Near-term forecasting of companion animal tick paralysis incidence: An iterative ensemble model.

Tick paralysis resulting from bites from Ixodes holocyclus and I. cornuatus is one of the leading causes of emergency veterinary admissions for companion animals in Australia, often resulting in death if left untreated. Availability of timely information on periods of increased risk can help modulate behaviors that reduce exposures to ticks and improve awareness of owners for the need of lifesaving preventative ectoparasite treatment. Improved awareness of clinicians and pet owners about temporal changes in tick paralysis risk can be assisted by ecological forecasting frameworks that integrate environmental information into statistical time series models. Using an 11-year time series of tick paralysis cases from veterinary clinics in one of Australia's hotspots for the paralysis tick Ixodes holocyclus, we asked whether an ensemble model could accurately forecast clinical caseloads over near-term horizons. We fit a series of statistical time series (ARIMA, GARCH) and generative models (Prophet, Generalised Additive Model) using environmental variables as predictors, and then combined forecasts into a weighted ensemble to minimise prediction interval error. Our results indicate that variables related to temperature anomalies, levels of vegetation moisture and the Southern Oscillation Index can be useful for predicting tick paralysis admissions. Our model forecasted tick paralysis cases with exceptional accuracy while preserving epidemiological interpretability, outperforming a field-leading benchmark Exponential Smoothing model by reducing both point and prediction interval errors. Using online particle filtering to assimilate new observations and adjust forecast distributions when new data became available, our model adapted to changing temporal conditions and provided further reduced forecast errors. We expect our model pipeline to act as a platform for developing early warning systems that can notify clinicians and pet owners about heightened risks of environmentally driven veterinary conditions.

Laboratory evaluations of the 3-month efficacy of oral lotilaner (Credelio™) against experimental infestations of dogs with the Australian paralysis tick, Ixodes holocyclus.

BACKGROUND: From three days following host attachment, the Australian paralysis tick, Ixodes holocyclus, secretes a neurotoxin that annually causes paralysis in approximately 10,000 domestic pets. Lotilaner, a novel isoxazoline formulated in a chewable flavoured tablet (CredelioTM), produces rapid onset of acaricidal activity in dogs, with an efficacy duration of at least one month. Two studies were performed to determine the efficacy of lotilaner against I. holocyclus infestations over 3 months. METHODS: Both studies included 16 dogs, ranked according to I. holocyclus counts on Day -5 (from infestations on Day -8) and blocked into pairs. One dog in each pair was randomized to be a sham-treated control, the other to receive lotilaner at a minimum dose rate of 20 mg/kg on Day 0. Dogs were dosed in a fed state. Infestations were performed in both studies on Days -8 (to determine the tick carrying capacity of each dog) -1, 28, 56, 70, 77 and 84, and additionally in Study 1 on Day 91, in Study 2 on Days 14 and 42. In Study 1, ticks were counted and assessed as alive or dead at 24, 48 and 72 h post-initial infestation and post-subsequent re-infestations. In study 2, ticks were counted at 24, 48 and 72 h post-dosing or post-re-infestation. Efficacy was determined by the percent reduction in live attached tick counts in the lotilaner group compared to control. RESULTS: Within 48 h post-treatment in Study 1 and within 72 h post-treatment in Study 2 all lotilaner-group dogs were free of live ticks. By 72 h post-infestation, efficacy in Study 1 remained at 100% through Day 87, except on Day 31 when a single tick was found on one dog, and through Day 59 in Study 2. Efficacy exceeded 95% through the final assessment in each study (Days 94 and 87 in Studies 1 and 2, respectively). CONCLUSION: These results demonstrate that lotilaner quickly kills existing I. holocyclus infestations. By providing 95.3-100.0% protection through at least 87 days post-treatment, lotilaner can be a valuable tool in reducing the risk of tick paralysis in dogs.

Are recreational areas a risk factor for tick paralysis in urban environments?

