to controlE. multilocularisinfection in wild red foxes have been undertaken in
Germany (Tackmann et al. 2001 ), Switzerland (Hegglin et al. 2003 ) and Japan
(Inoue et al. 2007 ); the long term success of these campaigns will likely depend on
the continued implementation of baiting programmes and its cost effectiveness.
2.2.3 Heartworm
The mosquito-transmitted filarial nematode,Dirofilaria immitis,is a major cause of
canine and feline disease in the USA, Africa, Australia, Japan and southern Europe.
In Europe, heartworm is most prevalent in Spain, Portugal, South of France and
Greece with the largest endemic area being located along the Po River Valley in
northern Italy, where more than 50% of untreated dogs test positive for heartworm
infection (Genchi et al. 2005 ). It is believed that climate change and the greater
freedom of pet movement across European countries may increase the spread of
arthropod-born filarial infections, including heartworm. Parasitic worms reside in
the pulmonary arteries and sometimes in the right ventricle. Clinical signs can range
from none to sudden death. Signs of right ventricular heart failure, occurring in
heartworm-infected dogs, include coughing, reluctance to move or exercise, fatigue
after moderate exercise, reduced appetite and weight loss (American Heartworm
Society,www.heartwormsociety.org). Clinical manifestations of heartworm dis-
ease in cats are variable. Heartworm-infected cats may undergo spontaneous self-
cure without clinical signs, but they may also suddenly show dramatic and acute
symptoms. Sudden death in apparently healthy cats is not a rare event (Venco et al.
2008 ).D. immitisand the subcutaneous filarial nematodeDirofilaria repenshave a
zoonotic potential. The public health significance ofD. immitisis not attributable to
the overt signs of clinical disease in humans but rather to the severity of disease that
the radiographic findings of a pulmonary coin lesion (solitary pulmonary nodule)
suggest might be present (Theis 2005 ). Differential diagnosis includes primary or
metastatic neoplasia, fungal infections, hamartomas (benign lung tumours), and
tuberculosis. This lesion requires an extensive clinical work-up, which, not infre-
quently, culminates in a thoracotomy (Theis 2005 ).
InD. immitis-endemic areas, monthly administration of heartworm preventa-
tives to dogs and cats throughout the high risk season is recommended (McCall
2005 ). The advent of the MLs – ivermectin, milbemycin oxime, moxidectin and
selamectin – transformed heartworm chemoprophylaxis, introducing a new era of
potent filaricidal activity, convenience afforded by long duration of action and
choice of delivery route (oral, spot on and slow release injectable formulations).
Combined control of flea infestations, heartworm and gastro-intestinal nematodes is
another advance in companion animal parasite control, which has been achieved
through the development of endectocide drugs (selamectin) or drug combinations
(moxidectin + imidacloprid, milbemycin oximeþlufenuron). Experimental ther-
apy targetingWolbachia,the bacterial endosymbiont, which is essential to filarial
survival, is currently under evaluation (McCall et al. 2008 ).
Population Medicine and Control of Epidemics 121