Epidemic Characteristics and Prevention and Control Strategies for Diseases in Chicken Farms
1 Current @#@230@#@ Epidemic Characteristics of Diseases in Farms
The speed of disease transmission has accelerated. The most notable features of large-scale chicken farming are the large production scale and the large number of chickens. The increase in the number of chickens leads to an accelerated speed of disease transmission and spread within the flock.
Disease resistance declines. In large-scale chicken farms, in order for producers to fully realize the production potential of chickens, the flock is kept in a highly stressed production state, which inevitably increases stress factors for the chickens, thereby causing endocrine abnormalities in sensitive chickens and a decline in disease resistance. Some diseases that are not prone to occur under free-range conditions, such as stress syndrome, have become commonly occurring diseases.
The types and quantities of breeding poultry introduced from abroad have increased significantly, especially through multi-channel introduction, and without understanding the disease occurrence situation in the countries of origin, as well as lacking effective monitoring methods and supporting measures, diseases are introduced along with the breeding poultry. Diseases that have newly appeared in recent years mainly include chicken infectious anemia, chicken proventriculitis-type infectious bronchitis, avian encephalomyelitis, chicken colibacillosis, egg drop syndrome, rhinotracheitis, swollen head syndrome, chlamydiosis, and others.
Diseases have become atypical. Due to insufficient immune levels, especially inconsistent herd immunity levels, pre-existing old diseases often appear with atypical symptoms and pathological changes - that is, atypical presentation, and sometimes even appear with a new appearance, of which the most representative is bronchitis.
The clinical symptoms of major infectious diseases have become diversified. The clinical symptoms of the same disease present multiple types coexisting simultaneously, and the correlation among the clinical symptoms is very small, with a very low cross-protection rate after natural recovery. For example, infectious bronchitis has the traditional respiratory type, egg production decline type, enterotropic type, proventriculotropic type, and a type not yet determined that can cause meat damage, among others. Marek's disease has neurological damage type, skin type, visceral type, ocular type, and others, including both mild subclinical infection leading to immunosuppression and diseases caused by super-virulent strains that cause huge losses.
The same clinical symptom may have multiple causes. Due to changes in pathogen serotypes and the emergence of new strains, the scope of invasion continues to expand, and clinical symptoms also become diversified, thus making the symptoms of the same cause more complex. Gastric swelling and degeneration may be Marek's disease or proventriculitis-type infectious bronchitis; encephalitis symptoms may be encephalomyelitis, encephalitis-type pullorum disease, encephalitis-type colibacillosis, and others.
New changes have appeared in pathogen virulence or antigens. In modern chicken production, the virulence of the pathogens of some diseases continues to increase, and virulent or super-virulent strains have appeared. Although the flock has been vaccinated, it still cannot obtain protection or the protective effect is not strong, leading to immunization failure.
The incidence of some bacterial diseases has increased, the cure rate has decreased, and the harmfulness has increased. With the improvement of the scale level of the chicken industry, the increase in the circulation volume of livestock and poultry commodities, the intensification of environmental pollution, and the increase in various stress factors, the susceptibility of chickens to pathogens has increased, causing a significant increase in the occurrence of bacterial diseases. At the same time, due to long-term irrational drug use, abuse of antibiotics and feed containing antibacterial drugs, the drug resistance of bacterial infectious pathogens in chickens has become increasingly serious, making the control of chicken bacterial diseases such as colibacillosis, Mycoplasma gallisepticum, and infectious coryza more difficult.
Mixed infections have increased, the condition is complex, and the harm is greater. In the epidemic process of livestock and poultry diseases, according to diagnosis, more than 50% of diseases are mixed infections or secondary infections. In actual production, the types of mixed infections include viral and bacterial mixed infections. Bacterial mixed infections, such as mixed infection of chicken colibacillosis and salmonellosis, mixed infection of bacterial diseases and parasitic diseases, and mixed infection of chicken colibacillosis and coccidiosis.
2 Prevention and Control Strategies
2.1 Strengthen the monitoring and quarantine of major diseases
Achieve early warning and take corresponding and effective control measures as early as possible, regularly quarantine breeding chicken farms, and eliminate positive chickens. During incubation, conduct sampling tests on fertilized eggs, dead embryos, and weak chicks and dead chicks at hatching to determine whether vertical infectious diseases exist; conduct proportional sampling tests in commercial farms to understand the antibody levels and disease conditions of the flock; regularly test the bacterial content and mycotoxin levels in the air inside the houses; after vaccination, conduct antibody level testing according to plan, and establish an epidemic registration and reporting system; at the same time, test the feed entering the farm, and do not purchase feed products produced in epidemic areas; strengthen air quality purification, and regularly test the air quality of chicken houses.
2.2 Promote advanced feeding and management techniques
Large-scale chicken farms should establish a stable improved breed breeding system, so that the population supply of chicken farms at all levels (nucleus farms, great-grandparent farms, parent farms, commercial farms) is relatively fixed, in order to reduce the vertical transmission and horizontal transmission of diseases within the breeding system; "all-in, all-out" is an important technical measure for large-scale chicken farms. It can not only ensure the planning of production, but also help the health care of the flock and the control, eradication, and purification of diseases; under high-density intensive feeding conditions, in order to ensure the normal production of the flock, it is necessary to effectively control the environment inside the chicken house, such as temperature, humidity, light, dust, harmful gas concentrations, and the number of pathogenic microorganisms; in order to pursue high benefits, large-scale chicken farms often use standardized high-efficiency breeding chickens with fast growth speed and high egg production rate. For this reason, it is necessary to supply sufficient high-quality feed and select appropriate feed formulas, and carry out standardized feeding of the flock according to nutritional standards.
2.3 Adopt comprehensive prevention and control measures
Formulate disease prevention and control norms, and strictly implement hygiene and disinfection systems. Pathogenic microorganisms are everywhere in nature. In order to prevent the occurrence and spread of diseases, pathogenic microorganisms in the living environment must be eliminated to eliminate sources of infection and cut off disease transmission routes; carry out scientific vaccination in a planned and conscious manner to enhance the resistance of chickens; do a good job in drug prevention and treatment. Drug prevention and treatment of diseases should be based on correct diagnosis of the disease, and according to the epidemiological patterns of the disease and drug sensitivity tests, select highly sensitive drugs and appropriate doses, and adopt correct administration methods for treatment.
2.4 Emergency measures when an epidemic occurs
The specific emergency measures include the following aspects: 1) During daily inspection or quarantine, once a suspicious condition appears, isolation measures should be taken immediately, and personnel should be organized to promptly diagnose and formulate relevant treatment and emergency vaccination plans; 2) When a fulminating infectious disease occurs, the site should be immediately locked down; report to the higher-level competent department and take corresponding measures; 3) Dead chickens should be incinerated, deeply buried, or centrally processed, and it is strictly prohibited to sell and consume them; 4) Chicken houses, facilities, tools, etc. where the disease occurs must be thoroughly cleaned, strictly disinfected, and left vacant for a certain period before use.