Beno's Sporidiosis is a chronic parasitic protozoan disease that causes great damage to cattle, horses, antelopes, deer, and camels. The infected animals have the characteristics of skin hair removal and thickening. The disease has a wide range of parts. Next, let's get to know: the etiological analysis of Beno Sporidiosis in dairy cows and the preventive measures of Beno Sporidiosis in dairy cows.
Seven of 277 dairy cows raised in a dairy farm in Daqing City, Heilongjiang Province, suffered from the disease and showed obvious clinical symptoms. Routine immunization of cattle was normal and the development was good. Two cows appeared depression, anorexia, back hair loss, skin thickening and other symptoms a week ago, but did not attract the attention of the breeders. The disease gradually developed. Seven adult cows in the cattle herd had clinical symptoms. The cattle were fed with ivermectin and florfenicol before treatment, but the condition did not improve.
Visual examination and palpation were performed on affected cattle, such as skin, sclera and joints. These cattle have some common clinical symptoms, including knee swelling, superficial lymph node swelling, needle-tip-sized papules in the sclera and conjunctiva, skin thickening and sclerosis, especially in the breast, elbow, shoulder and neck. In addition, edema and erythema were more obvious in these areas, but the cattle did not feel any itching. Based on the above clinical symptoms, the author preliminarily speculated that these infected cows suffered from Benoisporidiosis.
Microscopic observation. Select the obvious symptoms of cattle's back, clean the excess hair on the back skin with shears, wipe and disinfect the sample with 70% alcohol, collect the papillary nodules on the surface of the diseased skin with ophthalmic forceps, and put them in sterile sampling bottles, and bring them back to the laboratory. The nodules were cut up and observed under a microscope. Numerous cysts suspected of Benozoite sporozoite were found.
Molecular biology diagnosis. DNA's extraction kit was used to extract total genomic DNA from the blood of infected cattle. The target fragment '1'was amplified by using the previously published PCR diagnostic method of Benozoite sporozoite. The upstream primers BesITSIF (5 & acute; - TGA CAT TTA ATA ACA ATC AAC CCT 37) and downstream primers BesITSIR (57 GGT TTG TAT TAA CCA ATC CGTGA 37) reacted with 25 uL system under the conditions of 95 5 min; 95 1 min, 50 45 s, 72 1 min, totally 35 cycles, and lastly 72 7 min. The amplified products of PCR were detected in an o.8% agarose gel electrophoresis apparatus. The results showed that the target bands of sporozoites were successfully amplified from 7 infected cattle. Based on clinical symptoms' observation, pathogen detection, and molecular biology methods, these dairy cows were diagnosed as Benoisporidiosis.
The final host of sporozoites Benois is a cat, and cattle are its intermediate host. When the final host eats meat containing the cyst of Benozoite sporozoites, it proliferates in the final host by merozoite reproduction and eventually forms oocysts which are discharged separately. The oocyst's sporulation in the external environment is called the oocyst of the infective stage and is infected by the intermediate host after feeding cattle. It is reported that Beno Sporidiosis can also be transmitted between cattle herds, mainly through blood-sucking insects, such as gadfly, to spread Beno Sporidiosis trophozoites in the blood of diseased cattle in cattle herds . The epidemic of Bovine Beno Sporidiosis occurred in July and August, and its epidemic time is closely related to the active time of blood-sucking insects. Also, it has been reported that there are tachyzoites of Benozoite sporozoites in cattle's tears, and the disease can be transmitted by some insects that feed on tears . The author analyzed that the reason for the cow disease on this farm was the spread of blood-sucking insect gadfly. Numerous Gadflies were found on the dairy farm. At the same time, many flies were sucking cow's tears, and there was also the possibility of fly transmission.
Because of the lack of specific drugs for the treatment of Benoriosporiasis, the prevention of this disease is particularly important. For the prevention of the disease, dairy farms should do the following. Firstly, a rapid and accurate diagnostic method for Beno Sporidiosis was established, which is the basis of prevention and control of Beno Sporidiosis in dairy cows. Secondly, it is necessary to establish and improve the evaluation system of Benozoite sporozoite in dairy cows. Once there are suspected cases, isolation or killing should be carried out immediately to eradicate the source of infection. Thirdly, because of the importance of insect transmission in cattle, insecticides are recommended to eliminate the source of transmission in the active period of insects in endemic areas.
Pathogens of Benoisporidiosis in Dairy Cows
Bernosporidia belongs to Sporozoa, Eucoccidia, Sarcosporidae, and Besnoitia, and B. Benoit parasitizes cattle. Cysts of sporozoites parasitize many parts of the skin, subcutaneous, connective tissue, fascia, serosa, respiratory mucosa and sclera of diseased animals. The cysts are grey-white, round and fine sand-like. They can be easily recognized by the naked eye. They are usually scattered, clustered or arranged in beads. The cyst wall is formed by host tissues and is divided into two layers: the outer layer is thick, homogeneous and eosinophilic; the inner layer is thin, with many flat megakaryons and no septum in the cyst. The cyst contains a large number of bradyzoites (cysts), the average size of which is 8.4 um x 1.9 um. It is banana-shaped, crescent-shaped or pear-shaped, with a tip, a round end and a nucleus close to the center. Tachyzoites (endogens) are sometimes found in blood smears of acute diseased cattle. The morphology and structure of tachyzoites are similar to those of bradyzoites. The average size of the tachyzoites is 5.9 um * 2.3 um.
