Toxocariasis in dogs and cats is diagnosed primarily on the basis of clinical criteria during examination. In large numbers, the parasite causes diarrhoea, emesis, stunted growth, abdominal discomfort and, in severe cases, intestinal obstruction and distended abdomen (pot-bellied appearance).
Laboratory diagnosis of patent Toxocara infections is achieved by the detection and specific identification of Toxocara eggs in the faeces, following a concentration technique. Toxocara eggs are rough-shelled, spherical or oval and approximately 87 × 75 μm (T. canis) and 75 × 65 μm (T. cati).
Concentration/flotation techniques, however, are insensitive and may miss up to one-third of patent infections, not least because shedding of eggs may occur intermittently.
The development of rapid, highly sensitive and specific diagnostic tests that can be executed in the field is an essential element in any future control programmes. Faecal antigen testing is one such example and is becoming commercially available.
This will provide a sensitive and specific alternative to faecal flotation/concentration of eggs but will not detect immature adults in the gut or be able to detect arrested larval stages in the tissues.
