Chickens die en mass in Southern Vietnam, bird flu ruled out

[hawkeye]

Chickens die en mass in Southern Vietnam, bird flu ruled out

05:44' 26/11/2007 (GMT+7)

VietNamNet Bridge - Over 50,000 chickens in southern Vietnam's Tien Giang province have been dying en mass, probably from Marek?s disease.

The fowls, mostly in Cho Gao district, died after manifesting drooping eyelids, lethargy, limping and loss of appetite. A number of chickens in Chau Thanh district have also died.

They could probably have been struck by Marek, a highly contagious viral neoplastic disease in chickens caused by herpes virus, said Le Minh Khanh, deputy head of the province?s Animal Health Department.

Marek?s disease cannot be cured but only prevented, he added.

He attributed the disease?s spread to unhygienic conditions and cramped space where the fowls are raised.

Recently, chicken prices have been rising, prompting locals to cramp more and more chickens into small quarters for better profit, which inadvertently worsened the situation, he elaborated.

But he assured Sai Gon Giai Phong yesterday that no sign of H5N1 - a deadly bird flu strain ? has been found.

Phung Van An of Cho Gao?s Luong Hoa Lac commune who was raising 50,000 chickens has in the past days seen over 30,000 die and the remaining still keep on dying. He has lost around VND1 billion (US$62,500).

?Those 4 or 4.5 months old die more quickly?, An lamented.

Similarly, over 700 chickens of a 1,000-strong stock belonging to Nguyen Thanh Nguyen have died, dealing him a loss of over VND40 million. His neighbor, Doan Tan Du has recently lost over 800 chickens.

In Phu Kiet commune, the situation fares no better.

Hai Tuan, a veteran chicken breeder there, said he has never seen any such massive deaths, ?even during the times the H5N1 epidemic was breaking out?.

Meanwhile, Long An province nearby yesterday reported similar chicken deaths. Local authorities are investigating.

Such incidents have scared the public into suspecting bird flu has recurred in the southern region. Since outbreaks in December 2003, the avian influenza has killed and led to the forced culling of dozens of millions of fowls in Viet Nam.

 

[hawkeye]

Vietnam: More chickens die in southern provinces

Vietnam: More chickens die in southern provinces

More chickens die in southern provinces
08:46' 26/11/2007 (GMT+7)

VietNamNet Bridge - A recent report notified that the number of chickens dying of a new visceral disease has been alarmingly on the rise.

Nguyen Thi Thanh Hoa of the Luong Hoa Lac Commune in Cho Gao District, reports that 300 chickens die daily and the remaining still keep on dying. The report also estimated that a total of approximately 38,000 chickens in Cho Gao District have been dying on mass.

A large number of chickens in Long An Province have also been dying. Nguyen Van Thanh of Hamlet 2 in Binh Tan Commune, Tan An Town had about 800 live chickens. In the few past days, he has been totally desperate as the number of chickens dying has been escalating.

The infected symptoms occur in the chickens from about 3 months old of age. The chickens then die after a loss of appetite, contraction of muscle manifesting to limping, his wife reported.

Lumps were found in the lungs and livers of dying chickens, and it has been speculated that it is likely to be Marek?s disease that has caused this, scientific experts have reported.

They also have found that the source of the infected chickens originally came from the Charoen PoKphand Group (CP Group), the Viet Nam Branch.

 

[hawkeye]

Re: Chickens die en mass in Southern Vietnam, bird flu ruled out

Marek's Disease (Visceral Leukosis)

Definition/Introduction:

Marek's disease (MD) is one of the most common lymphoproliferative diseases of chickens which causes mononuclear infiltration of one or more of the following cells: peripheral nerves, gonad, iris, muscle, viscera, and skin. MD has been called by several names including "range paralysis", "neural lymphoma" and "skin leucosis".

Causative Organism: MD is caused by herpesvirus, which can be differentiated from other lymphoid neoplastic diseases. There are three serotypes of MDV which have many common antigens and are distinguished by serologic tests.


Pathogenesis: There are four phases of infection: 1) degenerative changes caused by early productive-restrictive virus infection, 2) latent infection, 3) another phase of cytolytic infection associated with permanent immunosuppression, and 4) nonproductive infected lymphoid cells that may or may not progress to lymphoma formation, a "proliferative" phase. The route of infection is inhalation. The virus then replicates in the lungs (in non-lymphoid cells). An acute phase of the disease can be seen within 72-96 hours where the lymphoid system, primarily bursa and thymus, undergoes cytolytic changes. Infected birds normally recover from the acute phase of the infection after 6-7 days and become latent. Infected lymphocytes carry the virus throughout the body, causing cell-associated viremia. Eventually, virus will be shed in the environment via feather debris and dander after the secondary cytolytic infection occurs in the feather follicle epithelium (~2 weeks post infection).

Transmission: MDV can be transmitted by direct and indirect contact between birds. Transmission is primarily by airborne route as the virus is shed in epithelial cells of the feather follicle, dander, chicken house dust, feces and saliva. The virus has a long survival time in dander since viable virus has been isolated from houses that have been depopulated for many months. (Historically, prior to vaccine availability, control in broilers was based upon early brooding exposure to used broiler litter and dander, marketing survivors versus poorer results with the thoroughly cleaned and disinfected brooder houses). Transmission by egg has no significance (i.e., chicken hatched and reared in isolation will be free of MDV.

Clinical signs: MD commonly affects pullets between 12-24 weeks of age, but can infect broilers as early as 6 weeks of age. The incubation period ranges from 3-4 weeks to several months. Signs may vary according to the nerve or nerves affected. Asymmetric progressive paralysis of one or more of the extremities can be seen. Wing involvement is characterized by drooping of the limb. Torticollis of nerves controlling the neck are affected. Vagal involvement will lead to dilatation of the crop and/or gasping. If the iris is involved, eyes will lose their ability to accommodate light intensity and blindness may occur (once called "grey eye"). Many birds die suddenly without symptoms. There are nonspecific signs such as weight loss, paleness, anorexia, and diarrhea.

Pathology: Macroscopic lesions: Nerve lesions can be seen as grayish, edematous, two or three times the normal thickness, and loss of the normal striated white glistening appearance. Nerves commonly affected include the brachial and sciatic plexi, celiac plexus, abdominal vagus and intercostals nerves. Nerve enlargement may not always be seen in affected birds at necropsy, although characteristic lesions may be found histologically. Also, tumors such as lymphoma occur in the ovary along with the nerve lesions. Macroscopic appearance in affected viscera, with the exception of the bursa of Fabricius, are indistinguishable from leukotic lesions induced by other agents (e.g. lymphoid leucosis virus). Organs are enlarged with diffuse grayish discoloration...