Canine filariasis in Salamanca (northwest Spain).

A survey of dogs in four areas of Salamanca province (northwest Spain) was carried out to determine the prevalence of filariids in the canine population. Blood samples from 293 dogs were tested for the presence of microfilariae, using a modification of the Knott technique. For correct identification of filariid species, blood smears associated with the 43 positive Knott tests were histochemically stained for demonstration of the somatic distribution of acid phosphatase activity. The survey revealed the presence in the northwest of Spain of Dirofilaria immitis, D. repens and Dipetalonema reconditum, with an overall prevalence in Salamanca of 12.3%, 0.3% and 2.1% respectively. The greater prevalence of canine heartworm was found in the irrigated area, where 33.3% of the dogs harboured microfilariae. The relationship between the prevalence of D. immitis and mosquito populations, and the influence of host sex and age in this infection, are analysed.