Control of canine leishmaniasis
- Several species of Leishmania have been reported in dogs, the major veterinary concern is infection by Leishmania infantum/chagasi of Latin America.
- The domestic dog is the major reservoir of infection for the human population so campaigns to control canine leishmaniasis (CanL) Leishmaniasis have always been attempts to reduce the risk of infection to people rather than to solve a veterinary problem.
- No effective vaccine exists against the disease and no prophylactic drugs.
- Treatment is expensive and frequently followed by a relapse.
- The only fully successful control campaign was by the elimination of all dogs in eastern China, an outmoded strategy that is longer acceptable in that country or elsewhere.
- In Brazil, culling seropositive dogs led to a temporary fall in CanL but large scale attempts to reduce the risk of infection to the human population were abandoned because of cost and the difficulty of maintaining a low level of infection in the canine population.
- In Italy, treatment of dogs with clinical signs of infection with the pentavalent antimonial, meglumine antimoniate Meglumine antimonate reduced the prevalence of CanL. Parasites isolated from dogs with relapses displayed resistance to the drug and, as pentavalent antimonials are the drug of choice to treat human cases, this approach is not recommended.
- Current means of control are aimed at the sand fly vectors.
- There are 9 species of closely related sand flies of the subgenus Larroussius that are proven or probable vectors of CanL in Portugal and countries bordering the Mediterranean. The best known, with the widest distribution, is Phlebotomus perniciosus.
- In China, the vectors are P chinensis and P alexandri.
- In Latin America, there are two vector species:
- Lutzomyia longipalpisis found from Mexico to Argentina (but not in Chile).
- Lutzomyia evansi, is a vector of less importance with a distribution limited to parts of Colombia and Venezuela.
- In the USA, the vector of CanL has not been identified. Infection among foxhounds may be by contact but it is likely that the bite of North American sand flies (probably Lutzomyia Shannoni) is responsible for transmitting CanL.
Time of greatest risk of infection
- The biting activity of sand flies is crepuscular and nocturnal.
- In the Mediterranean Basin and western China, sand fly activity is limited to the warm months of the year with the maximum risk of infection at the end of the summer and the beginning of the autumn when the population of sand flies is composed of a comparatively high proportion of old flies that have taken one or more blood meals (and may, therefore, be infected).
- In Latin America, Lu longipalpis is active throughout the year with two peaks of the population in May – June and October – November. The most likely time of risk is as these peaks decline.
- The times of maximum risk in the USA are unknown.
Methods of control of sandflies
- Sand flies breed in moist soil containing organic matter (not in water) but few natural breeding places have been found -> control of sand flies by attacking their larvae is impractical.
- The vectors of CanL bite mainly outdoors -> house spraying is not a cost effective option.
- Spraying an insecticide in and around kennels reduces the risk of infection.
Protection of dogs against sand fly bites
Deltamethrin-impregnated collars (Scalibor®ProtectorBand, Intervet International) Deltamethrin
- Effective in killing sand flies that feed on dogs and also have a strong anti-feeding effect on the flies.
- A plastic dog collar containing a depot of a complex of deltamethrin and the excipient triphenyl phosphate that permits the insecticide to be slowly released into the lipids of the dog’s skin. It covers the complete body of the animal and, unlike conventional dog collars or applied insecticides, the deltamethrin retains its activity on the dog for many months.
- Laboratory studies have shown that Scalibor protects dogs from the bites of more than 90% of P perniciosus or Lu longipalpis for more than six months; a complete sand fly season in countries of the Mediterranean Basin.
- In a pilot field trial in southern Italy, in a focus where P perniciosus is the vector, when the force of transmission was high, the protection rate against infection was 86%.
- The preliminary results of on-going field trials in Brazil and Iran show that Scalibor is more effective in preventing the transmission of L infantum among dogs than culling seropositive individuals.
- Since the work on Scalibor, other products containing synthetic pyrethroids have been tested in the laboratory and have been shown to protect dogs from sand fly bites, but for much shorter periods than Scalibor.
Canvas dog collars impregnated with deltamethrin Deltamethrin
- Chinese workers studied canvas dog collars impregnated with deltamethrin and recorded an anti-feeding effect for no more than three months.
- A topical solution containing 65% permethrin.
- Dogs need treating monthly as less effective than the canvas collars.
- No results of field trials available.
Duowin® (Virbac S.A.)
- A spray containing 2% permethrin and 0.02% pyroproxyfene with some some anti-feeding activity.
