Marek's disease: Difference between revisions

Latest revision as of 06:52, 16 February 2025

A viral disease affecting chickens

Marek's disease is a highly contagious viral disease in chickens caused by an alphaherpesvirus known as Gallid alphaherpesvirus 2. It is characterized by the presence of lymphomas, immunosuppression, and neurological symptoms. The disease is named after the Hungarian veterinarian József Marek, who first described the condition in 1907.

Virology[edit]

Marek's disease is caused by a herpesvirus that primarily affects chickens, although it can also infect other poultry species. The virus is classified into three serotypes:

Serotype 1: Oncogenic strains that cause the disease.
Serotype 2: Non-oncogenic strains found in chickens.
Serotype 3: Non-oncogenic strains found in turkeys.

The virus is transmitted through aerosols and fomites, with infected birds shedding the virus in feather dander.

Pathogenesis[edit]

The pathogenesis of Marek's disease involves several stages:

Early infection: The virus infects the respiratory tract and spreads to lymphoid tissue.
Latent infection: The virus establishes latency in T cells.
Reactivation: The virus reactivates, leading to lymphoproliferative disease.

Clinical Signs[edit]

Clinical signs of Marek's disease vary depending on the form of the disease:

Neurological form: Paralysis, ataxia, and torticollis.
Visceral form: Tumors in organs such as the liver, spleen, and kidneys.
Ocular form: Changes in the iris leading to "gray eye" or ocular Marek's disease.
Cutaneous form: Nodular lesions on the skin.

Diagnosis[edit]

Diagnosis of Marek's disease is based on clinical signs, histopathology, and polymerase chain reaction (PCR) testing. The presence of lymphoid tumors and enlarged nerves are indicative of the disease.

Prevention and Control[edit]

The primary method of controlling Marek's disease is through vaccination. Vaccines are typically administered to day-old chicks and provide protection against the oncogenic strains of the virus. Good biosecurity practices are also essential to prevent the spread of the virus.

Related pages[edit]

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-'''Marek's Disease''' is a highly contagious viral disease affecting domestic chickens and other bird species. It is caused by the Marek's disease virus (MDV), a herpesvirus, which can lead to tumors and paralysis in affected birds. The disease is named after Józef Marek, who first described it in 1907. Marek's disease poses a significant threat to poultry production worldwide, leading to economic losses due to mortality, reduced productivity, and the costs associated with control measures.
+{{Short description|A viral disease affecting chickens}}
+{{Use dmy dates|date=October 2023}}
-==Etiology==
+'''Marek's disease''' is a highly contagious viral disease in chickens caused by an [[alphaherpesvirus]] known as ''[[Gallid alphaherpesvirus 2]]''. It is characterized by the presence of [[lymphoma]]s, [[immunosuppression]], and [[neurological]] symptoms. The disease is named after the Hungarian veterinarian [[József Marek]], who first described the condition in 1907.
-Marek's disease is caused by the Marek's disease virus (MDV), which belongs to the genus ''[[Mardivirus]]'' within the family ''[[Herpesviridae]]''. There are several strains of the virus, varying in virulence. The virus is highly contagious and is spread through feather follicle dander, which can be inhaled by susceptible birds. Once infected, the virus targets the immune system, leading to immunosuppression and making the birds more susceptible to other diseases.
+==Virology==
+Marek's disease is caused by a [[herpesvirus]] that primarily affects [[chickens]], although it can also infect other [[poultry]] species. The virus is classified into three serotypes:
+* '''Serotype 1''': Oncogenic strains that cause the disease.
+* '''Serotype 2''': Non-oncogenic strains found in chickens.
+* '''Serotype 3''': Non-oncogenic strains found in turkeys.
+The virus is transmitted through [[aerosol]]s and [[fomites]], with infected birds shedding the virus in [[feather dander]].
+==Pathogenesis==
+The pathogenesis of Marek's disease involves several stages:
+* '''Early infection''': The virus infects the [[respiratory tract]] and spreads to [[lymphoid tissue]].
+* '''Latent infection''': The virus establishes latency in [[T cells]].
+* '''Reactivation''': The virus reactivates, leading to [[lymphoproliferative]] disease.
 ==Clinical Signs==
-The clinical signs of Marek's disease can vary depending on the strain of the virus, the age of the birds, and their immune status. Common signs include:
+[[File:Ocular_Marek's_disease.jpg|thumb|right|Ocular Marek's disease showing irregular pupil shape and color changes.]]
-* Paralysis of the legs, wings, and neck
+Clinical signs of Marek's disease vary depending on the form of the disease:
-* Weight loss and reduced growth
+* '''Neurological form''': Paralysis, ataxia, and [[torticollis]].
-* Irregularly shaped pupils or blindness
+* '''Visceral form''': Tumors in organs such as the [[liver]], [[spleen]], and [[kidneys]].
-* Tumors in various organs, including the liver, spleen, and heart
+* '''Ocular form''': Changes in the [[iris]] leading to "gray eye" or [[ocular Marek's disease]].
-* Difficulty breathing
+* '''Cutaneous form''': Nodular lesions on the skin.
 ==Diagnosis==
-Diagnosis of Marek's disease is based on clinical signs, post-mortem findings, and laboratory tests. Histopathology can reveal the presence of lymphoid tumors in various organs. Polymerase chain reaction (PCR) tests can detect MDV DNA in blood, feathers, and tissues, providing a definitive diagnosis.
+Diagnosis of Marek's disease is based on clinical signs, [[histopathology]], and [[polymerase chain reaction]] (PCR) testing. The presence of [[lymphoid tumors]] and [[enlarged nerves]] are indicative of the disease.
 ==Prevention and Control==
-Vaccination is the primary method for controlling Marek's disease. Vaccines are typically administered to chicks at one day of age, either in ovo (in the egg) or subcutaneously. Good biosecurity practices, including maintaining a clean environment and minimizing stress, can also help reduce the risk of disease spread. It is important to note that while vaccination can prevent the development of clinical disease, it does not prevent infection with the virus or shedding of the virus to other birds.
+The primary method of controlling Marek's disease is through [[vaccination]]. Vaccines are typically administered to [[day-old chicks]] and provide protection against the oncogenic strains of the virus. Good [[biosecurity]] practices are also essential to prevent the spread of the virus.
-==Treatment==
-There is no treatment for Marek's disease. Management practices focus on prevention through vaccination and biosecurity measures to reduce the spread of the virus.
-==Economic Impact==
+==Related pages==
-Marek's disease represents a significant economic burden to the poultry industry due to mortality, reduced productivity, and the costs associated with vaccination and biosecurity measures. The disease underscores the importance of ongoing research and development of more effective vaccines and control strategies.
+* [[Avian diseases]]
+* [[Herpesviridae]]
+* [[Vaccination in poultry]]
-==Research==
-Research on Marek's disease continues to focus on understanding the virus's pathogenesis, improving diagnostic methods, and developing more effective vaccines. Studies on the genetic resistance of chickens to MDV are also underway, which may lead to the breeding of resistant poultry strains.
-[[Category:Animal viral diseases]]
 [[Category:Poultry diseases]]
-[[Category:Herpesviridae]]
+[[Category:Viral diseases]]
+[[Category:Herpesviridae infections]]
-{{Virus-stub}}