In Australia, tick paralysis in dogs (caused by a toxin in the saliva of Ixodes species during feeding) is a serious, distressing condition, and untreated it is often fatal. The aim of this study was to quantify the association between parkland (recreational or natural) in an urban area and the occurrence of canine tick paralysis. Brisbane, as a large urban centre located within the zone of paralysis tick habitat along the east coast of Australia, was selected as the study area. Postcodes selected for inclusion were those defined as being of an urban character (Australian Bureau of Statistics). The number of natural and recreational parkland polygons and total land area per postcode were derived. Tick paralysis case data for the selected postcodes were extracted from a national companion animal disease surveillance database. Between October 2010 and January 2017, 1650 cases of tick paralysis in dogs were reported and included in this study. Significant correlations were found between the number of reported cases per postcode and parklands: natural counts, 0.584 (P < 0.0001); natural area, 0.293 (P = 0.0075); recreational counts, 0.297 (P = 0.0151); and recreational area, 0.241 (P = 0.0286). Four disease clusters were also detected within the study area. All of these were located on the edges of the study area - either coastal or on the urban fringe; no clusters were identified within the core urban zone of the study area. Of the disease cases included in this study, strong seasonality was evidence: 68% of all cases were identified in spring. Within urban environments, areas of natural vegetation in particular appear to pose a risk for tick paralysis in dogs. This evidence can be used by veterinarians and dog owners to reduce the impact of tick paralysis by raising awareness of risk areas so as to enhance prevention via chemoprophylaxis and targeted searches of pet dogs for attached ticks.

An Exotic Hitchhiker: A Case Report of Importation into Connecticut from Africa of the Human Parasitizing Tick, Hyalomma truncatum (Acari: Ixodidae).

We report the importation into Connecticut, U.S.A., of an exotic tick, Hyalomma truncatum (Koch) (Acari: Ixodidae), on a human with recent travel history to Africa. The tick was identified using key morphological characters and through DNA sequencing. This case report highlights continuing risk associated with the importation of exotic tick vectors of medical and veterinary significance on international travelers returning to the United States from abroad.

Transcriptome and toxin family analysis of the paralysis tick, Ixodes holocyclus.

The Australian paralysis tick (Ixodes holocyclus) secretes neuropathic toxins into saliva that induce host paralysis. Salivary glands and viscera were dissected from fully engorged female I. holocyclus ticks collected from dogs and cats with paralysis symptoms. cDNA from both tissue samples were sequenced using Illumina HiSeq 100 bp pair end read technologies. Unique and non-redundant holocyclotoxin sequences were designated as HT2-HT19, as none were identical to the previously described HT1. Specific binding to rat synaptosomes was determined for synthetic HTs, and their neurotoxic capacity was determined by neonatal mouse assay. They induced a powerful paralysis in neonatal mice, particularly HT4 which produced rapid and strong respiratory distress in all animals tested. This is the first known genomic database developed for the Australian paralysis tick. The database contributed to the identification and subsequent characterization of the holocyclotoxin family that will inform the development of novel anti-paralysis control methods.

Delineation of an endemic tick paralysis zone in southeastern Australia.

