The first records of human infestation by the hard tick Ixodes (Endopalpiger) australiensis (Acari: Ixodidae), with a review of human infestation by ticks in Australia

The bacterial biome of ticks and their wildlife hosts at the urban-wildland interface

Advances in sequencing technologies have revealed the complex and diverse microbial communities present in ticks (Ixodida). As obligate blood-feeding arthropods, ticks are responsible for a number of infectious diseases that can affect humans, livestock, domestic animals and wildlife. While cases of human tick-borne diseases continue to increase in the northern hemisphere, there has been relatively little recognition of zoonotic tick-borne pathogens in Australia. Over the past 5 years, studies using high-throughput sequencing technologies have shown that Australian ticks harbour unique and diverse bacterial communities. In the present study, free-ranging wildlife (n=203), representing ten mammal species, were sampled from urban and peri-urban areas in New South Wales (NSW), Queensland (QLD) and Western Australia (WA). Bacterial metabarcoding targeting the 16S rRNA locus was used to characterize the microbiomes of three sample types collected from wildlife: blood, ticks and tissue samples. Further sequence information was obtained for selected taxa of interest. Six tick species were identified from wildlife: Amblyomma triguttatum, Ixodes antechini, Ixodes australiensis, Ixodes holocyclus, Ixodes tasmani and Ixodes trichosuri. Bacterial 16S rRNA metabarcoding was performed on 536 samples and 65 controls, generating over 100 million sequences. Alpha diversity was significantly different between the three sample types, with tissue samples displaying the highest alpha diversity (P<0.001). Proteobacteria was the most abundant taxon identified across all sample types (37.3 %). Beta diversity analysis and ordination revealed little overlap between the three sample types (P<0.001). Taxa of interest included Anaplasmataceae, Bartonella, Borrelia, Coxiellaceae, Francisella, Midichloria, Mycoplasma and Rickettsia. Anaplasmataceae bacteria were detected in 17.7% (95/536) of samples and included Anaplasma, Ehrlichia and Neoehrlichia species. In samples from NSW, 'Ca. Neoehrlichia australis', 'Ca. Neoehrlichia arcana', Neoehrlichia sp. and Ehrlichia sp. were identified. A putative novel Ehrlichia sp. was identified from WA and Anaplasma platys was identified from QLD. Nine rodent tissue samples were positive for a novel Borrelia sp. that formed a phylogenetically distinct clade separate from the Lyme Borrelia and relapsing fever groups. This novel clade included recently identified rodent-associated Borrelia genotypes, which were described from Spain and North America. Bartonella was identified in 12.9% (69/536) of samples. Over half of these positive samples were obtained from black rats (Rattus rattus), and the dominant bacterial species identified were Bartonella coopersplainsensis and Bartonella queenslandensis. The results from the present study show the value of using unbiased high-throughput sequencing applied to samples collected from wildlife. In addition to understanding the sylvatic cycle of known vector-associated pathogens, surveillance work is important to ensure preparedness for potential zoonotic spillover events.

First record of the stump-tailed lizard tick, Amblyomma albolimbatum (Ixodida, Ixodidae) parasitising a human

Ticks are haematophagous arthropods that parasitise a wide range of vertebrate hosts. In Australia, there are currently 74 tick species described; 22 tick species have been reported parasitising humans. The stump-tailed lizard tick, Amblyomma albolimbatum, feeds on reptiles, most commonly lizards and snakes; however, we report the first case of A. albolimbatum parasitising a human. The nymphal tick was removed while conducting fieldwork on western tiger snakes (Notechis scutatus occidentalis) in an urban city environment near Perth, Western Australia. The tick was identified using morphological descriptions, which was further supported by the abundance of all parasitic stages of A. albolimbatum on the tiger snakes sampled. The number of tick species recorded from humans in Australia is now revised to 23 species. With the increasing incidence of tick-borne illnesses in Australia, this study highlights the need to report cases of new or atypical hosts, particularly humans, and especially when the ticks have been associated with zoonotic pathogens.

An annotated checklist of the eukaryotic parasites of humans, exclusive of fungi and algae

The classification of "parasites" in the medical field is a challenging notion, a group which historically has included all eukaryotes exclusive of fungi that invade and derive resources from the human host. Since antiquity, humans have been identifying and documenting parasitic infections, and this collective catalog of parasitic agents has expanded considerably with technology. As our understanding of species boundaries and the use of molecular tools has evolved, so has our concept of the taxonomy of human parasites. Consequently, new species have been recognized while others have been relegated to synonyms. On the other hand, the decline of expertise in classical parasitology and limited curricula have led to a loss of awareness of many rarely encountered species. Here, we provide a comprehensive checklist of all reported eukaryotic organisms (excluding fungi and allied taxa) parasitizing humans resulting in 274 genus-group taxa and 848 species-group taxa. For each species, or genus where indicated, a concise summary of geographic distribution, natural hosts, route of transmission and site within human host, and vectored pathogens are presented. Ubiquitous, human-adapted species as well as very rare, incidental zoonotic organisms are discussed in this annotated checklist. We also provide a list of 79 excluded genera and species that have been previously reported as human parasites but are not believed to be true human parasites or represent misidentifications or taxonomic changes.

