In hot, rainy seasons, pig farms fear acute high fever the most, with a mortality rate of up to 80%
Acute, high fever, 80% mortality! In hot, rainy seasons, pig farms fear it the most!
Swine erysipelas is an acute, high-fever infectious disease caused by Erysipelothrix rhusiopathiae. It mainly occurs in growing pigs aged 3 to 12 months, and susceptibility decreases with age. It can occur in all four seasons, but is most prevalent in hot, rainy seasons, and the mortality rate can reach as high as 80%.
2. Causes
① Dirty and damp pens;
② Feeding wet feed, especially if dairy by-products are used, promotes the reproduction of pathogens;
③ The water supply system is contaminated by pathogens;
④ Intake of feces;
⑤ Stress caused by moving and mixing pigs;
⑥ Sudden temperature changes, high summer temperatures;
⑦ The drinking water system is contaminated by pathogens;
⑧ Sudden change of diet;
⑨ Continuous production without emptying and disinfecting the barn;
⑩ Viral infection, especially porcine reproductive and respiratory syndrome and influenza;
⑪ Pig houses with straw in the resting area are more prone to outbreaks, because Erysipelothrix rhusiopathiae can survive in straw.
3. Clinical symptoms
1. Acute type
This type is common and is characterized by sudden outbreaks, an acute course, and high mortality. Sick pigs are listless and have persistent high fever; they do not eat and vomit; conjunctival congestion occurs; feces are dry and hard, with mucus attached. Piglets develop diarrhea in the later stage. The skin of the ears, neck, and back is flushed and purplish. Before death, irregular bright red patches appear under the axillae, on the inner thighs, and in the abdomen, which fade under finger pressure and then merge together. Death often occurs within 3-4 days, and those that do not die turn into the urticarial type or chronic type.
2. Subacute type (urticarial type)
The disease is milder. In the first one or two days, clearly demarcated, round or quadrangular, hot urticarial patches appear on the sides of the chest, back, neck, and then the whole body, commonly known as "fire stamps," and they fade under finger pressure. The patches protrude 2-3 mm above the skin, are about 1 to several cm in size, and range from a few to dozens in number; after drying, they form brown scabs. Sick pigs are thirsty, constipated, vomit, and have a high body temperature. After the patches appear, the body temperature begins to drop, the condition eases, and after several days to more than ten days, the sick pigs recover on their own. There are also many sick pigs whose symptoms worsen during the course of the disease and change into the septicemic type and die. The course of disease is about 1-2 weeks.
3. Chronic type
It develops from the acute type or subacute type, and there is also a primary form. The common forms include chronic arthritis, chronic endocarditis, and skin necrosis.
The chronic arthritis type manifests as inflammatory swelling of the limb joints, with stiff and painful affected legs, showing lameness in one or two limbs or inability to stand. The sick pigs have a normal appetite, but grow slowly, are physically weak, and emaciated. The course of disease is several weeks or months.
The chronic endocarditis type mainly manifests as emaciation, anemia, general weakness, preference for lying down, and aversion to moving; when forced to walk, they move slowly, sway all over, and breathe rapidly. Such sick pigs cannot be cured, and usually suddenly fall down and die due to cardiac paralysis. The course of disease is several weeks to months.
Chronic swine erysipelas sometimes causes skin necrosis. It often occurs on the back, shoulders, ears, hooves, and tail. The local skin swells, bulges, becomes necrotic, black, dry and hard, and leather-like.
4. Necropsy symptoms
The gastric and intestinal mucosa are congested and hemorrhagic; the liver is congested and reddish-brown; the kidneys are enlarged and dark red, with hemorrhagic spots on the surface; the spleen is enlarged and cherry-red, soft in texture, with a raised cut surface, and the splenic pulp is easily scraped off. The lymph nodes are congested and enlarged, red or blackish-red, juicy on the cut surface, with hemorrhagic points. The urticarial type is characterized by skin patches. The chronic type shows joint swelling, with a large amount of serofibrinous exudate, sticky or red. The endocardium has verrucous vegetations, resembling cauliflower.
Hemorrhage on the surface of the myocardium
Diffuse hemorrhage in the gastric fundus
No obvious enlargement of the kidneys
The spleen is dark, with no obvious enlargement
Ulcers and scabs
Pulmonary congestion
5. Prevention and control plan
1. Drug health care
During high-incidence seasons, the following drugs can be alternately added to the feed: cephalosporins, amoxicillin, tylosin, and some tetracycline drugs. Biosecurity measures on farms are the primary measure for controlling PRRS, and good management of the pigs' "food, clothing, housing, and transport" should be ensured.
2. High attention from management personnel
Pay high attention to sudden death with fever (40-43°C), conjunctival flushing, generalized redness, and no papular patches, and assign dedicated personnel to follow up on the improvement of the disease.
3. Do a good job in environmental disinfection
Focus on the humidity and hygiene of the breeding pens, gestation pens, and exercise yards, and carry out timely and appropriate flushing and disinfection of pens, especially regular thorough flushing and disinfection of the breeding pens. Ensure that the exercise yard has no standing water, and disinfect scattered feed regularly; potassium permanganate can be used.
4. Regular external deworming
The concentration and frequency of external deworming drugs should be reasonable to ensure the integrity of the pig's skin.
5. Do relevant immunization well
Do relevant immunization work well,Breeding pigsare immunized once every six months. For attenuated vaccine immunization: immunize via drinking water or mixing with feed, and a booster immunization is needed once after an interval of one week.
Antibiotics and Chinese herbal medicines should be suspended for one week before and after immunizationTreatment. The water used for immunization should be clean, and no disinfectant should be added. Do not use fermented or rancid feed, or feed mixed with hot water.
6.Treatmentplan
1. Handling of sick pigs ⟦55 Early detection and early handling: when a few suspicious cases appear in a local area, promptly carry out harmless disposal of suspected sick pigs, isolate and disinfect the contaminated area, and bag and handle the manure of affected pigs.
Early detection and early handling: when a small number of suspected cases appear in a localized area, promptly and safely dispose of suspected diseased pigs, isolate and disinfect contaminated areas, and bag the manure of affected pigs for disposal.
2. DrugsTreatment
Select sensitive drugs to administer to the entire unit or whole barn of affected pigsTreatment, such as amoxicillin, cephalosporins, penicillin, etc., plus VC, multivitamins, and heat-clearing and detoxifying Chinese herbal medicines, for 5 consecutive days.
For acute cases, fast-acting penicillin can be usedTreatment, twice a day for three consecutive days; alternatively, long-acting penicillin can be used, onceTreatment, covering 48 hours, and it can also be given again afterward.
3. Use and cleaning of the exercise yard
Suspend the use of the pig farm exercise yard. The exercise yard needs to have its sand turned or replaced, be disinfected with disinfectant, and maintain unobstructed water flow with no standing water. Strengthen the disinfection of feed troughs, drinking water, and the environment.
4. Vaccination
If individual cases appear among finishing pigs, the pens should be cleaned and disinfected between different batches. If the growing pig herd continues to develop the disease, vaccination is necessary, once at 8 weeks of age, and preferably again at 10-12 weeks of age. Generally, no vaccination is given before 8 weeks because maternal antibodies will affect the vaccination effect.