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Publications in zoology from Victoria University College, No. 5. This study forms part of an investigation carried out with the aid of a New Zealand University Research Fund Fellowship.
Our previous knowledge of the blood parasites of New Zealand birds is summarized in Table 1.
A survey of the haemotozoa of New Zealand animals carried out during Alauda arvensis and Anthus novaeseelandiae from which no material was examined. In the following pages the results of this survey are discussed and host and parasite records new to this country are given.
Birds examined for haematozoa were collected by trapping, by searching beaches after storms, and in the case of unprotected species, by shooting. Useful material was obtained from birds trapped by members of the Ornithological Society of New Zealand during routine banding work. Blood smears were taken from the birds concerned by pricking one of the superficial vessels of the leg, this method being used with large numbers of even small species such as Zosterops lateralis (silvereye) without causing them any ill effects. It should be made clear, however, that this method, although desirable in the case of rare and protected birds, is not productive of the best results. Some Leucocytosoon and Toxoplasma infections are liable to be overlooked unless smears are made from the heart blood, as is suggested by the fact that the only one of 124 specimens of Zosterops lateralis
Toxoplasma was the only specimen from which heart blood smears were examined.
During the Plasmodium infection in an example of Anas poicilorhyncha (grey duck) led to the development of a small self-contained collecting outfit, numbers of which were distributed among the members of the various Acclimatization Societies in time for the
Thin blood and organ smears were made on 3 in. × 1 in. microscopic slides, air-dried, fixed in absolute methyl alcohol, and stained with Giemsa. They were left uncovered and examined under a x5 ocular and a x97 oil immersion objective. All figures were drawn with the aid of an Abbé camera lucida at a magnification of 2,400, a x15 ocular being substituted for the x5 used in searching.
Members of the genus Haemoproteus Kruse, Haemoproteus by means of inoculation (Wenyon, Plasmodium in birds, that many of these will fall as synonyms to some of the earlier described species of the genus.
Haemoproteus danilewsky was described by Kruse (Corvus comix. Parasites inseparable from H. danilewsky on morphological grounds have since been described from other hosts. Coatney and West (Corvus branchyrhynchos,
Doré's (Haemoproteus (danilewsky) from Turdus ericetorum is now confirmed, after an examination of one of his preparations in the Victoria College collection and of fresh material. This latter material consists of a single lightly-infected preparation (averaging 1 parasite per 10,000 erythrocytes) from each of the species Turdus ericetorum (eight specimens examined) and Turdus merula (14 specimens examined). Both parasitized birds were shot at Mangere. 10 miles from Auckland, in Plasmodium relictum (Grassi and Feletti, H. danilewsky is already known from Turdus merula in Europe (Cardamatis,
Doré ( According to Coatney, Halteridium) = Haemoproteus from both the above hosts, the birds being shot at Kimihia, some 60 miles south of Auckland, in Haemoproteus as H. danilewsky, and subsequently recorded what he considered to be the same species of parasite from Alauda arvensis. Of birds of this species shot at Kimihia in H. danilewsky from Alauda arvensis in Greece, while a further species, Haemoproteus alaudae (Celli and San Felice, Haemoproteus from Turdus ericetorum in various parts of Europe.
