Canine leishmaniosis: an update

Abstract

Canine leishmaniosis caused by the protozoan parasite Leishmania infantum has entered the UK. Entry appears linked to pet dogs accompanying their owners (on vacation) to the Mediterranean basin where this vector-borne canine disease is prevalent. The parasite resides in the superficial dermis of infected dogs, either within macrophages or free in host tissue. L. infantum is transmitted naturally through sandfly bites. Sandflies are not currently present in the UK. Vertical transmission from infected bitches to puppies and transmission through blood transfusion have been confirmed, while sharing of hypodermics have only been proven experimentally. Some infected dogs remain asymptomatic with this resistance to disease development being associated with a strong cell-mediated immune response. Diseased dogs present with varied symptoms including generalised enlargement of lymph nodes, scaly dermatitis, anaemia, anterior uveitis and renal dysfunction. Clinically suspect dogs should be tested by fine needle aspiration of lymph nodes and/or bone marrow to perform cytology and polymerase chain reaction (PCR). Blood PCR lacks a certain degree of sensitivity. Indirect diagnosis through serology while routine is problematic in interpreting results and antibody titres. The recommended treatment protocol is a combination of the antimoniate N-metilglucamine subcutaneously, and allopurinol orally. Direct parasite transmission from dogs to humans has not been demonstrated. A commercial vaccine has emerged that offers options for prevention, which is useful for pets travelling to areas where the infection is endemic, particularly if they are staying for an extended period during the season when sandflies are active. Practitioners need to evaluate each individual case, based on client compliance, response to treatment and follow-up evaluation before deciding whether or not to consider euthanasia.