Prevalence of canine heartworm (Dirofilaria immitis) disease in dogs of central Portugal Ana Luísa Vieira, Maria João Vieira, João Manuel Oliveira, Ana Rita Simões, Pablo Diez-Baños and Juan Gestal Parasite, 21 (2014) 5 Published online: 19 February 2014 DOI: 10.1051/parasite/2014003