Harm and Prevention of Digestive tract Diseases in Pigs in Autumn and Winter

Entering the autumn and winter season, the decrease of temperature and sunshine, coupled with the changeable climate, is easy to decrease the resistance of pigs and lead to the infection of pathogenic microorganisms, so autumn and winter is the season of frequent occurrence of infectious diseases in pigs, in which digestive tract diseases of pigs are the most common, especially to piglets. There are many causes of digestive tract diseases in pigs, including infectious and non-infectious factors. Among the infectious factors, diarrhea caused by bacteria and viruses is the most serious, including yellow and white dysentery of piglets, red dysentery of piglets, paratyphoid fever of piglets and porcine dysentery; viral diarrhea includes porcine transmissible gastroenteritis, porcine epidemic diarrhea and porcine rotavirus infection. In addition, parasitic infections and some non-communicable factors such as environment and nutrition can also cause diarrhoea. The outbreak of digestive tract diseases in pig farms is often caused by a variety of pathogenic factors, which aggravate the disease and it is difficult to distinguish the pathogens. If appropriate measures are not taken in time, it will bring huge economic losses to pig production. The harm, prevention and treatment of digestive tract diseases in pigs are reviewed in this paper.

1 bacterial diarrhea

1.1 Red dysentery of piglets: the pathogen is Clostridium welchii type C. It can cause highly lethal enterotoxemia in 1-week-old piglets, especially 1-3-day-old piglets. Clinical manifestations are the discharge of pink blood stool, some mixed with small bubbles, sick pigs do not feed, cold environment is sensitive, trembling all over. The disease has the advantages of rapid onset, short course and high mortality. The lesion site is mainly ileum and jejunum, and the appearance is dark red. Autopsy showed that a large amount of red ascites accumulated in the abdominal cavity, the intestine was full of blood-like contents, jejunal villus necrosis, extensive bleeding of intestinal mucosa and submucosa, and bright red mesenteric lymph nodes.

1.2 Yellow and white dysentery of piglets: the pathogen is pathogenic Escherichia coli. Yellow dysentery is also known as early-onset colibacillosis because it occurs frequently in piglets at the age of 1 week. The main clinical manifestation of yellow dysentery is the discharge of mushy thin feces, the color is yellow or yellow-white, and the feces contain small curd tablets, small bubbles and mucus. The course of disease is short and the mortality rate is high. The dead piglets were severely dehydrated, and edema was observed under the skin of the neck and abdomen, the skin under the abdomen was purplish red, and the anal vulva was red; the gastric fundus was dark red, yellow and sour milk clots filled the stomach; the swollen intestine contained a large amount of yellow liquid content and gases, and the mucosa of the intestine, especially the duodenum, showed acute catarrhal inflammation; mesenteric lymph node dot bleeding. The piglets with white dysentery are mostly 10-30 days old, so it is also called delayed colibacillosis. The clinical manifestation is the discharge of milky white, yellowish, grayish white sticky feces with a special fishy smell. Usually, when the body temperature and appetite of sick pigs are normal, diarrhea occurs suddenly, the course of disease is long, the mortality rate is low, and the dead pig corpses are pale and emaciated. Autopsy also shows that there are a large number of milk clots in the stomach and yellow-white, gray-white thick and thin feces in the intestinal cavity. Small intestinal mucosal catarrhal inflammation, thin and transparent intestinal wall, slight redness and swelling of mesenteric lymph nodes.

1.3 Piglet paratyphoid: the pathogen is salmonella, which mainly infects pigs aged 1-4 months. It is more common in cold and rainy winter and spring, and is locally epidemic or sporadic. Mixed infection with classical swine fever and classical swine asthma is more common. In terms of clinical symptoms, the acute type showed constipation first, followed by dysentery, and the excreted stool smelled; the chronic type showed constipation first, followed by persistent or intermittent diarrhea, and the excreted feces were mixed with blood, necrotic tissue and cellulose fragments, the color was yellow or yellowish green, and the smell was foul. Autopsy showed that necrotizing enteritis sometimes spread to the cecum, colon and posterior ileum, the intestinal wall thickened and the submucosa was covered with a layer of diffuse necrotic material. There are swollen lymph nodes and necrotic foci in the liver and kidney.

