has been hampered by the difficulty of evaluating host resistance in the field and lack of reliable screening techniques.
Lack of reciprocity refers to the difficulty of sending host physicians abroad as well as failed attempts at building long-lasting relationships with foreign institutions.
Environmental heterogeneity significantly increases the difficulty of predicting host and pathogen fitness-related trait variation as the environment may alter both selection specificity and strength (Lazzaro and Little 2009; Wolinska and King 2009), leading to variation in specific gene frequencies in nature.
The poorly characterized capacity of bats to compensate for and respond to infection during hibernation demonstrates the difficulty of understanding how host-pathogen interactions influence disease manifestation and mortality.
In light of the difficulty of total expulsion of host tissue during nucleic acid extraction, this method offers (at least with respect to protein-coding genes) an a posteriori bioinformatic solution to ensure proper identification and filtration of contaminant sequences.
Untangling S. japonicum physiology can have important ramifications for efforts to control schistosmiasis, which remains a substantial challenge in endemic areas due to the difficulty of eradicating the snail intermediate hosts.
No attempt was made to control for kinship relationships between paired females in this study due to constraints on the availability of hosts combined with the difficulty of differentiating male and female E. nassaui.
It is easy to think of Ebola as an outlier, a rare and exotic disease that is particularly hard to learn about due to the sporadic nature of its outbreaks, the remoteness of the communities it affects, and the difficulty of containing transmission from its animal hosts.
Pathogens such as fungi, bacteria and especially viruses, are highly variable even within an individual host, intensifying the difficulty of distinguishing and accurately quantifying numerous allelic variants co-existing in a single nucleic acid sample.
These features contribute to the difficulty of integration of tissue-engineered constructs with the host tissue.
