Leishmania infantum is a protozoan parasite transmitted by female phlebotomine vector (sand flies). However, other routes of transmission have been demonstrated, such as congenital or sexual, or even direct dog to dog. The dogs are the main reservoir host but hares and humans also can harbour the parasite. Canine Leishmaniosis is endemic in the Mediterranean basin, and also in other parts of the world such as South America, Africa and Southern America. It is worth noting that many dogs will be completely asymptomatic and it may take years before they become overtly ill. The clinical disease is usually fatal and is a major zoonosis, dogs being the main reservoir. Human leishmaniasis (note the spelling is different) will typically affect young children and immunodeficients, and is a serious public health issue.
In practice, the highly variable clinical manifestations and relative rarity of the disease complicates the diagnosis. Cutaneous leishmaniosis is a common form. Skin lesions are observed in over 80% of the clinically affected animals and are varied: hyperkeratosis, alopecia, papules, pustules, nodules, erosion/ulceration… Peripheral lymphadenomegaly is also commonly found. Visceral leishmaniosis will cause a range of symptoms, typically systemic and affecting multiple organs. E.g. weight loss, lethargy, PUPD, vomiting and diarrhoea, kidney failure, epistaxis…
When the disease is suspected, a thorough history and clinical examination is crucial. Indeed, dogs can be asymptomatic for a very long time before developing symptoms, and a pet owner might not find relevant to tell you about a holiday several years before. A range of tools are available to confirm the suspicion: in-house antibody testing, quantitative serology, PCR, cytology/histology…
Once confirmed, the prognosis varies from fair to very poor based on the severity of the symptoms. Signs of kidney failure will be one of the main negative factors. The treatment is based on allopurinol combined with miltefosine (oral treatment, available in the UK via a special import certificate) or meglumine antimoniate (injectable). Owners have to be warned that the treatment is long, costly and requires close monitoring. Allopurinol is typically given for 6 to 12 months, while miltefosine and meglumine antimoniate will require 28 days and 4-6 weeks administration respectively. A lack of clinical response, as well as a relapse whilst on treatment or shortly after will the mean the prognosis is guarded.
So how should first opinion UK vets tackle canine leishmaniosis?
Offer testing to any animal imported, especially rescues from southern European countries. A positive result needs to be discussed with the owner, but does not mean the animal will ever show any clinical signs. Don’t forget other vector borne diseases.
As a simplified rule based on common symptoms, any dog presented with peripheral lymphadenomegaly and skin lesions and having travelled in endemic regions should be tested.
Prevention is the key! Convincing clients to protect their pets against an unfamiliar disease will always be more challenging. However, the severity of the potential symptoms and implications of treatment should be explained, as well as the zoonotic potential. Any owner enquiring about a pet passport should be asked what part of the EU they are planning on visiting. Some basic information about the disease and vector should be provided, and prevention discussed. Sand flies repellent collars are available, and a vaccine is fully licensed in the UK. The important of training support staff cannot be stressed enough, as they will be the first line of contact and information with clients, who will appreciate being made aware of this complex condition.
1. Chiara Noli, Manolis N. Saridomichelakis,An update on the diagnosis and treatment of canine leishmaniosis caused by Leishmania infantum (syn. L.chagasi), The Veterinary Journal (2014), doi: 10.1016/j.tvjl.2014.09.002
2. Solano-Gallego L, Miró G, Koutinas AF, Cardoso L, Pennisi MG, Ferrer L, Bourdeau P, Oliva G, Baneth G: LeishVet guidelines for the practical management of canine leishmaniosis. Parasites & Vectors 2011; 4:86.