1.4 Porcine dysentery: the pathogen is Treponema pullorum, which is a highly contagious mucinous, hemorrhagic diarrhea disease. Other microorganisms in the intestinal tract are also involved in the pathogenicity of the pathogen. Pigs of all ages could be infected, but the main targets were 6-12-week-old piglets. The clinical manifestation is to discharge yellow or gray soft stool first, then discharge water-like stool, blood, liquid and membrane are mixed in the stool. The main pathological changes were catarrhal hemorrhagic inflammation of the large intestine, obvious demarcation of the ileal valve, swelling of the large intestinal mucosa and covered with mucus and cellulose with blood clots.

2 viral diarrhea

2.1 Porcine transmissible gastroenteritis: it is a highly contagious intestinal infectious disease caused by porcine transmissible gastroenteritis virus. Pigs of all ages can be infected, and the older the infected pigs are, the lower the mortality rate is. Piglets within a week of age generally experience only 2-7 days from clinical symptoms to death, and the mortality rate can be as high as 100%. Adult pigs can recover gradually after 3-7 days of diarrhea, but their physique is weak and stiff pigs may be formed within a period of time. The sick piglets showed severe watery diarrhea, vomiting and dehydration. The clinical symptoms of fat pigs, sows and boars are different. Common symptoms are anorexia, vomiting occurs in individual cases, and the discharge of seriously ill pigs is in the shape of a spray. After infection, the disease of lactating sows is serious, with elevated body temperature, accompanied by anorexia, vomiting and diarrhea, resulting in the cessation of lactation, which is also another factor leading to the high mortality of piglets. Stomach and small intestine are the main lesions of the disease. The stomach is full of milk clots and the fundus mucosa is congested. The small intestine is congested and the intestinal wall becomes thin and shiny, filled with yellowish green or gray-white liquids, containing foams and undigested milk clots. Mesenteric lymph node congestion and edema.

2.2 Porcine epidemic diarrhea: an acute, highly contagious disease caused by porcine epidemic diarrhea virus. Winter is a frequent season, and suckling piglets have the most serious disease, and the mortality rate can reach 80% 100% [6]. The morbidity of shelf pigs and finishing pigs is also very high, but the mortality rate has been reduced. Mixed infection with transmissible gastroenteritis is very common, and the main clinical symptoms of piglets are difficult to distinguish from transmissible gastroenteritis, such as vomiting, dehydration and watery diarrhea. The lesions only occurred in the small intestine, small intestinal dilatation, intestinal wall thinning, filled with yellow fluid, intestinal villi atrophy, mesenteric congestion, mesenteric lymph node hyperemia and edema.

2.3 Porcine rotavirus infection: is caused by rotavirus, a variety of newborn animals, including piglets, including important intestinal pathogens. Late autumn, winter and early spring are frequent seasons of the disease, showing an endemic epidemic. Pigs of all ages can be infected by the virus, and the infection rate is as high as 90% mi 100%. Adult pigs in most disease endemic areas can be immunized, and the disease is most serious in piglets under 8 weeks old. The younger the age is, the higher the incidence and mortality rate is. The pathological changes of piglets infected with rotavirus were mainly limited to the digestive tract, the gastric activity was relaxed and filled with milk clots and milk, the small intestinal wall became thin and translucent, the intestinal contents were serous or thin as water, intestinal villus atrophy, mesenteric lymph node edema and gallbladder enlargement.

3 parasitic diarrhea

3.1 Porcine coccidiosis: a protozoa caused by porcine isosporidium and some Eimeria coccidiosis parasitic on small intestinal epithelial cells of piglets. Piglets are susceptible to infection at the age of 8-15 days, and the seasons with high incidence are summer and autumn. Most of the clinical symptoms of diseased pigs were yellow or yellow-white feces, which were sticky at first, and watery feces were discharged 1-2 days later. Sick pigs died or were weak, emaciated and stunted, often due to dehydration. Most of the foreign bodies covered the mucosa of jejunum and ileum of sick and dead pigs, and the intestinal villi atrophied and fell off.

