Field Diagnostics for Highly Pathogenic Avian Influenza, a timely reminder

Aug 15, 2016

This Information is provided by John Roberts, DVM, DACVP. Dr Roberts is the Avian Patholgist & Diagnostic Specialist, at the Thompson-Bishop-Sparks State Diagnostic Laboratory, Auburn, AL

Migratory waterfowl, shore birds and domestic ducks are reservoirs for Avian Influenza (AI) and can harbor and transmit AI without becoming sick. Over the last several years, there have been cases of avian influenza crossing from wild water fowl to domestic poultry. Avian Influenza in birds is characterized as either Low or High pathogenic, and applies only to bird populations. High Pathogenic Avian influenza (HPAI) originated in Asia and entered the wild bird populations in the Pacific flyway of the Northwest United States in during 2014. During the winter 2014/2015 the virus spilled over into domestic flocks causing die-offs in pet guinea fowl in Oregon, commercial chickens in British Columbia, Canada and commercial turkeys in California.  Although avian influenza virus (AI) has the potential to mutate and infect humans, the Center for Disease Control (CDC) considers the risk of human infection, this is a very rare event. The North American HPAI strain identified in 2014 possess a high risk to chickens, turkeys, pheasants, quail, ducks, geese and guinea fowl, as well as a wide variety of other wild and pet birds. Migratory waterfowl, shore birds and domestic ducks are reservoirs for AI and can harbor and transmit AI without becoming sick. The Alabama poultry industry employs over 75,000 people generating about 10 billion dollars annually. An outbreak of HPAI could result in a loss of billions of dollars to the Alabama poultry sector and this would have a ripple effect in other parts of the state’s economy. Thankfully, the commercial poultry industry operates under standards dictated by the National Poultry Improvement Plan (NPIP) and conducts routine monitoring for AI.  The greatest risk to the industry, however is AI amplification in wild waterfowl and backyard flocks.  Public awareness of AI will greatly increase the probability for rapid detection and anyone observing suspicious bird sickness or death in any avian species should contact state or federal authorities.

If you observe sick or dead poultry caused by AI there are certain precautions that should be followed. Skin to skin contact and direct inhalation of air born particles from sick or dead poultry or migratory water fowl should be avoided. Carefully placing dead poultry into a plastic bag (by inversion of the bag), then double bagging with a clean bag followed by immediate transfer to a diagnostic lab this is preferred. If transportation will be delayed it is best to place double-bagged carcass in a container with ice. After handling sick or dead poultry whether direct contact occurs or not, wash your hands with soap and water, shower and change clothing before having any contact with healthy domestic poultry or other birds. In Alabama, you can contact your state veterinarian office (334) 240-7253 or nearest Alabama, Dept of Agriculture and Industries, diagnostic lab (Thompson-Bishop-Sparks, Auburn 334-844-4987, Mitchem-Sparks, Boaz 256-593-2995, J.B.Taylor, Elba 334-897-6340,  Hinton-Mitchem, Hanceville 256-352-8036) to obtain information regarding carcass delivery. Accredited veterinarians or trained wildlife officials may be eligible to submit swab samples or serum for AI testing provided they contact the state diagnostic system and receive approval and sample preparation instructions and supplies. Only swabs of the pharyngeal region (roof of mouth) with Dacron swabs transported in sealed vials of blood heart infusion broth (BHI-broth) are accepted for molecular testing of poultry.

The Alabama Department of Agriculture and Industries, state diagnostic laboratory system preforms preliminary test for AI, but final confirmation of a positive AI-test will only be given after samples are double-checked by the National Veterinary Services Laboratory (NVSL) of Animal Plant Health Inspection Service (APHIS) in Ames Iowa. All samples entering the federal diagnostic system must be submitted by an authorized agency and this includes all Alabama state diagnostic labs and federal field veterinary officers. Screening and surveillance for AI in healthy or subclinical flocks is accomplished by detection of AI serum antibodies using enzyme-linked immunosorbent assay (ELISA) and then confirmed with Agar Gel Immunodiffusion (AGID) testing of serum. Samples identified as AI-positive with AGID are deemed inconclusive until they are double checked by NVSL. All AI-positive serum samples are followed up with farm visits from regulatory personnel to include additional serum sampling and PCR swabs of live birds. Although the Al State Diagnostic lab system performs many tests on domestic animal diseases, the scientist there still conduct over 200,000 diagnostic tests for the detection of Avian Influenza each year. 

In naïve poultry populations, HPAI is expected to cause sudden onset of disease with high death rates. Mortality may reach as high as 100% within 48 hours has been observed. Sick birds may exhibit open mouth breathing, ruffled feathers, severe depression or neurologic disease. The comb, wattles and facial subcutaneous tissue maybe have hemorrhage, edema, reddening or cyanosis. Facial edema is often most pronounced in eyelid and tissue surrounding eye. The shank and feet may be reddened with multifocal subcutaneous hemorrhage.  Necropsy of birds with these external lesions should be conducted under a ventilated hood at a diagnostic facility. AI is spread by exposure of poultry to migratory waterfowl. International movement of poultry, poultry equipment, and people pose additional risks for further introduction of AI into U.S. poultry. Once introduced, the disease can be spread from bird to bird by direct contact. Influenza viruses can also be spread by manure, equipment, vehicles, egg flats, crates, clothing and shoes. AI may also travel from farm to farm on dust particle picked up in the wind. AI viruses can remain viable at moderate temperatures for long periods in the environment and can survive indefinitely in frozen material. Biosecurity of backyard poultry flocks is the best defense we have for AI and other poultry disease. Additional information on biosecurity for backyard flocks can be found at healthy birds.aphis.usda.gov. 
We all must to work together (poultry producers, backyard flock owners, veterinarians, etc) to report large numbers of sick poultry, low egg production, poultry deaths to the State of Alabama Dept of Agriculture & Industries or one of it's 4 Diagnostic labs.