This chapter describes parasites of the digestive system, respiratory system, liver, pancreas, circulatory system, nervous system, reproductive/urogenital system, locomotory system, connective tissue, and the integument of dogs and cats. Two species of the genus Mammomonogamus, which is closely related to Syngamus, are parasitic in the nasal cavities of cats. Infections are usually asymptomatic but affected animals may sneeze and have a nasal discharge due to irritation of the nasal mucosa. Adult worms are red in colour, 1‐2 cm long and permanently joined in copula. Diagnosis is based on clinical signs and the finding of eggs in the faeces or adult worms on postmortem. The presence of eggs in faeces or sputum and a nasal discharge are indicative of infection. On fox‐rearing farms, care should be taken to ensure that runs are created in areas where the soil is dry and free‐draining.