1 analysis of clinical symptoms and prevention methods of common infectious diseases in pigs
1 swine paratyphoid fever
The disease mainly affects piglets aged 1 ~ 4 months, which can occur all year round, but it occurs frequently in rainy and humid seasons. Sick pigs and infected pigs are the main sources of infection, which can be excreted through feces, urine, milk, aborted fetus, placenta and amniotic fluid, mainly through the digestive tract. Infection may also occur in the uterus. It is quite common for healthy pigs to carry bacteria. When the resistance decreases due to external adverse factors, it often leads to endogenous infection. The main features are diarrhea and dysentery. If you can't get timely and accurate treatment, you will soon die of dehydration, with a high mortality rate and great economic losses.
1. 1 swine paratyphoid symptoms
Acute type: Piglets that mostly occur before and after weaning often die suddenly. The course of the disease is a little longer, the body temperature is as high as 4 1℃ ~ 42℃, diarrhea, dysentery, dyspnea, purple spots on the ear roots, chest and abdomen skin, and most of them end in death.
Subacute and chronic types: manifested as elevated body temperature, conjunctival inflammation and purulent secretion. Diarrhea after initial constipation, discharging gray-white or yellow-green malodorous feces. The sick pig is thin, and the skin has scab eczema. The course of the disease can last for several weeks, and eventually the pig dies or becomes stiff.
1.2 control measures
Prevention: Strengthen vaccination or feed paratyphoid vaccine. Keeping a good pig source is excellent for self-reproduction and self-maintenance. Improve the feeding tube and sanitary conditions, eliminate the cause, and enhance the resistance of piglets. Wash utensils and food trough frequently, keep the enclosure clean and dry, and do not leave urine and urine, so as to reduce the chance of infection.
When nursing and cultivating piglets, prevent them from licking dirty things, feed them with high-quality digestible feed, and don't change the feed suddenly.
Treatment: intramuscular injection of enrofloxacin, ciprofloxacin hydrochloride and oxytetracycline tablets; Intramuscular injection of chloramphenicol, gentamicin and oxytetracycline tablets; Intramuscular injection of chloramphenicol, sulfadiazine sodium and oxytetracycline tablets; Inoculate enrofloxacin and chloramphenicol, and take oxytetracycline tablets; Ciprofloxacin hydrochloride, chloramphenicol, oxytetracycline tablets.
2 pig lung disease
Porcine pneumonia is an acute septic infectious disease caused by Pasteurella multocida infection, which can be infected by pigs of all ages. Its characteristic is that acute cases die of septicemia. This disease is pathogenic to many kinds of animals and people. Pigs are the most susceptible, and the seasonality is not obvious. It is characterized by alternating hot and cold, severe climate change, high temperature, high humidity and many rainy seasons. Malnutrition, long-distance transportation and poor feeding conditions promote the occurrence of the disease, which is generally sporadic or endemic.
2. 1 swine pneumonia symptoms
Acute cases have high fever of 465,438+0℃ ~ 42℃, dyspnea, dog sitting posture, cough and asthma, foam or clear fluid in mouth and nose, acute swelling and swelling of throat, hard palpation and heat pain. Erythema appeared on the skin on the ventral side and inside the limbs, the finger pressure subsided, and finally it was difficult to breathe and suffocate. Chronic cases are mainly manifested as chronic pneumonia, chronic gastroenteritis, purulent nasal discharge, persistent cough, dyspnea, loss of appetite, diarrhea, emaciation and other symptoms.
2.2 Prevention and control measures
Prevention: regular injection of pig lung vaccine; Close the pig source; Pigpen should be disinfected regularly to keep dry, sanitary and ventilated; Found cases, timely isolation treatment.
Treatment: intravenous sulfadiazine sodium. Intramuscular injection of long-acting oxytetracycline, enrofloxacin or kanamycin, if combined with other diseases, should be treated symptomatically.
3. Porcine contagious pleuropneumonia
Actinobacillus pleuropneumoniae is the pathogen, which easily infects pigs of all ages, mostly 6 weeks to 6 months old. Long-distance transportation, improper feeding tube, sudden climate change and other factors can cause this disease. Sick pigs and infected pigs are the main sources of infection, mainly spread through respiratory airflow.