The younger gametocytes of H. danilewsky (Pl. 1, Fig. 2) have no pigment. Microgametocytes in my preparations range from 10.7 to 18.0μ in total length, and from 1.8 to 2.3μ (the approximate limit of the available space between the cell membrane and nuclear membrane of the host cell) in breadth at the nucleus. The cytoplasm is lightly vacuolated, and appears whitish-blue to pale blue with Giemsa, while the diffuse nucleus, usually central in position, stains pale pink. This latter structure may be ovoid (Pl. 1, Figs. 3 and 4) or irregular (Pl. 1, Fig. 6) in shape, but is more usually elongate, extending along one side of the parasite only (Pl. 1, Fig. 5) or occupying the full width of the body (Pl. 1, Figs. 7 and 8). The pigment granules are round to ovoid in shape and irregular in size, the number present ranging from 9 to 18 and averaging 14. Macrogametocytes range in total length from 10.2 to 23.0μ, and in breadth at the nucleus from 1.5 to 2.3μ. The cytoplasm is lightly vacuolated and stains deep blue, and the centrally placed nucleus is a compact structure round to ovoid in shape and staining deep
Both microgametocytes and macrogametocyetes are typically C-shaped when fully developed (Pl. 1, Figs. 8 and 11). A few large macrogametocytes surround the host cell nucleus and almost completely fill the available space between the cell and nuclear membranes (Pl. 1, Fig. 12). The host erythrocyte does not show marked hypertrophy. Those cells appearing longer and thinner than the others in Pl. 1 (Figs. 7 and 9) are from a part of the preparation showing longitudinal distortion of erythrocytes as a result of the smearing process. The only case of double infection observed, in which the host cell contains a developing microgametocyte and a developing macrogametocyte, is illustrated in Pl. 1, Fig. 9.
H. danilewsky from Turdus ericetorum and T. merula agrees in all essentials of its morphology with the parasite described from Corvus by Kruse (Haemoproteus from Turdus ericetorum, and from his rough sketches of this parasite, that his measurements must have been made in a straight line between the end limits of the body instead of following the curving centre line. This was found to be the case on a re-examination of one of Doré's slides in the Victoria College collection.
No smears were obtained from Alauda arvensis during the survey, and none of Doré's slides of the Haemoproteus from this host could be found in the small collection of his material at the Dominion Museum, Wellington. There is nothing in Doré's (H. danilewsky, but opinion must be withheld until fresh material has been obtained and compared with the descriptions of H. danilewsky and of H. alaudae.
According to Wenyon, Leucocytozoon fringillinarum was described by Woodcock (Fringilla coelebs, in England. A year later Prowazek
Huff (L. simondi are found in lymphocytes, monocytes, myelocytes, and polychromatophile erythroblasts, and that the cells containing fully grown gametocytes appear to be macrophages. Host cells of leucocytozoa undergo rapid changes in the initial stages of invasion by the parasites, making it far from clear in many cases whether erythroblasts, mononuclear leucocytes or both kinds of cell are involved, as de Mello (L. fringillinarum have an eccentric nucleus with a few large chromatin masses and light blue staining cytoplasm, strongly suggestive of the normal condition of the mononuclear leucocyte. Nevertheless, hypertrophy of the nucleus accompanied by a marked change in the condition of its chromatin, together with displacement of this structure towards the side of the cell distant from the Leucocytozoon, might well be an early consequence of the invasion of an erythroblast. The staining reaction of the host cell cytoplasm—which in the earlier stages of infection (Pl. 1, Fig. 17) resembles that of later erythroblasts (Pl. 1, Fig. 15) as closely as that of leucocytes—similarly does not necessarily indicate leucocyte affinities. During the course of an infection, this staining reaction becomes less and less marked, until the cytoplasm appears as an ill-defined blue band at the periphery of a whitish area (Pl. 1, Fig. 21) and finally disappears altogether (Pl. 1, Figs. 20 and 22). Wingstrand (Leucocytozoon is marked at as early a stage of infection as when the parasite measures only 1μ in diameter. This author states that "in the few cases when I have been able to establish its identity the parasitized cell has been an erythroblast." I do not believe that there are sufficient grounds for considering the host cells of L. fringillinarum in my material to be leucocytes; and regard them as erythroblasts, the normal development of which has been grossly altered by some agent secreted by the parasite during the early stages of infection.
The genus Leucocytozoon embraces two distinct types of parasite, which de Mello (Leucocytozoon concerned. L. fringillinarum is of rounded form and occupies host cells showing no signs of tail-like prolongations, and thus belongs to the second type of parasite described above.
