Leishmaniasis in dogs

Health and Wellbeing

Leishmaniasis is a parasitic disease which luckily isn’t prevalent in the UK - the parasite unfortunately spreads the most in countries that boast a warmer climate.

If you’ve got a hound that likes a holiday, you’ll want to be aware of leishmaniasis, how it happens, what to look out for and if you can prevent it from happening altogether if you’re planning on travelling with your pooch.

Leishmaniasis in dogs

We’ve got a full guide here all about the disease and the pesky parasite that causes it, so keep reading for everything you need to know about leishmaniasis.

WHAT IS LEISHMANIASIS IN DOGS?

Leishmaniasis is a vector-borne disease, which is the term for an infection transmitted by blood-sucking animals such as mosquitoes, ticks, fleas, and in this case, a parasite called leishmania. Leishmania is a sneaky little parasite that needs to utilise another animal to develop and become infectious, so it chooses the sandfly, which goes on to transmit the leishmania parasite onto other humans and animals. Unfortunately, leishmaniasis can be incredibly severe, and it’s prevalent in over 70 countries.

Dogs can suffer from a variety of symptoms due to leishmaniasis, with the infection usually affecting dogs in a number of ways. They can suffer from a cutaneous (skin) infection and a visceral (organ) infection, which can be extremely severe and require urgent treatment. Some dogs might even be totally asymptomatic, unknowingly carrying the disease for several years.

Leishmaniasis is classed as a zoonotic disease, because the sandfly can bite a person and pass on the parasite. Zoonoses is when a disease can jump from animal to human, however the spread of leishmaniasis mainly happens through animals rather than through people.

WHAT CAUSES LEISHMANIASIS IN DOGS?

As we know, leishmaniasis is caused by a protozoan parasite called leishmania. Protozoan parasites are sneaky single-celled organism that can go undetected by the human eye for quite a while. Over 20 species of leishmania have been reported, and the disease can be found many species of animal.

LEISHMANIA

Dogs become infected with the leishmania parasite through the bite of a female sandfly. Nearly 100 species of sandfly are reported to be carriers of the parasite, so the disease is relatively widespread in several countries.

The leishmania life cycle begins with the female sandfly searching for a host to feed from, which results in them feeding on the blood of a mammal host infected with the leishmania parasite. The nasty parasite grows and continues its lifecycle inside the sandfly.

The small, snapping sandfly, which is truly tiny, about one fourth the size of a mosquito, acts as the intermediate host for the leishmania parasite. By harbouring and allowing the parasite to develop inside its body, the sandfly enables the spread of infection by injecting the parasite into other mammals through its bite. Unfortunately, the canine population is one of predominant choices for the sandfly.

Here, the dog becomes the reservoir host (along with various other infected species), sustaining the parasite within its body. A reservoir host is the thing in which the infectious pathogen clings to for survival, so even if the dog is seeing no symptoms of the parasite, they’re still harbouring it and will still be infectious to sandflies who aren’t yet carriers of leishmania. This is how the cycle of infection continues.

WHAT ARE THE SIGNS AND SYMPTOMS OF LEISHMANIASIS IN DOGS?

Pinpointing the exact set of symptoms for canine leishmaniasis is tricky, because every dog responds to the infection so differently. There isn’t one definite symptom set.

It’s believed to be that the symptoms will depend on the strain of leishmania parasite your dog is infected with, your dog’s genetics and their general health status. Often, a dog can be infected for months without showing any signs of the disease, with a study reporting 45.5% of dogs were totally asymptomatic. However, dogs that do suffer from the disease encounter a whole spectrum of different symptoms. Also, because some dogs don’t even show any signs at all, it means that the incubation period is unpredictable. The incubation period is the time it takes from the point of infection until symptoms start to arise.

The symptom set can also vary so much because of the two main types of infection, the cutaneous form and the visceral form. The visceral form is the most common type of leishmaniasis, affecting various organs which can range from being just a mild illness to having fatal consequences.

Symptoms for the visceral form of leishmaniasis include:
On the other hand, the cutaneous form of leishmaniasis affects the skin in various ways, including:
  • Hardening of tissue on the snout and footpads, called hyperkeratosis
  • Loss of pigment in the skin
  • Ulcers
  • Skin lesions (abnormal changes of the skin tissue)
  • Dull and brittle coat
  • Hair loss

The vast array of symptoms means that identifying leishmaniasis might be difficult based on the clinical signs alone.