3. 1 Symptoms of porcine contagious pleuropneumonia
The incubation period of infected pigs is 1 ~ 7 days. According to the course of disease, it is divided into the most acute type, acute type, subacute type and chronic type. The most acute pig died suddenly without warning. The dead pig's abdomen, ears and limbs are cyanotic, and its nose and mouth are covered with blood-red foam. The mortality rate is as high as 80% ~ 100%. Acute pigs eat little or refuse to eat, and their body temperature is about 465438 0℃. They often stand or sit in the posture of dogs, with listlessness, blue ears, nose and limbs, panting, intermittent cough, dyspnea and extremely painful expression. They often die of suffocation within 24 hours, and some of them turn into subacute or chronic. Pigs with subacute or chronic diseases have normal or slightly higher body temperature, cough and asthma, loss of appetite, emaciation, prolonged or further deterioration of the course of disease.
3.2 Prevention and control methods
Prevention: strengthen epidemic prevention and regularly inject multivalent inactivated pleuropneumonia vaccine; Strictly control the source of pigs; Strengthen feeding management; Strict disinfection system, keep the pens clean, dry and ventilated; All-in and all-out feeding methods are implemented, and sick pigs are isolated and treated in time.
Treatment: early treatment of this disease is effective, and the dose should be large. The first choice is intravenous injection of sulfadiazine sodium, intramuscular injection of long-acting oxytetracycline, enrofloxacin or (kanamycin, amikacin).
Vitamin c and rice will be better when used together. If you are complicated with other diseases, you need symptomatic treatment.
Foot and mouth disease in pigs
Foot-and-mouth disease is an acute and severe infectious disease, which is easily infected by cloven-hoofed animals such as pigs, cattle and sheep. The disease is highly contagious and has no obvious seasonality, and can occur all year round. The main manifestations are salivation, limping, blisters on the mouth, nose plate and hoof.
4. 1 symptoms of foot-and-mouth disease in pigs
The sick pig has elevated body temperature, obvious systemic symptoms, salivation, limping and easy to lie down. Blisters can occur on the nose plate, mouth, gums, tongue, breast (mainly lactating sows), hoof crown, hoof fork and hoof heel. After the blister bursts, purulent blood will form rotten spots. In severe cases, the hoof shell will fall off, and sick pigs may die from fasting, enteritis and diarrhea.
4.2 Prevention and control methods
If pigs are found to have foot-and-mouth disease, they must report to the animal quarantine department, and cannot hide, sell or slaughter them privately. Dead pigs should be incinerated, buried and other harmless treatments; Strictly clean and disinfect fences, utensils and sinks. Prevent foot-and-mouth disease from spreading through air, soil and diseased meat. And infect other livestock and even people. This disease is extremely harmful and cannot be cured. Only prevention. Therefore, prevention is very important, and farmers should attach great importance to it and inject foot-and-mouth disease vaccine regularly to avoid taking chances and causing great economic losses.
Five cases of erysipelas
The disease is an infectious disease of pigs caused by erysipelas. It mostly occurs in summer, autumn and rainy season, and pigs over 2 months old are most susceptible to infection. The incubation period of sick pigs ranges from 3 to 5 days to half a month. The main manifestations are erythema or rash of various shapes on the skin behind the ear, neck, chest and abdomen, dyspnea and high mortality, which is very harmful to the pig industry.
5. 1 symptoms of erysipelas
The disease is divided into septicemia type, rash type and chronic type. Pigs will have symptoms such as elevated body temperature, listlessness, loss of appetite or abandonment, thirst and dry stool. In the ear root, chest, back, abdomen and thighs, there are purplish red rashes with different shapes and sizes, obvious boundaries and flat swelling, which indicates that they subside after pressing.
5.2 Preventive and control measures
Prevention: Regular vaccination against erysipelas. Strengthen the disinfection system and improve the sanitation of fences. Strictly control the source of pigs. Newly purchased pigs should be kept in isolation for a week, and then fed in circles after being confirmed to be normal.
Treatment: intravenous injection of sulfadiazine sodium, intramuscular injection of compound aminopyrine or analgin 10~20 ml diluted penicillin, twice a day; Chinese medicine can be rhubarb, gypsum, Scrophularia, Anemarrhena rhizome, forsythia suspensa, earthworm, licorice 15g, and decocted in water for 2 doses.
Download 2 of Undergraduate Thesis of Animal Husbandry and Veterinary Medicine Talking about the Research Progress of New Treatment Strategies for Cow Mastitis
Mastitis is the most common productive disease of dairy cows, which has caused huge economic losses to dairy industry [1]. There are two types of mastitis in dairy cows: clinical mastitis and recessive mastitis. The main characteristics of clinical mastitis are breast swelling, fever and pain, and breast tissue damage [2], while recessive mastitis has no visible clinical symptoms, but it exists in most dairy farms and is harmful. Mastitis in dairy cows causes the dysfunction of synthesis and secretion of mammary epithelial cells in different degrees, and the synthesis of milk main components such as milk fat, milk protein and lactose is obviously reduced [3], which leads to a significant decline in milk quality. The study confirmed that the loss caused by various factors was comprehensively evaluated, and the loss caused by the decline of milk yield and quality accounted for 49% of the total loss [1].
