An epidemiological study of canine filarioses in north-west Italy: what has changed in 25 years?

A field survey aimed at updating knowledge of the distribution and prevalence of filarial infections in the Piedmont region was undertaken. Blood samples were collected from 2628 dogs (10-15 dogs/100 km2) which had remained in the local area, were kept in the open overnight, were more than 2 years old and had not previously been treated with microfilaricidal drugs. Infection was diagnosed by a modified Knott test. Comparison of the results with those from a similar survey carried out 25 years ago showed a 3-fold increase in the size of the endemic area, with the colonization of new habitats, and a 4-fold increase in the prevalence of Dirofilaria immitis infection.