Dirofilaria immitis
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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") or moxidectin (“Advocate”) will prevent infection and is strongly recommended if animals travel to endemic areas. If dogs are confirmed to be infected, specialist advice should be sought. The drugs effective for prophylaxis (selamectin, milbemycin, and moxidectin) are not effective to eliminate adult infections. Cats can be infected and develop clinical signs but usually have few worms and circulating microfilariae are rare. This infection is not yet endemic in Britain, but imported dogs may have acquired infection abroad.
Dirofilaria testing at TEST-A-PET
Antigen Test
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 required: 0.5ml serum.
Results are available within one working day of us receiving the sample.
Parasite Detection
Detection of circulating microfilariae can accompany serological tests. This can be done by direct examination of the blood for microfilariae and a concentration technique.
Sample required: 1ml whole blood (EDTA).
Results are available within one working day of us receiving the sample.
A staining technique (for acid phosphatase activity) can also be done to differentiate from non-pathogenic filarial worms.
Sample required: 0.5ml whole blood (EDTA).
Results are available within two working days of us receiving the sample.
Links
For details on submitting samples for Dirofilaria immitis testing, please click here.
For further advice on diagnosis and treatment, please click here.
For further reading on dirofilariasis, please click here.
For maps showing the distribution of the major vector-borne parasitic infections of dogs and cats in Europe including Dirofilaria immitis, please click here.
