How to prevent and treat ovine contagious ecthyma? A detailed guide to practical methods

Ovine contagious ecthyma, also known as contagious pustular dermatitis of sheep, is a contact infectious disease of sheep and goats caused by a virus, characterized by the formation of papules, vesicles, pustules and wart-like scabs on the lips, tongue, nose, udder and other parts. The ovine contagious ecthyma virus belongs to the family Poxviridae and the genus Parapoxvirus; in negatively stained specimens, the virus particles have a characteristic skein-like appearance. The antigenicity of viruses isolated from different regions is not completely identical. This disease occurs mostly in lambs aged 3 to 6 months and often appears in outbreaks; adult sheep in epidemic areas mostly have a certain degree of resistance. This disease is widely distributed in various countries and regions around the world. In the main sheep-raising areas of China, such as **, Gansu, Qinghai, Yunnan, Inner Mongolia and the three northeastern provinces, this disease is present.

I. Preventive measures

1. Because this disease is mainly transmitted through trauma, and lambs aged 7 to 25 days are in the teething period and like to lick foreign objects, which easily injures the oral mucosa, it is necessary to prevent injury from awns and prickles in feed and bedding, keep the lambing pens dry, spread clean and soft bedding, and add an appropriate amount of salt to the feed to reduce the chance of gnawing on soil walls and protect the oral mucosa from injury.

2. In areas where this disease is epidemic, an attenuated vaccine strain identical to the locally prevalent strain can be used for immunization. The Gansu Provincial Institute of Animal Husbandry and Veterinary Medicine of China, through continuous passage in calf testicular cells, developed an attenuated strain into a freeze-dried live vaccine, suitable for scratch inoculation on the lower lip mucosa of sheep and goats of various ages, with an inoculation dose of 0.2 ml per animal; it can also be inoculated by scratching the skin on the inner side of the thigh, with an immunity period of 3 months, and when used on a large scale in the field, the protection rate reaches more than 80%. In addition, the Qinghai Provincial Academy of Animal Husbandry and Veterinary Sciences also successfully developed an attenuated vaccine using the same method. When used, it is injected into the oral lip mucosa or inoculated by subcutaneous scratch on the inner side of the thigh of newborn lambs, with an inoculation dose of 0.2 ml in both cases; the immunity period can reach 5 months, and the challenge protection rate reaches more than 3/4. Some reports state that the attenuated cell vaccine produced by the Lanzhou Biological Products Factory can provide a protection period of up to 18 months; when used, it is inoculated under the lip mucosa at 0.2 ml per sheep, and immunity is produced after 15 days. Pregnant ewes are vaccinated 30 days or 15 days before lambing, and newborn lambs can obtain high levels of antibodies from the dam's colostrum.

3. Because there is cross-neutralization between the viruses of ovine contagious ecthyma and goat pox, after immunizing goats in China with an attenuated goat pox vaccine cultivated at low temperature, the vaccinated goats show no local reaction or only a mild reaction, but they can resist challenge with virulent ovine contagious ecthyma virus; therefore, inoculation with attenuated goat pox vaccine can also be used for immune prevention. In a certain place in ** where an outbreak occurred, someone once used goat pox vaccine produced by the Qinghai Provincial Biological Products Factory to urgently vaccinate 4,063 threatened lambs; 150 became ill, and the immune protection rate reached 96.31%.

4. In epidemic areas of this disease, scabs from naturally affected sheep can also be collected, ground, and made into a 1% virus suspension with 50% glycerol saline buffer, then inoculated by scarification at the hairless area at the base of the tail of healthy sheep. After about 7 days, inflammation or pustular lesions appear at the inoculation site, followed by scabbing, and after several weeks the scabs fall off. This method of immunization can produce lasting immunity (for about one year). Vaccination of ewes should be completed 3 to 4 weeks before parturition. This method carries the risk of spreading the virus, so it is limited to use in epidemic areas.

Generally speaking, attenuated vaccines are relatively safe, while inactivated vaccines are less effective. However, some people abroad have also used papilloma tissue from muskoxen infected with this disease, inactivated it with glutaraldehyde, added Freund's adjuvant and emulsified it, and then inoculated 2-month-old muskoxen, which protected them from infection.

II. Treatment measures when an outbreak occurs

Several successful treatment methods reported in recent years are excerpted as follows:

1. Melt 1 kg of marmot (hamster) oil and mix it evenly with 300 g of trichlorfon, then apply it to the affected area; recovery occurs after 1 day. This method has been used to treat more than 12,000 sheep, all of which were cured.

