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A Contribution to the Study of Fijian Haematozoa With Descriptions of a New Species from Each of the Genera Haemogregarina and Microfilaria

Dirofilaria immitis (Leidy, 1856) — (Text-figure 2, Fig. 2)

Dirofilaria immitis (Leidy, 1856)
(Text-figure 2, Fig. 2)

Dirofilaria immitis is widespread in Australia and in many of the islands of the South Pacific, although it is not yet established in New Zealand. Of nine dogs examined for this parasite at the veterinary clinic of the Department of Agriculture, Suva, during June, 1949, five proved to be infected.

The measurements of the microfilariae from the blood of these dogs compare favourably with those given by Mönnig (1934). Averages obtained from the measurement of ten examples are given below. The figures in parentheses are those quoted by Mönnig, from the records of various authors. The distance figures given in every case express the percentage of the total body length.

Distance of nerve ring from anterior extremity 21.4% (21.4% and 22.8%)
Distance of excretory pore from anterior extremity 31.0% (29.3% and 31.0%)
Distance of anal pore from anterior extremity 77.1% (74.4% and 77.8%)
Distance of last tail cell from anterior extremity 91.1% (90.9% and 92.0%)
Total length of body 223.3μ (218.0μ-239.0μ)

The embryos of D. immitis, being unsheathed, stain very densely with Giemsa. Consequently, it is seldom possible to differentiate the excretory cell and the genital cells in examples from my Fijian material, although the other structural features of taxonomic significance and the cuticular an nidations appear to advantage (Fig. 2).

Among the mosquitoes listed by Del Rosario (1936) as known intermediary hosts for D. immitis are Aëdes aegypti (Linnaeus), Culex fatigans Wiedemann (Australia), and Aëdes vexans Meigen (Italy). These three species all occur in Fiji. Recent work (Summers, 1940, 1943) has indicated that fleas may play a more important role as vectors of D. immitis than has generally been realized. The species involved, Ctenocephalides canis (Curtis), C. felis (Bouché) and Pulex irritans Linnaeus are all found in Fiji. Pre-natal infection has also been known to occur (Augustine, 1938).