Chytrids and what effects their transmission sucess

The understanding of parasite characteristics, their contribution to overall fitness and the influence of both the external and host environment is a poorly studied area but could play a dynamic role in predicting disease outcome. Agha et al., 2018, used transmission success as a proxy for fitness while studying the influence of life-history traits on the of chytrid parasites during infection of the cyanobacterium Planktothrix spp. Interestingly, due to the positive correlations between sporangial size and the numbers of contained zoospores,  was noted that chytrids are potentially able to exploit trade-offs between reproductive output and propagule longevity depending on the environment to maximise fitness. Overall the study found that transmission success in chytrids is the result of an interaction between individual traits and the host environment individually or connected with the external environment. Successful evasion of host barrier defences appears to be driven purely by the host environment. Alternatively, parasite fitness traits related to the efficiency of the extraction of nutrients are influenced by both the host environment and environmental interactions. In future, an understanding of these traits will lead to the development of a better understanding of individual infection mechanisms. 

Agha, R., Gross, A., Gerphagnon, M., Rohrlack, T. and Wolinska, J. (2018). Fitness and eco-physiological response of a chytrid fungal parasite infecting planktonic cyanobacteria to thermal and host genotype variation. Parasitology, 145(10), pp.1279-1286.