Rickettsia are obligate intracellular coccoid, rod-shaped or pleomorphic gram-negative bacteria that parasitise in reticuloendothelial cells or erythrocytes. They are usually transmitted by arthropods.

Rickettsia are divided into the categories “spotted fever group”, thyphus group and “others”, which includes Coxiella burnetii.

In the USA, Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever, and in the Mediterranean area, Rickettsia conorii, the causative agent of Mediterranean spotted fever, are of central importance in animal infections. Infected dogs may remain asymptomatic or show symptoms ranging from lymphadenopathies, fever, hyperesthesia, peripheral oedema up to lameness.