Fowl Pox & Marek’s Disease in Poultry: Causes & Prevention

Fowl Pox (Avian Pox)

Fowl pox is a viral disease in poultry caused by the avipox virus, which can be transmitted through mosquito bites. It primarily affects domestic birds like chickens, turkeys, and pigeons. The disease is characterized by eruptions and scab-like lesions on the skin, combs, wattles, and inside the mouth.

There are two forms of fowl pox: the dry form and the diphtheritic (wet) form. The dry form presents as blisters and scabby bumps on the skin, while the wet form causes cheesy patches in the mouth, air passages, and eyes, leading to difficulty in eating and breathing. The wet form is more severe and can be fatal.

Causes of Fowl Pox

Fowl pox is caused by different strains of the poxvirus, each with specificities for various bird species and different levels of pathogenicity.

Transmission of the Disease

Fowl pox spreads slowly within a flock, with an incubation period of around 10 days. It can be transmitted through direct contact between infected and non-infected birds, as well as through mechanical means. Infection can occur through intact or lacerated skin, with the latter being the most common route.

Carrier birds can also spread the virus. Insects like ticks, lice, mosquitoes, and flies can act as vectors and transmit the disease. Poor sanitation practices can contribute to the spread of the virus.

Clinical Signs

All breeds of birds are susceptible to fowl pox, but males of light breeds with large combs are more vulnerable. The incubation period typically ranges from 4 to 10 days, and the age commonly affected is 5 to 10 months. The virus can remain viable in dry scabs for an extended period.

Control and Prevention of Fowl Pox

There is no specific treatment for fowl pox, so the focus is on good management practices to reduce stress in infected flocks. In an outbreak, affected birds should be culled and disposed of properly. Vaccination is an essential measure in controlling the spread of the disease.

The live pigeon pox virus vaccine protects for 6 months, while the live fowlpox virus vaccine offers longer immunity. Vaccination is typically done at 3 months of age using the wing web method. Controlling cannibalism in the flock can also help reduce the transmission of the pox virus.

Marek's Disease (Fowl Paralysis)

Marek's disease is a viral infection in poultry caused by the chicken herpes virus. It primarily affects mature birds from 12 weeks of age, although chicks can also be susceptible. Marek's disease causes a wide range of symptoms and can lead to significant losses in a flock.

Clinical Signs

Marek's disease commonly affects chickens between the ages of 12 to 24 weeks, but cases have been reported in birds as young as 6 weeks and older than 24 weeks. The disease can manifest in various ways, affecting the eyes, nerves, internal organs, bones, and blood.

Birds may show signs of depression, paralysis, loss of appetite, anemia (pale combs), and dehydration. The mortality rate ranges from 10 to 30%, while morbidity can reach up to 80%.

Transmission of Marek's Disease

Marek's disease is mainly transmitted through inhaling virus-laden dander. Spread occurs through direct or indirect contact. Young chicks are particularly susceptible to horizontal transmission, but their susceptibility decreases rapidly after the first few days of age. The virus can persist in dust, feces, and saliva.

Diagnosis and Treatment

Diagnosing Marek's disease involves observing clinical signs, performing post-mortem examinations, and conducting histopathology to confirm the presence of tumors and paralysis. There is no specific treatment for Marek's disease. Chicks are typically vaccinated at the hatchery to prevent tumor formation, but the vaccine does not prevent viral infection itself.

Control and Prevention of Marek's Disease

Isolating growing chickens from potential sources of infection is an important preventive measure. Vaccination is the most effective approach to controlling Marek's disease.

The vaccine is usually administered on day one or injected into the embryo three days before hatching. Vaccinated birds are protected for life.

In regions where Marek's disease is prevalent, a polyvalent vaccine containing multiple serotypes is often used. Using genetically resistant stock and implementing an all-in-all-out system to break the infection cycle can also help control the disease.

Additionally, thorough cleaning and disinfection practices should be followed.

Note: Marek's disease should not be confused with lymphoid leucosis, although both are viral diseases. Marek's disease typically affects chickens aged 12 to 25 weeks, while lymphoid leucosis usually starts at 16 weeks of age. In lymphoid leucosis, affected birds progressively lose weight, show weakness, and have diarrhea. Virus isolation can be performed to confirm the diagnosis of lymphoid leucosis.

Conclusion

In conclusion, understanding and effectively managing viral diseases in poultry, such as Fowl Pox and Marek's disease, is essential for maintaining the health and productivity of your flock. Fowl Pox, characterized by skin lesions and diphtheritic symptoms, can be controlled through good sanitation practices and vaccination. On the other hand, Marek's disease, with its various debilitating symptoms, calls for strict biosecurity measures, vaccination, and the use of genetically resistant stock.

By implementing preventive measures, such as vaccination, isolation, and proper hygiene protocols, poultry farmers can minimize the impact of these diseases on their flocks. Regular monitoring, prompt diagnosis, and appropriate action are crucial for early intervention and disease management.