Tick paralysis has a major impact on pet dog and cat populations in southeastern Australia. It results from envenomation by Ixodes holocyclus and Ixodes cornuatus ticks, the role of Ixodes cornuatus in the epidemiology of this disease in Australia being unclear. The aim of this study was to describe the geographical distribution of tick paralysis cases in southeastern Australia using data from a national disease surveillance system and to compare characteristics of "endemic" cases with those reported outside this endemic zone ("sporadic" cases). Data were collated and a proportional symbol map of all cases by postcode was created. A 15-case isopleth was developed based on descriptive spatial statistics (directional ellipses) and then kernel smoothing to distinguish endemic from sporadic cases. During the study period (January 2010-December 2015) 12,421 cases were reported, and 10,839 of these reported by clinics located in 434 postcodes were included in the study. Endemic cases were predominantly reported from postcodes in coastal southeastern Australia, from southern Queensland to eastern Victoria. Of those cases meeting selection criteria, within the endemic zone 10,767 cases were reported from 351 (88%) postcodes and outside this zone 72 cases were reported from 48 (12%) postcodes. Of these latter 48 postcodes, 18 were in Victoria (26 cases), 16 in New South Wales (28 cases), 7 in Tasmania (9 cases), 5 in South Australia (7 cases) and 2 in Queensland (2 cases). Seasonal distribution in reporting was found: 62% of endemic and 52% of sporadic cases were reported in spring. The number of both endemic and sporadic cases reported peaked in October and November, but importantly a secondary peak in reporting of sporadic cases in April was found. In non-endemic areas, summer was the lowest risk season whilst in endemic areas, autumn was the lowest risk season. Two clusters of sporadic cases were identified, one in South Australia (P=0.022) during the period 22 May to 2 June 2012 and another in New South Wales (P=0.059) during the period 9 October to 29 November 2012. Endemic and sporadic cases did not differ with respect to neuter status (P=0.188), sex (P=0.205), case outcome (P=0.367) or method of diagnosis (P=0.413). However, sporadic cases were 4.2-times more likely to be dogs than cats (P<0.001). The endemic tick paralysis zone described is consistent with previous anecdotal reports. Sporadic cases reported outside this zone might be due to a history of pet travel to endemic areas, small foci of I. holocyclus outside of the endemic zone, or in the case of southern areas, tick paralysis caused by I. cornuatus.

The first record of infestation by a native tick (Acari: Ixodidae) on the Australian emu (Dromaius novaehollandiae) and a review of tick paralysis in Australian birds.

For the first time, infestation of the Australian emu by a native tick is recorded based on an engorged adult female specimen of the southern paralysis tick (Ixodes cornuatus) taken from a captive emu at Healesville sanctuary, Victoria, Australia. Tick paralysis in Australian birds is discussed.

Ticks threatening lineage of Anatolian wild sheep (Ovis gmelinii anatolica) and determination of their tick-borne pathogens.

We aimed to determine the ticks of the Anatolian wild sheep and to define their tick-borne pathogens while molecularly studying their relationships with those of the domestic sheep. Furthermore, another aim of this study is to investigate tick paralysis resulting in the death of the Anatolian wild sheep. Ticks and blood samples were collected from the wild sheep whilst tick samples were also collected from hares, guinea fowls, chickens, and a turkey living in the Anatolian wild sheep breeding area. While PCR amplification was carried out for the detection of Babesia spp., Theileria spp. and Anaplasma spp. in blood samples, CCHF virus was screened in the tick samples in addition to the above-mentioned pathogens. Theileria spp. was detected in blood samples of 45 wild sheep. A total of 3494 ticks were collected from 52 Anatolian wild sheep, 5 hares, 5 guinea fowls, 2 chickens, and 1 turkey whereas 98 ticks were collected from the ground. B. ovis and T. ovis were detected in tick pools (Rh. bursa and H. excavatum) that were collected from the wild sheep. The paralysis was diagnosed in both of the hind legs of the newborn lambs infested with a great number of ticks. We also report that the tick species (H. excavatum and Rh. bursa) are determined to cause tick paralysis and tick toxicosis, which are associated with mortality especially in lambs. T. ovis and B. ovis were detected and studied for the first time in Anatolian wild sheep and in their ticks. The results of phylogenetic analyses showed that T. ovis and B. ovis isolates are genetically very close to the isolates that were previously obtained from the domestic small ruminants. We show that the Anatolian wild sheep can play the role of a reservoir for T. ovis. The presence of the CCHF virus has also been clearly shown and it has been observed that this virus, which is very pathogenic for humans, is anywise circulating in the region.

Use of big data in the surveillance of veterinary diseases: early detection of tick paralysis in companion animals.

