Renal transmission branch of chicken

Renal infectious bronchitis is a pathological manifestation of chicken infectious bronchitis caused by coronavirus. In recent years, especially since last winter and this spring, the incidence of renal transmission in Shandong Province, especially in Qingdao has increased significantly, resulting in considerable economic losses in the broiler industry, especially in the broiler industry, which has aroused widespread concern.

Renal transmission is not an independent disease caused by an independent virus, it is a special phenotype of the transmission virus strain in the urinary organs of chickens, or under specific environmental conditions, it is a prominent manifestation in the kidney of some renophilic transmission viruses in the process of systemic infection in chickens.

Studies have shown that the sum of all renal type transmission virus strains in the world does not show that they can form an independent transmission serotype. In fact, it can be said that the transmission branch virus in any serotype may show its nephropathic effect under certain conditions. For example, renal transmission is very common in Australia, with the exception of the famous "T strain", almost all transmission viruses isolated in Australia can cause kidney disease to a greater or lesser extent. The serum neutralization test of renal transmission mycovirus strain C90 Jing 66 isolated from Thailand in 1990 showed that it did not belong to T strain and was not related to British IBV4/91 strain, but was closely related to Masstype H120 strain. The variation of the transmission virus is very complex. So far, mankind has not fully understood and grasped all its secrets. Perhaps we can now say that renal type transmission virus (strain) is a common variation of respiratory transmission virus in biological characteristics and serotype level under certain conditions.

The disease only infects chickens, broilers are particularly susceptible, and other poultry are not infected. Rainy and cold seasons are frequent. Characterized by regional distribution. The susceptible age was between 15 and 50 days old, especially at the age of 3 to 6 weeks, which was almost the same as that of infectious bursal disease.

The typical course of renal transfer can be divided into two stages: the first stage (about 3 weeks old) has mild respiratory symptoms, which is often ignored and disappears after 2-4 days. In the second stage, the peak of death occurred at 7-10 days after the onset of the disease (that is, about 4 weeks old). The chickens suddenly aggravated their systemic symptoms, depressed spirit, anorexia, gray-white thin stool or white paste feces, sometimes watery dysentery, severe water loss, and dry claws (commonly known as "withered feet" or "dry claw disease"). The whole course of the disease lasted 21 days and 25 days, and the mortality rate was 10% and 30%. Generally, the disease slows down after 6 weeks of age, and the mortality rate decreases to less than 1%, but the growth is obviously slow, and the meat exchange rate of feed decreases.

The pathological changes of renal branches were mainly concentrated in the kidneys, which were enlarged and pale in both kidneys. The renal tubules showed betel hammer-like patches due to the accumulation of urate. Both sides of the ureter become obviously dilated, thickened and whitish due to the deposition of uric acid. In chronic cases, the kidney fades and the renal parenchyma is covered with yellow-white urate nodules the size of millet grains, sometimes ranging from soybeans to broad beans (kidney stones). In some cases, one or both ureters are completely blocked by white urate, resulting in ureteral calculi and urinary retention. Sometimes in the pericardium and liver surface also accumulate urate, like a layer of white frost, this is visceral gout. The cloacal cavity is filled with white plaster urate excretion.

The severity of nephropathy depends on six main factors: the nature of the ① strain; the maternal antibody level of ②; the sex of ③ (male mortality female); the nutritional status of ④ (mortality of high-protein and low-protein feed chickens, which is related to the level of uremia); ⑤ strain, the highest incidence of broilers; and the age of ⑥ infection (the lower the age of onset, the higher the mortality). In addition, it is also related to the immune system of the affected chickens. Preliminary statistics showed that the incidence of renal transmission was higher in broilers using highly virulent infectious bursal disease vaccine.

The diagnosis of renal branch is generally not difficult. A preliminary diagnosis can be made from the age of onset, white loose stool, severe dehydration, severe nephroma and urate deposited spotted kidney found during autopsy. The renal transfer branch lacks bleeding from the chest and leg muscles, and there is no lightning course and peak death, which is generally not confused with infectious bursal disease. Although some transmission strains can also cause edema and bleeding of bursa of Fabricius to a certain extent, the authenticity can be identified by Agar diffusion test with tissue suspension of bursa of Fabricius and positive serum of infectious bursal disease.

In addition to the biosafety control, isolation and disinfection of chicken farms, the prevention of renal transmission is mainly based on vaccination. For broilers and breeder chickens, if there is a local epidemic or threat of renal transmission, then, in addition to immunizing the common type of transmission vaccine (for example, H120Finals Ma5, etc.), we should also choose a high-quality renal transmission vaccine for immunization (for example, H120328c86). In some broiler farms in Qingdao, after 1-day-old use of ND-VH+H120+28/86 (eye drops or nasal drops), generally speaking, renal transmission branches are very rare. On the contrary, if only H120 or Ma5 vaccine is given, then there are more renal transmission branches. However, since last winter and this spring, there have been more and more cases of renal transmission in some broiler farms that have been immunized with H120-28x86 vaccine. Through laboratory testing, it is true that the transmission virus causing dwarf embryos can be isolated. After excluding the influence of immune operation and vaccine quality, the reason may be related to the variation of renal transmission branch (including virulence variation and molecular variation), the invasion of new transmission virus and the immune state of chicken. As most of the new cases of renal transmission occur in the use of highly virulent infectious bursal disease (IBD) live vaccine to reduce the damage and pressure on the immune center. This is not only beneficial to the prevention of renal transmission, but also of great significance to other infectious diseases, especially Newcastle disease, avian influenza and colibacillosis.

If renal transmission disease still occurs after vaccination with 28Gram 86 strains of renal branch vaccine, GallivacIBn renal branch vaccine (produced by Meria) can be considered at 7 days old. This is a new type of live virus vaccine of renal transmission, which was isolated from Thailand in 1990 and attenuated for 65 generations by SPF chicken embryo transmission. According to reports, after a 7-day-old immunization, it can 100% protect the renal transmission branches of Thailand, Taiwan and Malaysia, and the protection period can last about 6 weeks, which is very suitable for broilers. If a live Newcastle disease vaccine is arranged at the age of 7 days, it can be separated from the GallivacIBn vaccine (one drop on one side). This will not have a significant effect on the immunity of Newcastle disease.

It is worth noting that vaccines with good protection against renal transmission in one area may not protect renal transmission in another. If we blindly introduce foreign renal transmission vaccine, it may have a protective effect on the local renal transmission, or it may not be protected at all. on the contrary, it will add a new virus to the local area. Everything should be based on practice.

If all kinds of transmission vaccines sold in the market can not well protect the transmission or renal transmission of local chicken flocks, the best way is to isolate the virus strains from infected chickens in this farm, and please make oil emulsion self-inactivated vaccine in a high-level research institute or laboratory. and combined with the typical transmission live vaccine at the same time, this can better solve the problem of serotype and mutation.

When renal transmission is co-infected with mycoplasmosis and colibacillosis, especially with Newcastle disease, avian influenza and other viral diseases, the mortality rate will increase significantly. At this time, it is more important to strengthen veterinary hygiene and feeding management.

In terms of treatment, there is no specific drug at present. Diuresis and detoxification are the main drugs to treat the disease. Rehydration salts can be added to drinking water, or high-quality electrolytes + vitamins. Some traditional Chinese medicine antidotes for kidney swelling can be helpful to uremia.