As the name shows this illness is produced by a parasite which lives in the heart or major vessels of dogs .A study on “Heartworm in dogs in Canada in 2010” published by the Ontario Veterinary College’s Department of Pathobiology at the University of Guelph has revealed that 60 per cent increase in the number of dogs in Ontario with heartworm since the last study of its kind was conducted in 2002.
Female mosquitoes act as the intermediate host for the stage 1 of the cycle of larvae.Mosquitoes are infected when feed blood from infected dogs.The life cycle of this parasite (Dirofilaria immitis) takes at least six months after infection for the symptoms to become apparent.In this period of time 3 stages of life cycle of larvae are done in the mosquitoes bodies and finally by biting, L3 is transmitted to dogs .After about 100 days
L5 enters the pulmonary artery and it releases L1 into the bloodstream.Now the dog has been so infected that can be a source of the L1 and this cycle can be repeated if a mosquito bites that dog.
Cats appear to be more resistant to heartworm disease but can be infected.
Heart failure causes clinical signs including: fever,coughing,difficulty in respiration,increased heart rate,bleeding from respiratory system and pale mucous membranes and finally death.
Unfortunately treatment in advanced stage of disease is very difficult and expensive .Any way therapy includes cage rest, corticosteroids, supplemental oxygen,heparin and spacial drugs which can kill larvaes and even surgery.
Prevention is based on the heartworm test on the blood.In this lab test Ag or Ab is recognized in the serum.If the test is positive treatment has to be done and if this dog has had annual test,the disease is in the early stage and can be treated easily.If test is negative, prevention can be done by using special medication : chewable tablet like Heartguard or liquid form.