BACKGROUND: Tick paralysis, resultant from envenomation by the scrub-tick Ixodes holocyclus, is a serious threat for small companion animals in the eastern coast of Australia. We hypothesise that surveillance systems that are built on Internet search queries may provide a more timely indication of high-risk periods more effectively than current approaches. METHODS: Monthly tick paralysis notifications in dogs and cats across Australia and the states of Queensland (QLD) and New South Wales (NSW) were retrieved from Disease WatchDog surveillance system for the period 2011-2013. Internet search terms related to tick paralysis in small companion animals were identified using Google Correlate, and corresponding search frequency metrics were downloaded from Google Trends. Spearman's rank correlations and time series cross correlations were performed to assess which Google search terms lead or are synchronous with tick paralysis notifications. RESULTS: Metrics data were available for 24 relevant search terms at national level, 16 for QLD and 18 for NSW, and they were all significantly correlated with tick paralysis notifications (P < 0.05). Among those terms, 70.8, 56.3 and 50 % showed strong Spearman's correlations, at national level, for QLD, and for NSW respectively, and cross correlation analyses identified searches which lead notifications at national or state levels. CONCLUSION: This study demonstrates that Internet search metrics can be used to monitor the occurrence of tick paralysis in companion animals, which would facilitate early detection of high-risk periods for tick paralysis cases. This study constitutes the first application of the rapidly emerging field of Internet-based surveillance to veterinary science.

Can Subclinical Infestation by Paralyzing Dermacentor andersoni (Acari: Ixodidae) Induce Immunity to Tick Paralysis in Sheep?

Cattle and sheep can develop immunity to paralysis caused by Dermacentor andersoni Stiles; however, this has been reported only in animals that were initially challenged with a high dose of ticks and exhibited clear symptoms of paralysis. Paralysis in sheep occurs in a dose-dependent fashion, with no paralysis occurring in sheep exposed to <0.2 ticks per kilogram sheep weight, and 100% paralysis in sheep exposed to >0.8 ticks per kilogram. This experiment was conducted to determine if sheep exposed to a low dose of ticks would also develop immunity to paralysis. Sheep were exposed to either a low (0.2 ticks per kilogram) or high dose of ticks (0.8 ticks per kilogram), then re-exposed to a second challenge of a paralyzing dose of ticks. All naïve sheep (eight of the eight) were paralyzed, while paralysis occurred in only four of the eight sheep previously exposed to a low dose, and one of the eight sheep previously exposed to a high dose. Results indicate that immunity can develop when sheep are exposed to a subclinical dose of paralyzing ticks, but in a smaller percentage of animals than those exposed to a high dose of ticks. Vaccine development perhaps remains the best option for nonacaricidal control of tick paralysis.

Tick-Induced Facial Palsy.

Ticks are obligate blood-sucking arthropods that exist worldwide. Their targets include all vertebrates and humans. Ticks are harmful to people with regard to transmission in many viral, bacterial, and parasitic infections. In addition to these diseases and toxin-induced neurological complications, tick-induced paralysis is a syndrome related to neurotoxin production, and its mortality ratio in the literature is reported to be approximately 10%. Tick-induced isolated facial paralysis is a rare form of the disease developing because of attachment to the external auditory canal or attachment behind the ear. Our country and region are under risk in terms of included tick habitat for tick-induced paralysis that is responsible particularly for hard ticks. In our article, we aimed to present a case with isolated facial paralysis that occurred after the internal auditory canal was bitten by Hyalomma margintum species belonging to the hard ticks group and to probe the management of this disease.

Tick paralysis in spectacled flying-foxes (Pteropus conspicillatus) in North Queensland, Australia: impact of a ground-dwelling ectoparasite finding an arboreal host.

When a parasite finds a new wildlife host, impacts can be significant. In the late 1980s populations of Spectacled Flying-foxes (SFF) (Pteropus conspicillatus), a species confined, in Australia, to north Queensland became infected by paralysis tick (Ixodes holocyclus), resulting in mortality. This Pteropus-tick relationship was new to Australia. Curiously, the relationship was confined to several camps on the Atherton Tableland, north Queensland. It was hypothesised that an introduced plant, wild tobacco (Solanum mauritianum), had facilitated this new host-tick interaction. This study quantifies the impact of tick paralysis on SFF and investigates the relationship with climate. Retrospective analysis was carried out on records from the Tolga Bat Hospital for 1998-2010. Juvenile mortality rates were correlated to climate data using vector auto-regression. Mortality rates due to tick paralysis ranged between 11.6 per 10,000 bats in 2003 and 102.5 in 2009; more female than male adult bats were affected. Juvenile mortality rates were negatively correlated with the total rainfall in January to March and July to September of the same year while a positive correlation of these quarterly total rainfalls existed with the total population. All tick affected camps of SFF were located in the 80% core range of S. mauritianum. This initial analysis justifies further exploration of how an exotic plant might alter the relationship between a formerly ground-dwelling parasite and an arboreal host.

