Changing distribution patterns of canine vector borne diseases in Italy: leishmaniosis vs. dirofilariosis

Abstract

Ecological and climatic changes, human and animal population dynamics are among the several factors that have favoured the spread or the (re)introduction and establishment of "novel" vector species and pathogens they transmit in previously disease-free geographical areas. As key examples of the changing pattern of distribution of canine vector borne diseases (CVBDs), the current distribution of canine leishmaniosis (CanL) by Leishmania infantum and dirofilariosis by Dirofilaria immitis causing heart worm disease (HW) in Italy is discussed on the basis of retrospective historical reports until the 90's and later on until 2009. For long time, D. immitis has been considered mainly present along the Po River Valley and northward areas, while L. infantum in south-central Italy and Sicily and Sardinia. Comparison of current available and historical data (up to 1989) confirms that HW and CanL, although with different prevalence rates, have been changing their distribution patterns in Italy as a result of many biological and ecological factors, including those related to vector distribution and introduction of new species (e.g. the Asian tiger mosquito Aedes albopictus, a competent vector of D. immitis). New autochthonous foci of HW in southern Italy (i.e. Apulia and Calabria regions) have recently been reported.Although analysing retrospective data may represent a difficult task, the "paradigm" about the dual distribution of HW and CanL in northern and southern Italy cannot yet be considered valid. The research needs for managing HW and CanL in previously uninfected areas are discussed.

Figure 1

Adult Dirofilaria immitis in the heart of a dog. Dirofilaria immitis adult worms at the dissection of a heart of a dog.

Figure 2

Dog showing severe clinical signs of leishmaniosis. A dog from southern Italy positive for Leishmania infantum both at the parasitological and serological tests presenting poor general conditions.

Figure 3

Current distribution of Dirofilaria immitis in Italy. Foci of canine dirofilariosis by Dirofilaria immitis until the 1990s in the endemic area of the Po Valley (blue dots) and outside the endemic area (blue pushpin). New foci (red pushpin) reported in non-endemic areas after the 1990s until 2009.

Figure 4

Current distribution of Leishmania infantum in Italy before and after 1989. Foci of canine leishmaniosis until the 1990s (yellow pushpin) in endemic regions of central and southern Italy (no autochthonous cases in northern regions were reported). New foci (red pushpin) in non-endemic areas after the 1990s until 2009 based on the report of autochthonous infected dogs and concomitant presence of competent sandflies.