Plague crayfish

The appearance of this epidemic in Europe dates back to the years 1860–1865, when, apparently, the mass extinction of cancers in Lombardy was first recorded. Then, at the end of the sixties, the plague spread in the waters of Belgium and France, and in 1878–80, crayfish almost completely became extinct in the waters of Baden, Württemberg and Bavaria up to Upper Austria. At about the same time, the extinction of the crayfish was recorded in Central and Northern Germany, in Mecklenburg and Saxony; in 1881–1883, the gastronomically famous Oder cancer disappeared. In 1884, the crustacean plague crossed the Vistula River and in 1892 it spread alongside Russia - in Masuria . In its forward procession from west to east, this epidemic stopped for a while near the eastern border of Germany, but in different parts of it, such as, for example, in Mecklenburg, Brandenburg and West Prussia, was observed sporadically in later years (1896). In Russia, the crustacean plague appears, apparently, in 1892, which coincides with the year when this epidemic spread in the waters of neighboring Mazuria. According to individual instructions, the crayfish was seen within Russia much earlier (in 1878) in the mouths of the Danube and in some of its lower tributaries, but, apparently, in the latter case, the extinction of the crayfish was due to other causes and, by the way, pollution water mine runoff from neighboring mines. The overwhelming number of correspondents requested on this occasion point to 1892 — as the year when the crustacean plague first appeared in Russia and, by coincidence, almost everyone tends to coincide with the 1892 cholera epidemic. A very strange fact is that in Russia the crayfish plague was somehow immediately scattered within one year (1892–1893) in such distant from each other areas as Privislyansky, Dniprovsky, Volzhsky and Severo-Ozerny, while in Western Europe this epidemic spread with considerable gradualness. In addition, it is somewhat unexplained why this epidemic has found such favorable soil in Russia, where, compared with Western Europe, water pollution from industrial waste, causing the emergence of foci of all sorts, including pathogenic bacteria, can be considered as yet insignificant. According to information collected by the Department of Agriculture and the Imperial Russian Society of Fisheries and Fisheries (up to 702 correspondences), the crustacean plague was registered more or less reliably - in 1892 - for the Bessarabian province (the mouth of the Danube) and for the Volga region ( Samara province ); in 1893-1894 - for the Dnieper region, where it, starting from the estuaries and lower reaches of the Dnieper, moved gradually upstream - in the same 1893 - for the lakeside region (the river Svir , Onega, Ladoga and other lakes); in 1896 - for the basins of the Don and Western Dvina rivers . In the basin of the Dnieper, and in many other places, crayfish sometimes died at once in such large numbers that they contaminated the air with a terrible stench and had to be buried in the ground. Sometimes the plagued crayfish crawled in huge numbers to the shore and died on land in heaps. Unfortunately, there is no information about the basin of the Vistula River, and yet this border basin is particularly interesting in clarifying whether the crustaceans have passed to us from the west (from Germany), or, for the first time, penetrated through the Danube and the Dnieper . In general, it is extremely difficult to trace the spread of the rachea epidemic because of some contradictions in the correspondences reported from different parts of Russia. In 1900-1901, the crustacean plague, which devastated most of the reservoirs of European Russia, began to subside and in some places crayfish began to appear again in the reservoirs devastated by it. Judging by numerous reports, in the western and southwestern provinces, where the crayfish industry has developed quite extensively over the past decade, traders themselves played an important role in spreading the crustacean plague, and, through their agents-buyers everywhere, distributed special traps for crayfish ("buchi"), brought by them from abroad after using them there in knowingly plagued reservoirs. In any case, this or a similar way should have occurred in many places the infection of completely isolated reservoirs and the transfer of contagion through very long distances. For example, there is a known case of direct infection from the Podolsk province into the Oka River basin, along with the transport of sick crayfish. Even more remarkable is the fact of penetration of the crayfish plague even into the reservoirs of Western Siberia ( Tobolsk Province ), that is, through the Ural Range . With a high degree of likelihood, it can be assumed that crayfish traders contributed a lot to the extremely widespread spread of crayfish, which was observed in Russia, where only a few central provinces were more or less spared by the epidemic, while in all other crab fishing, which is still quite important auxiliary fishing for the population, due to the plague, was greatly reduced, and in some places stopped altogether ^[1] . In 2001 and in 2006, the plague was recorded in the Moscow region of the Shatura reservoirs and throughout the region.

Infection occurs through zoospores of the fungus Aphanomyces astaci from the family Oomycetes , which with the help of two flagella move from the carrier to the host. When a zoospore is infected with a new host, it discards both flagella, forms a cyst on the host, and attempts to penetrate the outer layer of the skin. The life span of zoospores is approximately 5 days without a host, and the process of discarding flagella can be resumed up to 3 times.

American crayfish are resistant to plague and are its main carriers. Their own enzymes prevent the spread of the disease. With moulting cancer, the fungus enters the water and starts producing spores.

Symptoms

After infection in crayfish, the defense reflex disappears. Cancer is scratching the eyes, belly and limbs with claws. His daily activity increases and symptoms of paralysis appear. The extremities disappear, the cancer is tilted on its side and in this position it is salted.

The disease is incurable and is fatal for cancers.