Avian Influenza: A Global Disease
Avian influenza is a naturally occurring disease in birds and can infect poultry operations around the globe. It is very contagious and can spread rapidly throughout poultry flocks, with certain types causing high mortality rates and reductions in egg production and egg quality. During an outbreak of highly pathogenic avian influenza, infected flocks must be culled entirely.
Kateri Bertran Dols, Ph.D., a researcher from the Institute of Agrifood Research and Technology in Barcelona, gave a presentation during the Zinpro International Poultry Seminar that included a global update on avian influenza, risk factors for infection and what poultry producers can do to prevent outbreaks.
We sat down with her after her presentation to get more details on the disease and what we can do to reduce the likelihood of it getting into our poultry facilities.
Q&A with Kateri Bertran Dols, Ph.D.
Marco Rebollo: What are the different types of influenza and how are they different from each other?
Kateri Bertran Dols: The main difference between each type is what species it can infect. Influenza A, for example, infects birds and humans, while B infects only humans, C infects humans and swine and D can infect swine and cattle. Additionally, there are two subcategories of avian influenza: Low pathogenic avian influenza (LPAI) and highly pathogenic avian influenza (HPAI), based on their pathogenicity in chickens.
LPAI results in mild or no clinical signs along with little to no mortality. However, LPAI can result in a drop in egg production between 2% and 50% as well as a slight drop in egg quality. More importantly, LPAI can be exacerbated by other co-infections or environmental factors and can exacerbate other diseases as well.
HPAI on the other hand can be much more problematic for poultry producers, resulting in high mortality rates up to 100% and up to a 100% drop in egg production as well. A sharp reduction in egg quality is very typical if the reproductive tract of the bird becomes infected.
MR: What are the most common ways avian influenza can spread?
KBD: There are many ways avian influenza virus can spread from bird to bird, facility to facility and even country to country. Birds can become infected with avian influenza virus after coming into contact with the virus shed by another bird through their saliva, nasal discharge or feces.
The virus can also spread due to human-caused factors like poor biosecurity at poultry facilities. One example of this is trucks that transport feed or materials from one poultry facility to another. The tires can pick up the virus in the form of contaminated mud or manure and transport it to another facility. Workers on a poultry operation themselves can even spread the virus if they are going from facility to facility without changing or cleaning their clothes and boots.
There are studies that suggest that the wind can transport the virus through the air, but wild aquatic birds are what make the virus global. Ducks and geese can literally carry the virus across continents, in many cases without showing any signs of disease. Typically, the first introduction of the virus into poultry is through contact with LPAI viruses carried by wild aquatic birds, but the subsequent spread among farms is usually caused by human activity, with the risk that the LPAI virus mutates to its HPAI form.
MR: So, what can poultry producers do from a biosecurity standpoint to prevent the spread of avian influenza?
KBD: Biosecurity is the first line of defense against avian influenza. It’s important to make sure that everything that comes into a facility and leaves a facility is free of the virus, including the birds themselves and their feed.
Start by cleaning and disinfecting the poultry houses and using disinfected bedding. Clean and disinfect your water lines to keep the virus out of your birds’ drinking water. Regularly clean and disinfect trucks and wheels that will be coming and going from a facility so that the virus doesn’t spread that way.
Wear disposable clothing and boot covers and make sure to clean and disinfect your clothes and boots regularly so that you’re not tracking the virus from house to house.
In order to prevent primary introduction of the virus from wild aquatic birds, raise poultry in confinement or, if raised with outdoor access, confine birds during specific migration periods of wild aquatic birds.
MR: So, how about vaccines? What do producers need to know about them?
KBD: When elimination of infected poultry cannot control virus spread, vaccines can be a useful tool in a comprehensive avian influenza control program when used in combination with other disease control components. There are several properties that a vaccine must have for it to be effective against the virus it is administered to prevent. First of all, the vaccine strain must be genetically similar enough to the avian influenza strain that is circulating in the field. If the vaccine is not genetically similar enough, the birds will not build an immunity to that particular strain of avian influenza virus.
Another essential property for effective vaccines is the number of vaccinations applied; the birds need to be receiving enough of the vaccine antigen to stimulate their immune systems and prevent illness and death as well as reduce virus replication and shedding into the environment. Not only does a single dose need to be strong enough, but you also need to make sure you’re vaccinating the birds enough times. Many birds will need to be vaccinated two or three times at different points in their lives. A single dose may not be enough to protect them from the virus through their entire lives. The number of vaccinations needed will depend on several factors, such as the infection pressure in a particular geographic area, the poultry type or the length of the production cycle.
Performance Trace Minerals Can Help To Prevent/Mitigate Avian Influenza Virus Infection
Supplementing poultry diets with zinc from Availa®Zn and manganese from Availa®Mn helps to provide a rapid and robust inflammatory response to immune challenges. They also provide support to epithelial barriers in the airways and improved their healing process limiting the access and multiplication of pathogens. Feeding zinc and manganese from performance trace minerals has shown to increase the effectiveness of vaccinations in young birds, particularly in antibiotic-free production.