Swine chlamydia (also known as psittacosis) is caused by swine chlamydia infection, and its incidence is low, but the fatality rate is very high, the spread of the disease The speed is very fast. Once a pig is infected in a pig farm, it will quickly spread in the pig herd, posing a serious threat to the health of the pig herd, and eventually leading to the death of a large number of pigs. Pigs of all ages can be infected with this disease, but it is most harmful to piglets and pregnant sows, which can lead to abortion and stillbirth of pregnant sows. After infection of piglets, it will cause serious adverse effects on their health and development. The disease is very easy to be misdiagnosed, delaying the timing of treatment and causing a large number of deaths in the herd. Therefore, breeders should have an in-depth understanding of the pathogen, causes, clinical manifestations, control measures and purification schemes of the disease during the breeding process to reduce the incidence of the disease in pig breeding.
1 Etiology and epidemiology
1.1 Etiological analysis
The disease is caused by swine chlamydia infection. Chlamydia is a microorganism between viruses and bacteria, and it is negative after Gram staining [1]. Its growth cycle is divided into two developmental stages: protoplasm and reticulum , when the susceptible cells come into contact with the original body, they can be infected, and then they will become reticulum and multiply in the cells by the proliferation of two divisions. It completes its infection process through extracellular secretion or is excreted after being dissolved by the body. Chlamydia has weak resistance to the external environment and can generally survive for 7 days in a natural light environment; 15 days in natural waters and more than 30 days in a dry environment. But chlamydia can survive for a long time in a low temperature environment, about a week in a 4°C environment, and a few weeks in a 0°C environment. It is more sensitive to commonly used disinfectants. For example, it can be inactivated by treatment with 0.5% carbolic acid or 0.1% formaldehyde solution for 24 hours, and it can be killed in a few minutes after treatment with 70% alcohol. ; And the use of hydrogen peroxide with a concentration of 3% can kill it for a while.
1.2 Epidemiological analysis
Studies have found that dozens of mammals and more than 100 species of birds can be infected with chlamydia and carry and spread. Generally, pigs of any age and breed are susceptible to this disease, especially pregnant sows and piglets. Pigs infected with this pathogen can excrete pathogens to the outside world through saliva, feces, urine, milk or other secretions. The amniotic fluid, stillbirths or afterbirths of pregnant sows after abortion will contain pathogens, especially after being cured. The affected pigs can still detoxify for a long time and become an important source of infection. In addition, wild birds, poultry or rodents can also carry the pathogen, posing a threat to the pig herd in the pig farm. At present, there are various degrees of chlamydia infection in large-scale pig farms in my country. The disease usually presents a chronic course of disease, so it is very easy to be ignored by farmers. However, with the continuous passage of chlamydia, its virulence continues to increase. , once the right conditions are met, a large-scale acute outbreak can occur.
2 Clinical symptoms The incubation period of
healthy pigs is about 7 days after infection with this disease, and the clinical manifestations of pigs of different age groups after infection with this disease are also different.
2.1 Piglets
Piglets before and after weaning are susceptible to swine chlamydia. The affected pigs are mainly characterized by fever, body temperature can be as high as 41-41.5 ℃, depression, body tremors, difficulty breathing, frequent coughing, and mucous secretions in the nasal cavity. Auscultation revealed rales in the lungs. Sick pigs have decreased appetite, stunted growth and development. In the early stage of the disease, thin feces will be discharged. In severe cases, dehydration will occur. As the disease progresses, black feces mixed with mucus or blood will be discharged. About 25% of the affected pigs develop inflammation and congestion of the conjunctiva, edema of the eyelid, tearing and the inability to open the eyes. In the late stage of the disease, some affected pigs will have neurological symptoms such as hyperexcitability, screaming, stroking of limbs, and sudden falling to the ground. When a pathogen infection occurs in the joints of piglets, joint swelling, pain and lameness can occur.
2.2 Sows After the
sows are infected with the disease, their body temperature usually rises to about 39-41.5°C. The affected pigs are depressed, lose their appetite, have constipation, have difficulty breathing, and have obvious panting. The affected pigs do not like to walk and refuse to stand. The affected pigs also had cough, purulent nasal discharge, flushing of the conjunctiva and increased sticky secretions. When the pregnant sow has an abortion, its body temperature will drop to about 38°C, but the body temperature will rise again on the second day. Pale red congestive areas can be seen in the groin and other parts, and then the color of the congested areas will gradually deepen, and finally a bleeding spot will form. The ears of the affected pigs turn purple, their appetite is reduced or even abolished, and the anus will be contaminated with feces. There are a few affected pigs. Purulent hemorrhagic dysentery may also occur. Pregnant sows have a longer course of disease and have dark brown faeces mixed with mucus or blood, swelling of the joints, unsteady movement, and lameness. After the sow has aborted, there is purulent fluid flowing out of the vagina, and the fetus is dark gray, the afterbirth is dark red, and a layer of water-like substance is adhered to the surface, and it exudes a foul smell. The incidence of primiparous sows is about 10%, and the cured pigs will not have abortions, etc. However, if the aborted pigs do not discharge the afterbirth in time, it is very easy to secondary bacterial infection, resulting in the occurrence of sows. Uterine inflammation.
