M.R. Alley

Malaria parasites (Plasmodium spp.) infecting introduced, native and endemic New Zealand birds

Avian malaria is caused by intracellular mosquito-transmitted protist parasites in the order Haemosporida, genus Plasmodium. Although Plasmodium species have been diagnosed as causing death in several threatened species in New Zealand, little is known about their ecology and epidemiology. In this study, we examined the presence, microscopic characterization and sequence homology of Plasmodium spp. isolates collected from a small number of New Zealand introduced, native and endemic bird species. We identified 14 Plasmodium spp. isolates from 90 blood or tissue samples. The host range included four species of passerines (two endemic, one native, one introduced), one species of endemic pigeon and two species of endemic kiwi. The isolates were associated into at least four distinct clusters including Plasmodium (Huffia) elongatum, a subgroup of Plasmodium elongatum, Plasmodium relictum and Plasmodium (Noyvella) spp. The infected birds presented a low level of peripheral parasitemia consistent with chronic infection (11/15 blood smears examined). In addition, we report death due to overwhelming parasitemia in a blackbird, a great spotted kiwi and a hihi. These deaths were attributed to infections with either Plasmodium spp. lineage LINN1 or P. relictum lineage GRW4. To the authors’ knowledge, this is the first published report of Plasmodium spp. infection in great spotted and brown kiwi, kereru and kokako. Currently, we are only able to speculate on the origin of these 14 isolates but consideration must be made as to the impact they may have on threatened endemic species, particularly due to the examples of mortality.

Naturally occurring tuberculosis caused by Mycobacterium bovis in brushtail possums (Trichosurus vulpecula): II. Pathology

The gross and microscopic lesions due to Mycobacterium bovis infection are described in 73 brushtail possums (Trichosurus vulpeculu) from population studies and from 11 terminally ill possums. Subcutaneous lesions were suppurative in nature, often discharging through sinuses to the exterior. Histologically, the smallest lesions comprised focal aggregations of macrophages with angulated cytoplasmic boundaries occasionally containing acid-fast organisms. Larger lesions were pyogranulomatous, with extensive necrosis, caseation and large numbers of intra- and extra-cellular acid-fast organisms. Few multinucleate giant cells were seen and fibroplasia was rare. Mineralisation was recorded in tuberculous lymph nodes from only two possums. Histological evidence of haematogenous and lymphatic spread was seen in some cases.

Chronic non-progressive pneumonia of sheep in New Zealand - a review of the role of Mycoplasma ovipneumoniae.

Chronic non-progressive pneumonia (CNP) is a common disease which affects lambs in New Zealand during late summer and autumn. Mycoplasma ovipneumoniae can be recovered from a high proportion of lesions but it is also present in some normal lungs. Bacteria, especially Pasteurella haemolytica, can also be recovered from more than half the lungs of affected animals. Isolates of M. ovipneumoniae are genetically heterogeneous, as demonstrated by examination of their DNA or total cellular proteins, and are serologically heterogeneous as shown by metabolic inhibition tests. The number of strains present in New Zealand is large and several distinguishable strains can be recovered from each affected lung. Mycoplasma ovipneumoniae has pathogenic potential as indicated by its ability to produce hydrogen peroxide, cause ciliostasis and by its possession of a capsule. Chronic non-progressive pneumonia can be transmitted consistently to over 50% of lambs by inoculation of pooled pneumonic lung homogenate and transmission can be suppressed by broad spectrum antibiotics. In contrast, penicillin does not prevent the development of lesions but diminishes their severity. Pooled lung homogenate treated with digitonin, which inactivates mycoplasmas, has failed to transmit CNP. Pure cultures of M. ovipneumoniae produce only mild lesions in some animals, whereas inoculation with pooled lung homogenate (from which no viruses were isolated) containing mixed strains of M. ovipneumoniae and free from bacteria, is more effective in producing lesions. Research work to date suggests that CNP may be initiated by colonisation of the lung by M. ovipneumoniae which causes ciliostasis and elicits an exudate allowing colonisation of the lungs by bacteria especially M. haemolytica and by other strains of M. ovipneumoniae. The immune response to the initial strain of M. ovipneumoniae may inhibit its replication but would be less effective in inhibiting heterologous strains of the organism allowing their sequential replication. Eventually production of a broad immune response to M. ovipneumoniae would lead to its elimination which in turn would facilitate the elimination of other microorganisms and the resolution of lesions. As natural immunity to CNP occurs within the first year, it may be possible to develop an effective and useful vaccine. Such a vaccine may need to include multiple strains of M. ovipneumoniae.

Bordetella parapertussis from lambs.

Abstract Extract Madam:—An organism identified as Bordetella parapertussis has been isolated in significant numbers from nasal swabs, bronchial washings and the lungs of 6–10 month old lambs showing signs of pneumonia. It has also been isolated from normal lambs but attempts to recover it from adult sheep have so far been unsuccessful (Table I).

The bacterial flora of the respiratory tract of normal and pneumonic sheep

Abstract Extract For many years chronic and subacute pneumonia has been recognized as a common finding in the lungs of lambs at slaughter throughout New Zealand. While the effect of the disease on weight gain is not clear, there can be no doubt that residual pleuritis is an important cause of economic loss through high condemnation rates of carcasses.

