Ligulosis of fish, the species of which we will describe in this article, is a fairly common disease in living organisms living in freshwater bodies of water. Infection occurs due to tape parasites in the larval stage. If they enter the body of the fish in a state of embryo, then the animals become infected. It should be noted that such larvae are capable of infecting all fish belonging to the cyprinid family. This type of parasite is found in many rivers, lakes, estuaries, ponds and reservoirs.
Pathogens
One of the causative agents of fish ligulosis, the photo of which is presented in the article, is plerocercoid. These helminths are white or yellow. They reach a length of 5 to 120 cm. In width, they do not exceed more than 2 cm. In the host organism, they attach to the tissues due to slit-like botria. Sexual complexes are located along the body of the parasite. The uterus of this worm looks like a tortuous tube. The laid eggs got an oval shape, no embryos.
Development cycle
Before considering the fish disease described in the article - ligulosis, it is necessary to understand the mechanism of development of the pathogen.
- To begin with, the egg enters the water - stage 1. This happens as a result of the process of defecation of fish-eating birds, gulls, grebes and so on. Together with excrement, they fall into the water. How quickly the embryo forms depends entirely on the temperature regime. If the indicator exceeds 20 degrees, then the eggs develop in a week. In the event that it ranges from 15 to 20, this period is extended to 10 days, and up to 15 days if the temperature is not more than 12 degrees.
- The second stage is that after a certain amount of time an embryo appears. The larva leaves the egg and then moves through the water. In a viable state is not more than 3 days. The period may vary slightly depending on the temperature of the water.
- The third stage is that the embryo enters the body of the crustaceans. They can also parasitize in cyclops and other similar animals. These hosts are the first intermediate, where the oncosphere is formed. After 2 weeks, it turns into a more mature individual.
- The fourth stage is that infected crustaceans enter the body of the fish. From the intestines, they crawl into the abdominal cavity of a larger carrier. Able to develop for up to a year. During this time, they grow to adults. Parasitize in the body of fish up to 3 years.
- The fifth stage is the last. The final "owners" of these parasites are birds that feed on fish. Further, in the intestines of feathered individuals grow to mature worms. Therefore, they begin to produce eggs. Their selection lasts no more than 4 days. After - helminths die and already with feces and eggs get out. The cycle repeats again.
Risk of disease
Ligulosis of fish can occur in a large number of representatives of the aquatic fauna. We are talking about a bream, roach, barbel, crucian carp, ram and so on. Over the past few years, it has been revealed that at risk are grass carp, as well as silver carp. Most often, carp and carp are affected. In some species of silver carp, two types of helminths can parasitize at the same time. Representatives living in estuaries, reservoirs and lakes are usually sick. In rivers and ponds, such cases are rare. This is explained by the fact that fish-eating birds fly to such reservoirs less often. In summer, winged nests on the waters, where they are constantly looking for food.
Infection occurs in the coastal zone, where mainly all fish feed only on zooplankton. It should be noted that when catching product representatives, the prevalence of infected people ranges from 40 to 60 percent. Moreover, the intensity is quite high: about 2-4 helminths per individual. Detailed characteristics are found in fish aged 2 to 4 years.
Representatives of the older generations have much less such indicators. Fish such as minnows and minnow, in almost 100% of cases suffer from fish ligulosis. Infection usually occurs in spring and summer. This period is the most favorable for the development of parasites. At the same time, a large number of fish die. Catching in the spring, which falls on April-May, is characterized by the maximum number of sick individuals. In the summer and autumn, they are much smaller.
In pond farms, fish is healthy. This is due to the fact that birds are least likely to visit such places. In the industrial sphere, measures are often taken that make it possible to deter winged, loving to feast on fish.
Danger to humans
It is also necessary to note the danger of fish ligulosis to human health. Many people may be disgusted at catching infected representatives. However, such fish are not dangerous. If there is a desire to use the catch as food, it is necessary to remove the helminthic infestations along with the gills. With proper processing of fish, ligulosis is not dangerous for humans.
