The frequency of photosensitization in a dairy cattle herd infected by Leptospires

Leptospirosis is a bacterial zoonotic disease, which can induce hepatic lesions. Photosensitization (PS)maybe is the result of accumulation of photodynamic agents in unpigmented area of the skin exposed tosunlight which occurred due to hepatic lesions. An outbreak of leptospirosis was occurred in a dairy cattleherd complex with 760 dairy milking cows in March (1990). Totally, 412 cows (54.21%) showed clinicalsigns including fever, systemic mastitis, haemoglobinuria, jaundice, lameness, abortion and stillbirth. Themicroscopic agglutination test (MAT) was used for diagnosis of leptospirosis. The herd was infected withLeptospira interrogans grippotyphosa, L. interrogans icterohaemorrhagiae, L. interrogans pomona, L.interrogans canicola and L. interrogans hardjo. Only one (0.13%) cow showed PS in the unpigmented skindorsum. MAT showed that she was infected with L. interrogans pomona, L. interrogans hardjo and L.interrogans icterohaemorrhagiae with titre of 1 : 3200 of antibody. In spite of the high incidence ofleptospirosis, the frequency of PS was too low.