Histopathological changes in the lungs from dogs with tick paralysis: 25 cases (2010-2012).

OBJECTIVE: To determine the prevalence and nature of histological lung lesions in dogs with tick paralysis. METHODS: A prospective study of 25 client-owned dogs that died during treatment for tick paralysis or were euthanased because of either the severity of the disease process or financial constraints was conducted at a veterinary emergency hospital in Queensland, Australia. Lung specimens were collected postmortem for histopathological examination. RESULTS: All 25 dogs had significant pulmonary changes: 9 exhibited congestion and alveolar oedema, with no obvious inflammatory cell infiltrate; 1 exhibited a mild increase in the number of alveolar macrophages in addition to congestion and alveolar oedema; the remaining 15 dogs had moderate or severe bronchopneumonia, with 2 showing evidence of aspiration pneumonia. CONCLUSION: Dogs with clinically severe tick paralysis are likely to have pulmonary parenchymal disease. Bronchopneumonia may be present in a significant proportion of cases and may reflect aspiration.

Indications, durations and outcomes of mechanical ventilation in dogs and cats with tick paralysis caused by Ixodes holocyclus: 61 cases (2008-2011).

OBJECTIVES: The primary objectives of this research were to describe the indications for mechanical ventilation, the duration of mechanical ventilation and probability of survival in dogs and cats with respiratory failure induced by the Australian paralysis tick (Ixodes holocyclus). METHODS: A retrospective case series and a retrospective single cohort study were conducted using dogs and cats with tick paralysis requiring mechanical ventilation. An index of oxygenating performance of the lung (PF ratio of partial pressure of oxygen in arterial blood to fraction of inspired oxygen) was derived from arterial blood gas analysis; patients euthanased because of veterinary costs were identified and Kaplan-Meier survival analyses performed. RESULTS: In total, 36.6% of patients were ventilated because of hypoxaemia refractory to oxygen therapy, 38.3% because of hypoventilation, 18.3% because of unsustainable respiratory effort and 6.6% because of respiratory arrest. Median duration of mechanical ventilation was 23 h, median time hospitalised was 84 h and 63.9% of all patients requiring mechanical ventilation survived to discharge from the hospital. Survival probability increased to 75% when cases of cost-based euthanasia were right-censored rather than treated as deaths. The survival probability of patients ventilated because of hypoxaemia (52.6%) was significantly less than for those ventilated because of hypoventilation (90.5%). The first measured PF ratio after commencing mechanical ventilation was not significantly associated with survival probability. CONCLUSIONS: Dogs and cats with tick paralysis requiring mechanical ventilation to manage respiratory failure have reasonable survival probability. Dogs and cats requiring mechanical ventilation because of hypoventilation have a higher survival probability than those with oxygenation failure.

Apparent tick paralysis by Rhipicephalus sanguineus (Acari: Ixodidae) in dogs.