Male and female gametocytes at all stages of development occur in my material of L. fringillinarum. The microgametocytes have rather hyaline cytoplasm which stains a very light blue with Giemsa and is not markedly granular. Small masses of extra-nuclear chromatin may be present (Pl. 1, Figs. 18, 19, 20). The nucleus itself is large and rather diffuse, and stains light pink. Rounded microgametocytes vary in diameter from 3.1μ (youngest form seen) to 9.0μ, in the case of adults, while ovoid forms (Pl. 1, figs. 18, 19, 20) measure from 6.6 by 4.0μ to 8.5 by 4.0μ in their greatest dimensions. The cytoplasm of the macrogametocyte is more granular than that of the microgametocyte, and takes a much darker blue stain. Wingstrand (
The Leucocytozoon recorded from Fringilla coelebs in Wellington agrees so closely with Woodcock's (L. fringillinarum from the same host as to leave no doubt that it is conspecific with the latter parasite.
Doré's (Turdus ericetorum is now expanded to Plasmodium relictum on the basis of an examination of one of his preparations in the Victoria College collection and of fresh material (three of eight thrushes shot at Mangere in Haemoproteus danilewsky as mentioned earlier). P. relictum is also recorded from another of Doré's hosts, Turdus merula, two birds shot at Mangere in Passer domesticus is now listed as a host for Plasmodium relictum for the first time from New Zealand (two out of 11 birds infected, one collected at Mangere in P. relictum in other countries (Coatney and Roudabush,
In addition, an extremely light infection of Plasmodium sp? is recorded from one of 210 specimens of Anas poicilorhyncha. The parasitized bird was shot near Lake Wairarapa, Wellington, in Anas poicilorhyncha is a new host for Plasmodium. During these studies no material was examined from Anthus novaeseelandiae and Alauda arvensis. Doré's description of Plasmodium from these hosts are too general to be of much assistance in specific identification, and the slides which he deposited in the Dominion Museum, Wellington, are too badly preserved to be of use in this respect.
Trophozoites of P. relictum in my material have rather alveolar cytoplasm staining sky blue with Giemsa, and a small chromatin mass staining bright pink. Ring-forms are some 2μ in diameter, and amoeboid forms (Pl. 2, Fig. 2) measure from 2.8 to 5.6μ by 2.0 to 4.0μ in their greatest dimensions. Three trophozoites only have been found in a smear of the peripheral blood of the specimen of Anas poicilorhyncha referred to above. These are elongate reniform bodies (Pl. 2, Fig. 3) of more regular outline than is usual in trophozoites of P. relictum. As neither schizonts nor gametocytes are present in the preparation, specific identification cannot be made. Wolfson (P. relictum into ducks (Anas boschas domestica), and found that in the first transfer parasites could only be demonstrated by subinoculation of the blood of infected ducks into canaries. At a later stage, gametocytes of P. relictum found in the blood of the ducks were atypical, being elongate instead of round. Wolfson suggests that the differences in morphology between P. relictum in ducks and other hosts may be due to physico-chemical differences between the red blood cells concerned. From the facts that only one of 210 specimens of Anas poicilorhyncha examined for haematozoa was positive for Plasmodium, and that the infection is so extremely light and the trophozoites atypical, it appears likely that this duck is not normally a host for Plasmodium. The presence of all but the youngest trophozoites of Plasmodium relictum, also those of Plasmodium sp? of the grey duck, within a red corpuscle, usually causes displacement of the host-cell nucleus to a greater or lesser extent.
Schizonts of P. relictum encountered in heart-blood smears from the song thrush (Pl. 2, Figs. 5–9), blackbird, and sparrow (Pl. 2, Fig. 4) have alveolar cytoplasm
Plasmodium relictum and Haemoproteus danilewsky. Schizonts vary in size from 4.9 to 7.9μ by 4.0 to 6.0μ. Host cells containing them are often distorted and slightly hypertrophied, and their nuclei are markedly displaced.
