Canal de Castilla Rey (Palencia), considered the beginning of the Northern Branch, Valladolid and Medina de Rioseco, lying at the end of the Southern Branch and Campos Branch respectively. The countryside crossed by the canal is of interest for its birdlife. In the Tierra de Campos there are two large Special Protection Areas ("La Nava-Campos Norte" and "La Nava-Campos Sur") which are notable for the birds such as great bustards ("Otis tarda") which live in the dryland farming areas (sometimes described as "steppes") which are typical of the region. The canal, on the other hand, provides habitats for wetland birds such as the
Porphyria cutanea tarda because of liver toxicity. Finally, due to the strong association between PCT and Hepatitis C, the treatment of Hepatitis C (if present) is vital to the effective treatment of PCT. Chloroquine, hydroxychloroquine, and venesection are typically employed in the management strategy. Porphyria cutanea tarda has a prevalence estimated at approximately 1 in 10,000. An estimated 80% of porphyria cutanea tarda cases are sporadic. The exact frequency is not clear because many people with the condition never experience symptoms and those that do are often misdiagnosed with anything ranging from idiopathic photodermatitis and seasonal allergies to hives. Porphyria cutanea tarda is