3.2 nematodes: the nematodes parasitic in the digestive tract of pigs are: Trichuris, Ascaris lumbricoides, Trichuris, sarcoidosis, Angiostrongylus, hookworm, esophageal nematode and so on. Piglets are the main targets, accompanied by abdominal pain and intractable dysentery. There is mucus, pus and bloody dysentery in the stool. The disease can occur in free-range and large-scale pigs.

3.3 trematodes: clonorchiasis ginger is the main trematodes that cause dysentery in pigs, and humans can also be infected by this worm. Ginger fluke parasites in the small intestine of pigs, causing inflammation of the intestinal mucosa, causing anemia, weight loss, and dysentery.

Toxoplasmosis: as one of the main diseases of pigs, toxoplasmosis is a zoonotic protozoonosis. The main symptoms of diseased pigs are as follows: mucus on the surface of fecal ball in the first stool, high fever (40.5-42 ℃), loss of appetite, and cyanosis in the later stage of dysentery, limbs, abdomen, ears, and other skin.

4 non-infectious etiology

4.1 Environmental diarrhea

Due to the low temperature in autumn and winter, piglets are prone to diarrhea syndrome under stress, such as sudden changes in temperature, continuous rain, damp and cold, ventilation and sanitation, and sudden changes in the environment, which lead to stress response, which become the inducement of porcine diarrhea. At low temperature, breeding pigs and large pigs can produce adverse stress reactions, nutritional metabolism occurs inside the body, resulting in functional disorders, while external pathological symptoms such as diarrhea or constipation. Farm staff can not effectively implement veterinary health system management and biosafety prevention measures, resulting in harmful gases, pathogenic microorganisms content exceeding the standard, leading to digestive tract diseases.

4.2 nutritional diarrhea

Long-term lack of certain nutrients or improper collocation will lead to gastrointestinal mucosal dysplasia and abnormalities (inflammation, necrosis and exfoliation) in pigs; insufficient nutrients in feed affect the quantity and quality of breast milk, such as insufficient VB or excessive protein and lipid content in breast milk, which can cause gastrointestinal dyspepsia and cause dyspepsia and diarrhea Protein molecules that are not fully decomposed by digestive enzymes enter the large intestine for fermentation, and the final products of fermentation include toxic amines, tyramine, histamine and cadaveric toxins, which can cause inflammation of the digestive tract, reduce intestinal secondary absorption and secondary infection; uneven feeding and overeating cause immediate diarrhea in pigs; accidental ingestion of toxic substances and chemical drugs such as acid, alkali and arsenic can also cause diarrhea.

5 Prevention and treatment of digestive tract diseases in pigs

5.1 Prevention and treatment of bacterial diarrhea

Due to the abuse of antibiotics in recent years, the drug resistance of bacteria has gradually increased. Relatively sensitive drugs should be selected in the treatment of bacterial diarrhea, and the dose should be large enough and the course of treatment should be long enough. Sulfonamides or antibiotics can be selected for treatment, such as sulfamethazine, sulfamidine, gentamicin, florfenicol and so on. Treatment should adhere to the principle of treating both mother and baby, that is, if there is one disease in the same litter, the whole litter of piglets should be treated. While taking drugs, attention should be paid to improving the environment and hygiene, enhancing nutrition and promoting the rehabilitation of sick pigs.

5.2 Prevention and treatment of viral diarrhea

Since there is no specific drug for the treatment of viral diarrhea, it can only be prevented by vaccine immunization. Immunization is an important measure to control the occurrence of infectious diseases. at present, the main vaccines used to treat viral diarrhea are porcine transmissible gastroenteritis and porcine epidemic diarrhea inactivated vaccine, porcine transmissible gastroenteritis and porcine epidemic diarrhea live vaccine. Porcine transmissible gastroenteritis, porcine epidemic diarrhea and rotavirus live vaccine. Because live vaccine can stimulate both humoral immunity and cellular immunity, and can produce antibodies more quickly, the effect of live vaccine is better than that of inactivated vaccine. The use and preservation of the vaccine should be carried out in strict accordance with the instructions. In practical application, the corresponding immunization measures can be formulated according to the epidemic situation of the local epidemic disease and the actual situation of pig farms. At the same time, scientific immunization procedures should be adopted according to the health status of the body and the maternal antibodies in young pigs. Antibody monitoring can be carried out if possible, and immunization procedures can be determined unconditionally according to the successful experience of pig farms under the same conditions.

