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Insects Collected from Aircraft Arriving in New Zealand from Abroad

Species of Veterinary Significance

Species of Veterinary Significance

A—Vectors of Disease-causing Organisms

The wasting disease of dogs known as heartworm or canine filariasis, caused by the nematode Dirofilaria immitis, is absent from New Zealand. In order to guard against its importation, together with that of other causal organisms of canine diseases, dogs may only be brought into this country under rigid quarantine regulations. Among the vectors of D. immitis are Aëdes aegypti and Culex fatigans (Del Rosario, 1936), also Pulex irritans (Summers, 1943). As has already been indicated, living examples of all these species were collected from aircraft which had come from or passed through Fiji, where heartworm is very prevalent (Laird, 1951). Any of these species, should they succeed in escaping from aircraft at Whenuapai in the infective state, might bite dogs in this area and so infect them with D. immitis. Heartworm thrives in both warm and temperate climates, and there is a decided possibility that it could become endemic at least in the northern parts of the North Island, locally bred C. fatigans and P. irritans serving to spread the disease.

Aëdes aegypti, Culex fatigans, and Stomoxys calcitrans are all known vectors of the virus which causes fowl-pox, and the first-named species may also transmit equine encephalomyelitis. Here again, there is a possibility that epidemics of these diseases might be originated in the farmlands adjacent to New Zealand airports, following the introduction of infective insects.

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B.—Producers of Pathological Conditions

The species of the Family Calliphoridae listed in Table 6 are all known sheep maggot flies. Calliphora laemica and Lucilia sericata are the primary sheep maggot flies in New Zealand (Miller, 1939), while Lucilia cuprina is the most important primary species in Australia (Mackerras, 1936). These insects cause blowfly strike, their maggots invading the living tissues of sheep, so causing myiasis. One female of C. laemica, a species native to New Zealand but not found in Australia, entered a DC4 following its arrival from the latter country in December, 1946, and deposited a number of living larvae when captured. Two living adults and many larvae of the widespread L. sericata were collected from a garbage can in the kitchen of a DC6 which arrived at Whenuapai from North America on 12th November, 1950. This species is established in Hawaii (Bryan, 1934) and Canton Island (Van Zwaluwenburg, 1943), and the examples which reached Whenuapai could have come from either of these places. Aircraft from Fiji twice harboured living examples of L. cuprina, an almost cosmopolitan species which has been introduced into that country (Bezzi, 1928). None of the other three species of Calliphoridae listed are of primary importance as sheep maggot flies. Single examples each of Calliphora erythrocephala and C. rufipes were taken alive in the astrodome and passenger compartment of a DC4 from North America, although there is a possibility that these may have flown on board following the completion of insecticidal spraying at Whenuapai. A single dead example of Chrysomyia rufifacies found in the passenger compartment of a DC6 from North America might have come on board at the airport in either Hawaii (Bryan, 1934) or Fiji (Bezzi. 1928).

The sheep maggot fly problem is of great importance to both Australia and New Zealand, the prosperity of which is so closely bound up with sheep-raising. The possible interchange between the Pacific islands and these countries of not only new species of sheep maggot flies but also dangerous strains of species already represented by harmless strains is obviously rendered possible by air transportation.