Antibiotics are commonly used to treat mastitis in dairy cows in China, but the therapeutic effect is not ideal because of the variety of pathogenic bacteria of mastitis and the complicated pathogenic mechanism of breast infection. Long-term and high-dose use of antibiotics can easily lead to the increase of drug-resistant strains and antibiotic residues in milk, which seriously threatens dairy products and life safety. Therefore, it is urgent to develop a treatment method that can quickly repair breast tissue, restore milk production and improve milk quality.
Studies have shown that nisin, Aegis lysozyme, lysostaphin, CpG-DNA and platelet concentrate can be used for clinical treatment of mastitis in dairy cows. In addition, new therapeutic strategies, such as hormone, regulation of breast cell signaling pathway and neutrophil number, also provide a good prospect for rapid and efficient prevention and treatment of mastitis.
1 A new preparation for treating mastitis
1. 1 nisin
Nisin, also known as Lactococcus peptide or Nisin, is a polypeptide antibacterial substance extracted from Lactococcus lactis fermentation broth, which has been proved to be a safe natural biological food preservative and antibacterial agent [4]. Nisin was first used as a disinfectant for bovine breast nipples, with good bactericidal effect and no potential tissue damage. The main mechanism of nisin as a drug to treat mastitis is to destroy the integrity of cell membrane, cause cell lysis and a large number of intracellular proteins to leak out, leading to the death of pathogenic bacteria [5].
Other studies have also confirmed that nisin also plays a good bactericidal role in treating the mouse model of streptococcus pneumoniae infection. The drug sensitivity test results of Staphylococcus and Streptococcus agalactiae isolated from clinical cow mastitis showed that nisin could effectively inhibit the growth and reproduction of these two bacteria [4]. Cao Liting et al [6] used Nisin breast perfusion to treat clinical mastitis. The milk fat content, skimmed milk solid content, milk protein content and lactation performance of dairy cows were measured before and after treatment. After treatment, the above indexes of milk yield of dairy cows have been obviously improved, suggesting that the use of nisin can promote the ability of breast epithelial cells to synthesize milk components and repair breast tissue. Szweda P et al [7] isolated 37 drug-resistant strains from cow mastitis, and the drug sensitivity results showed that 2 1 strain of Staphylococcus aureus was sensitive to nisin, which further proved that nisin had a good bactericidal effect.
1.2 aegis lysozyme
Aegis lysozyme is an effective antibacterial agent, which can cut off the interaction between N- acetylglucosamine and N- acetylmuramic acid in peptidoglycan. -l, 4 glycosidic bond, destroying peptidoglycan scaffold, causing cell expansion and bacterial lysis under the action of internal osmotic pressure [8]. By comparing the therapeutic effects of lysozyme and cefazolin sodium on clinical mastitis, it was found that the content of malondialdehyde (MDA) in whey in lysozyme group decreased significantly after 24 hours of administration, which revealed that lysozyme could inhibit and eliminate oxygen free radicals produced during inflammation. Further research confirmed that egg white lysozyme, duck egg white lysozyme, 10% lysozyme preparation and bacterial lysozyme all had inhibitory effects on staphylococcus causing mastitis in dairy cows [10], among which bacterial lysozyme had the best therapeutic effect and was the most promising one for treating bacterial mastitis.
Shen Cheng et al. [1 1] Breast perfusion of recombinant plasmid pcDNAKLYZ of human lysozyme in the treatment of subclinical mastitis in dairy cows. Comparing the negative conversion rate of bacteria in milk before and after perfusion, the negative conversion rate before perfusion was 0, and the negative conversion rate after perfusion was 5 1.92%, which indicated that the recombinant plasmid had significant antibacterial effect and had a good therapeutic effect on subclinical mastitis of dairy cows.
1.3 lysostaphin
Staphylysin is an endopeptidase containing Zn2+ isolated from Streptococcus mimicus, which can effectively remove the biofilm of Staphylococcus aureus, thus achieving bactericidal effect [12]. Aguinaga et al. [13] treated methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA) with lysostaphin and different antibiotics alone and in combination, which showed that the combined action of lysostaphin and antibiotics had stronger bactericidal effect than using antibiotics alone, and the antibiotic concentration of MSSA and MRSA strains decreased by 2 times to/kloc-respectively. In another study, a mouse pneumonia model was established by MRSA, and different doses of lysostaphin, vancomycin and PBS were used for post-infection treatment. The results showed that the lysostaphin group had the characteristics of low mortality, less lung tissue damage and less bacteria in the infected site, and the dose was dependent [14].
