are tested for VND. As long as they test negative for the virus, they will not be euthanized, but they must remain where they are under quarantine until the hot zone is cleared of the virus.
It must be noted that the definition of poultry is very broad. It includes: all chickens, turkeys, turkins, pheasants, Peafowl, guinea fowl, quail, ducks, geese, swans, gallinules, doves, pigeons, grouse, partridges, francolin, tinamou, ostriches and other ratites. It also includes any hatching eggs of the above listed varieties. None of these types of birds can be moved off a premises if they are within the larger quarantine zone. Furthermore, if you keep exotics with any of these species on your property, you can’t move the exotic birds either. For example, if you only keep finches within the quarantine zone, you can sell them or move them from your property, but if you keep Button Quail too, it is then not permitted to move the finches according to the CDFA policy. All dove species are considered poultry so even if you keep only fruit doves, for example, they cannot be moved if they are within the larger quarantine zone, and they may be at risk of euthanasia if they fall within a hot zone. However, CDFA has shown a willingness to work with exotic bird owners to prevent unnecessary euthanasia and may allow testing instead of automatic euthanasia of these rarer and more expensive exotic poultry species. The current policy is an improvement over prior outbreaks, but there is certainly still some more work to be done to refine it further.
There are additional challenges to exotic bird sellers within or near the quarantine zones. When legally shipping non-poultry exotic birds out of the quarantine zone to another state, permission from the state veterinarian of the receiving state may be required. In most instances, the receiving state’s vet will deny permission. Even though the movement of the virus is specifically associated with the movement of fighting-cocks, the fear that an exotic bird could have a very remote chance to transmit the virus to another state is all it takes for the state vet to block the shipment. Airlines have also presented challenges out of fear of being liable for shipping infected birds into and out of the quarantine zone. Delta Airlines, for example, instituted an embargo on all bird shipments both into and out of all of southern California until USDA and CDFA clarified the policy to them. Thanks to USDA and CDFA efforts, Delta resumed accepting shipments of non-poultry birds a few days after their embargo was put in place.
At the time of writing this article (April 6, 2019), some isolated positive cases have been reported hundreds of miles away in northern California and in Arizona, so the quarantine zone could be expanded dramatically if additional cases occur. This has been a very fluid situation, but with the hot and dry summer season approaching, there is hope the outbreak can be contained and eliminated soon.
Here are the basics that every bird owner should understand:
VND can infect all types of birds, but it is most dangerous to chickens.
Thus far, the spread of VND is closely tied to the movement of fighting cocks.
The biggest method of infection, by far, is bird-to-bird contact with infected birds so avoid cock-fighting events or people who frequent them.
Chickens and other poultry should always be contained and not allowed to room freely which could allow them to encounter infected birds or droppings from neighboring collections.
Movements of wild birds are not a factor for carrying the VND virus to new locations.
Good biosecurity should always be in place to prevent the introduction of any diseases to your flock. At a minimum after returning home, spray shoes, clothing, and equipment with disinfectant or change shoes and clothing before having contact with your own birds.
A quarantine zone affects entire counties or large portions where movement of poultry is prohibited, but exotic or non-poultry species can be moved if they are not housed with poultry.
A hot zone is a narrow area around a positive case of VND where no birds can be moved, and all chickens and most poultry will be euthanized, but exotic, non-poultry birds will be put under strict quarantine and tested before determining if euthanasia is required.
CDFA and USDA have demonstrated a willingness to work with exotic bird owners to avoid unnecessary euthanasia and to allow the movement of non-poultry birds that are not within a small hot zone.
For current information on the Newcastle Outbreak, visit http://www.cdfa.ca.gov/ahfss/Animal_Health/Newcastle_Disease_Info.html or call the Sick Bird Hotline at 866-922-2473