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Heartworm Disease in Domestic Cats

Heartworm in cat caused by Dirofilaria immitis is another vector borne helminthes infection of Zoonotic significance. The adults remain in the right ventricle, pulmonary artery and vena cava. Microfilaria can be detected in any tissue particularly blood, kidneys and lungs. Mortality due to heartworm disease is rare.

Incidence
Dirofilariasis is widespread in tropical/subtropical countries and temperate areas, which favor rapid breeding of fly population. The heartworm in cats is noticeable among the 3-6 years old ones.

Causes
Dirlofilaria immitis is a long slender roundworm measuring about 300 mm in length, which can be readily recognized in right ventricle of heart, pulmonary artery and vena cava and occasionally in lungs in heavy infections.

Microfilaria measuring about 286-349 millimicrons in length can also be identified in both dry and wet blood smears in clinically affected animals. Periodicity of microfilaria particularly at nighttime has been reported.

Transmission
The life cycle of heartworm in cat is indirect. In hot and humid climate, the disease is transmitted through bite of mosquitoes and lice where the microfilaria develops into infective stage.

Clinical Signs
No clinical have been reported during the life and the disease usually occurs as in apparent infection. Other signs include-

  • Occasional coughing
  • Asthma-like symptoms
  • Anorexia
  • Lethargy
  • Vomiting
  • Increased respiratory effort

Pathology
The parasites are generally noticed at necropsy as an incidental finding. Similarly microfilariae are also observed during routine screening of blood smears of felids having apparently normal health in endemic areas.

In heavy infection of heartworm disease, the pulmonary artery and vena cava may be occluded with parasites causing mechanical obstruction, passive hyperaemia and occasional initial damage.

Diagnosis
The disease in the domestic cats is usually detected on necropsy examination. The disease can also be diagnosed by examination of blood smears and demonstration of characteristic microfilaria. Confirmative diagnosis can be performed with the help of X-rays. The heartworm disease in domestic cats should be differentiated from Feline asthma and other pulmonary diseases.

Treatment
In endemic areas of heartworm disease, Diethyl carbamazine citrate (3mg/kg) may be tried after discussing with your vet. The effectiveness of acetarasamide for adulticidal action and levamisole and ivermectin (24 ug/kg) for antimicrobial action is yet to be assessed perfectly.

Prevention and control
Apart from vigorous fly and lice control measures, periodic treatment followed by serological monitoring and blood screening for microfilaria will be helpful in controlling heartworm in domestic cats in endemic areas.