Ehrlichia (Cytoecetes) phagocytophila predisposes to severe contagious ecthyma (Orf ) in lambs.

Eight lambs experimentally infected with Ehrlichia (Cytoecetes) phagocytophila 7 days before exposure to orf virus were compared with control lambs infected with orf virus alone. The dually infected animals differed from the controls in showing skin lesions of greater severity, prolonged viral shedding, and lower antibody titres. Infection with E. phagocytophila had no significant effect on virus-specific lymphocyte proliferation. Such proliferation was detected in the peripheral blood of all lambs as early as 7 days after exposure to orf virus.