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Bird flu virus H5N1 infection in laying Hens.

Clinical and pathological symptoms due to avian influenza virus infection vary widely, some clinical symptoms and pathologic lesions are sometimes similar to other diseases. The severity of clinical symptoms and lesions is highly dependent on the level of immunity, the type of virus that infects and the type of poultry.

Currently, in all laying chicken farms have been done vaccinations against bird flu (avian influenza). The results of vaccination are very good on farms with a strict vaccination program. However, on farms with weak vaccination programs and poor biosecurity management, avian flu cases are still common. The mortality rate of chickens is not as high as in non-vaccinated farms. The severity of clinical symptoms and pathological lesions is also different. Below are some symptoms of avian influenza by H5N1 virus.

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Bird Flu Symptoms, avian influenza in Chicken

Chicken suffers from depression, swollen face, cyanosis. This at a glance is a severe clinical symptom. A swollen face is a symptom of avian influenza H5N1 in laying chickens, but only a few chickens show cyanosis on the face like this. Cyanosis on the face, in broiler more easily found this symptom or in adult chickens with very low immunity or no immunity at all.  But the most common clinical symptoms in laying hens are severe depression, no respiratory symptoms, or with mild respiratory symptoms, no swollen face, and sudden death in peracute cases.

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avian influenza

Chicken showed neurological symptoms. Torticollis often found in some chickens that survived the acute case, the symptoms are observed after the case occurred a few days later.  This symptom becomes one of the causes of the misdiagnosis in the field. Many breeders conclude that their chickens are infected with the Newcastle Disease virus. So that they do revaccination against Newcastle Disease in chickens they were actually infected with avian influenza virus, and this always results in more severe conditions on their chicken, significantly increased mortality rate. Some breeders also think their chickens have been infected with two viruses at once, Newcastle disease virus and avian influenza virus. Finally, they also do the wrong handling of their chickens. If they do not use laboratory facilities (rapid test), or assisted by an experienced person to diagnose the case in the field, then a diagnostic error can occur.

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bird flu symptoms in chicken

Stress in chickens can cause cyanosis on the comb, such as diseases, heat stress. On the bird flu virus infection in adult chickens can also cause the same phenomenon. But cyanosis on the comb by avian influenza virus infection sometimes has a different pattern than cyanosis caused by other diseases or stress. Please compare the picture above with the picture below. Pictured above is a chicken infected with bird flu virus, comb swelling, edema and cyanosis pattern in the middle of the comb. This is rarely found in other diseases.

The image below, there is cyanosis on the tip of the comb, comb looks thin. This is a chicken that is suffering from heat stress, dehydration due to mismanagment (run out of drinking water supply) and chronic diseases (colibasilosis, etc). But all the factors that can cause stress in chickens, and chronic diseases can cause such symptoms.

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In the picture below looks chicken eyes opaque. In the case of avian influenza virus infection, H5N1 clade 2.3 this phenomenon is often found post-acute cases. But before the eyes look blurry, blurry, chicken eyes look like glaucoma, enlarged eyes filled with clear liquid.

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bird flu in chickens

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Abdominal Lesions on fat abdominal. avian influenza H5N1Haemorrhagic on abdominal fat is often observed in cases of HPAI H5N1. Some other diseases can cause the same thing, like cholera. In chickens that are kept in the battery cage, these lesions are easy to find.

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avian influenza lesions & symptoms

Spot bleeding on egg follicles is often also used as an indicator to diagnose avian influenza. Newcastle Disease, cholera can also cause similar symptoms, but in H5N1 virus infection, the hemorrhagic spots are clearer and more noticeable.

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avian influenza peracute infection

The images below are cases of avian influenza H5N1, clade 2.3 cases peracute, sudden death, without significant lesions in visceral and reproductive organs. This chicken is still producing an egg in the morning, and then the chicken is to die a few hours later, at noon.

Two pictures below is how the pattern of disease spread in the chicken house. This is interesting information.

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avian influenza, bird flu virus spread of disease

Please note, picture above is taken from a case of high daily mortality that has lasted for 12 days. Look at the pattern/spot (1,2,3,4) in the image !.Chick death starts from spot 1, and up to 12 days later found death of chicken in spot 4.  After 5 weeks later, no deaths occurred. See picture below, battery cage empty (ex-battery cage empty of dead chicken) post case.

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bird flu virus H5N1, transmission, the pattern of mortality

See also: Avian Influenza in Broiler