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Chlamydia of cattle (Latin - CrJamydophila abortus; English - Chlamidiosis of cattle; chlamydia, or enzootic, abortion of cows) - predominantly chronic disease of cows, characterized by damage to the membranes, abortions, premature birth of dead or non-viable calves.
Historical background, distribution, degree of danger and damage. Chlamydia in cattle was first described in 1923 by Fraum and Hart in the United States. The causative agent of chlamydia is isolated from the aborted fetuses of cows by the French scientist Giraud (1957). In our country, the disease was first established by V. I. Tereskikh and R. 3. Kurbanov (1967), in calves - by G. I. Chervonsky (1959).
The disease is widespread in many countries, including Russia. In all regions of the country, chlamydia causes great economic damage to livestock, in addition, under certain conditions, poses a threat to human health.
The causative agent of the disease. Chlamydia causative agent Chlamydophila abortus has typical signs of chlamydia. It can be distinguished from the placenta, uterine secretions, parenchymal organs and abdominal contents of aborted fetuses. The pathogen multiplies actively in the yolk sac of 6 ... 7-day-old chicken embryos, causing their death on 4 ... 6th day after infection. Characteristic elementary bodies with a red color are detected in preparations from the yolk sac of dead chicken embryos stained by Stamp and Macciavelllo. Pathogenic for white mice and guinea pigs.
In the tap water, the pathogen retains its viability and virulence for 17 days, 18 in the snow, 29 in the snow, and 23 days in pasteurized milk. On pasture, in infected objects remains viable for several weeks, in livestock buildings - for 5 weeks. Boiling kills the microorganism within 2 ... 10 min.
Epizootology. The main source of the causative agent are patients and carriers from which chlamydia is excreted in various ways, especially during abortion and calving, with secretions from the birth canal, amniotic fluid, as well as feces, urine, milk, sperm, etc. Infection of healthy animals is possible also in many ways: alimentary, aerogenic, contact during sexual intercourse or artificial insemination with sperm from pedigree enterprises that are unfavorable for chlamydia. Cows inseminated with such sperm often develop infertility, fetal intrauterine infection occurs, which leads to abortion and stillbirth. In infected herds, the proportion of premature calving or the birth of weak calves with various pathological changes is quite high (up to 50%). The most common pneumoenteritis that occurs between the 15th and 40th day after calving.
There is a correlation between the presence of seropositive animals and clinical manifestations (abortion, infertility). It has been established that after an abortion, animals become immune to re-infection and, in the absence of changes in the genitals, are able to reproduce full-fledged offspring.
The percentage of abortions in dysfunctional herds, especially among heifers, can go up to 70 or more. Young animals from such animals become infected at birth. Chlamydia is stationary in nature, and the largest number of patients are recorded in winter and spring, which is explained by a closer contact of animals in the winter-stall period and mass calving of cows.
Pathogenesis. In infected adult animals, the infection occurs in a latent form and develops with the onset of pregnancy. At a certain stage of pregnancy, the pathogen is localized and multiplies in the placental tissue, causing placentitis and necrosis. These lesions, in turn, can cause an abortion. At the same time, at the moment of chla-midemia, the fetus is also infected. Chlamydia multiply in the parenchymatous organs of the fetus, cause swelling of the subcutaneous connective tissue and as a result of toxic action can cause its death. The development of inflammatory changes in the uterus, due to the action of chlamydia, or the death of the fetus leads to an abortion. Lymphogenous and hematogenous chlamydia enters the nearest lymph nodes and liver, multiplies in the spleen, lungs, bone marrow, genitals, in the walls of blood vessels, etc. Accordingly, pathological processes appear in these organs, leading to impairment of their function.
Current and clinical manifestation. In cattle, chlamydia is characterized by a wide range of clinical manifestations, which depend on the age, sex, physiological and immune state of the body, as well as on virulence and the received dose of chlamydia. Figure 3.1 shows the main clinical syndromes and signs of chlamydia in cattle.
In cows, the main clinical sign is abortion, which usually occurs on the 7th ... 9th month of pregnancy, but it is also possible on the 4th month. The disease begins suddenly, and the cows before the abortion show no clinical signs, with the exception of an increase in body temperature to 40.5 ° C. Sometimes progressive depletion of animals is noted. In aborted animals, more often in heifers, the separation of the afterbirth is delayed, metritis, vaginitis develop and finally infertility may occur.Chlamydial abortion often occurs on the background of bacterial or parasitic diseases (salmonellosis, brucellosis, vibriosis, streptococcosis, trichomoniasis, etc.). In these cases, the phenomena of a common se titsemii and death of adult animals.
