Ichthyophthiriasis in carp Cyprinus carpio : infectivity of trophonts prematurely exiting both the immune and non-immune host

• Published in: Diseases of aquatic organisms Vol. 36; no. 3; pp. 201 - 207
• Main Authors: WAHLI, T, MATTHEWS, R. A
• Format: Journal Article
• Language: English
• Published: Oldendorf Inter-Research 31-05-1999
• Subjects: Animals; Biological and medical sciences; Carps - immunology; Carps - parasitology; Ciliophora Infections - immunology; Ciliophora Infections - veterinary; Cyprinus carpio; Disease Susceptibility - immunology; Fish Diseases - immunology; Fish Diseases - parasitology; Fisheries; Freshwater; Fundamental and applied biological sciences. Psychology; Hymenostomatida - immunology; Hymenostomatida - pathogenicity; Ichthyophthirius multifiliis; Life cycle. Host-agent relationship. Pathogenesis; Protozoa; Protozoan Infections, Animal - immunology; Protozoa; Host parasite relation; Protozoal disease; Immune response; Parasite; Host; Parasitosis; Immunity; Infection; Freshwater environment; Ichthyophthiriosis; Pathogenicity; Vertebrata; Ichthyophthirius multifiliis; Prematurity; Pisces; Emergence; Ciliata; Cyprinus carpio; Cyprinidae; Aquaculture
• ISSN: 0177-5103; 1616-1580
• DOI: 10.3354/dao036201

Ichthyophthirius multifiliis exposed to naturally immunised carp established short-term infections, the majority of parasites actively emerging within 2 h of entering the epidermis. A small, but significant, number of these expelled parasites were shown to retain theront-like properties with the capacity to directly re-invade a further fish host. Infectivity fell rapidly with time in the host and was comparable to that of trophonts of a similar age artificially induced to emerge from non-immune hosts with the aid of MEM (minimal essential medium). Trophonts recovered with MEM from immune carp 2 to 8 h post infection rarely established infections upon exposure to susceptible new hosts and no infections resulted from older trophonts recovered after 8 to 24 h exposure; older trophonts, however, represented only a small percentage of the original parasite population. A low level of infectivity was recorded in trophonts collected with the aid of MEM from non-immune carp after up to 24 h of infection. The results are discussed in relation to theront transformation and evasion of the host immune response.