Filarial Periodicity in the Dog Heartworm,Dirofilaria Immitis,After Blood Transfusion

Abstract

Lane 1 ,² believes that the mechanism of filarial periodicity in filariasis bancrofti in man is due to a simultaneous daily parturition of the females, involving the destruction daily of as many microfilariae as are produced. O'Connor 3 ,⁴ has found histological evidence to support Lane's hypothesis, and concludes that this occurs about midday in Puerto Rico. On the other hand, Low and Manson-Bahr 5 criticize the theory, because of the effects of absorption of these millions of dead microfilariae in the body, and because microfilariae have been kept alive outside the host for a week. Murgatroyd, 6 however, injected citrated blood containing 720,000 microfilariae into a human volunteer 2 hours after withdrawing the donor's blood, but never recovered microfilariae from the recipient's blood. Rao 7 kept microfilariae alive in vitro at 4°C. under aseptic conditions for 4 to 6 weeks. He concludes from collateral evidence that the duration of the life of the embryos in the human body is about 70 days.

Dirofilaria immitis is an infection of the dog, the adult worms occurring chiefly in the right ventricle and pulmonary arteries and their microfilariae exhibiting a nocturnal periodicity, although not so marked as in Wuchereria bancrofti. Fülleborn 8 injected 6.25 cc. of blood, containing approximately 450,000 microfilariae, from an infected dog into a young puppy. These microfilariae persisted in the blood of the recipient for 9 months but showed no periodicity and were present in only about one-third of the expected number. He believed that the majority of the larvae withdrew to the lungs and only a fraction got into the circulation. Unfortunately the possibility of natural infection by mosquitoes or via the placenta of the mother was not entirely excluded.