Aspergillosis and other causes of mortality in the stitchbird in New Zealand

A single fungal strain was the unexpected cause of a mass aspergillosis outbreak in the world's largest and only flightless parrot

Kākāpō are a critically endangered species of parrots restricted to a few islands off the coast of New Zealand. Kākāpō are very closely monitored, especially during nesting seasons. In 2019, during a highly successful nesting season, an outbreak of aspergillosis affected 21 individuals and led to the deaths of 9, leaving a population of only 211 kākāpō. In monitoring this outbreak, cultures of aspergillus were grown, and genome sequenced. These sequences demonstrate that, very unusually for an aspergillus outbreak, a single strain of aspergillus caused the outbreak. This strain was found on two islands, but only one had an outbreak of aspergillosis; indicating that the strain was necessary, but not sufficient, to cause disease. Our analysis provides an understanding of the 2019 outbreak and provides potential ways to manage such events in the future.

Aspergillosis in Wild Birds

The ubiquitous fungi belonging to the genus Aspergillus are able to proliferate in a large number of environments on organic substrates. The spores of these opportunistic pathogens, when inhaled, can cause serious and often fatal infections in a wide variety of captive and free-roaming wild birds. The relative importance of innate immunity and the level of exposure in the development of the disease can vary considerably between avian species and epidemiological situations. Given the low efficacy of therapeutic treatments, it is essential that breeders or avian practitioners know the conditions that favor the emergence of Aspergillosis in order to put adequate preventive measures in place.

A Comparison of Disease Risk Analysis Tools for Conservation Translocations

Conservation translocations are increasingly used to manage threatened species and restore ecosystems. Translocations increase the risk of disease outbreaks in the translocated and recipient populations. Qualitative disease risk analyses have been used as a means of assessing the magnitude of any effect of disease and the probability of the disease occurring associated with a translocation. Currently multiple alternative qualitative disease risk analysis packages are available to practitioners. Here we compare the ease of use, expertise required, transparency, and results from, three different qualitative disease risk analyses using a translocation of the endangered New Zealand passerine, the hihi (Notiomystis cincta), as a model. We show that the three methods use fundamentally different approaches to define hazards. Different methods are used to produce estimations of the risk from disease, and the estimations are different for the same hazards. Transparency of the process varies between methods from no referencing, or explanations of evidence to justify decisions, through to full documentation of resources, decisions and assumptions made. Evidence to support decisions on estimation of risk from disease is important, to enable knowledge acquired in the future, for example, from translocation outcome, to be used to improve the risk estimation for future translocations. Information documenting each disease risk analysis differs along with variation in emphasis of the questions asked within each package. The expertise required to commence a disease risk analysis varies and an action flow chart tailored for the non-wildlife health specialist are included in one method but completion of the disease risk analysis requires wildlife health specialists with epidemiological and pathological knowledge in all three methods. We show that disease risk analysis package choice may play a greater role in the overall risk estimation of the effect of disease on animal populations involved in a translocation than might previously have been realised.

Aspergillus and aspergilloses in wild and domestic animals: a global health concern with parallels to human disease

The importance of aspergillosis in humans and various animal species has increased over the last decades. Aspergillus species are found worldwide in humans and in almost all domestic animals and birds as well as in many wild species, causing a wide range of diseases from localized infections to fatal disseminated diseases, as well as allergic responses to inhaled conidia. Some prevalent forms of animal aspergillosis are invasive fatal infections in sea fan corals, stonebrood mummification in honey bees, pulmonary and air sac infection in birds, mycotic abortion and mammary gland infections in cattle, guttural pouch mycoses in horses, sinonasal infections in dogs and cats, and invasive pulmonary and cerebral infections in marine mammals and nonhuman primates. This article represents a comprehensive overview of the most common infections reported by Aspergillus species and the corresponding diseases in various types of animals.

Coccidiosis in hihi/stitchbirds (Notiomystis cincta) due to coccidia of the Eimeriidae

AIM

To describe the pathology of coccidiosis in hihi and to provide preliminary data on the taxonomy of the coccidia involved using molecular methods.

METHODS

In an initial study from 1994 to 1997, gross and histopathological examinations were performed on 12 dead juvenile hihi from the National Wildlife Centre (NWC) at Mt. Bruce. In a second study during 2008-2010 DNA from sporulated oocysts and liver tissue was used for PCR analysis and sequencing. Faecal samples were also obtained from infected hihi from the NWC and examined for coccidial oocysts, which were then sporulated in the laboratory in 1994-1997 and 2007-2009. In addition, a post mortem was performed on a dead adult hihi from the NWC in 2008, and 18 archived hihi tissues from 11 individual birds stored at the Institute of Veterinary, Animal and Biomedical Sciences (IVABS) were used for DNA extraction.

