Shrews are a very ancient group of primitive mammals that resemble most closely the proto-mammals. They are not closely related to rodents because rodents evolved from different groups of mammals. According to Dufton (1992), the known venomous species of shrew are: the northern short-tailed shrew (Blarina brevicauda), the Haitian solenodon (Solenodon paradoxus), the European water shrew (Neomys fodiens) and the Mediterranean shrew (Neomys anomalous). Another venomous shrew is the southern short-tailed shrew (Blarina carolinensis). It has also been suggested that the Cuban solenodon (Apotogale cubanus), the American shrew (Sorex cinereus) and the Maritime shrew (Sorex maritimensis) could be venomous. The northern short-tailed shrew (Blarina brevicauda) and its closely related species use a paralytic venom in its saliva to paralyze insects, other invertebrates (worms, annelids etc.), nesting birds and small mammals which it then stores, alive in its den, for future feeding (Martin 1981; George et al. 1986; Dufton 1992).
The shrew venom literature generally consists of seven articles from the 40s and 50s and one MA thesis in 1966 [Christenbury 1966]. These are summarized in a review [Dufton 1992]. Using a crude ammonium sulfate precipitate of shrew saliva glands, Ellis and Krayer (1955) concluded the active agent was probably a protein and, because of its inability to dialyze, a larger protein. A major contribution of the Ellis & Krayer work was to show activity in cats, dogs, mice, rats, guinea pigs and rabbits. Christenbury [1966] showed Ellis & Krayer's preparation stopped oxygen consumption by mouse kidney and liver slices. Japanese patent application (JP 10-236963; 1998) appears to disclose an alcoholic extract of saliva glands from two shrew species (Sorex unguiculatus & Sorex shinto saevus) as a calcium channel blocker and its use as a hypotensive. The purity is low—the extract includes any compounds that would dissolve in 70% ethanol. There is no information about the responsible active molecule/s in the unknown mixture of compounds.