2.3 Boars The main symptoms
of boars infected with this disease are depression and elevated body temperature. At the same time, the semen quality of the affected pigs is significantly decreased. Some affected pigs will not develop the disease after infection, but will continue to excrete them. Pathogens that cause infection in otherwise healthy pigs.
3 Diagnosis
Since the clinical symptoms of the disease are similar to those of swine fever and porcine blue-ear disease, it is difficult to make a definite diagnosis only through clinical changes. Laboratory diagnosis such as serological monitoring and pathogen isolation is also required to confirm the disease.
3.1 Microscopic examination of pathogens Collect liver, spleen, lymph nodes and other tissues and organs of dead pigs or aborted fetuses under
sterile conditions for smearing, then stain with Giemsa, and place them under microscope for microscopic examination. If you can see purplish red particles Chlamydia-like protosomes and blue-purple reticulum can be diagnosed as chlamydia.
3.2 Isolation and culture
of The disease materials suspected of chlamydia infection after smear and staining microscopy were aseptically sampled, ground, diluted, homogenized, centrifuged and left for 30 minutes, and then the supernatant was inoculated into 7-day-old chicken embryos. In the yolk sac, the vitelline membrane was taken after 72 hours and continued to be passaged. After 7 to 10 days, a stable and lethal chicken embryo was obtained, and a large number of chlamydia could be isolated
3.3 PCR technology
By designing specific primers for chlamydia, a PCR diagnostic method can be established. This diagnostic method is convenient, fast, highly sensitive, and specific. It is one of the most commonly used methods for laboratory monitoring of pathogens.
3.4 Serological diagnosis
Through complement fixation test (CF), indirect hemagglutination test (IHA), enzyme-linked immunosorbent assay (ELISA) and immunofluorescence (IF) test, etc., monitor whether the serum samples of suspected pigs contain chlamydia-specific It is possible to determine whether the pigs are infected by pathogens by using the antibodies, and this method has been widely used in practical detection [1].
4 Drug treatment
For swine chlamydia, antibiotics such as tetracycline, oxytetracycline, erythromycin and doxycycline hydrochloride are often used clinically for prevention and treatment. Breeders can mix 50% oxytetracycline hydrochloride soluble powder into drinking water at a dose of 300g/t to feed pigs to prevent this disease. Newborn piglets with disease can be treated with intramuscular injection of 1% oxytetracycline at a dose of 1 mg/kg bw for 5 to 7 days; for pregnant sows, tetracycline and other drugs can be injected about 2 to 3 weeks before birth. To prevent neonatal piglets from contracting this disease [2]. For pigs with severe symptoms, 1.5 million IU erythromycin + 100-150 mL of 10% glucose solution + 5 g of VC can be administered intravenously, and 20 mL of compound VB intramuscular injection can be used for 3 consecutive times. [1]. In addition, 15% chlortetracycline premix can also be added to the feed at a dose of 3g/kg to control the outbreak of the epidemic in the field.
5 Preventive measures
5.1 Strengthen feeding and management measures
Strengthening feeding and management measures in the breeding process can effectively improve the immunity of the pig herd and improve its own disease resistance. Breeders should rationally match the rations according to the differences in nutrient requirements of live pigs at different growth stages to ensure that live pigs can take in sufficient and balanced nutrients. In particular, young pigs should do a good job in cleaning and disinfection of the pens and keep warm and cold. It is best for pregnant sows to be raised alone to avoid the spread and infection of diseases. For fattening pigs, ensure that the supply of rations is sufficient. At the same time, attention should also be paid to good ventilation conditions and suitable temperature and humidity in the pen, so as to avoid the stress response of pigs to various stimuli and increase the risk of disease [3].
5.2 Strengthening disinfection and sanitation management
During the breeding process, the staff should promptly remove the feces, leftover material residues and other contaminants in the shed, and conduct thorough disinfection on a regular basis. Disinfection effect, cut off the route of transmission, and strictly control the source of infection.
6 Purification strategy
6.1 Strengthening biosecurity prevention and control
The farm should do a good job of cleaning and disinfection. It is best to disinfect the pens and sports fields once a day. Wild animals, rats, birds, etc. are prohibited from entering and leaving the pig farm to prevent disease. original dissemination. Adhere to the principle of "self-breeding and self-raising" as much as possible. If you need to introduce pig breeds, you should do various inspections for epidemic diseases in advance to ensure that there is no abnormality before introduction, and after the introduction, you still need to be isolated and raised. After the isolation is completed, there is no problem. The other pigs are mixed. The aborted fetus of the sow or the sick pig that died of illness, and the feed contaminated by the sick pig should be treated harmlessly and disinfected well.
6.2 Eliminate infected pigs in a timely manner Pig
farms should carry out regular serum antibody tests for this disease, which can detect and eliminate latently infected pigs in time, prevent wider spread and spread, and reduce the harm caused by this disease to the farm.
7 Conclusion
To sum up, swine chlamydia is a serious harm to the pig breeding industry, and no effective therapeutic drugs have been found, so prevention should be the main focus in breeding. Breeders should take corresponding protective measures according to the epidemic characteristics of the disease, control the spread of pathogens, strengthen feeding management, improve the immunity of pigs, reduce the incidence of the disease, and promote the healthy and rapid development of the pig breeding industry.
.jpeg)
评论
发表评论