by Dr Bob Killick-Kendrick PhD, DSc, FIBiol
Reading the many articles on the dangers of British dogs catching leishmaniasis when they are on a Mediterranean holiday, I can imagine dozens of owners rushing to their telephones to cancel plans for holidays with their dogs. But it is not quite as bad as it seems, there are ways the risk can be minimised. After all, there are lots of healthy dogs all round the Mediterranean. In France, where I now live, there are more dogs per head of the population than in the UK. This is in spite of the fact that leishmaniasis is common in many places. So what exactly causes canine leishmaniasis, how does a dog get infected and what can dog owners do to protect their pets?
The cause is a microscopic parasite that lives inside cells of the blood and internal organs. There are many species of these parasites all classified under the name Leishmania (after a famous Scottish doctor - Sir William Leishman - who discovered a species which causes epidemics in people in India). Most of these parasites have evolved in wild animals. They are generally pretty well adapted to these hosts and dont cause them any trouble. But if they get into the wrong host - like our dog- they can be dangerous. All of them are transmitted by the females of small blood sucking insects - sand flies - that first pick up an infection by feeding on an animal carrying the parasite. Like mosquitoes, sand flies need the protein in the blood to make eggs. In the stomach of the fly, the parasites keep dividing until they fill all the available space. Then, when the female takes another blood meal, she deposits some of the parasites into the skin of the unlucky individual and the cycle is completed. But many dogs bitten by an infected sand fly never get clinical leishmaniasis: they are able to control the parasite with their immune system. This depends on their genes and many vets think some breeds are more likely to get the disease than others.
To give the full picture, I ought to say something about sand flies. They are small two-winged insects - about 3mm long - that breed in damp soil rich in organic material. They are active from dusk to dawn and you can be bitten without knowing the culprit. You dont hear them when they come to bite and its quite likely you wont know what caused the itchy spot the next day. If you do see one, its easy to know it is a sand fly. They hold their wings up above the body, they are hairy, and they hop around as they are making up their minds where to bite. Leishmaniasis is not endemic where there are no sand flies. One species of Leishmania (L.infanta) infects dogs in countries bordering the Mediterranean, plus Portugal, many Latin American countries, parts of the USA, West Africa, Sudan, much of the Middle East, Central Asia and western China. British dog owners are, of course, more likely to take their pets to southern Europe than the more exotic places, so the rest of this article concerns transmission only around the Mediterranean and in Portugal.
Of course, if you take your dog to a place where there are no sand flies at all, theres no problem. But some popular holiday places are dangerous. In Portugal, there are hot spots in the Lisbon Metropolitan Region, the Evora district and Alijo, Alto-Douro. In Spain, the south is particularly risky, especially Salamanca, Granada, Jaen, Valencia, Murcia, Catalonia, the Northern Madrid area and the islands of Mallorca and Ibiza. In France, the most popular country for British holiday makers, your dog should be safe in a strip along the north (Brittany, Normandy and Picardy) and another down the eastern border north of Provence (Ardennes, Champagne, Lorraine and Franche-Comte); other parts of France are more or less dangerous. Most of Italy, all of Greece, and the islands of Cyprus, Malta, Gozo, Sicily, Sardinia and Corsica are risky.
But do not despair! It is safe to take your dog anywhere in southern Europe from the end of October to May when sand flies are hibernating as larvae in damp soil. Up to the end of May theres no real risk but, as summer gets into full swing, the chances of being bitten by an infected sand fly increase until late August and into September which is the time of greatest danger. All right! You dont want to go on holiday from October to May; you want to go when theres lots of sunshine. Theres no magic pill or vaccine yet on the market to protect your dog from leishmaniasis. But there are ways you can reduce the danger to about the same level as having a fatal accident while driving from the English Channel port to the Mediterranean on French roads.
The best protection for dogs against sand fly bites is a plastic collar called Scalibor which is marketed in two sizes. Scalibor is a depot of the insecticide deltamethrin. This is insoluble in water (so dogs can swim while wearing the collar) but is soluble in the oils of the dogs skin. Friction between the collar and the neck of the dog releases tiny amounts of deltamethrin which are absorbed by the oils and spread over the body of the dog. Complete cover takes about 10-14 days. Scientific studies in France, Spain, Brazil and Iran have shown that Scalibor will protect a dog from well over 90% of sand fly bites for more than six months. In southern Europe thats a complete sand fly season. Field studies in Italy and elsewhere have shown dogs wearing Scalibor are very much less likely to catch leishmaniasis than dogs without the collar. One problem is that if you shampoo your dog, with a detergent shampoo, some of the skin oils are removed and, after Scalibor is replaced, it will take a few before the maximum level of protection is regained. But the manufacturers thought of that and are now beginning to market a Scalibor shampoo with enough deltamethrin in it to keep up the protection. The collar gives dog owners a bonus: its also very good for protecting dogs from tick bites. And it is environmentally friendly because it targets only insects and ticks coming to bite a dog.
How do you know that, while sunbathing on the beach, your dog wont be bitten by a Leishmania-carrying sand fly? I can answer that question. Your dog wont be bitten dog while youre getting sunburned because there arent any sand flies on the beach. It is not their habitat. Dont be misled by the name: many species are a sort of sandy colour and some live in sandy deserts but they have nothing to do with beaches. And if they were on the beach, they wouldnt bite your dog while youre sunbathing. They hate the heat and, during the day, they are tucked away in cool moist resting places like cellars or cracks in walls and they dont come out to attack until twilight. Sand flies of southern Europe begin biting as the sun goes down and carry on until dawn. Interestingly most of them bite outdoors, not inside houses, so its a good idea to keep your dog indoors from dusk to dawn.
At the time of going to press OUR DOGS has received information from an official source that the Scalibor collar has been authorised in the UK which means that it should be available from veterinary surgeons. Because the availability of the collar is at its early stage it may be necessary for the vets to pressurise their pharmaceutical suppliers to obtain supplies but if enough travellers demand the product it should be forthcoming.
If your dog is going on holiday to a place in southern Europe where there is leishmaniasis, order a collar in plenty of time, put it on your pet two weeks before he sets a paw on the Continental mainland. This will reduce the risk to an acceptable level; but nobody can guarantee 100% protection against any disease. A UK dog owner must realise that, if a dog has been in a leishmaniasis endemic area in the summer, even if it was wearing Scalibor, there is a very faint possibility that the pet could have become infected. The time from a sand fly bite to the first clinical signs of leishmaniasis is usually around four to seven months but can occasionally be longer. Common early signs are loss of hair, especially round the eyes, skin sores, and loss of weight, but even experienced vets often find it difficult to diagnose canine leishmaniasis simply by a clinical examination. If a dog falls ill during the year after its return to the UK, it should be taken to a vet with a request for a blood test to check for leishmaniasis. This can be done in the Veterinary Faculty of Liverpool University.
If your vet doesnt know what youre talking about (he has probably never seen a case), suggest he looks at the website www.leishmaniasis.info where he will find all he needs to know about the clinical signs of canine leishmaniasis, how to make the diagnosis and how to treat his patient. There are also answers to the questions most frequently asked by dog owners.
Bob Killick-Kendrick PhD, DSc. FIBiol is an eminent parisitologist who has studied Canine Leishmaniasis for thirty based at Imperial College, London where he is Senior Research Investigator. He is also on the World Health Organisation expert panel on Canine Leishmaniasis an is a consultant to Intervet International which is responsible for developing the Scalibor collar