- In combined results of experiments done on days 1, 8 and 15 days after treatment, 18/556 flies fed on untreated dogs compared with 1/572 flies fed on treated dogs.
- No recommendation on how this product should be used.
- No results of field trials available.
In an independent comparison of the anti-feeding effect of four topically applied insecticides, it was concluded that deltamethrin is the one of choice.
- The current evidence strongly suggests that Scalibor will greatly reduce the risk of CanL to individual dogs.
- Claims that Scalibor protects dogs from sand fly bites are officially recognised in France, Spain, Greece and Italy and a claim is pending in Brazil.
- At the present time (August, 2002), no other product has a similar claim.
- In southern Europe, one collar will maintain its protective effect for a complete sand fly season.
- In Latin America, the collar should be renewed every six months.
- Times of renewal of collars in the USA cannot be suggested until the vector is identified and its activity period is known. Provisionally, it is recommended that Scalibor should be worn by dogs in the Eastern States during all warm months of the year.
- CanL is also commonly diagnosed in non-endemic countries (the UK, the Netherlands, Germany, Belgium, and parts of the USA) in dogs that have been either imported from endemic areas or exposed to infection while on holiday.
- For dogs taken on holiday from non-endemic areas to places of active transmission, Scalibor should be fitted at least one week before travel to give time for the deltamethrin to spread in the lipids of the skin over the whole body of the animal.
- Palatnik-De-Sousa C B, Batista-De-Melo L M, Borja-Cabrera G P, Palatnik M, Lavor C C (2004) Improving methods for epidemiological control of canine visceral leishmaniasis based on a mathematical model. Impact on the incidence of the canine and human disease. An Acad Bras Cienc 76, 583-593.
- Reithinger R et al (2004) Are insecticide impregnated dog collars a feasible alternative to dog culling as a strategy for controlling canine visceral leishmaniasis in Brazil. Int J Parasitol 34, 55-62.
- Mazloumi Gavgani A S, Hodjati M H, Mohite H & Davies C R (2002) Effect of insecticide-impregnated dog collars on incidence of zoonotic visceral leishmaniasis in Iranian children: a matched-cluster randomised trial. 3 The Lancet 360, 374-379.
- Chen S, Li F, He J, Chen X, Wang D, Wei L, Yang H & Guan L (2001) Experimental study on prevention of dog-sand fly contact by deltamethrin collar. End Dis Bull 16 (3), 17-19. (Chinese).
- David J R, Stamm L M, Bezarra H S, Nonato Souza, R, Killick-Kendrick R & Oliveira Lima J W (2001) Deltamethrin-impregnated plastic dog collars have a potent anti-feeding effect on Lutzomyia longipalpis and Lutzomyia migonei. Mem Inst Oswaldo Cruz 96, 839-847.
- Maroli M, Mizzon V, Siragusa C, D’Orazi A & Gradoni L (2001) Evidence for an impact on the incidence of canine leishmaniasis by the mass use of deltamethrin-impregnated dog collars in southern Italy. Med Vet Entomol 15, 358-363.
- Molina R, Lohse J-M & Nieto J (2001) Evaluation of a topical solution containing 65% permethrin against the sandfly (Phlebotomus perniciosus) in dogs. Vet Ther 2, 261-267.
- Reithinger R, Teodoro U & Davies C R (2001) Topical insecticide treatments to protect dogs from sand fly vectors of leishmaniasis. Emerg Infect Dis 7, 872-876.
- Halbig P, Hodjati M H, Mazloumi-Gavagni A S, Mohite H & Davies C R (2000) Further evidence that deltamethrin-impregnated collars protect domestic dogs from sandfly bites. Med Vet Entomol 14, 223-226.
- Killick-Kendrick R, Killick-Kendrick M, Focheux M C, Dereure J, Puech M P & Cadiergues M C (1997) Protection of dogs from bites of phlebotomine sandflies by Scalibor ProtectorBands for control of canine leishmaniasis. Med Vet Entomol 11, 105-111.
Other sources of information
- Killick-Kendrick R & Watson T (Eds) (2002) Proceedings of the 2nd International Forum on Canine Leishmaniasis, Seville, 6-9 February, 2002. Boxmeer: Intervet International.
- Ascher F, Alves-Pires C, Campos C, Capela M J & Aguiar P (1997) Effet protecteur d’un spray insecticide contre Phlebotomus perniciosus vecteur de leishmaniose. In: Conférence Nationale des Vétérinaires Specialisés en Petits Animaux (CNVSPA), Paris, November 1997,3pp.