Lymphocystis is reported widely in home aquariums and is associated with fish facing high levels of stress; which is usually attibuted to poor water quality (Lawler & Donnes 1977) or the stress of moving fish from one environment to another e.g. moving fish from the pet shop to the home aquarium.
Lymphocystis causes hypertrophy (increase in volume) of the tissue cells of infected fish, which leads to visible white, pinprick nodules forming usually on the fins and body (Lawler & Donnes 1977). Unfortunately the formation of these nodules often lead to a mis-diagnosis of Ichthyophthirius multifillis (Fresh Water White Spot Disease).
The diagnosis of Lymphocystis is difficult in the early stages due to its similar resemblance to Fresh Water Whitespot Disease, however the white nodules in Lymphocystis will clump together to form large clusters, usually within two weeks of exhibiting symptoms (Paperna et al 1982). Infected fish also exhibit swimming difficulty and may also be inactive due to a breathing difficulty associated with nodules growing over the gills (Paperna et al 1982).
Viruses can evolve rapidly because they lack many factors that correct impurities in their DNA or RNA that exist in humans. Therfore mutations in viruses are a common occurence (Bamford et al 2002). Because of this, there is no existing cure for Lymphocystis. Therefore treatment should be focused on decreasing the stress on infected fish to allow the immune system to fight the virus and to decrease the risk of secondary infections.
 |
| Early stage Lymphocystis |
 |
| Late stage Lymphocystis |
References:
Bamford, D. Bernett, R. Stuart, D 2002, 'Evolution of Viral Sructure', 'Theoretical Population Biology', vol. 61, pp. 461-470
Lawler, A. Donnes, J 1977, 'New Hosts for Lymphocystis, and a List of Recent Hosts', 'Journal of Wildlife Disease' vol. 13, pp. 307-312
Paperna, I. Sabnai, H. Colorni, A 1982, 'An Outbreak of Lymphocystis in Sparas aurata L. in the Gulf of Aqaba, Red Sea', 'Journal of Fish Diseases', vol. 5, pp. 433-437
Yan, X. Wu, Z. Jian, J 2011, 'Analysis of the Genetic Diversity of the Lymphocystis Virus and its Evolutionary Relationship with its Host', 'Virus Genes, vol. 43, pp. 358-366
That’s very interesting. I’m curious about how they know it is stress related. Have they checked for stress hormones in the blood? If so, what hormones do they test for?
ReplyDeleteHi Tasmin,
ReplyDeletegreat question as always. Stress in fish is an enormous subject, researchers are still scratching the surface. Basically it depends on the type of stress, as it is a physiological response to external factors. When a fish is threatened by say a predator, there's a release of these aromatic amines called catecholamines (includes things like adrenaline etc) which gives fish a boost of energy, so researchers essentially test for the abundance of these amines in the blood. In this post however, i'm referring more to the release of corticosteriods (mainly cortisol-which is released to essentially all if not most stress factors) into the blood. interestingly i did a little speech about hormonal effects on behavior a few weeks ago, its a great subject.