RESULTS

Severe gross and histopathological changes in the intestine and occasionally in the liver were found in the 12 dead birds examined. The morphological characteristics of the sporulated oocysts suggested that two types of coccidia were present. PCR analysis and sequencing of extracted DNA supported the existence of at least two different coccidia species in hihi. These were genetically more closely related to the genus Eimeria than to the morphologically similar genus Cystisospora (formerly Isospora) of mammals. In addition, one liver tissue sample that was examined post mortem was positive for at least two different coccidia species of the family Eimeriidae according to sequencing results, and the presence of extraintestinal coccidian stages was confirmed.

CONCLUSIONS

Preliminary morphological and sequencing results suggest that two types of eimeriid coccidia are present and at least one of these commonly has extraintestinal stages.

CLINICAL RELEVANCE

Coccidiosis in hihi is a serious disease capable of causing mortalities in juvenile and adult birds in captive situations. Treatment and control of the disease will be difficult as the extraintestinal stages of the organism are likely to be refractile to oral treatment.

Parasite management in translocations: lessons from a threatened New Zealand bird

Awareness of parasite risks in translocations has prompted the development of parasite management protocols, including parasite risk assessment, parasite screening and treatments. However, although the importance of such measures seems obvious it is difficult to know whether the measures taken are effective, especially when working with wild populations. We review current methods in one extensively researched case study, the endemic New Zealand passerine bird, the hihi Notiomystis cincta. Our review is structured around four of the 10 questions proposed by Armstrong & Seddon (Trends in Ecology & Evolution, 2008: 23, 20–25) for reintroduction biology. These four questions can be related directly to parasites and parasite management and we recommend using this framework to help select and justify parasite management. Our retrospective study of recent disease and health screening in hihi reveals only partial overlap with these questions. Current practice does not focus on, or aim to reduce, the uncertainty in most steps of the risk assessment process or on evaluating whether the measures are effective. We encourage targeted parasite management that builds more clearly on available disease risk assessment methodologies and integrates these tools within a complete reintroduction plan.

Sub-lingual oral fistulas in free-living stitchbirds (Notiomystis cincta)

Sub-lingual oral fistulas are a consistently observed lesion affecting the New Zealand stitchbird (hihi: Notiomystis cincta). This lesion, which has not been reported in other species, is usually only recognized when the tongue protrudes below the bird's mandible from a hole in the oral-cavity floor. In this study, we surveyed the prevalence of oral fistulas in a free-living population of stitchbirds on Tiritiri Matangi Island in 2002, 2003 and 2005. Between surveys, individuals with a fistula were caught and the progress of their lesion was monitored. The majority of birds with a fistula had a small localized lesion alongside the edge of the mandible without the tongue protruding. Oral fistulas were generally not associated with any reduction in the bird's condition or productivity, but if the tongue consistently deviated through the fistula it affected nectar-feeding efficiency. No fistulas were found in nestlings, but 9% to 10% of adult birds had some form of oral fistula, suggesting that it developed after fledging. Repeated measurement of birds showed that the size of the fistulas did not progress beyond the formation of the initial hole unless the tongue protruded. This protrusion resulted in continuous rubbing and erosion of the oral cavity floor and, ultimately, the mandible itself. Histopathology confirmed that fistulas occur in the thinnest part of the floor of the oral cavity, at the attachment point of the skin to the mandible. Despite long-term monitoring of this population, the formation of an oral fistula has never been observed and its aetiology remains elusive.

Fungal virulence, vertebrate endothermy, and dinosaur extinction: is there a connection?

Fungi are relatively rare causes of life-threatening systemic disease in immunologically intact mammals despite being frequent pathogens in insects, amphibians, and plants. Given that virulence is a complex trait, the capacity of certain soil fungi to infect, persist, and cause disease in animals despite no apparent requirement for animal hosts in replication or survival presents a paradox. In recent years studies with amoeba, slime molds, and worms have led to the proposal that interactions between fungi and other environmental microbes, including predators, select for characteristics that are also suitable for survival in animal hosts. Given that most fungal species grow best at ambient temperatures, the high body temperature of endothermic animals must provide a thermal barrier for protection against infection with a large number of fungi. Fungal disease is relatively common in birds but most are caused by only a few thermotolerant species. The relative resistance of endothermic vertebrates to fungal diseases is likely a result of higher body temperatures combined with immune defenses. Protection against fungal diseases could have been a powerful selective mechanism for endothermy in certain vertebrates. Deforestation and proliferation of fungal spores at cretaceous-tertiary boundary suggests that fungal diseases could have contributed to the demise of dinosaurs and the flourishing of mammalian species.