Fowlpox is a viral disease that commonly affects backyard chickens that have not been vaccinated. The disease is characterized by whitish blisters on the skin of the bird’s comb, wattles, and other areas, which later develop into dark scabs that take approximately three weeks to heal and drop off.
Although most birds survive the infection, very young or weak birds may succumb to the disease, and lesions in the mouth and throat can cause difficulty breathing and death. To prevent the disease, exhibition poultry breeders prefer to vaccinate their birds. The disease can also contain an integrated sequence from the Reticuloendotheliosis virus (REV), which is linked to the development of lymphoma in infected birds. Management of mosquito populations can help reduce outbreaks of fowlpox.
Fowl Pox Management in Chicken
Causes of Fowl Pox Disease
- An avipoxvirus in the Poxviridae family causes fowl pox. The virus is highly resistant and can survive in the environment for extended periods in dried scabs.
- Transmission of the virus usually occurs through contact with skin abrasions and the shedding of skin lesions (scabs) from recovering birds.
- Mosquitoes and other biting insects may also serve as mechanical vectors for transmission. Fowl pox can persist in multiple-age poultry complexes due to the slow spread of the virus and the availability of susceptible birds.
Disease Cycle of Fowl Pox
- The fowl pox virus is primarily transmitted to flocks through biting mosquitoes that have fed on infected birds.
- The virus can be transmitted to every uninfected bird on which the mosquito feeds. Once one bird is infected, the virus can spread to other flock members through scratches, broken skin, and mucous membranes, typically associated with fighting or pecking.
- The virus is highly resistant to dry scabs and can easily be transmitted to non-infected birds. The virus can infect birds through cuts and skin abrasions and is found in dried scabs, feathers, and skin dander. Birds of any age can become infected, and the disease can strike at any time of year.
Symptoms of Fowl Pox Disease
- There are two types of fowlpox: Drypox and Wetpox. Many birds have wart-like lumps in both forms, which is a reliable guide to diagnosis.
- The most common type is a dry pox, which manifests as fleshy pale lumps that enlarge and run together to form yellow crusts. In about a week, these scabs darken and fall off. Dry pox lesions are most common on the comb, wattle, and face, but they can appear on other body parts.
- On the other hand, wet pox manifests as ulcerous cheesy masses in the mouth, nose, and sometimes throat areas, which can obstruct eating and breathing. Birds with wet pox may become ill and, in some cases, die.
Diagnosis of Fowl Pox in Chicken
- Diagnosis of Fowl Pox in chickens can be made by observing characteristic gross and microscopic lesions in affected birds, such as fleshy pale lumps or ulcerous cheesy masses on the face, comb, and wattles, and the presence of eosinophilic cytoplasmic inclusion bodies visible with H&E staining, fluorescent antibody or immunohistochemical methods.
- The virus can also be isolated by inoculating the chorioallantoic membrane of developing chicken embryos or cell cultures of avian origin, and genomic profiles can be compared using restriction fragment length polymorphism or PCR amplification of virus-specific genomic fragments.
- The humoral immune response can be measured by ELISA, agar gel precipitation (AGP), or virus neutralization tests.
Treatment and Control of Fowl Pox Disease
- There is no treatment for fowl pox, so prevention through vaccination is key.
- Several vaccines are available for use in both backyard and commercial flocks. Vaccination can be done using the wing-stick or thigh-stick method, with the age and route of administration following the recommendations on the vaccine label.
- It’s important to check vaccinated birds for a “vaccination take” 7 to 10 days after administration. If lesions still occur in the flock, vaccinating when 20 percent or less of the birds show symptoms can help limit further damage.
- Additionally, controlling the spread of the disease can be done by isolating sick birds, practicing good biosecurity, and controlling mosquito populations.