Macrogametocytes (Pl. 2, Figs. 10 and 12) have rather dense cytoplasm which stains deep blue and an irregularly shaped nucleus staining deep pink. The pigment granules, which are scattered throughout the cytoplasm, are round or ovoid and variable in size. They are never elongate or rod-like as are those of Plasmodium cathemerium (Manwell,
The Plasmodium recorded from Turdus ericetorum, T. merula and Passer domesticus during the present survey is identified as P. relictum from the morphological features seen in Giemsa-stained blood smears. Its gametocytes are round, oval, or irregular in shape, a feature shared by only five well-established species of Plasmodium from birds, three of these each being restricted to a single host species (Manwell, P. relictum and P. cathemerium. may be distinguished by the shape of the pigment granules of the gametocytes, those of the former species being round or ovoid and those of the latter elongate or rod-like. As the pigment granules of the gametocytes of the species under discussion are round or ovoid, this parasite is identified as P. relictum.
Fantham and Porter (Plasmodium relictum var. spheniscidae from blood smears taken from four species of penguins in their natural habitats. These authors justified their description of a new variety on the grounds of the large vacuoles of the ring stages, the large size of the schizonts, the high level of intraerythrocytic schizogony together with the low gametocyte level, arid the small size of the gametocytes, as "compared with the corresponding stages of Plasmodium relictum in other hosts. One of the infected birds (Eudyptes) = Megadyptes antipodes (yellow-crowned penguin) was taken in Foveaux Strait between the South Island and Stewart Island.
During my survey I found the same variety of P. relictum in smears taken from one of two examples of Megadyptes antipodes in Campbell Island, also in preparations from three of 28 examples of Eudyptes pachyrhynchus (drooping-crested penguin) collected at the Snares Islands. The latter host is a new one for Plasmodium, and both localities are new. In all cases the infections were very light. This variety of P. relictum is mentioned here only because it has previously been recorded from New Zealand, and it is proposed to incorporate a full description of the material from Campbell Island and the Snares Islands in a paper on the haematozoa of the subantarctic islands which is in course of preparation.
Organisms answering to the description of the genus Toxoplasma Nicolle and Manceaux, Zosterops lateralis (silvereye) collected at Masterton in Haemoproteus, and, as a special watch was being kept for parasites of this genus in view of their discovery in the same host in Australia (Cleland and Johnston, Haemoproteus but Toxoplasma. Although this parasite was not recorded from any of the other Zosterops examined, its presence might easily have been overlooked, due to the fact that infections are often confined to the internal organs and are consequently not apparent from the examination of peripheral blood smears (Hewitt,
The Toxoplasma from Zosterops lateralis was found in the cytoplasm of endothelial cells and mononuclear leucocytes, some 20 per cent. of the latter cells being infected.
It is of elongate-oval, crescentic or reniform shape, one end often being more pointed than the other. The cytoplasm stains whitish-blue to light blue with Giemsa. It may be rather granular (Pl. 2, Fig. 14) or maculated (Pl. 2, Figs. 13 and 15), and often contains a number of small vacuoles (Pl. 2, Fig. 16). The nucleus, which may be central in position (Pl. 2, Figs. 14 and 15) or situated towards one extremity (Pl. 2, Figs. 13 and 16), is an irregularly shaped structure staining light pink. It frequently contains numerous small granules of chromatic material staining deeper pink. The average measurements of twenty individuals at their greatest dimensions are 8.5μ (7.0 to 10.4μ) by 3.4μ (2.9 to 4.5μ). The nuclei of these parasites measure some 4.0 by 2.7μ (range 2.9 to 6.2μ by 2.1 to 3.3μ). Parasitized leucocytes show a marked hyperchromatosis of the nucleus, and their cytoplasm may become pale staining and markedly alveolar, as described
Toxoplasma. No cases of double infection of a leucocyte nor any indications of schizogony have yet been seen in the material from Zosterops lateralis.
There is no previous record of Toxoplasma from New Zealand. The only Australian record is that of Lawrence (Toxoplasma-like bodies of Wolfson (Passer domesticus) examined at Sydney.