5.3 Prevention and treatment of parasitic diarrhea

Because coccidiosis is prone to drug resistance, it is necessary to plan to use anti-coccidial drugs alternately or in combination with anti-coccidial drugs in treatment or prevention. Most of the therapeutic drugs are oral sulfonamides, coccidiolide or diclazuril. In order to achieve the best therapeutic effect, early treatment is necessary. Nematode treatment and prevention drugs include levamisole, albendazole, ivermectin and so on. Toxoplasma gondii is treated with sulfonamides, such as pentamethoxy sulfadiazine, hexamethoxy sulfadiazine, compound sulfamethoxazole and so on. In order to achieve the preventive effect, it is necessary to ensure the good sanitation of the pig farm and its surrounding environment, it is forbidden to raise cats, beware of oocyst contamination of feed and drinking water, pig feeding is prohibited to use raw meat crumbs, swill should be cooked. Trematodes are treated with praziquantel, thiobichlorophenol, nitrothiocyanamide and so on.

5.4 Integrated prevention and control

Strengthen nutrition: supply full-price feed for pigs, ensure balanced nutrition supply for pigs, strictly prevent the lack of vitamins and trace elements, and resist pathogens by improving feed quality and enhancing resistance of pigs. In particular, the defense against intestinal pathogens can reduce the possibility of outbreaks of intestinal diseases in pigs. Provide an adequate supply of clean and hygienic clean water. Cold water sources that are strictly protected from contamination by pigs' diet.

Heat preservation: suitable temperature can not only ensure better resistance of piglets, but also prevent newborn piglets from being crushed to death for fear of being cold close to sows. Usually, the temperature of newborn piglets should reach 30-35 ℃ at 1-3 days old, 27-30 ℃ at 4-7 days old, and 22-26 ℃ at 8-30 days old. The main methods of piglet heat preservation are: incubator, insulation lamp, adding heating equipment and so on, close the doors and windows, prevent the gap, prevent the cold wind from entering the pigsty, and try not to flush the pigsty with water in the cold season.

Disinfection: appropriate disinfectants and disinfection methods should be selected according to the types and characteristics of pathogens, acid and aldehyde disinfectants can be selected for pig disinfection, alkali disinfectants can be used for empty house disinfection, and efficient disinfectants should be selected as far as possible to achieve better disinfection effect and ensure sufficient disinfection dose. Sow delivery room should be thoroughly cleaned, washed and disinfected, disinfection pool and disinfection room should be set up at the door of the delivery room, and vehicles and personnel entering and leaving should be strictly disinfected. A regular disinfection system should be established at ordinary times. It is recommended that it is best to disinfect 1-2 times a week, and now disinfect pigs with disinfectant to carry out spray disinfection. This practice can play a role in the inhibition and spread of the disease, and achieve the goal of reducing the infection rate of the disease. Once infectious diseases are found in pig farms, pig sheds and appliances should be disinfected once a week, and serious cases can be disinfected every 1 day. When disinfection, need to clean the manure and dirt in the enclosure first, then shovel off the surface soil, and finally use disinfectant to disinfect.

Isolation: it is strictly forbidden to introduce piglets and breeding pigs from diseased pig farms. The best method that pig farms can adopt is self-breeding and self-breeding. Determine the need for external introduction of piglets, must be isolated and observed for 30 days, once the problem occurs, solve in time to prevent the spread of the disease. At ordinary times, breeders should do a good job in the prevention and inspection of pig diseases, and should be isolated in time and actively treated to prevent the spread of the epidemic once the epidemic is found.

In a word, pig digestive tract disease has always been the main disease troubling pig farms in autumn and winter, and the etiology is very complicated. pig farms must give priority to prevention of pig digestive tract diseases, while taking immunization and drug treatment, we should achieve scientific, standardized feeding and management, do a good job in biosafety measures, and establish a series of comprehensive prevention and control measures to ensure the sustainable and stable development of pig production.