Virulent Newcastle Disease Can Kill Your Backyard Flock
June 2020 Update: When I originally wrote this post in January 2019 Virulent Newcastle Disease, a devastating and lethal poultry disease, had been epidemic in the backyard flocks of Southern California since May 2018. Here's really good news: The California Department of Food and Agriculture and the USDA announced on June 1, 2020 that the Virulent Newcastle Disease quarantine has come to an end! After rigorous testing, no new cases were detected. CDFA Secretary Karen Ross announced “We have eagerly anticipated this day and are extremely proud of the tireless work of the Virulent Newcastle Disease Task Force. While we extend gratitude to the hundreds of dedicated and skilled USDA, CDFA and California Animal Health and Food Safety Laboratory System employees who worked for over two years to achieve this goal, often in adverse conditions, we also want to thank the thousands of poultry owners in Southern California who made the sacrifices and investments needed to eradicate this virus from California.” To Karen Ross’s statement I will add this: As I write this vND update in June 2020, the world is in the midst of the COVID-19 pandemic. The California vND experience has shown us that with vigilance viruses can be eradicated, epidemics can end, and life can return to normal.
The skull and crossbones (public domain) originated in Europe in the Late Middle Ages as a symbol of death. Here, it is superimposed over a photomicrograph of NDV in the conjunctiva of a chicken (CSIRO Scienceimage).
Back in May of 2018, backyard chickens in Los Angeles County, California began to die – first in one backyard, then in another, then in many, many more. It was the beginning of the spread of a terrible scourge known as Virulent Newcastle Disease (vND), a contagious and deadly viral disease that affects birds. By August the disease had spread to San Bernardino, Riverside, and Ventura Counties resulting in the deaths of 9000 chickens, all from backyard flocks. By January 2019, in spite of the heroic efforts by staff of the US Department of Agriculture and the California Department of Food and Agriculture, vND continued to spread through the backyard flocks southern California and had also found its way into large commercial flocks. When vND is discovered in a flock, since there’s no effective treatment, and since it is so virulent, the entire flock must be euthanized. In an effort to stop the spread of the disease, the California State Veterinarian mandated that chickens in certain designated areas be euthanized even if they had previously tested negative for the disease. While this step makes sense epidemiologically, it is, without question, devastating on a personal level.
Newcastle Disease is endemic around the world, but until this outbreak, there have been no cases in the US since 2003 due to stringent import restrictions and the policy of destroying infected flocks. It is a disease that needs to be battled forcefully and with every weapon our public health veterinarians have in their arsenal. The 2002-2003 outbreak, which also started in California but eventually spread to Arizona, Nevada, and Texas, led to the loss of 3.16 million birds, cost 161 million dollars, and produced incalculable sorrow and grief.
What causes this disease? How is it spread? What are its symptoms? What should you do if you think your chickens are dying from this disease? What can you do to protect your flock? After some research, here are my best answers to these questions, and also some resources where you can find more information.
What is Newcastle Disease?
The first described outbreak of Newcastle Disease occurred in Indonesia in 1926. A year later, an outbreak occurred in Newcastle-upon-Tyne, England, and it was from that outbreak that the disease took its name. Newcastle Disease is caused by a virus that is part of a family of viruses called the paramyxoviruses, which includes the viruses that cause both measles and mumps. Within the family of paramyxoviruses, there are a group of 15 viruses (APMV-1 to APMV-15), called the avulaviruses, that cause disease only in birds. One of them, avian avulavirus 1 (APMV-1), is the virus that causes Newcastle Disease. For simplicity this virus is usually just referred to as NDV—Newcastle Disease Virus.
Because NDV mutates easily, there is continuous evolution of new strains and it is difficult to put an accurate number how many strains exist. From the perspective of the disease, the various strains are pigeon-holed into three groups—velogenic (highly virulent strains that are usually lethal), mesogenic (moderately virulent strains that cause coughing, illness, and are 10% lethal), or lentogenic (nonvirulent strains that cause little or no symptoms and are hardly ever lethal). This virulence-based pigeon-holing has been even further simplified for the purposes of reporting the disease to veterinary health authorities. Lentogenic, low-virulence strains are not reportable. Velogenic and mesogenic strains have been lumped together and are called Virulent Newcastle Disease Viruses (vNDV). So, the strain of NDV that is devastating California as I write this is called Virulent Newcastle Disease because it is so very lethal.
How is Newcastle Disease Spread?
The nasal secretions and poop of sick birds are loaded with virus. Uninfected birds can become infected by coming in contact with poop or secretions directly or by being exposed to food, water, or objects that have been contaminated—poultry equipment and litter are the main methods of virus transfer between flocks. People can also spread virus from flock to flock on their clothes or shoes or even the tires on their cars. The virus can stay viable in the environment for several weeks, especially in warm and humid weather. If the virus is frozen it can survive indefinitely.