Fig. 3.1. The main clinical syndromes and signs of chlamydia in cattle
Depending on the route of infection and age, the main signs of chlamydia in young cattle are gastroentero-colitis, polyarthritis, bronchopneumonia, keratoconjunctivitis, encephalomyelitis. These signs appear at one time. Newborns have diarrhea, fluid stool mixed with mucus and blood. There is a dehydration of the body, eyes sink, calves are strongly depressed, refuse to feed. The body temperature rises to 41.5 ° C, leukocytosis and neutrophilia are detected in the blood.
In calves W ... 10 days of age, except for diarrhea, polyarthritis is observed. Often affects the carpal and tarsus joints, they are swollen, painful. Patients with calves develop fever, conjunctivitis, weakness, short-term diarrhea, they lose weight quickly and die 2-10 days after the first signs of the disease.
Chlamydia in the form of keratoconjunctivitis acquires the character of enzootic among young cattle of different age groups (see section "Infectious keratoconjunctivitis").
Some calves from 20 ... 30 days to 5 ... 6 months of age are more pronounced signs of damage to the respiratory system. At the beginning, there is a decrease in appetite, body temperature rises to 40.5 "C. Discharge from the nasal cavity appears, on 3 ... 5th day - cough, wheezing in the lungs. Often the disease is complicated by secondary autoinfection, sometimes occurs in association with adenoviruses , parainfluenza-3 pathogens.
In bulls, chlamydia is characterized by orchitis, balanoposthitis, urethritis. In sick bulls, the testes are slightly enlarged, painful, sedentary. Animals are worried when urinating, shifting from foot to foot, a thick exudate is released from the prepuce.
In one-year-old bulls, the disease proceeds with little or no pronounced clinical signs, but sperm quality deteriorates significantly (decrease in sperm concentration and motility, aspermia, necro-sperm). In smears of sperm from sick bulls, a large number of cellular elements with a predominance of neutrophils are detected.
Pathological signs. Marked macroscopic changes in the genitals of cows with chlamydia cannot be considered as specific. The intensity of pathological changes in aborted fetuses and placentas of cows depends primarily on the duration of pregnancy.
Fruits of cows aborted before 6 months of age do not have pronounced lesions. Only an increased amount of reddish fluid in the pleural and abdominal cavities is noted, as well as subcutaneous reddish edema. When examining the fruits of cows aborted on the 7th ... 9th month of pregnancy, a number of pathological changes of diagnostic value can be detected. This is the pallor of mucous membranes, puffiness of the skin and subcutaneous tissue, especially in the head, very often hemorrhages are visible on the skin, on the mucous membrane of the mouth and tongue. Lymph nodes in the fetus are enlarged and swollen.
The liver is enlarged, granular, loose consistency, from light yellow to red-orange color. Specific foci of inflammation of 5 x 10 mm in the myocardium and in the cortical layer of the kidneys are also specific. In placenta, changes are detected, the severity of which also depends on the duration of pregnancy and the duration of infection at the time of abortion. At necropsy of calves, signs of catarrhal gastroenterocolitis are noted, the rennet mucosa is swollen, dotted with multiple hemorrhages, pericarditis, pleurisy, and pneumonia are observed. In the liver dystrophic, necrotic changes of the parenchyma are clearly visible. The joints contain greyish-yellow fluid, the articular capsule is littered with hemorrhages, sometimes necrosis of cartilage and its detachment from bone tissue are possible. In bulls in the parenchyma of the testes, multiple necrotic foci are visible. Fibrinous periorchitis, chronic balano-postitis, and urethritis are also characteristic of chlamy-diosis.
Diagnostics and differential diagnostics. The diagnosis of chlamydia is established comprehensively, taking into account the epidemiological data, clinical signs, post-mortem changes and laboratory data. The presence of permanently dysfunctional farms for enzootic abortions in cows, changes in the placenta and fetuses, as well as the identification of elementary bodies and inclusion bodies in the tissue-imprinted tissue smears of the affected areas of the placenta, make it possible to make a preliminary diagnosis.
To clarify the diagnosis in the veterinary laboratory send:
blood serum from aborted or suspicious animals for the disease, taken twice: during the clinical manifestation of the disease and again after 14 ... 21 days;
pathological material from dead or dead animals (pieces of the placenta, lymph nodes, parenchymal organs and testicles, aborted whole fruits or parenchymatous organs, fetus rennet);
Ejaculate or frozen semen samples obtained from manufacturers suspected of being ill.
Laboratory studies carried out according to the current guidelines for laboratory diagnosis of chlamydial infections in animals. They include: 1) the detection of specific antibodies in the serum of patients in RAC, RNA, ELISA; 2) detection of chlamydia and their antigens in the pathological material by the method of light or luminescent microscopy; 3) isolation of chlamydia in chicken embryos, in cell culture or laboratory animals, followed by their identification.
