This article follows the article in VT46.14, which discussed the chemotherapeutic approaches and vaccinations used to control canine leishmaniosis (CanL).

This part looks at control using repellents, as well as other means of sandfly control.

Topical fly repellents

Preventing sandfly bites protects dogs from CanL and reduces the risk of human infection.

Several directly applied, long-acting pyrethroid insecticides, with a repellent or anti-feeding effect to prevent sandflies from taking a blood meal (Figure 1), are available as spray, spot-on or collar formulations to protect dogs. They are commonly used for CanL prevention in Europe (Solano-Gallego et al, 2011; Brianti et al, 2014).

The following products have proven effective against sandflies with protection exceeding 80%, the minimum threshold considered by the registration agencies:

• Spot-on permethrin and imidacloprid formulations provide repellent activity against sandflies for up to three weeks and can be reapplied every three weeks throughout the exposure period (Miró et al, 2007).
• Deltamethrin-impregnated collars control sandfly feeding and are commonly used in Europe to prevent CanL (Maroli et al, 2010). Deltamethrin absorbs slowly into the animal’s skin, where it covers the dog and remains active for five months to six months. Deltamethrin has a potent anti-feeding and insecticidal effect against sandflies (Killick-Kendrick et al, 1997).
• Permethrin alone reported efficacy greater than 93.4% until day 8, then 86.8, 67.6 and 61% on days 15, 22 and 29, respectively (Molina et al, 2012). It repels sandflies for up to three weeks and can be reapplied every three weeks.
• A topical combination of dinotefuran, permethrin and pyriproxyfen showed an immediate repellent effect against sandfly Phlebotomus perniciosus and lasts four weeks. Application can be repeated every three to four weeks.
• A spray of permethrin and pyriproxyfen has been shown to have 71.4% repellent effect against sandfly bites after 21 days; however, its insecticidal effect was only 7.2% (Molina et al, 2006).
• A monthly topical application of new ectoparasiticide combination permethrin and fipronil has shown to be an effective control against P perniciosus in dogs, with a repellency/inhibition of feeding efficacy close to, or better than, the one obtained with other commercial spot-on formulations (Franc et al, 2015).
• A single topical administration of fipronil and permethrin demonstrated a significant and immediate repellent effect against P perniciosus and lasted for four weeks after application. The repellent effect was accompanied by a significant insecticidal effect on sandflies (Dumont et al, 2015).

Spot-on formulations should be applied at least two days prior to exposure, to ensure animals are protected. Collars should be applied for at least one week to two weeks before travelling to endemic areas, or at the beginning of the vector season for dogs living in endemic regions, to ensure enough time for the insecticide to be absorbed and distributed over the dog’s skin.

Products containing permethrin must not be used on cats or on dogs that cohabit with a cat.

Vector control

The basic goal of any vector control programme is to interrupt the parasite life cycle (Figure 2) and thus control the disease.

Mass vector killing, carried out for some vector-borne diseases, is not a practical control measure for sandflies as they tend to inhabit focal areas rather than have a widespread distribution (Gálvez et al, 2010) and breeding sites remain largely unknown.

Also, the sandfly season in endemic areas may vary from year to year and from region to region.

Two environmental control measures are used in Asian and Latin American countries to prevent human leishmaniosis (house spraying and bed nets treated with pyrethroids), but these are not applicable control measures for CanL.

Other measures to reduce disease transmission include:

• Keeping dogs indoors overnight throughout the whole risk season (April to November), especially during dusk and dawn when the vector flies are feeding.
• Avoiding dim, humid areas rich in organic matter because these may be favoured sandfly microhabitats.
• Using insecticidal room sprays, protective nets in windows and doors (mesh 0.3mm² to 0.4mm²).

These measures can dramatically reduce phlebotome populations.

Some control strategies used in the past, such as the culling of seropositive dogs in endemic areas, have not been successful in reducing Leishmania transmission.

Prevention of sandfly bites using repellents/insecticides, in the form of impregnated collars, sprays and spot-on preparations, is the most promising strategy.

Travelling with dogs to endemic areas

Despite the availability of preventive methods, the potential of Leishmania infantum spreading via dogs to non-endemic European countries where a competent sandfly vector exists is high – especially with the open nature of travelling within the EU. Thus, efforts should be made to prevent further dissemination of CanL to non-endemic regions.

Dogs imported from endemic areas (for welfare or commercial reasons) should be tested for infection by sensitive methods, such as serology and PCR, before their exportation and the positive animals may not be allowed to enter non-endemic countries (Solano-Gallego et al, 2009).

Since no test is 100% sensitive, additional measures aimed at reducing the risk of infection in dogs from endemic areas (repellents, vaccination and/or domperidone) are required for dogs that will be imported into non-endemic areas (Mattin et al, 2013). Vaccination of all dogs travelling to endemic regions has also been recommended.

Furthermore, because Leishmania infections are known to have a long incubation period, practitioners should inform the owners of imported dogs to retest their pets for Leishmania for at least two years after importation or in case of a clinical suspicion (Paltrinieri et al, 2010).

Killing sick or seropositive dogs is unacceptable and ineffective in controlling the spread of the disease because subclinically infected dogs and other wild canids represent additional sources of parasite transmission. More information about this is available at www.leishvet.info and www.esccap.org

Conclusions

Veterinary practitioners should keep abreast of the clinical advances in the diagnosis, treatment and prevention of CanL, and remain aware of the increasing probability of dealing with more clinical cases in the near future.

No licensed treatment exists for CanL in the UK; however, various preventive strategies exist, including the avoidance of sandfly bites via environmental measures and the use of insecticides, oral solution to boost immune response or the licensed CaniLeish vaccination.

The availability of CaniLeish in Europe, with a range of effective insecticides with a repellent or anti-feeding effect, should allow us to overcome the considerable challenges inherent in treating and managing CanL, via the development of an integrated programme that can protect against new infection and disease progression in animals living in, or travelling to, endemic areas.

Ultimately, developing new vaccine strategies, or improving on the existing vaccine, may prove to have the most significant impact, with the promise of truly limiting or eliminating CanL manifestations.

Competing interests

The author declares he has no competing interests associated with this publication. The mention of drugs is solely for the purpose of specific information and does not imply recommendation or endorsement. Readers are advised to check the most up-to-date product information provided by the manufacturer of each drug to verify the recommended dose, the method and duration of administration and adverse effects.

Acknowledgements

Because of space limitation, the author notes he was unable to comprehensively cite many worthy contributions to the field.

The author thanks Hind Mamdowh for her contribution to the artwork in this article.

Leishmaniosis in canines: part 1 – treating and controlling infection