2. Mix ribavirin (ribavirin injection) 100 mg/mL and dexamethasone injection 5 mg/mL at a ratio of 2:1 and inject intramuscularly; adult sheep 3 ml, lambs half or 2 ml; apply iodine glycerin or gentian violet topically. Generally, use for 2 to 3 days, with good results and a high cure rate. In severe cases, combine with penicillin and streptomycin twice daily.

3. Use disinfected surgical scissors and tweezers to remove the scabs and pustule skin from affected sheep, disinfect the wound surface with strong disinfectant spirit solution, then mix Bingpeng San powder (borneol 50 g, borax 500 g, glauber's salt 500 g, cinnabar 30 g, ground into powder and mixed evenly) with water into a paste, apply it to the affected area, apply once every other day, for 2 to 3 consecutive applications, with treatment for 7 to 10 days, until the scabs or crusts at the affected area fall off. A total of 28 cases were treated, and all were cured. As auxiliary measures, the sick sheep were kept in isolation, and 1 g/L strong disinfectant spirit was used to disinfect sheep pens, sites and the environment twice daily until the sick sheep recovered.

4. The wound surface may be coated with one of the following drugs: 2% gentian violet, or 3% iodine tincture glycerin (iodine 3 g, potassium iodide 5 g, dissolved in 75% alcohol 10 ml, then add glycerin 10 ml), or iodine-pine-tar-stone mixture (iodine tincture 1 part, pine tar 1 part, paraffin oil 1 part). Use twice daily for 3 consecutive days. Sulfonamide powder may be dusted on the wound surface. Alternatively, rinse the ulcer surface with light saline and then spray on Bingpeng San (borneol 15 g, borax 150 g, mirabilite 18 g, ground into fine powder) twice daily; after 2 days, new granulation tissue grows on the ulcer surface, and this method has a very good curative effect. In cases of mixed infection, combine with sulfonamides and antibiotics for anti-inflammatory treatment, fluid supplementation and other measures.

5. After removing the scabs, first wash the wound surface with 0.1% potassium permanganate water, then apply one of the following drugs: (1) A mixture of 3% iodine tincture, pine tar oil and paraffin oil (1:2:2), stirred evenly before use. (2) Nitrofural and ichthammol ointment (1:4); (3) iodine glycerin (70 ml of 7% iodine tincture plus 30 ml of anhydrous glycerin), all applied once daily for 7 consecutive days, then after 3 days proceed to the next course of treatment.

6. The ulcer surface can also be coated with the following traditional Chinese medicines: (1) A mixture of bletilla powder, vegetable oil and borneol (10:5:1), stirred evenly; (2) equal parts of human middle white, artificial cattle bezoar, indigo naturalis, borneol, gypsum and catechu, all ground into powder; (3) indigo naturalis 9 g, Phellodendron chinense 9 g, Coptis chinensis 6 g, Platycodon grandiflorus 6 g, catechu 6 g, mint 3 g, ground into powder; (4) Kou Ji Ling: more than ten drugs including indigo naturalis, Phellodendron chinense, Viola mandshurica, dried alum and galla chinensis, ground into fine powder and mixed with water into a paste. (5) catechu 15 g, dried salt 12 g, human middle white 9 g, Coptis chinensis 9 g, calcined alum 9 g, indigo naturalis 6 g, all ground into fine powder and applied or sprayed into the oral cavity; the above drugs are applied 1 to 2 times daily. Use cotton dipped in 50 g/L copper sulfate aqueous solution to wipe off the hard scabs, then apply iodine glycerin (50 g/L iodine tincture 100 mL, glycerin 100 ml) to the affected area.

7. After washing the hoof area, soak it in 50 mL formalin solution for 2 minutes, once daily for 2 consecutive days; if not cured, soak again after 1 week. After the above treatment for one week, the symptoms are significantly reduced, and 2 courses of treatment can achieve cure. Contaminated bedding should be burned, and equipment should be disinfected, for example with 20 g/L sodium hydroxide, 100 g/L lime water or 200 g/L hot plant ash water, etc. The hoof area can also be soaked in 10% zinc oxide or zinc sulfate or 5% formalin, then coated with 10% chloramphenicol solution in alcohol or propylene glycol, or coated with oxytetracycline or polymyxin ointment.