POLLUTANT REMOVAL AND THE HEALTH EFFECTS OF ENVIRONMENTAL POLLUTION Efficacy of Andrographis paniculata supplements induce a non-specific immune system against the pathogenicity of Aeromonas hydrophila infection in Indian major carp (Labeo rohita) Radhakrishnan Palanikani 1 & Kanagaraj Muthu-Pandian Chanthini 1 & Ramaiah Soranam 1 & Annamalai Thanigaivel 1 & Sengodan Karthi 1 & Sengottayan Senthil-Nathan 1 & Arunachalam Ganesan Murugesan 1 Received: 29 November 2018 /Accepted: 11 July 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract Aeromonas hydrophila, an opportunistic fish pathogen, which causes several major diseases including skin ulcer and haemorrhagic septicemia, contributes considerably to the lethality in aquaculture. Chemical and antibiotic treatment employed against A. hydrophila for disease management are expensive and consequently prompted the advent of drug resistance among the pathogens. To overcome these draw backs, alternative aquatic disease control methods using conventional plant-based medicines are focussed. Our present study aimed to augment the fish non-specific immune system with the implementation of methanolic crude extracts of Andrographis paniculata to Labeo rohita, for evaluating their efficacy against A. hydrophila. Histology of major organs of A. hydrophila-infected fish such as the gills and liver displayed severe tissue damage. A. paniculata extracts exhibited the strong antibacterial activity against A. hydrophila even at lower concentrations (50 μl). The extracts also altered the haema- tological profile of treated infected fishes by increasing the levels of haemoglobin and total erythrocyte-leucocyte counts, along with the phagocytic index. The extracts also had a significant impact on modifying the anatomy and swimming pattern of infected fish, post treatment with the extracts. Also, A. paniculata treated infected fishes in all the plant extract administration methods, viz. injection, oral feeding and diffusion, and reduced the cumulative mortality rate to less than 30%. Even lower concentrations of A. paniculata extracts (50 μl) resulted in maximum relative percentage survival of treated fishes. Therefore, our findings suggest that A. paniculata was effective against A. hydrophila infection in aquaculture, thereby maintaining a healthy status of these fishes in aquaculture. Keywords Skin ulcer . Mortality . Haematology . Histology . Survival Introduction Fish, an aquaculture food product stands a very valuable source of animal protein besides essential nutrients. Over the former times, aquaculture has stayed one among the fastest food-generating areas in the world (Bilen et al. 2016a; FAO 2016). Aquaculture product including fish constitutes 20% of food consumption in developing countries (Béné et al. 2007). Fish contributes to near 50% of protein and minerals in the diet to the people of South Africa and Africa (Richardson et al. 2011). Due to the increasing demand of fish supply, aquacul- ture of economically important fishes is being established globally. However, cultivated fish are vulnerable to many dis- eases and an upsurge of disease epidemics has been reported owing to the escalation, resulting in above partial or full loss of production. Fish production from aquaculture is hindered by several limiting factors, for instance overcrowding, meagre water value, poor nutritional status and handling subsidize to physiological variations in fish such as trauma or immunosup- pression and, therefore, amplify vulnerability to infection (Bilen et al. 2016b). Moreover, high concentrations of fish Responsible editor: Philippe Garrigues * Sengottayan Senthil-Nathan senthil@msuniv.ac.in; senthilkalaidr@hotmail.com 1 Sri Paramakalyani Centre for Excellence in Environmental Sciences, Manonmaniam Sundaranar University, Alwarkurichi, Tirunelveli, Tamil Nadu 627 412, India https://doi.org/10.1007/s11356-019-05957-7 / Published online: 30 July 2019 Environmental Science and Pollution Research (2020) 27:23420–23436