Habitat impacts the abundance and network structure within tick (Acari: Ixodidae) communities on tropical small mammals

Ticks of small mammals pose a significant risk to public health but these hazards are poorly understood in the tropics due to the paucity of information on the disease ecology of ticks in these regions. Mapping and quantifying the diversity of small mammal/tick networks and the effects of habitat on these medically important systems is key to disease prevention. Singapore represents a microcosm of much of tropical Asia as it has a diverse, though poorly studied, community of ticks and small mammals. Singapore also has a range of terrestrial habitats exhibiting a gradient of degradation. Small mammals and their ticks were sampled across the island in four main habitat types (old secondary forest, young secondary forest, scrubland, urban) across 4.5 years. Four tick species were collected (Amblyomma helvolum, Dermacentor auratus, Haemaphysalis semermis, Ixodes granulatus) from 10 small mammal species. Habitat was found to have a significant effect on both the abundance and structure of tick communities on small mammals. Old secondary forest communities had the highest tick abundance, comparatively high connectance, niche overlap (among ticks), linkage density, and were the preferred habitat of the zoonotic tick I. granulatus. Therefore, future disease spillover is likely to emerge from small mammal-tick communities in old secondary forests.

Tick-crocodilian interactions: a review, with the first record of tick (Acari: Ixodidae) infestation in the saltwater crocodile (Crocodylus porosus), and a concise host-parasite index

Interactions between ticks and crocodilians (crocodiles, alligators, caiman, and gharials) are poorly studied but may have significant bearing on the ecology and health of these reptiles. The first record of tick infestation of the saltwater crocodile (Crocodylus porosus) is reported along with the first case of infestation by Amblyomma cordiferum on Cuvier's dwarf caiman (Paleosuchus palpebrosus). A review is also provided of tick-crocodilian interactions with a concise host-parasite index.

Tick killing in situ before removal to prevent allergic and anaphylactic reactions in humans: a cross-sectional study

BACKGROUND

Tick anaphylaxis is a potentially fatal outcome of improper tick removal and management.

OBJECTIVE

To investigate whether killing ticks in-situ with ether-containing sprays or permethrin cream, before careful removal by the mouthparts could reduce this risk.

METHODS

This was a prospective study at Mona Vale Hospital Emergency Department (ED) in Sydney, New South Wales, over a 6-month period during the peak tick season of 2016. Tick removal methods, allergic/anaphylactic reactions were recorded for patients presenting with ticks in situ or having already removed the ticks themselves. Primary endpoint was allergic/anaphylactic reaction after tick killing/removal.

RESULTS

One hundred twenty-one patients met study inclusion criteria. Sixty-one patients (28 known tick-hypersensitive) had ticks killed with Wart-Off Freeze or Lyclear Scabies Cream (5% w/w permethrin) before removal with fine-tipped forceps or Tick Twister. Three patients (2 known tick-hypersensitive) had allergic reactions (5%), none anaphylactic. The 2 known hypersensitive patients suffered reactions during the killing process and the third patient had a particularly embedded tick meaning it could not be removed solely by mouthparts. Fifty patients presented to the ED posttick removal by various methods, none using either fine-tipped forceps or Tick Twister, of which 43 (86%) experienced allergic reactions - 2 anaphylactic. Five patients suffered allergic reactions before presentation despite no attempt at kill or removal, but ticks had likely been disturbed by some other method. Five patients had live ticks removed in ED - 3 refused killing and had no reaction despite 1 having known hypersensitivity; 2 had ticks on eyelids contraindicating killing, 1 with known hypersensitivity but both had allergic reactions post removal.

CONCLUSION

Results support killing ticks in-situ before careful removal by mouthparts to reduce allergic/anaphylactic reactions although further research is still required.

A novel Australian tick Ixodes (Endopalpiger) australiensis inducing mammalian meat allergy after tick bite

Tick-induced mammalian meat allergy has become an emergent allergy world-wide after van Nunen et al. first described the association between tick bites and the development of mammalian meat allergy in 2007. Cases of mammalian meat allergy have now been reported on all 6 continents where humans are bitten by ticks, in 17 countries - Australia, United States of America (USA), Europe (France, Spain, Germany, Belgium, Switzerland, Sweden, United Kingdom, Italy, and Norway), Asia (Korea and Japan), Central America (Panama), South America (Brazil), and Africa (South Africa and Ivory Coast). To date, in each of these countries, bites from only a single tick species have been linked to the development of mammalian meat allergy: Ixodes holocyclus (Australia), Amblyomma americanum (USA), Ixodes ricinus (Europe), and Ixodes cajennense (Panama) are confirmed as culprits, and Ixodes nipponensis (Japan and Korea), Amblyomma sculptum (Brazil), Amblyomma variegatum (Ivory Coast), and Haemaphysalis longicornis (Japan) suspected of provoking mammalian meat allergy after tick bite. Other tick species remain to be formally identified (South Africa). Identification of tick species associated with development of mammalian meat allergy is crucial to the uptake of public health measures to prevent tick bites from culprit tick species, for both individuals living in these tick-endemic areas and those who choose to visit these regions. We report a tick associated with the enhancement of mammalian meat anaphylaxis after tick bite which is novel for both Australia and the world and establishes Ixodes (Endopalpiger) australiensis as a second tick species associated with mammalian meat allergy in Australia.

Could Australian ticks harbour emerging viral pathogens?

Tick-borne viruses contribute significantly to the disease burden in Europe, Asia and the US. Historically, some of the most well-known viruses from this group include the human pathogens, tick-borne encephalitis virus and Crimean-Congo haemorrhagic fever virus. More recently multiple emerging tick-borne viruses have been associated with severe disease in humans with Bourbon virus and Heartland virus isolated from patients in the US and severe fever with thrombocytopenia syndrome virus reported from China, Japan, and South Korea. Such examples highlight the need for broader approaches to survey arthropod pathogens, to encompass not only known but novel pathogens circulating in Australian tick populations.