DIROFILARIASIS (Heartworm)

Heartworm disease is caused by the filarial nematode Dirofilaria immitis.  D. immitis has a wide distribution and is endemic in many areas of Europe, USA, Canada and Australia.  The adult worms may exceed 20 cm in length and live in the right side of the heart and the pulmonary arteries, resulting in clinical signs of coughing, dyspnoea, reduced exercise tolerance and right-sided heart failure. The severity of the disease is partially dependant on the number of worms present and the duration of the infection.  D. immitis is zoonotic but human infection is rare.  The adult worms release microfilariae (L₁) into the circulation which are picked up by mosquitoes (of several species).  Development occurs inside the mosquitoes which then transmit L₃ larvae when feeding. These larvae take 5 - 6 months to develop therefore there is often a long period between infection and clinical illness developing. Antigen tests will be negative until adult worms are present.  Prophylactic treatment with selamectin ('Stronghold') or milbemycin ('Program Plus', "Milbemax") will prevent infection and is strongly recommended if animals travel to endemic areas.  Cats can be infected and develop clinical signs but usually have few worms and circulating microfilariae are rare. 

D.immitis L1

D. immitis antigen test detects the secretory antigen of the female adult worms.  Results are reported as positive or negative with reference to the test control.  

Sample        0.5ml serum/whole (EDTA) or clotted blood

Detection of circulating microfilariae can accompany serological tests.  This can be done by direct examination of the blood for microfilariae in addition to a concentration and staining technique to differentiate from non-pathogenic filarial worms.

Sample        0.5ml whole blood (EDTA)