Symptoms of infection
When fishing, you need to pay attention to certain nuances. As a rule, infected individuals stay in the upper layer of water. They swim on their side or abdomen up, while remaining alive. They are very easy to catch. If strong waves appear, then such animals do not go into the depths of the reservoir, but, on the contrary, are nailed to reeds. In places where there is a huge concentration of sick fish, there are always bird colonies. They catch them. The fish looks very exhausted. On examination, you may notice a bloated abdomen, especially in the front. It will be quite hard due to the fact that helminths accumulate in it. Sometimes they can very strongly press on the abdomen of the fish. Accordingly, it is capable of breaking.
The effects of parasites on the body
The science of parasitology of fish ligulosis has been well studied, so you can roughly understand the mechanism of the development of the disease. It differs in that helminths after infection begin to grow and compress all internal organs. Because of this, the performance of all functions is disrupted and metabolic processes are inhibited. Fish will eat poorly, internal organs are underdeveloped or atrophied. Such a representative of the fauna is greatly depleted, and also have a weight of 2-3 times less when compared with healthy individuals.
Such a fish becomes barren, as the sex glands atrophy. Such a disease greatly affects the reproduction of the entire reservoir. The presence of such parasites in the body leads to intoxication in the fish. As a result, hemoglobin decreases, the number of neutrophils increases, and so on.
Pond Prevention
At present, there are no methods for treating fish ligulosis as such; therefore, certain preventive measures must be taken. You should study the characteristics of the parasite, as well as the patterns of the disease.
In pond farms, prevention comes down more to scaring away birds. It is necessary to ensure that there is no nesting near them. If a disease is found in the pond, it is necessary to catch and destroy all the fish, and drain the water. Helminth will be removed together with representatives of the local fauna. And water should be eliminated in order to avoid re-infection. To completely destroy the crustaceans, which can also be infected, in the winter, the pond must be kept without water. All pits, channels and wet places should be disinfected. This is done using quicklime. About 25 centners per hectare are used. In spring, pond lodges should be listened to and plowed.
Prevention in large bodies of water
If we talk about prevention in larger bodies of water, lakes and reservoirs, it should be noted - this is a rather difficult task. You can perform a number of measures that at least will minimize the percentage of infection.
It is necessary to scare away fish. This is done with blank shots. So you can get rid of the colonies. To prevent winged nests, hard aquatic vegetation should be completely destroyed. All infected fish must be caught from the places where it accumulates.
It should be studied among which fish ligulosis is most common. It is better to populate the reservoir with those representatives who are not amenable to the effects of these helminths.
Expertise
Any fish that has been caught from a dysfunctional reservoir must be inspected and sorted. This is done both fresh and chilled. If representatives with signs of swelling come across, then they are immediately eliminated. Such fish can be used in gutted form in the field of public catering, or processed for canned food. If it has a poor presentation and signs of severe exhaustion are detected, then it will be disposed of immediately. In the case when there are no clinical symptoms of damage to the fish by ligulosis, such a representative of the fauna is sent for sale without any restrictions.
How to protect yourself?
In order to protect yourself from ligulosis, it is necessary to heat-treat it before ingestion of infected fish. This precaution is considered basic.
Low-cooked, raw or unprocessed fish is forbidden to eat. Otherwise, the parasite can enter the human body. During thermal treatment, in order to completely eliminate ligulosis in fish, a temperature of at least 50 degrees must be maintained. Such a measure will prevent the development of helminths.
To get rid of the parasite larvae, you need to freeze the fish. At home, you can use a simple freezer. However, there should be a fish with ligulosis there for at least 10 hours. Ideally, it is best to keep her in it for about a day.
To carry out the disinfection method, it is necessary that the temperature in the freezer be at least -20 degrees. If it does not reach such a mark, but fluctuates around -10, then it is best to keep the fish in the freezer for up to 4 weeks.