There is much doubt as to the systematic position of the toxoplasms. Wenyon (Toxoplasma, this author considers the genus to be of vegetable nature and related to Histoplasma capsulatum or some other such yeast-like parasite. Some of the organisms from Zosterops lateralis superficially resemble the gametocytes of Hepatozoon and other intracellular haematozoa, as Hewitt (Toxoplasma-like bodies of Wolfson (Toxoplasma described above, believing that the application of such a name would only lead to confusion in the present unsatisfactory state of our knowledge of these organisms.
Doré (
A very full investigation of the haematozoa of New Zealand birds, both indigenous and exotic, will have to be made before any decision can be reached concerning the effect of these parasites on the native avian fauna, as Doré himself informed Myers (Simulium-transmitted leucocytozoa, which may cause fatal epidemics among ducks (O'Roke, Simulium australe might serve as a vector for these parasites in New Zealand. As Fisher (
Apart from two species of penguins (Megadyptes antipodes and Eudyptes pachyrhynchus) which breed on the subantarctic islands south of New Zealand, from which Plasmodium relictum var. spheniscidae is recorded, the only indigenous birds as yet known to be hosts for haematozoa are Anas poicilorhyncha (Plasmodium sp?) and Anthus novaeseelandiae (Plasmodium sp?). In so far as the indigenous portion of the New Zealand avian fauna has been examined for haematozoa (Table 2), it appears to be exceptionally free of these parasites. No material has yet been examined from any of the migratory birds, which offer the only avenue other than the agency of man for the introduction of avian haematozoa into this country. It is of decided interest in this connection that Toxoplasma sp? is here recorded from Zosterops lateralis, a species which reached New Zealand apparently from Australia or Tasmania in
Australian native birds have a rich fauna of Trypanosoma, Haemoproteus, Leucocytozoon, Plasmodium, and Microfilaria, and Lawrence (Toxoplasma from Passer domesticus in Sydney. Neither Trypanosoma nor Microfilaria have yet been recorded from birds in New Zealand. Cleland (Plasmodium biziurae? from the black swan (Chenopis atrata) = Cygnus atratus, one specimen of two examined in Australia being positive for this parasite. Following its introduction into New Zealand during last century, Cygnus atratus has become common and widespread, and is now regarded as a game bird. Smears from 99 specimens of this bird were examined during the survey, but all proved negative for haematozoa. Cleland and Johnston (Haemoproteus from Zosterops lateralis in Australia. Two of 14 birds examined by the former authors and one of three examined by Lawrence were infected with this parasite. As Haemoproteus was not recorded from any of the 124 specimens of Z. lateralis examined during my survey, it seems likely that the parasite did not accompany its vertebrate host to New Zealand, or, at all events, has failed to become established in the Wairarapa, the part of the country from which my material was obtained.
None of the 95 examples of the common pigeon Columba livia examined were infected with Haemoproteus columbae Kruse, Lynchia maura, it is too early to regard Haemoproteus columbae as definitely absent from New Zealand.
No indigenous species of haematozoa have yet been described from New Zealand birds. Plasmodium relictum var. spheniscidae, recorded by Fantham and Porter (Megadyptes antipodes in Foveaux Strait, is apparently of circumpolar distribution. The other Haemosporidia specifically identified during this survey were originally described from Europe, whence their hosts originate. It is likely that Plasmodium sp? recorded from the indigenous birds Anas poicilorhyncha and Anthus novaeseelandiae will prove to be Plasmodium relictum when further material becomes available.
Neither trypanosomes nor microfilariae have yet been recorded from birds in New Zealand. The haemosporidian genus Leucocytozoon is now listed from this country for the first time, as is Toxoplasma, the systematic position of which is still in question. Doré's (Plasmodium from Turdus ericetorum and Turdus merula is expanded to Plasmodium relictum; and his tentative identification of Haemoproteus danilewsky from these same hosts is confirmed. Anas poicilorhyncha is given as a new host for Plasmodium sp?, and Passer domesticus is recorded as an additional New Zealand host for Plasmodium relictum.
I have pleasure in acknowledging the assistance rendered me by the secretaries of the New Zealand Acclimatization Societies and the many members of these societies who collected blood smears during the