Roundworms from the genus Stephanofilaria are a cause of dermatitis and skin lesions on cattle all over the world. Where the skin lesions occur depends on the species of Stephanofilaria present. In Australia, skin lesions located on the inner corner of the eye (Figure 1), head, neck (Figure 2), and sternum have been attributed to an unnamed species of Stephanofilaria that is transmitted by buffalo fly. Stephanofilaria have been detected in less than 40% of skin lesions (Figure 3, Figure 4 and Figure 5) so they are unlikely to be the only cause of lesions on cattle in Australia. The large numbers of buffalo flies often observed feeding on the skin areas with lesions (Figure 1 and Figure 6) is thought to contribute to the severity of the lesions.
See the section on buffalo fly lesions
Figure 1. Skin lesion adjacent to the medial canthus of the eye: buffalo flies (arrows) are seen feeding in the lesioned area. Image courtesy of Constantin Constantinoiu
Figure 2. Skin lesion on the neck of a cow: raised, circumscribed, hairless, cracked and scab encrusted skin area up to 10 cm in diameter. Image courtesy of Constantin Constantinoiu
Figure 3. Female worm, most likely Stephanofilaria spp, in a cyst like structure: the arrow shows microfilariae within the uterus. H&E stained section from a skin area with lesions. Image courtesy of Constantin Constantinoiu
Figure 4. Microfilariae of Stephanofilaria spp. enclosed in vitelline membranes (arrows) from a skin area with lesions. H&E stained section from a skin area with lesions. Image courtesy of Constantin Constantinoiu
Figure 5. Adult male Stephanofilaria sp nematodes recovered from a skin lesion. Image courtesy of Muhammad Noman Naseem
Figure 6. Skin lesion on a cow with buffalo flies feeding on it. Image courtesy of Constantin Constantinoiu