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Salmonella

Salmonellosis of birds (Latin, English - Salmonellosis; paratyphoid, infectious diarrhea of ​​birds) is a disease characterized by an acute course of septicemia in young animals and latent infection in an adult bird.

Historical background, distribution, hazard and damage. Salmonella is widespread. Salmonella was first isolated from pig organs by American veterinarians Salmon and Smith in 1885. Later, diseases similar in etiology were called paratyphoid fever.

The economic damage in chicken salmonellosis consists mainly of losses from the departure of young chickens, lagging in growth and development of sick young chickens, decrease in egg and meat productivity of adult livestock, culling of sick and salmonella carriers, restrictions on sales of products from farms unsuccessful in salmonella chickens, costs to improve the economy.

An ill bird remains a carrier and a source of the pathogen for life, accumulating it, including in poultry products - eggs. Poultry and eggs are dangerous sources of salmonellosis for people, which occurs in the form of severe intestinal disorders and intoxication. In addition, being weakened, such chickens are more susceptible to other pathogenic agents.

The causative agent of the disease. The causative agents of salmonellosis in birds can be various Salmonella serovars that are not adapted to the bird (with the exception of S. pullorum-gallinarum, which causes an independent disease, see Pullorosis), however, these are mainly S. enteritidis and S. typhi-murium, which cause salmonella in waterfowl.

According to cultural and morphological properties, all salmonella are similar (see Salmonella). Salmonella is differentiated by their growth on Endo, Ploskirev, Levin and others.

Salmonella are quite stable in the external environment and to the action of physical and chemical factors. In litter and feed, they remain viable for up to 100 days, in soil for more than 400 days, in downy raw materials for more than 1150 days.

Epizootology. The most susceptible to salmonellosis are chickens, turkey poults, especially meat breeds, and in the first days of life. The main source of the causative agent of the infection is a sick bird that releases a large amount of the pathogen with litter. In salmonellosis, the transvarial method of infection can be significant - through the egg. The number of infected eggs laid by laying hens varies widely and increases during the period of enhanced egg laying. The causative agent of the infection is found in the yolk and causes the death of the embryos at all stages of embryonic development. An ill bird, isolating the pathogen into the external environment, infects feed, water, equipment.

The causative agent of the disease can also spread wild birds (pigeons, sparrows), rodents (mice, rats), ectoparasites (ticks, bird bugs). The causative agent of infection can be found in fish and meat and bone meal; on average, every fifth batch of feed is infected with salmonella. With salmonellosis, both the vertical and horizontal pathways of transmission of the infectious principle are noted. Alimentary and aerogenic infection are of primary importance.

Often, breeding farms, selling products to another farm, introduce the pathogen with an egg. Defective and untimely feeding of birds, crowding,

overheating, hypothermia, i.e., factors causing a decrease in natural resistance.

The incidence of chick salmonellosis varies from tenths to several tens of percent. Mortality in chicken salmonellosis in Russia is 13 ... 25%.

Pathogenesis. In the development of the disease, the production of endo- and exotoxins is of great importance.

With alimentary infection, the pathogen enters the gastrointestinal tract, localized on the intestinal mucosa (primary affect) - the blind processes, causing inflammatory and degenerative changes. As a result of a violation of the barrier functions of the mucous membrane, the microbe penetrates the lymphatic and blood vessels, spreads through the blood stream to all internal organs, causing septicemia and necrosis (secondary localization of the pathogen). Then, salmonella again enters the bloodstream, disrupting the functioning of the internal organs, which leads to death.

In the case of aerogenic transmission, the pathogen enters the lungs, forming foci of necrosis, from where it penetrates the bloodstream and spreads throughout the body.

The course and clinical manifestation. The incubation period continues with alimentary infection of 5 ... 7 days, and with aerosol infection - only 24 ... 36 hours. There are an acute, acute, subacute and chronic course of the disease.

An ultra-acute course of infection is observed in chickens that have hatched already sick. They die a few hours after withdrawal. An acute course is more often noted in young animals aged 1 ... 10 days. In diseased chickens, appetite worsens or disappears. They become lethargic, eyes are half-closed or closed, wings are lowered. Chicks move slowly, often peep. The main symptom is diarrhea. Often the disease proceeds with neuro-paralytic phenomena, this is especially characteristic of hatched ducklings. With subacute and chronic course, clinical signs are less pronounced.

A peculiar salmonella ez manifests itself in pigeons: an acute disease often prevails in pigeons up to 6 weeks of age, most of them die after a few days. Signs of the disease: loss of appetite, inflammation of the conjunctiva, impaired bowel function. In the future, pigeons begin to lose strength, they are indifferent, drowsy, the feather is disheveled, and thirst arises. Body temperature in all cases of acute course is increased. In intestinal form, the course is subacute and chronic. Symptoms of intestinal inflammation: persistent diarrhea, liquid droppings, contains blood, tail feathers are very dirty. The joint form occurs in young pigeons and pigeons after having been ill with a septic form. Initially, inflammation of the joints and tendons proceeds without visible changes. Later they increase, the volume of articular fluid increases. The affected bird is not able to fly, run, so the disease is sometimes called paralysis.

With these forms of damage, twitching of the limbs and trembling are sometimes noted. The muscles of the wings and legs are first compacted, then its atrophy sets in. Under the skin of the joints, nodules the size of a pea are formed - granulomas. If two limbs are affected, then the pigeon moves with the help of wings.

