Gyro-Scope

Background
Gyrodactylids are highly contagious fish parasites. This genus consists of an estimated 20,000 species, some of which are highly pathogenic and cause significant economic and ecological damage. For example, Gyrodactylus salaris has recently undergone a host-shift and now infects salmon, causing >500 million € economic damage and endangering wild salmon stocks throughout the EU.

The Software
Gyro-Scope is an "agent-based" computer model to study the infection dynamics of gyrodactylid parasites of fish hosts. The program uses a small number of input variables, (1) the initial number of parasites at the start of the infection, (2) the size of hosts and (3) the gestation times of parasites for their first and subsequent embryos. With these input values it can estimate the parasite load on individual fish over the entire infection trajectory. The simulated data are in close approximation to the empirical data from laboratory experiments in which guppies (Poecilia reticulata) were infected with Gyrodactylus turnbulli and G. bullatarudis parasites (van Oosterhout et al. 2003; Cable & van Oosterhout 2007).

The Output
The output generated by the model is for each parasite individually and includes: (1) simulation number, (2) time step, (3) parasite number, (4) position (X and Y coordinate) of each parasite at each time step, (5) "Resources" of the parasite and (6) "Constitution" of the parasite. The values in the column "Resources" reflect the number of feeding opportunities (in hours) each parasite has achieved. When the value in "Resources" equals or exceeds the user-defined value for "Gestation time first-born (in h)" or "Gestation time 2nd, 3rd, 4th and 5th born (in h)", a new parasite is born. If the value in the column "Constitution" equals zero, the parasite dies. In addition to this detailed output, summary statistics of the total number of parasites at each time step is given in a separate spreadsheet. From these data parasite life history and infection dynamics can be calculated.