For biological samples, white mice or pregnant guinea pigs are used. If there is pathogenic chlamydia in the material, the animals become sick and die. Elementary bodies are found in organs, the placenta, aborted fetuses and peritoneal exudate.
In the differential diagnosis of chlamydial abortions of cows, abortions observed in other infectious and non-infectious diseases (brucellosis, leptospirosis, campylobacteriosis, trichomoniasis, etc.) should be excluded.
Chlamydial bronchopneumonia of young cattle must be differentiated from viral respiratory diseases (infectious rhinotracheitis, pustular vulvovaginitis, parainfluenza-3, viral diarrhea, adenovirus infection), as well as mycoplasma, pasteurellosis.
Immunity, specific prevention. Chlamydia in the body of infected animals induce both humoral and cellular immunity. Immunity is non-sterile. When chlamydia over immunoprotective immune reactions dominate immunopathological with the formation of circulating immune complexes.
However, antibodies in chlamydia are not able to prevent the disease, but they play an important role in providing resistance to infection with small doses of chlamydia, which is usually found in the natural infection of animals.
Specific prevention of chlamydia in cattle has been developed in many countries, including Russia. Vaccination is a mandatory event for the improvement of farms from this disease. For specific prophylaxis to cattle, emulsin vaccine against chlamydia of animals is used culturally inactivated animals. Immunity in vaccinated animals persists for 1 year after vaccinations.
Prevention. Measures for the prevention and elimination of chlamydia are carried out according to the current rules. In order to prevent disease, you must:
the acquisition of farms to conduct clinically healthy animals from farms with chlamydia-free farms;
not to allow sharing of animals of different species, as well as to limit their contact with domestic and wild birds;
create an optimal indoor climate, comply with the principle “everything is free - everything is busy”;
Bulls in all categories of farms, 2 times a year (in spring and autumn) should be examined serologically for chlamydia.
Treatment. Treatment of sick animals should be complex and includes etiotropic, symptomatic and measures aimed at preventing possible complications with endogenous microflora. As etiotropic therapy for chlamydia, tetracycline antibiotics are mainly used, to which the pathogen has a high sensitivity (tetracycline, biomycin, oxytetracycline, etc.). Sulfonamide drugs on chlamydia do not work. In patients with chlamydia of cows, in which the afterbirth and inflammatory processes in the genitals are noted, general treatment is combined with topical treatment.
Tetracycline antibiotics are subjected to calves that have a fever, swollen joints, cough and eye damage. For the treatment of calves with chlamydial bronchopneumonia, the most effective use of drugs in the form of aerosols in special chambers.
Treatment of patients with manufacturing bulls is carried out by giving inside tetracycline hydrochloride or oxytetracycline for 10 days. 2 months after the course of therapy, the bulls determine the presence of antibodies in the serum and the quality of sperm. Repeated positive serological reaction and the presence of chlamydia in sperm smears are grounds for culling this animal.
Control measures. When the disease is established, the farm on which chlamydia is diagnosed is declared unsuccessful and restrictions are imposed.
In state-owned enterprises, where in recent years there have been cases of the disease of bulls with chlamydia, a microscopic (RIF) study of the ejaculate is carried out in parallel with a serological study in order to detect chlamydia and to study the cellular composition. Animals that have specific antibodies detected in the blood and chlamydia in the ejaculate are sent to slaughter, the sperm harvested from them is destroyed.
Animal houses are subjected to mechanical cleaning and disinfection. Aborted fruits, membranes, corpses are collected in a watertight container and taken out for disposal. Manure, bedding is stored in a pile and disinfected biothermally.
For disinfection of livestock buildings, free-flowing areas, pens use 4% sodium hydroxide solution, 4% chloramine solution, 3% phenosmolin solution at exposure 3 ... 4 h, bleach solution containing 3% active chlorine.
Forced slaughter of animals is carried out at the sanitary slaughterhouse. The carcass and unmodified organs are released after boiling, the modified organs are sent for recycling.
Carcasses and other products obtained from the slaughter of animals, which only positively react in the study of chlamydia in the absence of clinical signs or pathological changes in the muscle tissue and organs, are sent for industrial processing. Skins obtained from the slaughter of animals, clinically sick with chlamydia, are released after disinfection.
Milk from seronegative animals is used without restrictions, from abortive and seropositive cows - to be boiled for 30 minutes and can be used on the farm only for feeding animals.
Restrictions on the unfavorable item are removed 30 days after the recovery of sick animals and the holding of final measures.
Human health measures. Persons caring for sick animals or busy cutting the carcasses of such animals, as well as conducting research on pathological material from patients and those suspected of having chlamydia, should strictly adhere to personal prevention measures.
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