Certain tick species including Ixodes holocyclus can inoculate neurotoxins that induce a rapid, ascending flaccid paralysis in animals. Rhipicephalus sanguineus, the most widespread tick of dogs, is recognized as a vector of several pathogens causing diseases in dogs and humans. A single report suggests its role as cause of paralysis in dogs. This study presents the clinical history of 14 young dogs heavily infested by R. sanguineus (intensity of infestation, 63-328) in an endemic area of southern Italy. During May to June of 2011, dogs were presented at the clinical examination with neurological signs of different degrees (e.g., hind limb ataxia, generalized lethargy, and difficulty in movements). All animals were treated with acaricides and by manual tick removal but ten of them died within a day, displaying neurological signs. The other 4 dogs recovered within 3 days with acaricidal and supportive treatment. Twelve dogs were positive by blood smear examination for Hepatozoon canis with a high parasitemia, two also for Babesia vogeli and two were negative for hemoparasites. Low-grade thrombocytopenia, hypoalbuminemia, and pancytopenia were the haematological alterations most frequently recorded. Other causes of neurological disease in dogs were excluded and the diagnosis of tick paralysis by R. sanguineus was confirmed (ex juvantibus) by early and complete recovery of 4 dogs following acaricidal treatment and tick removal.

Differential feeding success of two paralysis-inducing ticks, Rhipicephalus warburtoni and Ixodes rubicundus on sympatric small mammal species, Elephantulus myurus and Micaelamys namaquensis.

Rodents are recognised as important hosts of ixodid ticks and as reservoirs of tick-borne pathogens across the world. Sympatric insectivores are usually inconspicuous and often overlooked as hosts of ticks and reservoirs of disease. Elephant shrews or sengis of the order Macroscelidea are small insectivores that often occur in sympatry with rodents in southern Africa. Sengis are invariably parasitised by large numbers of immature ticks while sympatric rodents are infested with very few. The reason for the difference in tick parasitism rates between these hosts is unknown. While a number of mechanisms are possible, we hypothesised that certain tick species exhibit "true host specificity" and as such would only attach and feed successfully on their preferred host or a very closely related host species. To investigate this, we conducted feeding experiments using two economically important tick species, the brown paralysis tick, Rhipicephalus warburtoni and the Karoo paralysis tick, Ixodes rubicundus and two sympatric small mammal species as potential hosts, the eastern rock sengi, Elephantulus myurus and the Namaqua rock mouse, Micaelamys namaquensis. Ticks attached and fed readily on E. myurus, but did not attach or feed successfully on M. namaquensis suggesting that these ticks exhibit true host specificity. We suggest that a kairomonal cue originating from the odour of E. myurus may stimulate the attachment and feeding of these ticks and that they further possess immunosuppressive mechanisms specific to E. myurus, allowing them to feed on this host species but not on M. namaquensis. This study highlights the importance of small mammalian insectivores as potential hosts of ixodid tick species and hence their potential as reservoirs of tick-borne pathogens.

Facial nerve paralysis due to intra-aural Hyalomma tick infestation.

We present the case of a 33 year-old man from a village of the north-eastern part of central Anatolia admitted to the otolaryngology department of Yeditepe University Hospital with right facial asymmetry and pain on the right ear. A tick of the genus Hyalomma was observed in the external auditory canal of the right ear and it was removed with fine cup forceps under otomicroscopy. We are of the opinion that in patients presenting with sudden acute ear pain and facial palsy, the ear canal should be examined to exclude an infestation by ticks.

Tick paralysis caused by Dermacentor andersoni (Acari: Ixodidae) is a heritable trait.

The heritability of the ability to cause paralysis was examined in crosses of virulent and avirulent Dermacentor andersoni (Stiles) (Acari: Ixodidae). Virulence was assessed using hamster bioassay. Paralysis was caused by the virulent parental strain but not by the avirulent parental strain. Four crosses were made: Avirulent female x Avirulent male (AA cross), Virulent female x Virulent male (VV cross), Avirulent female x Virulent male (AV cross), and Virulent female x Avirulent male (VA cross). The proportion of females that produced fertile egg masses was similar among the crosses; however, VV females produced fewer fertile eggs. This was attributed to the long-term laboratory colonization of the virulent strain. All crosses had similar levels of larval and nymphal engorgement and adult eclosion. The ability to cause paralysis was detected in progeny of all crosses except the AA cross. Both heterogeneous crosses caused paralysis, but the virulence was slightly less than for the VV cross. Virulence was similar among the AV and VA crosses, indicating that virulent males were as likely as females to pass the trait to progeny. Time to paralysis was faster for the VV cross compared with the heterogeneous crosses.