Aspergillosis in hihi (Notiomystis cincta) on Mokoia Island

AIM An intensive 2-year field study of 65 hihi (or stitchbirds) on Mokoia Island provided an opportunity to investigate the causes of mortality of this endangered species in a free-living environment. METHODS The birds were observed daily during the breeding season (October to March) and every 4 weeks during the remainder of the year. Any abnormalities in behaviour, voice and body weight were recorded and all sick or dead birds which could be recovered were taken to the laboratory for necropsy. RESULTS Thirty-one birds died during the period of this study. Aspergillosis was found to be the cause of death in six of nine adult birds examined post mortem. Some of the affected birds experienced subtle voice changes before becoming ill and all birds had granulomatous lesions in airsacs or lungs at necropsy. A further eight birds for which carcasses could not be found or which were autolysed showed similar clinical signs before death or disappearance. CONCLUSION Because Aspergillus is an opportunist pathogen it seems likely that affected birds were immunosuppressed. This may have occurred during the breeding season which in this species is highly stressful. The presence of fungal material in bronchial exudate and the occurrence of the disease in mates, raises the possibility that aspergillosis in hihi may be contagious.

A new prey‐detection mechanism for kiwi (Apteryx spp.) suggests convergent evolution between paleognathous and neognathous birds

Kiwi (Apterygidae: Apteryx spp.) are traditionally assumed to detect their soil‐dwelling invertebrate prey using their sense of smell. The unique position of the nares at the tip of the bill and the enlarged olfactory centres in the brain support this assumption. However, studies designed to show the importance of olfaction in prey‐detection by Apteryx have provided equivocal results. Another family of probing birds, the Scolopacidae, detect their buried prey using specialised vibration and pressure‐sensitive mechanoreceptors embedded in pits in the bill‐tip. We found that aspects of the foraging patterns of Apteryx mantelli are like those of scolopacid shorebirds, suggesting that Apteryx may be using a similar prey‐detection mechanism. We examined specimens of all five Apteryx species and conducted a morphological and histological examination of the bill of A. mantelli. We discovered that Apteryx possess an arrangement of mechanoreceptors within pits similar to that in Scolopacidae species and may therefore be able to localise prey using a similar vibrotactile sense. We suggest that this sense may function in conjunction with, or be dominant over, olfaction during prey‐detection. The Apterygidae and the Scolopacidae are members of the two different super‐orders of birds: the Paleognathae and the Neognathae, respectively. Therefore we cite the similar bill‐tip anatomy of these two families as an example of convergent evolution across a deep taxonomic divide.

Circovirus-like infection in a southern black-backed gull (Larus dominicanus)

A juvenile black-backed gull (Larus dominicanus) from the Manawatu region of New Zealand was found to have chronic airsacculitis due to Aspergillus spp. Histologically, there was moderately severe inflammation in the bursa of Fabricius associated with large, basophilic, intracytoplasmic inclusions, which ultrastructurally had an appearance typical of circovirus inclusions. This finding suggests that circoviruses may be more widespread in avian species than previously recognized and may be responsible for diseases associated with immunosuppression in free-living birds.

The prevalence of Mycoplasma ovipneumoniae and Mycoplasma arginini in the respiratory tract of sheep.

Abstract Extract In an initial study of mycoplasmas of the respiratory tract of New Zealand sheep a number of strains of mycoplasma were recovered and identified as either M. ovipneumoniae or M. arginini (Clarke et al., 1974). Investigations in Australia have produced evidence that M. ovipneumoniae is associated with a proliferative interstitial pneumonia in Queensland sheep (Sullivan et al., 1973) and for this reason the present survey was undertaken to investigate the prevalence of mycoplasmas in the respiratory tract of sheepin New Zealand.

An outbreak of avian malaria in captive yellowheads/mohua (Mohoua ochrocephala)

Abstract CASE HISTORY: Eight mohua, or yellowheads (Mohoua ochrocephala), were held in a large open aviary over the summer months of 2003–2004, following their capture for captivebreeding purposes. Two birds died of transportation trauma shortly after arrival, one became ill and died a month later, and another four died within a 2-week period in February 2004. The eighth bird also became ill at this time but survived for a year following treatment with chloroquine and doxycycline. CLINICAL AND PATHOLOGICAL FINDINGS: The affected birds were depressed, lethargic and dyspnoeic. Necropsy of three birds showed a slightly pale and swollen liver and spleen. Impression smears of the liver of one bird revealed schizonts resembling Plasmodium spp. within the cytoplasm of many hepatocytes, which was confirmed histopathologically. Similar protozoal organisms were seen within splenic histiocytes and pulmonary endothelial cells of 5/6 birds. Electron microscopy identified these as protozoal schizonts containing merozoites of similar size and structure to those of Plasmodium spp. DIAGNOSIS: The birds were infected with a protozoal haemoparasite resembling Plasmodium spp.; asexual stages within hepatocytes and endothelial cells of the lung and spleen were typical of this organism. CONCLUSIONS AND CLINICAL RELEVANCE: The mohua captured from west Otago were highly susceptible to avian malaria as they came from an isolated population that was likely to be naïve and have had no previous contact with this organism. The birds were probably infected by bites from mosquitoes feeding off local populations of blackbirds subsequently found to be infected with Plasmodium spp.