What is leishmaniasis?
Holidays at last! However, the joyful anticipation of long walks on the beach and mild summer nights will soon turn to panic if dog owners encounter the dreaded leishmaniasis for the first time. Transmitted by mosquitoes, this often fatal infectious disease is one of the most well-known tropical diseases that affect dogs. Since the sandflies that transmit leishmania pathogens prefer warmer climates, the disease mainly prevails south of the 45th parallel. Dogs from more northerly regions can be affected by this disease too though, for instance, if they travelled south for family holidays or have been imported from animal protection organisations based there. For dogs, at least two months or often even several years pass after a leishmaniasis infection until the illness breaks out.
How is leishmaniasis transmitted?
Leishmania pathogens, named after the Scottish tropical doctor William Boog Leishman, are single-celled parasites in the blood. They are generally transmitted through the sting of the sandfly, which infects dogs with dangerous leishmania by sucking their blood. However, transmission through a blood transfusion or contact with an infected dog cannot be ruled out. In the latter case though, this is only possible if the dog already has an open skin lesion that comes into direct contact with sores or fistulae on affected dogs. After the infection, leishmania bed themselves into the tissue cells (macrophages/scavenger cells), where they multiply and little by little attack the animal's lymph nodes, spleen, bone marrow, liver and other organs.
Effects of climate change
In Europe, the sandflies that spread leishmania are mainly found in the Mediterranean. Hence, the risk of being bitten by a carrier is higher in the South of France, Spain, Portugal, Italy, Croatia, Greece and Turkey than in other colder parts of the continent. However, sandflies could spread to hitherto untypical regions as part of climate change. As a result, a leishmaniasis infection is possible outside of these particular holiday regions, although it is comparatively rare. Along with the Mediterranean in Europe, sandflies have also migrated to parts of South America, Mexico, Southeast Asia and Africa.
Can I protect my dog from leishmaniasis?
Due to the increasing dispersal of sandflies, it's not very helpful to advise dog owners to stay away from countries with a high risk of leishmaniasis. Anyway, who wants to miss out on their well-deserved holiday in the warmth of the Mediterranean? Instead, it's recommended to reduce the chance of your dog getting bitten in order to protect it from leishmaniasis. If you take your dog on holiday with you to southern Europe, you can make it wear a protective collar, for instance. This secretes a distinct odour that repels flies, fleas and ticks. There are also insecticides for dogs that have a similar effect to mosquito repellent. The hairless base of the nose, eyelids and stomach or genitals for young dogs are particularly appealing to sandflies and should be sprayed thoroughly.
How you can prevent your dog from getting bitten by a sandfly
Since sandflies react to yellowy-orange light (predominantly generated by conventional lightbulbs), it's best to cover windows and doors with mosquito nets. Also bear in mind that mosquitoes are nocturnal and need several (undisturbed) minutes to suck the blood. Hence, they mainly bite their victims at night whilst they are sleeping. As an alternative to finely woven fly screens on windows and doors, you can also just use a mosquito net to protect the area where your dog sleeps. It's best if dogs stay indoors during the active phase of mosquitoes (from the onset of darkness to sunrise). If they do have to go outside, go for walks in windy areas, for instance, on the beach. Sandflies are highly sensitive to wind and predominantly stick to protected lanes of houses or woods and swampland.
Is there a vaccine against leishmaniasis?
There is no vaccine that hinders exposure to leishmania pathogens. However, a Europe-wide vaccine called CaniLeish® that significantly reduces the risk of an active infection and suffering from leishmaniasis has been permitted since 2011. This is a so-called adjuvanated vaccine that bolsters the immune system in fighting leishmania with the help of proteins with parasite characteristics and an additive (adjuvant). The danger of your dog actively suffering from leishmaniasis with possibly fatal consequences can be prevented with this new vaccine in approximately 90% of cases.
