Red water fever

Definition

A severe, acute hemolytic disease of cattle, sheep, and other ruminants caused by the apicomplexan protozoan *Babesia divergens* or related *Babesia* species, characterized by destruction of red blood cells, hemoglobinuria (dark red urine), fever, anemia, and often fatal outcomes if untreated. The disease is transmitted biologically by hard ticks of the family Ixodidae, primarily *Ixodes ricinus* in Europe, which serve as both vectors and reservoir hosts through transovarial and transstadial passage of the parasite.

Etymology

From the characteristic dark red or port-wine colored urine caused by massive hemolysis and hemoglobin excretion.

Example

In upland sheep pastures of Scotland, *Ixodes ricinus* nymphs transmit *Babesia divergens* to naïve grazing lambs, precipitating red water fever outbreaks during peak tick activity in late spring; control relies on acaricide treatment of sheep and habitat management to reduce tick populations.

Synonyms

• babesiosis
• cattle babesiosis
• tick fever (regional, imprecise)

Related Terms

• Babesia
• Ixodes ricinus
• biological vector
• Transovarial transmission
• hemolysis
• hemoglobinuria
• Theileriosis
• anaplasmosis
• acaricide

Usage Notes

The term is primarily used in British and Irish veterinary contexts; in North America, 'babesiosis' predominates, and 'redwater' (one word) is common in informal usage. Distinguish from 'redwater disease' caused by *Clostridium haemolyticum* (bacterial, non-tick-borne). Diagnosis requires blood smear examination or PCR to confirm *Babesia* spp. versus other hemoparasites. The disease exemplifies the veterinary entomology interface: tick population dynamics directly determine disease risk, making integrated tick management essential to prevention.