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Various factors such as species, breed, age, natural resistance, vector efficiency and immune status dictate whether clinical disease develops and its severity.

Various factors such as species, breed, age, natural resistance, vector efficiency and immune status dictate whether clinical disease develops and its severity.

==Diagnosis==

==Diagnosis==

On '''post-mortem examination''', a '''light yellow [[Transudate | transudate]]''' that '''coagulates on exposure to air''' is often found within the '''thorax, [[Pericardial Pathology | pericardium]] and abdomen.''' Volume may vary but may be several litres in cattle.  

On '''post-mortem examination''', a '''light yellow [[Transudate | transudate]]''' that '''coagulates on exposure to air''' is often found within the '''thorax, [[Pericardial - Pathology | pericardium]] and abdomen.''' Volume may vary but may be several litres in cattle.  

Most fatal cases will display the '''hydropericardium''' that gives the disease its common name, although this is seen more commonly in sheep and goats than cattle <ref> Henning, M. W. (1956) '''Heartwater'''. In: Anim Dis S Africa, ed 3. South Africa: ''Central News Agency Ltd'', 1155-1178</ref>

Most fatal cases will display the '''hydropericardium''' that gives the disease its common name, although this is seen more commonly in sheep and goats than cattle <ref> Henning, M. W. (1956) '''Heartwater'''. In: Anim Dis S Africa, ed 3. South Africa: ''Central News Agency Ltd'', 1155-1178</ref>