The research of Szweda P et al [7] also pointed out that the minimum inhibitory concentration (MIC) of drug-resistant bacteria to lysostaphin was 0.008? g/mL~0.5？ G/mL, far less than the maximum MIC 32? G/mL, and all drug-resistant bacteria are sensitive to lysostaphin. Jiang Sijia et al [15] treated the 104 milk zone of 85 cows with mastitis with low, medium and high recombinant staphylococcal enzyme powder. The experimental results show that low, medium and high doses of recombinant staphylococcal enzyme can effectively remove gram-positive bacteria such as Streptococcus, Staphylococcus and Cryptococcus pyogenes in infected milk area, greatly reduce the number of white blood cells in milk and increase the daily milk production. The effective rate and cure rate of different doses of recombinant lysostaphin in the treatment of subclinical mastitis and clinical mastitis are better than penicillin, and the curative effect is positively correlated with the dose.
1.4 CpG-DNA
CpG-DNA is a DNA sequence with immune activation function with unmethylated CpG motif as the core. Including CpG-ODN[ 16] synthesized from CpG motifs and genomic DNA of lower organisms in nature. In the goat mastitis model established by Escherichia coli, the number of Escherichia coli in the experimental group was significantly lower than that in the control group. CpG-ODN has protective effect on goat mastitis induced by Escherichia coli [17]. In the mastitis induced by Staphylococcus aureus and Escherichia coli in rats, there were -6 (interleukin -6, IL-6) and tumor necrosis factor-ι (tumor necrosis factor -sis factor) in the breast tissue of the experimental group using CpG-DNA. The mrna expression levels of TNF-Χ) and CpG-DNA specific receptor TLR-9 (Toll-like receptor -9) were significantly higher than those of the control group, and at the same time, the damage of inflammatory reaction and inflammatory mediators to tissues was reduced, suggesting that CpG-DNA has breast protection effect, and its mechanism may be that CpG-DNA binds to pattern recognition receptors on natural immune cells in the host body, triggering corresponding immune response [
1.5 platelet concentrate
The most common function of platelets is to gather at the site of vascular injury to form a coagulation surface composed of prothrombin and fibrinogen, thus achieving the function of hemostasis [19]. Pinto J M et al. [20] treated human chronic skin ulcer with platelet concentrate and observed granulation tissue hyperplasia, which showed that the treatment was effective. The possible reason is that platelets, as carriers of growth factors, stimulate collagen production, activate fibroblasts, induce extracellular matrix remodeling and repair tissue damage.
Lange-Con-siglio A et al [2 1] perfused infected breast with platelet concentrate, and evaluated the therapeutic effect by the number of somatic cells and bacteria in infected breast milk. The results show that the use of concentrated platelets can significantly reduce the number of somatic cells and bacteria in milk, which has a good effect on promoting inflammation dissipation, reducing breast parenchymal damage and reducing the recurrence rate of mastitis. Further research confirmed that platelet concentrate not only has the function of repairing breast tissue, but also has the function of inhibiting the pathogenic bacteria of mastitis in dairy cows.
Bi-elecki T M et al. [22] observed that human platelet-rich plasma agar plate could significantly inhibit the growth of Staphylococcus aureus and Escherichia coli by Kirby-Baue disk diffusion method.
Another study by Marian E et al. [23] not only verified the above research results, but also showed that platelet concentrate also had inhibitory effect on Pseudomonas aeruginosa. Epidemiological survey of mastitis showed that the incidence of Staphylococcus aureus mastitis was 65438 06.3%, and that of Escherichia coli mastitis was 25.2%[24]. Therefore, it is expected to use platelet concentrated solution to treat mastitis caused by conditional pathogens.
2 Research progress of new strategies for mastitis treatment
2. 1 hormone regulates the secretion and repair of breast cells.
Hormones are widely used in reproductive physiology. The growth, development and secretion of mammary gland are regulated by cerebral cortex and hypothalamus, and various endocrine hormones play an important role [25-26]. Tong Huili et al. [27] established a normal cultured mammary epithelial cell line of dairy goats, treated with prolactin, and measured the lactose and total protein levels of mammary epithelial cells in the prolactin-treated group. The results showed that the secretion levels of lactose and milk protein of mammary epithelial cells increased significantly.
