A Vets Insight

in Animals & Pets

Heartworm is this a problem you should be worrying about?

Heartworm is a disease of dogs and cats, it rarely causes illness in cats but can be a significant problem in canines.
Is it endemic in Gibraltar? 

Cases of heartworm are few and far between , therefore it is not a disease that is endemic in our local pet population but there are sporadic cases. The cases that I see tend to be cases in animals that have travelled and have spent time in regions in Spain where the disease is prevalent.

Heartworm, Dirofilariaimmitis, is a parasite where the adults live in the right ventricle and pulmonary arteries of the heart. The female worm once fertilised releases its offspring, tiny juvenile worms, microfilariae into the blood stream. These microfilariae circulate around the body where they reach peripheral capillaries under the skin. They can circulate in the blood for up to 2 years.

Mosquitoes that may happen to feed on the animal will take on this parasite along with the blood that it imbibes. Once in the mosquito the parasite goes through a development phase before migrating to the mosquito’s salivary glands. This development can only occur when the ambient temperature is over 14 degrees centigrade. Once the mosquito is carrying the microfilariae it will infect any further dog or cat that it feeds on. When an animal is infected the microfilariae migrate to the muscles where they go through another phase of their development before finally entering the circulatory system to reach their final destination, the pulmonary artery and right ventricles. The final development stage into an adult occurs here with females measuring up to 30 cm in length. The whole process of infection to fertile adults in the heart, the pre-patent period, is between six and seven months.

Diagnosis of this disease is a fairly simple affair; historically it could only be diagnosed by taking a blood sample from a peripheral blood vessel and then examining the sample microscopically. This method unfortunately can lead to a lot of false negatives for many reasons so we do not rely on this method now. Blood samples are now tested directly for parasite antigen and/or antibody and these tests are extremely reliable.

Heartworm can be a fatal disease with dogs presenting with clinical signs of congestive heart failure. However the symptoms might be varied, weight loss, anaemia, weakness, anorexia, ascites(fluid in the abdomen).

In cats symptoms might be more subtle, asthma type symptoms, weight loss , but often the only symptom is sudden death/ collapse.

With advances in medicine there are various safe alternatives now to treat this illness with a complete resolution of the disease. As long as the illness is diagnosed early enough. 

There are various alternatives to prevent the illness too. My preferred method is to prevent the mosquito from infecting your pet in the first place; there are some really effective parasitic treatments to do this. Personally I do not like the vaccination against heartworm , it has been reported to cause severe anaphylaxis and death in some cases. There are a number of effective preventative treatments , most of them combine to treat other parasites too. 

In summary, in the summer keep your animals protected with one of the many parasite treatments that are available and if by any chance you feel that your animal may have been exposed then get your pet tested. However as Sergeant Wilson used to say , ‘Don’t Panic’!

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