Biochemical and histopathological insights into different helminth infections in Saurida undosquamis with new host record of Ligula intestinalis.

Background

Saurida undosquamis (brushtooth lizardfish) is a species of the Synodontidae family that is widely distributed and commercially significant. Parasites impact fish survival, affecting aquaculture and wild populations. Aim: This study aimed to investigate the most prevalent helminths infecting different organs of S. undosquamis and to assess their impact on the overall health of the fish.

Methods

To investigate helminth infections, 200 S. undosquamis specimens were collected from local markets. Comparative analysis between uninfected and infected specimens was conducted using organ histopathology, evaluation of digestive tract mucus secretion patterns, and measurement of specific biochemical markers present in the mucus.

Results

Helminth infection affected 75% of the fish, primarily targeting the stomach and intestine, with Contracaecum sp. being the most prevalent and L. intestinal is being the least common, which is the first time that helminth infection has been recorded in this host. Larger fish were more susceptible to infection than smaller ones, with males showing a slightly higher infection rate than females. Histological analysis identified widespread tissue damage in multiple organs of infected fish. Infection was associated with increased mucus secretion and enzymatic changes, including elevated protease and lipase activities, as well as decreased α-amylase activity. Additionally, higher IgD levels were increased in individuals with heavy infection.

Conclusion

The study underscores the high prevalence and pathological effects of helminth infections in S. undosquamis, recommending further investigation into environmental factors influencing these infections. This also highlights the importance of understanding the emergence of L. intestinalis in this newly recorded host.