Sarcocystosis

Pathogens.

Sarcocystis bovicanis - oocysts with sizes 12-17 x 11-14 microns, with a thin single-layer membrane. Sporulation takes place in the definitive host, with the shell tightly compressed around the sporocysts and forms a dumbbell-like oocysts. The size of the sporocysts 11-14 x 7-9 microns. The number of meronth generations is unknown. The latest-generation meronts (sarcocists) are localized in the muscles of the esophagus, diaphragm, and skeletal muscles of cattle. On the 120th day after infection, the formation of the sarcocysts of the spindle shaped, oval, bag-shaped forms, up to 3 mm long, filled with merozoites 13-17 µm long and 2.53 µm wide, often banana-shaped. Gametogony passes under the epithelium of the small intestine. The preparation period lasts 7-9 days, the patent - 6-7 days.

Sarcocystis bovifelis - unsporulated oocysts rounded, sporulated - dumbbell-shaped. Sporocysts are elliptical, colorless or pale yellow, 13-22 x 6-5 microns in size. Three generations of meronthas develop in the body of cattle. First generation bullets are localized in the endothelial cells of the large intestine arteries, in the kidneys, pancreas and brain, the second in the endothelial cells of the capillaries of many organs, especially the kidneys, and the third in the striated muscles. The length of the sarkotsitsist can reach 1 cm. 3 months after infection, the sarcocysts complete development and can cause infection in dogs. The preparative period lasts 8-33 days, the patent - 8-70 days or more.

Sarcocystis bovihominis - sporocysts 13-17 x 8-11 microns in size, contain residual bodies. 476 suggest that the early stages of meronths develop in various internal organs. Sarcocysts have a cylindrical shape with fingerlike outgrowths. They form rounded metrocytes, which turn into gamont. The human drug period is 9-10 days.

Sarcocystis ovifelis - oocysts with sizes of 15-18 x 10-14 microns, rarely excreted into the external environment. Released sporocysts 11-14 x 8-9 microns in size contain residual bodies. Each sporocyste contains 4 sausage sporozoites. Sarcocysts are localized in the muscles and can reach a length of 1 cm. Merogony takes place in the small intestine of cats. The preparation period lasts 11-14 days, the patent - up to 2 months.

Sarcocystis ovicanis - sporulated unsporulated oocysts, sporulated - dumbbell-shaped. Sporocysts oval, sizes 13-16 x 8-11 microns, pale yellow or colorless. Banana-shaped sporozoites, 11 x 2-3 microns in size. Sporulation takes place in the small intestine of dogs. Sporulated oocysts are found in the intestines on days 7–10 after infection of dogs with sarcocysts from sheep. Merogony takes place in the endothelial cells of the arteries of many sheep organs. Sarcocysts form in the muscles by the end of the third month after infection with dog sporocysts. Gametogony takes place in the small intestine of dogs one day after infection with sarcocysts from sheep. The preparation period lasts 8-14 days, the patent - more than 9 days. Thus, the development of pathogens sarcocystosis, as well as ameri, has three phases: sporogony, merogony and gametogony. Merogony takes place in the body intermediate, and gametogony and sporogony - in the body of the definitive host. The development of each phase is necessarily confined to a specific organ of both the definitive and intermediate host.

Development Biology.

Sarcocysts develop with the participation of two hosts - definitive and intermediate. The definitive hosts of cattle pathogens in sarcocystosis in cattle are cats, dogs and humans. In small cattle - only dogs and cats. Intermediate owners - large and small cattle. The definitive hosts, in the organism of which the sexual cycle of development occurs, are excreted into the external environment with feces or sporulated oocysts containing two spores with four sporozoites in each, or sporocysts derived from oocysts. Intermediate hosts become infected by ingestion of oocysts or sporocysts with feed or water. In their gastrointestinal canal, released sporozoites penetrate into the bloodstream and into the endothelial cells of the vessels of the internal organs. They multiply by schizogony (multiple division).

The last generation merozoites enter the muscles where they form cysts. They are filled with a large number of merozoites and can be large - up to 2 cm in length (macrocyst) and microscopic (microcyst). Macrocyst are clearly visible to the naked eye in the form of yellowish-white nodules. When eating definitive hosts (dogs, cats and humans) of meat affected by sarcocysts and not having undergone the necessary processing, cystic stages occur in the digestive tract and sexual reproduction begins in the intestinal epithelium with the formation of oocysts.