NDV infects many wild bird species and both pigeons and double-crested cormorants have been shown to be reservoirs for vNDV in North America. Parrots smuggled into the US from South America, where vNDV is endemic, are a potential means for the virus to enter the country. Parrots are asymptomatic carriers of NDV and if they are infected can shed virus for well over a year.
What are the symptoms of Newcastle Disease in chickens?
Newcastle Disease may have such a sudden onset that the first sign of disease is death – with no prior symptoms. Other key symptoms can include:
Respiratory—gasping for air, coughing, nasal discharge
Nervous—tremors, paralysis of legs or wings, neck twisting
Swelling—especially around the eyes and in the neck
Gastrointestinal—watery, green diarrhea
Eggs—thin-shelled eggs and a sudden, partial to complete drop in egg production
Keep in mind that the listed symptoms are also symptoms of other diseases. So, look at the big picture, and if you have any concern that your flock is infected with NDV, call a vet, or contact the appropriate animal health officials in your state (see the contact information below.)
What should I do if I think my flock has Newcastle Disease?
If a number of your chickens die very suddenly, or if you see a combination of symptoms that match the description in the previous section, you need to take action. The sad reality is that there is nothing you can do to treat Newcastle Disease. And in addition, if any of your chickens are diagnosed with Newcastle Disease, the rest of the flock will have to be euthanized. Still, you need to act quickly to stop this devastating disease from spreading to other flocks.
Call your vet if you have one. Your vet will undertake the necessary diagnostic and reporting steps.
If you live in California, where the current outbreak continues, call the Sick Bird Hotline: 866-922-BIRD (2473). You can find a link to information about the ongoing California outbreak here.
If you live in the US but not in California, you can find the contact information for the animal health official in your state here.
You can contact the US Dept. of Agriculture at 866-536-7593. You can find information from the current outbreak here.
How can I protect my flock?
Since there is no cure for vND, the only strategy is prevention, and sadly, no prevention strategy will provide a 100% guarantee that your flock will be safe from vND. But here’s what we’ve got:
Vaccination:
ND vaccines have been around since the 1950’s. Current vaccines are not perfect, but may aid in the prevention of disease. A type B1 vaccine is made by Zoetis and is available on-line from Valley Vet Supply or Jeffers. The good news is that you don’t need needles to administer this vaccine—it can go right into the water supply! Unfortunately, since NDV mutates and evolves so rapidly, there is no way to be sure that any given vaccine will be effective against every new strain that comes along. The proof that vaccines are not entirely effective can be seen in the fact that while ND vaccines are used around the world, ND is still endemic globally—outbreaks are reported in dozens of countries every year, and it is probably under-reported. Research is being conducted on new and better ND vaccines—you can find a full discussion in this 2017 Veterinary Microbiology article, “Newcastle disease vaccines—A solved problem or a continuous challenge?” Until those new vaccines are developed we are left with our current strategy, of less-than-perfect vaccines, combined with a national strategy of depopulation (euthanasia) of infected flocks and import restrictions. And an equally critical practice that must be carried out by individual flock-keepers: Biosecurity.
Biosecurity:
The advice I wrote about biosecurity in my recent post about Marek’s Disease is completely pertinent to ND as well so I’m repeating it here with a few modifications: Commercial chicken operations with hundreds of thousands of chickens at one location rarely let outsiders onto the premises and those who absolutely need to enter the facility are often garbed in Tyvek suits and boots and nitrile gloves. They take biosecurity very seriously. Backyard chicken folks take biosecurity not so seriously. Neighbors meander in and out—some of those neighbors have chickens of their own. When the chicken owners go on vacation, the chicken sitter comes, and that chicken sitter may be traveling in and out of several other coops on any given day. There are coop tours where large groups of people wander from coop to coop. Chicken folks go to the chicken barn at the fair and then come home and tend their flocks. They go to swap meets and bring home chickens from strange flocks. All of these activities can transmit disease. If you’re serious about using biosecurity to protect your flock, you need to enact strict rules and you need to enforce those rules:
Don’t visit other coops.
Don’t allow any unnecessary people near your chickens or in your coop.
If you must allow a caregiver or someone else in your coop, and they’ve been in contact with another coop or flock, make sure that they’ve showered and changed clothes before visiting your coop.
Do NOT attend coop tours, don't enter poultry barns at the fair, don't go to swap meets or anywhere else where there are live chickens.
If you introduce new birds to your flock, quarantine the new bird for at least four weeks.
I’ll be the first to say that these rules are stringent. I don’t know anybody that strictly follows every rule. I know I don’t. But I should.
The USDA has a robust on-line resource center on biosecurity called “Defend the Flock.” I urge you to take a look at that and think about how you can best implement the suggestions.
Finally, bear in mind that while there’s an active outbreak in California, this disease doesn’t exist in the US most of the time, thanks to stringent government-mandated reporting and controls. Nevertheless, be vigilant, and if we all do likewise we have a good chance of holding this terrible disease at bay and away from our coops.