Chen Jianhui et al. [28] treated cow mammary epithelial cell lines with prolactin and progesterone, and determined the contents of casein and lactose in the treated cells. The results showed that the prolactin treatment group had an obvious upward trend, suggesting that prolactin could increase the number of mammary stem cells. Hormone has been proved to be helpful to improve the secretion ability of breast cells, improve the quality of milk and promote the recovery of breast tissue, but its application method and mechanism need further study.
2.2 Study on the regulation of breast cell apoptosis and related signal pathways
Studies have confirmed that the occurrence and development of mastitis is closely related to breast cell apoptosis and signal pathway. Xiao Yang [29] used tunnel method to detect the apoptosis of mammary gland tissue in different development stages of dairy cows, and confirmed that the signal of apoptosis was the strongest in the late lactation period. The differentiation, renewal and apoptosis of breast cells are closely related to the regulation of signal pathways, including Wnt signal pathway, Notch signal pathway and Hedge-hog signal pathway [26]. -catenin can initiate the expression of Wnt target gene; Depressed? -catenin signal, the differentiation and proliferation of breast cells are inhibited, the activation of Notch signaling pathway can promote the self-renewal of breast cells, and the over-expression of Notch will inhibit the differentiation of breast cells. Studies have shown that different forms of TP63 can promote the mitosis of breast cells by activating Hedgehog signaling pathway [30]. Zhang Wen [3 1] studied the secretion of cytokines and inflammatory mediators stimulated by lipopolysaccharide (LPS) and two common inflammatory signal transduction pathways NF-? B and MAPK changes, the results showed that under LPS stimulation, breast epithelial cells TRL4, NF-? The expression of B and downstream cytokines increased, which significantly inhibited the phosphorylation of p38, JNK, ERK and MAPKs. It is also expected to become a new direction of mastitis treatment to analyze the mechanism of various signal pathways in breast cell differentiation, renewal and apoptosis and to finely regulate breast cell apoptosis.
2.3 Study on regulating the number of neutrophils in breast tissue
After pathogenic bacteria, such as Staphylococcus aureus, invade the mammary gland of dairy cows, neutrophils concentrate in the infected mammary gland tissue, and play a phagocytic role to remove pathogens as the first line of defense to protect the body [32]. However, if PMN is over-activated or delayed in the inflammatory focus, a large number of PMN can aggravate the inflammatory reaction by releasing harmful substances such as oxygen free radicals, so that the inflammation is delayed, chronic or spread to the whole body [33]. Therefore, timely and appropriate removal of PMN is of great significance.
Wang Y et al [34] used low-intensity lasers of 650 nm, 2.5 MW and 30 MW/cm2 to treat LPS-induced mastitis model in rats. After low-intensity laser treatment, the aggregation of PMN to mammary gland acinus was inhibited, and the activity of myeloperoxidase was reduced, thus reducing the inflammatory reaction of mammary gland. Another study confirmed that the selenium content in the diet is directly related to the amount of PMN in the breast. Pathological sections of mouse mastitis induced by LPS showed that there was more PMN infiltration in the mammary glands of selenium-deficient mice, and the expression level of pro-inflammatory factors in the mammary glands was higher than that of mice with normal selenium content. Therefore, it is expected to adjust the amount of PMN in the breast by adjusting the selenium content in the diet, so as to prevent and treat mastitis in dairy cows [32].
To sum up, mastitis is a disease that seriously harms dairy industry. Because of its natural limitations, the therapeutic effect of antibiotics on mastitis is not ideal. Nisin, Aegis lysozyme, lysostaphin, CpG-DNA, platelet concentrate and other new preparations for the prevention and treatment of mastitis are expected to replace traditional therapeutic drugs. Hormone therapy, regulation of signal pathway and PMN number are expected to become new strategies for the prevention and treatment of mastitis. Actively carry out research on new preparations and new strategies for treating mastitis in dairy cows, and provide good conditions for efficient prevention and control of mastitis in dairy cows.
References:
[1] Sinha ·M·K, Mbary n, Mondal B. Mammalian subclinical mastitis: incidence, economics and inducing factors [J].Sci World J, 2014: 523984. DOI:10./kl.
[2] Song Yapan, Yang Liguo. Research progress on prevention and treatment of mastitis in dairy cows in China [J]. Dairy cows in China, 20 10 (12): 48-54.
[3], Yang Yongxin, Zhao. Comparison of breast tissues of clinical mastitis in dairy cows [J]. China Agricultural Science, 2009,42 (4):1442-1446.