HOW IS LEISHMANIASIS IN DOGS DIAGNOSED?

Diagnosis will be based on a number of things. Firstly, the symptoms your dog is experiencing and if they’ve recently travelled to a country where leishmaniasis is widespread will be enough for your vet to suspect the illness.

To confirm whether or not your dog has been infected with this pesky parasite, a combination of various tests, potentially including blood, urine and skin samples will be necessary.

HOW IS LEISHMANIASIS IN DOGS TREATED?

Treatment will depend on what symptoms, if any, your dog is displaying. Dogs that have no evidence of symptoms may require no treatment whatsoever, however most dogs will require some kind of medication. After a while, the medication should resolve any symptoms your dog was experiencing and all their tests will come back normal, at which point they should be able to come off treatment.

Sadly, treatment is unlikely to totally cure leishmaniasis and your dog will still be harbouring some element of the parasitic infection. This makes your dog prone to relapsing.

Unfortunately, treatment to prevent relapse can’t be continued for the entirety of your dog’s life as their immune system will begin to become resistant to the medication to the point where it has no impact. To avoid any serious relapses, medication will be recommenced to combat the relapse in its early stages. Leishmaniasis can be managed well with constant monitoring from both you and your vet.

CAN LEISHMANIASIS IN DOGS BE PREVENTED?

A vaccination against the leishmania parasite is licensed for use in the UK, but it isn’t in your dog’s core vaccination set that they’d normally be provided as a puppy. Therefore, if you’re planning on travelling to another country with your dog, especially one in which leishmania is widespread, it’s advised to get your dog fully vaccinated.

Topical treatments are also available to ward off sandflies, but these treatments are most widely available in countries where the bothersome bug is rife.

CAN I CATCH LEISHMANIASIS FROM MY DOG?

Humans can’t directly become infected with leishmaniasis from their dog. However, as the disease is zoonotic, people can catch it from the bite of a contaminated sandfly. As stated, dogs can be carriers of the leishmania parasite for several months, even years, so your dog could indirectly continue transmitting the disease to other animals and humans if an uninfected sandfly bites the infected dog and begins carrying the parasite.

There have been reports of dog-to-dog transmission through a bite and blood transfusions given from an infected dog to a non-infected dog, although this appears to be extremely rare.

RECAP

All in all, if you’re living in the UK, leishmaniasis isn’t really something that you and your four-legged friend need to worry about. Thankfully, the irritating sandfly insect doesn’t reside in the UK.

However, if you’re looking to travel with your dog, or you want to adopt a dog from overseas, it’s a good idea to get your pup vaccinated against leishmaniasis to stop that pesky parasite right in its tracks and keep your dog happy and healthy.

Dr Andrew Miller BVSc MRCVS

Written by: Dr Andrew Miller MRCVS

Andy graduated from Bristol University in 2010 and sees nutrition as a foundation for our pet's wellbeing and takes a common-sense approach. We are what we eat, and it shouldn't be any different for our pets.

Sources
  1. Zoonoses World Health Organisation
  2. Veterinary Medicines Directorate position paper on authorised vaccination schedules Veterinary Medicines Directorate
  3. Studies on canine leishmaniasis control. 1. Evolution of infection of different clinical forms of canine leishmaniasis following antimonial treatment Transactions of The Royal Society of Tropical Medicine and Hygiene, 82, (4), July 1988, 566–567, doi.org/10.1016/0035-9203(88)90510-X
  4. Parasites – About parasites Centers for Disease Control and Protection
  5. Parasites – Leishmaniasis Centers for Disease Control and Protection
  6. Parasite Biology: The Reservoir Host The Leishmaniases: Old Neglected Tropical Diseases, Jan 2018, 79-106, DOI: 10.1007/978-3-319-72386-0_4
  7. LeishVet guidelines for the practical management of canine leishmaniosis Parasites Vectors, 4, (86), May 2011, doi.org/10.1186/1756-3305-4-86
  8. Leishmaniosis in a dog with no travel history outside of the UK Vet Record, 184, (14), April 2019, 441-441, doi.org/10.1136/vr.105157
  9. Canine Leishmaniasis: An Overview of the Current Status and Strategies for Control BioMed Research International, 2018, doi.org/10.1155/2018/3296893