Camallanus

Camallanus is a genus of parasitic nematodes commonly found in freshwater and saltwater fish. These roundworms belong to the order Camallanida and are known for their distinctive buccal capsule, which is heavily sclerotized and often described as funnel-shaped. The body of Camallanus worms is typically reddish or pinkish, and they can vary in size, with some species reaching several centimeters in length.

The life cycle of Camallanus typically involves indirect transmission. Intermediate hosts, often small crustaceans like copepods, ingest the parasite's eggs or larval stages. Fish then become infected by consuming these infected crustaceans. Within the fish's digestive tract, the nematodes mature, mate, and reproduce, with the female worms releasing eggs that are then shed in the feces of the host fish, thus continuing the cycle.

Camallanus infections can affect a wide range of fish species, from aquarium inhabitants to commercially important food fish. In heavily infected fish, the parasites can cause intestinal damage, inflammation, and impaired nutrient absorption, leading to symptoms such as weight loss, lethargy, poor growth, and sometimes visible worms protruding from the anus. Diagnosis is usually made by observing the characteristic eggs or adult worms in fecal samples or during necropsy. Treatment options for Camallanus infections in fish often involve the use of anthelmintic medications.