First Case of Intestinal Worm in Popular Aquarium Fish

Jenn Hoskins
6th March, 2024

First Case of Intestinal Worm in Popular Aquarium Fish

Image Source: Natural Science News, 2024

Key Findings

  • In South India, flowerhorn cichlids were found to host a harmful human-infecting parasite
  • Infected fish showed symptoms like dark color, poor appetite, and abnormal swimming
  • DNA tests confirmed the parasite as Paracapillaria philippinensis, a first for Indian fish
The ornamental fish industry is a vibrant global market, with enthusiasts seeking out exotic species to add to their aquariums. Among these, the flowerhorn cichlid is a favorite due to its vivid colors and unique appearance. However, a recent discovery has raised concerns about the health of these fish and potential risks to humans. Researchers from Tamil Nadu Dr. J. Jayalalithaa Fisheries University have identified a parasitic nematode, Paracapillaria philippinensis, in flowerhorn cichlids from South India[1]. This finding is significant as it marks the first time this parasite has been reported in fish from India, and it confirms that flowerhorn cichlids can be definitive hosts for this nematode. The study observed infected fish displaying symptoms such as darkened coloration, lack of appetite, lethargy, abnormal swimming, and the presence of white, stringy feces. Upon microscopic examination, adult worms, larvae, and unembryonated eggs were found in the intestinal content and feces of the fish. To confirm the identity of the parasite, researchers employed a molecular approach using PCR (Polymerase Chain Reaction) to amplify specific regions of the parasite's ribosomal RNA (rRNA) genes. The 18S rRNA and the small subunit (SSU) rRNA gene sequences were used to accurately identify the species as P. philippinensis. These sequences were then submitted to GenBank, a global database of genetic information. This discovery is of particular concern due to the zoonotic nature of P. philippinensis, meaning it can be transmitted from animals to humans. In humans, this parasite causes intestinal capillariasis, a potentially fatal condition if left untreated[2]. The disease is characterized by symptoms such as abdominal pain, chronic diarrhea, and significant weight loss[3]. Prior studies have shown that human infection is typically accidental and can be diagnosed and treated effectively if caught early. A specific nested PCR test has been developed to improve diagnosis, which is sensitive and specific to this parasite[2]. The new study builds upon previous research that has explored the genetic and morphological diversity of Capillariinae nematodes[4], as well as the prevalence of various parasites in reptiles, which like fish, are often kept as pets[5]. The molecular techniques used in the new study are similar to those used in the earlier study[4], which utilized the 18S rRNA gene to clarify the taxonomic positions of different Capillariinae species. This method has proven effective for identifying parasites that are difficult to distinguish based on morphology alone. The implications of the latest research are twofold. First, it provides an important reminder to fish handlers and hobbyists about the potential health risks associated with ornamental fish. Precautionary measures should be taken when handling live flowerhorn cichlids to prevent the transmission of P. philippinensis. Second, the study highlights the need for ongoing surveillance and research into the pathogens carried by pet animals, as they can have serious implications for human health. The prevalence of parasites in pet reptiles, as noted in a study of reptiles in Slovenia[5], underscores the importance of screening for specific pathogens before these animals are introduced into domestic settings. In conclusion, the identification of P. philippinensis in flowerhorn cichlids from India is a reminder of the interconnectedness of animal and human health. It emphasizes the need for vigilance in the ornamental fish industry and among pet owners to prevent the spread of zoonotic diseases. The use of molecular diagnostics in this field continues to be a powerful tool for identifying and managing parasitic infections, safeguarding both animal and human health.

Animal ScienceMarine Biology


Main Study

1) First report of Paracapillaria philippinensis infection in flowerhorn cichlid in India.

Published 5th March, 2024

Related Studies

2) Molecular detection of Capillaria philippinensis: An emerging zoonosis in Egypt.

3) Capillaria philippinensis in Upper Egypt: has it become endemic?

4) Morphological and molecular genetic characterization of three Capillaria spp. (Capillaria anatis, Capillaria pudendotecta, and Capillaria madseni) and Baruscapillaria obsignata (Nematoda: Trichuridae: Capillariinae) in avians.

5) Parasites in pet reptiles.

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