What to do about Mycoplasma suis infection in pigs? Detailed explanation of prevention and treatment methods
Mycoplasma suis infection in pigs (abbreviated as M. suis disease) is not a new disease; it was reported in India as early as 1932, but it had long received no attention. Only in the past two years has the disease suddenly become more common, occurring and spreading in many regions and pig farms across the country, which is what has drawn people's attention. The disease is characterized by anemia, jaundice and fever. Its harm lies in the economic losses caused by the decline in pig production performance, including increased intestinal and respiratory infections, reduced sow fertility, delayed marketing of finishing pigs, and so on.
1. Pathogen M. suis was previously considered a protozoan, and the disease it caused was called "anaplasmosis-like disease". Now, based on biological characteristics, it is considered a rickettsia. M. suis is relatively sensitive to drying and chemical drugs; ordinary disinfectants can kill it within a few minutes, but its resistance to low temperatures is relatively strong.
2. Epidemiological characteristics Pigs of all ages and breeds are susceptible, but exotic breeds are more susceptible; sows, weaned piglets and fast-growing feeder pigs are more frequently affected, and their symptoms are also relatively more severe. The disease is transmitted by at least four routes: blood-borne, contact, vertical and vector insects, with mosquitoes, biting flies, lice, midges and other blood-sucking insects as the main transmission vectors.
Epidemiological investigations show that the occurrence of this disease coincides with the presence of mosquitoes; using mosquitoes for natural inoculation can reproduce the same cases. The occurrence of this disease is affected by many factors; farrowing, long-distance transport, poor feeding and management, mixing groups, feed changes, etc. all contribute to the occurrence of the disease. In particular, adverse factors such as high temperature and humid heat in summer and autumn and the breeding and biting of blood-sucking insects, large-scale intensive feeding methods, as well as contaminated injection needles, surgical instruments, piglet tail docking, tooth clipping and ear notching, may all promote infection and disease in pigs.
3. Clinical symptoms The incubation period is about 6-10 days, and the course of disease varies from a few days to several years. It mostly presents as latent infection or a chronic wasting course, with unobvious clinical symptoms. Acutely infected pigs first develop pneumonia, showing high fever, pale skin and mucous membranes, emaciation, slow growth, cyanosis and necrosis of the limbs, especially the edges of the ear pinnae, and sometimes jaundice and diarrhea are seen; the daily weight gain of finishing pigs decreases, and acute hemolytic anemia is likely to occur. In the later stage, enteritis and diarrhea often occur secondary. Chronically diseased pigs show anemia and emaciation and often become stunted pigs. Mycoplasma suis can persist in pigs for a long time, and recovered pigs can carry the organism for life.
After infection, sows show acute infection, poor appetite, persistent high fever (40-42°C), anemia, rapid breathing, pale skin, and reduced or absent milk, mostly seen after farrowing; chronically infected sows are emaciated and weak, with anemia, jaundice and tissue hemorrhage, and may also develop reproductive disorders such as reduced conception rate, delayed estrus, abortion and stillbirth.
4. Diagnosis The diagnosis of Mycoplasma suis is mainly through direct microscopic examination, including fresh blood wet mounts and stained smears. One drop of ear vein blood can be mixed with 1 drop of normal saline, spread evenly, then covered with a coverslip, and examined under oil immersion after focusing the field under high power. There are many serological testing methods, such as complement fixation reaction, indirect hemagglutination, fluorescent antibody, ELISA, etc., and some people abroad also use PCR for diagnosis.
5. Prevention and treatment In principle, medication should be used early. Commonly used drugs include blood parasite clear, yellow pigment, arsanilic acid, tetracycline, oxytetracycline, kanamycin, gentamicin, etc. At the same time, auxiliary symptomatic treatment and disinfection work should be carried out. For example, blood parasite clear can be prepared into a 3%-5% concentration with sterile water for injection or normal saline or 5% glucose injection, and injected intramuscularly at 4 mg/kg body weight; arsanilic acid at 300 mg/kg feed, mixed evenly and fed for one week; for prevention, at 90 mg/kg feed, mixed and fed for 1 month.