The rearing of mulberry silkworms for the production of natural silk is of great economic importance. The efficiency of sericulture primarily depends on the health of the silkworms. Various diseases can lead to delayed development, reduced productivity, decreased cocoon weight, deterioration of silk quality, and even significant mortality among silkworms.
Some diseases of the mulberry silkworm can be identified based on external symptoms. However, laboratory investigations, including microscopic examination, are of great importance for accurate diagnosis and identification of the causative agent. Using a microscope, parasite spores, bacteria, and characteristic fungal structures can be observed.
Mulberry silkworm diseases are conventionally divided into infectious and non-infectious diseases. The main infectious diseases include pebrine (nosematosis), flacherie, muscardine, and a number of bacterial diseases.
Pebrine, or nosematosis, is considered one of the most dangerous diseases of the mulberry silkworm. Its principal causative agent is the parasitic microorganism Nosema bombycis.
In infected silkworms, delayed development, reduced appetite, changes in body coloration, and uneven development among individuals may be observed. In severe cases, silkworms die before reaching the stage of cocoon spinning.
Microscopic diagnosis is particularly important for detecting pebrine. A sample is collected from a diseased silkworm or appropriate biological material, prepared using laboratory methods, and examined under a microscope.
In infected material, Nosema spores appear as small oval or ellipsoidal bodies.
Pebrine is particularly dangerous because the infection can be transmitted through eggs to the next generation. Therefore, microscopic monitoring of parent silkworms, eggs, and other breeding materials is of great importance in preventing the spread of the disease.
Flacherie is an infectious disease of the mulberry silkworm and is more likely to spread under unfavorable rearing and housing conditions. Inadequate temperature, excessive humidity, poor-quality feed, insufficient nutritional value of mulberry leaves, and failure to comply with sanitary requirements may contribute to the emergence and spread of the disease.
Silkworms affected by flacherie usually become lethargic, with reduced appetite and motor activity. At later stages, the body of the silkworm becomes soft and limp and may develop an abnormal coloration.
Microscopic examination of affected material may reveal certain forms of microorganisms, including bacteria. However, it is not always possible to identify the specific causative agent of flacherie solely on the basis of microscopic findings. Therefore, additional laboratory methods are required for definitive diagnosis.
Muscardine is a fungal disease of the mulberry silkworm. One of its most common causative agents is the fungus Beauveria bassiana.
After death, infected silkworms gradually become hardened, and a whitish fungal growth appears on the surface of their bodies. For this reason, muscardine is sometimes referred to as the “white disease.”
Microscopic examination of affected material reveals characteristic fungal structures, including hyphae and spores. These features are diagnostically important for determining the fungal nature of the disease.
The mulberry silkworm can also be affected by various bacterial diseases. Bacteria may enter the silkworm's body through contaminated feed, injuries, or unsanitary rearing conditions.
The symptoms of bacterial diseases vary depending on the species of pathogen and the severity of infection. Diseased silkworms may exhibit lethargy, reduced appetite, changes in body condition, and, in severe cases, death.
For the diagnosis of bacterial diseases, affected material is examined under laboratory conditions. A microscope can be used to observe the presence of bacterial cells; however, microscopy alone is insufficient to determine the specific bacterial species and its precise characteristics.
In such cases, additional diagnostic methods are required, including microbiological culture and other laboratory investigations.
The microscope is one of the important tools for the laboratory diagnosis of mulberry silkworm diseases. It enables the study of microorganisms and microscopic structures that cannot be seen with the naked eye.
Depending on the type of disease, microscopic examination may reveal parasite spores, bacterial cells, fungal hyphae, and spores. For example, Nosema spores can be observed in the diagnosis of pebrine, fungal structures in muscardine, and bacterial cells in certain bacterial diseases.
Despite the importance of microscopy, examination results should be correlated with clinical signs and other laboratory data. When necessary, additional diagnostic methods are used to identify the specific causative agent.
Pebrine, flacherie, muscardine, and bacterial diseases are among the most important diseases affecting the mulberry silkworm.
Early detection of disease is essential for preventing the spread of infection and reducing silkworm losses. Microscopic examination plays an important role in diagnosing a number of mulberry silkworm diseases, particularly pebrine and fungal diseases.
At the same time, microscopy alone is insufficient for the accurate diagnosis of certain diseases; therefore, additional laboratory investigations are necessary.
Thus, compliance with sanitary requirements, the use of healthy breeding material, regular monitoring of silkworm health, and timely laboratory diagnosis are of great importance for disease prevention, maintaining silkworm health, and improving the efficiency of sericulture.