Epizootological data.

Sarcocystosis of large and small cattle 478 is widespread. The extent of damage to animals in farms, where cats and dogs have free access to farms and pastures, reaches 100%. Sheep are particularly affected. This is due to the high degree (up to 90%) of dog cysts invasion, the parasite's great reproductive ability, its considerable stability in the external environment and muscle tissue. The main sources of infection are dogs, cats, people. Do not underestimate the spread of invasions and the role of other animals: wolves, foxes, raccoons, jackals, etc.

Pathogenesis and immunity.

In definitive hosts, the pathogenic effect on the body consists of the resulting endogenous stages of the parasite and disorders of the gastrointestinal canal, resulting in disorders of the integrity of the intestinal mucosa resulting from inflammatory processes. In cattle during the development of endogenous stages, acute inflammatory processes of organs and tissues occur as a response of the organism to the introduction of the pathogen. The defeat of the endothelium of blood vessels leads to the accumulation of toxic substances, dystrophic changes in parenchymal organs. It is believed that sarcocysts are the most virulent during the period of merogony. The manifestation of virulence is associated with the release of a parasite toxin - sarcocysteine, which disrupts the normal course of biochemical processes in cells. Due to the increased porosity of the vessels and extensive mass hemorrhages, anemia develops, and the heart and lungs become more frequent, causing acute heart failure. The development of merontov in the endothelium of the kidneys, liver, intestine leads to a violation of their functional activity. Developing cysts contribute to the atrophy of the surrounding muscle tissue. In places of a rupture of cysts the centers of a necrosis can be formed. An organism afflicted with sarcocysts fights invasion by mobilizing defense mechanisms, including the formation of antibodies. Sarcocysts sensitize the body of a sick animal, stimulating allergic reactions. The body is in a state of allergy to antigens. It is believed that definitive hosts can be repeatedly infected with sarcocysts of the same species. Cattle and small cattle accumulate invasion with age as a result of repeated re-infections.

Symptoms of the disease.

They depend on many factors and above all on the number of oocysts and sporocysts that caused the disease about the intermediary host, the pathogenicity of the pathogen, the immune status of the animal, the conditions of detention and feeding, etc. Most often the disease is chronic. In animals, the general condition worsens, body temperature rises to 40.5 ° C and higher, appetite disappears and productivity decreases, there may be erosion on the tongue and cheek mucosa. Pregnant and sugynye animals. Intensive damage to the heart muscle by sarcocysts can cause arrhythmia. The development of cysts in the striated musculature causes the occurrence of myositis, which is manifested by pain on palpation and shaky gait. A long (up to 2 months) course of the disease leads to anemia, tissue swelling in the submandibular space, severe depletion and death. In experimentally infected calves, a double rise in temperature is observed, which coincides with the development of meronths of the first and second generations of the sarcocist. Then comes depression, weakness, emaciation, fever, tachycardia, shortness of breath, shortness of breath, gnashing of teeth, muscle twitching, unsteadiness of gait, diarrhea, increased thirst. Similar clinical signs were observed in experimentally infected lambs. In definitive hosts (dogs, cats, arctic foxes), clinical signs when they are fed raw meat that is intensely infected by sarcocysts are not usually noted.

Pathological changes.

In cattle and small cattle, pathoanatomical changes are characterized by exhaustion, anemia of the mucous membranes, dullness of hair. On the serous membranes and in the parenchyma of all internal organs, massive hemorrhages are observed. All lymph nodes are enlarged. In the thoracic and abdominal cavities find a small amount of transparent, yellow exudate. Infiltration and swelling of the heart, brain, kidneys, muscles with foci of inflammation, necrosis and calcification are possible. Erosion and ulceration can be seen on the lips, gums, tongue, soft palate, esophagus, abomasum and all along the intestines, in the middle arteries of the lungs and the spleen - blood clots.

Diagnostics.

