Fowl Adenovirus Serotype D(FADV - D)

Fowl Adenovirus Serotype D (FADV - D) overview

Avian Adenovirus type D (Fowl Adenovirus Serotype D, hereinafter referred to as FADV - D) is a kind of influence of poultry virus, belong to the Adenovirus family. This virus can cause a variety of diseases, including intestinal disease, liver disease, and respiratory diseases, etc. FADV - D usually leads to infected poultry appear loss of appetite, weight loss, dyspnea, diarrhea, serious when can lead to death.

Diagnosis and control

FADV - D diagnosis often depend on laboratory tests, including molecular biology methods such as PCR (polymerase chain reaction) and virus separation, etc. PCR kits can be used to detect the DNA of fowl adenovirus type D, help vet confirmed. In addition, the fluorescence quantitative PCR kit can be used for quantitative detection of viral load, improve the diagnostic accuracy and sensitivity.

Prevention and control measures including improving breeding environment, strengthen the biological security measures, such as the implementation of vaccination. Because FADV - D can be spread through vertical and horizontal transmission, thus to control the spread of disease is particularly important. Vaccination is the effective measure to prevent FADV - D infection, can reduce the virus spread and outbreak in the crowd.

The latest research progress

Recent studies have shown that FADV - D infection of poultry have immunosuppressive effect, it may be reported in this field in recent 10 years for one of the leading causes of mixed infection with other virus. The study also found that FADV - D infected chicken spleen in inflammatory cytokines (IL6, IL8) transcription at different time points are raised, and the number of CD4 and CD8 T cells after infection significantly reduce some of the time points. These findings contribute to understanding the pathogenic mechanisms of FADV - D, and to provide scientific basis for the development of new control strategies.

Above all, avian adenovirus type D is a kind of important poultry pathogens, its diagnosis and prevention and control to the integrated use of modern veterinary technology and scientific management measures. With the deepening of the research, the future there may be a more effective prevention and control methods have been developed.

The main clinical symptoms of avian adenovirus type D

The main diseases caused by avian adenovirus type D are inclusion body hepatitis and pericardial effusion syndrome. The following are the main clinical signs of these two diseases:

Inclusion body hepatitis

50. The incubation period: usually shorter, about 1 to 2 days.
50. Symptoms: sick chicken may show the flagging, crouching, fluffy feathers, poor crown beard and facial skin was pale, growth and other symptoms.
50. Pathological changes: liver significantly enlarged, blunt edge thick, very brittle, fatty degeneration, liver surface present a pot of hemorrhage, focal under capsule has a large area of congestion and bleeding, and there are different sizes of yellowish-white focal necrosis. Spleen and kidney mild swelling, subcapsular organ and muscle extensive hemorrhage. Liver cells of intranuclear inclusions in the diagnostic significance.

Pericardial effusion syndrome (Ankara disease)

50. Symptoms: sick chicken may show spirit depressed, fluffy feathers, don't want to walk, characteristic symptoms for poultry suddenly fell down, eyes half closed, two feet empty, death within a few minutes.
50. Pathological changes: autopsy visible pericardium bag has pale yellow effusion, liver swelling discoloration, swelling in the kidney. The appearance of the heart is similar to after peeling litchi, so also known as litchi heart disease.

These symptoms may lead to a higher mortality rate, if not controlled, could quickly spread to the whole crowd. For suspected cases, therefore, should take immediate steps to isolate it, and diagnosis and treatment as soon as possible.

Avian adenovirus type D PCR detection method

PCR testing for avian adenovirus type D typically involves the following key steps:

1. Samples: first of all need from suspected avian adenovirus type D birds gathering samples such as blood, tissue, or secretion in the body.
2. Nucleic acid extraction, using specialized nucleic acid extraction kit from samples extracted DNA or RNA. This step is very important to subsequent PCR amplification, because only the pure of nucleic acids can ensure the success of the PCR reaction.
3. PCR amplification: use the avian adenovirus type D specific primers for PCR amplification. These primers based on avian adenovirus type D highly conservative area design, can specifically recognize and combining to the target DNA or RNA sequences.
4. After electrophoresis analysis: the PCR amplification product of electrophoresis analysis, by looking at the size and number of segments of DNA to see samples in the presence of fowl adenovirus type D.
5. Interpretation results: according to the result of electrophoresis, whether poultry infected with avian adenovirus type D. If samples to detect specific DNA fragments, explain avian adenovirus type D exist in the sample.
6. Report issued by: according to the result of diagnosis, issue the diagnosis report, provide the basis for poultry disease control and prevention.

In practice, in order to ensure the accuracy of detection and reliability, usually set the positive control and negative control, and repeated the experiment many times to verify the consistency of the results. In addition, the operator needs to have the corresponding professional knowledge and skills, in order to avoid the experiment error and pollution.

It is important to note that different avian adenovirus type D there may be genetic differences, so need to consider when designing primers to these differences, in order to ensure primers specificity and sensitivity. In addition, as technology advances, new PCR technology according to the facts of fluorescence quantitative PCR (qPCR) and droplet type digital PCR (ddPCR) is also used in the detection of fowl adenovirus type D, these technologies have a higher sensitivity and accuracy, and can provide a more detailed quantitative information.

The research progress of fowl adenovirus type D vaccination

The research progress of fowl adenovirus type D vaccine involves a variety of methods and strategies, including the development and application of genetic engineering vaccine. Here are some key points:

1. Genetic engineering vaccine, researchers are exploring using fowl pox virus as a carrier to express avian adenovirus type D (MDV - D) gene vaccine. This method by means of genetic engineering, will MDV - D key gene inserted into a fowl pox virus, thus produced can induce immune response of vaccines.
2. Carrier vaccine: in addition to fowl pox virus, other carrier, such as new town of (NDV) was considered to build MDV - D vector vaccine. These vaccines in the humoral immune, mucosal immune and poison attack protection show better performance.
3. DNA vaccine, DNA vaccine is a new form of vaccine, it by encoding target antigen protein gene sequences into the host cell, using the host's express antigen protein transcription mechanism, so as to induce an immune response. The vaccine can induce humoral immunity and cellular immunity at the same time, has the high safety and convenience.
4. Table a DNA vaccine, researchers are trying to build contains multiple immune epitope DNA vaccine, in order to improve the vaccine immune efficacy and protection scope. These vaccines can express multiple antigens on the same carrier, so as to realize cross protection for a variety of strains.
5. Attenuated salmonella typhimurium mediated DNA vaccines: a study using attenuated salmonella typhimurium as the carrier, oral vaccination of DNA vaccine containing the MDV - D gene, this method can stimulate the body to produce mucosal immune response, and provide the H5 subtype of avian influenza virus immune protection.

To sum up, avian adenovirus type D vaccine research is developing towards diversification and efficiency, and poultry disease prevention and control for the future is expected to provide more effective tool.