The final hosts of Bernoulli bailey are cats, while the natural intermediate hosts are cattle, antelope, rabbits, and mice. However, its characteristic lesions mainly occur in natural intermediate hosts. The onset of the disease is seasonal. Blood-sucking insects may be the transmitters and hosts. The main route of transmission is the digestive tract.
After the cat swallowed the ovum and developed into an infectious oocyst, the sporozoites were released and entered the blood circulation through the gastrointestinal mucosa. The endothelial cells in the dermis, subcutaneous tissue, fascia and upper respiratory mucosa were proliferated by double buds, and numerous tachyzoites were produced. Tachyzoites are released with cell destruction and then invade other cells to continue to produce tachyzoites. This process continues, gradually stimulating the body to produce the corresponding antibodies, to enhance the body's resistance, thereby generating body response, tachyzoites wrapped and formed a capsule, at this time tachyzoites will disappear from the tissue. But the tachyzoites in the cysts became slow-growing ones. When the cat eats the bovine capsule, the bradyzoites in the intestinal mucosal epithelial cells and lamina propria become merozoites, which are used for the reproduction of merozoites and gametes, and the oocysts are excreted with feces. The oocyst is sporulated outside and contains two sporangia, each with four sporozoites. The oocyst becomes an infectious one.
Firstly, there was an increase in body temperature and cysts could be seen in the skin for 1-4 weeks. The incidence and mortality of cattle ranged from 1% to 20% and 10% respectively. Clinically, it can be divided into three stages: the initial body temperature rises to above 40 degrees C, lasting for 2-5 days. Sick animals are afraid of light and like darkness. The coat is dull, and sometimes edema occurs all over the body in the lower abdomen and limbs. The pace is stiff. Respiratory and pulse increase. Rumination diminishes or stops, occasionally with diarrhea. Abortion can occur in pregnant cattle. Superficial cervical and subiliac lymph nodes were enlarged. Tears, corneal opacity, scleral congestion, on which a large gray-white cyst with needle tips can be seen. The nasal mucosa is flushed and there are many cysts. Serous, purulent or blood-purulent nasal fluid. If the throat is injured, there is a cough. This period lasted about 5-10 days.
Hair shedding, skin thickening, cracking, bleeding out of mixed blood serum. Diseased animals lie on the ground for a long time and suffer from bedsores. Early edema subsided and scab occurred in elbow, neck, and shoulder. This period lasts from half a month to January. If the sick animals do not die, they will be transferred to the next period.
Dry seborrhea: In edematous skin, most of its hair falls off, forming a thick scab on the skin, like acarid skin or elephant skin. The lymph nodes are still enlarged. The sick animals are depressed and weak. The bull's testis enlarges at the beginning and atrophies at the beginning.
In addition to the pathological changes described in the symptoms, the subcutaneous hypertrophy of the diseased part was observed at autopsy. In the subcutaneous tissue, fascia and intermuscular connective tissue of head, limbs, back, waist, buttocks and thighs, numerous gray-white round cysts of Benozoite sporozoite were found. In mild cases, cysts were found only in the skin of the extremities, especially in the lower part. In severe cases, cysts were formed in the subcutaneous part of the whole body and the heel, lumbar ligament, deep toe, superficial flexion of the toe, gastrocnemius tendon, lateral extensor tendon and muscle tissue connected with aponeurosis. Also, the cyst patrol can parasitize the tongue, soft palate, throat, trachea, lung parenchyma, gastrointestinal mucosa, and omentum.
Skin and subcutaneous tissue: Cysts are mainly parasitic in the dermal papilla and subcutaneous connective tissue, occasionally in the epidermis. At the beginning of the disease, the epidermis is hyperkeratotic and hypertrophic due to marked cell proliferation. The connective tissue under dermis is proliferated by sporozoite parasitism. There are many lymphocytes and eosinophils infiltrating in the connective tissue, and the sebaceous glands, sweat glands and hair follicles atrophy or disappear.
Muscle: Cysts are scattered between skeletal muscle fibers, occasionally parasitic in the fibers. If cystic degeneration and necrosis occur, the cysts will die and disintegrate, and there will be obvious eosinophil and lymphocyte reactions around them.
Benozoite cysts can also be parasitic in the following organs: alveolar septum, lymph node capsule, and trabecula, subcutaneous vessels of the media and intima, rhabdomyosarcoma or sublingual connective tissue, laryngeal epiglottis submucosa connective tissue, tracheal mucosa lamina propria, testis and epididymis interstitium and gastrointestinal mucosa.
(1) Deep skin scrapes were used to examine the encapsulation and cysts of Benozoite sporozoites.
(2) Rabbits were inoculated with the blood of diseased cattle, and blood smears were made during fever.
(3) White cystic nodules 0.5mm in size were examined at the skin and subcutaneous sites during postmortem dissection.