Both dogs and occasionally cats can be infected with Leishmania and the clinical presentation can be extremely variable. Thus patients can be presented due to red eyes, blindness, ocular or periocular swellings, abnormal appearance to one or both eyes or just an ocular discharge. Systemic illness is frequently also present, most notably skin disease but also general malaise, weight loss, lameness or signs of hepatic or renal disease. Indeed it is common for the owner to present the patient due to the systemic signs with the ocular symptoms only noted during the clinical examination. Any age of dog can be affected although young to middle-aged adults are perhaps more commonly encountered with the disease.
The case history again is very variable. However, one reliable factor is that the animal will have travelled through an endemic area. Areas where Leishmania infantum and the vector Phlebotomus spp. (sand flies) are found include the Mediterranean shore, parts of east Africa and India, while Leishmania chagasi is located in parts of Central and South America. Thus the travel history of the patient should alert one to the possibility of this disease. The patient might be acutely presented but more frequently there is a history of illness for up to several weeks. The skin lesions, if present, tend to be progressive, scaly and non-pruritic.
General clinical examination might be normal, but this is the exception. Careful attention to the skin should be made, as areas of alopecia, frequently with seborrhoea and desquamation, might be present. These might be just in the periorbital area or on the head, but can be more widespread. The patient might be thin, have renal or liver pain on abdominal palpation, or might show lameness. Thus there can be a variety of systemic abnormalities present.
Ophthalmic examination can be similarly variable. In some cases the eyes will be normal on initial examination (but ocular changes can develop later in the course of the disease, even after treatment has been instigated). Some patients will have thickened, inflamed eyelids – in either a diffuse or a nodular pattern (Figure 38.1). Some will have marked chemosis and conjunctivitis, with or without corneal involvement. Nodular swellings at the limbus might be noted. Corneal ulceration and vascularization are occasionally present. Anterior uveitis is common, with miosis, aqueous flare and iridal swelling (Figure 38.2). Such patients will be in pain and can be blind. If the posterior segment is visible then signs of chorioretinitis might be present, but the anterior segment is more frequently the area of the uveal tract which is most inflamed. Occasionally orbital cellulitis will be present and the patient will have a painful exophthalmos. Schirmer tear test readings should be performed – some dogs will have keratoconjunctivitis sicca. Clearly fluorescein testing is mandatory. If tonometry is available, intraocular pressures should be assessed – secondary glaucoma can be a feature. Most cases are bilateral but not necessarily symmetrical.
Image courtesy of Teresa Peña, College of Veterinary Medicine, Autonomous University of Barcelona, Spain.