Duck Plague, also known as Duck virus enteritis (DVE), is an acute, contagious disease caused by the herpesvirus, Anatid Herpesvirus 1 (AnHV-1). The severity of the disease depends on the virus strain and the resistance of the species of duck infected.
Duck plague is usually associated with sudden, high, persistent flock mortality during outbreaks. Duck plague causes hemorrhaging in the heart, liver, esophagus, and intestines and oral mucosal ulcers (often found under the tongue). Ducks which survive the infection may have scabs and scars in their mouth upon recovery. Common clinical signs observed in adult ducks include:
- Penile prolapse: Adult male ducks often die with a prolapsed penis.
- Weakness: Ducks often will be so weak that they are unable to stand or hold their head up. Drooped wings are also observed often.
- Diarrhea: Affected ducks often have bloody or greenish-watery diarrhea stained on their vents.
- Polydipsia: Increased water intake due to excessive thirst.
- Generalized illness signs: Lethargy, fever, reduced appetite, partially closed eyelids, light sensitivity, ruffled feathers, and depression.
- Sometimes affected ducks will be found dead, with the bird showing no clinical signs of sickness prior. This is especially the case with the more sensitive species, such as the Muscovy duck.
When young ducklings are affected (typically between 2 to 7 weeks of age), clinical signs most often observed include:
- Lacrimation (tearing eyes)
- Weight loss
- Bloody discharge from nares
- Blood-stained vent.
- Bloody fluid in mouth
- Blue colored beaks
How Duck Plague is Diagnosed
Duck plague is usually diagnosed from clinical signs which display blood present in the vent, nares or mouth. However, since many of the clinical signs appear similar to several other diseases, it will need to be differentiated from duck virus hepatitis, necrotic enteritis, lead poisoning, and pasteurellosis.
Duck plague is spread vertically (from breeding duck to the duckling hatching from the egg) or horizontally (through direct contact with an infected bird or indirectly from a contaminated environment). Wild migratory or free-ranging waterfowl are notoriously known to be silent carriers of the virus, often showing no clinical signs of infection. The disease is frequently seen when domestic and wild waterfowl come in contact with one another, such as in residential settings or urban ponds. Any ducks that recover from duck plague usually remain lifelong carriers, meaning they can shed the virus in their feces, exposing other birds to infection for several years after. The virus can survive for long periods in the environment.
In domestic ducks, the incubation period for duck plague ranges from 3 to 7 days. After initial clinical signs appear, most ducks will die within 1 to 5 days.
Risk Factors of Duck Plague
Duck plague outbreaks have been documented in both wild and domestic waterfowl worldwide, with the exception of Australia. Most outbreaks occur during the spring to early summer. Ducks of all ages are susceptible to duck plague, however it is most severe in adult ducks.