A complex diagnosis of sarcocystosis is made by analyzing the epizootological and clinical data, the picture of the autopsy, and confirmed by laboratory data. In definitive hosts, dogs and cats, diagnosis can only be made by examining feces using Darling and Fülleborn methods. With positive results, sporulated oocysts or sporocysts of pathogens are found. Given that the disease is widespread and in its course, both in large and small ruminants, there are no signs typical only for it, it is very difficult to diagnose clinically. At necropsy or a veterinary-sanitary examination of sheep and cattle carcasses, macrocysts as large as rice grain or white pea are found in the wall of the cervical part of the esophagus. Cysts can also be found in the muscles of the tongue, heart, diaphragm and skeletal muscles. To make sure that these formations are sarcocysts, they are placed on a glass slide, destroyed using dissecting needles or a scalpel. The contents of the cysts are mixed with a drop of water, and a small amount of the mixture is examined under a microscope with an average magnification in a slightly darkened field. In sarcocystosis, bananoid-shaped merozoites are visible in the contents. For greater persuasiveness, you can make a smear and paint it according to Romanovsky. In a smear you can see in the field of view a lot of merozoites. For the detection of a microcyst, samples are taken of the muscles of the heart, esophagus, diaphragm, skeletal muscles as large as oat grain, four slices are placed between the compressor glasses, squeezed and examined under a small microscope magnification. Microcysts have a spindle or oval shape and are located between the muscle fibers. A rather simple method for detecting merozoites from a microcist was proposed by M. Kozar. To 2-5 g of the investigated muscles add 2 to 5 ml of saline and triturate in a mortar to obtain a homogeneous mass. For the study, a drop of this liquid is taken, examined under a microscope with an average magnification, and merozoites are detected. For in vivo diagnosis using allergic and serological methods. As an allergen, a drug from cystozoites is used. Allergen is injected intracutaneously in the upper eyelid area. With a positive reaction after 2-4 hours, a swelling with a diameter of 10-20 mm or more is formed. Serological diagnosis is carried out by setting the RA, RSK and RDSK. The sarcocytosis antigen extracted from cystozoites with specific substances is used. Sarcocystosis of large and small cattle should be differentiated from a number of invasive and infectious diseases, such as toxoplasmosis, cysticercosis, pasteurellosis, brucellosis. When differentiating oocysts, the sarcocysts from oocysts of other exciters (Ameri and Toxoplasma) take into account their morphology and biological features of the life cycle, the place of oocyst sporogony, host specificity.

Treatment.

When treating cattle sarcocistosis, amprolium is used at a dose of 100 mg / kg. Halofuginone (stenerol) is administered to small cattle at a dose of 0.66 mg / kg. The drug is toxic and requires accurate dosage. For the treatment of dogs, chemcoccides are used at a dose of 50 mg / kg, as well as a coat of roe for a dose of 200 mg / kg.

Prevention and control measures.

All actions should be aimed at breaking the biological chain of pathogen transmission from the definitive host to the intermediate and vice versa. It should be remembered that man is also the definitive owner. It is categorically forbidden to feed meat and dogs affected by sarcocysts to dogs and cats. All animal corpses must be subjected to technical disposal or burial to a sufficient depth. In the territories of farms, in places of storage of feed can not keep dogs and cats. It is necessary to organize catching of homeless animals, systematically carry out deratization of farms and storage facilities. Bathrooms should be equipped on all farms. Feeding and keeping animals must meet veterinary and zootechnical requirements. An important link in the prevention of sarcocistosis is sanitary and educational work not only among the attendants, but also of the entire population about the ways of infection with the causative agent of sarcocystosis in animals and humans.

Human sarkosporidiozy often asymptomatic and difficult to diagnose, a person can play the role of both the main and intermediate host sarcocysts.

Intestinal sarkosporidiosis occurs when a person acts as the main host and is caused by the species S. hominis , S. suihominis and S. bovihominis . Infection occurs when eating insufficiently processed (half-baked) meat (pork, beef) containing sarcocysts, the flow is usually asymptomatic, in some cases accompanied by dyspeptic symptoms, fever, chills. Excretion of sporocysts with feces begins on the 10th - 13th day after infection and can last up to six months. Intestinal sarkosporidiosis is quite widespread.

Muscular sarkosporidiosis occurs when infected with sporocysts, when a person acts as an intermediate host and is caused by S. lindemanni , the infection occurs with sporozoites, which, when penetrating skeletal muscles and myocardium, form cysts, which can subsequently be monitored. In some cases, accompanied by myalgia and general malaise, is extremely rare.