Differences in health parameters between pups with perineal ulcers and matched controls (pups without perineal ulcers). (a) Almost half of the pups with perineal wounds had bloody diarrhoea compared to only 4% of pups without perineal wounds (GLM, Z = 3.54, d.f. = 90, p < 0.001). (b) Pups with perineal wounds had lower haemoglobin concentration compared with controls (GLM, Z = −3.89, d.f. = 83, p < 0.001). (c) Pups with perineal wounds had higher numbers of hookworm eggs in their faeces compared with controls (GLM, Z = 2.01, d.f. = 84, p = 0.043). (d) Pups with perineal wounds had higher numbers of leucocytes in the peripheral blood when compared with controls (GLM, Z = 2.43, d.f. = 81, p = 0.015).