Vaccination scheme and precautionary measures
In principle, all healthy dogs can be vaccinated from the age of six months. Before the vaccine is administered, however, you must ensure that there is no hitherto undiscovered leishmaniasis infection. If the results of the blood test are negative, the first injection can go ahead. The injection will be repeated twice more in three-week intervals. From this point onwards, an annual booster is sufficient to keep it effective. The side-effects of the leishmaniasis vaccine are comparable to those of typical immunisations. For instance, local reactions around the injection site could flare up, such as swelling, redness or hardening, though they generally subside after two days. Temporary reactions such as fever, pain or weariness are also possible due to the foreign proteins in the vaccine.
Should I get my dog vaccinated against leishmaniasis?
A “Leishmania infatum” vaccine certainly makes sense for dogs whose owners spend a lot of time in areas frequented by sandflies. Studies have shown that 93% of vaccinated dogs get through a leishmaniasis infection without showing any symptoms. The high efficacy and comparatively minor side-effects are definite factors in favour of the vaccination. However, you should of course be certain beforehand that your dog is in good state of health and able to tolerate the vaccination. Take your vet's advice on whether the vaccination is recommended in your case. You should make use of the previously cited preventive measures such as a protective collar and mosquito net above the area where your dog sleeps despite the vaccination. After all, this “only” works by actually fighting leishmaniasis and cannot prevent infection from the mosquitoes that transmit the disease.
How do I recognise if my dog already has leishmaniasis?
What's deceitful about leishmaniasis is that it often only breaks out years after the infectious mosquito bite has taken place. Holidays in hot southern destinations are long forgotten for many dog owners before the first signs of leishmaniasis emerge. However, both the long incubation time and the global multitude of leishmaniasis infantum strains with different forms and disease patterns ensure that the symptoms are often not at all traced back to a leishmaniasis infection or only very late on.
If you observe that your dog is showing the following signs and your vet has ruled out other diseases as a cause, you should ask them to carry out a blood test and take a tissue sample to be on the safe side. This is the only way to prove the presence of leishmania and get a certain diagnosis.
Signs of leishmaniasis:
- Diarrhoea/loss of appetite/fever
(mainly intermittently at the start)
- Weight loss
- Changes to the fur and skin
- Open skin wounds that do not heal
- Skin rashes on the bridge of the nose, tips of the ears and around the eyes (large, white, greasy scales, though not itchy)
- Hair loss
- Ocular diseases
- Swollen lymph nodes
- Sensitive stomach
- Bloody stools
- Excessive claw growth
What are the treatment possibilities after diagnosis?
The same applies for leishmaniasis as for many other diseases: the earlier it is recognised, the better the chances of recovery. As soon as you spot changes in your dog or one of the aforementioned symptoms, you should immediately seek out veterinary attention. If untreated, leishmaniasis can result in death within 12 months (mostly due to kidney failure). In addition, dogs suffering from the illness often have open wounds and can affect both humans and other animals. Children under the age of 2 or people with a weak immune system are particularly vulnerable.
If your vet has diagnosed leishmaniasis and backed this up with blood and tissue samples, treatment should commence as soon as possible. Treatment mainly focuses on alleviating the symptoms by strengthening the body's own defence system or by inhibiting the development of the pathogens. Unfortunately no medication available so far can fully cure leishmaniasis. Lifelong treatment with the required substances is generally inevitable and can lead to high costs. Sadly the many side-effects that medicinal treatment can bring are also unavoidable.
The currently most well-known medications to treat leishmaniasis and its most common side-effects are the following:
|Substance to tackle leishmaniasis
||Most common side-effects
||Gastrointestinal complaints, painful swelling around the bitten area
||Kidney stones (urolithiasis)
Treatment with the amphotericin B, aminosidine and antifungal antibiotics are the only options left for vets should the dog resist the substances listed above. The vet will often suggest altering the diet, with a low-protein diet food recommended for treatment with allopurinol.
Life with leishmaniasis
Despite these difficulties, a dog suffering from leishmaniasis can live a long life – provided that the disease is recognised and treated at an early stage. If you frequently spend time in at-risk areas, you're best getting your dog regularly tested for leishmania pathogens and their antibodies. This can diagnose the infection before it actively erupts when the organs are still unaffected. In this case, the symptoms can be alleviated extremely well by medication, which can prevent the pathogens from spreading further.