The neural form in most cases occurs subacute or chronically, occurs much less frequently than others.
Nervous phenomena, loss of mobility are characteristic. If you do not separate or destroy such a bird, symptoms may persist for several days or weeks. The bird lies on its side with a curved neck; neck curvature is a fairly typical symptom; if the auditory labyrinth is affected, then the curvature of the neck occurs on this side.

Pathological signs. In dead embryos, the contents of the yolk sac are grassy-green in color, and foci of necrosis in the liver. The gall bladder is usually enlarged and filled with viscous bile; Ampoule-rectal expansion of the rectum with uric acid salts or gases, increased deposition of uric acid salts on allantois are observed.

In chickens who died from salmonellosis, in the first days of life, a large unused yolk the size of a nut, catarrhal-hemorrhagic inflammation of the gastrointestinal tract is observed. Blind processes of the intestine are filled with fibrinous mass. With the cellular content of young animals, especially broilers, the joints of the legs are often affected. In adult birds, the vitelline follicles are irregular in shape, degenerated, contain a necrotic mass of green.

The mucous membrane of the gallbladder is swollen, hyperemic. In salmonellosis caused by S. enteritidis, the gallbladder is filled with dark olive bile mixed with fibrin and mucus.

In the subacute and chronic course of the disease, mainly the large intestine is affected, especially the processes of the cecum, where necrosis of the mucous membrane with overlays of fibrin on its surface is revealed. In parenchymal organs, changes are similar to those described in acute course, but are more pronounced.

A serous effusion with an admixture of fibrin flakes is found in the chest cavity. In the lungs, foci of compaction are gray-red in color. The heart is slightly enlarged due to the expansion of the right ventricle. The myocardium is flabby, the coronary vessels are blood-filled.

Diagnostics and differential diagnostics. The scheme for diagnosing the disease is similar to that for pullorosis. Bacteriological crops are done on conventional and differential diagnostic media (Endo agar, Ploskirev, Levin agar) from the yolk, liver, gall bladder, brain in young birds and altered follicles from an adult bird.

For diagnostic purposes, a blood-drop reaction of indirect hemagglutination (CCRNGA) has been proposed.

Salmonellosis must be differentiated from infectious hepatitis, ducklings sinusitis, ornithosis.

Immunity, specific prevention. Ducklings, goslings who have had an infection caused by S. typhimurium acquire immunity, but remain carriers of the pathogen against the background of immunity. The body of these birds in the absence of reinfection is completely released from salmonella only 60 ... 70 days after the disease. In chickens and turkey poultry immunity is poorly expressed.

A live avirulent salmonellosis vaccine has been developed and produced to immunize ducks and geese. Ducklings and goslings are vaccinated orally from 2 ... 3 days of age, after 2 days the vaccination is repeated. The vaccine creates intense immunity for a period of 3 ... 3.5 months. This allows you to prevent acute outbreaks of the disease, reduce the duration of the tank

teriocarrier and increases the safety of birds. It is possible to vaccinate twice and an adult bird before the start of the breeding period.

Prevention To prevent the occurrence of salmonellosis in poultry farms, the following is necessary: ​​1) sanitation of feed with carbosalom and other sanitizing preparations; 2) providing exit barriers and sanitary inspection rooms to prevent the entry of salmonellosis into farms; for the disinfection of objects, it is necessary to use universal preparations glutex, natusan, virkon S and others; 3) special attention should be paid to the hygiene of nests and hatching eggs obtained from chickens, the shell of which is treated with drugs (virkon S, VV-1, desmol, metacid and others); 4) precisely observe the sampling time of hatched young animals, incubate waste or incinerate; 5) to disinfect incubation cabinets, containers and vehicles after each use; 6) youngsters should be given probiotics at the first feeding.

Treatment. For the treatment of a patient brought out young animals, colmic-E, enfloxatril, eryprim concentrate, avidox, colimycin, albac and other antibacterial drugs are used. Most drugs are active against salmonella at the onset of the disease and during the incubation period of the disease, so obviously sick birds are rejected, and the rest are given drugs with food or water according to the instructions.

Control measures. Due to the fact that in adult birds, the disease proceeds chronically in an asymptomatic form, and the ill young bird has remained a bacteriocarrier for a long time, mass eradication is very important in eradicating the disease. A study of the birds of the parent flocks according to CCRNGA for the well-being of salmonellosis should be carried out without exception and without fail, as well as for pullorosis. This allows you to accurately determine the presence or absence of infection, the degree of trouble of the herd, remove bacteria and timely treatment, specific prophylaxis.

A bird responding to salmonellosis according to SCRNHA is sent to a sanitary slaughterhouse and disinfected in the presence of a bird, and bleach is added to the litter. Inventory, nests, feeders are subjected to mechanical cleaning, washing, disinfection using a wet method.

If from 7 to 10% or more of an adult poultry reacts positively in CCRNHA, the improvement of such a herd through systematic research, treatment or vaccination is not economically feasible. Therefore, such a population of birds is subject to slaughter, and poultry houses - sanitation. In the case of the clinical manifestation of the disease among young or adult livestock, sick birds are discarded, killed, and carcasses of birds discarded.

Restrictions on salmonellosis of birds are removed from the farm when receiving negative results twice in the CCRNGA, as well as if the pathogen of salmonellosis was not isolated during a systematic bacteriological study of pathological material.

Control questions and tasks. 1. What is the epidemiological significance of avian salmonellosis? 2. What are the sources and factors of transmission of the causative agent of infection. 3. What are the principles of diagnosis and differential diagnosis in salmonellosis of birds. 4. What modern chemotherapeutic drugs are used against salmonellosis? 5. List preventive and control measures that prevent foodborne toxic co-infection.
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Salmonella

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